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Prokaryote Cells Prokaryote Cells
ConclusionsConclusions
Bacterial RibosomeBacterial Ribosome
Small Sub Unit 30S 16S RNA 21 proteins
Small Sub Unit 30S 16S RNA 21 proteins
Large Subunit 50S 23S & 5S RNAs 31 proteins
Large Subunit 50S 23S & 5S RNAs 31 proteins
RibosomesRibosomes Complex structures
consisting of protein and RNA
Sites of protein synthesis
Smaller than eucaryotic ribosomes
procaryotic ribosomes Þ 70S
eucaryotic ribosomes Þ 80S
S = Svedburg unit
Complex structures consisting of protein and RNA
Sites of protein synthesis
Smaller than eucaryotic ribosomes
procaryotic ribosomes Þ 70S
eucaryotic ribosomes Þ 80S
S = Svedburg unit
Ribosomal ComplexityRibosomal Complexity
Three Dimensional image of the 30s ribosomal subunit
Vital in protein synthesis
Binds to the messenger RNA to initiate translation
Three Dimensional image of the 30s ribosomal subunit
Vital in protein synthesis
Binds to the messenger RNA to initiate translation
50s Ribosomal subunit50s Ribosomal subunit
The large subunit (50S) from Deinococcus radiodurans contains 33 different proteins
Two rRNA chains (23S and 5S rRNA). The ribosomal rRNA
Responsible for binding t RNA and the catalysis of peptide bonds for translation
The large subunit (50S) from Deinococcus radiodurans contains 33 different proteins
Two rRNA chains (23S and 5S rRNA). The ribosomal rRNA
Responsible for binding t RNA and the catalysis of peptide bonds for translation
16 s Ribosomal subunit from E. coliCulpepper Group at the Stanford School of Medicine
16 s Ribosomal subunit from E. coliCulpepper Group at the Stanford School of Medicine
InclusionsInclusions
These are storage bodies in the cytoplasm of bacteria
The inclusions vary with the type of bacteria
Provide a supply of vital compounds or ions for metabolism
Reduce osmotic pressure by tying up molecules in particulate form
These are storage bodies in the cytoplasm of bacteria
The inclusions vary with the type of bacteria
Provide a supply of vital compounds or ions for metabolism
Reduce osmotic pressure by tying up molecules in particulate form
Inclusions in CyanobacteriaInclusions in
Cyanobacteria Cyanophycin
granules are found in Cyanobacteria. They are large inclusion bodies composed of polypeptides comprised of arginine and aspartic acid. These store additional nitrogen for the bacteria.
Cyanophycin granules are found in Cyanobacteria. They are large inclusion bodies composed of polypeptides comprised of arginine and aspartic acid. These store additional nitrogen for the bacteria.
Inclusion bodies Inclusion bodies
Cyanophycin granules are found in the filamentous photosynthetic bacteria found in fresh water ponds that are vital to the nitrogen cycle in aquatic environments
Cyanophycin granules are found in the filamentous photosynthetic bacteria found in fresh water ponds that are vital to the nitrogen cycle in aquatic environments
CarboxysomesCarboxysomes Cyanobacteria,
thiobacilli, and nitrifying bacteria, organisms that reduce CO2 in order to produce carbohydrates, possess carboxysomes containing an enzyme used for CO2 fixation.
These may be separated from the cytoplasm by internal membrane
Cyanobacteria, thiobacilli, and nitrifying bacteria, organisms that reduce CO2 in order to produce carbohydrates, possess carboxysomes containing an enzyme used for CO2 fixation.
These may be separated from the cytoplasm by internal membrane
PHBPHB Poly-
hydroxybutyrate molecules joined by
ester bonds between the carboxyl and hydroxyl of adjacent molecules.
These are common in purple sulfur bacteria and stain with Sudan black for light microscopy. These granules serve as storage reservoirs for glycogen and sugars necessary for energy and biosynthesis.
Poly- hydroxybutyrate
molecules joined by ester bonds between the carboxyl and hydroxyl of adjacent molecules.
These are common in purple sulfur bacteria and stain with Sudan black for light microscopy. These granules serve as storage reservoirs for glycogen and sugars necessary for energy and biosynthesis.
VolutinVolutin Some bacteria produce
inorganic inclusion bodies in their cytoplasm, including volutin granules that store phosphate and sulfur granules that store sulfur. Volutin is a source of phosphate for DNA. Sulfur is used by purple photosynthetic bacteria that use hydrogen sulfide as a photosynthetic electron donor.
Some bacteria produce inorganic inclusion bodies in their cytoplasm, including volutin granules that store phosphate and sulfur granules that store sulfur. Volutin is a source of phosphate for DNA. Sulfur is used by purple photosynthetic bacteria that use hydrogen sulfide as a photosynthetic electron donor.
Gas VacuolesGas Vacuoles• Purple and green
photosynthetic bacteria as well as some other aquatic bacteria contain gas vacuoles. These are aggregates of hollow protein cylinders called gas vesicles that are permeable to atmospheric gas, enabling the organism to regulate buoyancy. Bacteria are able to regulate the depth at which they float to regulate photosynthetic activity
• Purple and green photosynthetic bacteria as well as some other aquatic bacteria contain gas vacuoles. These are aggregates of hollow protein cylinders called gas vesicles that are permeable to atmospheric gas, enabling the organism to regulate buoyancy. Bacteria are able to regulate the depth at which they float to regulate photosynthetic activity
EnterosomesEnterosomes In Salmonella and E. coli have internal
structures similar to carboxysomes Enterosomes contain enzymes required for
the metabolism of certain molecules The existence of these molecules may be due
to the necessity of dealing with toxic molecules
Propanediol is a metabolite of fucose which is a sugar found on the intestinal wall of mammals that that can be degraded by intestinal bacteria – This is one of the molecules metabolized in enterosomes
In Salmonella and E. coli have internal structures similar to carboxysomes
Enterosomes contain enzymes required for the metabolism of certain molecules
The existence of these molecules may be due to the necessity of dealing with toxic molecules
Propanediol is a metabolite of fucose which is a sugar found on the intestinal wall of mammals that that can be degraded by intestinal bacteria – This is one of the molecules metabolized in enterosomes
MagnetosomesMagnetosomes
• Some motile aquatic bacteria are able to orient themselves by responding to the magnetic fields of the earth because they possess magnetosomes, membrane-bound crystals of magnetite or other iron-containing substances that function as tiny magnets.
• Some motile aquatic bacteria are able to orient themselves by responding to the magnetic fields of the earth because they possess magnetosomes, membrane-bound crystals of magnetite or other iron-containing substances that function as tiny magnets.
MagnetosomesMagnetosomes
Movement of bacteria in a magnetic field
Movement of bacteria in a magnetic field
External StructuresExternal Structures
Fimbriae Pili Flagella
Fimbriae Pili Flagella
Bacterial piliBacterial pili
http://biophysics.bumc.bu.edu/faculty/bullitt/images/cartoon_ppili_hib.jpg
http://biophysics.bumc.bu.edu/faculty/bullitt/images/cartoon_ppili_hib.jpg
PiliPili
• Pili are appendages that are larger than fimbriae. Their presence is determined by genes on plasmids called sex factors. These structures function in conjugation which is a genetic exchange occurring in bacteria with these appendages
• Pili are appendages that are larger than fimbriae. Their presence is determined by genes on plasmids called sex factors. These structures function in conjugation which is a genetic exchange occurring in bacteria with these appendages
Pilin( Salmonella)Pilin( Salmonella)
FimbriaeFimbriae
• Fimbriae are thin, hair-lie projections extending from the cell wall in Gram – bacteria. They are composed of helical protein units and designed for attachment to the host cell membranes
( mucous). • They also may contribute
to types of movement in some bacteria.
• These are considered to be virulence factors and induce many pathogenic effects
• Fimbriae are thin, hair-lie projections extending from the cell wall in Gram – bacteria. They are composed of helical protein units and designed for attachment to the host cell membranes
( mucous). • They also may contribute
to types of movement in some bacteria.
• These are considered to be virulence factors and induce many pathogenic effects
Neisseria gonorrhea
Fimbriae and AdhesinsFimbriae and Adhesins
The tips of these structures have tips with adhesive proteins called adhesins
They are designed to attach to a specific molecular target
Fimbriae are produced in the cytoplasm and transported to the exterior of the cell
The tips of these structures have tips with adhesive proteins called adhesins
They are designed to attach to a specific molecular target
Fimbriae are produced in the cytoplasm and transported to the exterior of the cell
AdhesinsAdhesins
Structural polymorphism of bacterial adhesion pili.
Bullitt E, and Makowski L.
Structural polymorphism of bacterial adhesion pili.
Bullitt E, and Makowski L.
Bacterial adhesion pili are designed to bind specifically and maintain attachment of bacteria to target cells. Uropathogenic P-pili are sufficiently mechanically resilient to resist the cleansing action of urine flow that removes most other bacteria. P-pili are 68 A in diameter and approximately 1 micron long, and are composed of approximately 1,000 copies of the principal structural protein, PapA. They are attached to the outer membrane by a minor structural protein, PapH and are terminated by an approximately 20 A diameter fibrillus composed of PapK, PapE and PapF, which presents the host-binding adhesin PapG. The amino-acid sequences of PapA, PapE, and PapF are similar, with highly conserved C-termini being responsible for binding to PapD, the periplasmic chaperone. Our three-dimensional reconstruction indicates that pili are formed by the tight winding of a much thinner structure. A structural transition allows the pilus to unravel without depolymerizing, producing a thin, extended structure five times the length of the original pilus.
Bacterial adhesion pili are designed to bind specifically and maintain attachment of bacteria to target cells. Uropathogenic P-pili are sufficiently mechanically resilient to resist the cleansing action of urine flow that removes most other bacteria. P-pili are 68 A in diameter and approximately 1 micron long, and are composed of approximately 1,000 copies of the principal structural protein, PapA. They are attached to the outer membrane by a minor structural protein, PapH and are terminated by an approximately 20 A diameter fibrillus composed of PapK, PapE and PapF, which presents the host-binding adhesin PapG. The amino-acid sequences of PapA, PapE, and PapF are similar, with highly conserved C-termini being responsible for binding to PapD, the periplasmic chaperone. Our three-dimensional reconstruction indicates that pili are formed by the tight winding of a much thinner structure. A structural transition allows the pilus to unravel without depolymerizing, producing a thin, extended structure five times the length of the original pilus.
Neisseria gonorrheaNeisseria gonorrhea
To cause infection, Neisseria gonorrhoeae (inf) must first colonize a mucosal surface composed of columnar epithelial cells. Pili alow for this initial binding and, in fact, N. gonorrhoeae is able to rapidly lose pili and synthesize new ones with a different adhesive tip, enabling the bacterium to adhere to a variety of tissues and cells including sperm, the epithelial cells of the mucous membranes lining the throat, genitourinary tract, rectum, and the conjunctiva of the eye. Subsequently, the bacterium is able to make more intimate contact with the host cell surface by way of a cell wall adhesin called Opa
To cause infection, Neisseria gonorrhoeae (inf) must first colonize a mucosal surface composed of columnar epithelial cells. Pili alow for this initial binding and, in fact, N. gonorrhoeae is able to rapidly lose pili and synthesize new ones with a different adhesive tip, enabling the bacterium to adhere to a variety of tissues and cells including sperm, the epithelial cells of the mucous membranes lining the throat, genitourinary tract, rectum, and the conjunctiva of the eye. Subsequently, the bacterium is able to make more intimate contact with the host cell surface by way of a cell wall adhesin called Opa
Neisseria – Gram-intracellular diplococci
Neisseria – Gram-intracellular diplococci
E. Coli and adhesionE. Coli and adhesion
http://medschool.umaryland.edu/infeMSD/Images.htm
http://medschool.umaryland.edu/infeMSD/som.html
( Donnenberg lab at University of Maryland)
http://medschool.umaryland.edu/infeMSD/Images.htm
http://medschool.umaryland.edu/infeMSD/som.html
( Donnenberg lab at University of Maryland)
Flagella MotilityFlagella Motility
http://www-micro.msb.le.ac.uk/video/motility.html
Arrangement of flagellaArrangement of flagella
monotrichous – one flagellum polar flagellum – flagellum at end of cell amphitrichous – one flagellum at each
end of cell lophotrichous – cluster of flagella at one
or both ends peritrichous – spread over entire surface
of cell
monotrichous – one flagellum polar flagellum – flagellum at end of cell amphitrichous – one flagellum at each
end of cell lophotrichous – cluster of flagella at one
or both ends peritrichous – spread over entire surface
of cell
Arrangement of FlagellaArrangement of Flagella
The filamentThe filament
Hollow, rigid cylinder Composed of the protein flagellin Some procaryotes have a sheath
around filament
Hollow, rigid cylinder Composed of the protein flagellin Some procaryotes have a sheath
around filament
Flagellin( Protein structure)
Flagellin( Protein structure)
http://www.rcsb.org/pdb/home/home.do
Search with flagellin Choose 1ucu Click on choice Choose the different
image files to learn about molecular structure
http://www.rcsb.org/pdb/home/home.do
Search with flagellin Choose 1ucu Click on choice Choose the different
image files to learn about molecular structure
References on Genes and Proteins
References on Genes and Proteins
http://www.ncbi.nlm.nih.gov/ Choose structures – proteins Choose nucleotide – genes – DNA
sequence Choose protein – AA sequence Cn3D – free download to study
protein structure
http://www.ncbi.nlm.nih.gov/ Choose structures – proteins Choose nucleotide – genes – DNA
sequence Choose protein – AA sequence Cn3D – free download to study
protein structure
Tubulin subunits of eukaryote flagellumTubulin subunits of eukaryote flagellum
Tubulin dimer Tubulin dimer
Comparison of Prokaryote and Eukaryote Flagella
Comparison of Prokaryote and Eukaryote Flagella
The three parts of the flagellum
The three parts of the flagellum
3 parts filament basal body hook
3 parts filament basal body hook
Hook and Base StructureHook and Base Structure
http://molvis.sdsc.edu/atlas/morphs/flaghook/index.htm
http://www.umass.edu/microbio/chime/pe_beta/pe/atlas/atlas.htm
http://atlas.proteinexplorer.org
http://molvis.sdsc.edu/atlas/morphs/flaghook/index.htm
http://www.umass.edu/microbio/chime/pe_beta/pe/atlas/atlas.htm
http://atlas.proteinexplorer.org
The hook and basal bodyThe hook and basal body
Hooklinks filament to basal body
Basal bodyseries of rings that drive flagellar motor
Hooklinks filament to basal body
Basal bodyseries of rings that drive flagellar motor
Flagellar complexityFlagellar complexity
Structure of Bacterial Flagella
Structure of Bacterial Flagella
Flagellar SynthesisFlagellar Synthesis
An example of self-assembly Complex process involving many
genes and gene products New molecules of flagellin are
transported through the hollow filament
Growth is from tip, not base
An example of self-assembly Complex process involving many
genes and gene products New molecules of flagellin are
transported through the hollow filament
Growth is from tip, not base
Flagellar SynthesisFlagellar Synthesis
Flagellar MotionFlagellar Motion
flagellum rotates like a propeller in general, counterclockwise rotation
causes forward motion (run) in general, clockwise rotation disrupts
run causing a tumble (twiddle)
flagellum rotates like a propeller in general, counterclockwise rotation
causes forward motion (run) in general, clockwise rotation disrupts
run causing a tumble (twiddle)
Traveling toward and Attractant
Traveling toward and Attractant
Caused by lowering the frequency of tumbles
Traveling away involves similar but opposite responses
Caused by lowering the frequency of tumbles
Traveling away involves similar but opposite responses
Tumble and RunTumble and Run
Flagellar movementFlagellar movement
http://www-micro.msb.le.ac.uk/Video/motility.html
http://www-micro.msb.le.ac.uk/Video/motility.html
Motility and PathogenicityMotility and Pathogenicity
The mucosal surfaces of the bladder and the intestines constantly flush bacteria away in order to prevent colonization.
Motile bacteria that can swim chemotactically toward mucosal surfaces may have a better chance to make contact with the mucous membranes, attach, and colonize.
Many bacteria that can colonize the bladder and the intestines are motile. Motility probably helps these bacteria move through the mucous in places where it is less viscous. To support this, nonmotile mutants of Vibrio cholerae are less virulent than the motile wild types.
The mucosal surfaces of the bladder and the intestines constantly flush bacteria away in order to prevent colonization.
Motile bacteria that can swim chemotactically toward mucosal surfaces may have a better chance to make contact with the mucous membranes, attach, and colonize.
Many bacteria that can colonize the bladder and the intestines are motile. Motility probably helps these bacteria move through the mucous in places where it is less viscous. To support this, nonmotile mutants of Vibrio cholerae are less virulent than the motile wild types.
HelicobacterHelicobacter Helicobacter pylori ,by means of its flagella, is
able to swim through the mucus layer of the stomach and adhere to the epithelial cells of the mucous membranes.
Here the pH is near neutral. To also help protect the bacterium from the acid, H. pylori produces an acid-inhibitory protein that blocks acid secretion by surrounding parietal cells in the stomach.
The bacterium then releases toxins that lead to excessive production of cytokines and chemokines, as well as mucinase and phospholipase that damage the gastric mucosa.
Helicobacter pylori ,by means of its flagella, is able to swim through the mucus layer of the stomach and adhere to the epithelial cells of the mucous membranes.
Here the pH is near neutral. To also help protect the bacterium from the acid, H. pylori produces an acid-inhibitory protein that blocks acid secretion by surrounding parietal cells in the stomach.
The bacterium then releases toxins that lead to excessive production of cytokines and chemokines, as well as mucinase and phospholipase that damage the gastric mucosa.
ChemotaxisChemotaxis
Positive chemotaxis is exhibited by the outer ring which are responding to serine, the second ring responding to aspartate, and the upper dot – non chemotactic
The E. coli on the agar plate is responding to acetate. Acetate concentration varies from 0 to 2M at the top left
Helicobacter and the Gastric Mucosa
Helicobacter and the Gastric Mucosa
UlcersUlcers
Other Types of MotilityOther Types of Motility
Spirochetes axial filaments cause flexing and
spinning movement Gliding motility
cells coast along solid surfaces no visible motility structure has been
identified
Spirochetes axial filaments cause flexing and
spinning movement Gliding motility
cells coast along solid surfaces no visible motility structure has been
identified
Spirochetes and motilitySpirochetes and motility
Because of their thinness, their internal flagella (axial filaments), and their motility spirochetes are more readily able to penetrate host mucous membranes, skin abrasions, etc., and enter the body.
Motility and penetration may also enable the spirochetes to penetrate deeper in tissue and enter the lymphatics and bloodstream and disseminate to other body sites.
Because of their thinness, their internal flagella (axial filaments), and their motility spirochetes are more readily able to penetrate host mucous membranes, skin abrasions, etc., and enter the body.
Motility and penetration may also enable the spirochetes to penetrate deeper in tissue and enter the lymphatics and bloodstream and disseminate to other body sites.
ChemotaxisChemotaxis
Movement towards a chemical attractant or away from a chemical repellant
Concentrations of chemoattractants and chemorepellants detected by chemoreceptors on surfaces of cells
Movement towards a chemical attractant or away from a chemical repellant
Concentrations of chemoattractants and chemorepellants detected by chemoreceptors on surfaces of cells
Translocation and Secretion in Prokaryote
Cells
Translocation and Secretion in Prokaryote
Cells
Transport Across the Cell WallTransport Across the Cell Wall
Protein Export SystemsProtein Export Systems
Systems are present in Archaea, Bacteria, and Eukarya
Evolved independently but have many similarities
Eight systems move proteins across the cytoplasmic membrane and peptidoglycans cell wall
Another eight are involved in the transport of proteins across the outer membrane, LPS
Systems are present in Archaea, Bacteria, and Eukarya
Evolved independently but have many similarities
Eight systems move proteins across the cytoplasmic membrane and peptidoglycans cell wall
Another eight are involved in the transport of proteins across the outer membrane, LPS
Proteins for Movement out of the Cell
Proteins for Movement out of the Cell
Proteins may be folded, unfolded, or partially folded
Some are completely assembled
Proteins may be folded, unfolded, or partially folded
Some are completely assembled
TranslocationTranslocation
Movement of a molecule from one location to another
Protein export – Translocation out of the cytoplasm( compartment to compartment)
Protein secretion – Translocation of proteins through all membranes into the external environment( secretion to the external environment)
Movement of a molecule from one location to another
Protein export – Translocation out of the cytoplasm( compartment to compartment)
Protein secretion – Translocation of proteins through all membranes into the external environment( secretion to the external environment)
Membrane Systems in E. coli and Gram NegativeMembrane Systems in E. coli and Gram Negative
Protein Secretion in Procaryotes numerous protein secretion
pathways have been identified four major pathways are:
Sec-Dependent pathway Type II pathway Type I (ABC) protein secretion pathway Type III protein secretion pathway
Protein Secretion in Procaryotes numerous protein secretion
pathways have been identified four major pathways are:
Sec-Dependent pathway Type II pathway Type I (ABC) protein secretion pathway Type III protein secretion pathway
Recognition and The Sec system for the transport of
proteins
Recognition and The Sec system for the transport of
proteins Recognition by the Sec system occurs
during protein synthesis While the peptide is being synthesized a
portion of the molecule serves as a signal sequence which is essential for recognition
This 15-30 amino acid sequence is key to the attachment to the SecA system
Recognition by the Sec system occurs during protein synthesis
While the peptide is being synthesized a portion of the molecule serves as a signal sequence which is essential for recognition
This 15-30 amino acid sequence is key to the attachment to the SecA system
Protein Secretion – Sec Dependent
Protein Secretion – Sec Dependent
Sec A leads the attached newly synthesized membrane protein to the membrane spanning channel composed of three other Sec protein ( YEG)
The channel has a hydrophilic inner surface so proteins can enter and pass through
In transit another protein, SecB attaches to the protein. This is a chaperone that keeps the protein in its extended or unfolded form
Sec A leads the attached newly synthesized membrane protein to the membrane spanning channel composed of three other Sec protein ( YEG)
The channel has a hydrophilic inner surface so proteins can enter and pass through
In transit another protein, SecB attaches to the protein. This is a chaperone that keeps the protein in its extended or unfolded form
In transit modificationIn transit modification
In transit another molecule a signal peptidase clips off the signal sequence
As the protein is passed through the Sec YEG channel
An expenditure of energy is required – Both ATP and a proton motive force is required
In transit another molecule a signal peptidase clips off the signal sequence
As the protein is passed through the Sec YEG channel
An expenditure of energy is required – Both ATP and a proton motive force is required
Gram - and Gram +Gram - and Gram +
Gram positive bacteria secrete directly into the environment
Gram negative bacteria use the Sec system to transport across the cell wall( peptidoglycan cell wall into the periplasm) and a different system to move across the LPS
These systems can be quite complex involving as many as 14 proteins
Gram positive bacteria secrete directly into the environment
Gram negative bacteria use the Sec system to transport across the cell wall( peptidoglycan cell wall into the periplasm) and a different system to move across the LPS
These systems can be quite complex involving as many as 14 proteins
Structure of the Sec Dependent PathwayStructure of the Sec Dependent Pathway
Sec Dependent Pathway
Sec Dependent Pathway
PathwayPathway
Type II( research article)Type II( research article)
Mol Microbiol. 2002 Jan;43(2):475-85.Related Articles, Links
A novel type II secretion system in Pseudomonas aeruginosa.
Ball G, Durand E, Lazdunski A, Filloux A.
Laboratoire d'Ingenierie des Systemes Macromoleculaires, UPR9027, IBSM/CNRS, Marseille, France.
Mol Microbiol. 2002 Jan;43(2):475-85.Related Articles, Links
A novel type II secretion system in Pseudomonas aeruginosa.
Ball G, Durand E, Lazdunski A, Filloux A.
Laboratoire d'Ingenierie des Systemes Macromoleculaires, UPR9027, IBSM/CNRS, Marseille, France.
Type IIType II
Transports proteins from periplasmic space across outer membrane
Present in Pseudomonas aeruginosa and Vibrio cholera
Observed in some gram-negative bacteria, including some pathogens
Complex systems consisting of up to 12-14 proteins most are integral membrane proteins
Transports proteins from periplasmic space across outer membrane
Present in Pseudomonas aeruginosa and Vibrio cholera
Observed in some gram-negative bacteria, including some pathogens
Complex systems consisting of up to 12-14 proteins most are integral membrane proteins
Type II secretory proteinsType II secretory proteins
Toxins( cholera toxin) Pili protein Pectinases Lipases Proteases Other enzymes to degrade
molecules in the environment
Toxins( cholera toxin) Pili protein Pectinases Lipases Proteases Other enzymes to degrade
molecules in the environment
TYPE 2TYPE 2
ABC Transporters – Type IABC Transporters – Type I Also called ABC protein secretion pathway. 65
families of transporters Currently two families export large proteins
and four transport peptides and small proteins General structure is two integral channel
forming domains and two cytoplasmic domains that involve the hydrolysis of ATP
The proteins in this system associate with two auxillary systems the MFPs, membrane fusion proteins and the OMFs, outer membrane factors
MFP’s are present in Gram Positive and Gram Negative Bacteria
Also called ABC protein secretion pathway. 65 families of transporters
Currently two families export large proteins and four transport peptides and small proteins
General structure is two integral channel forming domains and two cytoplasmic domains that involve the hydrolysis of ATP
The proteins in this system associate with two auxillary systems the MFPs, membrane fusion proteins and the OMFs, outer membrane factors
MFP’s are present in Gram Positive and Gram Negative Bacteria
ABC TransportersABC Transporters
Type I The ABC (ATP binding
cassette) transporter is one of the active transport systems of the cell, which is widespread in archaea, eubacteria, and eukaryotes (Higgins 1992). It is also known as the periplasmic binding protein-dependent transport system in Gram-negative bacteria and the binding-lipoprotein-dependent transport system in Gram-positive bacteria. The transporter shows a common global organization
Type I The ABC (ATP binding
cassette) transporter is one of the active transport systems of the cell, which is widespread in archaea, eubacteria, and eukaryotes (Higgins 1992). It is also known as the periplasmic binding protein-dependent transport system in Gram-negative bacteria and the binding-lipoprotein-dependent transport system in Gram-positive bacteria. The transporter shows a common global organization
General structureGeneral structure
Typically, it consists of two integral membrane proteins (permeases) each having six transmembrane segments, two peripheral membrane proteins that bind and hydrolyze ATP, and a periplasmic (or lipoprotein) substrate-binding protein.
Typically, it consists of two integral membrane proteins (permeases) each having six transmembrane segments, two peripheral membrane proteins that bind and hydrolyze ATP, and a periplasmic (or lipoprotein) substrate-binding protein.
ATP and ABC TransporterATP and ABC Transporter The ATP-binding
protein component is the most conserved, the membrane protein component is somewhat less conserved, and the substrate-binding protein component is most divergent (Tam and Saier 1993; Saurin and Dassa 1994) in terms of the sequence similarity.
The ATP-binding protein component is the most conserved, the membrane protein component is somewhat less conserved, and the substrate-binding protein component is most divergent (Tam and Saier 1993; Saurin and Dassa 1994) in terms of the sequence similarity.
MechanismMechanism The ABC transporters
form the largest group of paralogous genes in bacterial and archaeal genomes (Tatusov et al. 1996), and the genes for the three components frequently form an operon (Higgins 1992).
The ABC transporters form the largest group of paralogous genes in bacterial and archaeal genomes (Tatusov et al. 1996), and the genes for the three components frequently form an operon (Higgins 1992).
Importers and exporters represent the ABC transporters. ABC transporters include nucleotide binding domains (NBD1 and NBD2), transmembrane spanning domains (MSD1 and MSD2) and solute binding proteins (SBP1 and SBP2). In the case of exporters, the SBP domains are absent. Also inherent to the ABC transporters is the conserved organizational nature of the genes involved.
Importers and exporters represent the ABC transporters. ABC transporters include nucleotide binding domains (NBD1 and NBD2), transmembrane spanning domains (MSD1 and MSD2) and solute binding proteins (SBP1 and SBP2). In the case of exporters, the SBP domains are absent. Also inherent to the ABC transporters is the conserved organizational nature of the genes involved.
•Sequences the same in black
•Amino Acid Alignment data for different bacteria on the ABC Transporter
•Differences in red( # in the polypeptide or protein molecule)
ABC TransportersABC Transporters
Animation for ABC transportershttp://www.cat.cc.md.us/courses/bio141/
lecguide/unit1/prostruct/active.html PMF- Proton motive forcehttp://www.cat.cc.md.us/courses/bio141/
lecguide/unit1/prostruct/pmf/pmf.html
Animation for ABC transportershttp://www.cat.cc.md.us/courses/bio141/
lecguide/unit1/prostruct/active.html PMF- Proton motive forcehttp://www.cat.cc.md.us/courses/bio141/
lecguide/unit1/prostruct/pmf/pmf.html
Type III and SecretionType III and Secretion
Secretes virulence factors of gram-negative bacteria from cytoplasm, across both plasma membrane and outer membrane, and into host cell
Some type III secretion machinery is needle-shaped secreted proteins thought to move through
a translocation channel
Secretes virulence factors of gram-negative bacteria from cytoplasm, across both plasma membrane and outer membrane, and into host cell
Some type III secretion machinery is needle-shaped secreted proteins thought to move through
a translocation channel
OccurrenceOccurrence
Found in Salmonella, Pseudomonas, Yersinia, Shigella, and E. coli
Contact between the bactgeria and the host cells simtulates the process
Low calcium levels may be required for secretion
Found in Salmonella, Pseudomonas, Yersinia, Shigella, and E. coli
Contact between the bactgeria and the host cells simtulates the process
Low calcium levels may be required for secretion
Type III and virulence factorsExclusive to Gram NegativeType III and virulence factorsExclusive to Gram Negative
Type III Secretion Pathway
Four different types of proteins
The secretory portion, the regulators, the proteins that aid in the insertion of secreted proteins, and effectors that alter host function
Type III Secretion Pathway
Four different types of proteins
The secretory portion, the regulators, the proteins that aid in the insertion of secreted proteins, and effectors that alter host function
Examples of Type IIIExamples of Type III
Cytotoxins Phagocytosis inhibitors Stimulators for reorganization of
the cytoskeleton Apoptosis promoters
Cytotoxins Phagocytosis inhibitors Stimulators for reorganization of
the cytoskeleton Apoptosis promoters
The Mxi-Spa Type III Secretory Pathway of Shigella flexneri
Outer Membrane Lipoprotein, MxiM for Invasin translocation
Raymond Schuch and Anthony Maurelli
The Mxi-Spa Type III Secretory Pathway of Shigella flexneri
Outer Membrane Lipoprotein, MxiM for Invasin translocation
Raymond Schuch and Anthony Maurelli Invasion of epithelial cells is mediated by
the Mxi-Spa, Type III secretion system The this type III secretion is activated by
pathogen and host cell interaction The secretion of these factors interacts with
the host cell membrane to initiate entry Regulated and mediated by invasion
plasmid proteins Lyse the endosomal compartment and
spread
Invasion of epithelial cells is mediated by the Mxi-Spa, Type III secretion system
The this type III secretion is activated by pathogen and host cell interaction
The secretion of these factors interacts with the host cell membrane to initiate entry
Regulated and mediated by invasion plasmid proteins
Lyse the endosomal compartment and spread
ShigellaShigella
Shigella species are aerobic, nonmotile, glucose-fermenting, gram-negative rods that are highly contagious, causing diarrhea after ingestion of as few as 180 organisms. Shigella species cause damage by 2 mechanisms, invasion of the colonic epithelium, which is dependent on a plasmid-mediated virulence factor, and production of enterotoxin, which is not essential for colitis but enhances virulence. The organism is spread by fecal-oral contact; via infected food or water; during travel; or in long-term care facilities, day care centers, or nursing homes.
Shigella species are aerobic, nonmotile, glucose-fermenting, gram-negative rods that are highly contagious, causing diarrhea after ingestion of as few as 180 organisms. Shigella species cause damage by 2 mechanisms, invasion of the colonic epithelium, which is dependent on a plasmid-mediated virulence factor, and production of enterotoxin, which is not essential for colitis but enhances virulence. The organism is spread by fecal-oral contact; via infected food or water; during travel; or in long-term care facilities, day care centers, or nursing homes.
ArticleArticle
Philos Trans R Soc Lond B Biol Sci. 2000 May 29;355(1397):681-93.Related Articles, Links
Type III secretion: a bacterial device for close combat with cells of their eukaryotic host.
Cornelis GR.
Microbial Pathogenesis Unit, Christian de Duve Institute of Cellular Pathology (ICP), Universite Catholique de Louvain, Brussels, Belgium. cornelis@mipa.ucl.ac.be
Philos Trans R Soc Lond B Biol Sci. 2000 May 29;355(1397):681-93.Related Articles, Links
Type III secretion: a bacterial device for close combat with cells of their eukaryotic host.
Cornelis GR.
Microbial Pathogenesis Unit, Christian de Duve Institute of Cellular Pathology (ICP), Universite Catholique de Louvain, Brussels, Belgium. cornelis@mipa.ucl.ac.be
Type IVType IV
Virulence Related Secretory Pathway Span both membranes of the gram-
negative bacterial cell or one membrane of the gram-positive
Agrobacterium tumefaciens transports DNA into plant cells
But Bordetella pertussis( whooping cough) uses a similar system to transfer the pertussis toxin into host cells
Virulence Related Secretory Pathway Span both membranes of the gram-
negative bacterial cell or one membrane of the gram-positive
Agrobacterium tumefaciens transports DNA into plant cells
But Bordetella pertussis( whooping cough) uses a similar system to transfer the pertussis toxin into host cells
Insertion of Proteins in the Cell Membrane
Insertion of Proteins in the Cell Membrane
The Oxal family consists of membrane insertases.
In E. coli, these proteins function primarily to insert proteins into membranes
The Oxal family consists of membrane insertases.
In E. coli, these proteins function primarily to insert proteins into membranes
Bacterial Endospores – agents of survival not
dispersal
Bacterial Endospores – agents of survival not
dispersal formed by some bacteria dormant resistant to numerous environmental
conditions heat radiation chemicals desiccation
formed by some bacteria dormant resistant to numerous environmental
conditions heat radiation chemicals desiccation
Resistance toResistance to
Acids and bases Heat Radiation Reactive oxygen
Acids and bases Heat Radiation Reactive oxygen
Resistance of endospore is the result of
Resistance of endospore is the result of
Calcium (complexed with dipicolinic acid)
Acid-soluble, DNA-binding proteins Dehydrated core Spore coat DNA repair enzymes
Calcium (complexed with dipicolinic acid)
Acid-soluble, DNA-binding proteins Dehydrated core Spore coat DNA repair enzymes
Electron Micrograph of endospore
Electron Micrograph of endospore
CW = Vegetative cell wall
CP= Spore Coat SC= Spore Cortex EX= Exosporium
CW = Vegetative cell wall
CP= Spore Coat SC= Spore Cortex EX= Exosporium
Position of endosporePosition of endospore
Spore LocationSpore Location The position of the endospore differs among bacterial
species and is useful in identification. The main types within the cell are terminal, subterminal and centrally placed endospores. Terminal endospores are seen at the poles of cells, whereas central endospores are more or less in the middle. Subterminal endospores are those between these two extremes, usually seen far enough towards the poles but close enough to the center so as not to be considered either terminal or central. Lateral endospores are seen occasionally.
Examples of bacteria having terminal endospores include Clostridium tetani, the pathogen which causes the disease tetanus. Bacteria having a centrally placed endospore include Bacillus cereus, and those having a subterminal endospore include Bacillus subtilis. Sometimes the endospore can be so large the cell can be distended around the endospore, this is typical of Clostridium tetani.
The position of the endospore differs among bacterial species and is useful in identification. The main types within the cell are terminal, subterminal and centrally placed endospores. Terminal endospores are seen at the poles of cells, whereas central endospores are more or less in the middle. Subterminal endospores are those between these two extremes, usually seen far enough towards the poles but close enough to the center so as not to be considered either terminal or central. Lateral endospores are seen occasionally.
Examples of bacteria having terminal endospores include Clostridium tetani, the pathogen which causes the disease tetanus. Bacteria having a centrally placed endospore include Bacillus cereus, and those having a subterminal endospore include Bacillus subtilis. Sometimes the endospore can be so large the cell can be distended around the endospore, this is typical of Clostridium tetani.
StainingStaining Visualising endospores under the light
microscope can be difficult due to the impermability of the endospore wall to dyes and stains. While the rest of a bacterial cell may stain, the endospore is left colourless. To combat this, a special stain technique called a Moeller stain is used. The allows the endospore to show up as red, while the rest of the cell stains blue. Another staining technique for endospores is the Schaeffer-Fulton stain, which stains endospores green and bacterial bodies red.
Visualising endospores under the light microscope can be difficult due to the impermability of the endospore wall to dyes and stains. While the rest of a bacterial cell may stain, the endospore is left colourless. To combat this, a special stain technique called a Moeller stain is used. The allows the endospore to show up as red, while the rest of the cell stains blue. Another staining technique for endospores is the Schaeffer-Fulton stain, which stains endospores green and bacterial bodies red.
Spore stainingSpore staining
Swollen terminal regionSwollen terminal region
SporogenesisSporogenesis
Normally commences when growth ceases because of a depletion of Nutrients
Sensitive low levels of Nitrogen and Phosphorus
Complex multistage process
Normally commences when growth ceases because of a depletion of Nutrients
Sensitive low levels of Nitrogen and Phosphorus
Complex multistage process
Formation of the Vegetative Cell- Sporulation or Sporogenesis
Formation of the Vegetative Cell- Sporulation or Sporogenesis
Complex, multistage process
Commences in response to environmental conditions such as a lack of nutrients
Complex, multistage process
Commences in response to environmental conditions such as a lack of nutrients
StepsSteps
The nucleoid lengthens forming a structure called the axial filament ( axial filament formation can be induced by exposure in early exponential growth phase by the antibiotic, chloramphenicol.
Inward folding of the cell membrane to enclose part of the DNA and produces the polar septum. The larger product is the mother cell, the smaller product is the forespore
The nucleoid lengthens forming a structure called the axial filament ( axial filament formation can be induced by exposure in early exponential growth phase by the antibiotic, chloramphenicol.
Inward folding of the cell membrane to enclose part of the DNA and produces the polar septum. The larger product is the mother cell, the smaller product is the forespore
Forespore and DNAForespore and DNA
Upon formation – only 30% of the DNA is in the forespore – the remainder enters prior to the formation of the septum
The mother cell sends out pseudopods that act in the same way a phagocyte to surround the forespore
The two cells face each other and a murein wall is laid down between
Upon formation – only 30% of the DNA is in the forespore – the remainder enters prior to the formation of the septum
The mother cell sends out pseudopods that act in the same way a phagocyte to surround the forespore
The two cells face each other and a murein wall is laid down between
Sporulation continuedSporulation continued
Protein coats are then formed around the cortex
Maturation of the spore occurs
Protein coats are then formed around the cortex
Maturation of the spore occurs
Structure continuedStructure continued
Dipocolinic acid and Calcium ions are accumulated - the forespore dehydrates
Outside of the cells a thick protective coat is synthesized
This thick layer is known as the cortex It may be surrounded by a membrane
known as the exosporium
Dipocolinic acid and Calcium ions are accumulated - the forespore dehydrates
Outside of the cells a thick protective coat is synthesized
This thick layer is known as the cortex It may be surrounded by a membrane
known as the exosporium
Quorum sensing and Sporulation
Quorum sensing and Sporulation
Sporulation is controlled by a complex series of molecular communications known as quorum sensing
The number of cells must reach a certain population and secrete peptides that trigger sporulation
Sporulation is controlled by a complex series of molecular communications known as quorum sensing
The number of cells must reach a certain population and secrete peptides that trigger sporulation
SpoASpoA
Sporulation is initiated by the signals that initiate phosphorylation and activation of SpoA which is a DNA binding protein
The cascade of events occurs as a result of the SpoA phosphorelay system
Further regulation of SpoA is through kinases and phosphatases
Sporulation is initiated by the signals that initiate phosphorylation and activation of SpoA which is a DNA binding protein
The cascade of events occurs as a result of the SpoA phosphorelay system
Further regulation of SpoA is through kinases and phosphatases
Steps in ActivationSteps in Activation
Activation prepares spores for germination often results from treatments like heating
Germination spore swelling rupture of absorption of spore coat loss of resistance increased metabolic activity
Outgrowth emergence of vegetative cell
Activation prepares spores for germination often results from treatments like heating
Germination spore swelling rupture of absorption of spore coat loss of resistance increased metabolic activity
Outgrowth emergence of vegetative cell
CDC and Anthrax Fact Sheet
CDC and Anthrax Fact Sheet
http://www.bt.cdc.gov/agent/anthrax/faq/
http://www.bt.cdc.gov/agent/anthrax/faq/
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