microbiology
DESCRIPTION
Prokaryotes, Eukaryotes, etc.TRANSCRIPT
Prokaryotes and
Eukaryotes
Classification of OrganismsHaeckel (1894)Three
kingdoms
Whittaker (1959)Five
kingdoms
Woese (1977)Six kingdoms
Woese (1990)Three
domains
ProtistaMonera
Eubacteria Bacteria
Archaebacteria Archaea
Protista Protista
EukaryaPlantaeFungi Fungi
Plantae Plantae
Animalia Animalia Animalia
Major DifferenceCHARACTERISTICS PROKARYOTES EUKARYOTESNucleus Non-membrane
boundMembrane bound
DNA single multipleChromosome Circular LinearHistones -/+ +Organelles - +Cell wall Peptidoglycan -/ cellulose/ chitinReproduction Binary fission Asexual/ sexualRibosomes 70s 80sETS Cell membrane mitochondria
Bacteria
Bacteria are prokaryotic cells, the simplest of microbial cells. They consist of cell portoplasm contained within a retaining a structure or cell envelope.
prokaryotic simple, single-celled organisms distinct cell wals containing peptidoglycan
layerNo true nucleus (only nucleoid) free-floating DNA (some w/ plasmid)
MORPHOLOGY
Prokaryotes exhibit a variety of shapes
– Most common
• Coccus– Spherical
• Bacillus– Rod or cylinder
shaped
MORPHOLOGY
Prokaryotes exhibit a variety of shapes
– Other shapes• Coccobacillus
– Short round rod• Vibrio
– Curved rod• Spirillum
– Spiral shaped• Spirochete
– Helical shape• Pleomorphic
– Bacteria able to vary shape
MORPHOLOGY
Division along a single plane may result in pairs or chains of cells
– Pairs = diplococci• Example: Neisseria
gonorrhoeae
– Chains = streptococci
• Example: species of Streptococcus
Arrangement:
MORPHOLOGY
Division along several random planes form clusters
– Example: species of Staphylococcus
Arrangement:
Division along two or three perpendicular planes form cubical packets
– Example: Sarcina genus
General Structure
General Structure of a Prokaryotic Cell
CELL APPENDAGES
FLAGELLA
• Some bacteria have protein appendages– Not essential for life
• Aid in survival in certain environments
– They include• Flagella• Pili
FLAGELLA
Flagella– Long protein structure– Responsible for motility
• Use propeller like movements to push bacteria
• Can rotate more than 100,00 revolutions/minute
– 82 mile/hour
– Some important in bacterial pathogenesis
• H antigen useful in distinguishing among serovras of gram negative bacteria
FLAGELLAFlagella structure has three basic parts
– Filament• Extends to exterior• Made of proteins called
flagellin
– Hook• Curved sheath• Connects filament to cell
– Basal body• Anchors flagellum into
cell wall and membrane
Figure 4.8b
FLAGELLAR ARRANGEMENTS
1. Monotrichous – single flagellum at one end2. Lophotrichous – small bunches arising from one end
of cell3. Amphitrichous – flagella at both ends of cell4. Peritrichous – flagella dispersed over surface of cell,
slowest
FLAGELLAR ARRANGEMENTS
FLAGELLA
Motile Cells
Axial Filaments
• Endoflagella• In spirochetes• Anchored at one end
of a cell• Rotation causes cell
to move
PILI
• Rigid tubular structure made of pilin protein
•Found only in Gram negative cells
•Functions – Sexual pili—joins bacterial cells for DNA
transfer (conjugation)– Common pili—adhesion
FIMBRAE
•Fine hairlike bristles from the cell surface
•Function in adhesion to other cells and surfaces
CELL ENVELOPE
GLYCOCALYX• Coating of molecules external to the cell wall,
made of sugars and/or proteins• 2 types
1. slime layer - loosely organized and attached2. capsule – highly organized, tightly attached
• Functions– attachment– inhibits killing by white blood cells– receptor
BIOFILM
Dental Plaque A polysaccharide-encased
mass of bacteria coating the surface of a tooth
Streptococcus mutans uses sucrose to synthesize a biofilm
Other bacteria can then adhere to the layer
(a) The appearance of colonies composed of encapsulated cells (mucoid) compared with those lacking capsules (nonmucoid).
(b) Staining reveals the microscopic appearance of a large, well- developed capsule.
CELL WALL
• Bacterial cell wall – Rigid structure– Surrounds cytoplasmic membrane– Determines shape of bacteria– Holds cell together– Prevents cell from bursting– Unique chemical structure
• Distinguishes Gram positive from Gram-negative
GRAM POSITIVE GRAM NEGATIVE
GRAM POSITIVE WALL
•Rigidity of cell wall is due to peptidoglycan (PTG)
– Compound found only in bacteria
•Basic structure of peptidoglycan
– Alternating series of two subunits• N-acetylglucosamine (NAG)• N-acetylmuramic acid (NAM)
– Joined subunits form glycan chain• Glycan chains held together by
string of four amino acids– Tetrapeptide chain
GRAM POSITIVE WALL– Relatively thick layer of peptidoglycan
• As many as 30– Regardless of thickness, peptidoglycan is permeable to
numerous substances
– Teichoic acid component of peptidoglycan; composed of glycerol and phosphate
– Lipoteucholic acid is attached to the lipids of cytoplasmic membrane
• Gives cell negative charge
GRAM POSITIVE WALL
GRAM POSITIVE GRAM NEGATIVE
GRAM NEGATIVE WALL
– More complex than Gram+– Only contains thin layer of
peptidoglycan• Peptidoglycan sandwiched
between outer membrane and cytoplasmic membrane
• Region between outer membrane and cytoplasmic membrane is called periplasm or periplasmic space
– Gel-like area– Most secreted proteins
contained here
GRAM NEGATIVE WALL
• Outer membrane Connected to the peptidoglycan layer by lipoproteins Constructed of lipid bilayer
• Much like cytoplasmic membrane but outer layer made of lipopolysaccharides and phospholipids
• Outer membrane also called the lipopolysaccharide layer or LPS layer
– LPS severs as barrier to a large number of molecules• Small molecules or ions pass through channels called
porins• Specific channel proteins are present
GRAM NEGATIVE WALL
•O-specific polysaccharide chain– Directed away from membrane
• Opposite location of Lipid A– Used to identify certain species or strains
• E. coli O157:H7 refers to specific O-side chain
•Lipid A– Portion that anchors LPS molecule in lipid bilayer– Plays role in recognition of infection
• Molecule present with Gram negative infection of bloodstream--endotoxin
GRAM NEGATIVE WALL
Gram-Positive Membrane
Gram-Negative Outer Membrane
CELL WALL• Peptidoglycan layer as a target
– Many antimicrobial interfere with the synthesis of peptidoglycans or alter its structural integrity
– Examples include• Penicillin• Lysozyme
• Penicillin– Binds proteins involved in cell wall synthesis
• Prevents cross-linking of glycan chains by tetrapeptides
– More effective against Gram positive bacterium• Due to increased concentration of peptidoglycans• Penicillin derivatives produced to protect against Gram negatives
CELL WALL
• Lysozymes– Produced in many body fluids including tears and
saliva– Breaks bond linking NAG and NAM
• Destroys structural integrity of cell wall
– Enzyme often used in laboratory to remove peptidoglycan layer from bacteria
• Produces protoplast in G+ bacteria• Produces spheroplast in G- bacteria
CELL WALL
• Differences in cell wall account for• differences in staining• Characteristics:
– Gram-positive bacterium retain crystal violet-iodine complex of Gram stain
– Gram-negative bacterium lose crystal violet-iodine complex
The Gram Stain
CELL WALL
• Some bacterium naturally lack cell wall– Mycoplasma
• Bacterium causes mild pneumonia• Have no cell wall
–Antimicrobial directed towards cell wall ineffective
• Sterols in membrane account for strength of membrane
CYTOPLASMIC MEMBRANE
• Cell (Cytoplasmic) membrane– Delicate thin fluid structure– Surrounds cytoplasm of cell– Defines boundary– Serves as a semi permeable barrier
• Barrier between cell and external environment
CELL MEMBRANE
•Structure is a lipid bilayer with embedded proteins
– Bilayer consists of two opposing layers
• Layer composed of phospholipids
– Each contains a hydrophilic phosphate head and hydrophobic fatty acid tail
CELL MEMBRANE
•Membrane is embedded with numerous protein
– More that 200 different proteins– Proteins function as receptors,
channels proteins, and transport proteins
– Provides mechanism to sense surroundings
– Proteins are not stationary• Constantly changing position
– Called fluid mosaic model
CYTOPLASM
CYTOPLASM
• Dense gelatinous solution of sugars,• amino acids, & salts
• 70-80% water
• Serves as solvent for materials• used in all cell functions
STRUCTURES WITHIN CYTOPLASM
• Bacterial cells have variety of internal structures• Some structures are essential for life
– Chromosome– Ribosome
• Others are optional and can confer selective advantage– Plasmid– Storage granules– Endospores
INTERNAL STRUCTURES
Chromosome– Resides in cytoplasm
• In nucleoid space– Typically single chromosome: protein and DNA– Circular double-stranded molecule– Contains all genetic information
Plasmid– Circular DNA molecule
• Generally 0.1% to 10% size of chromosome– Extrachromosomal
• Independently replicating– Encode characteristic
• Potentially enhances survival– Antimicrobial resistance– Tolerance to toxic metals
INTERNAL STRUCTURE
Ribosome– Involved in protein synthesis– Composed of large and small
subunits• Units made of protein 40%
and ribosomal RNA 60%– Prokaryotic ribosomal subunits
• Large = 30S• Small = 50S
– Small than eukaryotic ribosomes
• Difference often used as target for antimicrobials
INTERNAL STRUCTURES
Storage granules– Accumulation of polymers
• Synthesized from excess nutrient– Example = glycogen
» Excess glucose in cell is stored in glycogen granules
Gas vesicles– Small protein compartments
• Provides buoyancy to cell• Regulating vesicles allows
organisms to reach ideal position in environment
INTERNAL STRUCTURES
Endospores– Dormant cell types
• Produced through sporulation• Theoretically remain dormant for
100 years– Resistant to damaging conditions
• Heat, desiccation, chemicals and UV light
– Vegetative cell produced through germination
• Germination occurs after exposure to heat or chemicals
• Germination not a source of reproduction
Common bacteria genus that produce endospores include Clostridium and Bacillus
Inclusions• Metachromatic granules
(volutin)• Polysaccharide granules• Lipid inclusions• Sulfur granules• Carboxysomes
• Gas vacuoles• Magnetosomes
• Phosphate reserves
• Energy reserves• Energy reserves• Energy reserves• Ribulose 1,5-diphosphate
carboxylase for CO2 fixation• Protein covered cylinders• Iron oxide
(destroys H2O2)
Inclusions
Archaea
• primitive prokaryotes• extermophiles• lacks peptidoglycan in their cell wall• ether-linked membrane lipids
Phylogenetic Tree of Archaea
Archaea Morphology
Basic Archaeal Shapes : At far left, Methanococcus janaschii, a coccus form with numerous flagella attached to one side. At left center, Methanosarcina barkeri, a lobed coccus form lacking flagella. At right center, Methanothermus fervidus, a short bacillus form without flagella. At far right, Methanobacterium thermoautotrophicum, an elongate bacillus form.
Archaea Morphology
• Membrane lipids– ether bonds link glycerol to hydrocarbon side
chains– lacks fatty acids– side chains composed of repeating isoprene units– major lipid components: glycerol diether and
diglycerol teraether– lipid monolayer
Archaea Morphology
Archaea Morphology
• Cell Wall– lacks outer membrane– pseudomurein:
• N-acetylglucosamine + N –acetyltalosaminuronic acid• β-1,3 glycosidic linkage• L-amino acids
– Polysaccharide cell walls• Methanosarcina: glucose, glucuronic acid, uronic acid
galactosamine, and acetate• Halococcus: same as Methanosarcina cell wall + Sulfate
ions
Archaea Morphology
• Cell Wall– S-layers: paracrystalline surface layers
• proteins or glycoprotein arranged in various symmetries
• Functions:– structural support– interface btwn cell and its environment– selective sieve– retain proteins near cell surface
Archaea Morphology
• Other Cell Walls– Natronococcus: haloalkalophilic species of
Archaea• glycoprotein cell wall contains L-glutamate as a single
type of amino acid linking glucose and glucose derivatives
Archaea
• Crenarchaeaota: most thermophilic archaea are found in this group. They use sulfur compounds as electron donors or as acceptors. Not all are thermophilic.
• Euryarcheota: methanogens, halophiles, thermophiles.
• Korarcheota; found in hot springs. None have been grown in pure culture.
The hot springs of Yellowstone National Park, USA, were among the first places Archaea were discovered. At left is Octopus Spring, and at right is Obsidian Pool. Each pool has slightly different mineral content, temperature, salinity, etc., so different pools may contain different communities of archaeans and other microbes. The biologists pictured above are immersing microscope slides in the boiling pool onto which some archaeans might be captured for study.
Salt-lovers : immense bloom of a halophilic ("salt-loving") archaean species at a salt works near San Quentin, Baja California Norte, Mexico. This archaean, Halobacterium, also lives in enormous numbers in salt ponds at the south end of San Francisco Bay; interested residents of this area should take the Dumbarton Bridge for the best views.
Figure 4.22a
Eukarya
Flagella and Cilia
Figure 4.23a–b
Figure 4.23c
• Microtubules • Tubulin• Nine pairs + two arrangements
Cell Wall
• Cell wall– Plants, algae, fungi– Carbohydrates
• Cellulose, chitin, glucan, mannan• Glycocalyx
– Carbohydrates extending from animal plasma membrane
– Bonded to proteins and lipids in membrane
Plasma Membrane
• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins• Sterols• Glycocalyx carbohydrates
Plasma Membrane• Selective permeability allows passage of some
molecules• Simple diffusion• Facilitative diffusion• Osmosis• Active transport• Endocytosis
– Phagocytosis: Pseudopods extend and engulf particles.– Pinocytosis: Membrane folds inward bringing in fluid and
dissolved substances.
Eukaryotic Cell• Cytoplasm membrane:Substance inside plasma
and outside nucleus• Cytosol: Fluid portion of cytoplasm• Cytoskeleton: Microfilaments, intermediate
filaments, microtubules• Cytoplasmic streaming: Movement of cytoplasm
throughout cells
Organelles• Membrane-bound
– Nucleus: Contains chromosomes– ER: Transport network– Golgi complex: Membrane formation and secretion– Lysosome: Digestive enzymes– Vacuole: Brings food into cells and provides support– Mitochondrion: Cellular respiration– Chloroplast: Photosynthesis– Peroxisome: Oxidation of fatty acids; destroys H2O2
Eukaryotic Cell
• Not membrane-bound– Ribosome: Protein synthesis– Centrosome: Consists of protein fibers and
centrioles– Centriole: Mitotic spindle formation
Nucleus
Figure 4.24
Endoplasmic Reticulum
Figure 4.25
Ribosomes
• 80S– Membrane-bound Attached to ER– Free In cytoplasm
• 70S– In chloroplasts and mitochondria
Golgi Complex
Figure 4.26
Lysosomes and Vacuoles
Figure 4.22b
Mitochondrion
Figure 4.27
Chloroplast
Figure 4.28
Figures 10.2, 10.3
Endosymbiotic Theory
Endosymbiotic Theory
UN 4.1
Comparison of the Three DomainsCHARACTERISTICS BACTERIA ARCHAEA EUKARYA
Cell Nucleus - - +Chromosome Single, circular Single, circular Multiple, linearHistone Proteins - + +Peptidoglycan Cell Wall + - -
Membrane lipids Ester-linked Ether-linked Ester-linkedRibosome sedimentation rate
70s 70s 80s
Ribosome susceptibility to diptheria toxin
- + +
1st amino acid in protein
Formylmethionine Methioine ,ethionine
Chlorophyll based photosynthesis
+ (cyannobacteria) - + (algae)
Growth above 80 OC + + -Growth above 100 OC - + -