bacterial cell and its ultra structure handouts
TRANSCRIPT
Bacterial Cell and its Ultrastructure
Mary Joyce Saborrido- Teoxon, RMT, MD, PCOM. PSMAP
What do we expect? Briefly describe the different microscopes used to identify
microbial agents Differentiate Prokaryotes vs. Eukaryotes Describe a Prokaryotic cell Identify the parts of a Prokaryotic cell Enumerate its function Differentiate a gram-positive and gram-negative bacteria
Microscope LIGHT ELECTRON
Microscope Confocal Scanning Laser Microscope
Microscope Scanning Probe Microscope
Important Microbial Groups Prions Viruses Bacteria
FungiParasites
Differentiate
Bacterial Morphology Shape , Arrangement
* Pleomorphic
Coccus / Cocci
Bacillus / Bacilli
Gram stain Composition: VIAS
Crystal Violet Gram’s Iodine Alcohol / Acetone Safranin
General Rules in Gram Staining
All cocci are Gram + EXCEPT:- Neisseria- Moraxella- Veillonella
All bacilli are Gram – EXCEPT:- Mycobacterium- Corynebacterium- Bacillus- Clostridium- Actinomyces- Streptomyces
Less common bacilli- Erysipelothrix- Listeria- Nocardia- -bacterium (Bifido-, Propioni-, Eu-, Arcano- )
What is the Gram’s reaction ?
Streptococcus Staphylococcus Neisseria Bacillus Escherichia
Bacterial Envelope (All the concentric surface layers of the bacterial cell)
Envelope Structure
Gram + or -
Chemical Composition
Function
Capsule-Slime-Glycocalyx
Both Gram+/ -
Polysaccharide gel
Pathogenicity/ Virulence factor;Protect againstPhagocytosis untilOpsonized; immunogenic
Envelope Structure
Gram + or -
Chemical Composition
Function
Outer membrane
“ major permeability
barrier”
Gram-negative
only
Phospholipid/ proteins:
Lipopolysaccharide
Lipid A
Polysaccharide
Hydrophobic
Membrane:
LPS= endotoxin
Lipid A=
Toxic moiety
PS= immunogenic
Bacterial Envelope (All the concentric surface layers of the bacterial cell)
Outer Membrane
Envelope Structure
Gram + or -
Chemical Composition
Function
Gram + (thick)
Gram – (thin)
•Found in all free living bacteria EXCEPT
Mycoplasma
peptidoglycan; polymer of peptides (typically 4 amino acids long, cross-linked to other chains) and glycans (made of alternating amino sugars).
- Sugars found in peptidoglycan:
- N-acetylglucosamine (NAG).
- N-acetylmuramic acid (NAM).
Rigid support, cell shape, protection from osmotic damage Confer Gram reaction
Target of AB/ enzymes
Cell Wall =
Peptidoglycan
Cell wall
Cell Envelope Gram positive Gram negative
Envelope Structure
Gram + or -
Chemical Composition
Function
Cell Wall Acid-fast only
Mycolic acids Acid-fastness
Resistance to drying and chemicals
All organisms are non-acid fast EXCEPT:
Cryptosporidium sp.
Legionella micdadei
Isospora sp.
Mycobacterium sp
Nocardia sp.
Bacterial Envelope (All the concentric surface layers of the bacterial cell)
Envelope Structure
Gram + or -
Chemical Composition
Function
Periplasmic space Gram-negative only
“Storage space” between the inner and outer membranes
Stores degradative enxymes which break down large molecules, (β-lactamases)
Aids regulation of osmolarity
Bacterial Envelope (All the concentric surface layers of the bacterial cell)
Wall-less forms of Bacteria
Spheroplasts(+) OM
Protoplasts(-) OM
Envelope Structure
Gram + or -
Chemical Composition
Function
Cytoplasmic membrane
Both Phospholipid bilayer with many embedded proteins
Energy metabolism occurs here
Hydrophobic cell “sack”
Selective permeability and active transport
Envelope Structure
Gram + or -
Chemical Composition
Function
Pilus/ Fimbria
1. Common 2.Sex 3.Virulence
Primarily Gram -
Glycoprotein (pilin) Adherence to cell surfaces, including atachment to other bactera during conjugation
Envelope Structure
Gram + or -
Chemical Composition
Function
Flagellum
Axial Filaments
Both
Spirochetes
Protein (flagellin)
Protein
Motility
Motility
Internal Bacterial structure
Structure Gram + or -
Chemical Composition
Function
Nucleoid region
Also called neuclear body/ chromatin body/ nuclear region
Both DNA; RNA; Proteins Genetic material (all essential genes)
Internal Bacterial structureStructure Gram +
or -Chemical Composition
Function
Plasmids Both DNA Non-essential genetic material
Roles in conjugation, drug resistance, toxin production
Internal Bacterial structureStructure Gram +
or -Chemical Composition
Function
Ribosomes
Granules
Both
Both
70s
30s
50s
Glycogen, lipids, polyphosphate, etc.
CHON synthesis
Storage
Structure Gram + or -
Chemical Composition
Function
Endospores Gram + only Keratin coat, calcium dipicolinate
Resistance to heat, chemicals and dehydration
Internal Bacterial structure
Physiology, Growth and Nutrition Nutritional Requirements:1. Source of Carbon
A) Heterotrophs/ OrganotrophsB) Autotrophs/ Lithotrophs
photo-chemo-
2. Oxygen Requirement Obligate aerobes Obligate anaerobes Facultative anaerobes Microaerophiles Aerotolerant
3. Carbon dioxide
Capnophiles
PHYSICAL REQUIREMENTS
1. Redox potential (Eh)
Most culture media have Eh = +0.2 to +0.4V
Obligate anaerobes = requires – 0.2V
2. Temperature
Psychrophiles: -5 to 30 °C (opt 10-20) Mesophiles: 10 to 45 °C (opt 20-40) Thermophiles: 25 to 80 °C (opt 50-60)
3. pH
Acidophiles: 6.5 - 7.0 Neutrophiles: 7.5 - 7.8
**7.2 – 7.6 for medically important bacteria Alkalophiles: 8.4 – 9.0
BACTERIAL GROWTH
stationary
Log number log deathOf living cells/Tubidity
lag
Time (usually in hours)