Bacterial Structures Flashcards
Peptidoglycan
Function- Makes the cell wall backbone, is a murein layer. –Chemical composition- sugar backbone with peptide side chains crosslinked by trans peptidase. Alternating NAM and NAG have Beta 1-4 glycosidic bonds. the alanine(4thAA)binds to the lysine (3rd AA) in gram +ve and Diaminopimelic acid in Gram -ve lysine is a better bond and more of them
Cell wall/ Cell membrane(gram positives)
F: Major surface antigen CC: peptidoglycan for support. Lipoteichoic acid induces TNF and IL-1
Outer membrane
F:site of oxidative and transport enzymes CC: Lipid A induces TNF and IL-1, O Polysaccharide is the antigen
Plasma membrane
- F: site of oxidative transport enzymes(oxidative phosphorylation.),
- active transport,
- secretion of enzmes and toxins.
- export cell wall components
- Anchoring DNa during cell diviiaon (mesosome)
- chemotactic receptors are located here.
- CC: phospholipid bilayer with NO sterols except for Mycoplasma
Riobosome
F:Protein synthesis CC: 50S, 30S total is 70 S
Periplasm
F: space between the cytoplasmic membrane and outermembrane in gram negative bacteria CC:(loose network of peptidoglycan)hydrolytic enzyjmes, Beta-lactamases, proteases, nutrient transport proteins,
Capsule
F: Protects against phagocytosis CC: polysaccharide (Bacillus anthracis contains D-glutamate)
detected by the Quellung reaction, antserum + bacteria causes swelling of the capsule and you use specific antisera K/M for antigens for typing
pilus/fimbria
F: mediate adherence of bacteria to cell surface, sex pilus(gram -ve only) forms attachment between 2 bacteria during conjugation CC: glycoprotein (protein comp is Pilin
Flagellum
F: motility CC: protein
can be arranged polar- Mono, amphi, or lopho
can be arranged lateral- peritrichous
composed of 3 parts,
- Helical filament that inserts on hook and composed of Flagellin (H Antige
- hook- short curved structure anchors filament into the basal body.
- basal body- contains rod and 1 or 2 sets of double plate rings. 2 rings is G+ve and 4 rings is G-ve these rotate in CCW diretion to propel and a CW direction to reverse and disperse the flagella and create a tumbling motion.
Spore
F:resistant to dehydration, heat, chemicals, CC:keratin like coat, dipicolinic acid, peptidoglycan
compared to vegetative cells, have a thick spore coat and petidoglycan spore wall. calcium dipicolinic acid is present in core. no enzymatic activity and resistance to destruction.
This is considered differentiation. sporulation leads to spore, germination leads from spore to vegetative cell.
Plasmid
F: contains a variety of genes for antibiotic resistance enzymes and toxinsAntiboitic resistant is R plasmid, Mating capabilites is F plasmid.
Glycocalyx
SLIME Layer- EPS made of External polysaccharide- has poor attachment to the cell wall. this layer is easily removed and can attach to plastics, it also establishes a community of bacteria surrounded by slime usually associated with medical equipment like hip replacement or catheters
(Bacillus anthracis has a polypeptide
CAPSULE- also a glycocalyx
Function of Glycocalyx
- Adherance- Dental carries (streptococcus mutans), Glugans and Fructans
- Antigenic activity- EPS antigenic
- Antiphagocytic-the caspule covers antigens
- Prevent neutrophil killing of engulfed bacteria, lysosome doesn’t have acces to interior cell wall.
- Prevent PMN leukocyte migration to site of infection by paralyzing the leukocyte
- Toxicity to host cell-induces abscess formation
- Protection from oxygen toxicity, desiccation and nutrient loss
Axial Filaments
Motile bacteria LAck flagella like Pirochetes and leptospira
they are fagella like fillaments and are not exposed to the external environment it moves like a centepede.
Pathogenicity Islands
Distinct genetic elements on chromosome ahtat carry 1 or more virulence genes and present only in pathogen genome. the are frequently located next to tRNA
Gram +ve examples- Listerai, spp. S. aureus, Streptococcus spp., Enterococcus faecalis, Clostridium Difficile
Grame -ve examples- H. pylori, e. coli Slmonella spp., Shicella spp., yersinia spp., L. pneumophilia, P. Aeruginsoa, v. cholerae Bacteriodes fragilis.
