Microbiology Gülfem hoca

• thick hydrophilic gel layer; Polysaccharide/-peptide

• protection (chemical & biologic threats)

• metabolic processes

• stained with special capsular stains

• reasonable discrete layer -> capsule

• amorphous layer -> slime layer (often in orthopedic prosthetic)

• Capsule (can’t recognize)

• Peptidoglycan (can’t get degraded except with lysozyme in tears & other secretions )

• Antibiotic target Peptidoglycan (transpeptidase responsible for crosslinks) -> blocks crosslink formation

Mycoplasmas

Chlamydia sp.

• thick peptidoglycan (NAG & NAM crosslinks)

• teichoic acids (f.e. lipoteichoic acid -> adhesion)

• sometimes polysaccharides (specific antigen) or proteins (virulent M protein)

1. Cytosol: series of reactions -> Nacetylmuramic acid (NAM) residue bearing a pentapeptide on nucleotide carrier (UDP)

2. UMP released -> precurser attached to bacteroprenol (special lipid like carrier)

3. Nacetylglucosamine (NAG) added to precursor -> bridge between adjacent tetrapeptides

4. disaccharide subunit attached to the end of a growing glycan chain -> crosslinks via transpeptidases

• Transpeptidase

• Penicillin targets transpeptidase (responsible for Peptidoglycan crosslinks) -> blocks crosslink formation

• thinner Peptidoglycan & lipoprotein layer

• Periplasm

• outer membrane (surface protein f.e. porins; lipopolysaccharide)

• hydrolytic enzymes

• antibiotic inactivating enzymes

• proteins for chemotaxis, transport, secretion, and surface molecule anchoring

Lipopolysaccharide in Gram negative bacteria (Lipid A portion)

Endotoxic shock, fever, sepsis

Mycoplasmas in the bacterial cell membrane

• attached to cell membrane

• plays a role in the segregation of daughter chromosomes at cell division

• Mitotic apparatus bc bacterial chromosome attached at cell membrane

• Mitochondria bc electron transport system at cell membrane

• Receptors important for chemotaxis

• Secretes exotoxins & hydrolytic enzymes out

• Pilli (common or sex pili)

• made up of pilin (tube & hollow core)

• Adhesin (sometimes specialized for adherence to certain cell type f.e. uroepithelial cells leading to UTI)

• Gram negative bacteria

• Conjugation (exchange of gen. material)

granular cytoplasm (bc high ribosomes & high pr. synth.)

fibrous nucleoid

• Eukaryotic

  • 80S

    • 60S + 40S subunit

• Prokaryotic

  • 70S

    • 50S + 30S subunit

• pilli

• modif. of cytoskeleton

• binding iron (blood transferrin, secretions lactoferrin, bacteria siderophores)

• not genes for survival but specialized genes

  • f.e. mediate antimicrobial resistance, virulence…

• nutrient limitation etc. -> bacteria prod. spores (sporulation) -> resistant to environmental conditions (due to low water & calcium dipicolinate), can persist for centuries

  • biological weapon

• spore former normally Gram positive rods

• nutrients from environment (water, ox., c.d.) -> passive or facilitated diffusion (conc. gr.)

  • Embden–Meyerhof glycolytic pathway, pentose phosphate pathway, Krebs cycle

• active transport (f.e. get rid of antibiotics)

• bacteria secretes siderophores -> trap Fe3+ -> active transport

• substrate phosphorylation in fermentation

• recombination of substrate phosphorylation and oxidative phosphorylation in respiration

• Oxygen -> Superoxide

• if Superoxide not detoxified -> intracellular killing mechanism -> must grow anaerobically using fermentation (still moderately aerotolerant)

• if survives, superoxide dismutase & catalase broke it down -> (facultative) aerobic bacteria

bacteria must synthesize folic acid to reproduce -> inhibit this pathway

• antibiotic against UTI

• inhibit DNA gyrase (enzyme participating in DNA replication)

• RNA Polymerase

• blocks the initiation of transcription

• tuberculosis

• simplest and most common mechanism for protein secretion (Gram pos. & neg.)

High rate (20 min) -> e.coli

Low rate (20 hours) -> mycobacteria f.e. tuberculosis

• Transposition = transfer via insertion sequences IS (from one chr. to another, one location to another on same chr.,between chr. & plasmid)

• Transformation = DNA from environment encoded by chromosomal genes & activated under certain conditions

• Transduction = transfer of genetic information from donor to recipient cell by phages

• Conjugation = Transduction (mostly plasmid) but with intimate cell contact not phage

• weakness/fatigue

• weight loss

• non-productive cough

• mycolic acid (sputum microscopy)

• transmissibility/initiation

• adherence

• persistence (essential for survival)

• invasion (enter & spread)

• toxigenicity

• ability to evade or survive the host’s immune system

• “polyclonal stimulators of T cells”

• Protein exotoxins that bind to MHC II & TCR -> stimulate high cytokines production by T-cells (Il1, TNF…)

• toxic shock syndromes (aureus and group A streptococci), diarrhea, vomiting

E coli

Campylobacter

Salmonella

scabies

Gram positive teichoic acids & carbohydrates

Gram negative outer membrane

Human epithelial receptors mannose & fibronectin

• Exotoxin mediated (f.e. diphtheria, whooping cough)

• protein toxic to human host secreted by bacteria into body fluids

Invasin (bact.) interact with integrin (host) -> cytoskeleton stimulating modifications -> bacteria inside in membrane bound hostvesicular structure

exploit cell uptake mechanism (take up bact. instead of nutrients)

• Listeria & Shigella (lyse membrane & escape)

• Salmonella serotype Typhi, Mycobacterium tuberculosis (remain in phagosome & replicate inside phagocyte)

• prevent phagosome–lysosome fusion or, if fused, block acidification (digestive enzymes can’t function)

• neutralize phagocytes’ oxidative burst by producing neutralizing enzymes (catalase, superoxide dismutase).

• Change structure of surface structures etc

  • Antigenic Variation (on surface)

    • specific IgG binds its homologous antigen -> subpopulation with antigenically different surface multiplies & inf. continues

    • f.e. Gonorrhea -> common reinfections

  • Gram negative: Modification of Lipid A (Salmonella, Pseudomonas) -> escape Antimicrobial peptides (AMPs) -> in some pathogens already hard to recognize (Helicobacter, Legionella, Yersinia)

  • Gram positive: alter teichoic acids

• Disrupt Complement system

  • binding to f.e. C3b receptors in serum (capsule of pathogens causing pneumonia or meningitis)

  • surface acquisition of sialic acid

cell able to sense presence of other members of the same species -> produce virulence factors only when needed

• pathogenicity island (unique regions on chromosome assoc. with virulence)

• in most tissues

• when bacteria reaches subepithelial tisuue & sufficient lysozyme concentration -> disrupt Gram positive bacteria cell wall

G protein -> important for signal transduction

-> cholera: downregulation occurs & stim. of steroid prod. in adrenal gl.

Exotoxin: proteins secreted by pathogen

Endotoxin: structure on pathogen´s cell wall etc

Endotoxins