Micro - Bacterial Morphology + Physiology (ii)

Binary fission

1 chromo divides

2 identical copies segregate + go to opposite ends of cell

cleavage to form 2 identical cells

v fast - 20 mins (mycobacteria slower)

hence adapt + evolve fast

in a hostile environment - selective pressure - mutations persist

growth requirements

growth phases

stationary

decline

bacteria still adapting to environment

nutrient abundance, no inhibition, multiplying @ max rate

lack of nutrients, toxic metabolite buildup, multiplication rate = death rate

depleted nutrients

energy

appropriate environment

but are highly adaptive

temp of 20-110

pH of 4-9

aerobic or anaerobic

building blocks (nutrients)

for anabolism

H2O

inorganic salts

oxidation of organic compounds (carbs, lipids, proteins)

energy via catabolism

some bacteria stains can synthesise all the AAs they need (autotroph), whereas some require additional nutrients (auxotrophs)

Bacterial energy production

required for metabolism, nutrient transport, movement via flagellae

occurs in cytoplasmic membrane

aerobic resp -> glycolysis + TCA -> ETC -> oxidation (O2 = terminal election acceptor)

anaerobic resp -> oxidised inorganic compounds

e.g. lactic acid in fermentation

obligate anaerobes lack superoxide dismutase

hence sensitive to ROS

alternative ETC + electron acceptor used (e.g. NO2)

antimetabolite antibiotics are bacteriostatic not bacteriocidal

during ETC protons are pushed out of cytoplasmic membrane, + return along gradient - generates ATP

bacterial genome

1 chromo

possibly also plasmids

bacterial envelope

cytoplasmic membrane surrounded by cell wall

wall surround by outer membrane in gram -ves

molecular sieve

adhesion

resistance to phagocytosis

wall

rigid layer of peptidoglycan

thick in gram +ve, thin in gram -ve

cross-linked (via B1,4-glycosidic bond) polysacc

gives cell shape + prevents osmotic lysis

membrane

lipids + phospholipids

osmotic barrier (only molecules smaller than glycerol can enter by diffusion

ATP production via oxidative phosphorylation (no ribosomes)

contains permeases for transport

cell wall synthesis

anchors chromo

90% of gram +ve cell envelope, on 2-20% in gram -ve (1 layer only)

cross linking inhibited by beta-lactams + vancomycin (bactericidal via osmotic lysis)

adherence NB - fights against expulsion via coughing, sneezing, urination etc

antigens presented here

teichoic + lipoteichoic acid on gram +ve

extend into environment

NB adherence

antigen presented here - LPS bilayer (aka endotoxin)

composed of O antigen + porin protein

cause gram +ve sepsis

cause gram -ve sepsis by binding to LPS BP on monocyte/macrophage cell surface

activates TLR4, hence NFkappa-beta