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Micro - Bacterial Morphology + Physiology (ii) (Bacterial energy…
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
energy
appropriate environment
but are highly adaptive
temp of 20-110
pH of 4-9
aerobic or anaerobic
building blocks (nutrients)
for anabolism
H2O
N
inorganic salts
Fe
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)
growth phases
lag
bacteria still adapting to environment
log
nutrient abundance, no inhibition, multiplying @ max rate
stationary
lack of nutrients, toxic metabolite buildup, multiplication rate = death rate
decline
depleted nutrients
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
antigen presented here - LPS bilayer (aka endotoxin)
composed of O antigen + porin protein
cause gram -ve sepsis by binding to LPS BP on monocyte/macrophage cell surface
activates TLR4, hence NFkappa-beta
wall
rigid layer of peptidoglycan
cross-linked (via B1,4-glycosidic bond) polysacc
gives cell shape + prevents osmotic lysis
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)
thick in gram +ve, thin in gram -ve
adherence NB - fights against expulsion via coughing, sneezing, urination etc
antigens presented here
teichoic + lipoteichoic acid on gram +ve
extend into environment
NB adherence
cause gram +ve sepsis
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