Microbio (Exam 2): Ch 4 Bacterial Culture, Growth, Development

Required micronutrients

Co, Cu, Mn, Mo, Ni, Z

Growth factors

vitamins, amino acids, blood, serum

Nutritional wild typ

phototroph

Auxotroph nutritional type

deficient in a metabolic pathway

Defined (synthetic, minimal) media

requirements for fastidious bacteria

generation time

doubling time; length of time for a cell to divide

lag phase

temporarily no growth, acclimating, turning on/off genes, synthesis

factors affecting lag phase:

inoculum age, size, media, physical factors

log phase

most metabolically active state, fastest growth, cell size increases

late log phase

begins slow down in growth

stationary phase

nutrient limited, growth rate = death rate, cell size decreases, stress response

death phase

lack of nutrients and pH changes → exponential decline in cell numbers

dormancy/persistence

growth arrested cells that remain viable; maintain membrane potential to provide energy

fed-batch culture

feed additional nutrients at mid-log phase

biofilm development

occurs in stages via chemical/environmental signals

biofilm initiation

planktonic cells (free swimming)

biofilm attachment

fimbriae; swimmers → stickers

biofilm maturation

exopolysaccharide formation

biofilm maintenance

2D → 3D growth; biofilm towers

biofilm dissolution

breakdown; triggered by starvation; stickers → swimmers

quorum sensing

cellular communication triggers formation of exopolysaccharide from microcolony forming extracellular matrix of molecules

quorum sensing requirement

nutrient driven and cell density dependent

endospore formation

response to environmental stress

Bacillus endospores

aerobic

Clostridium endospore

obligate anaerobes

spore germination

in favorable conditions

sporulation

8 hour genetic process directing asymmetrical division to form a spore

unequal compartments during sporulation form:

mother cell & forespore

thick spore coat made of:

peptidoglycan

endospore formation: 1. DNA replication

axial filament formation & segregation

endospore formation 2. septum formation

forespore and mother cell form, each with DNA copy

endospore formation 3. mother cell engulfs forespore

thick spore coat forms

endospore formation 4. spore released

dipicolinic acid and calcium incorporated