CH.7 - Bacterial & Archaeal Growth

binary fission

asexual reproduction in which a cell separates into 2 identical daughter cells; most common mechanism for bacterial cell division

Bacterial and Archaeal Cell Reproduction

1. Elongation of the cell

2. Replication of the chromosome

3. Separation of the chromosomes into two parts of the cell

4. Formation of the septum in the middle (via cytokinesis or septation)

cytokinesis (septation)

process of forming a cross wall between 2 daughter cells during cell division

origin of replication

site where DNA replication is initiated

Penicillin-binding protein (PBP)

group of proteins that hydrolyze bonds in existing peptidoglycan strands and link new strands

NAG and NAM

major components of peptidoglycan that bind to a membrane protein called bactoprenol

Autolysins

degrade polypeptide where new units are to be added, and the new NAM-NAG units can then be inserted into the peptidoglycan layer

Archaeal Cell Reproduction

reminiscent of a miotic cell cycle

coccus shaped

new peptidoglycan forms only at central septum

bacilli shaped

requires the use of elongasome

vibrio shaped

produce a cytoskeleton whose filaments insert new peptidoglycan

batch culture

growth of microorganisms in a closed culture vessel WITHOUT adding fresh or removing old medium

Lag phase (A)

period following the introduction of microorganisms into a fresh culture medium; when there is no increase in number of cells

Exponential Phase (B)

microbial population is growing at a constant and maximum rate, dividing and doubling at regular intervals

Stationary Phase (C)

population growth ceases and growth curve levels off

Death Phase (D)

equilibrium between dying and reproducing cells shifts and the number of viable cells decline exponentially

Long-term stationary phase

population size remains at a more or less constant low level for an extended period

budding

form of asexual reproduction seen in Listeria

Baeocyte formation

multiple rounds of cell division; seen in cyanobacteria

generation time

time it takes a population to double

hypotonic

when the environment has a lower solute concentration than the interior of the cell, the environment is . . .

hypertonic

when the environment has a higher solute concentration than the interior of the cell, the environment is . . .

sessile

microbial cells are attached to a solid substrate

planktonic

free-living microbes

biofilms

organized microbial communities encased in extracellular polymeric substances and associated w/ surfaces

emergent properties

properties of a system that cannot be inferred from the components of the system

quorum sensing

process in which bacteria monitor their own population density by sensing levels of signal molecules released

burst

microorganisms in a hypotonic solution . . .

shrink

microorganisms in a hypertonic solution . . .

osmophiles

microorganisms that grow best in or on media of high concentration solutes

halophile

microorganism that requires high levels of NaCl for growth

osmotolerant

organisms that grow over a fairly wide range of solute concentration

xerotolerant

microorganism that grows best under low water activity

cardinal temperatures

minimum, maximum, and optimum temperatures for growth

psychrotolerant

microorganism that has a growth optimum between 20°C and 30°C; a maximum of ~45°C or lower

psychrophile

microorganism that has an optimum growth temperature of 15°C or lower and a temp. maximum of 20°C

• grow well in refrigerated foods

Mesophile

microorganism that grow well in 20°C to 45°C

thermophile

microorganisms that have a growth optimum of 55°C or higher

obligate aerobes

require oxygen for growth and die without it

facultative anaerobes

do not require oxygen to grow, but grow better in its presence

aerotolerant anaerobes

microbes that grow equally well whether or not oxygen is present

obligate anaerobes

microorganisms that cannot tolerate oxygen and die when exposed to it

barotolerant

grow and reproduce at high pressures but do not require them

piezophilic

microorganism that prefer or require high pressure for growth

ionizing radiation

most harmful EM radiation to cells; very short wavelength, but high energy that cause atoms to lose electrons

oligotrophic

environments that have a low supply in nutrients

eutrophic

environments that have a high supply of nutrients