Microbial Growth Flashcards
what is the bacterial cell cycle?
the sequence of events from the formation of a new cell through the next cell division
how do bacteria replicate?
through binary fission
what are the 3 phases of the bacterial cell cycle?
- period of growth after the cell is born
- chromosome replication and partitioning
- cytokenesis
what are the 5 stages of binary fission?
- cell at early phase of life cycle
- chromosome replication; prep for division by enlarging cell wall, plasma membrane, and overall volume
- septum grows inward as chromosomes move toward opposite ends of cell; distribute cytoplasmic components
- septum synthesized completely through cell center, creating two separate cell chambers
- division
describe most bacterial chromosomes
singular, circular chromosome
how many replication origins do bacteria have?
just one
what is the single origin of replication in a bacterial cell?
site at which replication begins
what is the terminus in bacterial cells?
site at which replication is terminated, located opposite of the origin
what is the replisome of bacterial cells?
group of proteins needed for DNA synthesis
in what direction does DNA synthesis proceed?
in BOTH directions from the origin of replication
where do the origins of replication move to in microbial replication?
opposite ends of cell
what is septation also known as?
cytokinesis
when does septation begin?
when the z ring forms
describe septation in terms of the Z ring and MinCD
MinCD is a protein that oscillates back and forth across the bacteral cell, and keep the Z ring from forming until the cell is long enough that it takes too much time to go from one end of the cell to another, thus allowing the Z ring to form one the cell is ready for septation
what is septation?
formation of the cross wall between two daughter cells
what are the 4 steps of septation?
- selection of site for septum formation
- assembly of Z ring
- assembly of cell-wall synthesizing machinery
- constriction of cell and septum formation
what protein is the Z ring composed of?
FtsZ
what part of the bacterial life cycle do a lot of antibiotics target?
cell growth and division
what is important to take away from the super complex process of septation?
that you can attack steps along the way to treat infection
when does Z ring formation occur?
after replication of genetic material
is FtsZ the only protein involved in Z ring formation?
no there are others involved, but don’t worry about it
what must be synthesized as cells divide?
peptidoglycan!!
what is cellular growth?
increase in cellular constituents
what 2 things could cellular growth result in?
- increase in cell number
2. increase in cell size
what does cellular growth refer to?
population growth rather than growth of individual cells
when is the microbial growth curve observed?
when microorganisms are cultivated in batch culture
how is the microbial growth curve plotted?
as the logarithm of cell number versus time
what are the 5 distinct phases of the microbial growth curve?
- lag phase
- log phase
- stationary phase
- death phase
- long-term stationary phase
what happens in the lag phase of microbial growth curve?
cell is synthesizing new components
give two reasons why the cell would need to synthesize new components in the lag phase of the microbial growth curve
- to replenish spent material
2. to adapt to new medium or other conditions
how long is the lag phase?
varies in length, can be very short or even absent
what is the log phase of the microbial growth curve also called?
exponential phase
describe rate of growth in the log phase of the microbial growth curve
constant and maxmal
describe the microbial population in the log phase of the microbial growth curve
uniform in terms of chemical and physical properties
describe the stationary phase of the microbial growth curve
closed system population growth eventually ceases; total number of viable cells remains constant
what cancels out during the stationary phase of the microbial growth curve?
cell death = cell growth
what may happen to the population in the stationary phase of the microbial growth curve?
population may cease to divide, but remain metabolically active
what are the 4 possible reasons for the stationary phase of the microbial growth curve?
- nutrient limitation
- limited oxygen availability
- toxic waste accumulation
- critical population density reached
what is the stationary phase of the microbial growth curve also called?
holding pattern/plateau
what is the death phase of the microbial growth curve?
when the number of viable cells declines exponentially, with cells dying at a constant rate
what happens during the death phase of the microbial growth curve in terms of the environment?
detrimental environmental changes cause irreparable harm to the cells
list and describe 2 hypotheses for why the death phase occurs
- cells are viable but not culturable (VBNC): cells alive, but dormant, capable of new growth when conditions are right
- programmed cell death: fraction of the population genetically programmed to die (commit suicide)
what happens in the long-term stationary phase of the microbial growth curve?
bacterial population continually evolves
what is the long-term stationary phase of the microbial growth curve marked by?
successive waves of genetically distinct variants
what occurs during the long-term stationary phase of the microbial growth curve?
natural selection
