microbial growth lesson 10

bacterial cell cycle

involves the formation of new cells through the replication of dna and partitioning of cellular components into two daughter cells

borella burgdorferi

positive agent of lyme disease, has a linear chromosome

binary fission

the most common mechanism of cell replication in bacteria

binary fission

before dividing, cell grows and increases its number of cellular components

ftsZ

a protein that directs the process of cytokinesis and cell division

divisome

it is formed when additional proteins is required for cell division and added to the z ring

divisome

it activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells

generation time

the time between the same points of the life cycle in two successive generations

doubling time

generation time in prokaryotes and is defined as a time it takes for the population to double through one round of binary fission

escherichia coli

can double in as little as 20 minutes under optimal growth conditions in the laboratory, bacteria of the same species may need several days to double in especially harsh environments

mycobacterium tuberculosis

the causative agent of tuberculosis which has a generation time of between 15 and 20 hours

M.leprae

causes hansense disease or leprosy which grows much more slowly, with a doubling time of 14 days

culture density

defined as the number of cells per unit volume

culture density

also a measure of the number of cells in the population

log phase

exponential increase in number of living bacterial cells

stationary phase

plateau in number of living bacterial cells; rate of cell division and death roughly equal

death or decline phase

exponential decrease in number of living bacterial cells

lag phase

no increase in number of living bacterial cells

lag phase

the beginning of the growth curve represents a small number of cells, referred to as an inoculum, that are added to a fresh culture medium, a nutritional broth that supports growth

lag phase

the initial phase of the growth curve

logarithmic growth phase

sometimes called exponential growth phase where cells are actively dividing by binary fission and their number increases exponentially

log phase

during this phase, the relationship between time and number of cells is not linear but exponential

log phase

stage where bacteria are the most susceptible to the action of disinfectants and common antibiotics that affect protein, dna, and cell wall synthesis

stationary phase

during this phase, cells switch to a survival mode of metabolism

persister cells

are medically important because they're associated with certain chronic infections such as tuberculosis, that do not respond to antibiotic treatment

chemostat

used to maintain a continuous culture in which nutrients are supplied at the steady rate

chemostat

a culture vessel fitted with an opening to add nutrients (feed) and an outlet to remove contents (effluent), effectively dilutin toxic waste and dead cells

binary fission

the most common pattern of cell division in prokaryotes

fragmentation

commonly observed in the actinomycetes, a group of gram positive anaerobic bacteria commonly found in soil

actinomycetes

a group of gram positive, anaerobic bacteria commonly found in soil

budding

most common in yeast, but it is also observed in prosthecate bacteria and some cyanobacteria

actinomyces

result bacteria which grow in long filaments divided by septa, similar to the mycelia seen in fungi, resulting in long cells with multiple nucleoids