L6: Microbial Growth Flashcards
define microbial growth
an increase in the number of cells in a population
What are the steps to binary fission?
- DNA replicatees
- Cell elongates, chromosomes segregate
- septum forms between two daughter cells
- cell divides
What is the name of a key bacterial cytoskeletal protein in bacteria and archaea
FtsZ
What is FtsZ
homologue of eukaryotic protein tubulin
What is FtsZ required for?
cell division and septum formation
it forms contractile ring at midcell
Where does FtsZ’s energy come from
hydrolysis of GTP
population growth is studied by analyzing_____
growth curve
What circumstances are used to form a growth curve?
microbes cultivated in a batch culture (closed vessel, single batch of medium)
What happens in the lag phase of the growth curve?
no growth, cells synthesizing new components
What happens in the log phase of the growth curve?
cells divide, exponential increase
What happens in the stationary phase of the growth curve?
population growth ceases because as the pop grows, toxic byproducts of replication accumulate and begin killing cells
What are spores?
stress-resistant, dormant cells that may form in microbes under nutrient limiting conditions
What are 3 methods of measuring microbial growth
direct cell counts (counting chambers)
viable cell counts (plating, CFUs)
turbidity measurements (spectrophotometer)
What are biofilms
microbial communities that are attached to a surface and covered with a protective matrix
What are the 4 phases of biofilm growth?
attachment
colonization
maturation
dispersal
What is present during attachment of biofilms?
pili and adherence proteins
What is present during colonization of biofilms? What happens during this phase?
quorum sensing
cell-cell signaling
activates gene expression to make matrix of polysaccharides, protein, and DNA
What happens during maturation of biofilms?
mushroom forms with channels for nutrients and oxygen gradients
can be aerobic or anaerobic
What happens during dispersal of biofilms?
biofilm opens and planktonic cells are released
What is periodontal disease?
microbial infection with inflammation and tissue destruction
What is dental plaque?
microbial film on tooth surface
What are some environmental factors that can influence microbial growth?
oxygen concentration
temperature
solutes and water activity
pH
What are extremophiles?
microbes that grow in extremes environments
What are obligate aerobes?
microbes that need oxygen
