devision Flashcards
what is the most common way bacteria devide
binary fission
how do bacteria divide
binary fission
what is binary fission
1 cell becomes 2 cells (2=sizes)
what type of bacteria devide by budding
planctomycetes
the cell cycle of a bacteria
-chromosome replication
-elonglation
-segregation
-z ring formation
-division
you observe a ghost cell in your bacteria culture. what is the best explanation
the z-ring is formed prior to segregation during the cell devision cycle
what is a ghost cell
cell with out chromosomes
what is biofilm
-from free-living planktonic to attached community
-4 key steps
-not a target of antibiotics
-several regulators and environmental factors
four key steps for biofilm formation
-attachement
-growth
-maturation
-detachment
you work in the food industry and bio films are a major problem. you must keep surfaces free of bacterial contamination. what step of biofilm formation should you target
attachment
quantifying growth of cells
each division adds two new cells
0 generation=1 cell
1 gen=2cells
2gen=4cells
3gen=8cells
what division would result in doubling of the population
budding
how to direct count using microscopy
-grid
-count cells in square
-challenges: dont know if bacteria is dead and could count dead ones
-if mobile they are hard to count
how to direct count using current
-coulter counter
-measure electrical current
-downside is you cant distinguish dead form alive
direct counting methods
coulter counter
microsopy
viable counting methods
-dilution
-plating
plating for counting bacteria
2 methods
-1)pour plate method
-bacteria sample mixed with warm agar
-sample poured onto sterile plate
-swirled around to mix, allowed to solidify
-plate incubated until colonies grow
-2) spread plate method
-sample (0.1mL) poured onto solid medium
-spread sample evenly over surface
-plate incubated until bacterial colonies grow in the surface of the medium
most probable number
-inoculate 3 different volumes of water in test tube and see what comes back positive
-see if high number of coliforms
-due to fecal contamination
-which ferments lactose
-determines if water is safe
turbidimetric
-measuring bacteria using optical density
which method would be used to measure the concentration of bacterial contamination in processed BP
-total plate count
-gives you direct count and BP wont interfere
how does bacteria grow
-predictably
-lag phase (no increase in number of living cells)
-log phase (exponential increase in number of living bacterial cells)
-stationary phase (plateau in number of living bacterial cells; rate of devision and death roughly equal
-death or decline phase (exponential decrease in number of living bacterial cells)
during which phase of growth would antibiotics be most effective
log/exponential phase
generation time
how long does it take one to become two, time for population to double
if you start a bacterial culture with one bacterial cell, how many cells would be expected after 12 hours the generation time is one hour
2^12
4096
