(6) Microbial Growth Flashcards
mention some parameters of growth in microbial growth
increase in number of microbial cells, increase in microbial mass, refers to population
what microorganism use binary fission to reproduce
amoeba, bacteria
what microorganism use budding to reproduce
bacteria, yeast, corals,flatworms
define binary fission
binary fission is an asexual reproduction where a parent cell splits into two daughter cells
define budding
budding is an asexual reproduction where a new organism develops from a bud of its parent organism
define multicellular
composed of more than once cell, with groups of cell differentiating and taking specialized functions
define unicellular
made up of only one cell that carries out all function needed by the organism
are algae and mold unicellular or multicellular
multicellular
what is mycellium
a root-like structure of a fungus consisting of a mass brancing, thread-like hyphae
what is hyphae
the long filamentous branching in fungus and actinobacteria
where does the hyphae growth takes place
the apical zone (at the very tip. the cell wall extends and produce long hyphal tube)
how to write microbial growth population
in one decimal (1 000 000= 1x10^6)
what’s the limit of bacteria in fresh milk?
10^5 cell/mL
what are the 4 stages in microbial growth curve
lag phase, exponential phase, stationary phase and death phase
explain lag phase
when microbial population is inoculated into fresh medium. there are cellular activity but no growth. cells grow in size but no cell division.
explain exponential phase
when the cells starts dividing in an logarithmic way. reproduction is high during this period. cells are active metabolically.
explain stationary phase
exponential growth ceases. available nutrients are all used up and waste product starts to accumulate. no growth occurs. number of cell death equals to number of cell divisions.
explain death phase
number of living cells decreases exponentially. population growth declines. number of cell death exceeds cell division.
in what phase do bacteria starts to synthesize nutrients and prepare for cell division?
lag phase
define growth rate in microbial kinetics
change in cell number/mass per unit time
define generation in microbial genetics
interval for formation of two cells from one
define generation time (doubling time)=G
the time required for formation of two cells
what is the formula of G (generation time)?
G= t/n
t= time interval in hours or minutes
n= number of generation
whats the formula to calculate the size of a population (n) over time
for binary fission
n= log X - log Xt/log 2
Exercise: At initial time the number of bacteria is 10^3. After 5 h the number of bacteria is 10^7.
Calculate number of doubling (n) and the
generation time (G).
n = log Xt- log X/log2
n = log 10^7 - log 10^3/log2
n = 7- 3/0.301
n = 13.3
G=t/n
G=5/13.3=0.375 h
G=22.56 min
how to directly measure cell number?
viable count, membrane filtration, direct microscopic counts
how to indirectly measure cell mass?
turbidimetry
how to measure cell mass?
dry weight
explain what and how viable count method
viable count is determining the number of cells forming colonies.
method: spread plate, pour plate
what is filtration method
measuring from the colony that is present on the plate or filter. it only countrs live cells.
what and how to do direct microscopic count
a method to estimate microbial cell number. requires microscope, special slides, high power objective lens.
how: counting total microbe numbers one by one.
what is turbidity measurement
method used to follow the rate of growth of the culture. uses spectrophotometer to send a visible light through the culture and measure how much light is scattered.
in statonary phase, bacteria produces…
toxins, antibiotics and secondary metabollites
in death phase, the total count of cell
decreases
