Microbial growth curves Flashcards
(10 cards)
The portion of the growth curve where rapid growth of bacteria is observed is known as ____________
a) Lag phase
b) Logarithmic phase
c) Stationary phase
d) Decline phase
Logarithmic phase
Explanation: A typical growth curve has four regions. An initial period of no growth known as the lag phase, followed by rapid growth known as logarithmic phase. No growth is observed in the stationary phase and death phase.
The growth of bacterial population follows a geometric progression.
a) True
b) False
True
Explanation: The bacteria show growth by following binary fission as means of reproduction. Thus, if we start with a single bacterium, the increase in population is by geometric progression.
In the growth equation: n = 3.3 (log10 N – log10 No), n stands for ____________
a) total population
b) initial population
c) number of generations
d) growth constant
number of generations
Explanation: In the above formula, n stands for the number of generations that have taken place after the growth.
Lag phase is also known as ___________
a) period of initial adjustment
b) transitional period
c) generation time
d) period of rapid growth
period of initial adjustment
Explanation: In the lag phase, the bacteria maybe deficient in enzymes or coenzymes which must first be synthesized and thus time is required for adjustments in the physical environment. So it is also known as a period of initial adjustment.
The generation time for E.coli is ________
a) 20 minutes
b) 35 minutes
c) 2 minutes
d) 13 minutes
20 minutes
Explanation: The generation time for E.coli at a temperature of 37 degrees Celsius lies in the range of 15-20 minutes generally.
During exponential phase, growth rate is _______
a) same as generation time
b) reciprocal of generation time
c) time required for population to double
d) rate of doubling population
reciprocal of generation time
Explanation: During exponential growth, the growth rate (R) i.e., the number of generations per hour, is the reciprocal of the generation time g. Growth rate is the slope of the straight line obtained when the log number of cells is plotted against time.
In which of the following phase secondary metabolites are produced during growth?
a) Lag phase
b) Log/Exponential phase
c) Stationary phase
d) Death phase
Stationary phase
Explanation: During the stationary phase, there is complete utilization of the nutrients present in media and thus produce secondary metabolites which are then used in different industries.
Which phase shows the reproduction rate equal to the equivalent death rate?
a) Log phase
b) Stationary phase
c) Death phase
d) Lag phase
Stationary phase
Explanation: In the stationary phase there is a complete cessation of division and thus the reproduction rate is balanced by an equivalent death rate.
Which of the following is used to grow bacterial culture continuously?
a) Chemostat
b) Hemostat
c) Coulter-Counter
d) Turbidostat
Chemostat
Explanation: Chemostat is used for continuous cultivation. This system depends on the fact that the concentration of an essential nutrient within the culture vessel will control the growth rate of the cells
The average size of the cells in the exponential phase is ___________
a) larger than the initial size
b) smaller than the initial size
c) equal to the initial size
d) maybe smaller or larger than the initial size
smaller than the initial size
Explanation: During the exponential phase, the cells divide steadily at a constant rate and thus give a straight line. So the average size of cells goes on decreasing than the initial size due to binary fission.
