CHAPTER 2: Lesson 9: Principles of Bacterial Growth Flashcards
It refers to increase in number of cells and not the
size of cells.
Bacterial/microbial growth
Most bacteria divide by _________ in which the bacteria undergo
asexual cell division to produce two daughter cells genetically identical to the parent
cell.
binary fission
It begins with DNA replication and
segregation
of
nucleoids
(distribution between the future
daughter cells); next, a Z-ring
composed
mainly
of
FtsZ
polymers is assembled in the
middle of the cell. Finally, the Zring recruits additional proteins
that serve for septum formation
and subsequent separation of the
daughter cells.
Cell division
It is the time required for a bacterium to give rise to two
daughter cells under optimum conditions.
Generation time
generation time
for most of the pathogenic bacteria, such as E. coli, is about ________, in about ________ can undergo 20 generations and produce 1 million cells, and in ________
produces 10²¹ cells
20 minutes
7
hours
24 hours
Microbial concentrations can be measured in terms of the following:
(i) cell concentration
(ii) biomass concentration
It is the number of viable cells per unit volume of culture.
cell concentration
Dry weight of cells per unit volume of culture.
biomass concentration
The number of bacteria at a given time can be estimated by ___________.
performing a total
count or viable count
It denotes the total number of bacteria in the sample, irrespective
of whether they are living or dead.
Total count
This is done by counting the bacteria under the
microscope using counting chamber or by comparing the growth with standard
opacity tubes.
Total count
It indicates the number of living or viable bacteria.
Viable count
This count can
be obtained by dilution method (series of sequential dilutions used to reduce a dense
culture of cells to a more usable concentration) or plating method (number of
colonies that grow after a suitable incubation time).
Viable count
Series of sequential dilutions used to reduce a dense
culture of cells to a more usable concentration.
dilution method
number of
colonies that grow after a suitable incubation time
Plating method
It represents the number of live cells in a bacterial
population over a period of time.
bacterial growth curve
Four phases of growth curve
- Lag phase
- Log phase
- Stationary phase
- Decline phase
The time between inoculation and beginning of multiplication is
known.
Lag phase
In this phase, the inoculated bacteria become
acclimatized to the environment, switch on various enzymes, and adjust to the
environmental temperature and atmospheric conditions.
Lag phase
During this phase,
there is an increase in size of bacteria but no appreciable increase in number
of bacterial cells.
Lag phase
The cells are active metabolically.
Lag phase
This phase is characterized by rapid exponential cell growth of
bacteria at their maximum rate.
Log phase
The bacterial cells are small and uniformly
stained.
Log phase
The microbes are sensitive to adverse conditions, such as antibiotics
and other antimicrobial agents
Log phase
