Bacterial Growth Flashcards
Orderly increase of all the chemical constituents
Growth
The increase in the number of microbial cells in a population.
Bacterial growth
The change in cell number or cell mass per unit tie.
Growth rate
Pattern of population increase
Exponential growth
Th time interval for the formation of two daughter cell from one.
Generation time
How do bacteria reproduce?
- Binary fission
- Budding (Asexual reprodution)
- Fragmentation
- Spore formation
Phases of bacterial growth curve?
- Lag phase
- Log phase
- Stationary phase
- Death phase or decline phase
It is the time period in which bacteria is metabolically active but do not divide is called?
Lag phase
During this phase bacteria divides continuously at constant rate and the number of bacteria increase exponentially.
Log phase
The bacteria reaches a state during which there is no net increase in bacterial population
Stationary phase
In this phase, the number of bacteria decrease continuously exponentially.
Death phase or decline phase
Bacteria have the maximum cell size towards the end of the lag phase.
Lag phase
Cells are smaller and stain uniformly in the log phase
Log phase
- Cells frequently are Gram variable and show irregular staining due to the presence of intracellular storage granules.
- Sporulation also occurs at this stage
Stationary phase
Involution forms are common
Decline phase
The time interval required for the cells (or population) to divide.
Generation time
Time interval in hours or minutes?
t
Number of bacteria at the beginning of a time interval
B
Number of bacteria at the end of the time interval?
b
Number of generations (number of times the cell population doubles during the time interval)
n
Equation is an expression of growth by binary fission
Bx2n
A measured volume of a bacterial suspension is placed within a defined area on a microscope slide.
Direct Microscopic Count
For longer eukaryotic microorganisms
Hemocytometer
For bacteria?
Petroff-Hausser Counting Chamber
Electronic counting chambers count numbers and measured size distribution of cells.
Electronic count
It gives accurate results with larger cells; not useful in counting bacteria
Coulter counter
It measures the number of living cells, cells capable of multiplication.
Viable counts
Involve plating out (spreading) a sample of a culture on a nutrient agar surface.
Plating Techniques
Each colony that can be counted in Plating Technique is called?
Colony Forming Unit (CFU)
This employ a variety of instruments to determine the amount of light scattered by a suspension of cells.
Turbidity Measurements
More rapid; sensitive technique; measures absorbance units
Spectrophotometry
- For cells growing in liquid samples
- Useful technique for measuring the growth of fungi
Microbial Dry Weight Determination
The total quantity of the cell constituent is directly related to the total microbial cell mass
Determination/Analysis of Cell Constituent
- A microbial culture that contains cells that are in the same growth stage
- Extensively used to address questions regarding cell cycle and growth
Synchronous culture of bacteria
A hypothetical situation in which the number of cells in a culture would increase in a stair-step pattern, dividing together at the same time.
Synchronous growth
A natural situation in which an actual culture has cell dividing at one rate and other cells dividing at a lightly slower rate.
Nonsynchronous growth
