Growth of Bacteria | Microbiology -

Table Of Contents

Growth and Multiplication of Bacteria

Bacterial cell division- binary fission

Most bacteria divide by binary fission in which the bacteria undergo cell division to produce two daughter cells identical to the parent cell.Bacterial DNA/chromosome- circular double stranded DNA
Nuclear division followed by cell division.
During binary fission, Two identical double strand DNA are separated and distributed to the daughter cells.
Transverse septum grows across the cell from the cell membrane, followed by the deposition of cell wall material.
Finally to daughter cell separates.

Bacteria growth follows a defined course .i.e. growth curve obtained by plotting bacterial count vs time. The bacterial growth curve has four phases.

Lag Phase	Log phase	Stationary phase	Decline phase
-The period between inoculation and the beginning of multiplication is known as the lag phase. -In this phase, the organism adapts to the new environment. -During the lag phase, necessary enzymes, intermediate metabolites are built up in adequate quantity for multiplication to proceed/start. -Increase in size of a cell -Number of cells- not increase -Duration of phase depends on species, culture type and temperature. -At the end of the lag phase, the bacterium has maximum cell size.	-Cell division starts -A number of organism increase exponentially or by geometric progression with time. The straight curve between logarithm viable count versus time. -Cells are smaller and strain uniformly.	-After low phase bacterial growth ceases due to exhaustion of nutrient and accumulation of toxic products. -Number of progeny cell form is just enough to replace the number of cell that die. -Number of viable cells remain stationary as there is is almost balance between dying cell and new formed cell. -Cells are gram variable and show irregularity straining due to intracellular storage of granules. -Sporulation occurs -Many bacteria produce exotoxin this phase	-The stationary phase decline phase start due to exhaustion of nutrients accumulation of the toxic product and autolytic enzymes. -Bacterial population decline due to the death of cells. -Decline in viable count of the bacteria. -Involution forms are common.

The bacterial growth curve phases

Bacterial Growth Curve: Lag, Log, Stationary & Decline Phase

Period between inoculation and the beginning of multiplication is known as the lag phase.
In this phase, the organism adapts to the new environment.
During lag phase, necessary enzymes, intermediate metabolites are built up in adequate quantity for multiplication to proceed/start.
Increase in size of a cell
Number of cells- not increase
Duration of phase depends on species, culture type and temperature.
At the end of the lag phase, the bacterium has maximum cell size.

Cell division starts
A number of organism increase exponentially or by geometric progression with time.
The straight curve between logarithm viable count versus time.
Cells are smaller and strain uniformly.

After low phase bacterial growth ceases due to exhaustion of nutrient and accumulation of toxic products.
Number of progeny cell form is just enough to replace the number of cell that die.
Number of viable cells remain stationary as there is is almost balance between dying cell and new formed cell.
Cells are gram variable and show irregularity straining due to intracellular storage of granules.
Sporulation occurs
Many bacteria produce exotoxin this phase

Stationary phase decline phase start due to exhaustion of nutrients accumulation of the toxic product and autolytic enzymes.
Bacterial population decline due to the death of cells.
Decline in viable count of the bacteria.
Involution forms are common.

Time required for a bacterium to give rise to two daughter cells under optimum condition is known Generation time.
Generation time for most bacterium is 20 minutes
Mycobacterium tuberculosis 20 hrs
Mycobacterium lepre – 20 days

Stay updated with Pharmacy Previous Papers, Pharma Jobs, GPAT Notes, Study Materials, Admission Alerts & Pharma News.

Get instant updates on Pharmacy Previous Year Papers, Pharma Job Notifications, Study Materials, Admission Alerts and Pharma News.

Receive latest updates about Pharmacy Previous Papers, Pharma Jobs, GPAT Materials, Admissions, Notes and Pharma News.

Download FREE Books & Notes, D.Pharm, B.Pharm, M.Pharm, GPAT, Drug Inspector Previous Papers and much more.