How bacteria grow in number

Asexual reproduction in bacteria

Bacteria follow asexual means of reproduction by binary fission. The word binary means two and fission means breakdown, so in binary fission a cell breakdown into two cells. The mechanism of binary fission is that firstly the parent cell enlarges in size and then chromosome starts to duplicate, next to it plasma membrane moves toward the region where a chromosome duplicate into two at the center of the cell. When all the nuclear material of chromosomes has been equally distributed in both of duplicated parts the cell wall grows inward and completes the separation of bacteria into two well-developed cells.

At some intervals the each daughter cell duplicates at the sequence and cause to increase in a large number of population. Once the division is complete the bacteria grow and develop their unique features. The time interval at which bacteria complete its growth before next division is called generation time

There are four distinct phases are recognized in bacterial growth curve.

1.   Lag phase: 

It is the first phase of bacterial growth curve at which bacteria show no growth and just prepare themselves for division.

2.   Log phase:

    The second phase of bacterial growth curve, at which bacteria shows its maximum growth. Bacteria grow at fast speed at an exponential rate.

3.   Stationary phase:

    At this phase bacteria become mature enough to stop further growth and achieve its desire shape and size. Bacteria death rate is equal to rate of reproduction and multiplication.

4.   Death/Decline phase:

 At this phase bacteria start dying. Now the death rate is higher than reproduction rate.

Sexual reproduction in bacteria

Bacteria do not follow traditional mode of sexual reproduction and mitosis. Some bacteria reproduce sexually only by transfer their genetic material from donor to a recipient bacteria. Donor is one which transfers its genetic material to recipient bacteria which receive that genetic material. The process of transferring genetic process is called conjugation. Some bacteria transfer their genetic material by sex pili. As a result of conjugation new genetic combinations are produce that are more adaptive to survive in a variety of conditions. After every 20 minutes the number of bacteria become double and hence form large number of colonies under favorable conditions.