Reproduction in Bacteria

Bacteria utilize two main methods of reproduction: asexual and sexual reproduction.

Asexual reproduction occurs through binary fission, where bacteria divide into two identical cells. Bacteria do not undergo mitosis, but rather replicate their DNA, separate their chromosomes, and form a transverse septum through inward plasma membrane pushing. The cell wall then grows inward to create two separate cells. The time period between each division is called the generation time, consisting of four phases: the lag phase with no growth, the log phase with rapid growth, the stationary phase where the rate of death and reproduction is equal, and the death phase where bacteria begin to die. Under optimal conditions, bacteria can divide quickly, taking only 20 minutes for daughter cells to grow and divide again.

               Binary fission in bacteria

On the other hand, sexual reproduction in bacteria occurs through genetic recombination, where two bacteria's DNA combine to form a new type of bacteria, called a recombinant. This genetic recombination can occur through conjugation, transduction, and transformation.

The genetic recombination in bacteria was first indirectly proven through the experiments of J. Lederberg and EL. Tatum in 1946. They irradiated wild-type E. coli bacteria and obtained two types of nutritional mutants. When the mixed cultures of these two mutants were grown, three types of bacteria were obtained, including one that was similar to the parent strains and one that was like the wild type. From this experiment, it was concluded that the offspring of the two mutant types were wild type and that genetic recombination must have taken place.

The direct proof of genetic recombination was later obtained through electron microscopy. The method of gene transfer in bacteria occurs through bacterial conjugation, which involves the F-plasmid that can transfer during the conjugation process. The F-plasmid forms a conjugation bridge connecting the donor and recipient bacterial cells and transfers a copy to the recipient cell.

                   Sexual reproduction in bacteria by forming Conjugation Bridge