Binary fission, sporulation and sexual reproduction are three main phases of reproduction in bacteria.
Binary Fission is the most common method of reproduction. A mature bacterium divides into two equal parts. It is quite similar to amitosis. In this chromosomes divide when they are attached to mesosome. After the division a new mesosome is formed. Each bacterial cell is able to undergo binary fission after 20 minutes. If this process continues it will produce 4.7 x 10 raise to power 21 bacteria within 24 hours. So bacteria they give rise to more daughter cells and this process goes on and on and one can say bacteria are immortal. But they are quite sensitive to temperature changes, food scarcity, and presence of waste products.
In sporulation many types of spores are produced which include gonidia, sporangiospores, cysts and endospores. Endospores are resistant and thick walled spores which are formed when the conditions are not favorable for bacteria such as extreme changes in temperature, food shortage and collection of waste products. As a result of this protoplast undergoes dehydration and separates by mesosome and is referred as Endospore Primordium. The resistant nature of endospores is mainly attributed by dipiclonic acid. Bacilli and clostridium are two species which produces endospores.
Sexual reproduction in bacteria
A typical sexual reproduction is absent in bacteria. As there is no gamete formation and there is no meiosis. However, gene recombination occurs which leads to certain processes such as conjugation, transformation and transduction.
Conjugation was discovered by Lederberg and Tatum in 1946 in Escherichia Coli. In this cell contact is required. It was observed under electron microscope. Bacteria featuring in this process must be dimorphic.
Dimorphic means with two type of cells that is male/ female or donor/ recipient. The male cell possesses single to multiple pili and a fertility factor. A female cell possesses no sex pili and fertility factor. Gene exchange in conjugation occurs by Sterile male method and Fertile male method. In sterile method the plasmid with fertility factor multiplies and is transferred to the recipient cell. The recipient cell can become donor. This phenomenon of interchangeability is referred to Sexduction. In fertile method the fertility factor gets associated with chromosome. This type of plasmid which can be attached is referred as episome. In this a recipient cell cannot become donor and vice a versa. Basically, in conjugation an incomplete diploid known as Monozygote is formed.
Transformation is the intake of DNA from the neighboring medium by living bacterium. This was discovered by Griffith in early 20th century.
Zinder and Lederberg discovered Transduction. It is defined as a method of transfer of foreign genes by viruses. If the genes are same they are referred as restricted transduction. If the genes are different they are referred as generalized transduction
