Short essay on Reproduction of Bacteria

Asexual reproduction is of general occurrence in the bacteria. Sexual reproduction involves exchange of genetic material.

A. Asexual reproduction

It takes place under suitable conditions of the environment; i.e. when there is plenty of nutrient supply and temperature, moisture conditions are congenial. Asexual reproduction may be vegetative or by sporulation.

1. Vegetative Reproduction

Most common type of this method of reproduction is by fission.

a. Fission – In this method, a single mother cell becomes equally divided into two or more daughter cells. When two identical cells are formed from a single cell, it is called binary fission.

The fission includes the following steps. (l) Division of the nuclear material by a process analogous to mitosis. (2) Separation of cytoplasm into two equal parts (3) Formation of septum or cross walls (4) Separation of sister cells.

Fission in bacteria under suitable conditions can takes place in every 15 to 20 minutes. A large number of cells can easily be formed by this method in a short span of time.

b. Budding – Certain rod shaped bacteria grow at one end by forming buds which later on separates into independent organisms here; nuclear material may be equally or partially transferred to the budding cell. The bud when attached to the mother cell may form a bud so that chains of buds may appear.

c. Segmentation – Some species of bacteria reproduce by the process called segmentation. The protoplast of the bacterial body divides to form very tiny bodies called gonidia. The cell wall ruptures and the gonidia are liberated to form new individuals.

2. Sporulation in bacteria

Bacteria may reproduce by spores, which are of two kinds, namely conidia and endosperms.

(a) Conidia – A certain bacteria like Streptomycin cuts off tiny, oval or rounded, non motile structures called conidia in chains. These are borne at the tips of special aerial branches called conidiophores. Each conidium under suitable conditions germinates into new bacterium.

(b) Endospores – These are highly resistant, physiologically dormant, single celled bodies formed inside the bacterium mother cell. In form the endospores may be spherical or elliptical, rarely cylindrical and may be central, terminal or sub terminal in position in the sporangium.

The diameter of the end spore may be slightly less than that of the rest of the parent cell. The process of end spore formation involves the condensation of a part of the protoplast of the cell. A small, clear area of denser materials in the granular cytoplasm towards one end or centre of the cell appears.

It may be elliptical or rounded and is called spore primordial. A short length of chromatin network moves into it. The spore primordial, then gradually increases in size. Soon after, the spore wall and spore coat develop. During the final stage which may extend over several hours, the spore changes in size and form and becomes an endospore.

The parent cell is called sporangium. At maturity, when cell contents around the endospore disintegrate, endospores are liberated. Each endospore germinates into a new bacterium under suitable conditions.