Types of Bacteria

Bacteria are microscopic organisms which are made up of single cells. They come in different sizes and shapes, but the sizes do not exceed a micro-meter. Bacteria survive in all types of conditions, multiply very fast and fall into different categories. There are those which are harmful and others which are not, but it is sometimes not very easy to tell the difference. 

Long ago, bacteria were classified according to their shapes, but with the advancement in technology, it is now easy to tell them apart using other criteria. The most commonly used approach is the DNA sequencing, which not only help in the classification, but also in establishing the relation between one bacterium and another. Other criteria used in the classification of bacteria into the different types are their metabolic activities, biochemical reactions and the conditions required for their growth and survival.


ome of the types of bacteria that exist today are the autotrophic and heterotrophic types. They are classified according to their requirements for survival. The autotrophic bacteria require carbon to survive, which it obtains from carbon dioxide available in the atmosphere. They also require direct sunlight to produce sugar for their survival.

The heterotrophic bacteria obtain carbon from the host organism in which they live. They also do not make their own sugar and rely on the host to obtain it. They are commonly found in the living cells of many organisms. Another classification that is closely related to this one is the aerobic and the anaerobic bacteria. The aerobic class of bacteria requires oxygen for survival, while the anaerobic ones do not. The anaerobic ones can survive in environments under the surface of the earth and in deep sea.