Bacteria are widespread microscopic organisms that have single cells which do not have any membrane-bounded nucleus or membrane-bounded organelles. Common examples of membrane-bounded organelles are mitochondria and chloroplasts. Bacteria had been the primary form of life originating far more than 4 billion years ago on earth. These big groups of unicellular micro-organisms can have diverse shapes like spheres, spirals and even rods. They are just a couple of micrometers in length.

Bacteria are omnipresent in every environment, even on radioactive waste and in the bodies of animals. To give an indication of its quantity, there are nearly 40 million bacterial cells in a single gram of mud and approximately five nonillion (5×1030) bacteria are present on earth at any given point of time. The study and study of bacteria is called bacteriology which is a part of microbiology.

Antonie van Leeuwenhoek was the very first person to discover bacteria in 1676 when he employed a microscope (single-lens). This made him the world’s first microbiologist to accomplish this feat and he penned the name ‘animalcules’ for bacteria. An interesting piece of details is that singular form of bacteria is referred to as bacterium. The term bacterium was coined by Christian Gottfried Ehrenberg later in the 18 th century.

There are quite a few bacteria present in our body and they even manage to be on human skin. The human immune system is strong enough to stop the bacteria from damaging our bodies. Some sorts of the bacteria are useful to humans. Bacteria are known to attach to exterior surfaces and form thick aggregations recognized as ‘bacterial mats’. Length of these ‘bacterial mats’ can vary although some can be as lengthy as half a micrometer. Areas which have these bacterial mats can consist of many varieties of bacteria, archaea and protists or even all them combined.

Bacteria are known to trigger several diseases which can be as frequent as infections or deadly diseases like diphtheria, syphilis, cholera, typhoid fever, leprosy and even tuberculosis. Tuberculosis alone kills more than a million men and women all over the world but mostly in African and Asian countries.

Now on a positive side, bacteria aid in sewage treatment, cheese and yoghurt production via fermentation. Bacteria are really helpful in biotechnology, antibiotics and several other helpful chemicals. Popularity of bacteriology has paved way to research in many other fields related to it.