Bacteria are a generic name for a large part of microorganisms. Depending on their type, batteria may have a variety of forms and a wide range of shapes.
Bacteria are present in most of the habitats of the earth, from the soil from live bodies of animals and plants.
The scientists discovered over 40 million of bacterial cells in a gram of soil and over 1 million in a milliliter of fresh water and in the human body there are approximately over 10 times more bacteria than human cells. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and a few are beneficial. However, a few species of bacteria cause infectious diseases. The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people a year.
In the biological communities bacteria provide the nutrients needed to sustain life by converting dissolved compounds such as hydrogen sulphide and methane.
Most bacteria have a single circular chromosome and as asexual organisms, inherit identical copies of their parent’s genes. Some bacteria also transfer genetic material between cells. Despite their apparent simplicity, bacteria can form complex associations with other organisms. These associations can be divided into:
- Parasitism – the parasite, benefits at the expense of the host;
- Mutualism – both parasite and the host benefit from each other;
- Commensalism – either parasite or host benefits, but the other is neutral- there is no harm or benefit.
Due to their small size, common bacteria grow on animals and plants exactly as they will grow on any other surface. However, their growth can be increased by environment (as warmth and sweat.
Some bacteria are used in food industry and the most common is “lactic acid bacteria”, which is used in the preparation of fermented food, such as cheese, pickles, wine or yoghurt.