What are bacteria?
Bacteria are tiny single-cell microorganisms and are normally a few micrometers in length. They are neither plant nor animal, being a classification of their own, and usually exist together in millions.
Scientists now say that bacteria were the first life forms on Earth four billion years ago. It is believed that for the next three billion years all life forms on the planet were microscopic in size, dominated by bacteria and archaea (classified as bacteria, but genetically and metabolically different from all other known bacteria).
Bacteriologists say that bacteria are absolutely everywhere except for places that humans have sterilized. Bacteria can survive where no other organism can. Even the most unlikely places where temperatures may be extreme, or where there may be a high concentration of toxic chemicals have bacteria.
Indeed, it is certain that we would not have existed without them. The air we breathe - specifically the oxygen - was most probably created millions of years ago by the activity of bacteria.
Bacteria come in three main shapes:
- Spherical (like a ball) which are called cocci (singular coccus).
- The meningococcal bacteria which causes meningitis is a diplococcus - a pair of two joined cocci.
- Rod shaped known as bacilli (singular bacillus) or vibrio if curved. Spiral known as spirilla (singular spirillum) or spirochetes if their coil is very tight.
There are many variations within each shape group. Unlike the cells of a plant or animal, bacterial cells have no nucleus.
Bacteria reproduce through binary fission which is an asexual form of reproduction which doesn't involve a male and female. The cell continues growing and growing, eventually a new cell wall grows through the center forming two daughter cells, which eventually separate. Each daughter cell has the same genetic material as the parent cell.
The problem with binary fission is that every daughter cell is identical to the parent cell it came from, as well as all its sisters. This makes it harder for bacteria to survive, especially when attacked by antibiotics. To get around this, bacteria use a process called recombination.
The secrets of bacteria have slowly been discovered over the course of human existence - thousands of years ago it was suggested that something too small for the naked eye to see may be the cause of disease, and over the hundreds of years that followed various theories were given. It was not until 1676 that bacteria were properly identified as microorganisms.
Although they can also be dangerous, causing disease, bacteria also play a vital part in keeping all things alive.
Plants, for example, would not survive without bacteria - plants cannot extract nitrogen from the soil, so they benefit from the atmospheric nitrogen which is assimilated by bacteria and released when they die.
We need them too - the human body contains huge amounts of friendly bacteria that are beneficial, e.g. bacteria in the digestive system are essential for the breakdown of certain types of nutrients, such as complex sugars, into forms the body can use.
Friendly bacteria also protect us from pathogenic (disease-causing) bacteria by occupying places in the body where they live and some attack the pathogens.
Whilst acknowledging that bacteria, found in soil, water, plants and animals, have played their part in creating life on earth, it is also true that they have caused some of the most deadly diseases in human history, including the plague, cholera , pneumonia, tuberculosis and of course meningitis.
Despite this, as hygiene has improved over the past 100 years or so, the number of deaths from bacterial diseases has dropped significantly, particularly in developed countries. Vaccines and immunisation programmes have been developed and whilst still devastating, the dangerous effects of bacteria are constantly being hit by modern medicine.
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