What are bacteria, where do they come from, how to they interact with us? All extremely valid questions. When the Earth formed 4.6 billion years ago, the environment was far too hostile for any life to form. But as the Earth cooled it is hypothesised and theorised, although nobody will ever know the answer, that life formed from the primordial soup that was flowing on the Earth’s surface. How did this happen? Again, it can only be surmised that a chemical explosion occurred which brought together vital elements that fused to form life.
Scientists in the 1950s conducted experiments which combined heated water, air and electricity to mimic conditions thought to exist when the Earth was cooling. The experiment concluded with the production of 5 amino acids, the building blocks of proteins and life. In 2008 a similar experiment was undertaken, but this time a further element was introduced, steam. These conditions were thought to mimic volcanoes erupting. The experiment resulted in the synthesis of 22 amino acids.
During pre-life did the amino acids form proteins, did the proteins combine to form life?
It is thought that microbes have been around for 3.8 billion years and further life such as plants developed from the fusion of amoeba and cyanobacteria 1.9 billion years ago. Multicellular organisms are thought to have developed 630 million years ago. Organisms made the transition from sea to land 3.2 billion years ago.
Some scientist believe that life existed on Mars, many billions of years ago and came to Earth by way of meteorites and fused with terrestrial proteins to form life. Did we really come from Mars? We will never know.
There are obviously many other beliefs as to our existence, such as creationism, but this article is concentrating on the background to bacteria and their impact on human life, rather that look at the background to human existence, that is a topic for another article!
Some scientists believe that all life developed from bacteria, with fusion and mutation continually playing vital roles in the evolutionary process. They have reached this conclusion due the remarkable similarity between cells and cellular processes in bacteria, plants and animals. The tree of life splits all living organisms into 3 groups:
Bacteria
Archaea
Eukarya
There are more microbes than stars in the universe, so it has been suggested. Bacteria are ubiquitous, they are found in and on humans, in the soil, water and atmosphere. Dust clouds contain many species of bacteria and viral particles responsible for causing diseases such as meningitis, coral farm disease, pneumonia, septic shock, inflammation of the heart, sars, influenza, valley fever and foot and mouth.
Whenever you are ready to take a shower, let it run for a minute before stepping in or risk getting a face full of bacteria. Scientists have found large numbers of Mycobacterium avium in the shower faucets. These bacteria cause respiratory diseases similar to TB. Two other strains of these bacteria actually cause TB and leprosy.
Any microbe responsible for causing disease is termed a pathogen. There are, however, more beneficial micro-organisms than pathogens. In fact without certain species we would die. Humans are caked in bacteria, which keeps inflammation in check, which can be caused by injury and pathogens. Staphylococcus aureus are commensal bacteria which are part of the natural micro-flora of humans (and other animals). Any microbes which are not part of our natural flora are called transients.
S aureus releases molecules which prevent skin cells from releasing chemicals that cause the inflammatory response. Although the inflammatory response is crucial to aid recovery from injury, too much, prolonged inflammation can cause skin diseases such as psoriasis.
We, along with other species, possess vast amounts of symbiotic bacteria in and on our body. Our skin, for example, is home to over 180 different species of bacteria and fungi. The majority of skin micro-flora is concentrated around our sweat glands, such as the underarms, genitalia, nipples and navel. Half of all these bacteria mainly belong to the genera Streptococcus, Corynebacterium, Staphylococcus and Propionibacterium (a species of which causes acne).
There are 17 known genera of bacteria known to belong to the Bacterial Phylogenic Tree. Each genus (genera = plural) can have many different species. Salmonella is a genus; there are over 2,500 known species of Salmonella.
The amount of bacteria present on the skin depends on several factors including the weather, age of host (young children harbour more bacteria, especially pathogens, than adults) and personal hygiene.
The mouth does not harbour any micro-flora, due to the anti-bacterial qualities of lysozyme, a constituent of saliva. However, if one has poor dental hygiene, allowing the build up of plaque, then transient bacteria can inhabit and grow. Plaque is a very good growth medium for several different genera of bacteria, causing such disorders as dental caries, gingivitis and periodontal disease.
The gastrointestinal tract (GI) is a single long tube running from the mouth to the anus. It starts at the oesophagus, which is inhabited by microflora. Between the oesophagus and anus there are up to 30 different species of bacteria present. Some studies have shown a bacteria cell count of 10 the power of 14 in the GI tract. That is a lot of bacteria, considering that 10 to the power of 6 is a million!
The bacteria are responsible for:
o steroid metabolism (modifying steroids released from the gall bladder after synthesis in the liver. The modified steroids are then absorbed by the gut)
o synthesis of vitamins such as B1, B2, B6, B12 and K
o breakdown of fibre (the digestible elements)
o production of gas such as methane, hydrogen and carbon dioxide.
Without bacteria present, we would not be able to digest food.
The upper respiratory tract (sinuses – larynx) of a healthy individual harbour many micro-flora. The lower respiratory tract (trachea – lungs) should contain few, if any.
The uro genital tract in both male and females contain a few resident bacteria. Urine is held in a sterile environment in the bladder. The bacteria inhabit the urethra. One such species, Lactobacillus acidophilus, is a resident of the vagina, where it ferments glycogen, releasing lactic acid. The acidic condition prevents disease, caused by pathogens, which do not like an acidic environment, from developing.
