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In the Fact File section we bring you a new collection of quick facts each week. (Click on the links below for more facts)


Special Microbe Fact File

2541/ There are more microbial cells in our bodies than there are human cells! In fact 95% of all the cells in the body are bacteria, mainly living in the digestive tract.

2542/ There are more bacteria in the colon than the total number of people who have ever lived.

2543/ Everyone has about 1 kg in weight of bacteria in their gut. Each gram of faeces contains 100,000,000,000 microbes.

2544/ Human adults excrete their own weight in faecal bacteria every year.

2545/ Without microbes we could not digest our food properly. Thanks to the bacteria inside the colon, which ferment about 100g of food each day, this part of our digestive tract is probably the most active organ in the body.

2546/ Microbes - bacteria, fungi, algae, protozoa and viruses - affect every aspect of life on earth. They have an amazing diversity of form and can exist in a wide range of habitats from hot springs to the icy wastes of Antarctica and inside the bodies of animals and plants. Microbes cause diseases like 'flu or malaria, but most are completely harmless. They are essential to the cycling of nutrients in the ecosystems of the planet. Microbial activity is exploited for the benefit of humankind in many ways, such as the production of medicines, food and enzymes, in the clean-up of sewage and other wastes and in the exciting advances resulting from developments in molecular biology techniques.

2547/ In the light of recent advances in molecular biology, which allow the comparison of the sequencing of ribosomal RNA of organisms, a new classification system is preferred by scientists. It is based on three lines of descent from a common ancestor. Each group is called a Domain:
1. Bacteria (true bacteria) - prokaryotes
2. Archaea (archaebacteria) - prokaryotes
3. Eukarya - eukaryotes

2548/ The eukaryotes include fungi, protozoa, algae, plants and all multicellular animals. Prokaryotes include bacteria and the mysterious archaebacteria which are prokaryotic in general structure but also share some characteristics with eukaryotes. Viruses are akaryotic because they are non-cellular. Prions are not micro-organisms but they are studied by microbiologists.

2549/ We consume the edible fruiting bodies of fungi when we eat mushrooms.

2550/ Lactic acid bacteria are used in the fermentation of milk to produce many dairy products such as yoghurt and cheese, vegetables to produce sauerkraut as well as fermented meat products such as salami.

2551/ The microbial genome, Deinococcus radiodurans, has the remarkable capacity to withstand massive space-scale doses of over 1.5 million rads of radiation - 3,000 times the dose that would kill a human in space.

2552/ C. acetobutylicum, a nonpathogenic microbe that can convert starch into the solvents acetone and butanol, enjoys an unusual place in history. Discovered in 1915 by Chaim Weizmann, the microbe was used by Great Britain during World War I for generating acetone to produce cordite for artillery shells. In gratitude, the government offered to honor Weizmann, but he asked instead for British support of a Jewish homeland in Palestine. This led to the Balfour Declaration of 1917, committing Britain to sanction what became in 1948 the state of Israel, with Weizmann as its first president.

2553/ In the warm waters of the Red Sea, and off the coast of Australia, the largest bacteria ever seen have been discovered in the guts of a fish. Epulopiscium fischelsoni is a bacterium of mammoth proportions. It can sometimes grow as large five hundred micrometers, or as about the size of the period at the end of this sentence, which is a remarkable size for bacteria.

2554/ The small size of most bacteria is owed to their limited abilities. Since they have few ways to transport nutrients across their cell membranes, they rely on diffusion to move food into their cells, and wastes out of them. This process of diffusion is limited by the surface area of a cell, which is the space that a cell's surface would occupy if it were stretched out flat. As a cell gets bigger, both its volume and surface area increase, but its surface area increases more slowly than its volume. Above a certain size, there is not enough surface area to absorb all of the nutrients that the increasing cell volume needs. So, the limit of a bacterium's size is related to the proportion of its surface area to its volume.

2555/ Organisms that use the earth's geomagnetic field have some type of internal compass. The smallest organisms that use this navigational method are called magnetotactic bacteria.

2556/ Magnetotactic bacteria were discovered in 1975 by Richard P. Blakemore. Blakemore noticed that some of the bacteria that he observed under a microscope always moved to the same side of the slide. If he held a magnet near the slide, the bacteria would move towards the north end of the magnet. These bacteria are able to do this because they make tiny, iron-containing, magnetic particles. Each of these particles is a magnet with a north pole and a south pole. The bacteria arrange these tiny magnets in a line to make one long magnet. They use this magnet as a compass to align themselves to the earth's geomagnetic field.

2557/ At the equator, the geomagnetic north doesn't point up or down, so the magnetotactic bacteria found there are a mixture of north-seeking and south-seeking bacteria.

2558/ Deinococcus radiodurans (said Din-o-coc-us rad-i-o-dew-ranz) was first found in food in the 1950's - food supposedly sterilized by radiation treatments.

2559/ It has been discovered that Deinococcus is as resistant to complete dehydration as it is to radiation. In fact, the same response is elicited by the organism when exposed to dry conditions as it is when exposed to high radiation levels, leading researchers to conclude that the organism evolved to survive long periods of dehydration, and that the resistance to radiation is only incidental to the discovery and development of radiation emitting technology during the second half of this century.

2560/ The first person to see microbes was a seventeenth century Dutch cloth merchant named Antoni van Leeuwenhoek. Leeuwenhoek made his own microscopes by grinding high-quality lenses, which he used to view drops of blood, pondwater, bits of skin, scrapings from his teeth, minerals, plant tissue and other samples. He called the tiny creatures he observed "animalcules." Even before we knew what they are, we were using microbes to do work for us, such as leavening bread, turning grapes into wine and curdling milk to make cheese. Now we have the means to manipulate microbial genes so that they make industrial enzymes, vitamins and many important medicines, as well as continue to perform their centuries old functions in food processing.

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