How would you convince a friend that microorganisms are more than just disease causing agents?
An entire kingdom of microorganisms was brought into life 3 billion years ago. Since then «the earth is a fundamentally a microbial planet, to which the micro-organisms are recent the relatively unimportant additions» (Wheelis, Mark, Principles of modern microbiology, 2008, p.1). The term microorganisms consist of bacteria, archaea, fungi, and protest, which can either be unicellular or multicellular. They first have been studied by Anton van Leeuwenhoek by the use of his own design microscope, in 1675. However, they have been an attractive source of study for many scientists, since they live in all parts of biosphere and are critical to nutrient recycling in ecosystems. Microbes in general are described as one of the most remarkable existence. «The procaryotes in particular are by very large margin the most biochemically and genetically diverse organisms on earth» (Wheelis, Mark, Principles of modern microbiology, 2008, p.23). Since the microorganisms were the first living being in earth they have an important regulatory role in ecosystem balance. Many of them contribute to the four major biochemical cycles; the carbon, nitrogen, sulphur and iron cycle. An example of carbon cycling at local scale is in ruminants where the digestion of cellulose occurs through microbial activity. These cellulolytic microbes hydrolyze cellulose to disaccharide cellobiose and glucose. Glucose then undergoes bacterial fermentation producing volatile fatty acids, CO₂ and methane. Many vitamins are synthesized at this point and microbial cells also good protein source. The nitrogen cycle is the main reservoir for nitrogen is the air where it is present as nitrogen gas. It includes three major processes of microbial nitrogen transformation; Nitrogen fixation, Nitrification and Denitrification. In case of sulphur cycle, sulphur contributes to the radiation balance of the earth. It reduces the amount of solar energy entering the earth, atmosphere and ocean system, thereby contributing to a cooling of the planet. In addition, at the iron cycle Leptospirillum ferooxidans and Geobacter metallireducens unergo anaerobic oxidation of organic compounds to CO2 using Ferric iron as an electron acceptor.
Image 1: Diagram of the carbon cycle. The black numbers indicate how much carbon is stored in various reservoirs, in billions of tons. The purple numbers indicate how much carbon moves between reservoirs each year.
By the time that scientists began began to understand the basis of their activities, the industrial microbiology has been familiar to a great development. This relatively new science describes «the isolation and description of microorganisms from natural environments, such as soil or water, and with the culture conditions required for obtaining rapid and massive growth of these organisms in large scale culture vessels commonly known as fermentors» (Casida, Industrial microbiology, 1968, p.4). Fermentation consist the central process to microbial biotech. In biochemistry the term mainly refers to the generation of energy by the oxidation of organic compounds using an endogenous electron acceptor. It can be carried out both in aerobic and anaerobic conditions. Despite the presence of oxygen, many microbes such as yeast prefer the fermentation to oxidative phosphorylation, as long as sugars are available for consumption. The production of ATP by fermentation, where the net-gain of energy is two molecules of ATP, is less efficient than oxidative phosporylation, a process whereby pyruvate is fully oxidized to carbon dioxide and the net-gain of ATP is 36 molecules. Since fermentation consists the main energy source in anaerobic conditions, it can be distinguished in three categories; the lactic acid fermentation, the ethanol fermentation and as hydrogen gas. The lactic acid fermentation is usually...
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