Microorganisms play an important role in the decay and release of nutrients from dead organisms and their waste products (Clegg and Mackean, 2000). Although some cause disease, humans would not exist if there were no inputs on the ecosystem. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Bacteria play an important role in the global ecosystem, however, decomposition is one of the most important roles of bacteria. It is described as the degradation of organisms and the release of nutrients into the environment (Ucmp.berkeley.edu, 2018). Another important role of bacteria is the nitrogen cycle. Plants rely on nitrogen through soil use to aid in their health and growth, and it cannot be obtained from nitrogen gas in the atmosphere. These two roles are a vital component to the maintenance of human life. The Earth's atmosphere is composed of 78% nitrogen, 22% oxygen, carbon dioxide and other greenhouse gases (Fullick, 1994). Nitrogen is a natural element essential for the growth and reproduction of both plants and animals (Science and Earth, 2018). In order for plants and animals to obtain nitrogen, it must be converted into nitrates, nitrogen compounds mixed with hydrogen. Although nitrogen gas makes up 78% of Earth's atmosphere, it is very non-reactive, meaning it is impossible for plants to use it directly. Instead, they need a supply of fixed nitrogen such as ammonium ions (NH4+) or nitrate ions (NO3-). All nitrogen-fixing organisms live free in the soil, while others are endophytes (Campbell et al, 2014). The bacteria involved include cyanobacteria, and organisms such as rhizobial bacteria form efficient and intimate associations with legume roots. The product of the initial stages of nitrogen fixation is ammonia. In the soil, ammonia is then rapidly converted to nitrates by bacteria such as Nitrosomas and then to nitrates by other bacteria such as Nitrobacter. In legumes, amino acids are synthesized directly using ammonia resulting from initial nitrogen fixation. Nitrates produced by nitrogen fixation are used to form proteins of plant and later animal tissues. Nitrogen is eventually released from the dead, decaying tissues of both plants and animals through the action of even more bacteria such as Thiobacilus deitficans (Fullick, 1999). Lightening is another way nitrogen can be converted into nitrogen compounds that can be used by plants. and animals. Lightning strikes when nitrogen fixation occurs and accounts for only 10% of nitrogen fixation worldwide (OCR A2 Biology Student Book, 2008). There are different types of foods and drinks produced with the help of microorganisms, however, yeast is a type of fungus that is used in different ways in the production of bread, beer and wines. The most common form of yeast used in bread is Saccharomyces cerevisiae (Hocking et al, 2008). Can use aerobic respiration, breathing with the presence of oxygen. During this process the yeast is used as sugar and the sugars present in the flour as food. It is broken down to provide the yeast with energy to rise. The yeast rises by budding and thus carbon dioxide gas bubbles are produced in the dough. The bubble causes the dough to expand because the dough becomes sticky and blocks the bubbles from escaping. Once the dough is cooked, the heat kills the yeast and the dough stops expanding (Microbiologyonline.org, 2018). Food production is another role of bacteria. Lactobacillus bulgaricus is.