Microorganisms play an important role in our life: helps us to digest our food, decompose wastes and participate in various life cycles
by thanh2v87 (student)
Microorganisms play an important role in our life: helps us to digest our food, decompose wastes and participate in various life cycles. They are diverse and have adapted to inhabit different environments including extreme conditions, such as hot vents under the ocean to ice caps; hence known as extremophiles. There are more microorganisms present in us than there are cells, and the various microorganisms are bacteria, viruses, fungi and protozoa. Many people associate microorganisms as death and diseases causing agents; also frequently compared to dirt. Although some microorganisms are responsible for causing diseases, most microorganisms’ original hosts are not the human body so are not pathogenic, but commensal. This essay will discuss the numerous beneficial microorganisms that carry out processes in biotechnology, agriculture, industries and environment; necessary to sustain life. First of all, essential uses of microorganisms are seen in the environment, as they play a vital role in many of the nutrient cycles. For instance, carbon fixation from the atmosphere during the carbon cycle by autotrophic bacteria, such as cyanobacteria; synthesizes organic molecules for other organisms and release oxygen for our consumption. In addition, microorganisms are vital participants of the food chain since they act as decomposers; breaking down dead organisms and organic materials and releasing minerals for uptake by living organisms and CO2 back into the atmosphere for photosynthetic organisms. Microorganisms, known as methanogens, influence the carbon cycle by converting CO2 in their cells to methane and releasing it into atmosphere; thus increasing methane concentration whereas methanothrophs consume methane from the atmosphere, leading to a decrease in the greenhouse gas and global warming (Prescott, 1999). Involvement of microorganisms in the nitrogen cycle demonstrates that they are not just beneficial for humans, but are significant to plants as well; especially diazotrophs. Plants and diazotrophs have developed a symbiotic relationship, for example, Rhizobium present in the nodules on legume roots, fixes nitrogen enabling the plant to flourish in nitrogen-deficient grounds. Microorganisms are crucial for all three steps of nitrogen cycle: firstly, Nitrosomonas and Nitrosococcus convert ammonium ions to nitrite and Nitrobacter convert nitrite to nitrate during nitrification; secondly, during denitrification Pseudomonas denitrificans reduces nitrate to nitrogen gas and thirdly nitrogen fixation, with the diazotrophs reducing nitrogen from the air into ammonia; utilized by the plants to synthesize DNA and amino acid. Another microorganism interacting with the plants are mycorrhizal fungi, which forms a symbiotic relationship
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with plant roots. This association is beneficial for plants as fungal hyphae increases surface area enabling the plant roots to absorb more nutrients; also advantageous to fungi since they gain sugars produced by plants during photosynthesis (Atlas &ump; Bartha, 1998).Moreover, microorganisms digest harmful chemicals, such as pollutants and chemical wastes produced by the industry through a process known as bioremediation; thus protecting the environment and human health. In this process, microorganisms grow over a solid substrate to form a biofilm, through which the fluid containing the contaminants passes through, so that the enzymes produced by the microorganism can degrade the contaminant and the resulting fluid is non-toxic. In a similar process microorganisms aid sewage water treatment: primary treatment, such as screening, results in digestion of sludge by anaerobic microorganisms; during secondary treatment microorganisms enable floc formation, biodegradation and neutralization of toxins when passed over the microbial films, for example, Geobacter sulfurreducens purifies contaminated water by precipitating metals such as uranium (Hofkin, 2010). Applications of microorganisms in the food industry, mainly in the production of dairy products are another example where microorganisms are beneficial to humans. Lactobacillus bulgaricus and Streptococcus thermophilus converts lactose in milk into lactic acid, causing the milk to coagulate during fermentation (reduction and oxidation of organic molecules) and form yoghurt in the process. Furthermore, probiotic yoghurt with live bacteria’s are also produced nowadays, to maintain microbial flora balance in our gut and prevent the growth of pathogens. Fermentation of milk by lactic acid bacteria also causes the milk to coagulate and form curd; then additional organisms forms the various cheeses, such as Penicillium camemberti produces Camembert. Another example is addition of Streptococcus lactis and Leuconostoc citrovorum to cream during fermentation to produce lactic acid, which causes thickening of the cream, and gives rise to the flavour attributed to sour cream. Furthermore, microbes such as yeasts which help us in the process of bread making, alcohol production and food preservation are also part of our diet. For example, marmite and vegemite made from “spent brewer’s yeast” are rich in vitamins. Additionally, Fusarium graminearum, a type of fungus developed into meat substitute for human consumption. The success of the food industry is partially due to the careful selection and addition of beneficial microorganisms, leading to a variety of cultured food for a wide range of people (Hofkin, 2010). Understanding microbe’s genetics has enabled us to use microorganisms in genetic-engineering techniques, such as gene cloning, and has given numerous benefits to the biotechnological industry. Microorganisms, such as bacteria, viruses and bacteriophages, act as cloning vectors to transfer specific sequence of gene, into the plasmid of bacterial cell using restriction enzymes. The purpose of the restriction enzyme is to bind to the inverted palindrome in both chromosomal and vector DNA; thus cleaving the DNA and producing sticky ends. DNA ligase joins the sticky ends of both DNA producing a recombinant DNA; used to transform the bacteria host cell. The bacteria can be induced to produce the proteins which these genes encode as the vector replicates and divides to produce new cells. Since the vector contains a selectable marker, maybe coding for antibiotic resistant gene, the bacterial cells which has taken up the recombinant DNA are identified. Proteins from recombinant technology are used to produce medicines, synthetic vaccines and other vital substances, such as insulin for diabetic individuals. Application of microorganisms in the medical industry is beneficial to human health, but also to the economy because huge amount of medicines being produced using microorganisms, such as insulin from E.coli, lowers the cost of production (Hofkin, 2010). Retrovirus, acts as a vector in gene therapy to treat ADA deficiency; patient’s ADA-deficient lymphocytes is cultured in the laboratory and infected with the retrovirus that contains the normal ADA gene, creating a recombinant retroviruses. During the replication of the retrovirus, its own DNA containing the normal ADA gene is inserted into the host’s DNA causing the patient's lymphocytes to synthesize ADA (Hofkin, 2010). Another application of recombinant techniques in the biotechnology industry, is the production of heat stable enzymes from thermophiles; organisms that live in an extremely hot environment. For instance, DNA polymerase produced from Thermus aquaticus and Thermococcus litoralis is used in the PCR and DNA fingerprinting, has enabled tracing of the fate of genes in plant and animal populations and improved gathering of evidence at crime scenes. Similarly, another enzyme, which breaks down lignin, obtained from Phanerochaete chrysosporium is used in the paper industry to bleach paper without the production of dioxin; thus preventing pollution (Hofkin, 2010). Application of genetic-engineering techniques in agriculture is the production of transgenic plants, using Agrobacterium tumefaciens to introduce cloned genes, such as resistant to environmental stress. This is achieved by replacing the genes in T-DNA of Ti plasmid that causes the crown gall tumour with the gene of interest and a selectable marker gene, usually resistance to kanamycin. The T-DNA is then incorporated into the plant genome when exposed to A. tumefaciens, and these cells grown in a medium containing kanamycin and carbenicillin. Transgenic plants have led to the development of biodegradable plastics and medical products such as production of vaccines from altering transgenic plants (Prescott, 1999). Another example of benefits of microorganism in agriculture is their use as biological pest control; for example, Bacillus thuringiensis produce Bt-toxin which is lethal for insects if ingested, but non-pathogenic to humans and other animals. Bt-toxin gene is genetically engineered into crops to increase their yield; consequently benefitting the economy. Some viruses are also microbial biopesticides, baculoviruses, and they specifically target caterpillars, by releasing nucleocaspsids – causes the insect to die – when ingested; therefore they are efficient pest control without huge environmental side-effects (Hofkin, 2010). Usually microorganisms are associated with causing cancer, but recent developments have highlighted they could be used in treating cancer. William B. Coley showed that the tumors relapsed when cancer patients were injected with various pathogens, such as Coley's toxin. Recent research findings have revealed that Mycobacterium bovis can be used in treating bladder cancer, as the BCG strain in microorganism kills the tumor (Chakrabarty, 2003). Similarly, recent development has suggested that Bdellovibrio bacteriovorus could be used as antibiotics, since they ingest E.coli, Salmonella spp. and other disease causing gram-negative bacteria, without affecting the humans (Rendulic et al., 2004). An additional important application of microorganism in medical industry is using bacteriophage to make antibiotics for curing anthrax. Schuch and his colleagues (2002) obtained enzyme, PlyG, from the bacteriophage; its function is to lyse the bacterial wall of B. anthracis. Their research revealed that PlyG was a strong lytic enzyme, because even when applied externally they still lysed the B. anthracis strains; and that 80% of B. anthracis infected mice was saved when injected with the enzyme. Another example of importance of microorganism in medical industry is synthesis of steroid hormones, for instance Rhizopus nigricans, which convert sterol compound into the hormones through bioconversions. Also, antibiotics are produced by the secondary metabolites of microorganisms, for example Streptomyces griseus produces streptomycin and penicillin is produced from Penicillium, when its growth is prevented due to less nutrients. (Prescott, 1999). Human’s digestive system, include different species of friendly bacteria which are vital for metabolism of food, production of enzymes and vitamins to aid digestion (e.g., ß-galactosidase, amylase), demolition of disease-causing microorganisms and regulation of intestinal acidity. Non-pathogenic bacteria, such as Lactobacillius spp., forms a symbiotic relationship with most multicellular organisms and is essential to the maintenance of our health, as they ensure that pathogenic bacteria is prevented from growing; aids our immune system in the process. Similarly, microorganisms existing in ruminants' digestive system break down cellulose into monosaccharaides releasing usable energy in the process; and the ruminant also use the microorganism as a source of amino acids and other products (Hofkin, 2010). Microorganisms being used in various researches throughout history, led to the advancement of science and technology. For example, using pathogenic and non-pathogenic strains of Streptococcus pneumoniae by Frederick Griffith to show that there was genetic material through the principal of transformation; and then Avery, MacLeod and McCarty used the same microorganism to show that DNA was the transforming principle. Another crucial experiment was Hershey &ump; Chase experiment using E.coli and T2 bacteriophage which showed that DNA is the hereditary material (Prescott, 1999). Microbial mining is where acidophilic bacteria, such as Thiobacillus ferroxidans are used to obtain copper from their ore. Acidic solution is showered over the copper ore, to increase bacterial growth residing in the soil surrounding the ore. The metabolic waste produced by the bacteria, sulphuric acid, causes the copper to leach out of the rock, preventing toxic chemicals to be released to the environment and is cheaper. Although, microbial mining can only occur where the soil around the ore deposits contains the microorganisms; further research has been conducted to produce genetically engineered bacterial strains, with the ability to excavate minerals from ores containing low-levels of minerals (Hofkin, 2010). Microorganisms have been beneficial to humans in the past too - the Weil-Felix test for typhus. A patient infected with Rickettsia prosecute will have antibodies to this bacterial species circulating in their blood which can bind to Proteus OX19, harmless soil bacterium. Physicians used to diagnose typhus by mixing patient's blood serum with Proteus OX19, positive test for typhus is confirmed when Proteus OX19 is clumped together (Hofkin, 2010). Overall, microorganisms are vital for life on Earth and are more than disease causing agents. Few microorganisms are pathogenic, but many more has an important role in various ecological and industrial processes, maintaining human health; and every day new discoveries are made that shows microorganisms are crucial for scientific advances to be made.