Microbes have apparently gained a scary reputation among general public since long time as bad guys, as dirty causes of disease. This image change is now in full swing, with various adverts such as probiotics, antibiotics and environment cleaners etc reminding us that some microbes are vital to our health, esthetics and livelihood.
Since evolution: In fact, humans couldn’t have evolved without microbes. Billions of years ago, microbes converted the Earth’s entire atmosphere from nitrogen-based to oxygen-based, making it possible for larger forms of life to evolve. Human evolution has been inextricably linked with the microbes that have surrounded us from the very beginning.
Even in industry, microbes are used to synthesize a number of products valuable to human beings. Beverages and antibiotics are some examples. Production on an industrial scale requires growing microbes in very large vessels called fomenters.
Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum. For this purpose the same yeast Saccharomyces cerevisiae used for bread-making and commonly called brewer’s yeast, is used for fermenting malted cereals and fruit juices, to produce ethanol. Do you recollect the metabolic reactions, which result in the production of ethanol by yeast? Depending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained. Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.
Food aspect: Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produces acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12. In our stomach too, the LAB play very beneficial role in checking disease causing microbes. The dough, which is used for making foods such as dosa and idli is also fermented by bacteria. The puffed-up appearance of dough is due to the production of CO2 gas.
A number of traditional drinks and foods are also made by fermentation by the microbes. ‘Toddy’, a traditional drink of some parts of southern India is made by fermenting sap from palms. Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods. Cheese, is one of the oldest food items in which microbes were used. Different varieties of cheese are known by their characteristic texture, flavor and taste, the specificity coming from the microbes used. For example, the large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii. The ‘Roquefort cheese’ is ripened by growing specific fungi on them, which gives them a particular flavor. Many of the foods we eat would be indigestible without the 10-100 trillion microbes living within our guts. Microbes also play a major role in creating many of the foods we love, such as cheese, yogurt and bread.
Master chemists: Hundreds of drugs available today were derived from chemicals first found in microbes. Scientists can use the amazing variety of chemicals microbes naturally produce to create new medicines. Antibiotics produced by microbes are regarded as one of the most significant discoveries of the twentieth century and have greatly contributed towards the welfare of the human society. Anti is a Greek word that means ‘against’ and bio means ‘life’, together they mean ‘against life’ (in the context of disease causing organisms); whereas with reference to human beings, they are ‘pro life’ and not against. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.
Microbes for agriculture:
Farmers and ranchers often think of microbes as pests that are destructive to their crops or animals (as well as themselves), but many microbes are beneficial. Soil microbes (bacteria and fungi) are essential for decomposing organic matter and recycling old plant material. Some soil bacteria and fungi form relationships with plant roots that provide important nutrients like nitrogen or phosphorus. Fungi can colonize upper parts of plants and provide many benefits, including drought tolerance, heat tolerance, resistance to insects and resistance to plant diseases.
Cleaning up: Because of their special adaptations, some microbes actually degrade—and there by render harmless—chemicals that are extremely dangerous to humans. These microbes can help clean up gasoline leaks, oil spills, sewage, nuclear waste, and many other types of pollution.
Light warriors: Without microbes, we wouldn’t have oxygen to breathe. Plants aren’t the only things that carry out photosynthesis: photosynthetic microbes are responsible for about half of the photosynthesis on Earth, simultaneously increasing the amount of oxygen and decreasing the amount of carbon dioxide in the air. Through this process, microbes are helping to mitigate some of the greenhouse gasses that cause global warming.
Soil-microbe link-up: A renowned microbiologist once remarked, "A soil devoid of microorganisms is a dead soil". Soil microbes provide ecosystem services and vital benefits to soil to maintain its living nature. Economic valuations show nature is worth US $1.5tn/year to agriculture and horticulture worldwide. Nutrient cycling in fertile soils is one of the most vital ecosystem functions that microbes perform. An estimate says that (Professor Sandhu, New Zealand) the financial value of ecosystem services from soil microbes that improve fertility as on average US $160.65/ha/year in organic fields and US $142/ha/year in conventionally managed land.
Plant-Microbe link-up: Microbes and plant roots communicate by exchanging chemical signals. These natural communications offer next generations of Eco-benign fertilizers, crop stimulants and protectants. For example, Isopyrazam (IZM), Syngenta's new cereal fungicide, is a move in this direction. Mycorrhizas increase root access to nutrients, particularly phosphorus, improve water uptake and defend them against invading pathogens. Carbon from dead plants and animals is recycled naturally back into the atmosphere as carbon dioxide by microbes using chemical energy. Nitrogen is taken by free-living soil bacteria from organic matter and added to the soil. Associations of bacteria living with legume roots add further nitrogen supplies into soils. Fixation of atmospheric nitrogen by legume-rhizobia deposits nitrogen about 33-46mn tones/year worldwide. At current fertilizer prices, this is worth US $50-70bn yearly.
Master pathologists: Fertile soils rich in microbes suppress plant pathogens. Such soil beneficial bacteria include Bacillus spp, Enterobacter spp, Flavobacterium balustinum and Pseudomonas spp and fungi such as Penicillium spp, Gliocladium virens and several Trichoderma spp. The crops that benefit this natural biocontrol include Pythium in turf grass, snow moulds in turf grass and Fusarium, Pythium and Rhizoctonia in tomato and cucumber. Suppression of Rhizoctonia solani attacking cucumber resulted from inoculating seedling compost with Trichoderma asperellum, while a reduction of bacterial leaf spot of radish, lettuce and tomato followed inoculation of compost with T. hamatum. Some free-living soil fungi diminish soil nematode populations very effectively. Their fungal hyphae form nooses that capture the nematodes and then they exude enzymes that dissolve them.
Microbe: the healers: Microbes play an unexpected role in the healing process. For example, the papilloma virus is associated with cervical cancer. The virus helps break down the excess tissue in the second half of the healing phase.
Production of Foods: Microbes are a key component in both home and industrial food preparation. Lactic acid bacteria are used to make yogurt, cheese, sour cream, buttermilk and other fermented milk products. Vinegars are produced by bacterial acetic acid fermentation. Yeast is used in the manufacture of beer and wine and for the leavening of breads. It is also involved in fermentations to convert corn and other vegetable carbohydrates into ethanol to make beer, wine, or gasohol; but bacteria are the agents of most other food fermentations. Other fermented foods include soy sauce, sauerkraut, dill pickles, olives, salami, cocoa and black teas.
Medical applications: The microbes that normally live in association with humans on the various surfaces of the body (called the normal micro-flora), such as Lactobacillus and Bifidobacterium, are known to protect their hosts from infections and otherwise promote nutrition and health. Antibiotics are secondary metabolites produced by microorganisms that kill or inhibit the growth of other microbes. They are used in the treatment of infectious disease. Antibiotics are produced in nature by molds such as Penicillium and bacteria such as Streptomyces and Bacillus. Vaccines are substances derived from microorganisms and are used to immunize against disease. The microbes that are the cause of infectious disease are usually the ultimate source of vaccines.
“We’re organisms; we’re conceived, we’re born, we live, we die, and we decay. But as we decay we feed the world of the living: plants and bugs and bacteria”
William M. Bass……