Milk is converted into curd by lactic acid bacteria such as Lactobacillus. A small drop of curd diluted with water and stained can show bacterial cells under the microscope. Other possible samples include pond water or spoiled food, but curd is easy to carry and reliably contains bacteria.
Curd is a suitable sample because it contains abundant lactic acid bacteria that can be observed under a microscope.
When yeast ferments sugars in dough, carbon dioxide bubbles make the dough rise. In anaerobic sludge digesters and rumen, methanogens such as Methanobacterium produce methane along with carbon dioxide and hydrogen. These examples show gas release during microbial metabolism.
Yeast releases carbon dioxide during fermentation of dough, and methanogenic bacteria release methane during anaerobic digestion in biogas plants and cattle rumen.
LAB such as Lactobacillus grow in milk and produce acids that coagulate milk proteins to form curd. Their growth partly digests milk proteins, improves vitamin content and can suppress harmful microbes in the gut.
Lactic acid bacteria are found in curd. They convert milk into curd, improve nutritional quality by increasing vitamin B12, and help check disease-causing microbes in the stomach.
Microbes ferment the batter or dough, producing acids and carbon dioxide. This improves texture, flavour and digestibility. Idli and dosa fermentation involves bacteria and yeasts in rice and pulse batter, while leavened wheat products use yeast fermentation.
Examples include dosa and idli made from fermented rice and black gram batter, dhokla made from fermented Bengal gram/rice batter, and bread or bhatura made from fermented wheat dough.
Antibiotics are chemical substances produced by some microbes that kill or inhibit disease-causing bacteria. Penicillin, produced by Penicillium, was the first widely used antibiotic. Many other antibiotics are produced by fungi and bacteria and are used to treat bacterial infections.
Microbes have helped control bacterial diseases by producing antibiotics.
Penicillin was discovered from Penicillium notatum, and improved industrial production has used Penicillium chrysogenum. Both are fungal sources associated with penicillin production.
Penicillium notatum and Penicillium chrysogenum are fungi used for antibiotic production.
Untreated sewage contains disease-causing bacteria, protozoa and other microbes. If released into water bodies, microbes decompose its organic matter and consume dissolved oxygen, leading to high BOD and oxygen depletion. This can kill aquatic organisms and spread water-borne diseases.
Sewage is municipal wastewater containing human excreta, organic matter and microbes. It can spread pathogens, pollute water and increase biological oxygen demand, harming aquatic life.
Primary treatment uses filtration and sedimentation to remove grit, floating debris and suspended solids. Secondary treatment uses aerobic microbes in aeration tanks to form flocs that consume organic matter and reduce BOD. The sludge may then be treated anaerobically.
Primary treatment is a physical process that removes large and suspended solids; secondary treatment is a biological process in which microbes degrade organic matter.
Methanogens such as Methanobacterium act on dung and sewage sludge under anaerobic conditions. They produce methane, carbon dioxide and hydrogen. Biogas plants collect this gas and use it for cooking, lighting or energy generation.
Yes. Methanogenic microbes produce biogas, a fuel rich in methane, during anaerobic digestion of organic wastes.
Biofertilisers such as Rhizobium, Azotobacter, Azospirillum and cyanobacteria fix atmospheric nitrogen and enrich soil nutrients. Mycorrhiza improves phosphorus absorption and plant resistance. Biocontrol agents such as Bacillus thuringiensis, Trichoderma and baculoviruses control pests and pathogens in a targeted way, reducing chemical pesticide dependence.
Microbes reduce fertiliser use by acting as biofertilisers and reduce pesticide use by acting as biocontrol agents.
BOD measures the amount of oxygen required by microbes to oxidise organic matter. Higher BOD means more organic pollution. Untreated sewage has the highest BOD, so C = 400 mg/L is untreated sewage. Relatively clean river water has the lowest BOD, so B = 8 mg/L. The remaining sample A = 20 mg/L is secondary effluent.
Sample C is most polluted. A is secondary effluent, B is river water and C is untreated sewage water.
Cyclosporin A is produced by the fungus Trichoderma polysporum and is used as an immunosuppressant in organ transplantation. Statins produced by Monascus purpureus inhibit cholesterol synthesis and help lower blood cholesterol.
Cyclosporin A is obtained from Trichoderma polysporum, and statins are obtained from Monascus purpureus.
For SCP, microbes such as bacteria, yeast and algae can be cultured on suitable substrates to produce large amounts of edible protein-rich biomass. In soil, bacteria and fungi decompose dead organic matter and release minerals. Rhizobium and cyanobacteria fix nitrogen, and mycorrhizal fungi improve phosphorus uptake and plant growth.
(a) Microbes are grown as protein-rich biomass called single cell protein for food or feed. (b) In soil, microbes decompose organic matter, recycle nutrients, fix nitrogen, form mycorrhizae and improve fertility.