Microbes

• Besides macroscopic plants and animals, microbes are the major components of biological systems on this earth
• Microbes are present everywhere – in soil, water, air, inside our bodies and that of other animals and plants. They are present even at sites where no other life-form could possibly exist–sites such as deep inside the geysers (thermal vents) where the temperature may be as high as 1000C, deep in the soil, under the layers of snow several metres thick, and in highly acidic environments
• Microbes

  • Protozoa
  • Bacteria
  • Fungi
  • Microscopic animal and plant viruses
  • Viroids
  • Prions that are proteinacious infectious agents
• Microbes like bacteria and many fungi can be grown on nutritive media to form colonies that can be seen with the naked eyes. Such cultures are useful in studies on micro-organisms
• Microbes cause a large number of diseases in human beings. They also cause diseases in animals and plants
• Several microbes are useful to man in diverse ways
• Lactic acid bacteria (LAB)


  Microbes that grow in milk and convert it to curd
• Fermentation of dough

  Bacteria produce CO2 gas, causing the dough to puff up
• Traditional drinks and foods made by fermentation

  • Toddy
  • Fermented fish, soyabean and bamboo-shoots
• Cheese

  Different varieties have characteristic texture, flavour and taste due to the specific microbes used
• Propionibacterium sharmanii


  Bacterium that produces large amount of CO2, causing the holes in Swiss cheese
• Roquefort cheese


  Ripened by growing a specific fungus, which gives them a particular flavour
• Saccharomyces cerevisiae

  Yeast used for bread-making and production of fermented beverages
• Production of fermented beverages

  1. Yeast ferments malted cereals and fruit juices to produce ethanol

  2. Different types of alcoholic drinks are obtained depending on the raw material and processing
• Antibiotics


  Chemical substances produced by microbes that can kill or retard the growth of other (disease-causing) microbes
• Penicillin was the first antibiotic to be discovered, and it was a chance discovery by Alexander Fleming
• Antibiotics have greatly improved our capacity to treat deadly diseases such as plague, whooping cough, diphtheria and leprosy
• Microbes used for commercial and industrial production

  • Organic acids (citric acid, acetic acid, butyric acid, lactic acid)
  • Alcohols (ethanol)
  • Enzymes (lipases, pectinases, proteases, streptokinase, statins)
• Sewage treatment

  1. Primary treatment (physical removal of particles)

  2. Secondary treatment (biological treatment by aerobic microbes to reduce BOD)
• Activated sludge

  Bacterial 'flocs' that settle in the secondary treatment plant
• Anaerobic sludge digesters


  Anaerobic bacteria digest the bacteria and fungi in the sludge, producing biogas
• Microbes play a major role in treating millions of gallons of waste water everyday across the globe
• Ganga Action Plan and Yamuna Action Plan have been initiated to save these major rivers from pollution by building more sewage treatment plants
• Methanogens

  Anaerobic bacteria that produce large amounts of methane, along with CO2 and H2
• Methanogens are present in the anaerobic sludge during sewage treatment and in the rumen of cattle
• that only treated sewage may be discharged in the rivers
• A visit to a sewage treatment plant situated in any place near you would be a very interesting and educating experience
• Biogas


  A mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel
• Biogas production

  1. Microbes grow anaerobically on cellulosic material and produce large amounts of methane along with CO2 and H2

  2. Methanogens like Methanobacterium are commonly found in the anaerobic sludge during sewage treatment

  3. Methanogens are also present in the rumen (stomach) of cattle and help in the breakdown of cellulose
• Humans cannot digest cellulose present in our foods
• Gobar gas

  Biogas produced from the excreta (dung) of cattle
• Biogas plant

  1. Concrete tank where bio-wastes are collected and a slurry of dung is fed

  2. Floating cover over the slurry keeps rising as gas is produced

  3. Outlet pipe supplies biogas to nearby houses

  4. Spent slurry removed and used as fertiliser
• Biogas plants are more often built in rural areas where cattle dung is available in large quantities
• The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC)
• Biocontrol refers to the use of biological methods for controlling plant diseases and pests
• Organic farming uses biocontrol measures to reduce dependence on toxic chemicals and pesticides
• Organic farming approach

  • Develop understanding of the webs of interaction between the organisms in the field
  • Eradication of 'pests' is undesirable as it would affect the beneficial predatory and parasitic insects
• Bt-cotton is an example of genetically engineered plants resistant to insect pests
• Biofertilisers


  Organisms that enrich the nutrient quality of the soil
• Main sources of biofertilisers

  • Bacteria
  • Fungi
  • Cyanobacteria