Microbes in Human Welfare Class 12 Notes: CBSE Biology Chapter 8

Microbes are beneficial as well as detrimental to the welfare of human beings. Microbes are utilized in many ways for human beings as explained below-

Microbes in vaccination and antibiotics/microbes in industrial products

The different products that are useful for humans are synthesized by microbes. The most common product obtained from microbes is beverages and antibiotics. For large-scale production and use of microbes in industries, The special vessels are referred to as fermenters for the use of microbes on large scale in industries.

Fermenters

Fermented Beverages are as old as civilization and are used in wine, whisky, brandy, etc. Saccharomyces cerevisiae commonly known as brewer’s yeast is the most common microbe used for fermentation. It has been used for fermenting malt-based cereals and fruit juices to produce ethanol. Different alcoholic drinks are produced based on the type of fermentation and raw material used. The drinks produced by distillation of the fermented broth are Whisky, brandy, and rum whereas wine and beer are produced through distillation.

Antibiotics are chemical substances produced using microbes against any disease-causing microbe. Penicillin, the first antibiotic discovered was obtained from mold is referred to as Penicillium notatum. For the treatment of different diseases like Whooping cough, leprosy, diphtheria, plague, etc antibiotics are required.

Some Antibiotics Produced by different Bacteria

For the production of certain chemicals like alcohols, enzymes, organic acids, etc, microbes are used. For example, Acetobacter aceti is used to produce acetic acid, Aspergillus niger is used to produce citric acid and Lactobacillus is used to produce lactic acid. Lipase enzymes can also be prepared using microbes. Streptokinase is produced by the bacterium Streptococcus which is very useful in removing clots from the blood vessels of patients who have undergone myocardial infarction leading to heart attack, thus acting as a ‘clot buster’. An immunosuppressive agent known as cyclosporin A is obtained from the fungus known as Trichoderma polysporum is used during organ transplant.

Microbes in Household Products

• Lactobacillus is the bacterium found in curd that is used to convert milk into curd.

• Lactic acid is produced from Lactobacillus, which partially digests milk protein and coagulates it to form curd.

• A small amount of curd is needed as an inoculum in milk to begin the curd-making process.

• Curd is a rich source of Vitamin B12.

• Fermentation is the process of converting sugar into alcohol without the presence of oxygen.

• Louis Pasteur discovered the process of fermentation.

• Dough used in food items such as idli, dosa, etc., is formed by the action of bacteria, which are responsible for the fermentation of the dough, resulting in the production of carbon dioxide.

• The dough used for making bread is fermented by yeast called Saccharomyces cerevisiae.

• Cheese is produced by fermenting bacteria called Propionibacterium shermanii.

• Different types of cheese have unique texture, taste and flavor, which are based on the types of microbes used in the fermentation process.

• Roquefort cheese is ripened by growing a selected fungus on it, which provides it with a specific flavor.

Microbes in Sewage Treatment

The human excreta is a major component of this wastewater. This municipal wastewater is also called sewage. Large amounts of organic matter and microbes are present inside it. To minimize the pollution, the excreta should be treated before release. To treat the sewage, heterotrophic bacteria which are naturally present in wastewater are required. It takes place in two stages- 

1. Primary Treatment 

2. Secondary Treatment. 

Sewage Treatment

Primary Treatment- 

It is the manual removal of small and large particles through filtration and sedimentation that begins the process of primary treatment. Firstly, sequential filtration removes debris. Then the soil and small pebbles are removed by sedimentation. leftover over known as effluent is taken for secondary treatment.

Secondary Treatment or Biological Treatment

• The principal effluent is sent via enormous aeration tanks, allowing aerobic bacteria to develop into flocs.  These microorganisms devour the majority of the organic materials in the wastewater as they grow.  This greatly reduces the effluent's BOD (biochemical oxygen demand). BOD is a measure of the amount of organic matter in water.  The higher the BOD of wastewater, the more it is polluting.

• After greatly reducing the BOD of sewage water, the effluent is fed into a settling tank where the bacterial 'flocs' are allowed to settle. This type of silt is known as activated sludge.

• A portion of this sludge is poured back into the aeration tank to act as an inoculum.

• The residual sludge is poured into enormous tanks known as anaerobic sludge digesters.

• Bacteria produce a combination of gases during digestion, including methane, hydrogen sulphide and carbon dioxide.  These gases combine to make biogas.

• The secondary treatment plant's effluent is often discharged into natural water bodies such as rivers and streams.

Microbes in Gobar Gas Formation 

Biogas is a mixture of different gases; methane percentage is the highest. Some bacteria, which grow anaerobically on cellulosic material, produce a large amount of methane along with CO2 and H2. These bacteria which produce methane as a result of anaerobic respiration are collectively called methanogens. is An example of methanogenic bacteria is Methanobacterium. 

Microbes as Biocontrol Agents 

Biocontrol is defined as the use of biological methods to control plant diseases and pests. Conventionally, pesticides and insecticides are being used for the control of diseases and pests. Hence, these chemicals are extremely toxic and harmful. 

Biological Control of Pests and Diseases. 

• Bacillus thuringiensis (Bt) is a bacterium used as a biocontrol agent against insects/pests.

• The endotoxin produced by Bt paralyses the gut of the insect/pest that consumes it.

• Bt cotton is an example of a plant-produced biocontrol agent.

• Trichoderma is a fungus used to control plant pathogens.

• Baculoviruses are pathogens of insects and other arthropods used as biocontrol agents.

• Most of the baculoviruses belong to the genus Nucleopolyhedrovirus and are ideal for narrow-spectrum actions.

• Baculoviruses have no negative impacts on other organisms like plants, mammals, birds, and fish, or even on non-target insects.

• Some microbes are used as bio-fertilizers.

• Rhizobium is a gram-negative bacterium found in leguminous plants that helps in nitrogen fixation.

Different Biocontrol Agents

Microbes in the Human Body

• Microbes colonize different parts of the human body including the skin, gut, and reproductive tract.

• The most important microbes in the human body are the Gut Microflora.

• The stomach microflora includes Streptococcus, Staphylococcus, etc., which are able to survive in the acidic conditions of the stomach.

• The intestinal flora belongs to Enterobacteriaceae, which is required for the process of digestion and absorption, leading to increased efficiency and utility of the gut.

• Certain microbes prevent the colonization of other harmful microbes and also secrete substances necessary for food digestion.

• In recombinant DNA technology, viruses are used as a vector for the transmission of a required gene.

Microbes as Biofertilizers

• Excess use of chemicals and their harmful effects have led farmers to switch to organic farming.

• Organic farming uses biofertilizers, which are organisms that enrich the soil's nutrients.

• Biofertilizers contain bacteria, fungi and cyanobacteria.

• Rhizobium bacteria are found in leguminous plants and are required by plants in the absorption of nitrogen.

• Other bacteria that fix nitrogen are Azospirillum and Azotobacter.

• Fungi form a symbiotic relationship with roots of higher plants and absorb phosphorus from the soil and pass it to the plant.

• Cyanobacteria are autotrophic microbes that fix atmospheric nitrogen, making them an important biofertilizer, especially in paddy fields.

• Cyanobacteria like Anabaena, Nostoc, and Oscillatoria are widely distributed in both aquatic and terrestrial environments.

• Blue-green algae add organic matter to the soil to increase its fertility.

5 Important Topics of Biology Class 12 Chapter 8 you shouldn’t Miss!

Importance of Class 12 Biology Microbes in Human Welfare Notes

• Microbes In Human Welfare Class 12 Short Notes break down intricate concepts related to microbial roles in medicine, agriculture, and industry into easy-to-understand explanations, making the subject more accessible.

• Summaries and key points help students remember essential information, aiding in long-term retention and mastery of the subject matter.

• Well-structured Microbes In Human Welfare Class 12 Notes facilitate efficient revision, especially during exam time, ensuring students cover all crucial topics effectively.

• Diagrams and illustrations in Microbes In Human Welfare Notes help visualise microbial processes and applications, improving comprehension and recall.

• Addresses all important topics and subtopics within the chapter, providing a thorough understanding of Microbes in Human Welfare.

Tips for Learning the Class 12 Biology Chapter 8 Microbes in Human Welfare 

• Start by grasping the fundamental roles of microbes in medicine, agriculture, industry, and environmental management to understand how they contribute to each area.

• Study diagrams, flowcharts, and illustrations to visualise microbial processes and applications, reinforcing your understanding and aiding in the recall.

• Use Microbes In Human Welfare Class 12 Short Notes of each section or topic, focusing on key points, definitions, and applications for easier review and retention.

• Work through practical examples and real-world applications of microbes, such as their use in fermentation, bioremediation, and production of antibiotics.

• Practice with past exam questions related to the chapter to familiarise yourself with the type of questions asked and how to approach them.

• Connect microbial processes and applications to everyday experiences, like how yoghurt is made or how biopesticides are used, to make the material more relatable and memorable.

Conclusion

Class 12 Biology Microbes In Human Welfare Notes provide crucial insights into how microbes benefit various aspects of human life. By understanding their roles in medicine, agriculture, industry, and environmental management, students gain a clear view of the practical applications of microbes. The notes simplify complex concepts with summaries, diagrams, and real-world examples, making it easier to grasp and remember important information. Regular review and practical examples help reinforce learning, ensuring students are well-prepared for exams and have a solid understanding of this essential topic.

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