Questions: Microbes in Human Welfare

Q1. Which household sample would you carry to the laboratory to show microbes, and why?

Answer (English): Curd is the best choice, because a small spoonful contains millions of living lactic acid bacteria. A drop smeared on a slide shows bacteria under the microscope, and the same sample can be spread on nutritive medium to grow visible colonies within a day or two. Fermented idli batter works the same way. Soil is a poor choice for a first demonstration because the soil particles hide the cells and many soil microbes grow slowly.

Hinglish: Curd sabse achha sample hai, kyunki ek chhoti chammach mein lakhon lactic acid bacteria hote hain. Slide par lagane par microscope mein bacteria dikhte hain, aur nutritive medium par ek do din mein colonies bhi ban jaati hain. Idli ka batter bhi wahi kaam deta hai. Soil pehli baar ke liye theek nahi, kyunki mitti ke particles cells ko chhupa dete hain.

Q2. Give two examples that show microbes release gases during metabolism.

Answer (English): First, idli and dosa batters puff up because bacteria in the batter release carbon dioxide during fermentation. Second, Swiss cheese develops its large holes because Propionibacterium sharmanii releases a large amount of carbon dioxide. A third example is biogas, where methanogens release methane and carbon dioxide from cellulosic waste.

Hinglish: Idli aur dosa ka batter bacteria ke CO2 se phoolta hai, yeh pehla example hai. Doosra, Swiss cheese ke bade holes Propionibacterium sharmanii ke carbon dioxide se bante hain. Teesra example biogas hai, jahan methanogens methane aur CO2 dete hain.

Q3. In which foods do you find lactic acid bacteria, and what are their useful applications?

Answer (English): Lactic acid bacteria are found in curd and other fermented milk foods. They convert milk into curd, raise the vitamin B12 content of curd, and produce lactic acid on an industrial scale. In the human stomach they check the growth of disease-causing microbes, so they support digestion and health.

Hinglish: LAB curd aur doosre fermented milk foods mein milte hain. Yeh doodh ko curd banate hain, vitamin B12 badhate hain, aur industry ke liye lactic acid banate hain. Pet mein yeh harmful microbes ko rokte hain, isliye digestion aur health ke liye faydemand hain.

Q4. Name traditional Indian foods made from wheat, rice and Bengal gram that involve microbes.

Answer (English): From wheat, bread is made from dough fermented by baker's yeast. From rice, the fermented batter for idli and dosa is prepared by bacteria that release carbon dioxide. From Bengal gram flour, khaman and dhokla are made from a fermented batter. Toddy, made from fermented palm sap, belongs to the same family of traditional fermented foods.

Hinglish: Wheat se bread banti hai jiska dough baker's yeast ferment karta hai. Rice se idli aur dosa ka batter banta hai, jise bacteria CO2 dekar phoolate hain. Bengal gram ke aate se khaman aur dhokla banate hain, unka batter bhi fermented hota hai. Toddy palm ke sap ko ferment karke banti hai.

Q5. How do microbes help control the diseases that harmful bacteria cause?

Answer (English): Microbes produce antibiotics, which are chemicals that kill or slow the growth of other microbes. Penicillin from the mould Penicillium notatum was the first, and many more antibiotics were later purified from other microbes. These drugs made it possible to cure bacterial diseases such as plague, whooping cough, diphtheria and leprosy, which used to kill millions of people.

Hinglish: Microbes antibiotics banate hain, jo doosre microbes ko maar ya rok dete hain. Penicillium notatum se penicillin mila, baad mein doosre microbes se aur antibiotics nikle. In dawaiyon se plague, whooping cough, diphtheria aur leprosy jaise rog theek hone lage, jo pehle lakhon logon ki jaan lete the.

Q6. Name two species of fungus used in the production of antibiotics.

Answer (English): Penicillium notatum, the original source of penicillin, and Penicillium chrysogenum, the species used later for large-scale penicillin production.

Hinglish: Penicillium notatum, jisse pehli baar penicillin mila, aur Penicillium chrysogenum, jise baad mein bade scale par penicillin banane ke liye use kiya gaya.

Q7. What is sewage, and how can it be harmful?

Answer (English): Sewage is municipal waste water that contains human excreta, large amounts of organic matter and many microbes, some of them pathogens. If it is released untreated, it pollutes rivers and streams, raises the BOD of the water, kills fish and other aquatic life, and spreads water-borne diseases. The organic matter also allows disease-causing microbes to multiply.

Hinglish: Sewage city ka waste water hai jismein human excreta, organic matter aur bahut se microbes hote hain, kuch pathogens bhi. Bina treat kiye chhodne par river aur nadiyan pollute hoti hain, paani ka BOD badh jaata hai, machhliyan marti hain aur water-borne diseases phailti hain.

Q8. State one main difference between the primary and secondary stages of sewage treatment.

Answer (English): Primary treatment is physical: filtration removes floating debris and sedimentation removes grit, leaving primary sludge and an effluent. Secondary treatment is biological: the effluent is aerated in large tanks, aerobic microbes grow as flocs and consume the organic matter, and the BOD falls. The settled flocs form activated sludge.

Hinglish: Primary treatment physical hai: filtration se debris aur sedimentation se grit nikalta hai, primary sludge aur effluent bachta hai. Secondary treatment biological hai: aeration tank mein aerobic microbes flocs bana kar organic matter kha jaate hain aur BOD gir jaata hai. Neeche baithne wale flocs activated sludge bante hain.

Q9. Three water samples have BOD values of 20 mg/L, 8 mg/L and 400 mg/L.

Which is most polluted, and which sample is river water?

Answer (English): BOD shows how much organic matter the water carries, so the biggest number belongs to the dirtiest sample. The sample with 400 mg/L is untreated sewage and is the most polluted. The sample with 8 mg/L is river water, which is relatively clean. The sample with 20 mg/L is the secondary effluent from the treatment plant, cleaner than raw sewage but still carrying more organic matter than the river.

Hinglish: BOD paani ke organic matter ka measure hai, isliye sabse high value sabse polluted sample ki hoti hai. 400 mg/L wala sample untreated sewage hai aur sabse zyada polluted hai. 8 mg/L wala river water hai kyunki river relatively clean hoti hai. 20 mg/L wala secondary effluent hai, raw sewage se saaf lekin river se zyada organic load wala.

Q10. How do biofertilisers make the soil more fertile?

Answer (English): Biofertilisers are living organisms that improve the nutrient quality of soil. Rhizobium lives in the root nodules of legumes and fixes atmospheric nitrogen into organic forms the plant can use. Azotobacter and Azospirillum fix nitrogen while living free in the soil. Glomus forms mycorrhiza, and its fungal partner absorbs phosphorus from the soil and passes it to the plant. Cyanobacteria such as Anabaena and Nostoc fix nitrogen in paddy fields and add organic matter, which raises fertility.

Hinglish: Biofertilisers soil ki nutrient quality badhate hain. Rhizobium legumes ke root nodules mein rehkar nitrogen fix karta hai. Azotobacter aur Azospirillum free-living nitrogen fixers hain. Glomus mycorrhiza banata hai aur fungus soil se phosphorus lekar plant ko deta hai. Anabaena aur Nostoc paddy fields mein nitrogen fix karte hain aur organic matter badhate hain. To test how much of this stuck, take the five-question quiz below. Each answer explains the reasoning, so read the explanation even when you get it right.

Quiz: the five question check for this chapter is set from the same topics. Attempt it after the questions above, then revisit any topic page where you lost a mark.