# Microbes, Disease and Health for UPSC: Vectors, Viruses, Antimicrobial Resistance, Probiotics, Biofilms and Wolbachia Source: https://tracknation.in/story/microbes-disease-and-health-for-upsc-vectors-viruses-antimicrobial-resistance-probiotics-biofilms-and-wolbachia (TrackNation β€” free UPSC notes with PYQs) > Microbes and health for UPSC: pathogens, diseases and vectors, viruses and culture media, antimicrobial resistance, probiotics and useful microbes, biofilms, the Wolbachia method, aerial metagenomics, nitric oxide and TB genomics. Includes practice questions and the real PYQs. ## How UPSC Tests Microbes and Health 🎯 **Exam priority: Tier-1/2. Microbes and health questions mix textbook disease facts with 'in the news' techniques.** *UPSC asked: what viruses can infect (2016); how plant diseases spread (2018); the reasons for multi-drug resistance in India and the statement about Hepatitis B and C (2019); which organisms grow on artificial media (2021); biofilms and probiotics (2022); the Wolbachia method and aerial metagenomics (2023); the gas the body makes that dilates blood vessels (2024); and viruses in oceans, bacteria and host cells (2025).* Three boxes: **who causes what and how it spreads**, **useful microbes** and **the newer ideas** (biofilms, resistance, Wolbachia, eDNA). ## Pathogens, Diseases and Vectors ## Pathogens, diseases and vectors | **Group** | **Disease and organism** | **Key facts** | | Bacteria | Typhoid (*Salmonella typhi*); pneumonia (*Streptococcus pneumoniae*, *Haemophilus influenzae*) | Typhoid is confirmed by the Widal test; 'Typhoid Mary' was a carrier. Pneumonia fills the alveoli with fluid. Dysentery, plague and diphtheria are other bacterial diseases | | Viruses | Common cold (rhinoviruses); AIDS (HIV); dengue and chikungunya (Aedes mosquitoes); Hepatitis B and C | A cold infects the nose and respiratory passage but not the lungs. Hepatitis B spreads through blood and body fluids much like HIV; it has a vaccine (Hepatitis C does not) and both can stay silent for years | | Protozoa | Malaria (*Plasmodium*); amoebiasis (*Entamoeba histolytica*) | The female *Anopheles* mosquito is the vector; sporozoites enter, multiply in the liver, then burst red blood cells, releasing haemozoin that causes recurring chills and fever. *P. falciparum* causes the most serious (malignant) malaria | | Helminths | Ascariasis (*Ascaris*); filariasis or elephantiasis (*Wuchereria*) | Filarial worms are transmitted by female mosquitoes and affect the lymphatic vessels | | Fungi | Ringworm (*Microsporum*, *Trichophyton*, *Epidermophyton*) | Thrive in heat and moisture; spread by soil, towels and combs | - **Viruses infect every kind of cell:** bacteriophages attack bacteria, other viruses infect fungi and many infect plants (2016 PYQ). Oceans are full of viruses, and many viruses change the gene activity of their host cells (2025 PYQ: all three of its 'no virus can' statements were wrong). - **Culture:** bacteria and fungi grow on artificial media; viruses need living host cells, so they cannot be cultured on a synthetic medium (2021 PYQ). - **Plant diseases** spread through birds, dust, rain splash and wind, so all four routes count (2018 PYQ). - **Vector control:** avoid stagnant water, use nets and wire mesh, spray insecticides and introduce *Gambusia* fish that feed on mosquito larvae. Smallpox has been eradicated and polio, diphtheria and tetanus largely controlled by vaccines. ## Useful Microbes ## Useful microbes - **Lactic acid bacteria** (*Lactobacillus*) turn milk into curd and help check disease-causing microbes in the gut. **Probiotics** are live bacteria and yeasts (such as *Saccharomyces*) that help digest milk sugar; the same organisms occur naturally in the gut, so the claim that they do not occur there is wrong (2022 PYQ). - **Medicines:** penicillin, the first antibiotic, was a chance discovery by Alexander Fleming from the mould *Penicillium*; streptokinase from *Streptococcus* breaks blood clots; cyclosporin A (from a fungus) is an immunosuppressant; statins (from yeast) lower blood cholesterol. - **Sewage treatment:** microbes break down organic matter in effluent; **BOD** (biochemical oxygen demand) is the oxygen needed to break down the organic matter in a litre of water, so a high BOD means more pollution. - **Biogas:** methanogens such as *Methanobacterium* produce methane from dung and waste anaerobically. ## Biofilms, Resistance, Wolbachia, eDNA and How UPSC Could Ask Next ## Newer ideas in the news - **Biofilms** are communities of microbes held in a slime matrix on a surface. They form on medical implants inside tissues and on food and food-processing surfaces, and bacteria in a biofilm tolerate antibiotics far better, so all three statements in the 2022 question were right. - **Antimicrobial resistance:** microbes become resistant when antibiotics are taken in incorrect or incomplete doses and when they are used in livestock farming (2019 PYQ: statements 2 and 3). A person's genetic predisposition or chronic disease does not make the microbe resistant. Vaccines, such as pneumococcal conjugate vaccines, reduce antibiotic use. - **Wolbachia method:** *Wolbachia* bacteria introduced into *Aedes aegypti* mosquitoes make them far less able to pass on dengue, Zika and chikungunya viruses, so it is a way of controlling viral diseases spread by mosquitoes (2023 PYQ). - **Aerial metagenomics** collects the DNA suspended in the air of a habitat and sequences it, to learn in one go which species are present (2023 PYQ). - **Nitric oxide** is made in the human body, from the amino acid arginine; it relaxes blood-vessel walls and so raises blood flow (2024 PYQ). Nitrous oxide is laughing gas, and nitrogen dioxide is a pollutant. - **Genomics against TB:** the Department of Biotechnology has sequenced about 18,000 *Mycobacterium tuberculosis* isolates from new patients; lineages 2 and 4, though fewer in number, show more multi-drug resistance. ## How UPSC Could Ask This Next - **Disease-organism-vector chains:** malaria, dengue, filariasis, Kyasanur forest disease. - **Culture and structure:** which pathogens can be grown on artificial media and which need hosts. - **Resistance drivers:** misuse in people, livestock and aquaculture. - **Techniques:** Wolbachia, gene drives, eDNA, metagenomics. ## Further Reading - NCERT Biology (Class 12) and Geography textbooks, the India State of Forest Report, the MoEFCC Annual Report, the Economic Survey and the official lists cited in this note β€” the primary sources behind every figure above. ## Test Yourself: Practice Questions and PYQs Twelve practice questions on pathogens, vectors, useful microbes and the newer ideas, followed by the real UPSC Prelims questions. ## Practice Questions **Q1.** Typhoid fever is caused by - (a) Plasmodium falciparum - (b) Wuchereria bancrofti - (c) Salmonella typhi - (d) Entamoeba histolytica **Answer: (c)** β€” It is confirmed by the Widal test. **Q2.** Which of the following is the vector of the malarial parasite? - (a) Female Aedes mosquito - (b) Housefly - (c) Female Anopheles mosquito - (d) Tsetse fly **Answer: (c)** β€” Plasmodium enters the body as sporozoites through its bite. **Q3.** The recurring chills and high fever of malaria are associated with the release of - (a) histamine - (b) insulin - (c) haemozoin - (d) interferon **Answer: (c)** β€” It is released when red blood cells burst. **Q4.** Viruses can infect 1. bacteria 2. fungi 3. plants - (a) 3 only - (b) 1 and 2 only - (c) 1 and 3 only - (d) 1, 2 and 3 **Answer: (d)** β€” Bacteriophages, mycoviruses and plant viruses exist. **Q5.** Which of the following can be grown on an artificial or synthetic culture medium? 1. Bacteria 2. Fungi 3. Viruses - (a) 2 and 3 only - (b) 1 and 2 only - (c) 3 only - (d) 1, 2 and 3 **Answer: (b)** β€” Viruses need living host cells. **Q6.** Which of the following contribute to antimicrobial resistance? 1. Taking incorrect doses of antibiotics 2. Using antibiotics in livestock farming 3. A person's genetic predisposition - (a) 2 and 3 only - (b) 3 only - (c) 1, 2 and 3 - (d) 1 and 2 only **Answer: (d)** β€” Resistance arises in the microbes under antibiotic pressure. **Q7.** Which one of the following statements is NOT correct? - (a) Hepatitis B, unlike Hepatitis C, does not have a vaccine - (b) Hepatitis B virus is transmitted much like HIV - (c) Some people infected with hepatitis viruses show no symptoms for years - (d) Hepatitis B and C infect more people than HIV does **Answer: (a)** β€” A vaccine exists for Hepatitis B. **Q8.** Biofilms - (a) kill all bacteria - (b) are made only of fungi - (c) can form on medical implants and food surfaces and make bacteria more antibiotic-tolerant - (d) are formed only in the open ocean **Answer: (c)** β€” UPSC's 2022 key: all three statements were right. **Q9.** The Wolbachia method is used for - (a) producing biodegradable plastics - (b) making biochar - (c) converting crop residue into packing - (d) controlling viral diseases spread by mosquitoes **Answer: (d)** β€” Wolbachia-infected Aedes mosquitoes transmit dengue less. **Q10.** Aerial metagenomics refers to - (a) studying avian genetics only - (b) using drones to collect blood from birds - (c) collecting DNA samples from the air of a habitat at one go - (d) sending drones to collect soil samples **Answer: (c)** β€” It samples airborne environmental DNA. **Q11.** BOD (biochemical oxygen demand) is a measure of - (a) the organic matter in water, as the oxygen needed to break it down - (b) the amount of dissolved oxygen in the air - (c) the pH of water - (d) the salt content of water **Answer: (a)** β€” A higher BOD means more organic pollution. **Q12.** Which gas, made in the human body, relaxes the walls of blood vessels and increases blood flow? - (a) Nitrogen pentoxide - (b) Nitrogen dioxide - (c) Nitrous oxide - (d) Nitric oxide **Answer: (d)** β€” UPSC's 2024 key. ### UPSC Previous Year Questions (PYQs) *Real UPSC Prelims questions, checked against the official paper and answer key.* **Q1.** (2016) Which of the following statements is/are correct? Viruses can infect 1. Bacteria 2. Fungi 3. Plants Select the correct answer using the code given below. - (a) 1 and 3 only - (b) 3 only - (c) 1 and 2 only - (d) 1, 2 and 3 **Answer: (d)** β€” Viruses infect every kind of cell: bacteriophages attack bacteria, there are viruses that infect fungi and many viruses infect plants. All three. **Q2.** (2018) Consider the following: 1. Birds 2. Dust blowing 3. Rain 4. Wind blowing Which of the above spread plant diseases? - (a) 1, 2, 3 and 4 - (b) 1 and 3 only - (c) 1, 2 and 4 only - (d) 3 and 4 only **Answer: (a)** β€” Plant pathogens are carried by birds, dust, rain splash and wind, so all four spread plant diseases. **Q3.** (2019) Which of the following are the reasons for the occurrence of multi-drug resistance in microbial pathogens in India? 1. Genetic predisposition of some people 2. Taking incorrect doses of antibiotics to cure diseases 3. Using antibiotics in livestock farming 4. Multiple chronic diseases in some people Select the correct answer using the code given below. - (a) 1 and 2 only - (b) 2 and 3 only - (c) 2, 3 and 4 only - (d) 1, 3 and 4 only **Answer: (b)** β€” Taking incorrect or incomplete doses of antibiotics and using antibiotics in livestock farming push microbes to become resistant. Genetic predisposition and chronic illness in people are not causes of resistance in the microbes themselves, so statements 2 and 3. **Q4.** (2019) Which one of the following statements is not correct? - (a) Hepatitis B, unlike Hepatitis C, does not have a vaccine. - (b) Some of those infected with Hepatitis B and C viruses do not show the symptoms for many years. - (c) Globally, the number of people infected with Hepatitis B and C viruses are several times more than those infected with HIV. - (d) Hepatitis B virus is transmitted much like HIV. **Answer: (a)** β€” Hepatitis B has a vaccine (Hepatitis C does not), so statement (a) is the incorrect one. Hepatitis B spreads through blood and body fluids much like HIV, and the hepatitis viruses infect many more people than HIV and may stay silent for years. **Q5.** (2021) Consider the following: 1. Bacteria 2. Fungi 3. Virus Which of the above can be cultured in artificial/synthetic medium? - (a) 1, 2 and 3 - (b) 1 and 3 only - (c) 2 and 3 only - (d) 1 and 2 only **Answer: (d)** β€” Bacteria and fungi can be grown on artificial media in a laboratory. Viruses need living host cells (cell cultures, eggs or animals), so they cannot be cultured on an artificial medium. **Q6.** (2022) Consider the following statements: 1. Biofilms can form on medical implants within human tissues. 2. Biofilms can form on food and food processing surfaces. 3. Biofilms can exhibit antibiotic resistance. Which of the statements given above are correct? - (a) 1 and 3 only - (b) 2 and 3 only - (c) 1, 2 and 3 - (d) 1 and 2 only **Answer: (c)** β€” Biofilms form on medical implants and on food-processing surfaces, and bacteria inside a biofilm are much more tolerant of antibiotics. All three statements are right. **Q7.** (2022) Consider the following statements in respect of probiotics: 1. Probiotics are made of both bacteria and yeast. 2. The organisms in probiotics are found in foods we ingest but they do not naturally occur in our gut. 3. Probiotics help in the digestion of milk sugars. Which of the statements given above is/are correct ? - (a) 2 and 3 only - (b) 2 only - (c) 1 and 3 only - (d) 1 only **Answer: (c)** β€” Probiotics are live micro-organisms: bacteria such as Lactobacillus and yeasts such as Saccharomyces, and they help digest lactose. The same kinds of organisms occur naturally in the gut, so statement 2 is wrong. **Q8.** (2023) β€œWolbachia method' is sometimes talked about with reference to which one of the following? - (a) Producing biochar from thermochemical conversion of biomass - (b) Controlling the viral diseases spread by mosquitoes - (c) Producing biodegradable plastics - (d) Converting crop residues into packing material **Answer: (b)** β€” Wolbachia bacteria introduced into Aedes mosquitoes make them far less able to pass on dengue and other viruses, so the method is used to control mosquito-borne viral diseases. **Q9.** (2023) Aerial metagenomics' best refers to which one of the following situations? - (a) Collecting DNA samples from air in a habitat at one go - (b) Using air-borne devices to collect blood samples from moving animals - (c) Understanding the genetic makeup of avian species of a habitat - (d) Sending drones to inaccessible areas to collect plant and animal samples from land surfaces and water bodies **Answer: (a)** β€” Aerial metagenomics collects the DNA floating in the air of a habitat and sequences it, to learn which organisms are present in one go. **Q10.** (2025) Consider the following statements: 1. No virus can survive in ocean waters. 2. No virus can infect bacteria. 3. No virus can change the cellular transcriptional activity in host cells. How many of the statements given above are correct? - (a) All the three - (b) Only one - (c) Only two - (d) None **Answer: (d)** β€” Oceans are full of viruses, bacteriophages infect bacteria, and many viruses reprogramme gene activity in their host cells. All three statements are wrong, so none is correct. **Q11.** (2024) Which one of the following is synthesised in human body that dilates blood vessels and increases blood flow? - (a) Nitric oxide - (b) Nitrogen dioxide - (c) Nitrogen pentoxide - (d) Nitrous oxide **Answer: (a)** β€” Nitric oxide is a gas the body makes (from the amino acid arginine) that relaxes the walls of blood vessels and so raises blood flow. Nitrous oxide is laughing gas, and nitrogen dioxide and pentoxide are not made for this purpose. ### Mains Practice Questions Use these to frame full-length answers. You don't have to answer one exactly β€” they show the angles UPSC tests, so let them guide which points you cover. - Why is antimicrobial resistance a major public-health threat in India? Suggest a multi-sector response (people, livestock, environment). - Distinguish between a vector-borne disease and a water-borne disease with examples, and describe control measures. - What are probiotics? Evaluate their claimed benefits and the regulatory position in India. - Explain how the Wolbachia approach differs from insecticide-based vector control. - Discuss how genomics is changing the fight against tuberculosis in India. ### UPSC Mains β€” Previous Years’ Questions on this topic (last 10 years) No direct GS Mains question has been asked specifically on this topic in the last decade β€” it is primarily a **Prelims** area. Use the practice prompts above to stay exam-ready.