Microbes in Human Welfare — Important Questions

It breaks down PET plastics into terephthalic acid and ethylene glycol using PETase and MHETase enzymes

Step 1: Plastic pollution is a major environmental concern. PET (polyethylene terephthalate) is one of the most common plastics used in bottles and packaging. Step 2: Ideonella sakaiensis was identified as a bacterium capable of breaking down PET plastic, making it valuable for bioremediation. Step 3: It uses two specific enzymes – PETase (breaks PET into MHET) and MHETase (breaks MHET into simpler monomers) – to convert PET into terephthalic acid and ethylene glycol, which can be recycled. Step 4: Option A describes Pestalotiopsis microspora, a fungus that degrades polyurethane. Option C is i

Solubilisation → Acidogenesis → Methanogenesis

Step 1: In a biogas plant, organic matter undergoes anaerobic digestion in a specific sequence of three stages. Step 2: Stage 1 – Solubilisation: Complex organic molecules (carbohydrates, proteins, fats) are broken down into simpler soluble compounds by hydrolytic bacteria. Step 3: Stage 2 – Acidogenesis: The simpler compounds are further broken down into organic acids (acetic acid, propionic acid) and alcohols by acidogenic bacteria. Step 4: Stage 3 – Methanogenesis: Methanogenic bacteria (like Methanobacterium) convert the organic acids into methane (CH₄) and carbon dioxide (CO₂), which cons

Citric acid – Aspergillus niger; Butyric acid – Clostridium butyricum

Step 1: Many organic acids are commercially produced using specific microorganisms. Step 2: The correct pairings from the chapter are: Citric acid → Aspergillus niger (a fungus), Acetic acid → Acetobacter aceti (a bacterium), Fumaric acid → Rhizopus oryzae (a fungus), Butyric acid → Clostridium butyricum (a bacterium), Lactic acid → Lactobacillus (a bacterium). Step 3: Option A is wrong because it swaps Rhizopus oryzae (fumaric acid) with Aspergillus niger (citric acid). Step 4: Option B is wrong – acetic acid is produced by Acetobacter aceti, not Lactobacillus, and butyric acid is by Clostrid

Streptomycin, isolated from Streptomyces griseus

Step 1: Selman Waksman was a soil microbiologist who coined the term 'antibiotic' in 1943. Step 2: He discovered streptomycin, which was isolated from the actinomycetes bacterium Streptomyces griseus. Step 3: Streptomycin is a broad-spectrum, bactericidal antibiotic effective against both gram-positive and gram-negative bacteria, especially Mycobacterium tuberculosis (which causes TB). Step 4: Option A is wrong – penicillin was discovered by Alexander Fleming from Penicillium fungi, not by Waksman. Option C is wrong – tetracycline (chlortetracycline) was isolated from Streptomyces aureofaciens