Answer the following three parts concisely (about 2–3 lines each):
Answer
(a) *Aspergillus niger* (b) *Trichoderma* is a fungus, not a bacterium; it acts as a biocontrol agent (antifungal), not as an antibiotic producer in the industrial sense. (c) *Bacillus thuringiensis* (Bt) is used as a biocontrol agent against insect pests such as the cotton bollworm; *Bacillus subtilis* is used for soil remediation and is not the primary Bt insecticide strain. (d) True. Methanogens are anaerobic bacteria that yield methane.
Step-by-step solution
- Part (a): Remember that citric acid (used as E330 in Indian beverages like Thums Up, Limonata, etc.) is industrially produced by fermenting molasses or sugar solutions using the filamentous fungus *Aspergillus niger*. This is explicitly stated in the NCERT table under 'Molecules of industrial importance'.
- Part (b): *Trichoderma* is a genus of **fungi** (Basidiomycota/Ascomycota), not bacteria. NCERT lists it under biocontrol agents because it acts as a broad-spectrum **antifungal** agent, protecting plant roots from soil-borne fungi such as *Fusarium* and *Rhizoctonia*.
Common mistake: Students often confuse Trichoderma (an antifungal biocontrol agent) with an antibiotic-producing microbe, or mix up Bacillus thuringiensis (insecticide) with Bacillus subtilis (soil bacterium).
Concept tested: Bioactive molecules from microbes
Published · How this solution was prepared and checked
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