Chapter 10: Microbes in Human Welfare

Ans: Option (b) is the answer. Flocs are bacterial swarms that bind together with fungal filaments to produce a mesh-like structure. The rate of breakdown of organic materials in activated sludge flocs will be slowed if oxygen availability is restricted. As the centre of the flocs becomes anoxic, the bacterial cells die, resulting in floc rupture.

Ans: Option (d) is the answer. Mycorrhizae aids the host plant in increasing its phosphorus absorption capability and drought tolerance. Mycorrhiza generates compounds that protect against pathogens such as Fusarium. As a result, the correct answer is 'increasing its insect resistance.'

Ans: Option (d) is the answer. Pseudomonas is a bacterium that does not fix nitrogen. Pseudomonas is a bacterium that lives in the soil as a saprophyte. Pseudomonas is utilized to degrade organic pollutants such as petroleum spills.

Ans: Option (c) is the answer. During fermentation, a bacteria called Propionibacterium sharmanii creates a lot of carbon dioxide. This is why Swiss cheese has many holes.

Ans: Option (c) is the answer. The residue left after methane production from cattle dung is used as manure. Biogas is a methane-rich fuel gas generated by anaerobic digestion of biomass using methanogenic bacteria.

Ans: Option (a) is the answer. Methanogens are obligate anaerobes, meaning that they create methane, hydrogen sulphide, and carbon dioxide but not oxygen.

Ans: Option (a) is the answer. To be pumped back to the aeration tank, the activated sludge must settle quickly. 'Be rapidly pumped back from the sedimentation tank to the aeration tank' is the proper choice.

Ans: Option (b) is the answer. The ladybird beetle is a biological pest control agent for aphids. Glomus is a genus of arbuscular mycorrhizal fungus that creates a mycorrhizal symbiotic association with plant roots. Trichoderma is a biological control agent used to combat pathogenic fungus of several species. Biogas is made up of methane, which is produced by methanobacterium.