CBSE Questions for Class 12 Medical Biology Microbes In Human Welfare Quiz 11 - MCQExams.com

• Antibiotics are commonly classified into bactericidal and bacteriostatic agents based on their antimicrobial action. 
  
• Ofloxacin is a synthetic bactericidal antibiotic that kills bacteria in the body. 
• Erythromycin, tetracycline, and chloramphenicol are bacteriostatic antibiotics.
• Bacteriostatic antibiotics are able to limit the growth of bacteria.
  

• The source of ethanol for industrial use was from the fermentation of sugars by yeast (Saccharomyces cerevisiae). 
• Statins are blood cholesterol-lowering agents extracted from rice that's been fermented with a type of yeast called Monascus purpureus. Red yeast rice is a traditional Chinese medicine that has been used to lower cholesterol. 
• Trichoderma is used as an immunosuppressant prescribed in organ transplants to prevent rejection. 
• There are three primary types of bacteria that are used to make Swiss cheese: Streptococcus thermophilus; Lactobacillus helveticus; and Propionibacterium shermanii. It is this Propionibacterium shermanii that is responsible for the holes in Swiss cheese.  

• Camembert is a soft and creamy type of cheese. Penicillium camemberti is a species of fungus that form colonies on these cheese which forms a hard and white coloured crust. 
• This leads to the ripening of the cheese. 
• The fungus is responsible for giving the cheese a particular type of taste.

The order of bacteria active in the conversion of organic wastes into biogas is hydrolytic, acetogenic, methanogenic. 

Hydrolytic- Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives which are used by bacteria.

Acetogenic- Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. These bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide.

Methanogenic- The methanogens convert the product of acetogenic step to methane and carbon dioxide. The produced gas consisting of methane, carbon dioxide, and traces of other ‘contaminant’ gases is known as biogas.

So, the correct answer is 'Hydrolytic $$\rightarrow$$ Acetogenic $$\rightarrow$$ Methanogenic'.

• Cheese is one of the oldest milk products prepared with the help of microbes.
• Dosa, Upma are fermented preparation of rice and black gram. 
• The two are allowed to ferment for 3-12 hours with air-borne Leuconostoc and Streptococcus species of bacteria. 
• Toddy is a traditional drink of some parts of South India which is made by fermentation of sap of palms.

A.Correct option B

B.Explanation for the correct option: 

• Trichoderma harzianum is an effective biocontrol agent against several fungal soil-borne plant pathogens. 
• They have an inhibitory effect on the growth of the mycelium of Phytium. 
• They suppress the growth of fungi in order to allow the plant to grow favourably.
  
• However, possible adverse effects of T. harzianum on plant growth-promoting microorganisms, such as arbuscular mycorrhiza (AM) fungi, might be a drawback in the use of this biocontrol agent in plant protection.