Tag: microbes in human welfare

Stromatolites are layered bio-chemical structures formed in shallow water by the trapping, binding and cementation of sediments by microorganisms, especially cyanobacteria. Stromatolites provide ancient records of life on earth by fossil remains, which might date from more than 3.5 billion years ago.

Since, BGA is a prokaryotic organism, they lack true nucleus and membrane bound organelles which means that chloroplast (double membrane bound chlorophyll containing plastids) is absent in them. Thus, option B is incorrect. Chromatophores are light reflecting, pigment containing cells. The peripheral region of BGA protoplast contains thylakoids and is termed as chromoplast. Thylakoids contain photosynthetic pigments (chrolophyll a, xanthophylls, phycobilin) in their membranes and serve as site for photosynthesis. Thus, option C is correct and D is incorrect.

• Certain bacteria, which grow anaerobically on cellulosic material, produce a large amount of methane along with $CO _2$ and $H _2$. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. 
• These bacteria are present in the rumen (a part of the stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In the rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle. 
• Hence Methanobacterium feed cellulose in the anaerobic condition is a true statement.
• So, the correct answer is 'Methanobacterium feed cellulose in anaerobic condition'.

On the basis of their energy source, organisms are classified as organotrophic and lithotrophs. Most prokaryotes and all non-phototrophic eukaryotes use organic compounds as their energy source and thus, are referred to as organotrophs. They oxidise organic compounds during cellular respiration and the produced oxygen as a byproduct. But some Cyanobacteria and Archaea use inorganic compounds as an electron donor in electron transport chain and are referred to as lithotrophs, none of the eukaryotes falls in this category. Virus act as non-living outside the cell. It becomes active when it enters the host cell and derives the cellular protein from the host.

Biofertilizers are the suspension of microorganism which is formed by ploughing in legumes. They enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria (blue-green algae). Biofertilizers will help solve such problems as increased salinity of the soil and chemical run-offs from the agricultural fields.

Nitrogen is the important nutrient for plant growth. Plant obtains nitrogen from the atmosphere with the help of symbiotic and free nitrogen-fixing microorganisms. Azotobacter  is aerobic free living nitrogen fixing organism and fixes atmospheric nitrogen non-symbiotically. Therefore, all plants, trees, vegetables get benefited. Whereas VAM, Anabaena and Rhizobium are the symbiotic organisms.