Question

Chemosynthetic bacteria obtain energy from
(a) Sun
(b) Infra-red rays
(c) Organic substances
(d) Inorganic chemicals.

Answer 1

 Hint: Chemosynthetic bacteria include a group of autotrophic bacteria that produce their food by oxidizing certain substances. Like photosynthetic bacteria, to grow their food, chemosynthetic bacteria require a carbon source (e.g. carbon dioxide) as well as an energy source.

Complete Step by Step Answer: Chemosynthetic bacteria obtain energy for the synthesis of food by oxidizing certain inorganic substances like ammonia, nitrates, nitrites, ferrous ions, etc. Due to their ability to generate their food using chemical energy, these organisms can live as free- living organisms or in association with other organisms (through symbiosis with other organisms) in a variety of habitats/environments (including harsh environments with extreme conditions).
The energy is then used in the carbon assimilation with the help of hydrogen from some source other than water, e.g., Hydrogen bacteria, nitrifying bacteria, sulfur bacteria, etc. They play a great role in recycling nutrients like nitrogen, phosphorus, iron, sulfur.
- Hydrogen bacteria: In microaerophilic environments, bacteria such as Hydrogen Vibrio marinus and Helicobacter pylori oxidize hydrogen as a source of energy. These bacteria are anaerobic for the most part and thus survive in regions with very little to no oxygen. This is largely due to the fact that in anaerobic environments, the enzyme used for oxidation purposes (hydrogenase) acts effectively.
- Nitrifying bacteria: Nitrifying bacteria, denitrifying bacteria, and nitrogen- fixing bacteria are subdivided into three classes. In the case of nitrifying bacteria, ammonia in the cytoplasm is first oxidized into hydroxylamine. The hydroxylamine is then oxidized in the cell cytoplasm by hydroxylamine oxidoreductase to create nitrite. A proton is produced by this process (one proton for each ammonium molecule). In contrast to nitrifying bacteria, nitrate compounds are oxidized by denitrifying bacteria as an energy source. For e.g., Nitrosomonas, Nitrobacter, and Nitrocystis.
- Sulphur bacteria: These bacteria oxidize such compounds of sulphur as thiosulfates of hydrogen sulfide (sulfides) and inorganic sulphur, etc. The oxidation process takes place in many phases depending on the individual, or the form of a sulfur compound being used. For e.g., Thiobacillus thiooxidans, Beggiatoa.
- Iron bacteria: Some of the bacteria causes iron oxidation. Depending on the organism (e.g. low pH and oxic anoxic) , this procedure has been shown to occur under distinct conditions. E.g., Ferrobacillus, Leptothrix.
So, the answer is ‘Inorganic chemicals.’

Note:   - These bacteria are aerobic and thus depend on oxygen to successfully complete this process. However, some species have been identified with anaerobic chemosynthesis (e.g. Sulfuricurvum kujiense). - These bacteria do not use light as the source of energy. The chemical energy thus obtained is stored in ATP molecules. - Unlike photosynthesis, which is common in eukaryotic organisms and cyanobacteria, prokaryotic microorganisms (particularly bacteria and archaea) are mostly involved in chemosynthetic reactions.