Chemolithotrophs, it is a significant group of bacteria which have such as extreme nutritional adaptation that they neither required sunlight nor organic nutrients.
Chemolithotrophs utilize the energy present in chemical compounds and carbon in the form of carbon dioxide.
Chemolithotrophic bacteria are very important to the biogeochemical cycling of various elements. These include organism like, Beggiatoa (it utilize hydrogen sulfide as energy source), Nitrosomonas (utilizing ammonia as energy source), Thiobacillus (utilizing iron), Nitrobacter (using nitrites) etc.
So far, found these microorganisms have simpler nutritional requirements and can be grown on defined media.
These microorganisms are the chief concern to man because all the parasites or pathogens of man, animals and plants are chemoheterotrophs. All the sporophytes are also chemoheterotrophs.
Chemolithotrophs fall into four groups with respect to their energy source:
- Hydrogen bacteria: oxidize hydrogen gas.
- Sulphur bacteria: oxidize hydrogen sulfide.
- Iron bacteria: oxidize reduced forms of iron.
- Nitrifying bacteria: include two groups of bacteria – one oxidized ammonia, forming nitrate, and the other oxidize nitrite, forming nitrate.
Chemolithotrophs derive energy in diverse and rather amazing way. In simple words, they remove electrons from inorganic substrates such as hydrogen gas, hydrogen sulfide, sulphur or iron and combine them with carbon dioxide and hydrogen. This reaction provides simple organic molecules and a modest amount of energy to drive the synthetic process of the cell.
The chemolithotrophs extract electrons from an inorganic energy source and then use the electrons to generate ATP by oxidative phosphorylation. Molecular oxygen serves as the terminal electron acceptor. The amount of energy gained in metabolism depends on the energy source and the terminal electron acceptor.