Chemotrophs

Introduction

The chemotrophs gain their energy from the oxidation of the molecules they have in their environments. Among them, the chemoorganotrophs oxidize the organic and the chemolithotrophs oxidize the inorganic compounds. The chemotrophs indirectly use light energy i.e., they use the stored energy of the ATPs. They are also divided into chemoautotrophic and chemoheterotrophic.

• The chemoautotrophs gains energy by the chemical reactions to synthesize all the organic compound commencing carbon dioxide.

• They can use inorganic sources of energy such as essential sulfur, molecular hydrogen, ferrous iron, hydrogen sulfide, and ammonia.

• Most of them live in deep-sea vents and act as primary environmental producers. They can be bacteria, archaea, and extremophiles.

• They are classified as methanogens, reducers, nitrifiers, sulfur oxidizers, thermoacidophiles, anammox, etc.

• The chemoheterotrophs cannot fix carbon to develop their own organic compounds.

• Chemoheterotrophs can be chemolithoheterotrophs by using inorganic sources of electrons and chemoorganoheterotrophs by using organic electron sources like carbohydrates, protein, and fat.

• They can thrive energy by oxidizing inorganic compounds and are able to sustain different life forms depending on the carbon source of the organism.

• They are the most abundant heterotrophs e.g. bacteria, fungi, protozoa, etc.

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Definition: Chemotrophs

Chemotrophs are organisms acquiring energy by oxidizing the organic and inorganic electron donor that exists in their surroundings e.g. bacteria. They break down the compounds by chemosynthesis. Chemosynthesis is the main metabolism category of chemotrophs. During their metabolism, the carbon and methane are transformed into organic compounds by the oxidation of hydrogen derivatives.

The chemotrophic bacteria help in the oxidation of iron and manganese.

• The iron-oxidizing bacteria convert the ferrous (Fe²⁺) ion to the ferric (Fe³⁺) form to acquire energy. This energy decreases the respiratory chain and synthesizes ATP by forwarding electron transport reaction and NADH by reverse transport. It enhances the traditional version of phototropism.

• The iron-oxidizing bacteria are mainly found in lava beds or in hydrothermal active areas where most of the ferrous iron concentrates. Oceans are devoid of iron due to dissolved oxygen’s oxidative effects and iron-consuming bacteria.

• Lava beds or newly developed igneous rocks supply ferrous iron to the bacteria and the reaction probably occurs in the upper ocean due to oxygen abundance.

• The weathering of the rocks is dependent on the biotic and abiotic factors or maybe some specialized enzymes that help bring FeO to the surface.

• The dissolved iron released from the hydrothermal vents, allows the bacteria to grow in their specific temperature niche and coexists in the deep ocean.

• They also provide a large food source to the deep sea ecosystems.

• The manganese-oxidizing bacteria converts the manganous (Mn²⁺) form to the manganic (Mn⁴⁺) form.

• Though manganese is inadequate than iron in the crust, it is easily extracted by bacteria. It gives two electrons rather than one from the iron.

• The synthesis of ATP and NADH is based on the amount of Gibbs free energy changes during oxidation. It also varies different concentrations and Ph, etc.

Chemoautotrophic Bacteria

• The chemoautotrophic bacteria obtain energy from the oxidizing compounds.

• These bacteria break the chemical bonding or oxidize the inorganic compounds such as ammonia, nitrates, nitrites, and iron (Fe²⁺) and gain energy.

• They do not use light energy but use the chemical energy stored in the ATP.

• This energy then helps in carbon assimilation.

• Basically, they break the bonds to acquire energy. The ammonia/nitrogen, sulfur, and iron bacteria are chemoautotrophic. Example − Thiothrix splits the bond of hydrogen sulfide to separate the sulfate and water content. These develop energy in the body by breaking the strong bond.

• These compounds and energy are further used for the basic functioning of the cell.

• They also help to recycle the nutrients such as sulfur, phosphorus, hydrogen, iron, nitrogen, etc.

• Examples: Nitrosomonas, Nitrobacter, Nitrococcus, Thiobacillus thioxidans, Ferrobacillus, and Lepothrix etc.

What is Auto Chemoautrophic Nutrition?

• The term auto chemoautrophic explains that the chemoautotrophic organisms are not dependent on another organism for food and nutrition. They produce their own food through some biochemical reactions to acquire energy.

• Primarily, the inorganic compounds synthesize various organic compounds containing carbon.

• Finally, the chemical reactions of the cell use the energy to develop carbon dioxide.

• These carbon compounds fulfil their nutritional demands.

Chemoautotrophs process

• Chemoautotrophs fix carbon dioxide to synthesize their own food or organic molecules.

• They obtain energy by oxidizing the inorganic sulfur, iron, and magnesium. Thus, the energy helps them in this process.

• They can able to deal with and flourish in very harsh conditions of the environments due to their independent nature, as they do not need to depend on other carbon sources other than carbon dioxide.

• They include the bacteria fixing nitrogen in the soil, oxidizing iron in lava beds, and oxidizing sulfur in thermal sea vents (deep sea).

Conclusion

The chemotrophs are organisms that acquire energy from the oxidation of both organic and inorganic compounds. They use chemical reactions instead of light energy. They are two types’ chemoautotrophs and chemoheterotrophs. The chemoautotroph can produce their own organic compounds but the chemoheterotrophs are dependent on each other to acquire energy. They gain energy from the energy stored in the ATP. They also use inorganic and organic electron-donor elements such as sulfur, nitrogen, hydrogen, manganese, iron, etc.

FAQs

Q1. Define extremophiles.

Ans. Extremophiles are organisms that can survive in extremely challenging environmental conditions such as salinity, highest or lowest pH level, temperature, radiation, etc. They are the most abundant and dominant life forms on the planet.

Q2. What is chemosynthesis?

Ans. In 1897, Wilhelm Pfeffer postulated the term chemosynthesis which defines oxidation of inorganic molecules with the help of autotrophy. The term has been changed into chemolithoautotrophy now.

Q3. State the characteristics of the thermoacedophilic organisms.

Ans.

• They are extremophilic microbes.

• Both thermophilic and acidophilic.

• Grow under low pH (<2) and high temperature (>80°C).

• Found in hot springs, solfataric environments, or hot volcanic gases covered by rocky areas, deep sea vents, or other geothermally active areas.

• Having aerobic or microaerophilic metabolism (archaea).

• Obligatory anaerobic.

• Adapted by horizontal gene transfer (archaea and bacteria).

Q4. How do the bacteria fix nitrogen in the soil?

Ans. Many plants are unable to fix their personal nitrogen, necessary for their daily life. So, they need nitrogen-fixing bacteria in the soil. Nitrogen is important for crops to grow. The legume plants form nodules in their root to form a symbiotic relationship with the nitrogen-fixing bacteria.

• The bacteria convert the natural free nitrogen to ammonia and other nitrogenous compounds.

• The usable compounds dissolve in the soil and are then absorbed by the plants.

• These legume plants replenish the nitrogen in the soil.