Question

List and discuss the metabolic diversity of microorganisms. Ex: Chemoheterotrophs (USLO 3.1)

List and describe organic molecules important in metabolism. (USLO 3.2)

Answer 1

Photoautotrophs and Photoheterotrophs

Photoautotrophs and photoheterotrophs are those organisms that rely on the light as their main source of energy to carry out cellular processes.

Photoautotrophs

An autotroph is an organism which is able to make its own food. Photoautotrophs are the organisms that carry out photosynthesis. Using energy from the sunlight, carbon dioxide and water are converted into organic materials that are used in cellular functions such as biosynthesis and respiration. In an ecological context, they provide all the nutrition for other forms of life (besides autotrophs such as chemotrophs ). In the terrestrial environments plants, are the predominant variety, while in aquatic environments there is a range of phototrophic organisms such as algae, protists, and bacteria.

Photoheterotrophs

A heterotroph is an organism which depends on the organic matter already produced by the other organisms for their nourishment. Photoheterotrophs can obtain their energy from the sunlight and carbon from the organic material . Most of the well-recognized phototrophs are autotrophs,and are also known as the photoautotrophs, and can fix carbon on earth.

Chemoautotrophs

Chemoautotrophs are those who are able to synthesize their own organic molecules from the fixation of carbon dioxide. These organisms can produce their own source of food, or energy. The energy required for these process come from oxidation of the inorganic molecules like iron, sulfur and magnesium. Chemoautotrophs van thrive in very harsh environments, like deep sea vents etc.

Chemoheterotrophs

Chemoheterotrophs, are unable to synthesize their own organic molecules. Instead of this, these organisms must ingest premade carbon molecules, in the form of carbohydrates and lipids, synthesized by other organisms. They do, however, still they obtain their energy from oxidation of inorganic molecules like chemoautotrophs.

2. The important molecules ,needed by autotrophs found only in bacteria are inorganic compounds which are oxidized directly (without using sunlight) to yield the energy (e.g., NH₃, NO₂^–, S₂, and Fe²⁺). This metabolism mode may also require the energy for CO₂ reduction, like photosynthesis, but no lipid-mediated process are involved by them. This mode of metabolism has also been called chemoautotrophy, or chemolithotrophy.