Nutrition: Introduction
How do microbes gain the energy they need?
In this section we will describe each type of nutrition (Autotrophy, Heterotrophy) and then consider some of the consequences of each process.
Energy can be obtained from existing sources of free energy (autotrophy) or it can come from energy rich compounds formed by other organisms (heterotrophy).
Some bacteria, all algae and some protists can photosynthesise. No fungi are known to be autotrophic.
The most common form of autotrophy is photoautotrophy (photosynthesis). Here, light energy activates an electron transport chain in a photopigment resulting in the ultimate formation of an energy rich carbon molecule. We need to realise here, that an energy rich carbon compound is formed as a result of the process. The energy rich carbon compound is more commonly referred to as an organic molecule or organic compound. Carbon dioxide is not an organic compound, methane is.
The only known chemoautotrophs are bacteria. In chemoautotrophy (chemosynthesis), energy from the oxidation of an energy rich compound activates an electron transport chain, resulting in the formation of an energy rich organic molecule.
