. Sun light-Photoautotrophs . Inorganic compounds by oxidation-Chemoautotrophs 2. Heterotrophs: Parasitic bacteria require more complex organic compounds as their source of carbon and energy. Human pathogenic bacteria are heterotrophs. The principal source of carbon is carbohydrate which are degraded either by oxidation, in the presence of oxygen, or by fermentation, in the absence of oxygen, to provide energy in the form of ATP.
Hydrogen and oxygen
Obtained from water.
Essential for the growth and maintenance of cell.
Constitutes 10% of dry weight of bacterial cell.
Obtained from organic molecules like proteins and inorganic
molecules like ammonium salts and nitrates. NB: Main source of nitrogen is ammonia, in the form of ammonium salt.
Growth factors are organic compounds that are required by micro- organisms in small amounts which the cell can not synthesize from other carbon source. These are aminoacids, purines and pyrimidines, and vitamins. Prototrophs: Wild-type bacteria with normal growth requirements. Auxotrophs: Mutant bacteria, which require an additional growth factor not needed by the parental or wild type strain.