Index >> Bacterial Nutrition >> Obligate Chemolithotrophs

Several differences have, however, been found with respect to sensitivity to these compounds between different obligate chemolithotrophs. In some cases a compound toxic to one species may actually be stimulatory for others. Thus valine inhibits the growth of Thiobacillus thioxitans and nitrifying bacteria, but stimulates the growth of T. thioparus. The concentrations required for inhibitions also differ from organism to organism. Toxicity of certain amino acids to obligate chemolithotrophs can be reversed by other organic acids, or by balancing the amino acid mixture.

Under normal conditions,  significant oxidation of NADH through the respiratory chain may not occur. This may contribute towards obligate chemolithotrophy in these bacteria. Organic compounds cannot replace CO2 as the major carbon source because of the fundamental deficiency in metabolizing these compounds. The contributory factors appear to be. : (1) absence of a complete Krebs cycle (The enzyme ά-ketoglutarate dehydrogenase is not present;