Polyamine patterns in iron- and sulphur-oxidizing bacteria isolated from an Indian copper mine indicate requirement of spermidine for growth under acid conditions

Spermidine was found to be the predominant polyamine in all the acidophilic as well as neutrophilic strains of chemolithotrophic iron- and sulphur-oxi dizing bacteria and associated organotrophic cultures inhabiting a copper m ining ecosystem. Adaptation of neutrophilic Thiobacillus thioparus strain t o pH 5.0 was found to increase the spermidine content of the cells 2.3 time s while the biomass yield decreased by 50%. However, exogenous supplementat ion of spermidine could restore the biomass yield to levels obtainable at p H 7.0. These observations indicate that spermidine plays a significant role in adaptive behaviour of microorganisms in natural ecosystems, especially under acid conditions.