Inhibitory microbial activity and GC-MS based metabolite profile of the halophilic cyanobacterium Aphanothece halophytica
Metabolites levels provide significant insights into the understanding of their biochemical action. GC-MS provides semi-quantitative information pertaining to numerous different chemical analytes depending upon the biological material. Aphanothece halophytica is a halotolerant cyanobacterium that can survive in extremes of salinity up to 3M NaCl and synthesizes betaine as the major osmoprotectant. In this study, metabolism was arrested by lyophilisation of the cell mass which was collected by centrifugation. Freeze-thaw cycles were employed in the extraction methods to facilitate cell permeabilization. The crude extract exhibited bioactivity against Gram positive S. aureus and Gram negative E. coli and P. aeruginosa and also against freshwater cyanobacteria namely A. fertilissima, N. commune and C. majus. Crude extracts from the cyanobacterium identified through GC-MS showed an abundance of long chain hydrocarbons with phytol and alkaloid derivatives in small amounts, in addition to fatty acids and sugars. The activity could largely be attributed to the volatile organic compounds found in the extract. This emphasizes the bioactive potential of the cyanobacterium and consistent with the earlier findings on the toxic/inhibitory activity of the crude extract of Aphanothece halophytica, on mice, bacteria and cyanobacteria, the halotolerant cyanobacterium is a reservoir of bioactive metabolites, which could be of economic and industrial significance.