Characterisation of respiratory capabilities of newly isolated iron-reducing bacteria strains

Iron-reducing bacteria are microorganisms that are suitable for application in various industries, including environmental activities. These bacteria play a prime role in the natural iron transformation. The capabilities to generate energy by reducing metal and non-metal allowed iron-reducing bacteria to sustain their lives under anaerobic conditions. This research aims to characterize the capabilities of the newly isolated iron-reducing bacteria strains E. coli KP 19 and K pneumoniae KP 20 previously isolated from Kuantan Port marine sediment and B. licheniformis EPSK 21 previously isolated from South China sediment to respire on metal and non-metal electron acceptors. The anaerobic growth of the newly isolated iron-reducing bacteria strains on different electron acceptors (ferric citrate and nitrate), as well as the ability to utilise lactate as electron donor, were tested. The growths of all newly isolated iron-reducing bacteria were compared to Shewanella oneidensis MR-1 as positive control and E. coli EC 1 OOD as a negative control. The strain is identified via a biochemical test (ferrozine and nitrite assay). E. coli KP 19 and K pneumoniae KP 20 strains were able to couple the oxidation of lactate while reducing iron (III) under anaerobic conditions. On the other hands, the growth was observed with nitrate as an electron acceptor and lactate as the electron donor for all the three strains. The ferrozine assay and nitrite assay revealed that the E. coli KP19 resulted in an iron reduction. Results of anaerobic growth trials showed all the strains able to be Fe (III) reduction.
Keyword: Iron reducing bacteria, anaerobic conditions, biochemical tests.