Biomineralisation of manganese on titanium surfaces exposed to seawater

Abstract

A 2-year long study was carried out to isolate and characterise various bacterial species present in the biofilm formed on titanium surfaces exposed to seawater and to assess the manganese oxidizing potential of the marine isolates. The amount of manganese present in the biofilm was also measured using atomic absorption spectrometry (AAS). The results showed that titanium was susceptible to biofouling. More than 50% of the culturable marine bacterial isolates were capable of bringing about oxidation of Mn(II). All these manganese oxidizing bacteria were heterotrophic. Autotrophic manganese oxidizing bacteria such as Leptothrix was not isolated in the present study. The AAS results confirmed that the manganese content in the biofilms increased with increasing exposure time. Hence, the study indicates that the titanium surfaces when exposed to seawater were colonised by a large number of heterotrophic bacteria, which have the ability of bringing about biomineralisation of manganese.

Keywords:

• titanium
• seawater
• biomineralisation
• biofilm
• heterotrophic bacteria
• manganese oxidizing bacteria
• Pseudomonas spp.
• Bacillus spp.

Acknowledgements

The authors are grateful to Dr V.S. Raghunathan, former Associate Director, Materials Characterization Group and Dr Baldev Raj, Director, Indira Gandhi Centre for Atomic Research, Kalpakkam, for their encouragement, valuable discussions and keen interest in the study. The financial assistance extended to this work from the IGCAR-IISc collaboration programme is also acknowledged.