Microbiologically influenced corrosion (MIC) potential of halophilic (salt-loving) microorganisms have gained increased interests in recent years due to the expansion of industrial operations in saline environments i.e. shale. Survey of multiple shale reservoirs across the continent revealed a number of recurring taxa shared by many geological formations, including members of the genera Halomonas, Halanaerobium, Methanohalophilus and members of the order Desulfovibrionales.
In this paper, MIC potential of pure halophilic strains was evaluated and compared with mixed microbial communities at high salinity. Results showed that the MIC potential of the pure nitrate-utilizing strain Halomonas halodenitrificans was low (max: 0.144 mm/yr), but it formed a biofilm layer close to the steel surface. Whereas the highly corrosive sulfate-reducing bacteria Desulfovibrio ferrophilus formed a thick and compact corrosion layer at the same salinity.
Results of the mixed microbial community established using enrichments from a Canadian shale oil site revealed a close association between the activities of bacteria from the genus Halanaerobium and the other members of the halophilic community. The data indicate the interdependence between the halophiles will alter the overall MIC mechanism.
Saline environments with greater than 10% NaCl (or approximately 1.5 M NaCl which is triple the seawater salinity) such as the Great-Salt Lake, salt marshes and salt caverns1,2, are inhabited by a unique group of microorganisms, known as the halophiles or salt-loving microbes. An increased industrial exposure on the halophiles was brought upon by the exploratory activities of the energy industry, such as shale operations. Microbial community analyses of several deep surface shale reservoirs revealed high proportions of halophiles3-10, which raises many questions regarding the potential risks of the halophiles on the infrastructures.
Halophiles have evolved two basically different adaptation strategies to survive in environments with high level of salt stress2-4,11,12, namely the "salt-in-cytoplasm" mechanism and the organic osmolyte mechanism. Organisms following the "salt-in-cytoplasm" mechanism adapt the interior protein chemistry of the cell to high salt concentration by employing highly acidic intracellular protein structures to accommodate the ionic stress. Organisms of the "salt in cytoplasm" strategy can be often found in environments with salt concentrations well above 15% NaCl12.
