Microbiologically influencedcorrosion(MIC)potentialof halophilic(salt-loving) microorganismshave gained increased interests in recent years due to the expansion of industrial operations in saline environments i.e. shale. Survey of multiple shale reservoirsacross the continent revealeda number of recurring taxa shared by many geological formations, includingmembers of the generaHalomonas, Halanaerobium, Methanohalophilus and membersof the orderDesulfovibrionales. In this paper, MIC potential of pure halophilic strains was evaluated and compared withmixed microbial communitiesat high salinity. Results showed that the MICpotential of the pure nitrate-utilizingstrain Halomonas halodenitrificans was low(max: 0.144 mm/yr),but it formed a biofilm layer close to the steel surface. Whereas thehighlycorrosive sulfate-reducing bacteria Desulfovibrio ferrophilusformed a thick and compact corrosion layer at the same salinity. Results of the mixed microbial communityestablished using enrichmentsfrom a Canadian shale oil site revealed a close association between the activities of bacteriafrom the genus Halanaerobiumand the other members of the halophilic community.The data indicate the interdependencebetween the halophiles will altertheoverall MIC mechanism.

Keywords: Halophile, halophilicmicroorganism, methanogenesis, high salinity, NaCl, shale, extremophile, sulfate-reducing bacteria, nitrate-reducing bacteria, microbiologically influenced corrosion, microbially induced corrosion, MIC, Halanaerobium