On the growth kinetics of oral and environmental sulfate-reducing bacteria (SRB) in aerobic and anaerobic conditions

Abstract

Biocorrosion is a process induced by microorganisms such as sulfate-reducing bacteria (SRB), which are able to reduce sulfate to sulfide under different environmental conditions. Such biocorrosive ability renders these microorganisms highly important on a biotechnological scope. However, few studies have addressed the cultivation and behavior of Desulfovibrio sp. in laboratory conditions. We therefore aimed to describe the growth kinetics of Desulfovibrio desulfuricans (oral and environmental strains) and D. fairfieldensis, in aerobic and anaerobic conditions. Three strains were manipulated in a glovebox-type controlled atmosphere chamber, which allowed for cultivation under anaerobic conditions in modified Postgate E culture medium without agar-agar and Postgate C culture medium without agar-agar. Strains were grown in the same culture media under aerobic conditions, within a laminar flow hood. After adaptation, cultures were incubated at 30 °C for 147 h in an automatic microplate reader. Plates were shaken for 3 s on an hourly-basis and their absorbance was read at the 590-nm wavelength using software Gen5TM. In parallel, we evaluated SRB growth in modified Postgate culture medium without agar-agar by assessing iron sulfide formation. The strain D. fairfieldensis grew on both culture medium types, in both conditions. The other strains showed variation in the applied conditions, with divergences in readings of the growth curve being observed with iron sulfide formation in the modified Postgate E culture medium without agar-agar. The occurrence of growth in a culture medium specific to Desulfovibrio sp. in an aerobic environment suggests that these bacteria may be facultative anaerobic or aerotolerant, and not strict, as previously reported in most studies. Thus, such trait suggests that there is no restriction to these bacteria in anaerobic environments, and they therefore may be able to move across different niches of the oral cavity with different oxygen concentrations.