| Endospore-forming thermophilic bacteria (thermospores) have been repeatedly detected in
permanently cold marine environments that do not favor their metabolic activity. Thermospores in
the cold seabed may be explained by a dispersal history originating in warm subsurface habitats
like oil reservoirs, where the natural seepage of fluids transports viable cells from oil reservoirs
into the overlying ocean. Previously, incubation experiments heating hydrocarbon seep sediments
from the Eastern Gulf of Mexico at 50 °C successfully identified several seep-associated
thermospore lineages dispersed from high-temperature petroleum reservoirs. In our study, we
investigated the activity and diversity of thermospores in deep sea sediments from GoM locations
subjected to different seepage conditions, including hydrocarbons, brine, both hydrocarbon and
brine, as well as non-seep sites using multiple high-temperature anoxic incubation experiments at
35 °C, 50 °C, and 65 °C followed by 16S rRNA gene amplicon sequencing. Our findings showed
that some bacterial classes and genera were restricted to particular temperatures and location types;
for instance, Desulfitobacteriia was observed only at 35 °C and only in hydrocarbon seep
sediments. Moreover, more diverse bacterial classes and genera were observed in hydrocarbon
seep locations compared to brine and non-seeps. This provided evidence that these bacterial taxa
are exclusive to particular incubation temperatures and site types, emphasizing the importance of
incubation experiments and comparative study of different locations at multiple temperatures
covering a wide thermophilic range for the discovery of novel microbes that were not detected
before in that location at 50 °C.
Keywords: Diversity, hydrocarbon, incubation, temperature, thermospore |