Microbial Communities in Hydrothermal Sediments Assimilate Varied Carbon Sources

Research conducted by the University of Minnesota has revealed that microbial communities in hydrothermal sediments of the Guaymas Basin exhibit a wide range of carbon assimilation, including detrital organic matter, DIC of hydrothermal and water column origin, methane, light alkanes, and petroleum hydrocarbons. The study analyzed the abundances and 13C-isotopic values of these carbon pools and compared them with the d13C-isotopic composition of bacterial and archaeal rRNA. The results indicate that carbon from 13C-depleted methane permeates the microbial food web, with no systematic preference for bacteria or archaea. However, the presence of detrital organic matter of photosynthetic origin complicates the interpretation of methane signals in bacterial and archaeal d13C-rRNA values.

Key Takeaways:

• Microbial communities in hydrothermal sediments of Guaymas Basin assimilate a wide range of carbon sources, including detrital organic matter, DIC of hydrothermal and water column origin, methane, light alkanes, and petroleum hydrocarbons.
• Carbon from 13C-depleted methane permeates the microbial food web, with no systematic preference for bacteria or archaea.
• The presence of detrital organic matter of photosynthetic origin means that any methane signal in bacterial and archaeal d13C-rRNA values is diluted by the heterotrophic background.
• Under alkane-rich conditions, consistent differences between bacterial and archaeal alkane assimilation pathways are observed.
• The study highlights the complexity of carbon cycling in hydrothermal sediments and the need for more detailed research on the microbial communities involved.

Statistics:

• The study analyzed 13C-isotopic values of carbon pools in hydrothermal sediments.
• The data showed that d13C-rRNA values for bacterial and archaeal rRNA are lighter (more 13C-depleted) than those of TOC and DIC in almost all hydrothermal sediments.
• In non-hydrothermal background sediment, d13C-rRNA values for bacterial and archaea are heavier (less 13C-depleted) and indicate the preferential utilization of detrital TOC of photosynthetic origin.
• The study found that the availability of different sedimentary or hydrothermal carbon sources, particularly hydrothermal methane, is reflected in changing d13C-rRNA values for bacteria and archaea.

Sources:

• Tracing microbial carbon sources in hydrothermal sediments by 13C isotopic analysis of bacterial and archaeal ribosomal RNA. Frontiers in Microbiology, 2025,16.
• https://doi-org.sdpl.idm.oclc.org/10.3389/fmicb.2025.1680337
• University of Minnesota, Department of Earth Sciences, Minneapolis, MN, United States.