Award: OCE-1756877

This project investigated the ecological role of marine Cable Bacteria (Ca. Electrothrix) in marine and estuarine sediments, with a focus on their interactions with other microorganisms. We aimed to identify microorganisms whose growth is enhanced by cable bacteria, examine metabolic processes linked with cable bacteria activity, and test specific metabolic connections using stable isotope approaches. We first established the ecological context of cable bacteria in our study system, the Chesapeake Bay, through a year-round field study. Our work confirmed Ca. Electrothrix as a prominent member of surface sediment communities in this complex oxygen stressed eutrophic system. Cable bacteria exhibited noted seasonality, enriched in winter and especially proliferating in early spring, and they exhibited strong niche partitioning with other sulfur oxidizing bacteria in sediments, with particularly high abundance in the seasonally anoxic main channel.

We investigated interactions with cable bacteria through experimental manipulations in the laboratory. Through a time course experiment, we were able to identify four modes of interactions with cable bacteria, including predation and competition, and two different potential modes of cooperation. We conducted stable isotope labelling experiments, while controlling the activity of cable bacteria, to confirm relationships between the growth of cable bacteria and the activity of associated microbes. We found that cable bacteria were capable of stimulating the growth and activity of other chemoautotrophic bacteria at depth in sediments, which is not explainable by conventional understanding of chemoautotrophic activity. Our findings substantiate the role for Cable bacteria to serve as ecosystem engineers in coastal marine sediments, and lends further support to the hypothesis that these bacteria may be serving as electron acceptors in sediments. The project supported the training of three graduate students as highly qualified personnel. We engaged with the public through fun interactive demonstrations at the Horn Point Laboratory. Our findings have been disseminated through publications in Limnology and Oceanography and Environmental Microbiology, and presented at international conferences in the fields of marine sciences and microbiology.

Last Modified: 04/18/2025
Modified by: Sairah Malkin