News   •   November 3, 2021

Cable bacteria are filamentous bacteria that conduct electricity across long distances (for a microbe!) in sediment and groundwater aquifers. Discovered in 2012, they are able to connect electron donors to electron acceptors, coupling physically separated oxidation and reduction reactions. In particular, cable bacteria are known to couple the reduction of oxygen or nitrate at the sediment’s surface to the oxidation of sulfide in the deeper, anoxic, sediment layers.

Cable bacteria strongly influence the geochemical properties of the surrounding environment, for example promoting the oxidation of hydrogen sulfide, which can be toxic to marine life. In search for a suitable electron acceptor, cable bacteria often associate with aquatic plants that leak oxygen from their roots (called radial oxygen loss).

In a commentary wrote together with Sairah Malkin from the University of Maryland, we discuss a recent paper by Scholz et al. (2021) investigating the distribution and specificity of the relationship between the rhizospheres of aquatic vegetation and cable bacteria.

We argue that cable bacteria, similarly to lucinid clams and their chemosynthetic symbionts, may also engage in a facultative mutualism with seagrasses and other aquatic vegetation. Further, we highlight that, given the ubiquity of facilitative interactions with microbes in a variety of aquatic plants, we have to explore their role in underpinning ecosystem functioning if we are to protect aquatic plant ecosystems and the provision of services that they deliver to humans.

Here the link to the paper, which was published today in the New Phytologist.

Ecological parallels between lucinid clams with their sulfur-oxidizing gill symbionts and cable bacteria. There are multiple nested facilitative interactions possible between the thiotrophic communities and aquatic plants. Key potential interactions are highlighted in the inset. DOC, dissolved organic carbon; DIN, dissolved inorganic nitrogen. Seagrass symbol from Integration and Application Network (ian.umces.edu/media-library).