Yin, H., Aller, R. C., Zhu, Q., & Aller, J. Y. (2021). The dynamics of cable bacteria colonization in surface sediments: a 2D view. Scientific Reports, 11(1), 1-8.
In 2010, Nielson and colleagues reported in Nature the existence of a new group of bacteria in marine sediments which had a previously unrecognized mode of metabolism. These microorganisms, termed cable bacteria, form multi-cellular filaments that act like wires coupling oxidation-reduction reactions between oxygen and sulfur (as sulfide) over distances of 1 – 10 cm, much like a wire connecting the cathode (+) and anode (-) poles of a battery. This discovery changed our understanding of how electrons flow in sediments and stimulated investigation of the impacts of these microorganisms on elemental cycling, for example, the remineralization of organic matter and nutrient regeneration. Up to now, no studies have demonstrated how these organisms colonize and grow in marine sediments.
Because the metabolic activity of cable bacteria (termed electrogenic) produces characteristic patterns of pH (acid / base conditions), Yin, et al (2021) (Nature: Scientific Reports) were able to use planar optical sensors to image in 2D the dynamics of cable bacteria colonization. Colonization is initiated in multiple small patches, which spread laterally and meld together on timescales of a few days to weeks, dramatically altering chemical reactions as they do so and potentially impacting ocean acidification processes (Figure). The rate of growth is determined by the availability of sulfide in sediment and oxygen in the overlying water.
Images of pH patterns in side view of sediment – water vertical section (like looking at the side of an ant-farm) illustrating the initiation of cable bacteria activity and spread. One end of filaments (cathode) consumes protons, raising the pH (blue) at the sediment surface, and the other end produces protons, lowering pH (dark red) at depth. White arrows point to sites of initiation at different times.
