Oxygen consumption of individual cable bacteria

Abstract

The electric wires of cable bacteria possibly support a unique respiration mode with a few oxygen-reducing cells flaring off electrons, while oxidation of the electron donor and the associated energy conservation and growth is allocated to other cells not exposed to oxygen. Cable bacteria are centimeter-long, multicellular, filamentous Desulfobulbaceae that transport electrons across oxic-anoxic interfaces in aquatic sediments. From observed distortions of the oxic-anoxic interface, we derived oxygen consumption rates of individual cable bacteria and found biomass-specific rates of unheard magnitude in biology. Tightly controlled behavior, possibly involving intercellular electrical signaling, was found to generally keep <10% of individual filaments exposed to oxygen. The results strengthen the hypothesis that cable bacteria indeed have evolved an exceptional way to take the full energetic advantages of aerobic respiration and let >90% of the cells metabolize in the convenient absence of oxidative stress.

Imaging the oxygen wave with a single bioluminescent bacterium

“…According to three-dimensional diffusion model (l 2 = 6Dt), 39 the diffusion coefficient (D) was determined to be ~2.0×10 -9 m 2 /s, which was consistent with the literature reports. 40,41 It is clear now that the time-lapsed BL images of a bacteria monolayer provide an efficient way to visualize the dynamic distribution of oxygen.…”

Cable bacteria at oxygen‐releasing roots of aquatic plants: a widespread and diverse plant–microbe association

“…The observations that the abundance of cable bacteria cells decreased at the sites where cable bacteria would source the oxygen (endosphere compared with the outside of rice root; at the root tip of seagrass compared with the root hair region) is in accordance with observations from cable bacteria in nonvegetated sediments. In these sediments less than one‐tenth of each filament is in the oxic zone (Scilipoti et al ., 2021 ) and most of the cable bacteria cells are located in the reduced sediment layer below the oxic surface (Schauer et al ., 2014 ; van de Velde et al ., 2016 ).…”

Phyllobacterium calauticae sp. nov. isolated from a microaerophilic veil transversed by cable bacteria in freshwater sediment

“…Oxic-anoxic interfaces (OAIs) are present in all environments where oxygen is consumed faster than replenished, such as aquatic sediments, and are home to microbial communities that are well adapted to micro-oxic conditions (Brune et al, 2000;Thar & Kühl, 2002;Thar & Fenchel, 2005). These communities frequently form a microaerophilic veil right at the OAI, with oxygen completely depleted behind the veil (Thar & Fenchel, 2005;Scilipoti et al, 2021). Specific low concentrations of oxygen are actively sought out by the microorganisms, which indicates chemotaxis towards the preferred oxygen concentration (Barbara & Mitchell, 1996;Thar & Fenchel, 2005).…”

“…They spatially separate their metabolic redox half reactions by transporting electrons from sulfide oxidation to the oxic surface sediment, where oxygen is reduced (Pfeffer et al, 2012), and thus create a suboxic zone up to several centimetres wide (Schauer et al, 2014). While sulfide and oxygen never directly meet in these zones, microaerophilic veils form along the OAI of cable bacteria-induced suboxic zones (Bjerg et al, 2016;Scilipoti et al, 2021). This suggests that organisms in these microaerophilic veils use electron donors other than sulfide.…”