Rethinking Sediment Biogeochemistry After the Discovery of Electric Currents

Nielsen, Lars Peter; Risgaard-Petersen, Nils

doi:10.1146/annurev-marine-010814-015708

Cited by 99 publications

(93 citation statements)

References 39 publications

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“…Cable bacteria were observed to stop gliding when in contact with oxygen and to glide when there was little or no oxygen available. This behavior is highly suggestive of oxygen chemotaxis and agrees with previous observations of cable bacterial activity in photosynthetic mats (10). Gliding motility and oxygen chemotaxis are common among other filamentous sulfide-oxidizing bacteria to effectively position them in gradient environments (25,27,28).…”

Section: ϫ6supporting

confidence: 89%

“…How they solve the problem of coordinating their movement in order to span the gap between oxygen and sulfide remains to be shown. Cable bacteria greatly influence sediment habitats (10,29), and insight into their motility and behavior helps explain previous experimental observations and sheds light on cable bacterial function in the environment, increasing our understanding of the cable bacterium's ecological role.…”

Section: ϫ6mentioning

confidence: 95%

“…Cable bacterium succession in incubations of homogenized sediment exposed to oxygen has a general pattern of fast growth to a peak population density followed by a decline (9,10). The depth distribution of cable bacteria matches the increasing separation between oxygen and pore water sulfide, and FISH and DAPI (4=,6-diamidino-2-phenylindole) staining show chromosomes in division or separation stages throughout the cable bacteria, suggesting that cells other than just apical cells are actively dividing and have to be moved actively to extend the filaments downwards (9).…”

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confidence: 99%

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Motility of Electric Cable Bacteria

Bjerg

Damgaard

Holm

et al. 2016

Appl Environ Microbiol

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Cable bacteria are filamentous bacteria that electrically couple sulfide oxidation and oxygen reduction at centimeter distances, and observations in sediment environments have suggested that they are motile. By time-lapse microscopy, we found that cable bacteria used gliding motility on surfaces with a highly variable speed of 0.5 ؎ 0.3 m s ؊1 (mean ؎ standard deviation) and time between reversals of 155 ؎ 108 s. They frequently moved forward in loops, and formation of twisted loops revealed helical rotation of the filaments. Cable bacteria responded to chemical gradients in their environment, and around the oxic-anoxic interface, they curled and piled up, with straight parts connecting back to the source of sulfide. Thus, it appears that motility serves the cable bacteria in establishing and keeping optimal connections between their distant electron donor and acceptors in a dynamic sediment environment. IMPORTANCEThis study reports on the motility of cable bacteria, capable of transmitting electrons over centimeter distances. It gives us a new insight into their behavior in sediments and explains previously puzzling findings. Cable bacteria greatly influence their environment, and this article adds significantly to the body of knowledge about this organism.

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Section: ϫ6supporting

confidence: 89%

Section: ϫ6mentioning

confidence: 95%

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confidence: 99%

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Motility of Electric Cable Bacteria

Bjerg

Damgaard

Holm

et al. 2016

Appl Environ Microbiol

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“…The observed FeS depletion in the top 4 cm in March shows that cable bacteria also induce strong FeS dissolution in the field, and we speculate that the depletion of the sedimentary FeS stock (Fig. 4A) may have limited the electron donor supply, causing the demise of the cable bacteria population in late spring (30). Cable Bacteria in Seasonally Hypoxic Systems and Euxinia.…”

Section: Resultsmentioning

confidence: 83%

Cable bacteria generate a firewall against euxinia in seasonally hypoxic basins

Seitaj

Schauer

Sulu-Gambari

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

148

236

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Seasonal oxygen depletion (hypoxia) in coastal bottom waters can lead to the release and persistence of free sulfide (euxinia), which is highly detrimental to marine life. Although coastal hypoxia is relatively common, reports of euxinia are less frequent, which suggests that certain environmental controls can delay the onset of euxinia. However, these controls and their prevalence are poorly understood. Here we present field observations from a seasonally hypoxic marine basin (Grevelingen, The Netherlands), which suggest that the activity of cable bacteria, a recently discovered group of sulfur-oxidizing microorganisms inducing long-distance electron transport, can delay the onset of euxinia in coastal waters. Our results reveal a remarkable seasonal succession of sulfur cycling pathways, which was observed over multiple years. Cable bacteria dominate the sediment geochemistry in winter, whereas, after the summer hypoxia, Beggiatoaceae mats colonize the sediment. The specific electrogenic metabolism of cable bacteria generates a large buffer of sedimentary iron oxides before the onset of summer hypoxia, which captures free sulfide in the surface sediment, thus likely preventing the development of bottom water euxinia. As cable bacteria are present in many seasonally hypoxic systems, this euxiniapreventing firewall mechanism could be widely active, and may explain why euxinia is relatively infrequently observed in the coastal ocean. sediment biogeochemistry | cable bacteria | coastal hypoxia | sulfur cycling | microbial competition

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“…(B) Concept of electron conductors in the shared outer cell envelope of multicellular Desulfobulbaceae filaments. Modified fromNielsen and Risgaard-Petersen (2014) andRisgaard-Petersen, Damgaard, Revil, and Nielsen (2014).…”

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confidence: 99%