Photoferrotrophs thrive in an Archean Ocean analogue

Sean A. Crowe, Carri Ayne Jones, Sergei Katsev, Cedric Magen, Andrew H. O'Neill, Arne Sturm, Donald E. Canfield, G. Douglas Haffner, Alfonso Mucci, Bjørn Sundby, David A. Fowle

Research output: Contribution to journalArticlepeer-review

157 Scopus citations

Abstract

Considerable discussion surrounds the potential role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce (<20 μmol·liter -1), and it is completely removed by sulfate reduction within the deep, Fe(II)-rich chemocline. The sulfide produced is efficiently scavenged by the formation and precipitation of FeS, thereby maintaining very low sulfide concentrations within the chemocline and the deep ferruginous bottom waters. Low productivity in the surface water allows sunlight to penetrate to the >100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lake's euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity.

Original languageEnglish (US)
Pages (from-to)15938-15943
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number41
DOIs
StatePublished - Oct 14 2008

Keywords

  • Anoxygenic photosynthesis
  • Banded iron formation
  • Green sulfur bacteria
  • Iron oxidation
  • Lake matano

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