217 000-year-old DNA sequences of green sulfur bacteria in Mediterranean sapropels and their implications for the reconstruction of the paleoenvironment

ABSTRACT The Black Sea is the largest extant anoxic water body on Earth. Its oxic-anoxic boundary is located at a depth of 100 m and is populated by a single phylotype of marine green sulfur bacteria. This organism, Chlorobium sp. strain BS-1, is extraordinarily low light adapted and can therefore serve as an indicator of deep photic zone anoxia (A. K. Manske, J. Glaeser, M. M. M. Kuypers, and J. Overmann, Appl. Environ. Microbiol. 71:8049-8060, 2005). In the present study, two sediment cores were retrieved from the bottom of the Black Sea at depths of 2,006 and 2,162 m and were analyzed for the presence of subfossil DNA sequences of BS-1 using ancient-DNA methodology. Using optimized cultivation media, viable cells of the BS-1 phylotype were detected only at the sediment surface and not in deeper layers. In contrast, green sulfur bacterial 16S rRNA gene fragments were amplified from all the sediment layers investigated, including turbidites. After separation by denaturing gradient gel electrophoresis and sequencing, 14 different sequence types were distinguished. The sequence of BS-1 represented only a minor fraction of the amplification products and was found in 6 of 22 and 4 of 26 samples from the 2,006- and 2,162-m stations, respectively. Besides the sequences of BS-1, three additional phylotypes of the marine clade of green sulfur bacteria were detected. However, the majority of sequences clustered with groups from freshwater habitats. Our results suggest that a considerable fraction of green sulfur bacterial chemofossils did not originate in a low-light marine chemocline environment and therefore were likely to have an allochthonous origin. Thus, analysis of subfossil DNA sequences permits a more differentiated interpretation and reconstruction of past environmental conditions if specific chemofossils of stenoec species, like Chlorobium sp. strain BS-1, are employed.

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Origin and Evolution of Photosystems: Lessons from Green Sulfur Bacteria

ChemPhotoChem ◽

10.1002/cptc.202100019 ◽

2021 ◽

Author(s):

Guillaume Tcherkez ◽

Nicolas Papon

Keyword(s):

Green Sulfur Bacteria ◽

Origin And Evolution ◽

Sulfur Bacteria ◽

Green Sulfur

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Novel green sulfur bacteria phylotypes detected in saline environments: ecophysiological characters versus phylogenetic taxonomy

Antonie van Leeuwenhoek ◽

10.1007/s10482-010-9420-x ◽

2010 ◽

Vol 97 (4) ◽

pp. 419-431

Author(s):

Xavier Triadó-Margarit ◽

Xavier Vila ◽

Charles A. Abella

Keyword(s):

Green Sulfur Bacteria ◽

Saline Environments ◽

Phylogenetic Taxonomy ◽

Sulfur Bacteria ◽

Green Sulfur

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Signature pigments of green sulfur bacteria in lower Pleistocene deposits from the Banyoles lacustrine area (Spain)

Journal of Paleolimnology ◽

10.1007/s10933-005-3731-3 ◽

2005 ◽

Vol 34 (2) ◽

pp. 271-280 ◽

Cited By ~ 16

Author(s):

N. Mallorquí ◽

J.B. Arellano ◽

C.M. Borrego ◽

L.J. Garcia-Gil

Keyword(s):

Green Sulfur Bacteria ◽

Sulfur Bacteria ◽

Lower Pleistocene ◽

Green Sulfur

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Differential RNA Sequencing Implicates Sulfide as the Master Regulator of S 0 Metabolism in Chlorobaculum tepidum and Other Green Sulfur Bacteria

Applied and Environmental Microbiology ◽

10.1128/aem.01966-17 ◽

2017 ◽

Vol 84 (3) ◽

Cited By ~ 1

Author(s):

Jacob M. Hilzinger ◽

Vidhyavathi Raman ◽

Kevin E. Shuman ◽

Brian J. Eddie ◽

Thomas E. Hanson

Keyword(s):

Gene Expression ◽

Elemental Sulfur ◽

Green Sulfur Bacteria ◽

Electron Donors ◽

Reduced Sulfur Compounds ◽

Promoter Elements ◽

Content Type ◽

Sulfur Bacteria ◽

Chlorobaculum Tepidum ◽

Green Sulfur

ABSTRACT The green sulfur bacteria ( Chlorobiaceae ) are anaerobes that use electrons from reduced sulfur compounds (sulfide, S 0 , and thiosulfate) as electron donors for photoautotrophic growth. Chlorobaculum tepidum , the model system for the Chlorobiaceae , both produces and consumes extracellular S 0 globules depending on the availability of sulfide in the environment. These physiological changes imply significant changes in gene regulation, which has been observed when sulfide is added to Cba. tepidum growing on thiosulfate. However, the underlying mechanisms driving these gene expression changes, i.e., the specific regulators and promoter elements involved, have not yet been defined. Here, differential RNA sequencing (dRNA-seq) was used to globally identify transcript start sites (TSS) that were present during growth on sulfide, biogenic S 0 , and thiosulfate as sole electron donors. TSS positions were used in combination with RNA-seq data from cultures growing on these same electron donors to identify both basal promoter elements and motifs associated with electron donor-dependent transcriptional regulation. These motifs were conserved across homologous Chlorobiaceae promoters. Two lines of evidence suggest that sulfide-mediated repression is the dominant regulatory mode in Cba. tepidum . First, motifs associated with genes regulated by sulfide overlap key basal promoter elements. Second, deletion of the Cba. tepidum 1277 ( CT1277 ) gene, encoding a putative regulatory protein, leads to constitutive overexpression of the sulfide:quinone oxidoreductase CT1087 in the absence of sulfide. The results suggest that sulfide is the master regulator of sulfur metabolism in Cba. tepidum and the Chlorobiaceae . Finally, the identification of basal promoter elements with differing strengths will further the development of synthetic biology in Cba. tepidum and perhaps other Chlorobiaceae . IMPORTANCE Elemental sulfur is a key intermediate in biogeochemical sulfur cycling. The photoautotrophic green sulfur bacterium Chlorobaculum tepidum either produces or consumes elemental sulfur depending on the availability of sulfide in the environment. Our results reveal transcriptional dynamics of Chlorobaculum tepidum on elemental sulfur and increase our understanding of the mechanisms of transcriptional regulation governing growth on different reduced sulfur compounds. This report identifies genes and sequence motifs that likely play significant roles in the production and consumption of elemental sulfur. Beyond this focused impact, this report paves the way for the development of synthetic biology in Chlorobaculum tepidum and other Chlorobiaceae by providing a comprehensive identification of promoter elements for control of gene expression, a key element of strain engineering.

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