Project description:The deep marine subsurface is one of the largest unexplored biospheres on Earth, where members of the phylum Chloroflexi are abundant and globally distributed. However, the deep-sea Chloroflexi have remained elusive to cultivation, hampering a more thorough understanding of their metabolisms. In this work, we have successfully isolated a representative of the phylum Chloroflexi, designated strain ZRK33, from deep-sea cold seep sediments. Phylogenetic analyses based on 16S rRNA genes, genomes, RpoB and EF-tu proteins indicated that strain ZRK33 represents a novel class within the phylum Chloroflexi, designated Sulfochloroflexia. We present a detailed description of the phenotypic traits, complete genome sequence and central metabolisms of the novel strain ZRK33. Notably, sulfate and thiosulfate could significantly promote the growth of the new isolate, possibly through accelerating the hydrolysis and uptake of saccharides. Thus, this result reveals that strain ZRK33 may play a crucial part in sulfur cycling in the deep-sea environments. Moreover, the putative genes associated with assimilatory and dissimilatory sulfate reduction are broadly distributed in the genomes of 27 metagenome-assembled genomes (MAGs) from deep-sea cold seep and hydrothermal vents sediments. Together, we propose that the deep marine subsurface Chloroflexi play key roles in sulfur cycling for the first time. This may concomitantly suggest an unsuspected availability of sulfur-containing compounds to allow for the high abundance of Chloroflexi in the deep sea.
Project description:Dimethylsufoniopropionate (DMSP) is an important and abundant organic sulfur compound and an important substrate for marine bacterioplankton. The Roseobacter clade of marine alpha-proteobacteria, including Silicibacter pomeroyi strain DSS3, are known to be a key phylogenetic group involved in DMSP degradaton. The fate of DMSP has important implications for the global sulfur cycle, but the genes involved in this process and their regulation are largely unknown. S. pomeroyi is capable of performing two major pathways of DMSP degradation, making it an interesting model organism. Based on the full genome sequence of this strain we designed an oligonucleotide-based microarray for the detection of transcripts of nearly all genes. The array was used to study the transcriptional response of S. pomeroyi cultures to additions of DMSP or Acetate in a time series experiment. We identified a number of DMSP-upregulated genes that could be assigned to potential roles in the metabolization of DMSP. DMSP also affected the transcription of other groups of genes, including genes for transport and metabolization of peptides, amino-acids and polyamines. High DMSP concentrations may be a chemical signal indicating phytoplankton abundance and elicit a regulatory response aimed at making maximum use of the available nutrients under these conditions. Keywords: Microarray, marine bacterium, messenger RNA, transcription, sulfur metabolism The array design is based on the complete genome sequence of S. pomeroyi strain DSS 3 and available from Genbank (Accession numbers CP000031 and CP000032). Probes for all identified potential genes were designed by Combimatrix using proprietary software. A total of 4161 genes out of the 4348 identified potential genes on the S. pomeroyi genome are represented on the array. When possible, two probes per gene were designed.
Project description:(from abstract): Iron oxidation is a desirable trait of biomining microorganisms, although the mechanism is not well-understood in extreme thermoacidophiles. The complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula DSM 5348 (2.2 Mb, ~2300 ORFs) provides insights into biologically catalyzed metal sulfide oxidation. Comparative genomics was used to identify pathways and proteins (in)directly involved with bioleaching. As expected, the M. sedula genome encodes genes related to autotrophic carbon fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin, involved in iron oxidation. The fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus, could also be identified. These iron-oxidizing components are missing from genomes of non-leaching Sulfolobales like Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole genome transcriptional response analysis showed that 88 ORFs were up-regulated 2-fold or more in M. sedula upon addition of ferrous sulfate to yeast extract-based medium; these included components of terminal oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of the iron and sulfur metabolism of M. sedula remain to be identified and characterized. Keywords: substrate response
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organism’s high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria.
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organism’s high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria.