Publications

4748

Summary Multicellular magnetotactic prokaryotes ( MMPs ) are a peculiar group of magnetotactic bacteria, each comprising approximately 10–100 cells of the same phylotype. Two morphotypes of MMP have been identified, including several species of globally distributed spherical mulberry‐like MMPs (s‐ MMPs ), and two species of ellipsoidal pineapple‐like MMPs (e‐ MMPs ) from C hina ( Q ingdao and R ongcheng cities). We recently collected e‐ MMPs from M editerranean S ea sediments ( S ix‐ F ours‐les‐ P lages) and D rummond I sland, in the S outh C hina S ea. Phylogenetic analysis revealed that the MMPs from S ix‐ F ours‐les‐ P lages and the previously reported e‐ MMP C andidatus   M agnetananas rongchenensis have 98.5% sequence identity and are the same species, while the MMPs from D rummond I sland appear to be a novel species, having > 7.1% sequence divergence from the most closely related e‐ MMP , C andidatus   M agnetananas tsingtaoensis. Identification of the novel species expands the distribution of e‐ MMPs to T ropical Z one. Comparison of nine physical and chemical parameters revealed that sand grain size and the content of inorganic nitrogen (nitrate, ammonium and nitrite) in the sediments from R ongcheng C ity and S ix‐ F ours‐les‐ P lages were similar, and lower than found for sediments from the other two sampling sites. The results of the study reveal broad diversity and wide distribution of e‐ MMPs .

Abstract Previous studies on enhanced biological phosphorus removal (EBPR) have focused on reconstructing genomic blueprints for the model polyphosphate-accumulating organism Candidatus Accumulibacter phosphatis. Here, a time series metatranscriptome generated from enrichment cultures of Accumulibacter was used to gain insight into anerobic/aerobic metabolism and regulatory mechanisms within an EBPR cycle. Co-expressed gene clusters were identified displaying ecologically relevant trends consistent with batch cycle phases. Transcripts displaying increased abundance during anerobic acetate contact were functionally enriched in energy production and conversion, including upregulation of both cytoplasmic and membrane-bound hydrogenases demonstrating the importance of transcriptional regulation to manage energy and electron flux during anerobic acetate contact. We hypothesized and demonstrated hydrogen production after anerobic acetate contact, a previously unknown strategy for Accumulibacter to maintain redox balance. Genes involved in anerobic glycine utilization were identified and phosphorus release after anerobic glycine contact demonstrated, suggesting that Accumulibacter routes diverse carbon sources to acetyl-CoA formation via previously unrecognized pathways. A comparative genomics analysis of sequences upstream of co-expressed genes identified two statistically significant putative regulatory motifs. One palindromic motif was identified upstream of genes involved in PHA synthesis and acetate activation and is hypothesized to be a phaR binding site, hence representing a hypothetical PHA modulon. A second motif was identified ~35 base pairs (bp) upstream of a large and diverse array of genes and hence may represent a sigma factor binding site. This analysis provides a basis and framework for further investigations into Accumulibacter metabolism and the reconstruction of regulatory networks in uncultured organisms.

Abstract“Candidatus Achromatium palustre” was recently described as the first marine representative of the Achromatium spp. in the Thiotrichaceae - a sister lineage to the Chromatiaceae in the Gammaproteobacteria. Achromatium spp. belong to the group of large sulfur bacteria as they can grow to nearly 100 μm in size and store elemental sulfur (S0) intracellularly. As a unique feature, Achromatium spp. can accumulate colloidal calcite (CaCO3) inclusions in great amounts. Currently, both process and function of calcite accumulation in bacteria is unknown, and all Achromatium spp. are uncultured. Recently, three single-cell draft genomes of Achromatium spp. from a brackish mineral spring were published, and here we present the first draft genome of a single “Candidatus Achromatium palustre” cell collected in the sediments of the Sippewissett Salt Marsh, Cape Cod, MA. Our draft dataset consists of 3.6 Mbp, has a G + C content of 38.1 % and is nearly complete (83 %). The next closest relative to the Achromatium spp. genomes is Thiorhodovibrio sp. 907 of the family Chromatiaceae, containing phototrophic sulfide-oxidizing bacteria.