Publications

4870

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.

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 .

AbstractAmmonia-oxidizing archaea (AOA) are recently found to participate in the ammonia removal processes in wastewater treatment plants (WWTPs), similar to their bacterial counterparts. However, due to lack of cultivated AOA strains from WWTPs, their functions and contributions in these systems remain unclear. Here we report a novel AOA strain SAT1 enriched from activated sludge, with its physiological and genomic characteristics investigated. The maximal 16S rRNA gene similarity between SAT1 and other reported AOA strain is 96% (with “Ca. Nitrosotenuis chungbukensis”), and it is affiliated with Wastewater Cluster B (WWC-B) based on amoA gene phylogeny, a cluster within group I.1a and specific for activated sludge. Our strain is autotrophic, mesophilic (25 °C–33 °C) and neutrophilic (pH 5.0–7.0). Its genome size is 1.62 Mb, with a large fragment inversion (accounted for 68% genomic size) inside. The strain could not utilize urea due to truncation of the urea transporter gene. The lack of the pathways to synthesize usual compatible solutes makes it intolerant to high salinity (>0.03%), but could adapt to low salinity (0.005%) environments. This adaptation, together with possibly enhanced cell-biofilm attachment ability, makes it suitable for WWTPs environment. We propose the name “Candidatus Nitrosotenuis cloacae” for the strain SAT1.