Publications

3843

The taxonomic positions of members within the family Pseudonocardiaceae were assessed based on phylogenomic trees reconstructed using core-proteome and genome blast distance phylogeny approaches. The closely clustered genome sequences from the type strains of validly published names within the family Pseudonocardiaceae were analysed using overall genome-related indices based on average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values. The family Pseudonocardiaceae consists of the type genus Pseudonocardia , as well as the genera Actinoalloteichus , Actinocrispum , Actinokineospora , Actinomycetospora , Actinophytocola , Actinopolyspora , Actinorectispora , Actinosynnema , Allokutzneria , Allosaccharopolyspora gen. nov., Amycolatopsis , Bounagaea , Crossiella , Gandjariella , Goodfellowiella , Haloactinomyces , Haloechinothrix , Halopolyspora , Halosaccharopolyspora gen. nov., Herbihabitans , Kibdelosporangium , Kutzneria , Labedaea , Lentzea , Longimycelium , Prauserella , Saccharomonospora , Saccharopolyspora , Saccharothrix , Salinifilum , Sciscionella , Streptoalloteichus , Tamaricihabitans , Thermocrispum , Thermotunica and Umezawaea . The G+C contents of the Pseudonocardiaceae genomes ranged from 66.2 to 74.6 mol% and genome sizes ranged from 3.69 to 12.28 Mbp. Based on the results of phylogenomic analysis, the names Allosaccharopolyspora coralli comb. nov., Halosaccharopolyspora lacisalsi comb. nov. and Actinoalloteichus caeruleus comb. nov. are proposed. This study revealed that Actinokineospora mzabensis is a heterotypic synonym of Actinokineospora spheciospongiae , Lentzea deserti is a heterotypic synonym of Lentzea atacamensis , Prauserella endophytica is a heterotypic synonym of Prauserella coralliicola , and Prauserella flava and Prauserella sediminis are heterotypic synonyms of Prauserella salsuginis . This study addresses the nomenclature conundrums of Actinoalloteichus cyanogriseus and Streptomyces caeruleus as well as Micropolyspora internatus and Saccharomonospora viridis .

Two strains of filamentous, colorless sulfur bacteria were isolated from bacterial fouling in the outflow of hydrogen sulfide-containing waters from a coal mine (Thiothrix sp. Ku-5) and on the seashore of the White Sea (Thiothrix sp. AS). Metagenome-assembled genome (MAG) A52 was obtained from a sulfidic spring in the Volgograd region, Russia. Phylogenetic analysis based on the 16S rRNA gene sequences showed that all genomes represented the genus Thiothrix. Based on their average nucleotide identity and digital DNA-DNA hybridization data these new isolates and the MAG represent three species within the genus Thiothrix with the proposed names Thiothrix subterranea sp. nov. Ku-5T, Thiothrix litoralis sp. nov. AST, and “Candidatus Thiothrix anitrata” sp. nov. A52. The complete genome sequences of Thiothrix fructosivorans QT and Thiothrix unzii A1T were determined. Complete genomes of seven Thiothrix isolates, as well as two MAGs, were used for pangenome analysis. The Thiothrix core genome consisted of 1,355 genes, including ones for the glycolysis, the tricarboxylic acid cycle, the aerobic respiratory chain, and the Calvin cycle of carbon fixation. Genes for dissimilatory oxidation of reduced sulfur compounds, namely the branched SOX system (SoxAXBYZ), direct (soeABC) and indirect (aprAB, sat) pathways of sulfite oxidation, sulfur oxidation complex Dsr (dsrABEFHCEMKLJONR), sulfide oxidation systems SQR (sqrA, sqrF), and FCSD (fccAB) were found in the core genome. Genomes differ in the set of genes for dissimilatory reduction of nitrogen compounds, nitrogen fixation, and the presence of various types of RuBisCO.

UCYN-A is one of the most widespread and important marine diazotrophs. Its unusual distribution in both cold/warm and coastal/oceanic waters challenges current understanding about what drives the biogeography of diazotrophs. This study assessed the community assembly processes of the nitrogen-fixing cyanobacterium UCYN-A, developing a framework of assembly processes underpinning the microbial biogeography and diversity. High-throughput sequencing and a qPCR approach targeting the nifH gene were used to investigate three tropical seas: the Bay of Bengal, the Western Pacific Ocean, and the South China Sea. Based on the neutral community model and two types of null models calculating the β-nearest taxon index and the normalized stochasticity ratio, we found that stochastic assembly processes could explain 66–92% of the community assembly; thus, they exert overwhelming influence on UCYN-A biogeography and diversity. Among the deterministic processes, temperature and coastal/oceanic position appeared to be the principal environmental factors driving UCYN-A diversity. In addition, a close linkage between assembly processes and UCYN-A abundance/diversity/drivers can provide clues for the unusual global distribution of UCYN-A.

During the 1960s, small quantities of radioactive materials were co-disposed with chemical waste at the Little Forest Legacy Site (LFLS, Sydney, Australia). The microbial function and population dynamics in a waste trench during a rainfall event have been previously investigated revealing a broad abundance of candidate and potentially undescribed taxa in this iron-rich, radionuclide-contaminated environment. Applying genome-based metagenomic methods, we recovered 37 refined archaeal MAGs, mainly from undescribed DPANN Archaea lineages without standing in nomenclature and ‘Candidatus Methanoperedenaceae’ (ANME-2D). Within the undescribed DPANN, the newly proposed orders ‘Ca. Gugararchaeales’, ‘Ca. Burarchaeales’ and ‘Ca. Anstonellales’, constitute distinct lineages with a more comprehensive central metabolism and anabolic capabilities within the ‘Ca. Micrarchaeota’ phylum compared to most other DPANN. The analysis of new and extant ‘Ca. Methanoperedens spp.’ MAGs suggests metal ions as the ancestral electron acceptors during the anaerobic oxidation of methane while the respiration of nitrate/nitrite via molybdopterin oxidoreductases would have been a secondary acquisition. The presence of genes for the biosynthesis of polyhydroxyalkanoates in most ‘Ca. Methanoperedens’ also appears to be a widespread characteristic of the genus for carbon accumulation. This work expands our knowledge about the roles of the Archaea at the LFLS, especially, DPANN Archaea and ‘Ca. Methanoperedens’, while exploring their diversity, uniqueness, potential role in elemental cycling, and evolutionary history.

Huanglongbing (HLB) disease, also known as citrus greening disease, was first reported in the US in 2005. Since then, the disease has decimated the citrus industry in Florida, resulting in billions of dollars in crop losses and the destruction of thousands of acres of citrus groves. The causative agent of citrus greening disease is the phloem limited pathogen Candidatus Liberibacter asiaticus. As it has not been cultured, very little is known about the structural biology of the organism. Liberibacter are part of the Rhizobiaceae family, which includes nitrogen-fixing symbionts of legumes as well as the Agrobacterium plant pathogens. To better understand the Liberibacter genus, a closely related culturable bacterium (Liberibacter crescens or Lcr) has attracted attention as a model organism for structural and functional genomics of Liberibacters. Given that the structure of lipopolysaccharides (LPS) from Gram-negative bacteria plays a crucial role in mediating host-pathogen interactions, we sought to characterize the LPS from Lcr. We found that the major lipid A component of the LPS consisted of a pentaacylated molecule with a β-6-GlcN disaccharide backbone lacking phosphate. The polysaccharide portion of the LPS was unusual compared to previously described members of the Rhizobiaceae family in that it contained ribofuranosyl residues. The LPS structure presented here allows us to extrapolate known LPS structure/function relationships to members of the Liberibacter genus which cannot yet be cultured. It also offers insights into the biology of the organism and how they manage to effectively attack citrus trees.