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July 7, 2019  |  

Exploring structural variants in environmentally sensitive gene families.

Environmentally sensitive plant gene families like NBS-LRRs, receptor kinases, defensins and others, are known to be highly variable. However, most existing strategies for discovering and describing structural variation in complex gene families provide incomplete and imperfect results. The move to de novo genome assemblies for multiple accessions or individuals within a species is enabling more comprehensive and accurate insights about gene family variation. Earlier array-based genome hybridization and sequence-based read mapping methods were limited by their reliance on a reference genome and by misplacement of paralogous sequences. Variant discovery based on de novo genome assemblies overcome the problems arising from a reference genome and reduce sequence misplacement. As de novo genome sequencing moves to the use of longer reads, artifacts will be minimized, intact tandem gene clusters will be constructed accurately, and insights into rapid evolution will become feasible. Copyright © 2016 Elsevier Ltd. All rights reserved.


July 7, 2019  |  

Complete genome of the starch-degrading myxobacteria Sandaracinus amylolyticus DSM 53668T.

Myxobacteria are members of d-proteobacteria and are typified by large genomes, well-coordinated social behavior, gliding motility, and starvation-induced fruiting body formation. Here, we report the 10.33 Mb whole genome of a starch-degrading myxobacterium Sandaracinus amylolyticus DSM 53668(T) that encodes 8,962 proteins, 56 tRNA, and two rRNA operons. Phylogenetic analysis, in silico DNA-DNA hybridization and average nucleotide identity reveal its divergence from other myxobacterial species and support its taxonomic characterization into a separate family Sandaracinaceae, within the suborder Sorangiineae. Sequence similarity searches using the Carbohydrate-active enzymes (CAZyme) database help identify the enzyme repertoire of S. amylolyticus involved in starch, agar, chitin, and cellulose degradation. We identified 16 a-amylases and two ?-amylases in the S. amylolyticus genome that likely play a role in starch degradation. While many of the amylases are seen conserved in other d-proteobacteria, we notice several novel amylases acquired via horizontal transfer from members belonging to phylum Deinococcus-Thermus, Acidobacteria, and Cyanobacteria. No agar degrading enzyme(s) were identified in the S. amylolyticus genome. Interestingly, several putative ß-glucosidases and endoglucanases proteins involved in cellulose degradation were identified. However, the absence of cellobiohydrolases/exoglucanases corroborates with the lack of cellulose degradation by this bacteria. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.


July 7, 2019  |  

Complete genome sequence of plant growth-promoting bacterium Leifsonia xyli SE134, a possible gibberellin and auxin producer.

Leifsonia xyli SE134 is a potential plant growth-promoting bacterium isolated from a soil in Daegu, Republic of Korea, which produces large amounts of gibberellin (GA) and indole acetic acid (IAA). In this study, we sequenced the complete genome of L. xyli SE134 by the Pacific Biosciences RSII (PacBio) Single Molecule Real Time (SMRT) sequencing technology. The genome of L. xyli SE134 contains a single chromosome that is 3,596,761bp in length, with 70.2% G+C content. The genome contains 3466 protein-coding genes (CDSs) and 51 rRNA- and 46 tRNA-coding genes. By genomic analysis, we identified genes that are potentially involved in plant growth promotion such as genes participating in indole-3-acetic acid (IAA) biosynthesis, siderophore, and trehalose production. L. xyli SE134 also harbours genes for central carbohydrate metabolism, indicating that it can utilise the root exudates with other organic materials as an energy source. Furthermore, the SE134 genome is equipped with various kinds of genes for adaptation to plant surfaces, e.g. defence against desiccation, nutrient deficiencies, and oxidative stress, and a large proportion of genes related to secretion mechanisms and signalling. The genetic information provided here may help to expand this bacterium’s biotechnological potential and to further improve its plant growth-promoting characteristics. Copyright © 2016. Published by Elsevier B.V.


July 7, 2019  |  

Assembly and transfer of tripartite integrative and conjugative genetic elements.

Integrative and conjugative elements (ICEs) are ubiquitous mobile genetic elements present as “genomic islands” within bacterial chromosomes. Symbiosis islands are ICEs that convert nonsymbiotic mesorhizobia into symbionts of legumes. Here we report the discovery of symbiosis ICEs that exist as three separate chromosomal regions when integrated in their hosts, but through recombination assemble as a single circular ICE for conjugative transfer. Whole-genome comparisons revealed exconjugants derived from nonsymbiotic mesorhizobia received three separate chromosomal regions from the donor Mesorhizobium ciceri WSM1271. The three regions were each bordered by two nonhomologous integrase attachment (att) sites, which together comprised three homologous pairs of attL and attR sites. Sequential recombination between each attL and attR pair produced corresponding attP and attB sites and joined the three fragments to produce a single circular ICE, ICEMcSym(1271) A plasmid carrying the three attP sites was used to recreate the process of tripartite ICE integration and to confirm the role of integrase genes intS, intM, and intG in this process. Nine additional tripartite ICEs were identified in diverse mesorhizobia and transfer was demonstrated for three of them. The transfer of tripartite ICEs to nonsymbiotic mesorhizobia explains the evolution of competitive but suboptimal N2-fixing strains found in Western Australian soils. The unheralded existence of tripartite ICEs raises the possibility that multipartite elements reside in other organisms, but have been overlooked because of their unusual biology. These discoveries reveal mechanisms by which integrases dramatically manipulate bacterial genomes to allow cotransfer of disparate chromosomal regions.


July 7, 2019  |  

Cupriavidus malaysiensis sp. nov., a novel poly(3-hydroxybutyrate-co-4-hydroxybutyrate) accumulating bacterium isolated from the Malaysian environment.

Bacterial classification on the basis of a polyphasic approach was conducted on three poly(3 hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] accumulating bacterial strains that were isolated from samples collected from Malaysian environments; Kulim Lake, Sg. Pinang river and Sg. Manik paddy field. The Gram-negative, rod-shaped, motile, non-sporulating and non-fermenting bacteria were shown to belong to the genus Cupriavidus of the Betaproteobacteria on the basis of their 16S rRNA gene sequence analyses. The sequence similarity value with their near phylogenetic neighbour, Cupriavidus pauculus LMG3413T, was 98.5%. However, the DNA-DNA hybridization values (8-58%) and ribotyping analysis both enabled these strains to be differentiated from related Cupriavidus species with validly published names. The RiboPrint patterns of the three strains also revealed that the strains were genetically related even though they displayed a clonal diversity. The major cellular fatty acids detected in these strains included C15:0 ISO 2OH/C16:1 ?7c, hexadecanoic (16:0) and cis-11-octadecenoic (C18:1 ?7c). Their G+C contents ranged from 68.0  to 68.6 mol%, and their major isoprenoid quinone was Ubiquinone Q-8. Of these three strains, only strain USMAHM13 (= DSM 25816 = KCTC 32390) was discovered to exhibit yellow pigmentation that is characteristic of the carotenoid family. Their assembled genomes also showed that the three strains were not identical in terms of their genome sizes that were 7.82, 7.95 and 8.70 Mb for strains USMAHM13, USMAA1020 and USMAA2-4, respectively, which are slightly larger than that of Cupriavidus necator H16 (7.42 Mb). The average nucleotide identity (ANI) results indicated that the strains were genetically related and the genome pairs belong to the same species. On the basis of the results obtained in this study, the three strains are considered to represent a novel species for which the name Cupriavidus malaysiensis sp. nov. is proposed. The type strain of the species is USMAA1020T (= DSM 19416T = KCTC 32390T).


July 7, 2019  |  

Complete genome sequence of the symbiotic strain Bradyrhizobium icense LMTR 13T, isolated from lima bean (Phaseolus lunatus) in Peru.

The complete genome sequence of Bradyrhizobium icense LMTR 13T, a root nodule bacterium isolated from the legume Phaseolus lunatus, is reported here. The genome consists of a circular 8,322,773-bp chromosome which codes for a large and novel symbiotic island as well as genes putatively involved in soil and root colonization. Copyright © 2018 Ormeño-Orrillo et al.


July 7, 2019  |  

Modular traits of the Rhizobiales root microbiota and their evolutionary relationship with symbiotic Rhizobia.

Rhizobia are a paraphyletic group of soil-borne bacteria that induce nodule organogenesis in legume roots and fix atmospheric nitrogen for plant growth. In non-leguminous plants, species from the Rhizobiales order define a core lineage of the plant microbiota, suggesting additional functional interactions with plant hosts. In this work, genome analyses of 1,314 Rhizobiales isolates along with amplicon studies of the root microbiota reveal the evolutionary history of nitrogen-fixing symbiosis in this bacterial order. Key symbiosis genes were acquired multiple times, and the most recent common ancestor could colonize roots of a broad host range. In addition, root growth promotion is a characteristic trait of Rhizobiales in Arabidopsis thaliana, whereas interference with plant immunity constitutes a separate, strain-specific phenotype of root commensal Alphaproteobacteria. Additional studies with a tripartite gnotobiotic plant system reveal that these traits operate in a modular fashion and thus might be relevant to microbial homeostasis in healthy roots. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.


July 7, 2019  |  

Genomic characterization of methylotrophy of Oharaeibacter diazotrophicus strain SM30T.

Oharaeibacter diazotrophicus strain SM30T, isolated from rice rhizosphere, is an aerobic, facultative lanthanide (Ln3+)-utilizing methylotroph and diazotroph that belongs to the Methylocystaceae family. In this research, the complete genome sequence of strain SM30T was determined, and its methylotrophy modules were characterized. The genome consists of one chromosome and two plasmids, comprising a total of 5,004,097 bp, and the GC content was 71.6 mol%. A total of 4497 CDSs, 67 tRNA, and 9 rRNA were encoded. Typical alpha-proteobacterial methylotrophy genes were found: pyrroloquinoline quinone (PQQ)-dependent methanol dehydrogenase (MDH) (mxaF and xoxF1-4), methylotrophy regulatory proteins (mxbDM and mxcQE), PQQ synthesis, H4F pathway, H4MPT pathway, formate oxidation, serine cycle, and ethylmalonyl-CoA pathway. SDS-PAGE and subsequent LC-MS analysis, and qPCR analysis revealed that MxaF and XoxF1 were the dominant MDH in the absence or presence of lanthanum (La3+), respectively. The growth of MDH gene-deletion mutants on alcohols and qPCR results indicated that mxaF and xoxF1 are also involved in ethanol and propanol oxidation, xoxF2 participates in methanol oxidation in the presence of La3+, while xoxF3 was associated with methanol and ethanol oxidation in the absence of La3+, implying that XoxF3 is a calcium (Ca2+)-binding XoxF. Four Ln3+ such as La3+, cerium (Ce3+), praseodymium (Pr3+), and neodymium (Nd3+) served as cofactors for XoxF1 by supporting ?mxaF growth on methanol. Some heavier lanthanides inhibited growth of SM30 on methanol. This study contributes to the understanding of the function of various XoxF-type MDHs and their roles in methylotrophs. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.


July 7, 2019  |  

Complete genome sequence of the Robinia pseudoacacia L. symbiont Mesorhizobium amorphae CCNWGS0123.

Mesorhizobium amorphae CCNWGS0123 was isolated in 2006, from effective nodules of Robinia pseudoacacia L. grown in lead-zinc mine tailing site, in Gansu Province, China. M. amorphae CCNWGS0123 is an aerobic, Gram-negative, non-spore-forming rod strain. This paper characterized M. amorphae CCNWGS0123 and presents its complete genome sequence information and genome annotation. The 7,374,589 bp long genome which encodes 7136 protein-coding genes and 63 RNA coding genes, contains one chromosome and four plasmids. Moreover, a chromosome with no gaps was assembled.


July 7, 2019  |  

Complete genome sequence of Rhizobium sp. strain 11515TR, isolated from tomato rhizosphere in the Philippines.

Rhizobium sp. strain 11515TR was isolated from the rhizosphere of to- mato in Laguna, Philippines. The 7.07-Mb complete genome comprises three repli- cons, one chromosome, and two plasmids, with a G?C content of 59.4% and 6,720 protein-coding genes. The genome encodes gene clusters supporting rhizosphere processes, plant symbiosis, and secondary bioactive metabolites.


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