Phylogenomic analysis of Pseudomonas nitroreducens strains FY43 and FY47

Proper identification of strain is essential in understanding the ecology of a bacteria species. The classification of Pseudomonas nitroreducens is still being questioned and revised until now. The novel P. nitroreducens strains FY43 and FY47 used in this study have been reported to show a high level of tolerance to glyphosate. In this study, next-generation sequencing (NGS) and whole genome analysis were used to clarify the delineation of the species. Whole genome analysis showed that P. nitroreducens strains FY43 and FY47 shared high homology to five reference genomes of P. nitroreducens: strain B, Aramco J, NBRC 12694, DF05, and TX01. Phylogenomic and phylogenetic analysis (average nucleotide identity based on BLAST (ANIb), genome-to-genome distance (GGDC) analysis) showed that both P. nitroreducens strains FY43 and FY47 are Pseudomonas nitroreducens members. However, strains DF05 and TX01 were not correctly assigned at the species level for all the analyses. The P. nitroreducens strain DF05 and TX01 should be further investigated for their classification as the correct species classification is the prerequisite for future diversity studies.

Comparative Genomics of Pseudomonas stutzeri Complex: Taxonomic Assignments and Genetic Diversity

Pseudomonas stutzeri is a species complex with extremely broad phenotypic and genotypic diversity. However, very little is known about its diversity, taxonomy and phylogeny at the genomic scale. To address these issues, we systematically and comprehensively defined the taxonomy and nomenclature for this species complex and explored its genetic diversity using hundreds of sequenced genomes. By combining average nucleotide identity (ANI) evaluation and phylogenetic inference approaches, we identified 123 P. stutzeri complex genomes covering at least six well-defined species among all sequenced Pseudomonas genomes; of these, 25 genomes represented novel members of this species complex. ANI values of ≥∼95% and digital DNA-DNA hybridization (dDDH) values of ≥∼60% in combination with phylogenomic analysis consistently and robustly supported the division of these strains into 27 genomovars (most likely species to some extent), comprising 16 known and 11 unknown genomovars. We revealed that 12 strains had mistaken taxonomic assignments, while 16 strains without species names can be assigned to the species level within the species complex. We observed an open pan-genome of the P. stutzeri complex comprising 13,261 gene families, among which approximately 45% gene families do not match any sequence present in the COG database, and a large proportion of accessory genes. The genome contents experienced extensive genetic gain and loss events, which may be one of the major mechanisms driving diversification within this species complex. Surprisingly, we found that the ectoine biosynthesis gene cluster (ect) was present in all genomes of P. stutzeri species complex strains but distributed at very low frequency (43 out of 9548) in other Pseudomonas genomes, suggesting a possible origin of the ancestors of P. stutzeri species complex in high-osmolarity environments. Collectively, our study highlights the potential of using whole-genome sequences to re-evaluate the current definition of the P. stutzeri complex, shedding new light on its genomic diversity and evolutionary history.

First National Genomic Epidemiological Study of Neisseria gonorrhoeae Strains Spreading Across Sweden in 2016

The increasing transmission and antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a global health concern with worrying trends of decreasing susceptibility to also the last-line extended-spectrum cephalosporin (ESC) ceftriaxone. A dramatic increase of reported gonorrhea cases has been observed in Sweden from 2016 and onward. The aim of the present study was to comprehensively investigate the genomic epidemiology of all cultured N. gonorrhoeae isolates in Sweden during 2016, in conjunction with phenotypic AMR and clinical and epidemiological data of patients. In total, 1279 isolates were examined. Etest and whole-genome sequencing (WGS) were performed, and epidemiological data obtained from the Public Health Agency of Sweden. Overall, 51.1%, 1.7%, and 1.3% resistance to ciprofloxacin, cefixime, and azithromycin, respectively, was found. No isolates were resistant to ceftriaxone, however, 9.3% of isolates showed a decreased susceptibility to ceftriaxone and 10.5% to cefixime. In total, 44 penA alleles were found of which six were mosaic (n = 92). Using the typing schemes of MLST, NG-MAST, and NG-STAR; 133, 422, and 280 sequence types, respectively, and 93 NG-STAR clonal complexes were found. The phylogenomic analysis revealed two main lineages (A and B) with lineage A divided into two main sublineages (A1 and A2). Resistance and decreased susceptibility to ESCs and azithromycin and associated AMR determinants, such as mosaic penA and mosaic mtrD, were predominantly found in sublineage A2. Resistance to cefixime and azithromycin was more prevalent among heterosexuals and MSM, respectively, and both were predominantly spread through domestic transmission. Continuous surveillance of the spread and evolution of N. gonorrhoeae, including phenotypic AMR testing and WGS, is essential for enhanced knowledge regarding the dynamic evolution of N. gonorrhoeae and gonorrhea epidemiology.

The phylogenomic landscape of the genus Serratia

The genus Serratia has been studied for over a century and includes clinically-important and diverse environmental members. Despite this, there is a paucity of genomic information across the genus and a robust whole genome-based phylogenetic framework is lacking. Here, we have assembled and analysed a representative set of 664 genomes from across the genus, including 215 historic isolates originally used in defining the genus. Phylogenomic analysis of the genus reveals a clearly-defined population structure which displays deep divisions and aligns with ecological niche, as well as striking congruence between historical biochemical phenotyping data and contemporary genomics data. We show that Serratia is a diverse genus which displays striking plasticity and ability to adapt to its environment, including a highly-varied portfolio of plasmids, and provide evidence of different patterns of gene flow across the genus. This work provides an essential platform for understanding the emergence of clinical and other lineages of Serratia.

Conservation of magnetite biomineralization genes in all domains of life and implications for magnetic sensing

Animals use geomagnetic fields for navigational cues, yet the sensory mechanism underlying magnetic perception remains poorly understood. One idea is that geomagnetic fields are physically transduced by magnetite crystals contained inside specialized receptor cells, but evidence for intracellular, biogenic magnetite in eukaryotes is scant. Certain bacteria produce magnetite crystals inside intracellular compartments, representing the most ancient form of biomineralization known and having evolved prior to emergence of the crown group of eukaryotes, raising the question of whether magnetite biomineralization in eukaryotes and prokaryotes might share a common evolutionary history. Here, we discover that salmonid olfactory epithelium contains magnetite crystals arranged in compact clusters and determine that genes differentially expressed in magnetic olfactory cells, contrasted to nonmagnetic olfactory cells, share ancestry with an ancient prokaryote magnetite biomineralization system, consistent with exaptation for use in eukaryotic magnetoreception. We also show that 11 prokaryote biomineralization genes are universally present among a diverse set of eukaryote taxa and that nine of those genes are present within the Asgard clade of archaea Lokiarchaeota that affiliates with eukaryotes in phylogenomic analysis. Consistent with deep homology, we present an evolutionary genetics hypothesis for magnetite formation among eukaryotes to motivate convergent approaches for examining magnetite-based magnetoreception, molecular origins of matrix-associated biomineralization processes, and eukaryogenesis.

Microvirga Puerhi Sp. Nov., Isolated from Puerh Tea Garden Soil

Strain WGZ8T was isolated from a soil sample of Puerh tea garden in Puer city, Southwest China. The isolate was rod-shaped, Gram-stain negative, aerobic, non-motile. Growth occurred within 0-3.0% (w/v) NaCl (optimal concentration, 0-1.0%), pH 5.0-11.0 (optimal pH, 7.0) and 10-40°C (optimal temperature, 28°C). 16S rRNA gene sequences based phylogenetic and phylogenomic analysis revealed that WGZ8T belonged to the genus Microvirga. Its major cellular fatty acids were C19:0 cyclo ω8c, C16:0, C18:1ω7c and/or C18:1ω6c. The profile of polar lipids included phosphatidyldimethylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol and phosphatidyl-glycerol. The only respiratory quinone was detected as ubiquinone 10 (Q-10). The genome size of strain WGZ8T was 5.17MB, and the content of DNA G+C was 61%. Based on the results of digital DNA-DNA hybridization and phenotypic results, strain WGZ8T could be concluded as a novel species of the genus Microvirga, for which the name Microvirga puerhi sp. nov. is proposed. The type strain is WGZ8T (=CGMCC 1.19171T=JCM XXXXT).

Shewanella nanhaiensis sp. nov., a marine bacterium isolated from sediment of South China Sea, and emended descriptions of Shewanella woodyi, Shewanella hanedai and Shewanella canadensis

A Gram-stain-negative, motile, facultative anaerobic and rod-shaped bacterium, designated strain NR704-98T, was isolated from marine sediment of the northern South China Sea. Cells were positive for oxidase and catalase activity. Growth was observed at 4–30 °C (optimum 20–25 °C), at pH 6–9 (pH 7) and with 0.5–7 % NaCl (2 %). The 16S rRNA gene-based phylogenetic analysis revealed that the nearest phylogenetic neighbours of strain NR704-98T were Shewanella woodyi MS32T (97.9 %), Shewanella hanedai 281T (97.1 %), Shewanella sediminis HAW-EB3T (96.8 %) and Shewanella canadensis HAW-EB2T (96.7 %). Based on the results of phylogenomic analysis, the average nucleotide identity and the digital DNA–DNA hybridization values between strain NR704-98T and the previously mentioned type strains of species of the genus Shewanella were in the range of 74.9–93.1 % and 20.6–51.4 %, respectively. The respiratory quinones were Q-7 and Q-8. The predominant fatty acids (>10 %) of strain NR704-98T were C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and iso-C15 : 0. Phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminophospholipids and five unidentified lipids were detected in strain NR704-98T. Based on the phylogenetic and phenotypic characteristics, strain NR704-98T is considered to represent a novel species of the genus Shewanella , for which the name Shewanella nanhaiensis sp. nov. is proposed. The type strain is NR704-98T (=KCTC 82799T=MCCC 1K06091T).