Halomonas azerica sp. nov., Isolated from Urmia Lake in Iran

Marinobacter azerbaijanicus sp. nov., a moderately halophilic bacterium from Urmia Lake, Iran

A novel moderately halophilic, Gram-stain-negative and facultatively anaerobic bacterium, designated as strain TBZ242T, was isolated from water of Urmia Lake in the Azerbaijan region of Iran. The cells were found to be rod-shaped and motile by a single polar flagellum, producing circular and yellowish colonies. The strain could grow in the presence of 0.5-10 % (w/v) NaCl (optimum, 2.5-5 %). The temperature and pH ranges for growth were 15-45 °C (optimum 30 °C) and pH 7.0-11.0 (optimum pH 8.0) on marine agar. The 16S rRNA gene sequence analysis revealed that strain TBZ242T belonged to the genus Marinobacter, showing the highest similarities to Marinobacter algicola DG893T (98.8 %), Marinobacter vulgaris F01T (98.8 %), Marinobacter salarius R9SW1T (98.5 %), Marinobacter panjinensis PJ-16T (98.4 %), Marinobacter orientalis W62T (98.0 %) and Marinobacter denitrificans JB2H27T (98.0 %). The 16S rRNA and core-genome phylogenetic trees showed that strain TBZ242T formed a distinct branch, closely related to a subclade accommodating M. vulgaris, M. orientalis, M. panjinensis, M. denitrificans, M. algicola, M. salarius and M. iranensis, within the genus Marinobacter. Average nucleotide identity and digital DNA-DNA hybridization values between strain TBZ242T and the type strains of the related species of Marinobacter were ≤85.0 and 28.6 %, respectively, confirming that strain TBZ242T represents a distinct species. The major cellular fatty acids of strain TBZ242T were C16 : 0 and C16 : 1  ω7c/C16 : 1 ω6c and the quinone was ubiquinone Q-9. The genomic DNA G+C content of strain TBZ242T is 57.2 mol%. Based on phenotypic, chemotaxonomic and genomic data, strain TBZ242T represents a novel species within the genus Marinobacter, for which the name Marinobacter azerbaijanicus sp. nov. is proposed. The type strain is TBZ242T (= CECT 30649T = IBRC-M 11466T). Genomic fragment recruitment analysis showed that this species prefers aquatic saline environments with intermediate salinities, being detected on metagenomic databases of Lake Meyghan (Iran) with 5 and 18 % salinity, respectively.

A long-awaited taxogenomic investigation of the family Halomonadaceae

The family Halomonadaceae is the largest family composed of halophilic bacteria, with more than 160 species with validly published names as of July 2023. Several classifications to circumscribe this family are available in major resources, such as those provided by the List of Prokaryotic names with Standing in Nomenclature (LPSN), NCBI Taxonomy, Genome Taxonomy Database (GTDB), and Bergey's Manual of Systematics of Archaea and Bacteria (BMSAB), with some degree of disagreement between them. Moreover, regardless of the classification adopted, the genus Halomonas is not phylogenetically consistent, likely because it has been used as a catch-all for newly described species within the family Halomonadaceae that could not be clearly accommodated in other Halomonadaceae genera. In the past decade, some taxonomic rearrangements have been conducted on the Halomonadaceae based on ribosomal and alternative single-copy housekeeping gene sequence analysis. High-throughput technologies have enabled access to the genome sequences of many type strains belonging to the family Halomonadaceae; however, genome-based studies specifically addressing its taxonomic status have not been performed to date. In this study, we accomplished the genome sequencing of 17 missing type strains of Halomonadaceae species that, together with other publicly available genome sequences, allowed us to re-evaluate the genetic relationship, phylogeny, and taxonomy of the species and genera within this family. The approach followed included the estimate of the Overall Genome Relatedness Indexes (OGRIs) such as the average amino acid identity (AAI), phylogenomic reconstructions using amino acid substitution matrices customized for the family Halomonadaceae, and the analysis of clade-specific signature genes. Based on our results, we conclude that the genus Halovibrio is obviously out of place within the family Halomonadaceae, and, on the other hand, we propose a division of the genus Halomonas into seven separate genera and the transfer of seven species from Halomonas to the genus Modicisalibacter, together with the emendation of the latter. Additionally, data from this study demonstrate the existence of various synonym species names in this family.

Hypersaline Lake Urmia: a potential hotspot for microbial genomic variation

Lake Urmia located in Iran is a hypersaline environment with a salinity of about 27% (w/v). Metagenomic analyses of water samples collected from six locations in the lake exhibited a microbial community dominated by representatives of the family Haloferacaceae (69.8%), mainly those affiliated to only two genera, Haloquadratum (59.3%) and Halonotius (9.1%). Similar to other hypersaline lakes, the bacterial community was dominated by Salinibacter ruber (23.3%). Genomic variation analysis by inspecting single nucleotide variations (SNVs) and insertions/deletions (INDELs) exhibited a high level of SNVs and insertions, most likely through transformation for abundant taxa in the Lake Urmia community. We suggest that the extreme conditions of Lake Urmia and specifically its high ionic concentrations could potentially increase the SNVs and insertions, which can consequently hamper the assembly and genome reconstruction from metagenomic reads of Lake Urmia.

Culturable bacteria diversity in stem liquid and resina from Populus euphratica and screening of plant growth-promoting bacteria

BACKGROUND

Populus euphratica Olivier is a kind of tree capable of growing in extremely arid desert and semi-desert environments. In this study, a culture-dependent method was used to analyze the bacterial diversity of stem liquid of P. euphratica and resina of P. euphratica, and to further evaluate plant growth promoting (PGP) activity.

RESULTS

A total of 434 bacteria were isolated from stem fluid and resina of P. euphratica in Ebinur Lake Wetland Nature Reserve and Mulei Primitive forest. The results of taxonomic composition analysis shows that Gammaproteobacteria, Firmicutes, and Actinobacteria_c are the three dominant groups in all the communities, and the representative genera are Bacillus, Nesterenkonia and Halomonas. The diversity analysis shows that the culturable bacterial community diversity of P. euphratica in Ebinur Lake Wetland Nature Reserve is higher than that in Mulei Primitive forest, and the bacterial community diversity of P. euphratica stem fluid is higher than that of resina. According to PGP activity evaluation, 158 functional bacteria with plant growth promoting potential were screened. Among them, 61 strains havephosphorus solubilizing abilities, 80 strains have potassium solubilizing abilities, 32 strains have nitrogen fixation abilities, and 151 strains have iron ammonia salt utilization abilities. The germination rate, plant height, and dry weight of the maize seedlings treated with strains BB33-1, TC10 and RC6 are significantly higher than those of the control group.

CONCLUSION

In this study, a large number of culturable bacteria were isolated from P. euphratica, which provides new functional bacteria sources for promoting plant growth.

Shewanella azerbaijanica sp. nov. a novel aquatic species with high bioremediation abilities

A novel Gram-negative, facultative anaerobic, rod-shaped, and non-motile bacterium with bio-degradation potential of polycyclic aromatic hydrocarbons (PAHs) and uranium bio-reduction, designated as RCRI7^T, was isolated from Qurugöl Lake water near Tabriz city. Strain RCRI7^T can grow in the absence of NaCl and tolerates up to 3% NaCl (optimum, 0-0.5%), at the temperature range of 4-45 °C (optimum, 30 °C) and a pH range of 6-9 (optimum, pH 7 ± 0.5). Results of phylogenetic analysis based on 16S rRNA gene sequence indicated that strain RCRI7^T is affiliated with the genus Shewanella, most closely related to Shewanella xiamenensis S4^T (99.1%) and Shewanella putrefaciens JCM 20190^T (98.9%). The genomic DNA G+C content of strain RCRI7^T is 41 mol%. The major fatty acids are C_16:1ω9c, C_18:1ω9c and iso-C_17:1ω5c. The OrthoANI and ANIb values between RCRI7^T and Shewanella xiamenensis S4^T were 87.4% and 87.7%, and between RCRI7^T and Shewanella putrefaciens JCM 20190^T were 79.5% and 79.7%, respectively. Strain RCRI7^T displayed dDDH values of 30.2% and 39.8% to Shewanella xiamenensis S4^T and Shewanella putrefaciens JCM 20190^T, respectively. The major polar lipids include phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). The respiratory quinone is Q8. Based on the polyphasic evidence presented in this paper, strain RCRI7^T is considered to represent a novel species, with bioremediation potential, in the genus Shewanella, for which the name Shewanella azerbaijanica sp. nov. is proposed. The type strain is RCRI7^T (= JCM 17276^T) (= KCTC 62476^T).