A detailed phenotypic characterisation of the type strains of Halomonas species

Advances and challenges in polyhydroxyalkanoates (PHA) production using Halomonas species: A review

Plastic waste pollution is one of the major threats to sustainable development. Biodegradable polymers and biopolymers such as polyhydroxyalkanoates (PHAs) offer suitable alternatives for replacing synthetic plastics. PHAs are produced by diverse bacteria species and archaea as storage compounds for utilization as carbon and energy sources. Halomonas species have emerged as attractive microbial cell factories for biosynthesis of PHAs due to their metabolic versality, ability to valorize diverse feedstock materials, and tolerance to high salinity and pH that allows fermentation in contamination-resistant conditions. In recent years, there has been great attention to the use of Halomonas species in PHA biosynthesis and genetic engineering efforts for enhanced production. This article provides a discussion of the current state of knowledge on production of polyhydroxyalkanoates by Halomonas species. It includes an overview of PHA biosynthesis mechanisms, fermentation strategies, production with cheap substrates, exploitation of open and unsterile conditions, co-production of PHAs and other products, and advances genetic engineering efforts.

Pseudohoeflea coraliihabitans sp. nov., a poly-β-hydroxybutyrate-producing, halotolerant bacterium isolated from coral sediment in the Dapeng peninsula (Guangdong, China)

A Gram-stain-negative, strictly aerobic, motile, flagellated, rod-shaped, halotolerant, and poly-β-hydroxyalkanoate-producing bacterium, designated DP4N28-3T, was isolated from offshore sediment surrounding hard coral in the Dapeng peninsula (Guangdong, PR China). Growth occurred at 15-35 °C (optimal at 30 °C), pH 6.0-9.5 (optimal at 6.0-7.0), and 0.0-30.0 % NaCl concentration (w/v, optimal at 0.0-2.0 %), showing halotolerance. Phylogeny based on 16S rRNA gene sequences, five housekeeping genes, and genome sequences identified Pseudohoeflea suaedae DSM 23348T (98.1 %, 16S rRNA gene sequence similarity) as the most related species to strain DP4N28-3T. Average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values between strain DP4N28-3T and P. suaedae DSM 23348T were all below the threshold of species demarcation. Major phenotypic differences were the flagella type and the limited sources of single carbon utilization by strain DP4N28-3T, which only included acetic acid, acetoacetic acid, d-glucuronic acid, and glucuronamide. Strain DP4N28-3T harboured the class I poly-β-hydroxyalkanoate synthase gene (phaC) and produced poly-β-hydroxybutyrate. The fatty acids were summed feature 8 (C18 : 1  ω6c and/or C18 : 1  ω7c, 49.4 %) and C16 : 0 (13.4 %). The major cellular polar lipids consisted of phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, and sulfoquinovosyl diacylglycerol. The respiratory quinone was Q-10. The results of the phylogenetic, genomic, phenotypic, and chemotaxonomic analysis indicated that the isolated strain represents the type strain of a novel species. Based on these results, strain DP4N28-3T (=MCCC 1K05639T=KCTC 82803T) is proposed as the type strain of the novel species Pseudohoeflea coraliihabitans sp. nov.

Probiotic Potential of Lactobacillus and Enterococcus Strains Isolated From the Faecal Microbiota of Critically Endangered Hangul Deer (Cervus hanglu hanglu): Implications for Conservation Management

The mammalian gut microbiota plays a crucial role in promoting host health, and lactic acid bacteria (LAB) are commonly employed as probiotics for their beneficial effects. The Hangul deer (Cervus hanglu hanglu), a critically endangered red deer subspecies found in the Indian subcontinent, requires meticulous health management for its conservation. This pioneering study aimed to isolate, identify, and evaluate the in-vitro probiotic functional properties of LAB strains from the faeces of Hangul deer. A total of 27 LAB strains were isolated and identified using 16S rDNA gene sequencing, followed by comprehensive probiotic characterization and safety assessment. Remarkably, four species exhibited robust resistance and survivability against varying pH levels and bile salts, along with high aggregation and co-aggregation capacities. Notably, Lactobacillus acidophilus and Enterococcus mundtii strains displayed antibacterial activities. Safety assessment revealed the absence of hemolytic activity and virulence genes in all four strains. Antibiotic susceptibility testing showed that Lactobacillus acidophilus and Enterococcus casseliflavus were susceptible to all tested antibiotics, while Enterococcus mundtii exhibited resistance to clindamycin, and Enterococcus gallinarum exhibited resistance to erythromycin. These findings suggest that the isolated LAB strains possess advantageous probiotic characteristics and hold potential as dietary supplements for promoting the health and disease management of Hangul deer.

Ectoine production from a novel bacterial strain and high-purity purification with a cost-effective and single-step method

This study marks the exploration into the production of ectoine, a valuable compound with significant potential as an antioxidant, osmoprotectant, anti-inflammatory agent, and stabilizer of cell membranes, proteins, and DNA integrity. Our focus centred on investigating the presence of ectoine and optimizing its production by the novel ectoine producer bacterial strain, Piscibacillus halophilus. For the optimization of ectoine production the effects of carbon and nitrogen sources, salt, pH, agitation and incubation period were optimized by one-factor-at-a-time. We started with an initial ectoine content of 46.92 mg/L, and through a series of optimization processes, we achieved a remarkable increase, resulting in an ectoine content of 1498.2 mg/L. The bacterial species P. halophilus achieved its highest ectoine production after 48 h of incubation, with conditions set at 10 % (w/v) salinity, pH of 7.50, and an agitation speed of 160 rpm. These precise conditions were found to be the most favourable for maximizing ectoine production by this strain. Besides, we have achieved successful purification of ectoine from the crude extract through a streamlined single-step process. This purification method has delivered an exceptional level of purity, surpassing 99.15 %, and an impressive yield of over 99 %. Importantly, we accomplished this using readily available and cost-effective strong acids (HCl) and strong bases (NaOH) to arrange pH gradients. The use of acid and base in the purification process of ectoine reflects an innovative and sustainable methodology.

Genome analysis deciphered Chryseobacterium indicum is a distinct species associated with freshwater pufferfish

A bacterium, strain PS-8T of the genus Chryseobacterium, was isolated from the skin of freshwater pufferfish (Tetraodon cutcutia). Strain PS-8T is a Gram-negative, aerobic, non-motile, and rod-shaped bacterium. Colonies appear in yellowish-orange colors. The major cellular fatty acids were C15:0 iso, C17:0 iso 3OH, C15:0 iso 3OH, and C11:0 anteiso. The predominant polar lipids were phosphatidylethanolamine and amino lipids. The genome size is 4.83 Mb. The G + C content was 35.6%. The in silico dDDH homology, ANI, and AAI were below the cutoff value, 70% and 95% to 96%, respectively, suggesting that strain PS-8T represents a defined species. The phylogenetic tree based on core and the non-recombinant genes showed the strain PS-8T clustered with Chryseobacterium gambrini DSM 18014T. Genome-wide analysis decodes several virulence factors of the genus Chryseobacterium, including genes for adherence, biofilm and stability, proliferation, resistance to immune response, and host-defense evasion system. The cladogram of the virulence genes showed a phylogenetic relationship among the Chryseobacterium species. Knowledge of the association of Chryseobacterium with freshwater pufferfish adds a new ecological niche to this bacterium.

Illegal dumping of oil and gas wastewater alters arid soil microbial communities

The Permian Basin, underlying southeast New Mexico and west Texas, is one of the most productive oil and gas (OG) provinces in the United States. Oil and gas production yields large volumes of wastewater with complex chemistries, and the environmental health risks posed by these OG wastewaters on sensitive desert ecosystems are poorly understood. Starting in November 2017, 39 illegal dumps, as defined by federal and state regulations, of OG wastewater were identified in southeastern New Mexico, releasing ~600,000 L of fluid onto dryland soils. To evaluate the impacts of these releases, we analyzed changes in soil geochemistry and microbial community composition by comparing soils from within OG wastewater dump-affected samples to unaffected zones. We observed significant changes in soil geochemistry for all dump-affected compared with control samples, reflecting the residual salts and hydrocarbons from the OG-wastewater release (e.g., enriched in sodium, chloride, and bromide). Microbial community structure significantly (P < 0.01) differed between dump and control zones, with soils from dump areas having significantly (P < 0.01) lower alpha diversity and differences in phylogenetic composition. Dump-affected soil samples showed an increase in halophilic and halotolerant taxa, including members of the Marinobacteraceae, Halomonadaceae, and Halobacteroidaceae, suggesting that the high salinity of the dumped OG wastewater was exerting a strong selective pressure on microbial community structure. Taxa with high similarity to known hydrocarbon-degrading organisms were also detected in the dump-affected soil samples. Overall, this study demonstrates the potential for OG wastewater exposure to change the geochemistry and microbial community dynamics of arid soils.IMPORTANCEThe long-term environmental health impacts resulting from releases of oil and gas (OG) wastewater, typically brines with varying compositions of ions, hydrocarbons, and other constituents, are understudied. This is especially true for sensitive desert ecosystems, where soil microbes are key primary producers and drivers of nutrient cycling. We found that releases of OG wastewater can lead to shifts in microbial community composition and function toward salt- and hydrocarbon-tolerant taxa that are not typically found in desert soils, thus altering the impacted dryland soil ecosystem. Loss of key microbial taxa, such as those that catalyze organic carbon cycling, increase arid soil fertility, promote plant health, and affect soil moisture retention, could result in cascading effects across the sensitive desert ecosystem. By characterizing environmental changes due to releases of OG wastewater to soils overlying the Permian Basin, we gain further insights into how OG wastewater may alter dryland soil microbial functions and ecosystems.

Decoding the Genomic Profile of the Halomicroarcula Genus: Comparative Analysis and Characterization of Two Novel Species

The genus Halomicroarcula, classified within the family Haloarculaceae, presently comprises eight haloarchaeal species isolated from diverse saline habitats, such as solar salterns, hypersaline soils, marine salt, and marine algae. Here, a detailed taxogenomic study and comparative genomic analysis of the genus Halomicroarcula was carried out. In addition, two strains, designated S1CR25-12T and S3CR25-11T, that were isolated from hypersaline soils located in the Odiel Saltmarshes in Huelva (Spain) were included in this study. The 16S rRNA and rpoB' gene sequence analyses affiliated the two strains to the genus Halomicroarcula. Typically, the species of the genus Halomicroarcula possess multiple heterogeneous copies of the 16S rRNA gene, which can lead to misclassification of the taxa and overestimation of the prokaryotic diversity. In contrast, the application of overall genome relatedness indexes (OGRIs) augments the capacity for the precise taxonomic classification and categorization of prokaryotic organisms. The relatedness indexes of the two new isolates, particularly digital DNA-DNA hybridization (dDDH), orthologous average nucleotide identity (OrthoANI), and average amino acid identity (AAI), confirmed that strains S1CR25-12T (= CECT 30620T = CCM 9252T) and S3CR25-11T (= CECT 30621T = CCM 9254T) constitute two novel species of the genus Halomicroarcula. The names Halomicroarcula saliterrae sp. nov. and Halomicroarcula onubensis sp. nov. are proposed for S1CR25-12T and S3CR25-11T, respectively. Metagenomic fragment recruitment analysis, conducted using seven shotgun metagenomic datasets, revealed that the species belonging to the genus Halomicroarcula were predominantly recruited from hypersaline soils found in the Odiel Saltmarshes and the ponds of salterns with high salt concentrations. This reinforces the understanding of the extreme halophilic characteristics associated with the genus Halomicroarcula. Finally, comparing pan-genomes across the twenty Halomicroarcula and Haloarcula species allowed for the identification of commonalities and differences between the species of these two related genera.

Halomonas citrativorans sp. nov., Halomonas casei sp. nov. and Halomonas colorata sp. nov., isolated from French cheese rinds

Eight Gram-stain-negative bacterial strains were isolated from cheese rinds sampled in France. On the basis of 16S rRNA gene sequence analysis, all isolates were assigned to the genus Halomonas. Phylogenetic investigations, including 16S rRNA gene studies, multilocus sequence analysis, reconstruction of a pan-genome phylogenetic tree with the concatenated core-genome content and average nucleotide identity (ANI) calculations, revealed that they constituted three novel and well-supported clusters. The closest relative species, determined using the whole-genome sequences of the strains, were Halomonas zhanjiangensis for two groups of cheese strains, sharing 82.4 and 93.1 % ANI, and another cluster sharing 92.2 % ANI with the Halomonas profundi type strain. The strains isolated herein differed from the previously described species by ANI values <95 % and several biochemical, enzymatic and colony characteristics. The results of phenotypic, phylogenetic and chemotaxonomic analyses indicated that the isolates belonged to three novel Halomonas species, for which the names Halomonas citrativorans sp. nov., Halomonas casei sp. nov. and Halomonas colorata sp. nov. are proposed, with isolates FME63T (=DSM 113315T=CIRM-BIA2430T=CIP 111880T=LMG 32013T), FME64T (=DSM 113316T=CIRM-BIA2431T=CIP 111877T=LMG 32015T) and FME66T (=DSM 113318T=CIRM-BIA2433T=CIP 111876T=LMG 32014T) as type strains, respectively.

Halomonas rhizosphaerae sp. nov. and Halomonas kalidii sp. nov., two novel moderate halophilic phenolic acid-degrading species isolated from saline soil

Four vanillic acid-degrading bacterial strains, named LR5S13T, LR5S20, and M4R5S39T and LN1S58, were isolated from Kalidium cuspidatum rhizosphere and bulk soils, respectively. Phylogenetic analysis based on 16S rRNA gene as well as core genome revealed that LR5S13T and LR5S20 clustered closely with each other and with Halomonas ventosae Al12T, and that the two strains shared the highest similarities (both 99.3 %) with H. ventosae Al12T, in contrast, M4R5S39T and LN1S58 clustered together and with Halomonas heilongjiangensis 9-2T, and the two strains shared the highest similarities (99.4 and 99.2 %, respectively) with H. heilongjiangensis 9-2T. The average nucleotides identities based on BLAST (ANIb) and digital DNA-DNA hybridization (dDDH) values of strains LR5S13T to LR5S20, and M4R5S39T to LN1S58, were both higher than the threshold values for delineation of a species. The ANIb and dDDH values of the four strains to their closely relatives were lower than the threshold values. All four strains take phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol as the major polar lipids, Summed Feature 8, Summed Feature 3, and C16:0 as the major fatty acids. Based on the phylogenetic and phenotypic results, the four strains should be classified as two novel Halomonas species. Therefore, Halomonas rhizosphaerae sp. nov. (type strain LR5S13T = KCTC 8016T = CGMCC 1.62049T) and Halomonas kalidii (type strain M4R5S39T = KCTC 8015T = CGMCC 1.62047T) are proposed. The geographical distribution analysis based on 16S rRNA gene revealed that the two novel species are widely distributed across the globe, specifically in highly saline habits, especially in Central and Eastern Asia.

Leucobacter edaphi sp. nov., a highly chromate-tolerant bacterium isolated from chromium containing chemical plant soil

A Gram-positive, aerobic, rod-shaped non-motile, non-sporulating bacterium, designated CSA2T, was isolated from chromium-containing soils collected from a chemical plant. The 16S rRNA gene sequence of strain CSA2T showed the highest homology with Leucobacter chromiireducens subsp. solipictus (97.85%), Leucobacter chromiireducens subsp. chromiireducens (97.85%). The digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI) and the amino acid identity (AAI) values among strains CSA2T and the selected Leucobacter species were 20.6-23.4% (dDDH), 72.67-78.03% (ANI) and 66.39-76.16% (AAI), falling below the recommended thresholds for species delimitation. The principal fatty acids were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. The polar lipids were phosphatidylglycerol, diphosphatidylglycerol and an unknown glycolipid. The major menaquinones detected were MK-10 and MK-11. The cell-wall amino acids included 2,4-diaminobutyric acid, threonine, glutamic acid, alanine and glycine. Based on molecular feature, phenotypic and chemotaxonomic, strain CSA2T was considered to be a novel species of the genus Leucobacter., and the name Leucobacter edaphi sp. nov. is proposed. The type strain is CSA2T (= JCM 34360T = CGMCC 1.18747T).

Genome analysis of haloalkaline isolates from the soda saline crater lake of Isabel Island; comparative genomics and potential metabolic analysis within the genus Halomonas

BACKGROUND

Isabel Island is a Mexican volcanic island primarily composed of basaltic stones. It features a maar known as Laguna Fragatas, which is classified as a meromictic thalassohaline lake. The constant deposition of guano in this maar results in increased levels of phosphorus, nitrogen, and carbon. The aim of this study was to utilize high-quality genomes from the genus Halomonas found in specialized databases as a reference for genome mining of moderately halophilic bacteria isolated from Laguna Fragatas. This research involved genomic comparisons employing phylogenetic, pangenomic, and metabolic-inference approaches.

RESULTS

The Halomonas genus exhibited a large open pangenome, but several genes associated with salt metabolism and homeostatic regulation (ectABC and betABC), nitrogen intake through nitrate and nitrite transporters (nasA, and narGI), and phosphorus uptake (pstABCS) were shared among the Halomonas isolates.

CONCLUSIONS

The isolated bacteria demonstrate consistent adaptation to high salt concentrations, and their nitrogen and phosphorus uptake mechanisms are highly optimized. This optimization is expected in an extremophile environment characterized by minimal disturbances or abrupt seasonal variations. The primary significance of this study lies in the dearth of genomic information available for this saline and low-disturbance environment. This makes it important for ecosystem conservation and enabling an exploration of its biotechnological potential. Additionally, the study presents the first two draft genomes of H. janggokensis.

Characterization of Haloarcula terrestris sp. nov. and reclassification of a Haloarcula species based on a taxogenomic approach

An extremely halophilic archaeon, strain S1AR25-5AT, was isolated from a hypersaline soil sampled in Odiel Saltmarshes Natural Area (Huelva, Spain). The cells were Gram-stain-negative, motile, pleomorphic rods. Cell growth was observed in the presence of 15-30 % (w/v) NaCl [optimum, 25 % (w/v) NaCl], at pH 6.0-9.0 (optimum, pH 6.5-7.5) and at 25-50 °C (optimum, 37 °C). Based on the 16S rRNA and rpoB' gene sequence comparisons, strain S1AR25-5AT was affiliated to the genus Haloarcula. Taxogenomic analysis, including comparison of the genomes and the phylogenomic tree based on the core-orthologous proteins, together with the genomic indices, i.e., orthologous average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity, confirmed that strain S1AR25-5AT (=CCM 9249T=CECT 30619T) represents a new species of the genus Haloarcula, for which we propose the name Haloarcula terrestris sp. nov. The major polar lipids were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulphate and an unidentified glycolipid, which correlated with the lipid profile of species of the genus Haloarcula. In addition, based on the modern approach in description of species in taxonomy of prokaryotes, the above mentioned genomic indexes indicated that the species Haloarcula tradensis should be considered as a heterotypic synonym of Haloarcula argentinensis.

Marinobacter iranensis sp. nov., a slightly halophilic bacterium from a hypersaline lake

A novel halophilic bacterium, strain 71-iT, was isolated from Inche-Broun hypersaline lake in Golestan province, in the north of Iran. It was a Gram-stain-negative, non-endospore forming, rod-shaped bacterium. It grew at 4-40 °C (optimum 30 °C), pH 6.0-11.0 (optimum pH 7.5) and with 0.5-15 % (w/v) NaCl [optimum 3 % (w/v) NaCl]. The results of phylogenetic analyses based on the 16S rRNA gene sequence comparison indicated its affiliation to the genus Marinobacter and the low percentage of identity with the most closely related species (97.5 %), indicated its placement as a novel species within this genus. Digital DNA-DNA hybridization (dDDH) values and average nucleotide identity (ANI) analyses of this strain against closely related species confirmed its condition of novel taxon. On the other hand, the percentage of the average amino acid identity (AAI) affiliated strain 71-iT within the genus Marinobacter. The DNA G+C content of this isolate was 57.7 mol%. The major fatty acids were C16 : 0 and C16 : 1ω7c and/or C16 : 1 ω6c. Ubiquinone-9 was the major isoprenoid quinone and diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) were the main polar lipids of this strain. On the basis of the phylogenomic and phenotypic (including chemotaxonomic) features, we propose strain 71-iT (= IBRC M 11023T = CECT 30160T = LMG 29252T) as the type strain of a novel species within the genus Marinobacter, with the name Marinobacter iranensis sp. nov. Genomic detections of this strain in various metagenomic databases indicate that it is a relatively abundant species in environments with low salinities (approximately 5 % salinity), but not in hypersaline habitats with high salt concentrations.

Towards high-throughput screening (HTS) of polyhydroxyalkanoate (PHA) production via Fourier transform infrared (FTIR) spectroscopy of Halomonas sp. R5-57 and Pseudomonas sp. MR4-99

High-throughput screening (HTS) methods for characterization of microbial production of polyhydroxyalkanoates (PHA) are currently under investigated, despite the advent of such systems in related fields. In this study, phenotypic microarray by Biolog PM1 screening of Halomonas sp. R5-57 and Pseudomonas sp. MR4-99 identified 49 and 54 carbon substrates to be metabolized by these bacteria, respectively. Growth on 15 (Halomonas sp. R5-57) and 14 (Pseudomonas sp. MR4-99) carbon substrates was subsequently characterized in 96-well plates using medium with low nitrogen concentration. Bacterial cells were then harvested and analyzed for putative PHA production using two different Fourier transform infrared spectroscopy (FTIR) systems. The FTIR spectra obtained from both strains contained carbonyl-ester peaks indicative of PHA production. Strain specific differences in the carbonyl-ester peak wavenumber indicated that the PHA side chain configuration differed between the two strains. Confirmation of short chain length PHA (scl-PHA) accumulation in Halomonas sp. R5-57 and medium chain length PHA (mcl-PHA) in Pseudomonas sp. MR4-99 was done using Gas Chromatography-Flame Ionization Detector (GC-FID) analysis after upscaling to 50 mL cultures supplemented with glycerol and gluconate. The strain specific PHA side chain configurations were also found in FTIR spectra of the 50 mL cultures. This supports the hypothesis that PHA was also produced in the cells cultivated in 96-well plates, and that the HTS approach is suitable for analysis of PHA production in bacteria. However, the carbonyl-ester peaks detected by FTIR are only indicative of PHA production in the small-scale cultures, and appropriate calibration and prediction models based on combining FTIR and GC-FID data needs to be developed and optimized by performing more extensive screenings and multivariate analyses.

Halomonas binhaiensis sp. nov., isolated from saline-alkali soil

A Gram-stain-negative, aerobic and rod-shaped bacterium, strain Y2R2^T, was isolated from a saline-alkali soil sample collected from Binhai New Area, Tianjin, PR China. Growth of strain Y2R2^T was observed at 10-45 °C (optimum, 30 °C), at pH 6.0-11.0 (optimum, pH 9.0) and in the presence of 0-15 % (w/v) NaCl (optimum, 9.0 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Y2R2^T was affiliated with the genus Halomonas and showed the highest similarity to Halomonas huangheensis BJGMM-B45^T (99.0%) and Halomonas cupida DSM 4740^T (98.4%). The digital DNA-DNA hybridization and average nucleotide identity values of 21.0-22.8 % and 73.3-75.7 % with the closely related species H. huangheensis BJGMM-B45^T, H. cupida DSM 4740^T, H. ventosae AL12^T, H. stenophila N12^T and H. litopenaei SYSU ZJ2214^T were lower than the threshold recommended for species discrimination.The major respiratory quinone of strain Y2R2^T was Q-9 and the major cellular fatty acids consisted of C_16 : 0, C_19 : 0 cyclo ω8c and summed feature 8 (C_18 : 1 ω7c and/or C_18 : 1 ω6c). The DNA G+C content of strain Y2R2^T was 57.0 mol%. On the basis of this polyphasic taxonomic study, strain Y2R2^T is considered to represent a novel species of the genus Halomonas, for which the name Halomonas binhaiensis sp. nov. is proposed. The type strain is Y2R2^T (=CGMCC 1.16974^T=KCTC 72578^T).

Biotechnological impacts of Halomonas: a promising cell factory for industrially relevant biomolecules

Extremophiles are the most fascinating life forms for their special adaptations and ability to offer unique extremozymes or bioactive molecules. Halophiles, the natural inhabitants of hypersaline environments, are one among them. Halomonas are the common genus of halophilic bacteria. To support growth in unusual environments, Halomonas produces various hydrolytic enzymes, compatible solutes, biopolymers like extracellular polysaccharides (EPS) and polyhydroxy alkaloates (PHA), antibiotics, biosurfactants, pigments, etc. Many of such molecules are being produced in large-scale bioreactors for commercial use. However, the prospect of the remaining bioactive molecules with industrial relevance is far from their application. Furthermore, the genetic engineering of the respective gene clusters could open up a new path to bio-prospect these molecules by overproducing their products through heterologous expression. The present survey on Halomonas highlights their ecological diversity, application potential of the their various industrially relevant biomolecules and impact of these biomolecules on respective fields.

Culture dependent and independent characterization of endophytic bacteria in the seeds of highland barley

Endophytes in the seeds of plants have shown plant growth promoting (PGP) properties. Highland barley is an economically important crop and a major part of the local diet in the Tibetan Plateau, China, with potential health benefits. We applied culture-dependent and culture-independent methods to study endophytic bacteria in the seeds of eight Highland barley varieties. Based on the seed properties, the variety Ali was clearly separated from the other varieties except the variety CM. Most of the 86 isolates were assigned into genus Bacillus. Approximately half of the isolates showed PGP properties in vitro. Compared to the not-inoculated plants, inoculation with the isolate Bacillus tequilensis LZ-9 resulted in greater length and number of roots, and in bigger aboveground and root weights. Based on the 16S rRNA gene sequencing, the seed microbiome was majorly affiliated with the phylum Proteobacteria and the family Enterobacteriaceae. Overall, the bacterial community compositions in the different varieties were different from each other, yet the between variety differences in community composition seemed relatively small. The differences in community compositions were associated with differences in the total and reducing sugar contents and viscosity of the seeds, thus possibly connected to differences in the osmotic pressure tolerance of the endophytes. The results suggested that the seed endophytes are likely to promote the growth of Highland barley since germination.

Complete genome sequence of a multiple-stress-tolerant bacterium Halomonas piezotolerans NBT06E8T isolated from a deep-sea sediment sample of the New Britain Trench

Halomonas piezotolerans NBT06E8T is a Gram-stain-negative, moderately halophilic, piezotolerant, H2O2 and heavy metal-resistant bacterium, isolated from a deep-sea sediment sample collected from the New Britain Trench at depth of 8900 m. Growth of the strain was observed at 4-45 °C (optimum 30 °C), at pH 5-11 (optimum 8-9) and in 0.5-21% (w/v) NaCl (optimum 3-7%). The optimum pressure for growth was 0.1-30 MPa (megapascal) with tolerance up to 60 MPa. Under optimum growth conditions, the strain could tolerant 15 mM H2O2. Here, we report the complete genome of H. piezotolerans NBT06E8T, which consists of 3,945,801 bp (G + C content of 57.93%) with a single chromosome, 3509 protein-coding genes, 60 tRNAs and 6 rRNA operons. Genomic analysis revealed the capability of utilizing various carbon and nitrogen sources, the presence of multiple toxin-antitoxin systems and strain-specific type VI secretion system benefitting its adaptation to the oligotrophic hadal environments. Multiple respiratory chain components, especially the strain-specific anaerobic enzymes, could allow its survival in both surficial and buried sediments with variable oxygen concentrations. Gene function and metabolic pathway analysis showed that strain NBT06E8T encodes a series of genes related to high hydrostatic pressure tolerance, antioxidative stress and heavy metal resistance, which could also contribute to its deep-sea adaptation strategies. The complete genome sequence of H. piezotolerans NBT06E8T provides further insights into the stress adaptation strategies of deep-sea bacteria and potential biotechnological application of Halomonas species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03283-3.

Halomonas alkalisoli sp. nov., a novel haloalkalophilic species from saline-alkaline soil, and reclassification of Halomonas daqingensis Wu et al. 2008 as a later heterotypic synonym of Halomonas desiderata Berendes et al. 1996

Two Gram-stain-negative, strictly aerobic, moderately halophilic, non-spore-forming and rod-shaped bacteria, designated M5N1S17T and M5N1S15, were isolated from saline soil in Baotou, China. A phylogenetic analysis based on 16S rRNA gene sequences showed that the two strains clustered closely with Halomonas montanilacus PYC7WT and shared 99.1 and 99.3% sequence similarities, respectively. The average nucleotide identity based on BLAST (ANIb) and MUMmer (ANIm) values of the two strains with each other were 95.5% and 96.7%, respectively, while the ANIb and ANIm values between the two strains and 15 closer Halomonas species were 74.8-91.3% and 84.1-92.6%, respectively. The major polar lipids of M5N1S17T are diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, and an unidentified phospholipid. The major polar lipids of M5N1S15 are diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, two unidentified phospholipids, and an unidentified lipid. The predominant ubiquinone in the two strains is Q-9. The major fatty acids of the two strains are C18:1ω6c and/or C18:1ω7c, C16:0, and C16:1ω7c and/or C16:1ω6c. Based on phylogenetic, phenotypic, and physiological results, strains M5N1S17T and M5N1S15 should be identified as a novel species of the genus Halomonas, for which Halomonas alkalisoli sp. nov. is proposed. The type strain is M5N1S17T (= CGMCC 1.19023T = KCTC 92130T). The phylogenetic trees showed that Halomonas daqingensis CGMCC 1.6443T clustered tightly with Halomonas desiderata FB2T, and the two strains shared >98.0% of ANI values with each other. Therefore, we propose the reclassification of H. daqingensis Wu et al. 2008 as a later heterotypic synonym of H. desiderata Berendes et al. 1996.

Sampling a gradient of red snow algae bloom density reveals novel connections between microbial communities and environmental features

Snow algae blooms and associated microbial communities play large roles in snow ecosystem processes. Patterns and mechanisms underpinning snow algae bloom spatial distribution and associated microbial community assembly dynamics are poorly understood. Here we examine associations of microbial communities and environmental measures between/within snow algae blooms. Snows from the Cascade Mountains and the Rocky Mountains (USA) were collected from medial (M), peripheral (P), and adjacent (A) zones of red snow algae blooms. Medial snow shows increased levels of pollen, lower oxidation–reduction potential, decreased algal and increased bacterial richness, and increased levels of potassium when compared to A and P within the same bloom. Between the Cascade and Rocky Mountains, fungal communities are distinct but bacterial and algal communities show little differentiation. A weighted OTU co-expression analysis (WOCNA) explores OTU modules and their differential correlation with environmental features, suggesting certain subcommunities may be altered by ecological patterns. Individual OTU interaction networks (fungi and bacteria) show high levels of connectivity compared to networks based on the red snow alga Sanguina nivaloides, which underscores associative differences between algal dominated networks and other taxa.

Halomonas faecis sp. nov., a halophilic bacterium isolated from human faeces

A novel moderately halophilic, Gram-stain-negative, catalase- and oxidase-positive, strictly aerobic, non-sporulating, non-motile rod, designated strain JSM 104105 ^T, was isolated from human faeces. Strain JSM 104105 ^T was able to grow with 0.5-18% (w/v) NaCl (optimum 4-9%), at pH 6-10.5 (optimum pH 7-8) and at 10-40 °C (optimum 30 °C) in complex media. The major cellular fatty acids were C_18:1ω7c, C_16:0, C_16:1ω7c and/or C_16:1ω6c, C_19:0 cyclo ω8c and C_12:0 3-OH. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid and three unidentified phospholipids. The predominant respiratory quinone was Q-9 and the genomic DNA G + C content was 64.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain JSM 104105 ^T should be assigned to the genus Halomonas, and was most closely related to Halomonas gudaonensis SL014B-69 ^T (99.0% sequence similarity), followed by Halomonas azerbaijanica TBZ202^T (98.6%) and Halomonas lysinitropha 3(2)^T (97.3%). The whole genomic analysis showed that strain JSM 104105 ^T constituted a different taxon separated from the recognized Halomonas species. Combined data from phenotypic and genotypic studies demonstrated that strain JSM 104105 ^T represents a new species of the genus Halomonas, for which the name Halomonas faecis sp. nov. is proposed. The type strain is JSM 104105 ^T (= CCTCC AB 2014160 ^T = CGMCC 1.12945 ^T = KCTC 42146 ^T).

Halomonas jincaotanensis sp. nov., isolated from the Pamir Plateau degrading polycyclic aromatic hydrocarbon

A Gram-strain-negative, rod-shaped, aerobic bacterium, designated strain TRM 85114^T, was isolated from the Jincaotan wetland in the Pamir Plateau of China. This strain grew optimally at 30 °C and pH 6.0 in the presence of 3% (w/v) NaCl. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain TRM 85114^T was affiliated with the genus Halomonas, and shared high sequence similarity with Halomonas korlensis XK1^T (97.3%) and Halomonas tibetensis pyc13^T (96.4%). Strain TRM 85114^T contained C_16:0 and C_19:0 cyclo ω8c as primary cellular fatty acids, Q-9 as predominate respiratory quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phospholipids of unknown structure containing glucosamine, unidentified aminophospholipids, unidentified lipids and three unidentified phospholipids as the major polar lipids. The complete genome of TRM 85114^T comprised 3,902 putative genes with a total of 4,126,476 bp and a G + C content of 61.6%. The average nucleotide identity and digital DNA-DNA hybridization values between strain TRM 85114^T and related type Halomonas strains of H. korlensis XK1^T, H. tibetensis pyc13^T, Chromohalobacter salexigens DSM 6768^T, and Halomonas urumqiensis BZ-SZ-XJ27^T were 75.4-88.9% and 22.9-39.2%, respectively. Based on phenotypic, chemotaxonomic, and molecular features, strain TRM 85114^T represents a novel species of the genus Halomonas, for which the name is proposed as Halomonas jincaotanensis sp. nov.. The type strain is TRM 85114^T (CCTCC AB 2021006^T = LMG 32311^T). The amount of 1-naphthylamine degradation by strain TRM 85114^T reached up to 32.0 mg/L in 14 days.

Heterotrophic Sulfur Oxidation of Halomonas titanicae SOB56 and Its Habitat Adaptation to the Hydrothermal Environment

Halomonas bacteria are ubiquitous in global marine environments, however, their sulfur-oxidizing abilities and survival adaptations in hydrothermal environments are not well understood. In this study, we characterized the sulfur oxidation ability and metabolic mechanisms of Halomonas titanicae SOB56, which was isolated from the sediment of the Tangyin hydrothermal field in the Southern Okinawa Trough. Physiological characterizations showed that it is a heterotrophic sulfur-oxidizing bacterium that can oxidize thiosulfate to tetrathionate, with the Na₂S₂O₃ degradation reaching 94.86%. Two potential thiosulfate dehydrogenase-related genes, tsdA and tsdB, were identified as encoding key catalytic enzymes, and their expression levels in strain SOB56 were significantly upregulated. Nine of fifteen examined Halomonas genomes possess TsdA- and TsdB-homologous proteins, whose amino acid sequences have two typical Cys-X2-Cys-His heme-binding regions. Moreover, the thiosulfate oxidation process in H. titanicae SOB56 might be regulated by quorum sensing, and autoinducer-2 synthesis protein LuxS was identified in its genome. Regarding the mechanisms underlying adaptation to hydrothermal environment, strain SOB56 was capable of forming biofilms and producing EPS. In addition, genes related to complete flagellum assembly system, various signal transduction histidine kinases, heavy metal transporters, anaerobic respiration, and variable osmotic stress regulation were also identified. Our results shed light on the potential functions of heterotrophic Halomonas bacteria in hydrothermal sulfur cycle and revealed possible adaptations for living at deep-sea hydrothermal fields by H. titanicae SOB56.

Alteribacter keqinensis sp. nov., a moderately halophilic bacterium isolated from a soda lake

A Gram-stain-positive, aerobic, endospore-forming and rod-shaped bacterium (KQ-3^T), which grew at 10-45 °C (optimum 35 °C), pH 8.0-10.5 (optimum pH 9.0) and in the presence of 0-16 % (w/v) NaCl (optimum 3.0 %), was isolated from a soda lake and identified as representing a novel species using a polyphasic taxonomic approach. Strain KQ-3^T was catalase-positive, oxidase-negative and non-motile. Phylogenetic analysis based on 16S rRNA gene sequence affiliated KQ-3^T to the genus Alteribacter and showed the highest similarities to Alteribacter natronophilus M30^T (97.90 %), Alteribacter aurantiacus K1-5^T (97.84 %) and Alteribacter populi FJAT-45347^T (97.22 %). Digital DNA-DNA hybridization and average nucleotide identity analyses revealed that KQ-3^T displayed 21.4 and 72.81% genomic DNA relatedness with the most closely related strain, A. natronophilus M30^T, respectively. KQ-3^T contained all of the conserved signature indels that are specific for members of the genus Alteribacter. The DNA G+C content was 45.03 mol%. The cell-wall peptidoglycan contained meso-diaminopimelic acid and the polar lipids consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and one unidentified phospholipid. The predominant menaquinone was MK-7 (100%) and the major fatty acids (>10 %) comprised anteiso-C_15 : 0, iso-C_15 : 0 and iso-C_16 : 0. Based on the data from the current polyphasic studies, KQ-3^T represents a novel species of the genus Alteribacter, for which the name Alteribacter keqinensis sp. nov. is proposed. The type strain is KQ-3^T (=ACCC 61799^T=KCTC 33933^T).

Aliidiomarina halalkaliphila sp. nov., a haloalkaliphilic bacterium isolated from a soda lake in Inner Mongolia Autonomous Region, China

A haloalkaliphilic strain (IM 1326^T) was isolated from brine sampled at a soda lake in the Inner Mongolia Autonomous Region, China. Cells of the strain were rod-shaped and motile. Strain IM 1326^T was able to grow at 4–42 °C (optimum, 37 °C) with 0–13.0 % (w/v) NaCl concentrations (optimum at 4.0–6.0 %) and at pH 7.5–11.0 (optimum at 9.0–10.0). The 16S rRNA gene phylogenetic analysis revealed that the isolate belongs to the genus Aliidiomarina and is closely related to the type strains of Aliidiomarina sanyensis (95.8 % sequence similarity), Aliidiomarina shirensis (95.7 %), Aliidiomarina iranensis (95.4 %) and Aliidiomarina haloalkalitolerans (95.3 %). The whole genome of strain IM 1326^T was sequenced, and the genomic DNA G+C content was 49.7 mol%. Average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between the isolate and the related Aliidiomarina species were 68.1–84.9 %, 76–78 % and 18.4–20.4 %, respectively. The respiratory quinone was ubiquinone-8. The polar lipid profile included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and one unidentified aminophospholipid. The predominant cellular fatty acids were summed feature 9 (10-methyl-C_16 : 0/iso-C_17 : 1 ω9c, 22.2 %), iso-C_15 : 0 (16.1 %) and iso-C_17 : 0 (13.1 %). Based on the results of phylogenetic analysis, genome relatedness, and the physiological and chemotaxonomic properties of the isolate, strain IM 1326^T is considered to represent a novel species of the genus Aliidiomarina, for which the name Aliidiomarina halalkaliphila sp. nov. is proposed (type strain IM 1326^T=CGMCC 1.17056^T=JCM 34227^T).

Halomonas antri sp. nov., a carotenoid-producing bacterium isolated from surface seawater

A Gram-negative, moderately halophilic bacterium, designated as strain Y3S6T, was isolated from a surface seawater sample collected from Dongangyoeng cave, Udo-myeon, Jeju-si, Jeju-do, Repulic of Korea. Cells of strain Y3S6T were aerobic, rod-shaped, non-sporulated, yellow, catalase- negative, oxidase-negative and motile with one polar flagellum. Growth of strain Y3S6T occurred at 15–40 °C (optimum: 25–30 °C), at pH 6.0–9.0 (optimum: pH 7.0) and in the presence of 0–13% NaCl (optimum: 1–6 %, w/v). The novel strain was able to produce carotenoids. Its chemotaxonomic and morphological characteristics were consistent with those of members of the genus Halomonas . Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain Y3S6T formed a clade with Halomonas pellis L5T (98.97 %) and Halomonas saliphila LCB169T(98.90%). The average nucleotide identity and digital DNA–DNA hybridization values of strain Y3S6T with the most closely related strains for which whole genomes are publicly available were 82.3–85.2% and 62.8–66.1 %, respectively. The major fatty acids in strain Y3S6T were C16 : 0, C19 : 0 cyclo ω8c and summed feature 8 (composed of C18 : 1 ω7c and/or C18 : 1 ω6c), and the predominant quinone was Q-9. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified phosphoglycolipid, one unidentified phosphoaminoglycolipid and one unidentified phospholipid. The genomic DNA G+C content based on the draft genome sequence was 64.2 mol%. The results of physiological and biochemical tests and 16S rRNA sequence analysis clearly revealed that strain Y3S6T represents a novel species in the genus Halomonas , for which the name Halomonas antri sp. nov. has been proposed. The type strain is Y3S6T (=KACC 21536T=NBRC 114315=TBRC 15164T).

Halomonas profundi sp. nov., isolated from deep-sea sediment of the Mariana Trench

Two novel Gram-stain-negative, facultative anaerobic, non-flagellated, rod-shaped bacterial strains, designated MT13T and MT32, were isolated from sediment samples collected from the Mariana Trench at a depth of 8300 m. The two strains grew at −2–30 °C (optimum, 25 °C), at pH 5.5–10.0 (optimum, pH 7.5–8.0) and with 0–15 % (w/v) NaCl (optimum, 3–6 %). They did not reduce nitrate to nitrite nor hydrolyse Tweens 40 and 80, aesculin, casein, starch and DNA. The genomic G+C contents of draft genomes of strain MT13T and MT32 were 52.2 and 54.1 m ol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains MT13T and MT32 were affiliated with the genus Halomonas , with the highest similarity to the type strain of Halomonas olivaria . The values of average nucleotide identity and in silico DNA–DNA hybridization between strain MT13T and MT32, and between strain MT13T and five closely related type strains of Halomonas species indicated that strains MT13T and MT32 belonged to the same species, but represented a novel species in the genus of Halomonas . The major cellular fatty acids of strains MT13T and MT32 were C16 : 0, summed feature 3(C16 : 1  ω7c/ω6c) and summed feature 8 (C18 : 1  ω7c/ω6c). Major polar lipids of strains MT13T and MT32 included phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Ubiquinone-9 was the predominant respiratory quinone. Based on data from the present polyphasic study, strains MT13T and MT32 represent a novel species of the genus Halomonas , for which the name Halomonas profundi sp. nov. is proposed. The type strain is MT13T (=MCCC 1K06389T=KCTC 82923T).

The impact of bacterial diversity on resistance to biocides in oilfields

Extreme conditions and the availability of determinate substrates in oil fields promote the growth of a specific microbiome. Sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB) are usually found in these places and can harm important processes due to increases in corrosion rates, biofouling and reservoir biosouring. Biocides such as glutaraldehyde, dibromo-nitrilopropionamide (DBNPA), tetrakis (hydroxymethyl) phosphonium sulfate (THPS) and alkyl dimethyl benzyl ammonium chloride (ADBAC) are commonly used in oil fields to mitigate uncontrolled microbial growth. The aim of this work was to evaluate the differences among microbiome compositions and their resistance to standard biocides in four different Brazilian produced water samples, two from a Southeast Brazil offshore oil field and two from different Northeast Brazil onshore oil fields. Microbiome evaluations were carried out through 16S rRNA amplicon sequencing. To evaluate the biocidal resistance, the Minimum Inhibitory Concentration (MIC) of the standard biocides were analyzed using enriched consortia of SRB and APB from the produced water samples. The data showed important differences in terms of taxonomy but similar functional characterization, indicating the high diversity of the microbiomes. The APB and SRB consortia demonstrated varying resistance levels against the biocides. These results will help to customize biocidal treatments in oil fields.

Isolation of a novel halothermophilic strain of the genus Gracilibacillus from Howz-e Sultan hypersaline lake in Iran

Background and Objectives:

Halothermophilic bacteria are adapted to high osmolarity and can grow in high saline environments and high temperatures. This study was aimed at the isolation of halothermophilic bacteria from Howz-e Sultan hypersaline lake in the central desert zone in Iran.

Materials and Methods:

Samples were collected and after preparing dilutions, the samples were cultured on Molten haloid agar with different salt concentrations (5–35%), then the plates were incubated at 35–70ºC in both aerobic and anaerobic conditions. Biochemical characterizations, utilization of carbon sources, production of exoenzymes and antibiotic susceptibility were investigated. Taxonomic and phylogenetic analyses were performed using 16S rRNA gene sequences.

Results:

One of the isolated bacteria was found to be Gram-positive, hyperhalophilic, thermophilic, endospore-forming, and was named as 1–9 h isolate. The bacterial cells were bacilli-shaped, which produced endospores at a subterminal position. This isolate was an aerobe and facultative anaerobe and grew between pH 5.0 and 10.0 (optimal growth at pH 7.0–7.5), at temperature between 15°C and 65°C (optimal growth at 40–45°C) and at salinity of 9–32% (w/v) NaCl, growing optimally at 18% (w/v) NaCl. On the basis of 16S rRNA gene sequence analysis, isolate 1–9 h belongs to the genus Bacillus within the phylum Firmicutes and showed the closest phylogenetic similarity to Gracilibacillus sp. IBP-V003 (99.0%).

Conclusion:

Based on the results of its phenotypic and genotypic properties, strain 1–9 h represents a novel strain of the genus Gracilibacillus. It can be used in various fields of industry and biotechnology.

Bowmanella yangjiangensis sp. nov. and Amphritea pacifica sp. nov., isolated from mariculture fishponds in China

Four Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strains (Y26, Y57^T, ZJ14W^T and RP18W) were isolated from mariculture fishponds in PR China. Comparisons based on 16S rRNA gene sequences showed that strains Y26 and Y57^T share 16S rRNA gene sequence similarities in the range of 95.1-98.5 % with species of the genus Bowmanella, and strains ZJ14W^T and RP18W share 16S rRNA gene sequence similarities in the range of 96.7 -98.8 % with species of the genus Amphritea, respectively. The genome sizes of strains Y26, Y57^T, ZJ14W^T and RP18W were about 4.85, 5.40, 4.70 and 4.70 Mbp with 49.5, 51.7, 51.2 and 51.3 mol% G+C content, respectively. The calculated pairwise OrthoANIu values among strains Y26, Y57^T and species of the genus Bowmanella were in the range of 72.6-83.1 %, but the value between strains Y26 and Y57^T was 96.2 %. The pairwise OrthoANIu values among strains ZJ14W^T, RP18W and other species of the genus Amphritea were all less than 93.9 %, but the value between strains ZJ14W^T and RP18W was 99.3 %. Q-8 was the major respiratory quinone of strains Y26, Y57^T, ZJ14W^T and RP18W, and the major fatty acids of these strains were all C_{16 : 1} ω7c, C_{16 : 0} and C_{18 : 1} ω7c. The predominant polar lipids of strains Y26 and Y57^T included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylinositol, but strains ZJ14W^T and RP18W only contained phosphatidylethanolamine and phosphatidylglycerol. Combining phenotypic, biochemical and genotypic characteristics, strains Y26 and Y57^T should belong to the same species and represent a novel member of the genus Bowmanella, and strains ZJ14W^T and RP18W should belong to the same species and represent a novel member of the genus Amphritea, for which the names Bowmanella yangjiangensis sp. nov. (type strain Y57^T=GDMCC 1.2180^T=KCTC 82439^T) and Amphritea pacifica sp. nov. (type strain ZJ14W^T=GDMCC 1.2203^T=KCTC 82438^T) are proposed.

Taxogenomic and Metabolic Insights into Marinobacterium ramblicola sp. nov., a New Slightly Halophilic Bacterium Isolated from Rambla Salada, Murcia

A Gram-negative, motile, rod-shaped bacteria, designated D7^T, was isolated by using the dilution-to-extinction method, from a soil sample taken from Rambla Salada (Murcia, Spain). Growth of strain D7^T was observed at 15–40 °C (optimum, 37 °C), pH 5–9 (optimum, 7) and 0–7.5% (w/v) NaCl (optimum, 3%). It is facultatively anaerobic. Phylogenetic analysis based on 16S rRNA gene sequence showed it belongs to the genus Marinobacterium. The in silico DDH and ANI against closest Marinobacterium relatives support its placement as a new species within this genus. The major fatty acids of strain D7^T were C_16:0, summed feature 3 (C_16:1 ω7c/C_16:1 ω6c) and summed feature 8 (C_18:1 ω7c/C_18:1 ω6c). The polar lipid profile consists of phosphatidylethanolamine, phosphatidylglycerol and two uncharacterized lipids. Ubiquinone 8 was the unique isoprenoid quinone detected. The DNA G + C content was 59.2 mol%. On the basis of the phylogenetic, phenotypic, chemotaxonomic and genomic characterization, strain D7^T (= CECT 9818^T = LMG 31312^T) represents a novel species of the genus Marinobacterium for which the name Marinobacterium ramblicola sp. nov. is proposed. Genome-based metabolic reconstructions of strain D7^T suggested a heterotrophic and chemolitotrophic lifestyle, as well as the capacity to biosynthetize and catabolize compatible solutes, and to degrade hydrocarbon aromatic compounds.

Leucobacter chromiisoli sp. nov., isolated from chromium-containing chemical plant soil

A Gram-stain-positive, rod-shaped, aerobic, non-motile, non-sporulating bacterial strain, designated CSA1^T, was isolated from chromium-containing soil sampled at a chemical plant. Growth of strain CSA1^T occurred at pH 6-10 (optimum, pH 7), 15-45 °C (optimum, 30 °C) and in the presence of 0.5-6.5 % (w/v) NaCl (optimum, 2 %). The 16S rRNA gene sequence of strain CSA1^T revealed the highest similarity to Leucobacter ruminantium A2^T (97.5 %), Leucobacter tardus K 70/01^T (97.3 %), Leucobacter humi Re6^T (96.6 %), Leucobacter kyeonggiensis F3-P9^T (96.2 %), Leucobacter zeae CC-MF41^T (96.1 %) and Leucobacter weissii S27^T (96.0 %). The draft genome of CSA1^T was approximately 3 350 931 bp in size with a G+C content of 70.6 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among strain CSA1^T and the selected Leucobacter species were 74.0-79.2 % (ANIb), 84.3-87.1 % (ANIm) and 21.5-25.4 % (dDDH), which are below the recommended cutoff values for species delineation. The major fatty acids were anteiso-C_15 : 0, iso-C_16 : 0 and anteiso-C_17 : 0. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid. The predominant menaquinones were MK-11, MK-8 and MK-6. The cell-wall amino acids were 2,4-diaminobutyric acid, alanine, glycine, glutamic acid and threonine. From the phenotypic, chemotaxonomic and molecular features, strain CSA1^T was considered to represent a novel species of the genus Leucobacter, for which the name Leucobacter chromiisoli sp. nov. is proposed. The type strain is CSA1^T (=JCM 34359^T=CGMCC 1.18746^T).

Halomonas diversa sp. nov., isolated from deep-sea sediment of the Pacific Ocean

A novel Gram-stain-negative, facultatively anaerobic, rod-shaped bacterium, designated as D167-6-1^T, was isolated from deep-sea sediment collected from the Pacific Ocean. The cells were catalase- and oxidase-positive, and motile by means of peritrichous flagella. Growth occurred at NaCl concentrations ranging from 0 to 19 % (optimum, 2-8 %, w/v), from pH 6 to 11 (optimum, 7-8) and at temperatures between 4 and 45 °C (optimum, 33 °C). Phylogenetic analysis based on 16S rRNA, gyrB and rpoD gene sequences and its genome sequence revealed that strain D167-6-1^T formed a monophyletic branch within the genus Halomonas and was most closely related to Halomonas saliphila, Halomonas pellis, Halomonas kenyensis, Halomonas daqingensis, Halomonas desiderata and Halomonas lactosivorans (with 98.5, 98.5, 98.4, 98.1, 97.5 and 97.8 % 16S rRNA sequence similarity, respectively). The complete genome size of strain D167-6-1^T was 4.49 Mb, with a DNA G+C content of 62.8 mol%. The estimated averagenucleotide identity and DNA-DNA hybridization values between strain D167-6-1^T and other closely related species were 77.59-85.35 % and 22.0-30.6 %, respectively. The principal cellular fatty acids (>5 %) were C_18 : 1  ω7c, C_16 : 0, C_19 : 0 cyclo ω8c, summed feature 3 (C_16 : 1  ω7c/C_16 : 1  ω6c) and C_17 : 0 cyclo. The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, aminophospholipid and two unidentified phospholipids. The predominant respiratory quinones were Q-9 and Q-8. The combined genotypic and phenotypic data show that strain D167-6-1^T represents a novel species of the genus Halomonas, for which the name Halomonas diversa sp. nov. is proposed, with the type strain D167-6-1^T (=MCCC 1A13316^T=KCTC 72441^T).

Aerobic Denitrification and Heterotrophic Sulfur Oxidation in the Genus Halomonas Revealed by Six Novel Species Characterizations and Genome-Based Analysis

Bacteria of Halomonas are widely distributed in various environments and play a substantial role in the nutrient cycle. In this report, 14 strains capable of aerobic denitrification and heterotrophic sulfur oxidation were isolated from different habitats. Based on the phenotypic, genotypic, and chemotaxonomic analyses, these strains were considered to represent six novel species of the genus Halomonas, for which the names Halomonas zhangzhouensis sp. nov. type strain CXT3-11T ( = MCCC 1A11036T = KCTC 72087T), Halomonas aerodenitrificans sp. nov. CYD-9T ( = MCCC 1A11058T = KCTC 72088T), Halomonas sulfidoxydans sp. nov. CYN-1-2T ( = MCCC 1A11059T = KCTC 72089T), Halomonas ethanolica sp. nov. CYT3-1-1T ( = MCCC 1A11081T = KCTC 72090T), Halomonas sulfidivorans sp. nov. NLG_F1ET ( = MCCC 1A13718T = KCTC 72091T), and Halomonas tianxiuensis sp. nov. BC-M4-5T ( = MCCC 1A14433T = KCTC 72092T) are proposed. Intriguingly, they formed a unique group with 11 other species designated as the "H. desiderata group." To better understand their featured metabolisms, genes involved in denitrification and sulfur oxidation were analyzed, along with 193 other available genomes of the whole genus. Consistently, complete denitrification pathways were confirmed in the "H. desiderata group," in which napA, narG, nirS, norB, and nosZ genes coexist. Their nitrite reductase NirS formed a unique evolutionary lineage, distinguished from other denitrifiers in Halomonas. In addition, diverse occurrence patterns of denitrification genes were also observed in different phylogenetic clades of Halomonas. With respect to sulfur oxidation, fccAB genes involved in sulfide oxidation commonly exist in the "H. desiderata group," while sqr genes are diverse and can be found in more species; sqr genes co-occurred with fccAB in eight strains of this study, contributing to more active sulfide oxidation. Besides, the tsdA gene, which encodes an enzyme that oxidizes thiosulfate to tetrathionate, is ubiquitous in the genus Halomonas. The widespread presence of sqr/fccAB, pdo, and tsdA in Halomonas suggests that many Halomonas spp. can act as heterotrophic sulfur oxidizers. These results provide comprehensive insights into the potential of denitrification and sulfur oxidation in the whole genus of Halomonas. With regard to the global distribution of Halomonas, this report implies their unneglectable role in the biogeochemical cycle.

Kushneria phosphatilytica sp. nov., a phosphate-solubilizing bacterium isolated from a solar saltern

A Gram-stain-negative, motile, rod-shaped, non-endospore-forming, aerobic and halophilic bacterium, designated strain YCWA18^T, was isolated from the sediment of Jimo-Daqiao saltern in China. This strain was able to grow at NaCl concentrations in the range 0.5-20 % (w/v) with optimum growth at 6 % (w/v) NaCl. Growth occurred at temperatures of 4-40 °C (optimum 28 °C) and pH 4.0-9.0 (optimum 7.0). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YCWA18^T belonged to the genus Kushneria and shared the highest sequence similarity of 98.7 % with Kushneria sinocarnis DSM 23229^T. Moreover, the phylogenetic analysis based on the 23S rRNA gene sequence also confirmed the phylogenetic position of this novel strain. The predominant fatty acids were C_16 : 0, C_17 : 0 cyclo and C_12 : 0 3-OH. The major isoprenoid quinone was Q-9 (94.2 %) and the polar lipids were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), an unidentified aminolipid (AL), an unidentified phospholipids (PL) and two unidentified lipids (L). The complete genome of strain YCWA18^T consisted of a single, circular chromosome of 3 624 619 bp, with an average G+C content of 59.1 mol%. A genome-based phylogenetic tree constructed using an up-to-date bacterial core gene set (UBCG) showed that strain YCWA18^T formed a clade with K. sinocarnis DSM 23229^T. However, the level of the ANI and dDDH values between strain YCWA18^T and K. sinocarnis DSM 23229^T were 82.3 and 24.6 %, respectively, which were low enough to distinguish strain YCWA18^T from K. sinocarnis DSM 23229^T. Overall, based on the phenotypic, chemotaxonomic, phylogenetic and genomic analyses, strain YCWA18^T represents a novel species of genus Kushneria. The name Kushneria phosphatilytica sp. nov. is proposed, with the type strain YCWA18^T (=CGMCC 1.9149^T=NCCB 100306^T).

Genomic analysis of a novel species Halomonas shambharensis isolated from hypersaline lake in Northwest India

Genome analysis of Halomonas shambharensis, a novel species, was performed to understand the osmoprotectant strategies used by the strain to overcome the salinity stress and to explore the prospective industrial uses. It will also help to better understand the ecological roles of Halomonas species in hypersaline habitats. Ultrastructure of the cell was determined by using transmission electron microscopy. Standard microbiological methods were used to find out growth parameters and heterotrophic mode of nutrition. For Genome analysis, complete bacterial genome sequencing was performed using the Oxford Nanopore MinION DNA Sequencer. Assembly, annotation and finishing of the obtained sequence were done by using a Prokaryotic Genome Annotation Pipeline (PGAP) (SPAdes v. 3.10.1). Predicted Coading sequences (CDSs) obtained through the PGAP were used for functional annotation using Clusters of Orthologous Groups and Kyoto Encyclopedia of Genes and Genomes (KEGG) platforms. The H. shambharensis was found to be a Gram-stain-negative, rod-shaped bacterium, motile with a peritrichous flagella. The H. shambharensis bacterium can grow in a wide range of temperature (from 25 to 65 °C), pH (pH 4 to pH 12.0) and salt concentration (5.0% NaCl to 30.0% NaCl). After annotation and assembly, the total genome size obtained was 1,533,947 bp, which revealed 146 subsystems, 3847 coding sequences, and 19RNAs with G+C content of 63.6%. Gene annotation identified the genes related to various metabolic pathways, including carbohydrate metabolism, fatty acid metabolism and stress tolerance. The genomic dataset of H. shambharensis will be useful for analysis of protein-coding gene families and how these coding genes are significant for the survival and metabolism among the different species of Halomonas. The complete genome sequence presented here will help to unravel the biotechnological potential of H. shambharensis for production of the high-value products such as betaine, or as a source of gene-mining for individual enzymes.

Halomonas azerbaijanica sp. nov., a halophilic bacterium isolated from Urmia Lake after the 2015 drought

A novel, slightly halophilic bacterium, designated TBZ202^T, was isolated from water of Urmia Lake, in the Azerbaijan region of north-west Iran. The strain was facultatively anaerobic, Gram-stain-negative, rod-shaped and motile. Colonies were creamy, circular, convex and shiny. It grew at NaCl concentrations of 0-12 % (w/v) (optimum 3-5 % w/v), at temperatures of 20-45 °C (optimum 30 °C) and at pH 5.0-10.0 (optimum pH 7.0). Based on the 16S rRNA gene sequence, strain TBZ202^T belongs to the genus Halomonas in the Halomonadaceae and the most closely related species are Halomonas gudaonensis CGMCC 1.6133^T (98.6 % similarity), Halomonas ventosae Al12^T (96.8 %) and Halomonas rambilicola RS-16^T (96.6%). The G+C content was 67.9 % and the digital DNA-DNA hybridization and average nucleotide identity values with H. gudaonensis were 35.8 and 83.8 %, respectively, indicating that the isolate differs from all species described. The major fatty acids were C_{18 : 1} ω7c, C_{16 : 0} and C_{16 : 1} ω7c. The only respiratory quinone detected was Q-9 and polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, aminophospholipid and three unknown phospholipids. On the basis of a polyphasic taxonomic analysis, the isolate is considered to represent a novel species of the genus Halomonas, for which the name Halomonas azerbaijanica sp. nov. is proposed. The type strain is TBZ202^T (=KCTC 62817^T=CECT 9693^T).

Heat stress during late gestation disrupts maternal microbial transmission with altered offspring's gut microbial colonization and serum metabolites in a pig model

Heat stress (HS) during gestation has been associated with negative outcomes, such as preterm birth or postnatal metabolic syndromes. The intestinal microbiota is a unique ecosystem playing an essential role in mediating the metabolism and health of mammals. Here we hypothesize late gestational HS alters maternal microbial transmission and structures offspring's intestinal microbiota and serum metabolic profiles. Our results show maternal HS alters bacterial β-diversity and composition in sows and their piglets. In the maternal intestine, genera Ruminococcaceae UCG-005, [Eubacterium] coprostanoligenes group and Halomonas are higher by HS (q < 0.05), whereas the populations of Streptococcus, Bacteroidales RF16 group_norank and Roseburia are decreased (q < 0.05). In the maternal vagina, HS mainly elevates the proportions of phylum Bacteroidetes and Fusobacteria (q < 0.05), whereas reduces the population of Clostridiales Family XI (q < 0.05). In the neonatal intestine, maternal HS promotes the population of Proteobacteria but reduces the relative abundance of Firmicutes (q < 0.05). Moreover, the core Operational taxonomic units (OTU) analysis indicates the proportions of Clostridium sensu stricto 1, Romboutsia and Turicibacter are decreased by maternal HS in the intestinal and vaginal co-transmission, whereas that of phylum Proteobacteria and Epsilonbacteraeota, such as Escherichia-Shigella, Klebsiella, Acinetobacter, and Comamonas are increased in both the intestinal and vaginal co-transmission and the vagina. Additionally, Aeromonas is the only genus that is transmitted from environmental sources. Lastly, we evaluate the importance of neonatal differential OTU for the differential serum metabolites. The results indicate Acinetobacter significantly contributes to the differences in the adrenocorticotropic hormone (ACTH) and glucose levels due to HS (P < 0.05). Further, Stenotrophomonas is the most important variable for Cholesterol, low-density lipoprotein (LDL), diamine oxidase (DAO), blood urea nitrogen (BUN) and 5-hydroxytryptamine (5-HT) (P < 0.10). Overall, our data provides evidence for the maternal HS in establishing the neonatal microbiota via affecting maternal transmission, which in turn affects the maintenance of metabolic health.

Halomonas lysinitropha sp. nov., a novel halophilic bacterium isolated from a hypersaline wetland

We carried out a polyphasic taxonomic study on a new halophilic strain designated 3(2)^T, isolated from Meighan wetland, Iran. Cells of the novel strain were Gram-stain-negative, non-hemolytic, catalase- and oxidase-positive, rod-shaped, non-endospore-forming and motile. Cell growth occurred at 3-15 % NaCl (w/v; optimum, 5 %), pH 7.0-9.0 (optimum, pH 7.5-8.0) and 15-35 °C (optimum, 30 °C). 16S rRNA gene sequence comparisons confirmed the affiliation of strain 3(2)^T to the class Gammaproteobacteria and the genus Halomonas with highest similarity to Halomonas daqiaonensis YCSA28^T (98.4 %) and Halomonas ventosae Al12^T (97.9 %). Experimental and in silico DNA-DNA hybridization values were 42.7 and 35.1% with H. daqiaonensis IBRC-M 10931^T and 48 and 35.2% with H. ventosae IBRC-M 10566^T, respectively, and indicated that they are different members of the same genus. The genome of the type strain was characterized by a size of 3.83 Mbp with 63 scaffolds and a G+C content of 64.8 mol%. Moreover, the average nucleotide identity values against H. ventosae Al12^T and H. daqiaonensis YCSA28^T were 88.8 and 88.5 %, respectively. The predominant respiratory quinone was Q-9 (92 %) with Q-8 (8 %) as a minor component. Major fatty acids were C_16 : 0 cyclo, C_19 : 0 ω8c, C_16 : 1 ω7c and/or iso-C_15:0 2-OH, C_12 : 0 3-OH and C_18 : 1 ω7c. The polar lipid profile of the strain contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphoaminoglycolipid and four unidentified phospholipids. According to our results, strain 3(2)^T could be classified as a novel species in the genus Halomonas for which the name Halomonas lysinitropha sp. nov. is proposed. The type strain is 3(2)^T (=IBRC M 10929^T=LMG 29450^T=CIP 111708^T).

Genome Analysis of a Marine Bacterium Halomonas sp. and Its Role in Nitrate Reduction under the Influence of Photoelectrons

The solar light response and photoelectrons produced by widespread semiconducting mineral play important roles in biogeochemical cycles on Earth's surface. To explore the potential influence of photoelectrons generated by semiconducting mineral particles on nitrate-reducing microorganisms in the photic zone, a marine heterotrophic denitrifier Halomonas sp. strain 3727 was isolated from seawater in the photic zone of the Yellow Sea, China. This strain was classified as a Halomonadaceae. Whole-genome analysis indicated that this strain possessed genes encoding the nitrogen metabolism, i.e., narG, nasA, nirBD, norZ, nosB, and nxr, which sustained dissimilatory nitrate reduction, assimilatory nitrate reduction, and nitrite oxidation. This strain also possessed genes related to carbon, sulfur, and other metabolisms, hinting at its substantial metabolic flexibility. A series of microcosm experiments in a simulative photoelectron system was conducted, and the results suggested that this bacterial strain could use simulated photoelectrons with different energy for nitrate reduction. Nitrite, as an intermediate product, was accumulated during the nitrate reduction with limited ammonia residue. The nitrite and ammonia productions differed with or without different energy electron supplies. Nitrite was the main product accounting for 30.03% to 68.40% of the total nitrogen in photoelectron supplement systems, and ammonia accounted for 3.77% to 8.52%. However, in open-circuit systems, nitrite and ammonia proportions were 26.77% and 11.17%, respectively, and nitrogen loss in the liquid was not observed. This study reveals that photoelectrons can serve as electron donors for nitrogen transformation mediated by Halomonas sp. strain 3727, which reveals an underlying impact on the nitrogen biogeochemical cycle in the marine photic zone.

Halomonas pellis sp. nov., a moderately halophilic bacterium isolated from wetsalted hides

A Gram-stain-negative, moderately halophilic strain, designated strain L5T, was isolated from wetsalted hides collected from Chengdu, south-west PR China. The cells were motile, facultative aerobic, short rod-shaped and non-endospore-forming. Growth of strain L5T occurred at pH 6–10 (optimum, pH 8), 10–45 °C (optimum, 30 °C) and in the presence of 1–17 % (w/v) NaCl (optimum, 10 %). Results of phylogenetic analyses based on 16S rRNA, gyrB and rpoD gene sequences and its genome revealed that strain L5T belonged to the genus Halomonas . Strain L5T was found to be most closely related to the type strains of Halomonas saliphila , Halomonas lactosivorans , Halomonas kenyensis , Halomonas daqingensis and Halomonas desiderata (98.8, 98.6, 98.3, 97.9 and 97.4 % 16S rRNA gene sequence similarity, respectively). The draft genome was approximately 4.2 Mb in size with a G+C content of 63.5 mol%. The average nucleotide identity (ANI) and digital DNA–DNA hybridization values among strain L5T and the selected Halomonas species were 83.3–88.9 % (ANIm), 71.1–87.3 % (ANIb) and 20.2–34.6 %, which are below the recommended cutoff values. Major fatty acids were C16 : 0, C16 : 1  ω7c, C18 : 1  ω7c and C19 : 0 cyclo ω8c and the predominant ubiquinone was Q-9, with minor ubiquinone Q-8 also present. The phospholipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, four unidentified aminophospholipids and three unidentified phospholipids. Based on the mentioned polyphasic taxonomic evidence, strain L5T represents a novel species within the genus Halomonas , for which Halomonas pellis sp. nov. is proposed. The type strain is L5T (=CGMCC 1.17335T=KCTC 72573T).

Characteristics of spatial and seasonal bacterial community structures in a river under anthropogenic disturbances

In this study, the seasonal characteristics of microbial community compositions at different sites in a river under anthropogenic disturbances (Maozhou River) were analyzed using Illumina HiSeq sequencing. Taxonomic analysis revealed that Proteobacteria was the most abundant phylum in all sites, followed by Actinobacteria, Bacteroidetes, Chloroflexi, Acidobacteria and Firmicutes. The variations of the community diversities and compositions between the seasons were not significant. However, significant differences between sites as well as water and sediment samples were observed. These results indicated that sites under different levels of anthropogenic disturbances have selected distinct bacterial communities. pH, dissolved oxygen (DO), concentrations of total nitrogen (TN) and heavy metals were the main factors that influence the diversity and the composition of bacterial community. Specifically, the relative abundance of Proteobacteria was negatively correlated with pH and DO and positively correlated with TN, while Actinobacteria and Verrucomicrobia showed the opposite pattern. Moreover, positive correlations between the relative abundances of Firmicutes and Bacteroidetes and the concentration of heavy metals were also found. Results of functional prediction analysis showed no significant differences of the carbon, nitrogen and phosphorus metabolism across the sites and seasons. Potential pathogens such as Vibrio, Arcobacter, Acinetobacter and Pseudomonas were found in these samples, which may pose potential risks for environment and human health. This study reveals the effect of anthropogenic activities on the riverine bacterial community compositions and provides new insights into the relationships between the environmental factors and the bacterial community distributions in a freshwater ecosystem under anthropogenic disturbances.

Halomonas rituensis sp. nov. and Halomonas zhuhanensis sp. nov., isolated from natural salt marsh sediment on the Tibetan Plateau

Two novel Gram-stain-negative, aerobic and non-motile rods bacteria, designated TQ8S^T and ZH2S^T, were isolated from salt marsh sediment collected from the Tibetan Plateau. Strain TQ8S^T was found to grow at 10-40 °C (optimum, 30 °C), pH 6.0-11.0 (optimum, pH 8.0-9.0) and in the presence of 2-12 % (w/v) NaCl (optimum, 6-8 %). Strain ZH2S^T was found to grow at 15-40 °C (optimum, 30 °C), pH 7.0-10.0 (optimum pH 9.0) and in the presence of 2-10 % (w/v) NaCl (optimum, 4-6 %). Phylogenetic analysis based on the 16S rRNA gene sequences showed that strains TQ8S^T and ZH2S^T shared 99.07 % sequence similarity between each other and were affiliated with the genus Halomonas, sharing 97.48 % and 97.41 % of sequence similarity to their closest neighbour Halomonas sulfidaeris Esulfide1^T, respectively. DNA-DNA hybridization analyses showed 61.0 % relatedness between strains TQ8S^T and ZH2S^T. The average nucleotide identity and the average amino acid identity values between the two genomes were 92.33 and 92.84 %, respectively. The values between the two strains and their close phylogenetic relatives were all below 95 %. The major respiratory quinones of strain TQ8S^T were Q-9 and Q-8, while that of ZH2S^T was Q-9. The main fatty acids shared by the two strains were C_18 : 1  ω6c and/or C_18 : 1  ω7c, C_16 : 1  ω6c and/or C_16 : 1  ω7c, C_16 : 0 and C_12 : 0 3-OH. Strain ZH2S^T can be distinguished from TQ8S^T by a higher proportion of C_19 : 0 cyclo ω8c. The G+C content of the genomic DNA of strains TQ8S^T and ZH2S^T were 57.20 and 57.14 mol%, respectively. On the basis of phenotypic distinctiveness and phylogenetic divergence, the two isolates are considered to represent two novel species of the genus Halomonas, for which the names Halomonas rituensis sp. nov (type strain TQ8S^T=KCTC 62530^T=CICC 24572^T) and Halomonas zhuhanensis sp. nov (type strain ZH2S^T=KCTC 62531^T=CICC 24505^T) are proposed.

Biosorption of Cr(VI) by Halomonas sp. DK4, a halotolerant bacterium isolated from chrome electroplating sludge

This study evaluated Cr(VI) biosorption by a halotolerant gram-negative bacterium Halomonas sp. DK4 isolated from chrome electroplating sludge. The bacterium could withstand high concentrations of Cr(VI) exhibiting a minimal inhibitory concentration (MIC) of 250 mg/L. Plackett-Burman design confirmed glucose, KH₂PO₄, NaCl, inoculum size, and initial Cr(VI) concentration as significant variables influencing the Cr(VI) removal ability of the bacterium. The suspended culture of Halomonas sp. DK4 was able to remove 81% (100 mg/L) of Cr(VI) in optimized MSM medium from aqueous solutions within 48 h. The bacterium also removed 59% Cr(VI) in the presence of 15% NaCl concentration within 72 h. The main mechanism involved in Cr(VI) removal by Halomonas sp. DK4 was determined to be biosorption which was best explained using the Langmuir isotherm model, wherein the maximum adsorption of 150.7 mg/g was observed under equilibrium conditions. Kinetic studies reveal that chemisorption of Cr(VI) by Halomonas sp. DK4 was a rate-limiting process which followed pseudo-second-order kinetics (R² = 0.99). Bacterial biomass exhibited maximum adsorption of 70.3% Cr(VI) at an initial concentration of 100 mg/L under optimal conditions. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of hydroxyl, carboxyl, amide, and phosphate groups on the bacterial surface which may be involved in Cr(VI) adsorption. Scanning electron microscopy coupled energy dispersive X-ray (SEM-EDX) analysis revealed morphological changes in the bacterial cell and accumulation of Cr(VI) on the cell surface. These results suggest the potential application of Halomonas sp. DK4 in the removal of Cr(VI) from saline chromium-containing industrial wastewaters.

Effect of a fungus, Hypoxylon spp., on endophytes in the roots of Asparagus

The fungal isolate Hypoxylon spp. (Sj18) was isolated from the root of pecan. It might have effects on the plant's stress tolerance and endophytic community. Inoculation experiments were carried out on the roots of Asparagus with normal and inactivated Sj18, and the diversity and community structure of endophytes in the root of inoculated Asparagus were studied. It was found that Sj18 fungi affected the endophytic community of Asparagus roots. From being a low-abundance genus, the salt-tolerant bacterium Halomonas became the dominant genus. In order to verify that Sj18 can improve salt tolerance, Arabidopsis thaliana was inoculated with Sj18 in a salt tolerance test. The result showed that A. thaliana grew better in a high salt environment after inoculation with Sj18. Sj18 changed the microbe diversity, community composition and structure of endophytes in the roots of Asparagus, which increased the bacterial diversity. A total of 16 phyla and 184 genera of bacteria were detected. However, the diversity of fungi decreased.

Gracilibacillus salitolerans sp. nov., a moderate halophile isolated from saline soil in Northwest China

A moderately halophilic strain, designated SCU50T, was recovered from a saline soil sample and characterized by a polyphasic approach. The 16S rRNA gene sequence analysis showed that strain SCU50T belonged to the genus Gracilibacillus and was most closely related to Gracilibacillus thailandensis TP2-8T (98.1 % similarity) and Gracilibacillus orientalis XH-63T (97.7 %). Genomic average nucleotide identity and digital DNA–DNA hybridization analyses confirmed the separate species status of the new isolate relative to other recognized Gracilibacillus species. The genome size was about 5.09 Mbp and the DNA G+C content was 36.7 mol%. The strain grew optimally at 10–15 % (w/v) NaCl, pH 6.5–7.5 and 25–30 °C. It contained anteiso-C15 : 0, iso-C15 : 0 and anteiso-C17 : 0 as the dominant fatty acids and menaquinone-7 as the major respiratory quinone. The polar lipid profile was examined and found to comprise diphosphatidylglycerol, phosphatidylglycerol, one unidentified phospholipid and one unidentified lipid. The cell-wall peptidoglycan type was A1γ based on meso-diaminopimelic acid. Combining the data from phenotypic, chemotaxonomic, genomic and phylogenetic characterization, it was concluded that strain SCU50T should be assigned as representing a novel species within the genus Gracilibacillus . Thus, a novel taxon named Gracilibacillus salitolerans sp. nov. was first established, with SCU50T (=CGMCC 1.17336T=KCTC 43107T) as the type strain.

Decolorization of Reactive Black 5 and Reactive Red 152 Azo Dyes by New Haloalkaliphilic Bacteria Isolated from the Textile Wastewater

Textile wastewaters are usually alkali and saline, so using haloalkaliphilic bacteria can be the best option for the treatment of wastewater. This study aimed at the decolorization of textile Reactive Black 5 and Reactive Red 152 dyes using new haloalkaliphilic bacteria isolated from the textile wastewater. Among 50 strains of bacteria isolated from the effluent of Kashan textile industry, three bacterial strains, namely D1, D2 and E49, exhibited high decolorization abilities for Reactive Black 5 and Reactive Red 152 dyes. Decolorization was evaluated through spectrophotometry at maximum absorbance wavelengths of 607 and 554 nm for Reactive Black 5 and Reactive Red 152, respectively. The highest decolorization percentage was observed at a dye concentration of 50 mg L^-1. Aerobic conditions, 5% of the yeast extract and salt, 10% of peptone and glucose as nitrogen and carbon sources, respectively, and a pH range of 9-12 were considered as the optimal conditions for decolorization. The consortium of three haloalkaliphilic isolates showed a remarkable ability for decolorization of the Reactive Black 5 (87%) and Reactive Red 152 (85%) dyes. The consortium exhibited higher decolorization ability for the textile effluent, compared to individual bacterial inoculations. According to phenotypic characterization experiments and phylogenetic analyses based on comparing 16S rDNA sequence, the mentioned strains belonged to the genus Halomonas.

Halomonas lactosivorans sp. nov., isolated from salt-lake sediment

A bacteria strain, designated CFH 90008T, was isolated from a salt lake sediment sample collected from Yuncheng city, Shanxi Province, PR China. Strain CFH 90008T was Gram-stain-negative, strictly aerobic, motile with lateral flagella and rod-shaped. Colonies were yellow, circular and smooth. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain CFH 90008T belonged to the genus Halomonas , showing highest sequence similarity to Halomonas daqingensis DQD2-30T (98.6 %), Halomonas saliphila LCB169T (98.5 %), Halomonas desiderata FB2T (98.1 %) and Halomonas kenyensis AIR-2T (98.0 %). Good growth was observed at 10–50 °C, pH 6.0–9.0 and with NaCl concentration from 1.0 to 12.0 % (w/v). The predominant quinone was Q9. The major fatty acid (>10 %) was C18 : 1 ω7c, C16 : 0 and C16 : 1 ω7c. The genome of strain CFH 90008T was 4.36 Mbp with a genomic DNA G+C content of 66.7 mol%. Based on low average nucleotide identity and DNA–DNAhybridization results, chemotaxonomic characteristics, and differential physiological properties, strain CFH 90008T could not be classified into any recognized species of the genus Halomonas . Therefore, a new species, for which the name Halomonas lactosivorans sp. nov. is proposed. The type strain is CFH 90008T (=DSM 103220T=KCTC 52281T).

Roseovarius bejariae sp. nov., a moderately halophilic bacterium isolated from a hypersaline steep-sided river bed

An aerobic, Gram-stain-negative ovoid, designated as strain A21T, was isolated using the dilution-to-extinction method from a soil sample taken from Rambla Salada, an athalassohaline habitat located in Murcia (south-eastern Spain). Strain A21T is non-motile, has a respiratory metabolism and grows at NaCl concentrations within the range 0.5–15 % (w/v) [optimum, 5 % (w/v)], at 5–35 °C (optimum, 28 °C) and at pH 6–8 (optimum, pH 7.0). This strain is positive for catalase activity, oxidase activity and nitrate reduction. The 16S rRNA gene sequence indicates that it belongs to the genus Roseovarius in the class Alphaproteobacteria . The most closely related species are Roseovarius pacificus and Roseovarius halotolerans to which the strain A21T shows 16S rRNA gene sequence similarity values of 98.06 and 97.7 %, respectively. The average nucleotide identity in blast and digital DNA–DNA hybridization values between strain A21T and R. pacificus LMG 24575T are 76.8 and 21 %, respectively. The DNA G+C content based on the genome is 61.28 mol%. The major fatty acids (>5 % of the total fatty acids) of strain A21T are C18 : 1 ω7c/C18 : 1 ω6c and C16 : 0. The only detected isoprenoid quinone in strain A21T is ubiquinone 10 (Q-10). The polar lipid profile contains phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and three unidentified polar lipids. Based on the phylogenetic, genotypic, phenotypic and chemotaxonomic data, the strain represents a novel species of the genus Roseovarius , for which the name Roseovarius bejariae sp. nov. is proposed. Strain A21T (=CECT 9817T=LMG 31311T) is the type strain.