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We cloned a xylanase gene (xynT) from marine bacterium Echinicola rosea sp. nov. JL3085T and recombinantly expressed it in Escherichia coli BL21. This gene encoded a polypeptide with 379 amino acid residues and a molecular weight of ~43 kDa. Its amino acid sequence shared 45.3% similarity with an endoxylanase from Cellvibrio mixtus that belongs to glycoside hydrolases family 10 (GH10). The XynT showed maximum activity at 40 °C and pH 7.0, and a maximum velocity of 62 μmoL min−1 mg−1. The XynT retained its maximum activity by more than 69%, 51%, and 26% at 10 °C, 5 °C, and 0 °C, respectively. It also exhibited the highest activity of 135% in the presence of 4 M NaCl and retained 76% of its activity after 24 h incubation with 4 M NaCl. This novel xylanase, XynT, is a cold-active and halotolerant enzyme that may have promising applications in drug, food, feed, and bioremediation industries.

Background Aureobasidium pullulans is a black-yeast-like fungus used for production of the polysaccharide pullulan and the antimycotic aureobasidin A, and as a biocontrol agent in agriculture. It can cause opportunistic human infections, and it inhabits various extreme environments. To promote the understanding of these traits, we performed de-novo genome sequencing of the four varieties of A. pullulans. Results The 25.43-29.62 Mb genomes of these four varieties of A. pullulans encode between 10266 and 11866 predicted proteins. Their genomes encode most of the enzyme families involved in degradation of plant material and many sugar transporters, and they have genes possibly associated with degradation of plastic and aromatic compounds. Proteins believed to be involved in the synthesis of pullulan and siderophores, but not of aureobasidin A, are predicted. Putative stress-tolerance genes include several aquaporins and aquaglyceroporins, large numbers of alkali-metal cation transporters, genes for the synthesis of compatible solutes and melanin, all of the components of the high-osmolarity glycerol pathway, and bacteriorhodopsin-like proteins. All of these genomes contain a homothallic mating-type locus. Conclusions The differences between these four varieties of A. pullulans are large enough to justify their redefinition as separate species: A. pullulans , A. melanogenum , A. subglaciale and A. namibiae . The redundancy observed in several gene families can be linked to the nutritional versatility of these species and their particular stress tolerance. The availability of the genome sequences of the four Aureobasidium species should improve their biotechnological exploitation and promote our understanding of their stress-tolerance mechanisms, diverse lifestyles, and pathogenic potential.

Thiol peroxidases have been identified as antioxidant enzymes in different organisms. However, there have been only a few reports on deleting or overexpressing its gene to characterize its function. Recently, the ability of the enzyme thiol peroxidase belonging to the Micrococcus sp. IITD107 on asphaltene biotransformation has been reported. Here, we report the construction of deletion and overexpression strains of tpx and compared them with the wild-type strain of Micrococcus sp. IITD107. For this purpose, whole-genome sequencing of the strain was carried out. The genome sequence revealed the presence of only one copy of the tpx gene and several other genes which might play a role in stress response, polyaromatic hydrocarbon (PAH) degradation, etc. The tpx deletion mutant was constructed by homologous recombination. For overexpression, a pRC4 replicon from Rhodococcus was used, and the gene for tpx was expressed under the control of an IPTG-inducible tac promoter. The replicon was found to be stable in Micrococcus . The deletion mutant showed coccoid morphology, and the doubling time was found to be 7.2 h as compared to the doubling times of 3.5 h for the wild-type strain and 4.5 h for the overexpression strain in LB medium. The deletion strain was unable to grow in the presence of high salt or hydrogen peroxide concentrations, whereas the overexpression strain showed less growth as compared to the wild type. Further, about a 50% decrease and only a 5% increase in the rate of asphaltene biotransformation in the deletion and overexpression strains, respectively, were observed. Overall, our results suggest that thiol peroxidase helps not only in asphaltene biotransformation but also aids the bacterium to survive in the presence of stress agents such as salt and hydrogen peroxide. Key points • Gene for thiol peroxidase confirmed to enhance asphaltene biotransformation • Change in growth and morphology • Alteration in halotolerance and stress response

The Onygenales represent a versatile group of fungi that primarily inhabit soils, degrading cellulose and/or keratin. While some are known human pathogens, others are osmotolerant or colonize chitin substrates such as insects. The marine environment, characterized by 3.5% salinity and chitin as the dominant polysaccharide, represents an intriguing niche for these fungi. However, fungal diversity in this environment remains poorly studied. This study investigated the culturable diversity of Onygenales in marine sediments, explored their global biogeography, and assessed their adaptability to marine conditions. Marine sediments were collected near river mouths and other coastal areas along the Catalan coast (Spain). Identification was based on a polyphasic approach; global distribution patterns were assessed through the GlobalFungi database, and adaptability was evaluated through osmotolerance and substrate degradation assays (cellulose, chitin, keratin). We recovered 32 strains, of which 24 represented 16 known species distributed in Gymnascella , Gymnoascus , Narasimhella , and Sporendonema (Gymnoascaceae) ; Malbranchea (Malbrancheaceae) ; Myriodontium (Neoarthropsidaceae) ; and Aphanoascus and Byssoonygena (Onygenaceae) . The remaining eight strains were delineated as six novel species, including a new genus: Gymnoascoideus alboluteus sp. nov. , Malbranchea parafilamentosa sp. nov. , M. sedimenticola sp. nov. , M. seminuda sp. nov. , M. sexualis sp. nov. , and Deilomyces minimus gen. et sp. nov. In addition, all strains degraded cellulose, and most tolerated up to 10% NaCl. Only four species that also degraded chitin ( Malbranchea parafilamentosa , M. sexualis , Myriodontium keratinophilum , and Sporendonema casei ) could be considered facultative marine fungi. This work evidences the great diversity of onygenalean fungi in marine sediments and underscores their metabolic adaptability to marine conditions.

Abstract Zygosaccharomyces rouxii is an osmotolerant and halotolerant yeast that can participate in fermentation. To understand the mechanisms of salt and sugar tolerance, the transcription levels of Z. rouxii M 2013310 under 180 g/L NaCl stress and 600 g/L glucose stress were measured. The transcriptome analysis showed that 2227 differentially expressed genes (DEGs) were identified under 180 g/L NaCl stress, 1530 DEGs were identified under 600 g/L glucose stress, and 1278 DEGs were identified under both stress conditions. Then, KEGG enrichment analyses of these genes indicated that 53.3% of the upregulated genes were involved in the ergosterol synthesis pathway. Subsequently, quantitative PCR was used to verify the results, which showed that the genes of the ergosterol synthesis pathway were significantly upregulated under 180 g/L NaCl stress. Finally, further quantitative testing of ergosterol and spotting assays revealed that Z. rouxii M 2013310 increased the amount of ergosterol in response to high salt stress. These results highlighted the functional differences in ergosterol under sugar stress and salt stress, which contributes to our understanding of the tolerance mechanisms of salt and sugar in Z. rouxii. Ergosterol synthesis has functional differences in Zygosaccharomyces rouxii response to high salt and high sugar stress.

In recent years, the low Zn content of wheat has become critical. Consequently, solutions that can improve the Zn nutrition of wheat are highly researched. In the present investigation, we aimed to evaluate the potential benefits of phosphate-solubilizing bacteria isolated from Ziziphus lotus on wheat seedling growth. Based on the phosphate-solubilizing criteria, four isolated strains, J16, J143, J146, and J158, were identified by 16SrRNA gene sequencing as Pseudomonas moraviensis, Bacillus halotolerans, Enterobacter hormaechei, and Pseudomonas frederiksbergensis, respectively. Studies of the conventional properties of plant growth-promoting rhizobacteria (PGPR) showed that E. hormaechei J146 produced up to 550 mg·L−1 of indole-3-acetic acid (IAA). Siderophores and ammonia were produced by all strains but cellulase was restricted to B. halotolerans J143, whereas proteases were missing in E. hormaechei J146 and P. frederiksbergensis J158. E. hormaechei J146 tolerate up to 1.5 mg·L−1 of copper and cadmium, while B. halotolerans J143 withstood 1.5 mg·L−1 of nickel. Strains B. halotolerant J143, E. hormaechei J146, and P. frederiksbergensis J158 remarkably improved wheat seed germination, plant growth, and Zn absorption. Lastly, nutrient measurement revealed that a wheat plant inoculated with E. hormaechei J146 and P. frederiksbergensis J158 increased its nitrogen and potassium uptake by up to 17%.

The genus Sporendonema ( Gymnoascaceae , Onygenales ) was introduced in 1827 with the type species S . casei for a red mould on cheese. Cheese is a consistent niche for this species. Sphaerosporium equinum is another species classified in Gymnoascaceae and has also been reported from cheese. Recently, other habitats have been reported for both Sporendonema casei and Sphaerosporium equinum . The present study aimed to investigate the taxonomy of Sporendonema and Sphaerosporium , as well as a close neighbour, Arachniotus . Two strains of Hormiscium aurantiacum , another related cheese-associated species were also included in the analyses. Strains were evaluated in terms of macro- and micromorphology, physiology including salt tolerance, growth rate at different temperatures, casein degradation, cellulase activity, lipolytic activity, and multi-locus phylogeny with sequences of the nuclear ribosomal internal transcribed spacer region, the D1-D2 region of the large subunit and partial β-tubulin locus sequences. The results showed that the analysed species were congeneric, and the generic names Arachniotus and Sphaerosporium should be reduced to the synonymy of Sporendonema . Therefore, four new combinations as well as one lectotype and one epitype were designated in Sporendonema . Two strains attributed to Sphaerosporium equinum from substrates other than cheese were found to be phylogenetically and morphologically deviant and were introduced as a new species named Sporendonema isthmoides .

Recent research highlighted the need to include experimental estimates of tolerance limits to varying environmental conditions when investigating what factors limit species distributions. However, most niche approaches are only based on the statistical dependence between environmental and occurrence data. Here, we combined field data with survival experiments to assess the role of salinity as a limiting factor in the distribution of two species of exotic ostracods from the Iberian Peninsula. Vizcainocypria viator is a free-living species associated with rice fields and Ankylocythere sinuosa is a commensal of the red swamp crayfish (Procambarus clarkii). Experiments and field data indicate that the distribution of V. viator is limited by adult survival at low and high salinities (below electrical conductivity of 0.6 mS/cm and above 10 mS/cm). In the case of A. sinuosa, the analysis of field data shows that its prevalence is negatively affected by high salinity, whereas experiments indicate an optimal survival at high salinities (conductivity above 10.2 mS/cm), thus suggesting that high salinity may impact A. sinuosa distribution indirectly through affecting host traits (e.g. reduced activity). The habitat of close ancestors (marine versus non-marine respectively for A. sinuosa and V. viator) most likely explains the contrasting differences in salinity tolerance between both ostracod species.

Hyper soil salinity is currently one of the major concerns for global agricultural yield as it directly hinders the qualitative and quantitative aspects of agronomic outcomes. Owing to ever-increasing food requirements and a vast proportion of saline agricultural land in the world, developing salinity-resilient crops is of utmost need. To address this issue, various approaches based on conventional breeding as well as biotechnological and omics-based strategies have been explored by researchers and plant breeders. Out of them, genetic engineering-based alterations of plant genomes via inserting/overexpressing beneficial salt-responsive genes originating from different organisms have shown great potential and thus explored heavily. Interestingly, a group of halotolerant organisms, plants, algae, fungi, and bacteria, collectively referred to as halobiome, holds advantageous physical, chemical, and molecular characteristics for survival in the hypersaline environment. These characteristics include effective distribution and compartmentalization of ions, elevated production of the osmoprotectants, improved activity of antioxidant machinery, and regulated synthesis of phytohormones. There are several genes from halobiome identified and successfully used to improve the salt tolerance level of glycophytic crops. However, the gene pool from the halobiome is far from its full-potential exploration. Besides, non-coding RNAs also present a potent resource to be utilized for enhancing the salinity tolerance in crop plants. Further, the use of priming agents and biofertilizers from the halobiome sources is also turning into an effective solution for plant growth enhancement and salinity tolerance. In the current review, we present the current status and recent developments in identifying and exploring halotolerant gene pools (coding and non-coding) from the constituent members of halobiome and their exploration in engineering salt-tolerant crops. Technological advancements and challenges for their full-potential exploration in crop improvement programs have been discussed. The review also provides futuristic insights about the unexplored organisms or genes from halobiome in developing salt resilience in crops.

Background The black yeast Hortaea werneckii (Dothideomycetes, Ascomycota) is one of the most extremely halotolerant fungi, capable of growth at NaCl concentrations close to saturation. Although dothideomycetous fungi are typically haploid, the reference H. werneckii strain has a diploid genome consisting of two subgenomes with a high level of heterozygosity. Results In order to explain the origin of the H. werneckii diploid genome we here report the genome sequencing of eleven strains isolated from different habitats and geographic locations. Comparison of nine diploid and two haploid strains showed that the reference genome was likely formed by hybridization between two haploids and not by endoreduplication as suggested previously. Results also support additional hybridization events in the evolutionary history of investigated strains, however exchange of genetic material in the species otherwise appears to be rare. Possible links between such unusual reproduction and the extremotolerance of H. werneckii remain to be investigated. Conclusions H. werneckii appears to be able to form persistent haploid as well as diploid strains, is capable of occasional hybridization between relatively heterozygous haploids, but is otherwise limited to clonal reproduction. The reported data and the first identification of haploid H. werneckii strains establish this species as a good model for studying the effects of ploidy and hybridization in an extremotolerant system unperturbed by frequent genetic recombination.