Anion-type modulates the effect of salt stress on saline lake bacteria

Dark septate endophytic fungus Alternaria sp. 17463 regulates various antioxidant enzymes and compounds to mitigate salt stress caused by different anion salts

In the field of agricultural and environmental management, understanding how dark septate endophytic fungi (DSE) like Alternaria sp. 17463 respond to salt stress is crucial. Prior research has yet to fully explore the anion-specific responses of DSE to salt stress. In this study, we delve into the physiological and biochemical responses of Alternaria sp. 17463 under NaCl and Na2SO4 stress, employing a suite of analytical techniques. We discovered a marked disparity in fungal tolerance, with NaCl inducing a 50 % growth reduction at 0.6 M and a complete growth arrest at 1.4 M, contrasting with Na2SO4's milder 30 % impact at the highest tested concentration. Cell membrane integrity was severely compromised under NaCl, with a 70 % increase in permeability and a 40 % plummet in cell viability at 1.4 M, whereas Na2SO4 induced only a 20 % permeability increase. Antioxidant enzyme profiling revealed a twofold surge in superoxide dismutase (SOD) activity under NaCl at 0.4 M, and a 1.5-fold rise in catalase (CAT) activity under Na2SO4. Furthermore, there was a significant correlation between Na+ concentration and cellular responses, particularly under Na2SO4 stress, where higher sodium tolerance was linked to enhanced melanin, reduced glutathione (GSH), and total glutathione (tGSH) levels. Our findings not only illuminate the nuanced response of Alternaria sp. 17463 to anionic stress but also underscore the fungus's potential as a bioindicator for salt stress. This research paves the way for developing targeted microbial interventions to bolster crop performance in saline environments, offering a significant step forward in precision agriculture.

Habitat distribution of the genus Belliella in continental waters and the description of Belliella alkalica sp. nov., Belliella calami sp. nov. and Belliella filtrata sp. nov

The genus Belliella belongs to the family Cyclobacteriaceae (order Cytophagales, phylum Bacteroidota) and harbours aerobic chemoheterotrophic bacteria. Members of this genus were isolated from various aquatic habitats, and our analysis based on global amplicon sequencing data revealed that their relative abundance can reach up to 5-10 % of the bacterioplankton in soda lakes and pans. Although a remarkable fraction of the most frequent genotypes that we identified from continental aquatic habitats is still uncultured, five new alkaliphilic Belliella strains were characterized in detail in this study, which were isolated from three different soda lakes and pans of the Carpathian Basin (Hungary). Cells of all strains were Gram-stain-negative, obligate aerobic, rod-shaped, non-motile and non-spore-forming. The isolates were oxidase- and catalase-positive, red-coloured, but did not contain flexirubin-type pigments; they formed bright red colonies that were circular, smooth and convex. Their major isoprenoid quinone was MK-7 and the predominant fatty acids were iso-C_15 : 0, iso-C_17 : 0 3-OH and summed feature 3 containing C_16 : 1  ω6c and/or C_16 : 1  ω7c. The polar lipid profiles contained phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid, and several unidentified lipids and aminolipids. Based on whole-genome sequences, the DNA G+C content was 37.0, 37.1 and 37.8 mol % for strains R4-6^T, DMA-N-10a^T and U6F3^T, respectively. The distinction of three new species was confirmed by in silico genomic comparison. Orthologous average nucleotide identity (<85.4 %) and digital DNA-DNA hybridization values (<38.9 %) supported phenotypic, chemotaxonomic and 16S rRNA gene sequence data and, therefore, the following three novel species are proposed: Belliella alkalica sp. nov. (represented by strains R4-6^T=DSM 111903^T=JCM 34281^T=UCCCB122^T and S4-10), Belliella calami sp. nov. (DMA-N-10a^T=DSM 107340^T=JCM 34280^T=UCCCB121^T) and Belliella filtrata sp. nov. (U6F3^T=DSM 111904^T=JCM 34282^T=UCCCB123^T and U6F1). Emended descriptions of species Belliella aquatica, Belliella baltica, Belliella buryatensis, Belliella kenyensis and Belliella pelovolcani are also presented.

Salinity and Heavy Metal Tolerance, and Phytoextraction Potential of Ranunculus sceleratus Plants from a Sandy Coastal Beach

The aim of the present study was to evaluate tolerance to salinity and different heavy metals as well as the phytoextraction potential of Ranunculus sceleratus plants from a brackish coastal sandy beach habitat. Four separate experiments were performed with R. sceleratus plants in controlled conditions: (1) the effect of NaCl gradient on growth and ion accumulation, (2) the effect of different Na⁺ and K⁺ salts on growth and ion accumulation, (3) heavy metal tolerance and metal accumulation potential, (4) the effect of different forms of Pb salts (nitrate and acetate) on plant growth and Pb accumulation. A negative effect of NaCl on plant biomass was evident at 0.5 g L^-1 Na⁺ and growth was inhibited by 44% at 10 g L^-1 Na⁺, and this was associated with changes in biomass allocation. The maximum Na⁺ accumulation (90.8 g kg^-1) was found in the stems of plants treated with 10 g kg^-1 Na⁺. The type of anion determined the salinity tolerance of R. sceleratus plants, as Na⁺ and K⁺ salts with an identical anion component had a comparable effect on plant growth: nitrates strongly stimulated plant growth, and chloride treatment resulted in slight but significant growth reduction, but plants treated with nitrites and carbonates died within 4 and 5 weeks after the full treatment, respectively. The shoot growth of R. sceleratus plants was relatively insensitive to treatment with Mn, Cd and Zn in the form of sulphate salts, but Pb nitrate increased it. Hyperaccumulation threshold concentration values in the leaves of R. sceleratus were reached for Cd, Pb and Zn. R. sceleratus can be characterized as a shoot accumulator of heavy metals and a hyperaccumulator of Na⁺. A relatively short life cycle together with a high biomass accumulation rate makes R. sceleratus useful for dynamic constructed wetland systems aiming for the purification of concentrated wastewaters.