The High Arctic deserts of remote northern Greenland are expected to become warmer and wetter due to climate change. Precipitation changes will increase fluctuations in surface soil salinity, and the same happens for thawed permafrost soil where stable salt concentrations are replaced with fluctuating salinity during annual freeze-thaw cycles. Both have unknown effects on the microbial communities and their emissions of microbial volatile organic compounds (MVOCs). These compounds are produced from various pathways mainly as secondary metabolites and have ecological and climatic implications when released into the environment and the atmosphere. Thus, it is important to explore the effects of environmental changes, such as changes in salinity, on soil microbial communities and their MVOC emissions. Here, we characterize the MVOC production of three novel bacterial isolates from northern Greenland throughout their growth period under low, moderate, and high salt concentrations. We demonstrate that salinity significantly alters both the quantity and composition of MVOCs emitted by all three strains, including changes in the emissions of sulphur- and nitrogen-containing compounds, potentially leading to ecosystem nutrient loss. The observed changes in MVOC profiles suggest that changes in soil salinity due to climate change could alter microbial metabolism and MVOC emissions, with potential implications for Arctic nutrient cycling and atmospheric chemistry. Novel Arctic bacterial isolates were found to produce diverse microbial volatile organic compounds, including sulphur- and nitrogen-containing gases, with emissions strongly shaped by changing soil salinity

A polyphasic taxonomic approach was conducted to characterize the bacterial strain B22T isolated from the rhizospheric soil of the halophyte Salicornia hispanica. This strain is aerobic, Gram-negative, rod-shaped, catalase and oxidase positive, motile, reduces nitrates and chemoheterotrophic. It is halotolerant, exhibiting optimal growth at 28 degrees C and pH 7.0 in the presence of 0.5-2.5% (w/v) of NaCl. The B22T genome size is 5.7 Mbp, with a G+C content of 60.5 mol%. This strain has the capacity to promote tomato growth by producing siderophores, indole-3-acetic acid and enzymes such as phytase and acid phosphatase. Additionally, strain B22T produces a quorum quenching (QQ) enzyme capable of degrading synthetic N-acylhomoserine lactones (AHLs) as well as those produced by phytopathogens. The interference of plant pathogen communication reduced virulence in tomato fruits and plants. Phylogenetic analysis revealed that the closest relatives of strain B22T was Pseudomonas tehranensis SWRI 196T. The average nucleotide identity values between strain B22T and P. tehranensis SWRI 196T was 95.1% while digital DNA-DNA hybridization values was 64.5% The main cellular fatty acids of strain B22T were C16:0, summed feature 3 (C16:1 omega 7c/C16:1 omega 6c) and summed feature 8 (C18:1 omega 7c/C18:1 omega 6c). The major polar lipids identified were diphosphatidylglycerol and phosphatidylethanolamine, while the predominant respiratory quinone was ubiquinone (Q-9). Based on genomic, phylogenetic and chemotaxonomic data, strain B22T (=CECT 31209; =LMG33902) represents a novel species within the genus Pseudomonas. The name Pseudomonas halotolerans sp. nov. is proposed. Additionally, this study highlights the potential of P. halotolerans as a sustainable biocontrol agent due to its plant growth-promoting activity in tomato plants and its ability to reduce phytopathogen virulence factors, mitigating damage to fruits and plants.

In recent years, there has been increasing interest in the study of extremophilic microorganisms, which include halophiles and halotolerants. These microorganisms, able to survive and thrive optimally in a wide range of environmental extremes, are polyextremophiles. In this context, one of the main reasons for studying them is to understand their adaptative mechanisms to stress caused by extreme living conditions. In this paper, a fungal strain Penicillium chrysogenum P13, isolated from saline soils around Pomorie Lake, Bulgaria, was used. The effect of elevated concentrations of sodium chloride on the growth and morphology as well as on the physiology of the model strain was investigated. P. chrysogenum P13 demonstrated high tolerance to NaCl, showing remarkable growth in liquid and agar media. In order to establish the relationship between salt- and oxidative stress, changes in the cell biomarkers of oxidative stress, such as oxidatively damaged proteins, lipid peroxidation, and levels of reserve carbohydrates of the studied strain were evaluated. The involvement of antioxidant enzyme defense in the adaptive strategy of the halotolerant strain against elevated NaCl concentrations was investigated.

Salinized soil is an important reserved arable land resource in China. The management and utilization of salinized soil can safeguard the current size of arable land and a stable grain yield. Salt accumulation will lead to the deterioration of soil properties, destroy soil production potential and damage soil ecological functions, which in turn will threaten global water and soil resources and food security, and affect sustainable socio-economic development. Microorganisms are important components of salinized soil. Microbial remediation is an important research tool in improving salinized soil and is key to realizing sustainable development of agriculture and the ecosystem. Knowledge about the impact of salinization on soil properties and measures using microorganisms in remediation of salinized soil has grown over time. However, the mechanisms governing these impacts and the ecological principles for microbial remediation are scarce. Thus, it is imperative to summarize the effects of salinization on soil physical, chemical, and microbial properties, and then review the related mechanisms of halophilic and halotolerant microorganisms in salinized soil remediation via direct and indirect pathways. The stability, persistence, and safety of the microbial remediation effect is also highlighted in this review to further promote the application of microbial remediation in salinized soil. The objective of this review is to provide reference and theoretical support for the improvement and utilization of salinized soil.

High soil salinity has an unfavorable consequence on the growth and productivity of rice crop. However, some salt-tolerant plant growth-promoting bacteria (ST-PGPB) regulate specific physiological, biochemical, and molecular properties to promote crop growth while minimizing the detrimental effects of salt stress. In this regard, we isolated ST-PGPB from rhizospheric soil and examined it to mitigate the salinity stress in rice seedlings. The growth of the bacterium at 3 M NaCl demonstrated its halotolerance, and 16S rRNA sequencing identified it as Bacillus siamensis, and the isolated strain was named BW. Further study indicated that biopriming with BW strain helps plant growth promotion-related phenotype and significantly mitigates salinity stress in rice seedlings. Treatment of rice seeds with BW resulted in significantly improved germination of seedlings at 75 mM to 150 mM NaCl, along with better physiology and biochemical parameters than the untreated ones. Furthermore, Bacillus sp. BW efficiently colonizes rice roots and produces auxin and siderophore, via forming biofilm under different salt concentrations. Under 100-200 mM NaCl treatment conditions, the extracellular metabolite profile from BW showed a substantial abundance in specific metabolites, such as osmoprotective chemicals, suggesting the likely protective mechanism against salinity stress damage. This study demonstrates the role and potential of a halotolerant- BW strain in supporting the growth of rice plants under salinity conditions.

The increasing salinization of soils and resulting degradation of irrigated lands have directly affected 2.6 billion hectares of dryland agriculture worldwide. This phenomenon has led to significant qualitative and quantitative losses in crop production. The absorption and accumulation of ions adversely affect plants by disrupting photosynthetic machinery, damaging tissues, disturbing the ionic balance of cells, and inducing oxidative stress. Rhizobacteria-induced salinity tolerance is a promising tool in crop plants that works by modulating the plant metabolism. Among rhizobacteria, halotolerant plant growth promoting rhizobacteria (PGPR) stand out as particularly significant because they can extend salinity tolerance in crop plants through various mechanisms, including secondary metabolite production, osmolyte accumulation, and modulation of plant metabolism via certain localized and systemic defense functions. Furthermore, the volatile organic compounds produced by PGPR play a vital role in salinity amelioration by regulating root ions uptake, promoting osmolyte related genes expression, reducing the level of oxidative stress markers such as electrolyte leakage, and maintaining endogenous hormonal levels. These novel salt-ameliorating mechanisms and their ability to improve plant fitness and enhance tolerance to salinized soils highlight halotolerant PGPR as eco-friendly and cost-effective tools for salt stress tolerance. This review focuses on elucidating the novel mechanisms used by halotolerant PGPR, their production of secondary metabolites under salinity stress, their application as bioinoculants for crop plants in salinized soils and the development of novel bioformulations for the bioremediation of agricultural soils facing salt stress-related challenges.