Effect of salinity on biological nitrogen removal from wastewater and its mechanism.

The nitrogen discharge from saline wastewater will cause significant pollution to the environment. As a high-efficiency and low-cost treatment method, biological treatment has a promising application prospect in the removal of nitrogen from high-salt wastewater. However, the inhibitory effect of high salt on microorganisms increases the difficulty of its treatment. This review discusses the influence of salinity on the nitrogen removal process, considering both traditional and novel biological techniques. Common methods to enhance the effectiveness of biological nitrogen removal processes and their mechanisms of action in engineering practice and research, including sludge acclimation and inoculation of halophilic bacteria, are also introduced. An outlook on the future development of biological nitrogen removal processes for high-salt wastewater is provided to achieve environmentally friendly discharge of high-salt wastewater.

Bacterial diversity and chemical ecology of natural product-producing bacteria from Great Salt Lake sediment.

Great Salt Lake (GSL), located northwest of Salt Lake City, UT, is the largest terminal lake in the USA. While the average salinity of seawater is ~3.3%, the salinity in GSL ranges between 5% and 28%. In addition to being a hypersaline environment, GSL also contains toxic concentrations of heavy metals, such as arsenic, mercury, and lead. The extreme environment of GSL makes it an intriguing subject of study, both for its unique microbiome and its potential to harbor novel natural product-producing bacteria, which could be used as resources for the discovery of biologically active compounds. Though work has been done to survey and catalog bacteria found in GSL, the Lake's microbiome is largely unexplored, and little to no work has been done to characterize the natural product potential of GSL microbes. Here, we investigate the bacterial diversity of two important regions within GSL, describe the first genomic characterization of Actinomycetota isolated from GSL sediment, including the identification of two new Actinomycetota species, and provide the first survey of the natural product potential of GSL bacteria.

Bioremediation of oily hypersaline soil via autochthonous bioaugmentation with halophilic bacteria and archaea.

Kuwaiti hypersaline soil samples were contaminated with 5 % (w/w) weathered Kuwaiti light crude oil and bioaugmented with autochthonous halophilic hydrocarbonoclastic archaeal and bacterial strains, two each, individually and as consortia. Residual oil contents were determined, and microbial communities were analyzed by culture-dependent and culture-independent approaches initially and seasonally for one year. After one year of the bioremediation process, the mean oil degradation rate was similar across all treated soils including the controlled unbioaugmented one. Oil hydrocarbons were drastically reduced in all soil samples with values ranging from 82.7 % to 93 %. During the bioremediation process, the number of culturable oil-degrading bacteria increased to a range of 142 to 344 CFUx104 g-1 after 12 months of bioaugmentation. Although culture-independent analysis showed a high proportion of inoculants initially, none could be cultured throughout the bioremediation procedure. Within a year, microbial communities changed continually, and 33 species of halotolerant/halophilic hydrocarbonoclastic bacteria were isolated and identified belonged mainly to the three major bacterial phyla Actinobacteria, Proteobacteria, and Firmicutes. The archaeal phylum Halobacterota represented <1 % of the microbial community's relative abundance, which explains why none of its members were cultured. Improving the biodegradability of an already balanced environment by autochthonous bioaugmentation is more involved than just adding the proper oil degraders. This study emphasizes the possibility of a relatively large resistant population, a greater diversity of oil-degrading microorganisms, and the highly selective impacts of oil contamination on hypersaline soil bacterial communities.

Exploring Andean High-Altitude Lake Extremophiles through Advanced Proteotyping.

Quickly identifying and characterizing isolates from extreme environments is currently challenging while very important to explore the Earth's biodiversity. As these isolates may, in principle, be distantly related to known species, techniques are needed to reliably identify the branch of life to which they belong. Proteotyping these environmental isolates by tandem mass spectrometry offers a rapid and cost-effective option for their identification using their peptide profiles. In this study, we document the first high-throughput proteotyping approach for environmental extremophilic and halophilic isolates. Microorganisms were isolated from samples originating from high-altitude Andean lakes (3700-4300 m a.s.l.) in the Chilean Altiplano, which represent environments on Earth that resemble conditions on other planets. A total of 66 microorganisms were cultivated and identified by proteotyping and 16S rRNA gene amplicon sequencing. Both the approaches revealed the same genus identification for all isolates except for three isolates possibly representing not yet taxonomically characterized organisms based on their peptidomes. Proteotyping was able to indicate the presence of two potentially new genera from the families of Paracoccaceae and Chromatiaceae/Alteromonadaceae, which have been overlooked by 16S rRNA amplicon sequencing approach only. The paper highlights that proteotyping has the potential to discover undescribed microorganisms from extreme environments.

Microbes of biotechnological importance in acidic saline lakes in the Yilgarn Craton, Western Australia.

Acidic salt lakes are environments that harbor an array of biologically challenging conditions. Through 16S rRNA, 18S rRNA, and ITS amplicon sequencing of eight such lakes across the Yilgarn Craton of Western Australia, we aim to understand the microbial ecology of these lakes with a focus on iron- and sulfur-oxidizing and reducing microorganisms that have theoretical application in biomining industries. In spite of the biological challenges to life in these lakes, the microbial communities were highly diverse. Redundancy analysis of soil samples revealed sulfur, ammonium, organic carbon, and potassium were significant diversities of the microbial community composition. The most abundant microbes with a hypothetical application in biomining include the genus 9 M32 of the Acidithiobacillus family, Alicyclobacillus and Acidiphilium, all of which are possible iron- and/or sulfur-oxidizing bacteria. It is evident through this study that these lakes harbor multiple organisms with potential in biomining industries that should be exploited and studied further.

Assessing the metabolism, phylogenomic, and taxonomic classification of the halophilic genus Halarchaeum.

In this study, a genomic approach was employed to evaluate the metabolic potentials and taxonomic classification of the halophilic genus Halarchaeum. Genomic analysis revealed that Halarchaeum members exhibit a predilection for amino acids as their primary energy source in high-salinity environments over carbohydrates. Genome analysis unveiled the presence of crucial genes associated with metabolic pathways, including the Embden-Meyerhof pathway, semi-phosphorylative Entner-Doudoroff pathway, and the urea cycle. Furthermore, the genomic analysis indicated that Halarchaeum members employ diverse mechanisms for osmotic regulation (encompassing both salt-in and salt-out strategies). Halarchaeum members also encode genes to alleviate acid and heat stress. The average nucleotide identity value between Halarchaeum solikamskense and Halarchaeum nitratireducens exceeded the established threshold (95%-96%) for defining distinct species. This high similarity suggests a close relationship between these two species, prompting the proposal to reclassify Halarchaeum solikamskense as a heterotypic synonym of Halarchaeum nitratireducens. The results of this study contribute to our knowledge of taxonomic classification and shed light on the adaptive strategies employed by Halarchaeum species in their specific ecological niches.

Draft genome sequence of Halomonas sp. SSL-5, a halophilic Mn(II)-oxidizing, perchlorate-tolerant bacterium.

Halomonas sp. SSL-5 is a Mn(II)-oxidizing, perchlorate-tolerant halophilic bacterium isolated from an Australian hypersaline lake. The genome sequence contains 27 contigs, and the genome is 3.4 Mb with a GC content of 67.2%. The sequence provides information for future studies of Mn(II) oxidation and perchlorate resistance under halophilic conditions.

Draft genome sequence of Halobacillus campisalis strain ASL-17.

We report here the genome sequence of moderately halophilic Halobacillus campisalis ASL-17, isolated from hypersaline sediment from the Yellow Sea, Korea. The bacterium was Gram variable, oval or coccoid, and mesophilic. The genome of H. campisalis ASL-17 has 3.8 Mbp, with 3,910 coding sequences, 76 RNAs, and 41.3% G + C content.

Improved production of alkaline and solvent-stable proteases from a halotolerant Exiguobacterium isolate through heterologous expression.

Halophiles are excellent sources of detergent proteases that are attributed to stability in alkaline pH, salts, surfactants, and hydrophobic solvents. The lower enzymatic yields and tedious downstream processes necessitate the search for newer halophilic sources. We have previously reported a halotolerant Exiguobacterium sp. TBG-PICH-001, which secretes solvent-tolerant alkaline protease/s. The present study describes the heterologous expression of two protease genes, namely, rsep metalloprotease (WP_195864791, 1.23 Kb) and tpa serine protease (WP_195864453, 0.879 Kb) genes. These were cloned into the pET 22b + plasmid vector and expressed in Escherichia coli BL21(DE3). The recombinant proteases rsep and tpa showed respective yields of 6.3 and 6.7 IU/mg, 11 and 12-fold higher than the crude native protease/s from TBG-PICH-001. These showed soluble expression at 46 and 32 KDa, respectively. These were purified to homogeneity through Ni-NTA-affinity chromatography. The purified proteases were characterized for properties like pH & temperature optima and stability, substrate specificity, kinetic parameters, and detergent attributes. They showed affinity towards various substrates with a respective Km of 392 and 301 µM towards casein. The recombinant proteases exhibited stability in the alkaline pH (7-10), surfactants, metal ions, detergents, and hydrophobic solvents, rendering their suitability as detergent additives.

Microbial diversity in polyextreme salt flats and their potential applications.

Recent geological, hydrochemical, and mineralogical studies performed on hypersaline salt flats have given insights into similar geo-morphologic features on Mars. These salt-encrusted depressions are widely spread across the Earth, where they are characterized by high salt concentrations, intense UV radiation, high evaporation, and low precipitation. Their surfaces are completely dry in summer; intermittent flooding occurs in winter turning them into transitory hypersaline lakes. Thanks to new approaches such as culture-dependent, culture-independent, and metagenomic-based methods, it is important to study microbial life under polyextreme conditions and understand what lives in these dynamic ecosystems and how they function. Regarding these particular features, new halophilic microorganisms have been isolated from some salt flats and identified as excellent producers of primary and secondary metabolites and granules such as halocins, enzymes, carotenoids, polyhydroxyalkanoates, and exopolysaccharides. Additionally, halophilic microorganisms are implemented in heavy metal bioremediation and hypersaline wastewater treatment. As a result, there is a growing interest in the distribution of halophilic microorganisms around the world that can be looked upon as good models to develop sustainable biotechnological processes for all fields. This review provides insights into diversity, ecology, metabolism, and genomics of halophiles in hypersaline salt flats worldwide as well as their potential uses in biotechnology.

Recent advances in production and applications of ectoine, a compatible solute of industrial relevance.

Extremophilic bacteria growing in saline ecosystems are potential producers of biotechnologically important products including compatible solutes. Ectoine/hydroxyectoine are two such solutes that protect cells and associated macromolecules from osmotic, heat, cold and UV stress without interfering with cellular functions. Since ectoine is a high value product, overviewing strategies for improving yields become relevant. Screening of natural isolates, use of inexpensive substrates and response surface methodology approaches have been used to improve bioprocess parameters. In addition, genome mining exercises can aid in identifying hitherto unreported microorganisms with a potential to produce ectoine that can be exploited in the future. Application wise, ectoine has various biotechnological (protein protectant, membrane modulator, DNA protectant, cryoprotective agent, wastewater treatment) and biomedical (dermatoprotectant and in overcoming respiratory and hypersensitivity diseases) uses. The review summarizes current updates on the potential of microorganisms in the production of this industrially relevant metabolite and its varied applications.

Mutualistic symbiosis of fungi and nitrogen-fixing bacteria in halophilic aerobic granular sludge treating nitrogen-deficient hypersaline organic wastewater.

Hypersaline organic wastewater is characterized as being nitrogen-deficient, and is easily prone to sludge bulking. In this study, the stability of halophilic aerobic granular sludge (HAGS) for the treatment of hypersaline organic wastewater is explored. Along with the decrease of influent ammonium, the bacterial population substantially reduced, whereas the fungal population continuously increased in HAGS. Saccharomycetales in fungi become the dominant sequence (99.78%) in HAGS bulking. Additionally, Halanaerobium (77.47%) remained prevalent in HAGS despite bacterial washout. Halanaerobium, a nitrogen-fixing genus of bacteria, provided nitrogen for ammonium-assimilating fungi. Saccharomycetales encapsulating HAGS reduced the transfer efficiency of dissolved oxygen, thereby creating favorable growth conditions for Halanaerobium. This paper for the first time highlights the mutualistic symbiosis of fungi and bacteria in HAGS treating the hypersaline organic wastewater. The study lays the foundation for the control and recovery of HAGS bulking.

Enhancing poly(3-hydroxybutyrate) production in halophilic bacteria through improved salt tolerance.

Polyhydroxyalkanoates (PHA) have emerged as a promising bio-compound in the industrial application due to their potential to replace conventional petroleum-based plastics with sustainable bioplastics. This study focuses on Halomonas sp. YJPS3-3, a halophilic bacterium, and presents a novel approach to enhance PHA production by exploiting its salt tolerance toward PHA biosynthesis. Through gamma irradiation-induced mutants with enhanced salt tolerance from 15% NaCl to 20% NaCl, mutant halo6 showing a significant 11% increase in PHA yield, was achieved. Moreover, the mutants displayed not only higher PHA content but also remarkable cell morphology with elongation. In addition, this research unravels the genetic determinants behind the elevated PHA content and identifies a corresponding shift in fatty acid composition favoring PHA accumulation. This novel mutant obtained from gamma irradiation with enhanced salt tolerance in halophilic bacteria opens up new avenues not only for the bioplastic industry but also for applications in the production of high-value metabolites.

A long-awaited taxogenomic investigation of the family Halomonadaceae.

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

Halo-alkaliphilic microbes as an effective tool for heavy metal pollution abatement and resource recovery: challenges and future prospects.

The current study presents an overview of heavy metals bioremediation from halo-alkaline conditions by using extremophilic microorganisms. Heavy metal remediation from the extreme environment with high pH and elevated salt concentration is a challenge as mesophilic microorganisms are unable to thrive under these polyextremophilic conditions. Thus, for effective bioremediation of extreme systems, specialized microbes (extremophiles) are projected as potential bioremediating agents, that not only thrive under such extreme conditions but are also capable of remediating heavy metals from these environments. The physiological versatility of extremophiles especially halophiles and alkaliphiles and their enzymes (extremozymes) could conveniently be harnessed to remediate and detoxify heavy metals from the high alkaline saline environment. Bibliometric analysis has shown that research in this direction has found pace in recent years and thus this review is a timely attempt to highlight the importance of halo-alkaliphiles for effective contaminant removal in extreme conditions. Also, this review systematically presents insights on adaptive measures utilized by extremophiles to cope with harsh environments and outlines the role of extremophilic microbes in industrial wastewater treatment and recovery of metals from waste with relevant examples. Further, the major challenges and way forward for the effective applicability of halo-alkaliphilic microbes in heavy metals bioremediation from extremophilic conditions are also highlighted.

Reduction in Salt Stress Due to the Action of Halophilic Bacteria That Promote Plant Growth in Solanum lycopersicum.

Soil salinity is one of the most important factors reducing agricultural productivity worldwide. Halophilic plant growth-promoting bacteria (H-PGPB) represent an alternative method of alleviating saline stress in crops of agricultural interest. In this study, the following halophilic bacteria were evaluated: Bacillus sp. SVHM1.1, Halomonas sp. SVCN6, Halomonas sp. SVHM8, and a consortium. They were grown under greenhouse conditions in Solanum lycopersicum at different salinity concentrations in irrigation water (0, 20, 60, and 100 mM NaCl) to determine the effects on germination, fruit quality, yield, and concentration of osmoprotectors in plant tissue. Our results demonstrate the influence of halophilic bacteria with the capacity to promote plant growth on the germination and development of Solanum lycopersicum at higher salinity levels. The germination percentage was improved at the highest concentration by the inoculated treatments (from 37 to 47%), as were the length of the radicle (30% at 20 mM) and plumule of the germinated seed, this bacterium also increased the weight of the plumule (97% at 100 mM). They also improved the yield. The dry weight of the plant, in addition to having an influence on the quality of the fruit and the concentration of osmoprotectors (Bacillus sp. SVHM 1.1) had the greatest effect on fruit yield (1.5 kg/plant at 20 mM), by the otherhand, Halomonas sp. SVHM8 provided the best fruit quality characteristics at 100 mM. According to the above results, the efficiency of halophilic PGPB in the attenuation of salt stress in Solanum lycopersicum has been proven.

Antimicrobial potential of secondary metabolites and DNA gyrase B blocking molecules produced by a halophilic bacterium Virgibacillus salarius (MML1918).

AIM: The present study aims to determine the antimicrobial potential of Virgibacillus salairus (MML1918) against human pathogens and its in-vitro and in-silico properties. METHODS AND RESULTS: In this present study, totally 63 halophilic bacterial cultures were obtained and cultivated in nutrient broth medium containing 8% NaCl and the metabolites, were extracted using ethyl acetate and screened for their antimicrobial property by cell viability assay against 12 pathogenic bacteria and fungi, among 63 halophilic bacteria the Vir. salaries (MML1918) found to be the best producer for secondary metabolites production against clinical pathogens. The optimization of growth for important physiochemical parameters was characterized and applied for different production media and based on its highest activity as 17.5 ± .07 mm zone of inhibition (ZOI) for Bacillus cereus followed by 17.5 ± 00 mm ZOI for Staphylococcus aureus, the production medium ATCC1097 was chosen for mass production. The mass production of secondary metabolites from Vir. salaries MML1918 was carried out in a fermenter under controlled conditions and crude metabolites was extracted and condensed. The antimicrobial activity of crude metabolites showed B. cereus (19.3 ± 0.5 mm ZOI), Staph. aureus, and Candida albicans (18.3 ± 0.5 mm ZOI) as the highest ZOI in production media for halophilic bacteria ATCC1097. Further, the gas chromatography-mass spectrometry analysis showed 24 compounds present in crude metabolites. Among the 24 compounds, four molecules were found to be important based on molecule percentage in crude and structural similarity. The molecular docking studies show that the selected four molecules effectively bind with the active region DNA gyrase B. CONCLUSION: Virgibacillus salarius (MML1918) effectively showed antimicrobial activity against several pathogenic organisms and can be employed as a suitable candidate for producing novel antimicrobial agents.

Aromatic compounds depurative and plant growth promotion rhizobacteria abilities of Allenrolfea vaginata (Amaranthaceae) rhizosphere microbial communities from a solar saltern hypersaline soil.

Introduction: This work investigates whether rhizosphere microorganisms that colonize halophyte plants thriving in saline habitats can tolerate salinity and provide beneficial effects to their hosts, protecting them from environmental stresses, such as aromatic compound (AC) pollution. Methods: To address this question, we conducted a series of experiments. First, we evaluated the effects of phenol, tyrosine, 4-hydroxybenzoic acid, and 2,4-dichlorophenoxyacetic (2,4-D) acids on the soil rhizosphere microbial community associated with the halophyte Allenrolfea vaginata. We then determined the ability of bacterial isolates from these microbial communities to utilize these ACs as carbon sources. Finally, we assessed their ability to promote plant growth under saline conditions. Results: Our study revealed that each AC had a different impact on the structure and alpha and beta diversity of the halophyte bacterial (but not archaeal) communities. Notably, 2,4-D and phenol, to a lesser degree, had the most substantial decreasing effects. The removal of ACs by the rhizosphere community varied from 15% (2,4-D) to 100% (the other three ACs), depending on the concentration. Halomonas isolates were the most abundant and diverse strains capable of degrading the ACs, with strains of Marinobacter, Alkalihalobacillus, Thalassobacillus, Oceanobacillus, and the archaea Haladaptatus also exhibiting catabolic properties. Moreover, our study found that halophile strains Halomonas sp. LV-8T and Marinobacter sp. LV-48T enhanced the growth and protection of Arabidopsis thaliana plants by 30% to 55% under salt-stress conditions. Discussion: These results suggest that moderate halophile microbial communities may protect halophytes from salinity and potential adverse effects of aromatic compounds through depurative processes.

Phylogeny and functional diversity of halophilic microbial communities from a thalasso environment.

The El-Rawda solar saltern, located in North Sinai, Egypt, is formed through the process of water evaporation from the Bradawil lagoon. This evaporation leads to the precipitation of gypsum, halite minerals, and salt flats, which subsequently cover the southern and eastern areas of the lagoon. This study employed the shotgun metagenomic approach, the illumine platform, and bioinformatic tools to investigate the taxonomic composition and functional diversity of halophilic microbial communities in solar saltern. The metagenomic reads obtained from the brine sample exhibited a greater count compared to those from the sediment sample. Notably, the brine sample was primarily characterized by an abundance of archaea, while the sediment sample displayed a dominant abundance of bacteria. Both samples exhibited a relatively low abundance of eukaryotes, while viruses were only found in the brine sample. Furthermore, the comparative analysis of functional pathways showed many important processes related to central metabolism and protein processing in brine and sediment samples. In brief, this research makes a valuable contribution to the understanding of very halophilic ecosystems in Egypt, providing insights into their microbial biodiversity and functional processes.

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.