Solar Saltern Research Articles

Plant-growth promotion by halotolerant black yeast Hortaea sp. strain PMGTC8 associated with salt crystals from solar saltern of Goa, India.

Plant-growth-promoting microbes are sustainable alternative to improve the soil fertility and plant-growth facilitating the nutrients uptake in normal and stressed environmental conditions. Among these, halotolerant and halophilic microorganisms with plant- growth-promoting ability are better candidates that could be exploited as bioinoculants in salinity affected agriculture soils. Considering this, the current study aimed to isolate, characterize and determine the plant-growth-promoting potential of the culturable halotolerant black yeast associated with salt crystals from the solar saltern of Goa, India. The results revealed 1.3 × 104CFU/g of viable number of colonies on 25% NaCl Tryptone Yeast Extract (NTYE) agar after 30-45days incubation. Among ten morphologically distinct isolates, a black pigmented strain PMGTC8 was characterized as yeast-like and appeared two celled with average size of 4.30 ± 0.14µm under scanning electron micrograph. Based on phylogenetic analysis using internal transcribed spacer (ITS) marker, the isolate showed maximum similarity to genus Hortaea. Interestingly, Hortaea sp. strain PMGTC8 (OR527117) exhibited plant-growth-promoting characteristics and caused significantly (p < 0.01) higher germination rate (93.33%), vigor index (964.22), shoot (3.95cm) and root length (6.38cm), and fresh weight (0.039g) of Oryza sativa var. Korgut. This halotolerant black yeast may play a role in nutrition of the plants growing in saline soils. Conclusively, the current findings report for the first time the plant-growth-promoting potential of Hortaea sp. strain PMGTC8 associated with salt crystals of solar saltern, Goa, India for its possible use as bio-fertilizers in saline agriculture soils.

Impact of dilution on stochastically driven methanogenic microbial communities of hypersaline anoxic sediments.

Sediments underlying the solar salterns of S'Avall are anoxic hypersaline ecosystems dominated by anaerobic prokaryotes, and with the especial relevance of putative methanogenic archaea. Slurries from salt-saturated sediments, diluted in a gradient of salinity and incubated for > 4 years revealed that salt concentration was the major selection force that deterministically structured microbial communities. The dominant archaea in the original communities showed a decrease in alpha diversity with dilution accompanied by the increase of bacterial alpha diversity, being highest at 5% salts. Correspondingly, methanogens decreased and in turn sulfate reducers increased with decreasing salt concentrations. Methanogens especially dominated at 25%. Different concentrations of litter of Posidonia oceanica seagrass added as a carbon substrate, did not promote any clear relevant effect. However, the addition of ampicillin as selection pressure exerted important effects on the assemblage probably due to the removal of competitors or enhancers. The amended antibiotic enhanced methanogenesis in the concentrations ≤ 15% of salts, whereas it was depleted at salinities ≥ 20% revealing key roles of ampicillin-sensitive bacteria.

Simultaneous conversion of chromium and malachite green coexists in halophilic bacterium Halomonas xianhensis SUR308 isolated from a solar saltern.

Many industries are known to use heavy metals like chromium (Cr) to fix dyes in the fabrication processes and malachite green (MG) as colorant. Alkalinity, elevated temperature, or salinity of the industrial effluents makes conventional physicochemical removal of MG and hexavalent chromium [Cr(VI)] more difficult to apply and demands to perceive potential cost-effective and environment-friendly treatment methods to eliminate or convert them into less toxic compounds. Here, we report simultaneous removal and bioconversion of MG and Cr(VI) by a halophilic biofilm-forming bacterium Halomonas xianhensis SUR308. It can efficiently produce exopolysaccharides as extracellular polymeric substances (EPS) and form biofilm under oxygen limiting condition. The reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] is about 100%, and 95% after 84 h of growth in shaken and stagnant culture, respectively. The strain completely decolorizes MG after 48 h of growth in shaken culture. Furthermore, we found that strain SUR308 can efficiently detoxify chromium by reduction and degrades MG via producing various intermediate products simultaneously. Most interestingly, such conversions can also take place in alkaline environment and in environment where substantial amount of salt is present. These unique features of strain SUR308 make it suitable for the simultaneous remediation of toxic heavy metals and hazardous dye even from the environment having higher pH and salinity. The detail molecular mechanism of the bioconversion with its application in open environment would be the future research focus for bioprospecting strain SUR308.

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

IntroductionThis 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.MethodsTo 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 halophyteAllenrolfea 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.ResultsOur 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.Halomonasisolates were the most abundant and diverse strains capable of degrading the ACs, with strains ofMarinobacter,Alkalihalobacillus,Thalassobacillus,Oceanobacillus, and the archaeaHaladaptatusalso exhibiting catabolic properties. Moreover, our study found that halophile strains Halomonas sp. LV-8T andMarinobactersp. LV-48T enhanced the growth and protection ofArabidopsis thalianaplants by 30% to 55% under salt-stress conditions.DiscussionThese 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.

Psychromarinibacter sediminicola sp. nov., a novel moderately halophilic, metabolically diverse bacterium isolated from a solar saltern sediment, and comparison between members of family Roseobacteraceae.

Known for its species abundance and evolutionary status complexity, family Roseobacteraceae is an important subject of many studies on the discovery, identification, taxonomic status, and ecological properties of marine bacteria. This study compared and analyzed the phylogenetic, genomic, biochemical, and chemo taxonomical properties of seven species from three genera (Psychromarinibacter, Lutimaribacter, and Maritimibacter) of the family Roseobacteraceae. Moreover, a novel strain, named C21-152T was isolated from solar saltern sediment in Weihai, China. The values of 16S rRNA gene sequence similarity, the average nucleotide identity (ANI), the average amino acid identity (AAI), and the digital DNA-DNA hybridization (dDDH) between genomes of the novel strain and Psychromarinibacter halotolerans MCCC 1K03203T were 97.19, 78.49, 73.45, and 21.90%, respectively. Genome sequencing of strain C21-152T revealed a complete Sox enzyme system related to thiosulfate oxidization as well as a complete pathway for the final conversion of hydroxyproline to α-ketoglutarate. In addition, strain C21-152T was resistant to many antibiotics and had the ability to survive below 13% salinity. This strain had versatile survival strategies in saline environments including salt-in, compatible solute production and compatible solute transport. Some of its physiological features enriched and complemented the knowledge of the characteristics of the genus Psychromarinibacter. Optimum growth of strain C21-152T occurred at 37℃, with 5-6% (w/v) NaCl and at pH 7.5. According to the results of the phenotypic, chemotaxonomic characterization, phylogenetic properties and genome analysis, strain C21-152T should represent a novel specie of the genus Psychromarinibacter, for which the name Psychromarinibacter sediminicola sp. nov. is proposed. The type strain is C21-152T (= MCCC 1H00808T = KCTC 92746T = SDUM1063002T).

In vitro and molecular docking studies on a novel Brevibacillus borstelensis NOB3 bioactive compounds as anticancer, anti-inflammatory, and antimicrobial activity

ABSTRACT Cancerous tumor growth and inflammation stimulate the search for novel anticancer drugs. This pioneering study isolated Brevibacillus borstelensis NOB3 from a solar saltern and tested its bioactive substances for anticancer, antimicrobial, and anti-inflammatory activity. An in-silico test against HeLa cells was followed by an in-vitro MTT test. Agar well diffusion was used to examine the activity of the bioactive compounds of B. borstelensis NOB3 against spectrum human pathogenic bacteria and fungi. The highest clear zone was found with Bacillus subtilis (30 mm), followed by Escherichia coli and Candida albicans (28 mm); Pseudomonas aeruginosa and Staphylococcus aureus had a smaller zone of inhibition (25 mm). The minimum inhibitory concentration (MIC), was 31.25 g/ml against E. coli, followed by 62.5 g/ml against B. subtilis, P. aeruginosa, and C. albicans. Twenty-two bioactive substances were identified by (GC-MS). The binding energy of pyrazine, n-hexadecenoic acid, and oleic acid was measured for the cervical cancer target protein, and the findings were ‒5.1 kcal/mol, ‒4.6 kcal/mol, and ‒4.7 kcal/mol, respectively. In-vitro tests revealed potential action against the HeLa cell line with a half-maximal inhibitory concentration (IC50) of 68.46 g/ml. The novel halophilic B. borstelensis NOB3 has the potential to produce bioactive compounds for drug development.

Insights into saline adaptation strategies through a novel halophilic bacterium isolated from solar saltern of Yellow sea

Solar salterns were placed along the coast and were frequently left unattended after use. While many studies have isolated and identified microorganisms from hypersaline environments, their role and adaptation mechanisms are still unclear. Herein, we elucidated the role of halophiles in salt-polluted areas through the recently reported Halomonas getboli YJPS3-2 from the abandoned saltern. We analyzed the expression levels of genes in the YJPS3-2 strain to identify its adaptation mechanisms to high salinity environments, by representing the process from tidal flats to abandoned salterns with varying salinity gradients. The YJPS3-2 strain primarily overexpresses genes associated with ABC transport to adapt to hypersaline environments. Interestingly, the cheA gene, which recognizes changes in the surrounding, was the most upregulated, and it was also associated with the overexpression of the MS ring and T3SS mechanisms relating to the flagellar activity. The YJPS3-2 recognized the high salt concentration in its surroundings and attempted to accumulate compatible solutes that could withstand high osmotic pressure inside the cell to adapt to the high salinity environment. Furthermore, during this process, the YJPS3-2 strain removed surrounding pollutants and secreted secondary metabolites that could be utilized by neighboring organisms. Our results suggested that this halophilic bacterium has the potential to serve as a pioneering species for thriving the surrounding while adapting to saline environments.

Taxonomic Profiling of Microorganisms Inhabiting Two Solar Salterns that Produce High- and Low-Quality Salts

The contribution of halophilic microorganisms to the quality of salts produced in solar salterns has recently been recognized but not clearly understood. Using metagenomic 16S rRNA gene sequencing approach, we showed the microbial composition difference between the Tuban crystallization pond (CP-Tuban) that produces low-quality salt and CP-Sampang as a representative solar saltern that yields high-quality salt. Dominant classes in both traditional salterns were represented by γ-proteobacteria and halobacteria that occurred at higher prevalence in CP-Sampang. Microbial taxa, including beneficial genera, in CP-Sampang were more diverse and abundant compared to CP-Tuban. Among 180 genus-level OTUs identified in CP-Sampang, 127 of them were considered unique due to their absence in CP-Tuban. Higher levels of dissolved oxygen (DO) and nutrient (phosphate, nitrate, and ammonia) in the seawater reservoir (SR) of Sampang may contribute to more diverse phytoplankton genera, which could support the growth of beneficial heterotrophic microbes that positively affect the salt quality of the CP-Sampang. Low number of Dunaleilla sp. in both CPs do not seem to influence the quality of salts produced. The outcome of these comparative studies provides new insights into the contribution of diverse microbial taxa in correlation with physico-chemical parameters and phytoplankton communities to the high quality of salts produced in traditional solar salterns. The presence of beneficial genera in the enriched microbial cultures could provide an important basis for further applications, such as improving the quality of salt produced and producing unique compounds and enzymes.

Eukaryotic algal community composition in tropical environments from solar salterns to the open sea

Tropical environments with unique abiotic and biotic factors—such as salt ponds, mangroves, and coral reefs—are often in close proximity. The heterogeneity of these environments is reflected in community shifts over short distances, resulting in high biodiversity. While phytoplankton assemblages physically associated with corals, particularly their symbionts, are well studied, less is known about phytoplankton diversity across tropical aquatic environments. We assess shifts in phytoplankton community composition along inshore to offshore gradients by sequencing and analyzing 16S rRNA gene amplicons using primers targeting the V1-V2 region that capture plastids from eukaryotic phytoplankton and cyanobacteria, as well as heterotrophic bacteria. Microbial alpha diversity computed from 16S V1-V2 amplicon sequence variant (ASV) data from 282 samples collected in and around Curaçao, in the Southern Caribbean Sea, varied more within the dynamic salt ponds, salterns, and mangroves, compared to the seemingly stable above-reef, off-reef, and open sea environments. Among eukaryotic phytoplankton, stramenopiles often exhibited the highest relative abundances in mangrove, above-reef, off-reef, and open sea environments, where cyanobacteria also showed high relative abundances. Within stramenopiles, diatom amplicons dominated in salt ponds and mangroves, while dictyochophytes and pelagophytes prevailed above reefs and offshore. Green algae and cryptophytes were also present, and the former exhibited transitions following the gradient from inland to offshore. Chlorophytes and prasinophyte Class IV dominated in salt ponds, while prasinophyte Class II, including Micromonas commoda and Ostreococcus Clade OII, had the highest relative abundances of green algae in mangroves, above-reef, off-reef, and the open sea. To improve Class II prasinophyte classification, we sequenced 18S rRNA gene amplicons from the V4 region in 41 samples which were used to interrelate plastid-based results with information on uncultured prasinophyte species from prior 18S rRNA gene-based studies. This highlighted the presence of newly described Ostreococcus bengalensis and two Micromonas candidate species. Network analyses identified co-occurrence patterns between individual phytoplankton groups, including cyanobacteria, and heterotrophic bacteria. Our study reveals multiple uncultured and novel lineages within green algae and dictyochophytes in tropical marine habitats. Collectively, the algal diversity patterns and potential co-occurrence relationships observed in connection to physicochemical and spatial influences help provide a baseline against which future change can be assessed.

Nanohaloarchaea as beneficiaries of xylan degradation by haloarchaea.

Climate change, desertification, salinisation of soils and the changing hydrology of the Earth are creating or modifying microbial habitats at all scales including the oceans, saline groundwaters and brine lakes. In environments that are saline or hypersaline, the biodegradation of recalcitrant plant and animal polysaccharides can be inhibited by salt-induced microbial stress and/or by limitation of the metabolic capabilities of halophilic microbes. We recently demonstrated that the chitinolytic haloarchaeon Halomicrobium can serve as the host for an ectosymbiont, nanohaloarchaeon 'Candidatus Nanohalobium constans'. Here, we consider whether nanohaloarchaea can benefit from the haloarchaea-mediated degradation of xylan, a major hemicellulose component of wood. Using samples of natural evaporitic brines and anthropogenic solar salterns, we describe genome-inferred trophic relations in two extremely halophilic xylan-degrading three-member consortia. We succeeded in genome assembly and closure for all members of both xylan-degrading cultures and elucidated the respective food chains within these consortia. We provide evidence that ectosymbiontic nanohaloarchaea is an active ecophysiological component of extremely halophilic xylan-degrading communities (although by proxy) in hypersaline environments. In each consortium, nanohaloarchaea occur as ectosymbionts of Haloferax, which in turn act as scavenger of oligosaccharides produced by xylan-hydrolysing Halorhabdus. We further obtained and characterised the nanohaloarchaea-host associations using microscopy, multi-omics and cultivation approaches. The current study also doubled culturable nanohaloarchaeal symbionts and demonstrated that these enigmatic nano-sized archaea can be readily isolated in binary co-cultures using an appropriate enrichment strategy. We discuss the implications of xylan degradation by halophiles in biotechnology and for the United Nation's Sustainable Development Goals.

Solar Salterns and Pollution: Valorization of Some Endemic Species as Sentinels in Ecotoxicology.

Solar salterns and salt marshes are unique ecosystems with special physicochemical features and characteristic biota. Currently, there are very few studies focused on the impacts of pollution on these economic and ecological systems. Unfortunately, diversified pollution (metals, Polycyclic Aromatic Hydrocarbons, etc.) has been detected in these complex ecosystems. These hypersaline environments are under increasing threat due to anthropogenic pressures. Despite this, they represent a valuable source of microbial diversity, with taxa displaying special features in terms of environmental remediation capacities as well as economical species such as Artemia spp. (Branchiopoda) and Dunaliella salina (Chlorophyta). In this review, we discuss the impacts of pollution on these semi-artificial systems. Therefore, we have indicated the sentinel species identified in plankton communities, which can be used in ecotoxicological investigations in solar salterns. In future, researchers should increase their interest in pollution assessment in solar salterns and salt marshes.

Halobacterium wangiae sp. nov. and Halobacterium zhouii sp. nov., two extremely halophilic archaea isolated from sediment of a salt lake and saline soil of an inland saltern.

Two novel halophilic archaeal strains, Gai3-17T and XZYJT26T, were isolated from the sediment of Gaize salt lake and the saline soil of Mangkang ancient solar saltern in Tibet, PR China, respectively. Strains Gai3-17T and XZYJT26T were related to each other (96.5 and 89.7% similarity, respectively) and showed 97.5-95.4 and 91.5-87.7% similarities to the current members of Halobacterium based on 16S rRNA and rpoB' genes. The phylogenomic analysis indicated that strains Gai3-17T and XZYJT26T formed two distinct clades and clustered with the Halobacterium species. The two strains can be differentiated from the type strains of the six species with validly published names based on several phenotypic characteristics. The phospholipids of the two strains were phosphatidic acid, phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. One major glycolipid, sulphated galactosyl mannosyl glucosyl diether, was detected in strain Gai3-17T, while four glycolipids, mannosyl glucosyl diether, sulphated mannosyl glucosyl diether, disulphated mannosyl glucosyl diether and sulphated galactosyl mannosyl glucosyl diether were observed in strain XZYJT26T. The average nucleotide identity, digital DNA-DNA hybridization and amino acid identity values among the two strains and the members of Halobacterium were no more than 81, 25 and 77 %, respectively. These overall genome-related indices were below the threshold values for species boundary, indicating that strains Gai3-17T and XZYJT26T represent two novel species of Halobacterium. Thus, two novel species, Halobacterium wangiae sp. nov. and Halobacterium zhouii sp. nov., are proposed to accommodate strains Gai3-17T (=CGMCC 1.16101T=JCM 33551T) and XZYJT26T (=CGMCC 1.16682T=JCM 33556T), respectively.

Metagenome-derived virus-microbe ratios across ecosystems.

It is generally assumed that viruses outnumber cells on Earth by at least tenfold. Virus-to-microbe ratios (VMR) are largely based on counts of fluorescently labelled virus-like particles. However, these exclude intracellular viruses and potentially include false positives (DNA-containing vesicles, gene-transfer agents, unspecifically stained inert particles). Here, we develop a metagenome-based VMR estimate (mVRM) that accounts for DNA viruses across all stages of their replication cycles (virion, intracellular lytic and lysogenic) by using normalised RPKM (reads per kilobase of gene sequence per million of mapped metagenome reads) counts of the major capsid protein (MCP) genes and cellular universal single-copy genes (USCGs) as proxies for virus and cell counts, respectively. After benchmarking this strategy using mock metagenomes with increasing VMR, we inferred mVMR across different biomes. To properly estimate mVMR in aquatic ecosystems, we generated metagenomes from co-occurring cellular and viral fractions (>50 kDa-200 µm size-range) in freshwater, seawater and solar saltern ponds (10 metagenomes, 2 control metaviromes). Viruses outnumbered cells in freshwater by ~13 fold and in plankton from marine and saline waters by ~2-4 fold. However, across an additional set of 121 diverse non-aquatic metagenomes including microbial mats, microbialites, soils, freshwater and marine sediments and metazoan-associated microbiomes, viruses, on average, outnumbered cells by barely two-fold. Although viruses likely are the most diverse biological entities on Earth, their global numbers might be closer to those of cells than previously estimated.

Streptomyces salinarius sp. nov., an actinomycete isolated from solar saltern soil.

An actinobacterium, designated strain SS06011T, was isolated from solar saltern soil collected from Samut Sakhon province, Thailand. The taxonomic position of this strain was established using the polyphasic taxonomic approach. The strain produced grey aerial spore mass on International Streptomyces Project 2 seawater agar that differentiated into spiral spore chains with rugose-surfaced spores. Strain SS06011T was found to have ll-diaminopimelic acid in the cell peptidoglycan. Whole-cell hydrolysates contained galactose, glucose and ribose. MK-9(H6) and MK-9(H4) were major menaquinones. The major cellular fatty acids comprised iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol were detected in cells. These characteristics were coincident with the typical morphological and chemotaxonomic properties of the genus Streptomyces. The taxonomic affiliation at the genus level of this strain could also be confirmed by its 16S rRNA gene sequence data. Strain SS06011T showed the highest 16S rRNA gene sequence similarity to Streptomyces ardesiacus NRRL B-1773T (99.1 %), Streptomyces coelicoflavus NBRC 15399T (99.1 %) and Streptomyces hyderabadensis OU-40T (99.1 %). Digital DNA-DNA hybridization (dDDH), average nucleotide identity-blast (ANIb) and average amino acid identity (AAI) values between strain SS06011T and its closely related type strains, S. ardesiacus NBRC 15402T, S. coelicoflavus NBRC 15399T and S. hyderabadensis JCM 17657T, were in the range of 45.4-48.4 % (for dDDH), 90.8-91.9 % (for ANIb) and 90.8-91.7 % (for AAI), respectively, which are lower than the cut-off criteria for species delineation. The DNA G+C content of genomic DNA was 71.9 mol%. With the differences in physiological, biochemical and genotypic data, strain SS06011T could be discriminated from its closest neighbours. Thus, strain SS06011T should be recognized as representing a novel species of the genus Streptomyces, for which the name Streptomyces salinarius sp. nov. is proposed. The type strain is SS06011T (=TBRC 9951T=NBRC 113998T).

A halophilic Chromohalobacter species from estuarine coastal waters as a detoxifier of manganese, as well as a novel bio-catalyst for synthesis of n-butyl acetate.

Anthropogenic pollution due to ferro-manganese ore transport by barges through the Mandovi estuary in Goa, India is a major environmental concern. In this study a manganese (Mn) tolerant, moderately halophilic Chromohalobacter sp. belonging to the family Halomonadaceae was isolated from the sediments of a solar saltern adjacent to this Mandovi estuary. Using techniques of Atomic absorption spectroscopy, Scanning electron microscopy-Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy and Atomic Force Microscopy, the Chromohalobacter sp. was explored for its ability to tolerate and immobilize Mn in amended and unamended media with 20% natural salt concentration (w/v). In aqueous media supplemented with 0.1 mM Mn, the Chromohalobacter sp. was capable of sequestering up to 76% Mn with an average immobilization rate of 8 mg Mn /g /day. Growth rate kinetic analysis using Gompertz mathematical functions was found to model the experimental data well. The model inferred that the maximum growth rate of Chromohalobacter sp. was at 10% natural salt concentration (w/v). The Chromohalobacter sp. was further found to be multimetal tolerant showing high tolerance to Iron (Fe), Nickel (Ni) and Cobalt (Co), (each at 4 mM), and tolerated Manganese (Mn) up to 6 mM. Morphologically, the Chromohalobacter sp. was a non-spore forming, Gram negative motile rod (0.726 μ× 1.33 μ). The adaptative mechanism of Chromohalobacter sp. to elevated Mn concentrations (1 mM) resulted in the reduction of its cell size to 0.339 μ× 0.997 μ and the synthesis of an extracellular slime, immobilizing Mn from the liquid phase forming Manganese oxide, as confirmed by Scanning Electron Microscopy. The expression of Mnx genes for manganese oxidation further substantiated the finding. This bacterial synthesized manganese oxide also displayed catalytic activity (∼50% conversion) for the esterification of butan-1-ol with CH3COOH to yield n-butyl acetate. This Chromohalobacter sp. being indigenous to marine salterns, has adapted to high concentrations of heavy metals and high salinities and can withstand this extremely stressed environment, and thus holds a tremendous potential as an environmentally friendly "green bioremediator" of Mn from euryhaline environments. The study also adds to the limited knowledge about metal-microbe interactions in extreme environments. Further, since Chromohalobacter sp. exhibits commendable catalytic activity for the synthesis of n-butyl acetate, it would have several potential industrial applications.

Antimicrobial Activity of Extremely Halophilic Archaea Isolated from Southern Thai Salt-Fermented Products and Solar Saltern of Pattani, Thailand

This research aimed to study the diversity and antimicrobial activity of culturable haloarchaea in soil samples of solar saltern in Pattani Province, Thailand and Southern Thai salt-fermented food. Seventy-seven extremely haloarchaea were isolated on Halophilic medium agar containing 25% NaCl at 37°C for 7-21 days. They were grouped by Amplified Ribosomal DNA Restriction Analysis (ARDRA) with two restriction enzymes, RsaI and HindIII. The ARDRA patterns illustrated 6 different Operation Taxonomic Units (OTUs). Partial 16S rRNA gene sequences (938 bp) of the representative of each OTUs were aligned with the GenBank database. The results showed that the representatives of OTU1, OTU2, OTU3, OTU4, OTU5, and OTU6 had 99-100% similarity to Halobacterium salinarum, 99-100% similarity to Halostagnicola larsenii, 99% similarity to Natronococcus sp., 99-100% similarity to Haloferax alexandrinus, 99-100% similarity to Natrialba sp. and 97% similarity to Halococcus sp., respectively. The antimicrobial activity testing of the 17 isolated haloarchaeal strains from solar saltern was performed against 5 tested strains of Hbt. salinarum and 1 strain of Natrialba sp. were isolated from fermented food. Seven (41.2%) were candidate halocin-producing strains. In addition, no phage activity was observed. The 14-day fermentation broth of Natronococcus sp. SS13 showed the highest antimicrobial activity against Hbt. salinarum PK08, BD07 and BD09 (&gt;5,120 AU/ml).

Comparative Genomics of Halobacterium salinarum Strains Isolated from Salted Foods Reveals Protechnological Genes for Food Applications.

Archaeal cell factories are becoming of great interest given their ability to produce a broad range of value-added compounds. Moreover, the Archaea domain often includes extremophilic microorganisms, facilitating their cultivation at the industrial level under nonsterile conditions. Halophilic archaea are studied for their ability to grow in environments with high NaCl concentrations. In this study, nine strains of Halobacterium salinarum were isolated from three different types of salted food, sausage casings, salted codfish, and bacon, and their genomes were sequenced along with the genome of the collection strain CECT 395. A comparative genomic analysis was performed on these newly sequenced genomes and the publicly available ones for a total of 19 H. salinarum strains. We elucidated the presence of unique gene clusters of the species in relation to the different ecological niches of isolation (salted foods, animal hides, and solar saltern sediments). Moreover, genome mining at the single-strain level highlighted the metabolic potential of H. salinarum UC4242, which revealed the presence of different protechnological genes (vitamins and myo-inositol biosynthetic pathways, aroma- and texture-related features, and antimicrobial compounds). Despite the presence of genes of potential concern (e.g., those involved in biogenic amine production), all the food isolates presented archaeocin-related genes (halocin-C8 and sactipeptides).

Isolation and characterization of halophilic and halotolerant fungi from man-made solar salterns in Pattani Province, Thailand.

The present study explored culturable halophilic and halotolerant fungi from man-made solar salterns in Pattani Province, Thailand. A total of 24 fungal isolates were discovered and characterized using morphological and molecular identification. Production of extracellular enzymes, secondary metabolites and mycoviruses was examined. Growth was observed in salinity and temperature ranges between 0%-20% and 28-40°C, respectively. Growth in different environmental conditions confirmed the halophilic or halotolerant nature of some strains. Fungal isolates were phylogenetically classified into seven different genera belonging to Aspergillus, Cladosporium, Curvularia, Diaporthe, Ectophoma, Fusarium and Penicillium. An enzymatic production test revealed that thirteen isolates could produce proteases and amylases at different levels. The presence of mycoviruses was detected in three isolates. Seventeen of the 24 isolates produced antimicrobial metabolites. The majority of these active isolates were identified as Aspergillus and Penicillium species. Crude extracts of the fungal mycelia and culture broths from these isolates had an inhibitory effect on both Gram-positive and Gram-negative bacteria and human pathogenic fungi. Research into fungi from saline environments could reveal fungal strains of biotechnological and industrial interest.

INVESTIGATING THE MICROBIOTA OF SOLAR SALTERN OF MULUND, MUMBAI, INDIA

Solar salterns, located in tropical and subtropical areas worldwide, are artificial shallow ponds for the production ofhalite (NaCl) from seawater. They are often built as multipond systems. Multi-pond solar salterns have been widespreadenvironments for studies on halophilic microorganisms. In the present study Archaeal and bacterial diversity of thesalterns located at Mulund (19°10’12’’N, 72°57’18’’E), Mumbai was investigated. Three Halophiles were isolated fromthe brine samples collected. All isolated archaea were shown intensely orange pigmentation. These salt tolerantorganisms were characterized using morphological, biochemical and 16S rRNA analysis. Phylogenetic analysis of thesesequences revealed a range of identities to several group of bacteria. The clones fell into major lineages theActinobacteria and firmicutes. Presence of industrially important carotenoids producing halophiles were also recorded.