Culturable halophilic archaea at the initial and crystallization stages of salt production in a natural solar saltern of Goa, India

Genomic insights on carotenoid synthesis by extremely halophilic archaea Haloarcula rubripromontorii BS2, Haloferax lucentense BBK2 and Halogeometricum borinquense E3 isolated from the solar salterns of India

Haloarchaeal cultures were isolated from solar salterns of Goa and Tamil Nadu and designated as BS2, BBK2 and E3. These isolates grew with a characteristic bright orange to pink pigmentation and were capable of growing in media containing upto 25% (w/vol) NaCl. Whole genome sequencing (WGS) of the three haloarchaeal strains BS2, BBK2 and E3 indicated an assembled genomic size of 4.1 Mb, 3.8 Mb and 4 Mb with G + C content of 61.8, 65.6 and 59.8% respectively. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the archaeal isolates belong to Haloarcula, Haloferax and Halogeometricum genera. Haloarcula rubripromontorii BS2  was predicted to have 4292 genes with 4242 CDS regions, 46 tRNAs, 6 rRNAs and 3 misc_RNAs. In case of Haloferax lucentense  BBK2,, 3840 genes with 3780 CDS regions were detected along with 52 tRNAs, 5 rRNAs and 3 misc_RNAs. Halogeometricum borinquense  E3 contained 4101 genes, 4043 CDS regions, 52 tRNAs, 4 rRNAs, and 2 misc_RNAs. The functional annotation and curation of the haloarchaeal genome, revealed C50 carotenoid biosynthetic genes like phytoene desaturase/carotenoid 3' -4' desaturase (crtI), lycopene elongase (ubiA/lyeJ) and carotenoid biosynthesis membrane protein (cruF) in the three isolates. Whereas crtD (C-3',4' desaturase), crtY (lycopene cyclase) and brp/blh (β-carotene dioxygenase) genes were identified only in BS2.

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 × 104 CFU/g of viable number of colonies on 25% NaCl Tryptone Yeast Extract (NTYE) agar after 30-45 days 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 ± 0.14 µm 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 (3.95 cm) and root length (6.38 cm), and fresh weight (0.039 g) 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.

Combination of in situ iodization and Haloferax spp. bacteria enrichment in salt crystallization process

Salts that meet the standard quality are enriched with micronutrients, such as potassium iodate, at least 30 ppm. The iodization can be carried out directly in crystallization ponds (in-situ iodization) in salt fields. This paper reports the effectiveness of in-situ iodization technology combined with the enrichment of Halophilic bacteria consortium and Haloferax spp. to produce bio-based NaCl salt. The brine was first crystallized under sunlight exposure for approximately five days with water temperatures of 32-39 °C and an average wind speed of 2.8-6.0 m/s in each pond with a dimension of 20 × 20 m. Following this, the performance of these bacteria was analyzed in terms of the resulting final concentration of KIO3 (ppm), NaCl concentration (v/v), and water content (v/v). Results showed that the treatment with in situ iodization and Haloferax spp. successfully produce better bio-based salt quality in terms of KIO3 level, NaCl purity, and water contents. Moreover, the method did not produce aqueous and solid wastes, unlike in the conventional salt industry. The optimum condition was found at 50 ppm of KIO3 with the addition of Haloferax spp. SEM analysis shows that the treatment using Haloferax spp. resulted in a larger rectangular and harder crystal salt than the controls.

Microbial community and functional prediction during the processing of salt production in a 1000-year-old marine solar saltern of South China

In Hainan Island, South China, a 1000-year-old marine saltern has been identified as an intangible cultural heritage due to its historical complicated salt-making techniques, whereas the knowledge about this saltern is extremely limited. Herein, DNA sequencing and biochemical technologies were applied to determine bacterial and fungal communities of this saltern and their possible functions during four stages of salt-making, i.e. seawater storage, mud solarization, brine concentrating, and solar crystallization. The results showed that both of bacterial and fungal communities were suffered from significant changes during processing of salt-making in Danzhou Ancient Saltern, whereas the richness and diversity of bacterial community dominated by Proteobacteria, Bacteroidota and Cyanobacteria was considerably greater than that of fungal community dominated by Ascomycota, Basidiomycota and Mortierellomycota. Additionally, the succession of bacterial community was closely associated with both of salt physicochemical properties (Na⁺, Cl^-, total phosphorus, total nitrogen, Ca²⁺ and Mg²⁺) and bacteria themselves, whereas fungal community was more closely associated with physicochemical properties than fungi themselves. Importantly, Cyanobium_PCC-6307, Synechococcus_CC9902, Marinobacter, Prevotella and Halomonas as dominant bacterial genera respectively related to the metabolisms of amino acid, carbohydrate, terpenoids/polyketides, lipid and nucleotide were correlated with salt flavors. Saprophytic and saprotroph-symbiotroph fungi dominated by Aspergillus, Mortierella, Amanita, Neocucurbitaria and Tausonia also played core roles in the formation of salt flavors including umami and sweet smells. These findings revealed the highly specified microbiome community in this 1000-year-old saltern that mainly selected by brine solarization on basalt platforms, which is helpful to explore the underlying mechanisms of traditional salt-making techniques and to explore the useful microbes for nowadays food, medicine and chemical industries.

Isolation of Halomicroarcula pellucida strain GUMF5, an archaeon from the Dead Sea-Israel possessing cellulase

A strain designated GUMF5 was isolated in Goa-India from sediments of Dead Sea-Israel  and identified as haloarchaeon Halomicroarcula pellucida based on 16S rRNA gene analysis similarity value of 99.84%. Strain GUMF5 grew on mineral salts medium with 20% NaCl and 0.5% carboxymethyl cellulose-sodium (CMC-Na) as a sole source of carbon and produced haloextremozyme cellulase. The enzyme was concentrated using Sephadex G20, precipitated with ethanol, dialyzed and retentate purified using Sephadex G200, the size exclusion chromatography. A yield of 78.53% cellulase with an activity of 131.13 U/mg and 1.24-fold purity was obtained. The purified cellulase had optimum activity at 20% NaCl, at 40 ºC, 0.5% CMC-Na, pH 7 and 150 rpm. SDS-PAGE combined with zymographic analysis revealed the molecular weight of cellulase as 240 kDa, 40 kDa and 17.4 kDa. The activity of the enzyme was stimulated by metallic cations in the order of Ca⁺² > Mn⁺² > Mg⁺² > SO₄ ^2- > NH₄ ⁺ and was inhibited by Ag⁺  > Fe⁺² > Cu⁺². Methanol and ethanol enhanced the cellulase activity by 6% and 26%, respectively. The haloextremozyme cellulase degraded Whatman No. 1 filter paper indicated in scanning electron micrographs, exposure of open pores and fibers without any intra connectivity corresponding to paperase activity and implicating the possible use of enzyme to bio-convert cellulosic waste. Conclusively, Halomicroarcula pellucida GUMF5 (Accession number: MH244431), globally, is the only Halomicroarcula pellucida isolated from the sediments of Dead Sea producing haloextremozyme cellulase, and hence is an important biotechnological resource.

The oil spill and the use of chemical surfactant reduce microbial corrosion on API 5L steel buried in saline soil

In order to evaluate the biocorrosion of API 5L metal buried in saline soils, three different conditions in microcosms were evaluated. The control microcosm contained only saline soil, the second had the addition of petroleum, and the third contained the addition of both petroleum and surfactant. The corrosion rate of the metals was measured by loss of mass after 30 days, and the microbial communities were delineated using 16S rRNA gene sequencing techniques. The species were dominated by halophiles in all samples analyzed. Among the bacteria, the predominant group was Proteobacteria, with emphasis on the Alphaproteobacteria and Gammaproteobacteria. Betaproteobacteria and Deltaproteobacteria members were also identified in a smaller number in all conditions. Firmicutes were especially abundant in the control system, although it was persistently present in other conditions evaluated. Bacteroidetes and Actinobacteria were also present in a considerable number of OTUs in the three microcosms. Halobacteria were predominant among archaea and were present in all conditions. The analysis pointed to a conclusion that in the control microcosm, the corrosion rate was higher, while the microcosm containing only oil had the lowest corrosion rate. These results suggest that, under these conditions, the entry of other carbon sources favors the presence of petroleum degraders, rather than samples involved in the corrosion of metals.

Resistance of a Halobacterium salinarum isolate from a solar saltern to cadmium, lead, nickel, zinc, and copper

The current study focuses on the tolerance of a strain of Halobacterium salinarum isolated from Sfax solar saltern (Tunisia) towards cadmium (Cd), lead (Pb), nickel (Ni), zinc (Zn), and copper (Cu) by using agar dilution methods in complex and minimal media. The results showed the least inhibitory metals based on Minimum Inhibitory Concentrations (MICs) were lead (MIC = 4.5 mM), cadmium (MIC = 4 mM), and nickel (MIC = 2.5 mM) in complex medium. The MICs of these metals were more inhibitory (MIC < 2 mM) in the other tested media. The archaeal strain revealed a high sensitivity for copper and zinc, with MICs below 0.5 mM for both metals. Growth kinetics in complex and minimal media showed the strain to be more sensitive to the metals in liquid media than in solid media. The growth kinetic assays indicated the presence of selected heavy metals resulted in a lower growth rate and lower total cell mass relative to the control. Despite that cadmium and lead are nonessential and have no nutrient value, they were the most tolerated metals by H. salinarum strain. In addition, pigment intensity in the strain was inhibited by the presence of the heavy metals relative to the control.

The microbiology of red brines

The brines of natural salt lakes with total salt concentrations exceeding 30% are often colored red by dense communities of halophilic microorganisms. Such red brines are found in the north arm of Great Salt Lake, Utah, in the alkaline hypersaline lakes of the African Rift Valley, and in the crystallizer ponds of coastal and inland salterns where salt is produced by evaporation of seawater or some other source of saline water. Red blooms were also reported in the Dead Sea in the past. Different types of pigmented microorganisms may contribute to the coloration of the brines. The most important are the halophilic archaea of the class Halobacteria that contain bacterioruberin carotenoids as well as bacteriorhodopsin and other retinal pigments, β-carotene-rich species of the unicellular green algal genus Dunaliella and bacteria of the genus Salinibacter (class Rhodothermia) that contain the carotenoid salinixanthin and the retinal protein xanthorhodopsin. Densities of prokaryotes in red brines often exceed 2-3×10⁷ cells/mL. I here review the information on the biota of the red brines, the interactions between the organisms present, as well as the possible roles of the red halophilic microorganisms in the salt production process and some applied aspects of carotenoids and retinal proteins produced by the different types of halophiles inhabiting the red brines.

Transient Dynamics of Archaea and Bacteria in Sediments and Brine Across a Salinity Gradient in a Solar Saltern of Goa, India

The microbial fluctuations along an increasing salinity gradient during two different salt production phases – initial salt harvesting (ISH) phase and peak salt harvesting (PSH) phase of Siridao solar salterns in Goa, India were examined through high-throughput sequencing of 16S rRNA genes on Illumina MiSeq platform. Elemental analysis of the brine samples showed high concentration of sodium (Na⁺) and chloride (Cl^–) ions thereby indicating its thalassohaline nature. Comparison of relative abundance of sequences revealed that Archaea transited from sediment to brine while Bacteria transited from brine to sediment with increasing salinity. Frequency of Archaea was found to be significantly enriched even in low and moderate salinity sediments with their relative sequence abundance reaching as high as 85%. Euryarchaeota was found to be the dominant archaeal phylum containing 19 and 17 genera in sediments and brine, respectively. Phylotypes belonging to Halorubrum, Haloarcula, Halorhabdus, and Haloplanus were common in both sediments and brine. Occurence of Halobacterium and Natronomonas were exclusive to sediments while Halonotius was exclusive to brine. Among sediments, relative sequence frequency of Halorubrum, and Halorhabdus decreased while Haloarcula, Haloplanus, and Natronomonas increased with increasing salinity. Similarly, the relative abundance of Haloarcula and Halorubrum increased with increasing salinity in brine. Sediments and brine samples harbored about 20 and 17 bacterial phyla, respectively. Bacteroidetes, Proteobacteria, and Chloroflexi were the common bacterial phyla in both sediments and brine while Firmicutes were dominant albeit in sediments alone. Further, Gammaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria were observed to be the abundant class within the Proteobacteria. Among the bacterial genera, phylotypes belonging to Rubricoccus and Halomonas were widely detected in both brine and sediment while Thioalkalispira, Desulfovermiculus, and Marinobacter were selectively present in sediments. This study suggests that Bacteria are more susceptible to salinity fluctuations than Archaea, with many bacterial genera being compartment and phase-specific. Our study further indicated that Archaea rather than Bacteria could withstand the wide salinity fluctuation and attain a stable community structure within a short time-frame.

16S rRNA molecular profiling of heavy metal tolerant bacterial communities isolated from soil contaminated by electronic waste

Electronic waste is an evolving source of harmful pollutants in our surrounding environments and considered to be perilous as it contains toxic metals such as chromium, cadmium, lead, mercury, zinc, and nickel in huge quantities. Heavy metals are harmful contaminants and accumulated in the environment due to various anthropogenic activities. The present study was conducted to isolate and characterize different heavy metal tolerant bacterial species, based on molecular techniques from soil contaminated by electronic waste. The contaminated soil samples were analyzed for various physicochemical properties such as pH, electrical conductivity, soil moisture, water holding capacity, organic carbon, organic matter, available phosphorus, total nitrogen, and potassium using standard procedures. The soil samples were found to contain a higher amount of different heavy metals such as copper, chromium, lead, iron, cadmium, and nickel. Serial dilution and spread plate techniques have been used for bacterial isolation. The identification and molecular characterization of isolated bacterial species were done by biochemical tests and 16S rRNA gene sequencing technique. The 16S rRNA sequencing analysis confirmed the presence of different bacterial species as, Micrococcus aloeverae, Kocuria turfanensis, Bacillus licheniformis, Bacillus jeotgali, Bacillus velezensis, and Bacillus haikouensis. The findings indicated that the e-waste dumping sites are the storehouse of elite bacterial species. The present research study offers a platform for systematic analysis of e-waste sites by microbial profiling that may help in the innovation of novel microorganisms of scientific importance and better biotechnological potential.

Taxonomically Characterized and Validated Bacterial Species Based on 16S rRNA Gene Sequences from India During the Last Decade

Microbial taxonomy dealing with identification and characterization of prokaryotes like bacteria and archaea has always been a major area of research all over the world. Exploring diversity of microbes and description of novel species with different genes and secondary compounds is of utmost importance for better future and sustenance of life. India having an enormous range of ecosystems and diverse species inhabiting these niches is considered to be one of the richest biodiversity regions of the world. During the last decade, with newer methodologies and better technology, the prokaryotic taxonomy from India has extended our inventory of microbial communities in specific niches. However, there still exist some limitations in classifying the microbes from India as compared to that is done world-over. This review enlists the taxonomic description of novel taxa of prokaryotes from India in the past decade. A total of 378 new bacterial species have been classified from different habitats in India in the last ten years and no descriptions of archaeal species is documented till date.

Haloferax sulfurifontis GUMFAZ2 producing xylanase-free cellulase retrieved from Haliclona sp. inhabiting rocky shore of Anjuna, Goa-India

Salt stable cellulases are implicated in detritic food webs of marine invertebrates for their role in the degradation of cellulosic material. A haloarchaeon, Haloferax sulfurifontis GUMFAZ2 producing cellulase was successfully isolated from marine Haliclona sp., a sponge inhabiting the rocky intertidal region of Anjuna, Goa. The culture produced extracellular xylanase-free cellulase with a maximum activity of 11.7 U/ml, using carboxymethylcellulose-Na (CMC-Na), as a sole source of carbon in 3.5 M NaCl containing medium, pH 7 at 40°C and produced cellobiose and glucose, detectable by thin-layer chromatography. Nondenaturing polyacrylamide gel electrophoresis of the crude enzyme, revealed a single protein band of 19.6 kDa which on zymographic analysis exhibited cellulase activity while corresponding sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a molecular weight of 46 kDa. Unlike conventional cellulases, this enzyme is active in presence of 5 M NaCl and does not have accompanying xylanase activity, hence can be considered as xylanase-free cellulase. Such enzymes from haloarchaea offer great potential for biotechnological application because of their stability at high salinity and is therefore worth pursuing.

Diversity and bioprospecting of extremely halophilic archaea isolated from Algerian arid and semi-arid wetland ecosystems for halophilic-active hydrolytic enzymes

The diversity of haloarchaea associated with different dry salt lakes in northeastern Algeria was investigated together with their potential of hydrolytic enzyme production. A total of 68 aerobic halophilic archaea were isolated from saline sediments. Based on the 16S rRNA gene sequencing, the isolates were assigned to seven phylotypes within the class Halobacteria, namely Haloarcula, Halococcus, Haloferax, Halogeometricum, Haloterrigena, Natrialba, and Natrinema. The results showed that Haloferax group was found to be dominant in all samples (30 isolates) (44%) with high diversity, followed by Halococcus spp. (13%) (9 isolates). All phylotypes are extreme halophiles and thermotolerant with the ability to grow at temperatures up to 48 °C. In addition, the screening for extracellular halophilic enzymes showed that 89.7% of the isolates were able to produce at least two types of the screened enzymes. The strains producing esterase, gelatinase, inulinase, cellulase and protease activities were the most diverse functional group. These data showed an abundant and diverse haloarchaeal community, detected in Algerian wetland ecosystems, presenting a promising source of molecules with important biotechnological applications.

Utilization of Sugarcane Bagasse by Halogeometricum borinquense Strain E3 for Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Sugarcane bagasse (SCB), one of the major lignocellulosic agro-industrial waste products, was used as a substrate for biosynthesis of polyhydroxyalkanoates (PHA) by halophilic archaea. Among the various wild-type halophilic archaeal strains screened, Halogeometricum borinquense strain E3 showed better growth and PHA accumulation as compared to Haloferaxvolcanii strain BBK2, Haloarcula japonica strain BS2, and Halococcus salifodinae strain BK6. Growth kinetics and bioprocess parameters revealed the maximum PHA accumulated by strain E3 to be 50.4 ± 0.1 and 45.7 ± 0.19 (%) with specific productivity (qp) of 3.0 and 2.7 (mg/g/h) using NaCl synthetic medium supplemented with 25% and 50% SCB hydrolysate, respectively. PHAs synthesized by strain E3 were recovered in chloroform using a Soxhlet apparatus. Characterization of the polymer using crotonic acid assay, X-ray diffraction (XRD), differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR), and proton nuclear magnetic resonance (¹H-NMR) spectroscopy analysis revealed the polymer obtained from SCB hydrolysate to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] comprising of 13.29 mol % 3HV units.

Expression and Function of Different Guanine-Plus-Cytosine Content 16S rRNA Genes in Haloarcula hispanica at Different Temperatures

The halophilic archaeon Haloarcula hispanica harbors three ribosomal RNA (rRNA) operons (rrnA, rrnB, and rrnC) that contain the 16S rRNA genes rrsA, rrsB, and rrsC, respectively. Although rrsB and rrsC (rrsBC) have almost identical sequences, the rrsA and rrsBC sequences differ by 5.4%, and they differ by 2.5% with respect to guanine-plus-cytosine content (P_GC). The strong correlation between the typical growth temperatures of archaea and P_GC of their 16S rRNA genes suggests that H. hispanica may harbor different 16S rRNA genes having different P_GC to maintain rapid growth in a wide range of temperatures. We therefore performed reverse transcription-coupled quantitative PCR to assess expression levels of rrsA (P_GC, 58.9%) and rrsBC (P_GC, 56.4-56.5%) at various temperatures. The expression ratio of rrsA to rrsBC increased with culture temperature. Mutants with complete deletions of one or two of the three rRNA operons were constructed and their growth rates at different temperatures compared to that of the wild-type. The growth characteristics of the rRNA operon single-mutant strains were indistinguishable from the wild-type. The rRNA operon double-mutant strains maintained the same temperature range as wild-type but displayed reduced growth rates. In particular, the double-mutant strains grew much slower than wild-type at low temperature related to minimum growth temperature of the wild-type. On the other hand, at physiologically high temperatures the wild-type and the double-mutant strain which harbors only rrnA with high-P_GCrrsA grew significantly faster than the double-mutant strain which harbors only rrnC with low-P_GCrrsC. These findings suggest the importance of 16S rRNAs transcribed from rrsA with high-P_GC in maintaining rapid growth of this halophilic archaeon at raised growth temperatures.

Isolation, Identification and Extracellular Enzymatic Activity of Culturable Extremely Halophilic Archaea and Bacteria of IncheBoroun Wetland

Extremely halophilic diversity of IncheBroun wetland located in the north of Iran was investigated by using culture-dependent methods. Sampling was carried out in May and September 2014. In each sampling 4 distinct regions of wetland were analyzed by using complex media like MGM, JCM168, MH1 and an alkaliphilic medium containing 23% salts. After incubation at 40°C, a total of 406 isolates and 2.1 × 106 CFU/ml were obtained in culture media. Among them 361 isolates were obtained from MGM and 39 isolates from JCM 168, 3 isolates from MH1 and 3 isolates from the alkaliphilic media. Initial morphological, biochemical and physiological tests were performed. Production of 4 hydrolytic enzymes by 45 selected strains was assayed qualitatively. A total of 38, 19 and 6 strains were able to produce lipase, DNase and amylase activity. Protease activity was not observed among strains. As total 45 strains were selected randomly and phylogenetic analysis of 16S rRNA was performed for them. Among selected strains 40 isolated strians belonged to Haloarchaea and were belonged to the genera: Haloarcula(30%), Halorubrum(27.5%), Haloferax(17.5%), Halobellus (10%), Halogeometricum(5.2%), Halobacterium(2.6%), Halolamina(2.6%), Halorhabdus (2.6%) and Halostagnicola (2.6%). Haloarcula and Halorubrum were the dominant populations. A total of 5 strains belonged to domain of Bacteria and were similar to members of Rhodovibrio (40%), Pseudomonas (40%) and Salicola (20%).

Isolation, Identification and Extracellular Enzymatic Activity of Culturable Extremely Halophilic Archaea and Bacteria of IncheBoroun Wetland

Extremely halophilic diversity of IncheBroun wetland located in the north of Iran was investigated by using culture-dependent methods. Sampling was carried out in May and September 2014. In each sampling 4 distinct regions of wetland were analyzed by using complex media like MGM, JCM168, MH1 and an alkaliphilic medium containing 23% salts. After incubation at 40°C, a total of 406 isolates and 2.1 × 106CFU/ml were obtained in culture media. Among them 361 isolates were obtained from MGM and 39 isolates from JCM 168, 3 isolates from MH1 and 3 isolates from the alkaliphilic media. Initial morphological, biochemical and physiological tests were performed. Production of 4 hydrolytic enzymes by 45 selected strains was assayed qualitatively. A total of 38, 19 and 6 strains were able to produce lipase, DNase and amylase activity. Protease activity was not observed among strains. As total 45 strains were selected randomly and phylogenetic analysis of 16S rRNA was performed for them. Among selected strains 40 isolated strians belonged to Haloarchaea and were belonged to the genera:Haloarcula(30%),Halorubrum(27.5%),Haloferax(17.5%),Halobellus(10%),Halogeometricum(5.2%),Halobacterium(2.6%),Halolamina(2.6%),Halorhabdus(2.6%) andHalostagnicola(2.6%).HaloarculaandHalorubrumwere the dominant populations. A total of 5 strains belonged to domain ofBacteriaand were similar to members ofRhodovibrio(40%),Pseudomonas(40%) andSalicola(20%).

Biology and survival of extremely halophilic archaeon Haloarcula marismortui RR12 isolated from Mumbai salterns, India in response to salinity stress

Haloarchaea are unique microorganism’s resistant to environmental and osmotic stresses and thrive in their habitats despite extreme fluctuating salinities. In the present study, haloarchaea were isolated from hypersaline thalossohaline salterns of Bhandup, Mumbai, India and were identified as Haloferax prahovense, Haloferax alexandrines, Haloferax lucentense, Haloarcula tradensis, Haloarcula marismortui and Haloarcula argentinensis. The mechanism of adaptation to contrasting salinities (1.5 M and 4.5 M) was investigated in the extreme haloarchaeon, Hal. marismortui RR12. Hal. marismortui RR12 increased the intracellular sequestration of K⁺ and Cl⁻ ions in hypo salinity and hyper salinity respectively as detected by Energy-dispersive X-ray spectroscopy microanalysis (EDAX) and Inductively Coupled Plasma- atomic Emission Spectroscopy (ICP-AES) indicating the presence of ‘salt-in’ strategy of osmoadaptation. As a cellular response to salinity stress, it produced small heat shock like proteins (sHSP) identified using MALDI-TOF MS and increased the production of protective red carotenoid pigment. This is the first report on the study of the concomitant cellular, molecular and physiological mechanism adapted by Hal. marismortui RR12 when exposed to contrasting salinities in external environment.

The heterotrophic eubacterial and archaeal co-inhabitants of the halophilic Dunaliella salina in solar salterns fed by Bay of Bengal along south eastern coast of India

Halophilic microbes are studied to understand the metabolic pathways adopted by organisms in such extreme environment and for their biotechnological exploitation. In thallosohaline environments worldwide, the autotrophic alga Dunaliella salina Teodoresco is omnipresent, but it is being recently realised that the heterotrophic components vary in different regions. The unexplored eastern coastline of India abutted by Bay of Bengal was investigated for the heterotrophic halophilic microbes in this region. The waters in the salterns – replicas of natural hyper-saline water bodies of that region, were collected at four sites along 650 km of the coastal belt. In cultures set up from these waters, green and pink colonies were observed. The green colonies were found to be those of D. salina while the pink colonies were of heterotrophs. To identify the heterotrophic microbes, light microscopy, 16S rRNA typing and pigment profiling through spectrophotometry and HPLC were done. The cells in pink colonies were rod shaped. 16S rRNA typing of cells in these colonies detected the presence of Halomonas sp. – a eubacterium. The pigment profile of cells in pink cultures matched that of the archaea – Halobacterium; bacterioruberin derivatives were found. Thus, it was concluded that Halomonas and Halobacterium spp. are among the co-inhabitant heterotrophs of D. salina. Cultures of D. salina established from these salterns showed the typical three colours seen in the ponds of different sub-plots of salterns. They were green until 30 days, turning dark orange by 60 days and pink when 90 day old. In the 90 day old cultures, innumerable rod shaped cells were found. These cells were similar to the cells of the waters from the ponds of pink sub-plots of salterns and the pink colonies established from saltern waters in the laboratory. In the old (90 days) laboratory cultures of D. salina, the glycerol and proteins released from degenerating cells and the increase in salt concentration to super saturation levels due to evaporation of water in the medium led to the gregarious appearance of the heterotrophs – the co-inhabitants in natural environment.

Anti-bacterial TeNPs biosynthesized by haloarcheaon Halococcus salifodinae BK3

Microbial synthesis of highly structured metal sulfide and metallic nanoparticles is a benign approach of nanomaterial synthesis. Various microbes have been exploited for nanoparticle synthesis, but nanofabrication using haloarchaea is still in nascent stages. Here, we report the intracellular synthesis of hexagonal needle-shaped tellurium nanoparticles with an aspect ratio of 1:4.4, by the haloarcheon Halococcus salifodinae BK3. The isolate was able to tolerate up to 5.5 mM K2TeO3. The yield of tellurium nanoparticles was highest when the culture was exposed to 3 mM K2TeO3, even though the isolate exhibited slightly decreased growth rate as compared to the culture growing in the absence of K2TeO3. The enzyme tellurite reductase was responsible for tellurite resistance and nanoparticle synthesis in H. salifodinae BK3. These tellurium nanoparticles exhibited anti-bacterial activities against both Gram-positive and Gram-negative bacteria, with higher antibacterial activity towards Gram-negative bacteria. This is the first report on the synthesis of tellurium nanoparticles by Halophilic archaea.

Patterns and determinants of halophilic archaea (class halobacteria) diversity in tunisian endorheic salt lakes and sebkhet systems

We examined the diversity and community structure of members of the halophilic Archaea (class Halobacteria) in samples from central and southern Tunisian endorheic salt lakes and sebkhet (also known as sebkha) systems using targeted 16S rRNA gene diversity survey and quantitative PCR (qPCR) approaches. Twenty-three different samples from four distinct locations exhibiting a wide range of salinities (2% to 37%) and physical characteristics (water, salt crust, sediment, and biofilm) were examined. A total of 4,759 operational taxonomic units at the 0.03 (species-level) cutoff (OTU0.03s) belonging to 45 currently recognized genera were identified, with 8 to 43 genera (average, 30) identified per sample. In spite of the large number of genera detected per sample, only a limited number (i.e., 2 to 16) usually constituted the majority (≥80%) of encountered sequences. Halobacteria diversity showed a strong negative correlation to salinity (Pearson correlation coefficient = -0.92), and community structure analysis identified salinity, rather than the location or physical characteristics of the sample, as the most important factor shaping the Halobacteria community structure. The relative abundance of genera capable of biosynthesis of the compatible solute(s) trehalose or 2-sulfotrehalose decreased with increasing salinities (Pearson correlation coefficient = -0.80). Indeed, qPCR analysis demonstrated that the Halobacteria otsB (trehalose-6-phosphatase)/16S rRNA gene ratio decreases with increasing salinities (Pearson correlation coefficient = -0.87). The results highlight patterns and determinants of Halobacteria diversity at a previously unexplored ecosystem and indicate that genera lacking trehalose biosynthetic capabilities are more adapted to growth in and colonization of hypersaline (>25% salt) ecosystems than trehalose producers.

Exploration of a haloarchaeon, Halostagnicola larsenii, isolated from rock pit sea water, West Coast of Maharashtra, India, for the production of bacteriorhodopsin

AIMS

The aim of the present investigation was to isolate haloarchaea from rock pit sea water, West Coast of India and to explore their potential in the production of bacteriorhodopsin (BR) which converts light energy into electrical energy.

METHODS AND RESULTS

Haloarchaeal strains were isolated from rock pit sea water samples collected from Rock garden, Malvan, West Coast of India. Based on morphological, physiological and biochemical characteristics, and 16S rRNA gene sequencing, all the 11 strains were identified as Halostagnicola larsenii. All the strains require at least 1·5 mol l(-1) NaCl for growth; grow optimally in the range of 3·5-5·2 mol l(-1) NaCl. BR was detected in all the strains ranging from 0·035 to 0·258 g l(-1) . All 11 strains showed conversion of light energy into electrical energy in the range of 0·7-44·2 mV, when exposed to sunlight.

CONCLUSIONS

A haloarchaeon, Hst. larsenii is isolated from rock pit sea water and demonstrated to have BR that converted light energy into electrical energy.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present investigation is presumably the first report of the isolation of Hst. larsenii from low salinity environment and its potential in production of BR. The haloarchaeon could be explored for the generation of electrical energy.

Cadmium resistance in extremely halophilic archaeon Haloferax strain BBK2

Halophilic archaea are prevalent in highly saline habitats. Haloferax strain BBK2 is an orange pigmented, exopolysaccharide (EPS) producing extremely halophilic archaeon, isolated from solar salterns of Ribandar, Goa, India. It grew in varying pH (5-10) and NaCl concentration (10-30%). The isolate grew well in complex (NTYE) and minimal media (NGSM) in presence of heavy metal cadmium (Cd) up to 4.0 mM (805.28 mg L(-1)) concentration. The optimum growth in the presence and absence of Cd was seen at a pH range of 7-9 and salinity of 15-25%. The growth kinetics of the isolate in NTYE showed a specific growth rate (μmax) of 0.352 with generation time of 1.968 days. In presence of 1mM Cd, the μmax was 0.325 day(-1) and generation time was 2.132 days. In NGSM, the μmax decreased from 0.517 day(-1) (in control) to 0.265 day(-1) in 1mM Cd while, the doubling time increased from 1.34 days in control to 2.615 days in presence of 1 mM Cd. SDS PAGE of the whole cell protein extracts showed overexpressed proteins of 74.14 and 40 kDa. The scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM-EDX) analysis of the intact cells and cells disrupted by dialysis revealed that Cd was bound onto the cells, which was further confirmed by AAS, FTIR and XRD analysis.

Diversity of cultivable halophilic archaea and bacteria from superficial hypersaline sediments of Tunisian solar salterns

Prokaryotes in the superficial sediments are ecologically important microorganisms that are responsible for the decomposition, mineralization and subsequent recycling of organic matter. The aim of this study was to explore the phylogenetic and functional diversity of halophilic archaea and bacteria isolated from the superficial sediments of solar salterns at Sfax, Tunisia. Sixty four strains were isolated from crystallizer (TS18) and non-crystallizer (M1) ponds and submitted to genotypic characterization and evaluation by amplified ribosomal RNA restriction analysis (ARDRA) techniques. Our findings revealed that the archaeal diversity observed for 29 isolates generated five distinct patterns from the non-crystallizer M1 pond, with Halorubrum chaoviator as the most prevalent cultivable species. However, in the TS18 crystallizer pond, ten restriction patterns were observed, with the prevalence of haloarchaea EB27K, a not yet identified genotype. The construction of a neighbour-joining tree of 16S rRNA gene sequences resulted in the division of the potential new species into two major groups, with four strains closely related to the sequence of the unculturable haloarchaeon EB27K and one strain to the recently described Halovenus aranensis strain. The 35 bacterial strains observed in this work were present only in the non-crystallizer pond (M1) and presented two distinct ARDRA patterns. These strains belonged to the γ-proteobacteria subdivision, with members of Salicola marasensis (83%) being the most predominant species among the isolates. 16S rRNA gene sequencing revealed that Salicola strains displayed different degrees of homogeneity. The results from pulsed field gel electrophoresis assays showed that the Salicola isolates could be clustered in two distinct groups with different genome sizes.

Trehalose/2-sulfotrehalose biosynthesis and glycine-betaine uptake are widely spread mechanisms for osmoadaptation in the Halobacteriales

We investigated the mechanisms of osmoadaptation in the order Halobacteriales, with special emphasis on Haladaptatus paucihalophilus, known for its ability to survive in low salinities. H. paucihalophilus genome contained genes for trehalose synthesis (trehalose-6-phosphate synthase/trehalose-6-phosphatase (OtsAB pathway) and trehalose glycosyl-transferring synthase pathway), as well as for glycine betaine uptake (BCCT family of secondary transporters and QAT family of ABC transporters). H. paucihalophilus cells synthesized and accumulated ∼1.97-3.72 μmol per mg protein of trehalose in a defined medium, with its levels decreasing with increasing salinities. When exogenously supplied, glycine betaine accumulated intracellularly with its levels increasing at higher salinities. RT-PCR analysis strongly suggested that H. paucihalophilus utilizes the OtsAB pathway for trehalose synthesis. Out of 83 Halobacteriales genomes publicly available, genes encoding the OtsAB pathway and glycine betaine BCCT family transporters were identified in 38 and 60 genomes, respectively. Trehalose (or its sulfonated derivative) production and glycine betaine uptake, or lack thereof, were experimentally verified in 17 different Halobacteriales species. Phylogenetic analysis suggested that trehalose synthesis is an ancestral trait within the Halobacteriales, with its absence in specific lineages reflecting the occurrence of gene loss events during Halobacteriales evolution. Analysis of multiple culture-independent survey data sets demonstrated the preference of trehalose-producing genera to saline and low salinity habitats, and the dominance of genera lacking trehalose production capabilities in permanently hypersaline habitats. This study demonstrates that, contrary to current assumptions, compatible solutes production and uptake represent a common mechanism of osmoadaptation within the Halobacteriales.

Accumulation of polyhydroxyalkanoates by halophilic archaea isolated from traditional solar salterns of India

Extremely halophilic archaeal isolates obtained from brine and sediment samples of solar salterns of Goa and Tamil Nadu, India were screened for accumulation of polyhydroxyalkanoates (PHA). Seven polymer accumulating haloarchaeal strains (TN4, TN5, TN6, TN7, TN9, TN10 and BBK2) were selected based on their growth and intensity of fluorescence when grown on 20 % NaCl synthetic medium supplemented with 2 % glucose and incorporated with Nile red dye. The polymer was quantified by conversion of PHA to crotonic acid which gave a characteristic absorption maxima at 235 nm. On the basis of phenotypic and genotypic characterization the cultures TN4, TN5, TN6, TN7, TN10 and BBK2 were grouped under genus Haloferax whereas isolate TN9 was grouped under the genus Halogeometricum. Growth kinetics and polymer accumulation studies revealed that the culture Halogeometricum borinquense strain TN9 accumulates PHA maximally at the mid-log phase, i.e. 5th day of growth (approx. 14 wt% PHA of CDW). Analysis of the polymer by IR, (1)H NMR and (13)C NMR confirmed it to be a homopolymer of 3-hydroxybutyrate.

Synthesis of silver nanoparticles using haloarchaeal isolate Halococcus salifodinae BK3

Numerous bacteria, fungi, yeasts and viruses have been exploited for biosynthesis of highly structured metal sulfide and metallic nanoparticles. Haloarchaea (salt-loving archaea) of the third domain of life Archaea, on the other hand have not yet been explored for nanoparticle synthesis. In this study, we report the intracellular synthesis of stable, mostly spherical silver nanoparticles (AgNPs) by the haloarchaeal isolate Halococcus salifodinae BK3. The culture on adaptation to silver nitrate exhibited growth kinetics similar to that of the control. NADH-dependent nitrate reductase was involved in silver tolerance, reduction, synthesis of AgNPs, and exhibited metal-dependent increase in enzyme activity. The AgNPs preparation was characterized using UV-visible spectroscopy, XRD, TEM and EDAX. The XRD analysis of the nanoparticles showed the characteristic Bragg peaks of face-centered cubic silver with crystallite domain size of 22 and 12 nm for AgNPs synthesized in NTYE and halophilic nitrate broth (HNB), respectively. The average particle size obtained from TEM analysis was 50.3 and 12 nm for AgNPs synthesized in NTYE and HNB, respectively. This is the first report on the synthesis of silver nanoparticles by haloarchaea.

Properties of Halococcus salifodinae, an Isolate from Permian Rock Salt Deposits, Compared with Halococci from Surface Waters

Halococcus salifodinae BIp^T DSM 8989^T, an extremely halophilic archaeal isolate from an Austrian salt deposit (Bad Ischl), whose origin was dated to the Permian period, was described in 1994. Subsequently, several strains of the species have been isolated, some from similar but geographically separated salt deposits. Hcc. salifodinae may be regarded as one of the most ancient culturable species which existed already about 250 million years ago. Since its habitat probably did not change during this long period, its properties were presumably not subjected to the needs of mutational adaptation. Hcc. salifodinae and other isolates from ancient deposits would be suitable candidates for testing hypotheses on prokaryotic evolution, such as the molecular clock concept, or the net-like history of genome evolution. A comparison of available taxonomic characteristics from strains of Hcc. salifodinae and other Halococcus species, most of them originating from surface waters, is presented. The cell wall polymer of Hcc. salifodinae was examined and found to be a heteropolysaccharide, similar to that of Hcc. morrhuae. Polyhydroxyalkanoate granules were present in Hcc. salifodinae, suggesting a possible lateral gene transfer before Permian times.

Characterization of polyhydroxyalkanoates accumulated by a moderately halophilic salt pan isolate Bacillus megaterium strain H16

AIM

Characterization of polyhydroxyalkanoates (PHA) accumulated by halophilic bacteria isolated from solar salterns.

METHODS AND RESULTS

Twenty-six halophilic isolates were obtained from solar salterns of Goa, India. They were screened for accumulation of PHA by Sudan black B, Nile blue A and Nile red stains. Strains H15, H16 and H26 were selected based on their intensity of Nile blue A/Nile red fluorescence. On the basis of phenotypic and genotypic characterization, the three isolates were identified as Bacillus megaterium. Growth kinetics and polymer accumulating capacity of strain H16 were studied in E2 mineral media with 2% glucose with/without NaCl. In the absence of NaCl, strain H16 accumulated PHA to 40·0% (w/w) of cell dry weight (CDW) at 42 h of growth, whereas in presence of 5% w/v NaCl, the culture showed longer lag phase of up to 24 h and accumulated a maximum PHA of 39% (w/w) CDW at 54 h of growth. The infrared spectra of both the polymers exhibited peaks at 1733·9 cm(-1) characteristic of C=O. Scans of (1) H nuclear magnetic resonance (NMR) showed a doublet at 2·5 ppm corresponding to methylene group (-CH(2)), the signal at 5·3 ppm corresponded to methine group (-CH-), and another signal at 1·3 ppm corresponded to the methyl group (-CH(3)). Scans of (13)C NMR showed prominent peaks at 20, 40, 67-68 and 170 ppm, indicating the polymer to be homopolymer of 3-hydroxybutyrates. The polymer is stable up to a temperature of 160°C.

CONCLUSION

Three moderately halophilic isolates (strain H15, H16 and H26) capable of accumulating PHA were isolated from solar salterns of Ribandar Goa, India, and identified as B. megaterium based on phenotypic and genotypic characterization. Strain H16 accumulated polyhydroxybutyrate in the presence and absence of NaCl up to 40% of its CDW.

SIGNIFICANCE AND IMPACT OF THE STUDY

This strain would be better suited for production of PHA at industrial level due to its tolerance to high concentration of NaCl.

Community solar salt production in Goa, India

Traditional salt farming in Goa, India has been practised for the past 1,500 years by a few communities. Goa's riverine estuaries, easy access to sea water and favourable climatic conditions makes salt production attractive during summer. Salt produced through this natural evaporation process also played an important role in the economy of Goa even during the Portuguese rule as salt was the chief export commodity. In the past there were 36 villages involved in salt production, which is now reduced to 9. Low income, lack of skilled labour, competition from industrially produced salt, losses incurred on the yearly damage of embankments are the major reasons responsible for the reduction in the number of salt pans.Salt pans (Mithagar or Mithache agor) form a part of the reclaimed waterlogged khazan lands, which are also utilised for aquaculture, pisciculture and agriculture. Salt pans in Goa experience three phases namely, the ceased phase during monsoon period of June to October, preparatory phase from December to January, and salt harvesting phase, from February to June. After the monsoons, the salt pans are prepared manually for salt production. During high tide, an influx of sea water occurs, which enters the reservoir pans through sluice gates. The sea water after 1-2 days on attaining a salinity of approximately 5ºBé, is released into the evaporator pans and kept till it attains a salinity of 23 - 25ºBé. The brine is then released to crystallizer pans, where the salt crystallises out 25 - 27ºBé and is then harvested.Salt pans form a unique ecosystem where succession of different organisms with varying environmental conditions occurs. Organisms ranging from bacteria, archaea to fungi, algae, etc., are known to colonise salt pans and may influence the quality of salt produced.The aim of this review is to describe salt farming in Goa's history, importance of salt production as a community activity, traditional method of salt production and the biota associated with salt pans.