Temperature governs the distribution of hot spring microbial community in three hydrothermal fields, Eastern Tibetan Plateau Geothermal Belt, Western China

The eastern Tibetan Plateau geothermal belt in the southwest of China hosts a number of hot springs with a wide range of temperature and hydrogeochemical conditions, which may harbor different niches for the distribution of microbial communities. In this study, we investigated hydrochemical characteristics and microbial community composition in 16 hot springs with a temperature range of 34.6 to 88.2 °C within and across three typical hydrothermal fields (Kangding, Litang, and Batang). According to aquifer lithologic and tectonic differences, the hydrochemical compositions of hot springs displayed an apparent regional-specific pattern with distinct distributions of major and trace elements (e.g., Ca²⁺, Mg²⁺, F^-/B) and were primarily formed by water-rock interaction across the three hydrothermal fields. Nonetheless, microbial communities significantly assembled with the temperature rather than the geographic locations with distinct hydrogeological features. Low temperature (<45 °C), moderate temperature (55-70 °C) and high temperature (>70 °C) groups were identified based on their community compositions. Proteobacteria and Nitrospirae were the predominant phyla in low-temperature hot springs, while in moderate to high-temperature springs they were mainly composed of Aquificae, Deinococcus-Thermus, Thermodesulfobacteria, Thermotogae and Cyanobacteria. Variation partition analysis suggested a higher explanation of temperature (29.6%) than spatial variable (1.8%) and other geochemical variables (2.5%) on the microbial distribution. Microbial co-occurrence network showed >80% negative associations hinting a low co-existence pattern and highlighted the driving force of temperature as well as F^- or total organic carbon (TOC) for microbial interactions. Microbial dissimilarity displayed significant linear correlations with environmental (temperature) and geographic distance in Batang but only with temperature in Kangding area, which might be attributed to the regional-specific hydrogeochemistry. This study may help us to better understand the distribution of the microbial community in hot spring across different hydrothermal fields.

Parasite Communities of Oreochromis niloticus baringoensis (Trewavas, 1983) in Relation to Selected Water Quality Parameters in the Springs of Lorwai Swamp and Lake Baringo, Kenya

PURPOSE

Parasite infections may lead to mortalities in fish; therefore, destabilizing the biodiversity and ecosystem functions. Swamps such as the Lorwai Swamp are important water sources, and information on the parasite species infecting Oreochromis nilotocus baringoensis in the hot springs of Lorwai Swamp which have a distinct genetic makeup from their counterparts in Lake Baringo is lacking. The purpose of this study was to provide a knowledge base on the parasite species infecting O. niloticus baringoensis in these springs, facilitate their comparison with those in Lake Baringo and determine their relationship with selected water quality parameters.

METHODS

347 fish were collected and standard parasitological procedures were used to examine the presence of parasites. Physico-chemical parameters were measured in situ and water samples were collected for chlorophyll-a determination and nutrient analyses in the laboratory using standard methods. Relationship between parasitic infections and selected water quality parameters was determined by PCA using SPSS version 22.

RESULTS

Two parasite species were common in all sites: Cichlidogyrus sclerosus and Clinostomum sp. Some parasites correlated positively with some parameters; Amirthalingamia macracantha and Contracaecum sp. with nitrogen compounds. Others like Clinostomum sp. and Tylodelphys sp. correlated negatively with dissolved oxygen.

CONCLUSION

Results from this study showed that there were both positive and negative relationships between some water quality parameters and the prevalence of recovered parasites. O. niloticus baringoensis from Lake Baringo also recorded high parasite prevalence and this calls for sensitization of the public on the risks that may arise from the consumption of undercooked infected fish.

Diversity analysis and metagenomic insights into antibiotic and metal resistance among Himalayan hot spring bacteriobiome insinuating inherent environmental baseline levels of antibiotic and metal tolerance

OBJECTIVES

Mechanisms of occurrence and expression of antibiotic resistance genes (ARGs) in thermophilic bacteria are still unknown owing to limited research and data. In this research, comparative profiling of ARGs and metal tolerance genes among thermophilic bacteria has been done by functional metagenomic methods.

METHODS

Shotgun metagenomic sequence data were generated using Illumina HiSeq 4000. Putative ARGs from the PROKKA predicted genes were identified with the ardbAnno V.1.0 script available from the ARDB (Antibiotic Resistance Genes Database) consortium using the non-redundant resistance genes as a reference. Putative metal resistance genes (MRGs) were identified by using BacMetScan V.1.0. The whole-genome sequencing for bacterial isolates was performed using Illumina HiSeq 4000 sequencing technology with a paired-end sequencing module.

RESULTS

Metagenomic analysis showed the dominance of Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes in two hot springs of Sikkim. ARG analysis through shotgun gene sequencing was found to be negative in the case of thermophilic bacteria. However, few genes were detected but they showed maximum similarity with mesophilic bacteria. Concurrently, MRGs were also detected in the metagenome sequence of isolates from hot springs. Detection of MRGs and absence of ARGs investigated by whole-genome sequencing in the reference genome sequence of thermophilic Geobacillus also conveyed the same message.

CONCLUSION

The study of ARGs and MRGs (Heavy metal resistance gene) among culturable and non-culturable bacteria from the hot springs of Sikkim via metagenomics showed a preferential selection of MRGs over ARGs. The absence of ARGs also does not support the co-selection of ARGs and MRGs in these environments. This evolutionary selection of metal resistance over antibiotic genes may have been necessary to survive in the geological craters which have an abundance of different metals from earth sediments rather than antibiotics. Furthermore, the selection could be environment driven depending on the susceptibility of ARGs in a thermophilic environments as it reduces the chances of horizontal gene transfer.

Characterizing the Mineral Assemblages of Hot Spring Environments and Applications to Mars Orbital Data

Certain martian hydrated silica deposits have been hypothesized to represent ancient hot spring environments, but many environments can produce hydrated silica on Earth. This study compares the mineral assemblages produced in terrestrial hot springs to those observed in silica-producing volcanic fumarolic environments to determine which diagnostic features of hot springs could be remotely sensed on Mars. We find that hot spring environments are more likely to produce geochemically mature silica (i.e., opal-CT and microcrystalline quartz) in addition to opal-A, whereas volcanic fumarolic environments tend to produce only opal-A, potentially reflecting differences in water-to-rock ratios. Neutral/alkaline hot springs contain few accessory minerals (typically calcite and Fe/Mg clays), while acidic hot springs commonly contain accessory kaolinite. By comparison, mineral assemblages at volcanic fumaroles contain protolith igneous minerals and a diversity of alteration minerals indicative of acidic conditions. Based on these terrestrial observations, the presence of opal-CT and/or microcrystalline quartz could be more diagnostic of a hot spring origin rather than a fumarolic origin, and accessory mineralogy could provide information on formation pH. On Mars, we observe that most orbital opal detections in outcrop are opal-A, sometimes accompanied by Fe/Mg clays, suggestive of neutral/alkaline conditions. However, these observations do not uniquely distinguish between hot springs and fumarolic environments, as opal-A can occur in both environments. Many martian silica detections occur in regionally extensive units, and sometimes in association with fluvial landforms suggesting a detrital or lower temperature authigenic origin. Thus, only a few martian opal detections may be mineralogically, spatially, and morphologically consistent with a hot spring origin. However, although it is difficult to unambiguously identify martian hot spring environments from orbital data sets, the orbital data are still valuable for identifying siliceous sites that are consistent with higher biosignature preservation potential, that is, sites with opal-A (not opal-CT), for future in situ investigations.

Biomolecules from Fossilized Hot Spring Sinters: Implications for the Search for Life on Mars

Hot spring environments are commonly dominated by silica sinters that precipitate by the rapid cooling of silica-saturated fluids and the activity of microbial communities. However, the potential for preservation of organic traces of life in silica sinters back through time is not well understood. This is important for the exploration of early life on Earth and possibly Mars. Most previous studies have focused on physical preservation in samples <900 years old, with only a few focused on organic biomarkers. In this study, we investigate the organic geochemistry of hot spring samples from El Tatio, Chile and the Taupo Volcanic Zone, with ages varying from modern to ∼9.4 ka. Results show that all samples contain opaline silica and contain hydrocarbons that are indicative of a cyanobacterial origin. A ∼3 ka recrystallized, quartz-bearing sample also contains traces of cyanobacterial biomarkers. No aromatic compounds were detected in a ∼9.4 ka opal-A sample or in a modern sinter breccia sample. All other samples contain naphthalene, with one sample also containing other polyaromatic hydrocarbons. These aromatic hydrocarbons have a thermally mature distribution that is perhaps reflective of geothermal fluids migrating from deep, rather than surface, reservoirs. These data show that hot spring sinters can preserve biomolecules from the local microbial community, and that crystallinity rather than age may be the determining factor in their preservation. This research provides support for the exploration for biomolecules in opaline silica deposits on Mars.

The Case for Ancient Hot Springs in Gusev Crater, Mars

The origin and age of opaline silica deposits discovered by the Spirit rover adjacent to the Home Plate feature in the Columbia Hills of Gusev crater remains debated, in part because of their proximity to sulfur-rich soils. Processes related to fumarolic activity and to hot springs and/or geysers are the leading candidates. Both processes are known to produce opaline silica on Earth, but with differences in composition, morphology, texture, and stratigraphy. Here, we incorporate new and existing observations of the Home Plate region with observations from field and laboratory work to address the competing hypotheses. The results, which include new evidence for a hot spring vent mound, demonstrate that a volcanic hydrothermal system manifesting both hot spring/geyser and fumarolic activity best explains the opaline silica rocks and proximal S-rich materials, respectively. The opaline silica rocks most likely are sinter deposits derived from hot spring activity. Stratigraphic evidence indicates that their deposition occurred before the emplacement of the volcaniclastic deposits comprising Home Plate and nearby ridges. Because sinter deposits throughout geologic history on Earth preserve evidence for microbial life, they are a key target in the search for ancient life on Mars.

Bacterial diversity and functional metagenomics expounding the diversity of xenobiotics, stress, defense and CRISPR gene ontology providing eco-efficiency to Himalayan Hot Springs

Sikkim is one of the bio-diverse states of India, which harbors diverse alkaline and sulfur rich hot springs in its vicinity. However, there is a dearth of data present in terms of microbial and its functional diversity as only a few hot springs have been studied in this area. Thus, in this regard, microbial and functional diversity of two hot springs by NGS, PLFA, and culture-independent approaches were carried out. PLFA and culture-dependent analysis was complementary as the Gram-positive bacteria were abundant in both the hot springs with the dominance of phylum Firmicutes with Geobacillus. Metagenomic analysis revealed the abundance of Proteobacteria, Actinobacteria, and Firmicutes in both hot springs. Functional metagenomics suggested that both Yumthang and Reshi hot spring possess a diverse set of genes analogous to stress such as genes allied to osmotic, heat shock, and acid stresses; defense analogies such as multidrug resistance efflux pump, multidrug transport system, and β-lactamase; and CRISPR analogues such as related to Cas1, Cas2, Cas3, cmr1-5 proteins, CT1972, and CT1133 gene families. The xenobiotic analogues were found against benzoate, nitrotolune, xylene, DDT, and chlorocyclohexane/chlorobenzene degradation. Thus, these defensive mechanisms against environmental and anthropogenic hiccups and hindrances provide the eco-efficiency to such thermal habitats. The higher enzymatic, degradation, defense, stress potential and the lower percentage identity (< 95%) of isolates encourage the further exploration and exploitation of these habitats for industrial and biotechnological purposes.

Boron Isotopes in the Puga Geothermal System, India, and Their Implications for the Habitat of Early Life

Boron is associated with several Archean stromatolite deposits, including the tourmaline-rich Barberton stromatolites in South Africa and tourmaline-bearing pyritic laminae associated with stromatolites of the 3.48 Ga Dresser Formation in the Pilbara Craton, Australia. Boron is also a critical element in prebiotic organic chemistry, including in the formation of ribose, a crucial component in RNA. As geological evidence and advances in prebiotic chemistry are now suggesting that hot spring activity may be associated with the origins of life, an understanding of boron and its mobility and isotopic fractionation in geothermal settings may provide important insights into the setting for the origin of life. Here, we report on the boron isotopic compositions and elemental concentrations in a range of fluid, sediment, and mineral samples from the active, boron-rich Puga geothermal system in the Himalayas, India. This includes one of the lowest boron isotope values ever recorded in modern settings: diatom-rich sediments (δ¹¹B = -41.0‰) in a multiphase fractionation system where evaporation is not the dominant form of isotope fractionation. Instead, the extreme boron isotopic fractionation is ascribed to the incorporation of tetrahedral ¹⁰B borate anions in precipitating amorphous silica. These findings expand the known limits and drivers of boron isotope fractionation, as well as provide insight into the concentration and fractionation of boron in Archean hot spring environments.

Tolerance and sorption of Bromacil and Paraquat by thermophilic cyanobacteria Leptolyngbya 7M from Costa Rican thermal springs

We studied the adsorption ability and tolerance of the thermophilic filamentous cyanobacteria Letolyngbya 7M towards Paraquat and Bromacil. Adsorption isotherms at pH = 7.0 showed an adsorption capacity of 24.4 mg/g and 66.8 mg/g, respectively, and a good fit to the Langmuir model (R² = 0.97 and 0.99, respectively). To evaluate the effect of both herbicides on photosynthetic pigments and viability of cyanobacteria, cell autoflorescence and esterase activity was determined using flow cytometry. Autofluorescence was less sensitive to changes in cell viability, as it was only slightly reduced at high Paraquat and Bromacil concentrations. Herbicide effect on esterase activity is dose-dependent. Bromacil did not cause a significant effect on either chlorophyll a content or cell viability. This study demonstrates the potential of Leptolyngbya 7M to remove Paraquat and Bromacil herbicides from aqueous solution under laboratory conditions.

Fischerella thermalis: a model organism to study thermophilic diazotrophy, photosynthesis and multicellularity in cyanobacteria

The true-branching cyanobacterium Fischerella thermalis (also known as Mastigocladus laminosus) is widely distributed in hot springs around the world. Morphologically, it has been described as early as 1837. However, its taxonomic placement remains controversial. F. thermalis belongs to the same genus as mesophilic Fischerella species but forms a monophyletic clade of thermophilic Fischerella strains and sequences from hot springs. Their recent divergence from freshwater or soil true-branching species and the ongoing process of specialization inside the thermal gradient make them an interesting evolutionary model to study. F. thermalis is one of the most complex prokaryotes. It forms a cellular network in which the main trichome and branches exchange metabolites and regulators via septal junctions. This species can adapt to a variety of environmental conditions, with its photosynthetic apparatus remaining active in a temperature range from 15 to 58 °C. Together with its nitrogen-fixing ability, this allows it to dominate in hot spring microbial mats and contribute significantly to the de novo carbon and nitrogen input. Here, we review the current knowledge on the taxonomy and distribution of F. thermalis, its morphological complexity, and its physiological adaptations to an extreme environment.

Antibiotic resistance and heavy metal tolerance in cultured bacteria from hot springs as indicators of environmental intrinsic resistance and tolerance levels

Antibiotic resistance (AR) in the environment is a growing and global concern for public health, and intrinsic AR from pristine sites untouched by pharmaceutical antibiotics is not commonly studied. Forty aerobic bacteria were isolated from water and sediment samples of hot springs in South Africa. Resistance against ten antibiotics (carbenicillin, gentamicin, kanamycin, streptomycin, tetracycline, chloramphenicol, ceftriaxone, co-trimoxazole, nalidixic acid and norfloxacin) was tested using a standard disk diffusion assay. Resistance to one or two antibiotics were equally found in 37.5%, while the remaining 22% showed complete sensitivity. Intermediate resistance was found for ceftriaxone (52.5%), nalidixic acid (37.5%) and carbenicillin (22.5%), while low levels of resistance were observed for streptomycin (5%) and kanamycin (2.5%), and total sensitivity towards the other antibiotics. Twenty-nine isolates were also tested against eight different heavy-metal salts (Al, Cr, Cu, Fe, Hg, Mn, Ni and Pb) at 10 and 40 mM. All isolates were tolerant and able to grow on ≥2 heavy-metal salts at both concentrations. No association was observed between AR and heavy metal tolerance (HMT). Based on the relatively low AR levels, hot spring sites are pristine environments reflecting baseline levels for comparison to other potentially contaminated groundwater sites.

A review of the mechanisms of mineral-based metabolism in early Earth analog rock-hosted hydrothermal ecosystems

Prior to the advent of oxygenic photosynthesis ~ 2.8-3.2 Ga, life was dependent on chemical energy captured from oxidation-reduction reactions involving minerals or substrates generated through interaction of water with minerals. Terrestrial hydrothermal environments host abundant and diverse non-photosynthetic communities and a variety of minerals that can sustain microbial metabolism. Minerals and substrates generated through interaction of minerals with water are differentially distributed in hot spring environments which, in turn, shapes the distribution of microbial life and the metabolic processes that support it. Emerging evidence suggests that terrestrial hydrothermal environments may have played a role in supporting the metabolism of the earliest forms of microbial life. It follows that these environments and their microbial inhabitants are increasingly being studied as analogs of early Earth ecosystems. Here we review current understanding of the processes that lead to variation in the availability of minerals or mineral-sourced substrates in terrestrial hydrothermal environments. In addition, we summarize proposed mechanisms of mineral substrate acquisition and metabolism in microbial cells inhabiting terrestrial hydrothermal environments, highlighting the importance of the dynamic interplay between biotic and abiotic reactions in influencing mineral substrate bioavailability. An emphasis is placed on mechanisms involved in the solubilization, acquisition, and metabolism of sulfur- and iron-bearing minerals, since these elements were likely integrated into the metabolism of the earliest anaerobic cells.

Molecular Identification of Free-Living Amoebae (Naegleria spp., Acanthamoeba spp. and Vermamoeba spp.) Isolated from Un-improved Hot Springs, Guilan Province, Northern Iran

BACKGROUND

This study was conducted to determine the presence and molecular identify of Acanthamoeba, Naegleria and Vermamoeba in unimproved hot springs.

METHODS

From Jul to Aug 2017, 54 water samples were collected from hot springs in different parts of the Guilan Province, North Iran. For the isolation of Acanthamoeba, Naegleria and Vermamoeba approximately 500 ml of the water samples were filtered through a cellulose nitrate membrane with a pore size of 0.45 μm. The filter was transferred onto non-nutrient agar plates seeded with Gram-negative bacteria (Escherichia coli) as a food source. The morphological key of page was used to identify free-living amoebae (FLA) using an inverted microscope, PCR amplification targeting specific genes for each genus and sequencing determined frequent species and genotypes base on NCBI database.

RESULTS

Fifteen of the 54 samples were positive by culture and/or PCR for Acanthamoeba and other FLA from unimproved hot springs. By sequencing the positive isolates, the strains were shown to belong to Acanthamoeba castellanii (12 case isolates belonged to T4 genotype), 4 cases of V. vermiformis, and 3 cases of N. australiensis, 2 cases of N. pagei and 1 cases of N. gruberi.

CONCLUSION

Although FLA-mediated illnesses are not as high as in environmental distribution, but because of a poor prognosis, more investigations about FLA distribution in hot springs is critical. Hot spring may enhance exposure of the amoebae in individuals. Hence, more attention to unimproved hot springs is needed to prevent free-living amoebae mediated diseases.

Hydrolytic Enzyme Production by Thermophilic Bacteria Isolated from Saudi Hot Springs

Hydrolytic enzyme production by thermophilic bacteria isolated from hot springs in the southern region of Saudi Arabia was investigated. The physical and chemical properties of the hot springs prove to be an important environment for hydrolytic-enzyme-producing thermophilic bacteria. Eighty-four bacterial isolates were obtained from three hot springs: Al-Majardah, Al-Khubah and Al-Ardah. Screening of the isolates for enzyme production indicated that 78 isolates showed activity for one or more enzymes. Molecular identification and phylogenic analysis of selected promising isolates confirmed the identity of the isolates as Bacillus aerius, Bacillus licheniformis and Bacillus sonorensis, which have potential to produce the target enzymes α-amylase, protease and lipase, respectively. Optimization of hydrolytic enzyme production by bacterial strains was investigated using kitchen waste as a cheap carbon energy source. Maximum enzyme production was achieved after 72 hours of incubation at the beginning of the stationary phase of growth. Enzyme production was dependent on the initial pH value in the range of pH 7.5-8.5 and an optimal incubation temperature of between 55-60°C. Enzyme production increased gradually in proportion to the kitchen waste concentration; whereas maximum lipase production was gained at 5.0% (w/v) kitchen waste, 7.0% (w/v) of waste was optimal for both α-amylase and protease productivity. The results indicated that hot springs in Saudi Arabia are a substantial source of thermophilic bacteria producing industrially important enzymes using cheap and unexploited waste.

Temperature-controlled thermophilic bacterial communities in hot springs of western Sichuan, China

Background

Ganzi Prefecture in Western China is situated geographically at the transition regions between Tibetan Plateau and Sichuan Basin in a highly tectonically active boundary area between the India and Eurasia plates. The region hosts various hot springs that span a wide range of temperature from 30 to 98 °C and are located at high altitude (up to 4200 m above sea level) in the region of large geothermal anomalies and active Xianshuihe slip-fault that has been active since Holocene. The site represents a biodiversity reservoir for thermophiles, yet their diversity and relationship to geochemical parameters are largely unknown. In the present work, bacterial diversity and community structure in 14 hot springs of Ganzi were investigated using Illumina MiSeq sequencing.

Results

Bacterial community compositions were evidently distinct among the 14 hot springs, and the bacterial communities in hot springs were majorly abundant in phyla Aquificae, Cyanobacteria and Proteobacteria. Both clustering and PCoA analysis suggested the existence of four bacterial community patterns in these hot springs. Temperature contributed to shaping bacterial community structure of hot springs as revealed by correlation analysis. Abundant unassigned-genus sequences detected in this study strongly implied the presence of novel genera or genetic resources in these hot springs.

Conclusion

The diversity of hot springs of Ganzi prefecture in Western Sichuan, China is evidently shaped by temperature. Interestingly disproportionally abundant unassigned-genus sequences detected in this study show indicate potential of novel genera or phylotypes. We hypothesize that frequent earthquakes and rapidly changing environment might have contributed to evolution of these potentially new lineages. Overall, this study provided first insight into the bacterial diversity of hot springs located in Western Sichuan, China and its comparison with other similar communities worldwide.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1271-z) contains supplementary material, which is available to authorized users.

Bioprospecting thermophilic glycosyl hydrolases, from hot springs of Himachal Pradesh, for biomass valorization

The harnessing of biocatalysts from extreme environment hot spring niche for biomass conversion is significant and promising owing to the special characteristics of extremozymes attributed by intriguing biogeochemistry and extreme conditions of these environments. Hence, in the present study 38 bacterial isolates obtained from hot springs of Manikaran (~ 95 °C), Kalath (~ 50 °C) and Vasist (~ 65 °C) of Himachal Pradesh were screened for glycosyl hydrolases by in situ enrichment technique using lignocellulosic biomass (LCB). Based on their hydrolytic potential 5 isolates were selected and they were Bacillus tequilensis (VCB1, VCB2 and VSDB4), and B. licheniformis (KBFB2 and KBFB3). Cellulolytic activity assayed by growth under submerged fermentation showed that B. tequilensis VCB1 had maximum FPA activity (3.38 IU ml⁻¹) in 48 h, while B. licheniformis KBFB3 excelled for endoglucanase (EGA of 4.81 IU ml⁻¹ in 24 h) and cellobiase (0.71 IU ml⁻¹ in 48 h) activities. Among all the thermophilic biocatalysts evaluated, highest exoglucanase (0.06 IU ml⁻¹) activity was observed in B. tequilensis VSDB4 while endoglucanase of B. licheniformis KBFB3 showed optimum specific activity at pH 7 and 70 °C. Further, the presence of celS, celB and xlnB genes in the isolates suggest their possible role in biomass conversion. Protein profiling by SDS-PAGE analysis revealed that cellulase isoforms migrated with molecular masses of 75 kDa. The endoglucanase activity of promising strain B. licheniformis KBFB3 was enhanced in the presence of Ca²⁺, mercaptoethanol and sodium hypochlorite whereas moderately inhibited by Cu²⁺, Zn²⁺, urea, SDS and H₂O₂. The results of this study indicate scope for the possible development of novel biocatalysts with multifunctional thermostable glycosyl hydrolases from hot springs for efficient hydrolysis of the complex lignocellulosic biomass into simple sugars and other derived bioproducts leading to biomass valorization.

Microbial ecology of two hot springs of Sikkim: Predominate population and geochemistry

Northeastern regions of India are known for their floral and faunal biodiversity. Especially the state of Sikkim lies in the eastern Himalayan ecological hotspot region. The state harbors many sulfur rich hot springs which have therapeutic and spiritual values. However, these hot springs are yet to be explored for their microbial ecology. The development of neo generation techniques such as metagenomics has provided an opportunity for inclusive study of microbial community of different environment. The present study describes the microbial diversity in two hot springs of Sikkim that is Polok and Borong with the assist of culture dependent and culture independent approaches. The culture independent techniques used in this study were next generation sequencing (NGS) and Phospholipid Fatty Acid Analysis (PLFA). Having relatively distinct geochemistry both the hot springs are thermophilic environments with the temperature range of 50-77 °C and pH range of 5-8. Metagenomic data revealed the dominance of bacteria over archaea. The most abundant phyla were Proteobacteria and Bacteroidetes although other phyla were also present such as Acidobacteria, Nitrospirae, Firmicutes, Proteobacteria, Parcubacteria and Spirochaetes. The PLFA studies have shown the abundance of Gram Positive bacteria followed by Gram negative bacteria. The culture dependent technique was correlative with PLFA studies. Most abundant bacteria as isolated and identified were Gram-positive genus Geobacillus and Anoxybacillus. The genus Geobacillus has been reported for the first time in North-Eastern states of India. The Geobacillus species obtained from the concerned hot springs were Geobacillus toebii, Geobacillus lituanicus, Geobacillus Kaustophillus and the Anoxybacillus species includes Anoxybacillus gonensis and Anoxybacillus Caldiproteolyticus. The distribution of major genera and their statistical correlation analyses with the geochemistry of the springs predicted that the temperature, pH, alkalinity, Ca²⁺, Mg²⁺, Cl²⁺, and sulfur were main environmental variables influencing the microbial community composition and diversity. Also the piper diagram suggested that the water of both the hot springs are Ca-HCO^3- type and can be predicted as shallow fresh ground waters. This study has provided an insight into the ecological interaction of the diverse microbial communities and associated physicochemical parameters, which will help in determining the future studies on different biogeochemical pathways in these hot springs.

Rapid assessment of As and other elements in naturally-contaminated calcareous soil through hyperspectral VIS-NIR analysis

Although arsenic (As) toxicity in soil vary depending on its chemical forms and oxidation states, regulatory limits for this compartment rely on total As content. Conventional methods of total As determination are expensive and time-consuming. The development of predictive techniques might enable a speditive assessment of As contamination in those scenarios, such as thermal spring sites, where exposure to the metalloid poses a threat to human health. The objective of this study was to assess the suitability of Visible Near Infrared spectrophotometry for predicting the total As content in highly calcareous thermal spring soils and the same aim was pursued for those elements (i.e. Al, Fe and Mn) the chemistry of which is tightly connected with that of As. A Partial Least Square approach, including cross-validation and external independent test, was used to relate the concentrations of the target elements to spectral data. The most accurate prediction was found for As with Pearson's coefficient, RMSE, RPD and SEP being equal to 0.94, 69.65, 2.9 and 66.99, respectively. Less accurate predictions were found for Al (r = 0.88; RMSE = 11014; RPD = 1.96; SEP = 11014), Fe (r = 0.93; RMSE = 6921.1; RPD = 2.45; SEP = 6462.4), and Mn (r = 0.92; RMSE = 542.01; RPD = 2.43; SEP = 529.79).

Marine-influenced microbial communities inhabit terrestrial hot springs on a remote island volcano

Raoul Island is a subaerial island volcano approximately 1000 km northeast of New Zealand. Its caldera contains a circumneutral closed-basin volcanic lake and several associated pools, as well as intertidal coastal hot springs, all fed by a hydrothermal system sourced from both meteoric water and seawater. Here, we report on the geochemistry, prokaryotic community diversity, and cultivatable abundance of thermophilic microorganisms of four terrestrial features and one coastal feature on Raoul. Hydrothermal fluid contributions to the volcanic lake and pools make them brackish, and consequently support unusual microbial communities dominated by Planctomycetes, Chloroflexi, Alphaproteobacteria, and Thaumarchaeota, as well as up to 3% of the rare sister phylum to Cyanobacteria, Candidatus Melainabacteria. The dominant taxa are mesophilic to moderately thermophilic, phototrophic, and heterotrophic marine groups related to marine Planctomycetaceae. The coastal hot spring/shallow hydrothermal vent community is similar to other shallow systems in the Western Pacific Ocean, potentially due to proximity and similarities of geochemistry. Although rare in community sequence data, thermophilic methanogens, sulfur-reducers, and iron-reducers are present in culture-based assays.

Biodiversity of the microbial mat of the Garga hot spring

BACKGROUND

Microbial mats are a good model system for ecological and evolutionary analysis of microbial communities. There are more than 20 alkaline hot springs on the banks of the Barguzin river inflows. Water temperature reaches 75 °C and pH is usually 8.0-9.0. The formation of microbial mats is observed in all hot springs. Microbial communities of hot springs of the Baikal rift zone are poorly studied. Garga is the biggest hot spring in this area.

RESULTS

In this study, we investigated bacterial and archaeal diversity of the Garga hot spring (Baikal rift zone, Russia) using 16S rRNA metagenomic sequencing. We studied two types of microbial communities: (i) small white biofilms on rocks in the points with the highest temperature (75 °C) and (ii) continuous thick phototrophic microbial mats observed at temperatures below 70 °C. Archaea (mainly Crenarchaeota; 19.8% of the total sequences) were detected only in the small biofilms. The high abundance of Archaea in the sample from hot springs of the Baikal rift zone supplemented our knowledge of the distribution of Archaea. Most archaeal sequences had low similarity to known Archaea. In the microbial mats, primary products were formed by cyanobacteria of the genus Leptolyngbya. Heterotrophic microorganisms were mostly represented by Actinobacteria and Proteobacteria in all studied samples of the microbial mats. Planctomycetes, Chloroflexi, and Chlorobi were abundant in the middle layer of the microbial mats, while heterotrophic microorganisms represented mostly by Firmicutes (Clostridia, strict anaerobes) dominated in the bottom part. Besides prokaryotes, we detect some species of Algae with help of detection their chloroplasts 16 s rRNA.

CONCLUSIONS

High abundance of Archaea in samples from hot springs of the Baikal rift zone supplemented our knowledge of the distribution of Archaea. Most archaeal sequences had low similarity to known Archaea. Metagenomic analysis of microbial communities of the microbial mat of Garga hot spring showed that the three studied points sampled at 70 °C, 55 °C, and 45 °C had similar species composition. Cyanobacteria of the genus Leptolyngbya dominated in the upper layer of the microbial mat. Chloroflexi and Chlorobi were less abundant and were mostly observed in the middle part of the microbial mat. We detected domains of heterotrophic organisms in high abundance (Proteobacteria, Firmicutes, Verrucomicrobia, Planctomicetes, Bacteroidetes, Actinobacteria, Thermi), according to metabolic properties of known relatives, which can form complete cycles of carbon, sulphur, and nitrogen in the microbial mat. The studied microbial mats evolved in early stages of biosphere formation. They can live autonomously, providing full cycles of substances and preventing live activity products poisoning.

Business Performance of Health Spa Tourism Providers in Relation to the Structure of Employees in the Republic of Croatia

Health spa tourism services are provided in special hospitals for medical rehabilitation and health resorts, and include controlled use of natural healing factors and physical therapy under medical supervision in order to improve and preserve health. Health tourism is a service industry and therefore labor-intensive industry in which human resources are one of the key factors of business success. The aim of this study was to analyze business performance of special hospitals for medical rehabilitation and health resorts in Croatia in relation to the structure of employees, specifically the number of physicians and total medical personnel, as well as the share of physicians and medical personnel in the total number of employees. The assumption was that those who employ more physicians and medical employees are more successful. The empirical research was conducted and the assumption was tested firstly by correlation analysis and afterwards by regression analysis. The total number of employees in the researched health resorts and special hospitals amounted to 2,863, of which the share of physicians specialists accounted for almost 7%, while the share of total medical staff was almost 53%. From the results of our research, it can be concluded that special hospitals for medical rehabilitation and health resorts, which employ more physicians and medical personnel, are achieving better financial business performance. Based on the results obtained, it is possible to provide guidance for further growth and development in the direction of basing the primary offer on medical-health offer, rather than on wellness offer, which is a strong trend in the world. These findings are important for planning the health and tourism policies in Croatia and similar countries.

Diversity and Distribution of Thermophilic Bacteria in Hot Springs of Pakistan

Chilas and Hunza areas, located in the Main Mantle Thrust and Main Karakoram Thrust of the Himalayas, host a range of geochemically diverse hot springs. This Himalayan geothermal region encompassed hot springs ranging in temperature from 60 to 95 °C, in pH from 6.2 to 9.4, and in mineralogy from bicarbonates (Tato Field), sulfates (Tatta Pani) to mixed type (Murtazaabad). Microbial community structures in these geothermal springs remained largely unexplored to date. In this study, we report a comprehensive, culture-independent survey of microbial communities in nine samples from these geothermal fields by employing a bar-coded pyrosequencing technique. The bacterial phyla Proteobacteria and Chloroflexi were dominant in all samples from Tato Field, Tatta Pani, and Murtazaabad. The community structures however depended on temperature, pH, and physicochemical parameters of the geothermal sites. The Murtazaabad hot springs with relatively higher temperature (90-95 °C) favored the growth of phylum Thermotogae, whereas the Tatta Pani thermal spring site TP-H3-b (60 °C) favored the phylum Proteobacteria. At sites with low silica and high temperature, OTUs belonging to phylum Chloroflexi were dominant. Deep water areas of the Murtazaabad hot springs favored the sulfur-reducing bacteria. About 40% of the total OTUs obtained from these samples were unclassified or uncharacterized, suggesting the presence of many undiscovered and unexplored microbiota. This study has provided novel insights into the nature of ecological interactions among important taxa in these communities, which in turn will help in determining future study courses in these sites.

Bio-prospecting Bacterial Diversity of Hot Springs in Northern Himalayan Region of India for Laccases

Bacterial diversity of hot springs of northern Himalayan region of India was studied and explored for laccases, the multicopper enzymes applicable in a large number of industries due to their ability to utilize a wide range of substrates. 220 operational taxonomic units (OTUs) out of 5551 sequence reads for bacterial diversity and 3 OTUs out of 19 sequence reads for Laccase like multicopper oxidases (LMCOs) diversity were generated. Bacteroidetes (74.28%) was the most abundant phylum including genus Paludibacter (66.96%), followed by phylum Proteobacteria (24.53%) including genera Chitinilyticum (7.55%) and Cellvibrio (6.14%). In case of laccase diversity, three LMCO sequences showed affiliation with proteobacteria and one with two domain laccase from uncultivable bacteroidetes. LMCO sequences belonged to H and N families.

Comparative analysis of microbial diversity in two hot springs of Bakreshwar, West Bengal, India

Various aspects of hot springs at Bakreshwar (Lat. 23°52'48″N; Long. 87°22'40″E) in West Bengal, India have been investigated since the middle of 20th century, but comprehending the complete diversity and the complexity of the microbial population therein has been in the continuing process. Some of these microorganisms are found to have immense industrial importance. Microbes generally exist in milieus of varying complexities and diversities. Attempting the usually employed cultivation-based techniques in experimentation with those microbes had confronted various limitations. To overcome these limitations a strategy based on high-throughput sequencing of 16S rRNA gene amplicon analysis was employed for studying the differential diversity and the detailed nature of microbial population of the two hot springs of Bakreshwar (54 °C & 65 °C). Paired-end libraries of amplified V-3 hyper-variable 16S rDNA fragments from sets of samples that varied in their contents, ranging from a single bacterium to highly complex communities were sequenced. The comparison revealed the differential aspects in the two hot spring waters; the samples at 54 °C showed the bacterial phylum Firmicutes (65.85%) and Synergistetes (27.24%) predominating and those from hot spring water at 65 °C showed the abundance of the phyla Firmicutes (96.10%) and Proteobacteria (3.36%). The presence of Archaea in the hot springs could not be ascertained.

Characterization of culturable bacteria isolated from hot springs for plant growth promoting traits and effect on tomato (Lycopersicon esculentum) seedling

To elucidate the functional diversity of hot spring bacteria, 123 bacteria were isolated and screened for evaluating their multifunctional plant growth promoting (PGP) properties. The antagonistic activity against different phytopathogens showed the presence of a high amount of biocontrol bacteria in the hot springs. During screening for PGP properties, 61.0% isolates showed production of indole acetic acid and 23.6% showed inorganic phosphate solubilization qualitatively. For production of extracellular enzymes, it was found that 61.0% isolates produced lipase, 56.9% produced protease, and 43.9% produced cellulase. In extreme properties, half of the isolates showed tolerance to 5% NaCl (w/v) and 48.8% isolates survived heat shock at 70°C. The identification of 12 multipotential bacteria based on 16S rRNA gene sequencing revealed that the bacteria belonged to Aneurinibacillus aneurinilyticus and Bacillus spp. Bacterization of tomato seeds showed that the hot spring bacteria promoted shoot height, fresh shoot weight, root length, and fresh root weight of tomato seedlings, with values ranging from 3.12% to 74.37%, 33.33% to 350.0%, 16.06% to 130.41%, and 36.36% to 318.18%, respectively, over the control. This research shows that multifunctional bacteria could be isolated from the hot springs. The outcome of this research may have a potential effect on crop production methodologies used in saline and arid environments.