Halobacterium Research Articles

Arsenite tolerance and removal potential of the indigenous halophilic bacterium, Halomonas elongata SEK2.

The indigenous halophilic arsenite-resistant bacterium Halomonas elongata strain SEK2 isolated from the high saline soil of Malek Mohammad hole, Lut Desert, Iran, could tolerate high concentrations of arsenate (As5+) and arsenite (As3+) up to 800 and 40 mM in the SW-10 agar medium, respectively. The isolated strain was able to tolerate considerable concentrations of other toxic heavy metals and oxyanions, including Cadmium (Cd2+), Chromate (Cr6+), lead (Pb2+), and selenite (Se4+), regarding the high salinity of the culture media (with a total salt concentration of 10% (w/v)), the tolerance potential of the isolate SEK2 was unprecedented. The bioremoval potential of the isolate SEK2 was examined through the Silver diethyldithiocarbamate (SDDC) method and demonstrated that the strain SEK2 could remove 60% of arsenite from arsenite-containing growth medium after 48 h of incubation without converting it to arsenate. The arsenite adsorption or uptake by the halophilic bacterium was investigated and substantiated through Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray (EDX) analyses. Furthermore, Transmission electron microscope (TEM) analysis revealed ultra-structural alterations in the presence of arsenite that could be attributed to intracellular accumulation of arsenite by the bacterial cell. Genome sequencing analysis revealed the presence of arsenite resistance as well as other heavy metals/oxyanion resistance genes in the genome of this bacterial strain. Therefore, Halomonas elongata strain SEK2 was identified as an arsenite-resistant halophilic bacterium for the first time that could be used for arsenite bioremediation in saline arsenite-polluted environments.

Isolation, Characterization and Identification of Halophilic bacteria from Solar saltern of Khambhat, Gujarat, India

The solar salterns of Khambhat, Gujarat are distinct biological niches distinguished by high salinity levels and harsh environmental circumstances. Our goal in this work was to isolate and characterise bacteria in order to investigate the diversity of microbes found in these saline soils. Standard microbiological procedures were used to isolate the bacteria from samples taken from various depths of the solar saltern ponds. To clarify their taxonomic identity and physiological characteristics, the isolated bacterial strains underwent morphological, biochemical and molecular characterization. Catalase, oxidase and fermentation assays are examples of biochemical studies that shed light on the isolated strains' metabolic capacities. Moreover, the phylogenetic relationships of the isolated bacteria were ascertained through molecular characterization using 16S rRNA gene sequencing. This work advances our knowledge of the microbial ecology of hypersaline environments and highlights the potential uses of bacteria isolated from these settings in biotechnology such as bioremediation, the synthesis of enzymes and the identification of new bioactive substances. To fully utilize these bacteria's biotechnological potential, more research into their functional properties is necessary.

Biodegradable bacterial polyester, poly (hydroxybutyrate-co-hydroxyvalerate) copolymer, produced by moderately halophile bacterium Halomonas sp. PR-1 isolated from marine environment

PHA (polyhydroxyalkanoate) production by halophiles has attracted much attention in recent years. It was certified that the halophile bacteria Halomonas sp. PR-1 isolated from saltern soil synthesised poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV) intracellularly from simple carbon substrate by means of FT-IR spectra analysis. The carbon and nitrogen source suitable for PHA production were selected as glucose and NH4Cl, respectively. The optimal ratio of glucose to NH4Cl was 20, when PHA content was 2.85 g/L and PHA yield was 50.85%. The optimal NaCl concentration for PHA biosynthesis was 30 g/L, when PHA yield was 63.3%. The halophile bacterium Halomonas sp. PR-1 was considered as a promising candidate for PHA production.

Sodium content in fermented shrimp paste with varying packaging materials

Shrimp and fish paste are fermented products with high amounts of added salt. Sodium (Na+ ) ions in salt are growth factors for halophilic lactic acid bacteria (LAB), essential in shrimp paste. However, an overabundance of Na+ negatively affects the human body and may increase blood pressure and the risk of heart attacks, strokes, kidney damage, and other health issues. Commercial shrimp paste can be found in various packaging materials. The permeability of the packaging material affects air availability during fermentation, which affects LAB growth and sodium levels. This study aimed to determine the effect different packaging materials have on rebon (Acetes sp.) shrimp paste sodium levels, precisely that of teak leaf, paper, and plastic. A completely randomized design and an experimental laboratory were used for the experiments. The data were analyzed using ANOVA and Honest Significant Differences tests. The different packaging materials significantly affected (P < 5%) the acidity, sodium levels, and total plate count (TPC) of LAB but did not affect the water activity or salt content. Shrimp paste consisted of 1.32±0.12% sodium when packaged in teak leaves, 1.51±0.08% in paper packaging, and 1.69±0.07% in plastic packaging. Teak leaves packaging resulted in shrimp paste with the lowest sodium content because of its many pores and high gas permeability, thus supporting the growth of microbes that use Na+ .

Deciphering the influence of salinity stress on the biological aniline degradation system: Pollutants degradation performance and microbial response

In order to evaluate the impact of salinity gradients on the aniline biodegradation system, six reactors at salinity concentrations (0%–5%) were established. The results presented the salinity except for 5% imposed negligible effects on aniline degradation performance. Nitrification had prominent resistance to salinity (0%–1.5%) while were significantly restrained when salinity increased. The total nitrogen (TN) removal efficiency of Z4 (1.5%) was 20.5% higher than Z1 (0%) during the stable operation phase. Moreover, high throughput sequencing analysis showed that halophilic bacterium, such as Halomonas, Rhodococcus, remained greater survival advantages in high salinity system. The substantial enrichment of Flavobacterium, Dokdonella, Paracoccus observed in Z4 ensured its excellent nitrogen removal performance. The close cooperation among dominant functional bacteria was strengthened when salt content was below 1.5% while exceeding 1.5% led to the collapse of metabolic capacity through integrating the toxicity of aniline and high osmotic pressure.

A non-classical crystallization mechanism of microbially-induced disordered dolomite

Non-classical crystallization pathways, involving the formation of complex precursors prior to nucleation, have been observed during the calcification process of invertebrate skeletons and shells. However, these pathways were rarely documented in microbially-induced carbonate precipitation. In this study, we presented experimental evidence demonstrating that a halophilic bacterium (Halomonas sp. strain JBHLT-1) catalyzed the biomineralization of disordered dolomite through an amorphous calcium-magnesium carbonate (ACMC) with a stoichiometry near that of dolomite. During the ACMC formation, strain JBHLT-1 significantly enhanced the incorporation of Mg2+ ions compared to abiotic ACMC that was synthesized without any microbial biomass. In the stage of ACMC crystallization, the presence of microbial biomass reduced the dissolution-reprecipitation rate and induced bias towards a solid-state reaction pathway. This observation was supported by the negligible loss of structural Mg2+ ions in the presence of cells of strain JBHLT-1. The microbially-induced growth of disordered dolomite appeared to follow a spherulitic growth mechanism, as evidenced by its hierarchical structure composed of coalesced nano-spheres, eventually growing into micron-sized spheroids and dumbbells with extended incubation times. Since disordered dolomite is considered as a crucial crystalline precursor of ordered sedimentary dolomite, the findings of this study have important implications for understanding the formation mechanism of natural dolomite.

Left knee septic monoarthritis in a pediatric patient due to shewanella putrefaciens: case report and literature review

BackgroundShewanella putrefaciens is a gram-negative, nonfermenting, oxidase-positive, hydrogen sulfide-producing bacillus and a halophilic bacterium, known for causing unusual infections in humans and often regarded as an opportunistic pathogen. Its diverse symptoms have a significant impact on human health, with 260 documented disorders reported in the literature over the last 40 years, highlighting its potential danger.Case presentationWe present the case of a previously healthy 15-year-old male patient who sustained a self-inflicted sharp-object injury while working in the field, resulting in secondary septic monoarthritis due to Shewanella putrefaciens.ConclusionsThis case highlights the bacteriological and clinical characteristics, as well as the antibiogram, of Shewanella spp. Given the recent increase in notifications of Shewanella infections, predominantly by S. algae and S. putrefaciens, it is essential to consider these pathogens in patients with a history of contact with bodies of water. Special attention must be paid to their resistance patterns in patient management to prevent the development of intrinsic antimicrobial resistance.

Cloning and expression of Rubisco Like Protein (RLP) from halophilic bacterium Chromohalobacter salexigens BKL 5

Cloning and expression of Rubisco Like Protein (RLP) from halophilic bacterium Chromohalobacter salexigens BKL 5

Living emission abolish filters (LEAFs) for methane mitigation: design and operation

As one of the most potent greenhouse gases, methane is a critical target for the near-term mitigation of global warming. Efficient, scalable, easy-to-implement, and robust mitigation technologies are urgently needed to assist in reaching methane abolishment. The goal of this research was to test the applicability of active, extremophilic methanotrophic cells as a baseline concept for engineered systems aiming at methane capturing. The system, named living emission abolish filters (LEAFs), represents an array of immobilized biomaterials capable of capturing methane directly from vent streams. The biomaterials were made using cells of Methylotuvimicrobium alcaliphilum 20ZR, a robust halophilic methanotrophic bacterium with the ability to consume methane gas at low concentrations. Several critical parameters were tested, including (i) the composition of the matrix and optimal immobilization to increase catalyst load, (ii) the stability of methanotrophic cells, and (iii) the toxicity of trace gases (i.e. CO). We found that hydrogels coated with 2.3 mg cell dry weight/cm3 methanotrophic cells represent the best-performing biomaterials. The methane reduction potential of LEAFs fluctuated from 20% to 95% and depended on the methane concentration in the gas stream and the stream flow rates. The potential for commercial-scale deployment and emissions reductions was also evaluated. Total greenhouse gas emissions (combined using the global warming potential GWP100) from an example using a ventilation air methane source over a one-year period was shown to be reduced in two LEAF scenarios by 51% and 75%. Over longer time horizons, more significant reductions are possible as consistent methane consumption can be sustained. The study highlights the overall potential of the liquid-free bio-based composite methane mitigation system. Further improvements essential for system assembly and implementations should include (a) optimization of the cell immobilization protocols to improve cell load and the shelf-life of the system and (b) implementation of matrix moldings for cell immobilization to achieve optimal gas flow and increase the cell-gas interface.

Metagenomic profiling of halites from the Atacama Desert: an extreme environment with natural perchlorate does not promote high diversity of perchlorate reducing microorganisms.

We surveyed the presence of perchlorate-reducing microorganisms in available metagenomic data of halite environments from the Atacama Desert, an extreme environment characterized by high perchlorate concentrations, intense ultraviolet radiation, saline and oxidizing soils, and severe desiccation. While the presence of perchlorate might suggest a broad community of perchlorate reducers or a high abundance of a dominant taxa, our search reveals a scarce presence. In fact, we identified only one halophilic species, Salinibacter sp003022435, carrying the pcrA and pcrC genes, represented in low abundance. Moreover, we also discovered some napA genes and organisms carrying the nitrate reductase nasB gene, which hints at the possibility of cryptic perchlorate reduction occurring in these ecosystems. Our findings contribute with the knowledge of perchlorate reduction metabolism potentially occurring in halites from Atacama Desert and point towards promising future research into the perchlorate-reducing mechanism in Salinibacter, a common halophilic bacterium found in hypersaline ecosystems, whose metabolic potential remains largely unknown.

Removal of cadmium through biomineralization using halophilic and ureolytic bacteria under saline conditions

Heavy metal pollution poses an immense challenge to humanity owing to its severe toxic effects on living beings. This study investigates the bioremediation potential of the urease-hydrolyzing and halophilic bacterium Bacillus paramycoides- MSR1 to reduce the toxicity of cadmium (Cd) in the environment under salt stress through microbially induced calcium carbonate precipitation (MICCP). The enzymatic activity of urease and calcium carbonate (CaCO3) precipitation was studied under different concentrations of salt stress (0%, 3.5%, 5%, 7.5%, 10%, 15%) and maximum urease activity of 735.7 U/ml was recorded at 5% salt stress. The urease activity and CaCO3 precipitation decreased with increasing Cd toxicity (0, 10, 20, 30, 40, 50, and 60 μM). The maximum concentration of Cd endured by bacteria was determined by IC50 value and the minimum inhibitory concentration of Cd was recorded as 9.86 μM under 5% stress. Atomic absorption spectroscopy results revealed that Cd removal was as high as 90.3% under 5% salt stress. Microstructural analysis through FE-SEM revealed the surface topography of carbonate crystals as rhombohedral, whereas EDS confirmed the presence of CaCO3 and Cd in the bio-precipitates. These results suggest that MICCP is a potential, environmentally safe, low-cost technique and an excellent alternative to conventional heavy metal removal strategies from the environment.

Production and Optimization of Extracellular α-amylase From Halophilic Bacteria Cytobacillus oceanisediminis Isolated From Wadi-El-Natrun, Egypt

The current study aimed to maximize α-amylase enzyme production by halophilic bacteria Cytobacillus oceanisediminis isolated from soil of Wadi-El-Natrun, Egypt. The results showed that of 21 halophilic bacterial isolates recovered from saline soil samples, eight isolates were high amylase producers. Interestingly, the bacterial isolate AHB6 exhibited the highest extracellular amylase production and was selected for further studies. This isolate was molecularly identified based on the 16srRNA gene sequencing as Cytobacillus oceanisediminis and has the accession number OM759999. The optimum temperature for α-amylase enzyme was 45 °C and exhibited thermostability at 45 °C for 1 h and retained more than 80% of its original activity. The α-amylase enzyme was active in almost all tested pHs and reached its highest activity at pH 9. Also, the optimum culture conditions for α-amylase enzyme production were wheat bran as carbon source, 2 g/l K2HPO4 as potassium source, 6 g/l MgSO4 as magnesium source and 0.5 g/l KNO3 as nitrogen source. These findings suggest the applicability of bacterial isolate Cytobacillus oceanisediminis as a potent producer of α-amylase for industrial purposes. Keywords: Amylase; Optimization; Cytobacillus oceanisediminis; Starch hydrolysis; Thermo-halophilic bacteria.

Halophilic Plant Growth-Promoting Rhizobacteria as Producers of Antifungal Metabolites under Salt Stress

Salinity is one of the main factors causing soil deterioration, making it unsuitable for agriculture. It is well documented that the application of halotolerant and halophilic plant growth-promoting bacteria (PGPR: plant growth-promoting rhizobacteria) with biological control activities as an inoculant of cultivated plants offers a biological alternative to the use of agrochemicals, particularly when subjected to salt stress. From this perspective, 70 bacterial strains were isolated from saline soils (sebkha) in arid and semi-arid areas of Eastern Algeria. Three isolates were selected based on their ability to produce bioactive molecules allowing them to promote plant growth, such as hydrolytic enzymes, indole acetic acid (auxin-phytohormone), HCN, NH3, etc. Two of these isolates belonged to the genus Serratia and the third was a halophilic Halomonas bacteria. These bacteria were identified based on their 16S rDNA sequences. Antagonism tests against phytopathogenic fungi were carried out. The identification of the antifungal molecules produced by these bacteria was determined using high-performance liquid chromatography. These bacteria can inhibit mycelial development against phytopathogenic fungi with rates reaching 80.67% against Botrytis cinerea, 76.22% against Aspergillus niger, and 66.67% against Fusarium culmorum for Serratia sp. The strain Halomonas sp. inhibited mycelial growth through the production of volatile substances of Aspergillus niger at 71.29%, Aspergillus flavus at 75.49%, and Penicillium glabrum at a rate of 72.22%. The identification of the antifungal molecules produced by these three bacteria using HPLC revealed that they were polyphenols, which makes these strains the first rhizobacteria capable of producing phenolic compounds. Finally, pot tests to determine the effectiveness of these strains in promoting wheat growth under salinity stress (125 mM, 150 mM, and 200 mM) was carried out. The results revealed that a consortium of two isolates (Serratia sp. and Halomonas sp.) performed best at 125 mM. However, at higher concentrations, it was the halophilic bacteria Halomonas sp. that gave the best result. In all cases, there was a significant improvement in the growth of wheat seedlings inoculated with the bacteria compared to non-inoculated controls.

Characterization of anthranilic acid produced by Virgibacillus salarius MML1918 and its bio-imaging application.

Anthranilic acid (AA) holds significant importance in the chemical industry. It serves as a crucial building block for the amino acid tryptophan by manipulating the tryptophan biosynthesis pathway, it is possible to increase the production of anthranilic acid. In this study, we utilized metabolic engineering approaches to produce anthranilic acid from the halophilic bacterium Virgibacillus salarius MML1918. The halophilic bacteria were grown in an optimized production medium, and mass production of secondary metabolites was made in ATCC medium 1097 Proteose peptone-for halophilic bacteria and subjected to column chromatography followed by sub-column chromatography the single band for the purified compound was confirmed. Further, various spectral analyses were made for the partially purified compounds, and fluorescence microscopy for fungal cell observation was performed. The purified compound was confirmed by single crystal X-ray diffraction (XRD) analysis, and it was identified as 2-amino benzoic acid. The Fourier transform infrared Spectroscopy (FT-IR) spectrum and nuclear magnetic resonance (NMR) spectrum also confirm the structural characteristic of 2-amino benzoic acid. The UV-Vis absorption spectrum of AA shows the maximum absorption at 337.86nm. The emission spectrum of 2-amino benzoic acid showed the maximum emission at 453nm. The bio-imaging application of 2-amino benzoic acid was examined with fungal mycelium of Rhizoctonia solani. It was effectively bound and emitted the blue color at the concentration of 200 and 300µg/mL. The halophilic bacterium (V. salarius), may have unique metabolic pathways and requirements compared to non-halophilic organisms, to produce AA effectively. This could have implications for industrial biotechnology, particularly in manufacturing environments where high salt concentrations are present and also it can be used as bio-imaging agent.

Bioremediation of Saline Soils with the Consortium of Halophilic Bacteria

88 strains of bacteria were isolated and purified from the naturally saline soils of Kumisi, Sagarejo and Alazani valley (Eastern Georgia). Based on the initial identification all strains belong to the genus Bacillus. Two strains – Bacillus spp. 8(3)1) and Bacillus spp. 7(5)4, resistant to chloride, sulfate and mixed (chloride-sulfate) salinity, as well as possessing high cellulase and amylase activities were selected as a result of successive screenings among the isolated bacteria. After the antagonism between potential members of the consortium has been excluded, the consortium of halophilic bacteria was created. Compost was made and applied to moderately saline soils using the halophilic consortium. The bioremediation of saline soils of Alazani was especially successful: the halophilic consortium has reduced the salt content in the soil by 41% during the 21 days of composting.

Chelativorans salis sp. nov., a slightly halophilic bacterium isolated from an enrichment system with saline lake sediment.

A Gram-stain-negative, non-motile, and slightly halophilic alphaproteobacterium, designated strain EGI FJ00035T, was isolated from enrichment sediment samples of a saline lake in Xinjiang Uygur Autonomous Region, PR China. The taxonomic position of the isolate was determined using the polyphasic taxonomic and phylogenomic analyses. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain EGI FJ00035T formed a distinct clade with 'Chelativorans alearense' UJN715 and 'Chelativorans xinjiangense' lm93 with sequence similarities of 98.44 and 98.22 %, respectively, while sharing less than 96.7 % with other valid type strains. The novel isolate could be distinguished from other species of the genus Chelativorans by its distinct phenotypic, physiological, and genotypic characteristics. Optimal growth of strain EGI FJ00035T occurred on marine agar 2216 at pH 7.0 and 30 °C. The major respiratory quinone was Q-10, while the major fatty acids (>5 %) were C19 : 0 cyclo ω8c, summed feature 8 (C17 : 1 ω6c and/or C17 : 1 ω7c), C16 : 0, C18 : 0, and iso-C17 : 0. The detected polar lipids included diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, unidentified aminophospholipids, unidentified glycolipids, and an unidentified lipid. Based on its genome sequence, the G+C content of strain EGI FJ00035T was 63.2 mol%. The average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization values of strain EGI FJ00035T against related members of the genus Chelativorans were below the thresholds for delineation of a novel species. According our polyphasic taxonomic data, strain EGI FJ00035T represents a new species of the genus Chelativorans, for which the name Chelativorans salis sp. nov. is proposed. The type strain of the proposed novel isolate is EGI FJ00035T (=KCTC 92251T=CGMCC 1.19480T).

Influence of the surface modification of BaTiO3 nanoparticles by Polyhydroxybutyrate obtained from halophiles bacteria on the optical response intensity of the second harmonic

Influence of the surface modification of BaTiO3 nanoparticles by Polyhydroxybutyrate obtained from halophiles bacteria on the optical response intensity of the second harmonic

Expression of Concern: Virgibacillus senegalensis sp. nov., a new moderately halophilic bacterium isolated from human gut

Expression of Concern: Virgibacillus senegalensis sp. nov., a new moderately halophilic bacterium isolated from human gut

Expression of Concern: Virgibacillus ndiopensis sp. nov., a new halophilic bacterium isolated from the stool of a healthy 11-year-old boy

Expression of Concern: Virgibacillus ndiopensis sp. nov., a new halophilic bacterium isolated from the stool of a healthy 11-year-old boy

Succession of bacterial and fungal communities during the mud solarization of salt-making processing in a 1000-year-old marine solar saltern

A 1000-year-old marine solar saltern in Hainan Island, South China, is in the continuation of traditional skills involving mud soak and solarization for three days to accumulate salt, which is a unique process contributing to the selection of highly halophilic microbes related to salt quality and flavor. Herein, the successions of physicochemical properties and bacterial and fungal communities of muds from the saltern were investigated during the processing of mud solarization. The results showed that Na+, Cl−, Mg2+ and total nitrogen were the main factors in explaining the fluctuation of the fungal community, whereas the bacterial community was predominantly determined by Ca2+, total kalium and total phosphorus. During three days of mud solarization, the soil bacterial alpha diversity in the saltern was significantly lower than that of the surroundings, whereas the fungal alpha diversity showed an opposite trend. The bacterial functional groups with the same survival and adaptation strategies remained relatively stable, while the dominant functional type in fungi changed from monotropic to complex trophic mode. Additionally, some unidentified fungi species were increasingly found in mud. The abundances of Saitozyma, Solicoccozyma and Wallemia (Basidiomycota) increased and may contribute to the salt flavor through decomposing cellulose molecules into glucose due to their higher β-glucosidase activity, while the harmful fungal genera including Inocybe and Paraconiothyrium decreased obviously due to the stresses of salinity and solar exposure. These results showed that the traditional salt-making skills associated with mud solarization have selected a high abundance of beneficial halophilic microbes to increase the salt quality and flavor. Our findings not only reveal the underlying mechanisms for the long-history salt-making skills of this 1000-year-old unusual cultural heritage but also are highly valuable for bioprospecting to develop novel halophilic bacteria and fungi for modern chemistry industries.