Bacillus Halotolerans Research Articles

Insights into Endophytic and Rhizospheric Bacteria of Five Sugar Beet Hybrids in Terms of Their Diversity, Plant-Growth Promoting, and Biocontrol Properties

Sugar beet is the most important crop for sugar production in temperate zones. The plant microbiome is considered an important factor in crop productivity and health. Here, we investigated the bacterial diversity of seeds, roots, and rhizosphere of five sugar beet hybrids named Eduarda (ED), Koala (KO), Tibor (T), Tajfun (TF), and Cercospora-resistant (C). A culture-independent next-generation sequencing approach was used for the further investigation of seed-borne endophytes. Hybrid-associated bacteria were evaluated for their plant growth–promoting (PGP) characteristics, antagonistic activity towards Cercospora beticola and several Fusarium strains in dual culture assays, and drought and salinity tolerance. High-throughput sequencing revealed that the Proteobacteria phylum was most dominant in the seeds of all hybrids, followed by Cyanobacteria and Actinobacteriota. The predominant genus in all hybrids was Pantoea, followed by Pseudomonas, Acinetobacter, Chalicogloea, Corynebacterium, Enterobacter, Enterococcus, Glutamicibacter, Kosakonia, and Marinilactibacillus. Unique genera in the hybrids were Pleurocapsa and Arthrobacter (T), Klebsiella (TF), Apibacter (ED), and Alloscardovia (KO). The genera that were most represented in one hybrid were Weissella and Staphylococcus (TF); Streptococcus (T); Gardnerella, Prevotella, and Rothia (KO); and Gilliamella, Lactobacillus, and Snodgrassella (ED). Thirty-two bacteria out of 156 isolates from the rhizosphere, roots, and seeds were selected with respect to various plant growth–promoting activities in vitro, i.e., nitrogen fixation, phosphate solubilization, siderophore production, indole-3-acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase activity, hydrogen cyanide production, exoenzymatic activity (amylase, protease, lipase, cellulase, xylanase, mannanases, gelatinase, and pectinase), mitigation of environmental stresses, and antifungal activity. Mixta theicola KO3-44, Providencia vermicola ED3-10, Curtobacterium pusillum ED2-6, and Bacillus subtilis KO3-18 had the highest potential to promote plant growth due to their multiple abilities (nitrogen fixation, phosphate solubilization, production of siderophores, and IAA). The best antagonistic activity towards phytopathogenic fungi was found for Bacillus velezensis C3-19, Paenibacillus polymyxa C3-36 and Bacillus halotolerans C3-16/2.1. Only four isolates B. velezensis T2-23, B. subtilis T3-4, B. velezensis ED2-2, and Bacillus halotolerans C3-16/2.1 all showed enzymatic activity, with the exception of xylanase production. B. halotolerans C3-16/2.1 exhibited the greatest tolerance to salinity, while two B. subtilis strains (C3-62 and TF2-1) grew successfully at the maximum concentration of PEG. The current study demonstrates that sugar beet–associated bacteria have a wide range of beneficial traits and are therefore highly promising for the formulation of biological control and PGP agents.

Production and characterization of exopolysaccharide (EPS) from marine Bacillus halotolerans and its antibacterial activity against clinical pathogens

Production and characterization of exopolysaccharide (EPS) from marine Bacillus halotolerans and its antibacterial activity against clinical pathogens

Insights into Genomic Features and Potential Biotechnological Applications of Bacillus halotolerans Strain HGR5.

Algeria is one of the wealthiest countries in terms of hydrothermal sources, with more than two hundred hot springs. However, diverse and little-described microbial communities colonize these habitats, making them an intriguing research subject. This work reports the isolation of bacteria from two hot springs water samples in northeastern Algeria, evaluating their enzymatic activities and effect on plant pathogens. Out of the obtained 72 bacterial isolates and based on the 16S rRNA gene sequence analysis, the strain HGR5 belonging to Bacillus halotolerans had the most interesting activity profile. Interestingly, HGR5 was substantially active against Fusarium graminearum, Phytophthora infestans, and Alternaria alternata. Furthermore, this strain presented a high ability to degrade casein, Tween 80, starch, chitin, cellulose, and xylan. The genome sequence of HGR5 allowed taxonomic validation and screening of specific genetic traits, determining its antagonistic and enzymatic activities. Genome mining revealed that strain HGR5 encloses several secondary metabolite biosynthetic gene clusters (SM-BGCs) involved in metabolite production with antimicrobial properties. Thus, antimicrobial metabolites included bacillaene, fengycin, laterocidine, bacilysin, subtilosin, bacillibactin, surfactin, myxovirescin, dumulmycin, and elansolid A1. HGR5 strain genome was also mined for CAZymes associated with antifungal activity. Finally, the HGR5 strain exhibited the capacity to degrade polycaprolactone (PCL), a model substrate for polyester biodegradation. Overall, these results suggest that this strain may be a promising novel biocontrol agent with interesting plastic-degradation capability, opening the possibilities of its use in various biotechnological applications.

Differences of airborne and mural microorganisms in a 1,500-year-old Xu Xianxiu's Tomb, Taiyuan, China.

Microbial colonization represents one of the main threats to the conservation of subterranean cultural heritage sites. Recently, the microbial colonization on murals in tombs has gradually attracted attention. In this study, a total of 33 samples, including 27 aerosol samples and 6 mural painting samples, were collected from different sites of Xu Xianxiu's Tomb and analyzed using culture-dependent methods. We compared the diversities of culturable bacteria and fungi isolated from the air and murals and explored the potential impacts of microorganisms on the biodeterioration of the murals. Phylogenetic analyses revealed that the culturable bacteria belonged to Bacillus, Microbacterium, Lysobacter and Arthrobacter. And the most of fungal belonged to the Penicillium, Cladosporium and Aspergillus genera. The composition and structure of airborne bacteria and fungi outside the tomb were both significantly different from that inside the tomb. The variation trends of airborne bacterial and fungal concentrations at different sampling sites were remarkably similar. Bacillus frigoritolerans, Bacillus halotolerans, Bacillus safensis, Exiguobacterium mexicanum, Microbacterium trichothecenolyticum, and Micrococcus yunnanensis were bacterial species commonly isolated from both the mural and air environments. Fungal species commonly isolated from aerosol samples and mural painting samples were Alternaria alternata, Cladosporium cladosporioides, Penicillium brevicompactum, and Peyronellaea glomerata. The prediction of the ecological functions of the bacteria revealed that chemoheterotrophy or aerobic_chemoheterotrophy accounted for substantial relative proportions in all sample types. These results suggest that the aerosol circulation between the inside and outside environments of the tomb was weak and that the outside environment had yet to have an impact on the air microbial community inside the tomb. Selective colonization of microorganisms, which is mediated by interaction between microorganisms and special microenvironmental factors, is an important reason for the biodeterioration of murals.

Microbial and physico-chemical dynamics associated with chicken feather compost preparation vis-à-vis its impact on the growth performance of tomato crop

The study aimed to assess the effectiveness of five potent keratinolytic bacterial strains, including Bacillus halotolerans L2EN1, B. cereus N27, B. cereus N14, B. megaterium N35, and B. halotolerans DPE11, in the preparation of chicken feather compost (CFC) using chicken feathers (CF) and cow dung (CD) as substrates. The experiment that involved two setups (Set-I, with a keratinolytic bacterial consortium, and Set-II, without consortium) and five treatment combinations (T1 - CF only; T2 - 3CF:1CD; T3 - 1CF:1CD; T4 - 1CF:3CD; T5 - CD only) was conducted in both plastic pots and composting pits for six months. Microbiological and physico-chemical analyses of CFC conducted monthly revealed that treatment T4 in Set-I demonstrated the most favorable microbiological (bacteria: 9.40 Log CFU/g; fungi: 4.20 Log CFU/g; actinomycetes: 3.49 Log CFU/g; enteric: 7.62 Log CFU/g; spore-formers: 4.96 Log CFU/g; diazotrophs: 6.38 Log CFU/g; proteolytic bacteria: 7.98 Log CFU/g) and physico-chemical (pH: 7.53; temperature: 34.79 °C; EC: 0.87 mmhos/cm; moisture: 45.10%; non-volatiles: 21.25%; volatiles: 78.75%; organic carbon: 45.68%; N: 7.02%; P: 0.68%; K: 2.06%; C:N ratio: 15.70) characteristics. Subsequent efficacy testing of varying proportions (%) of T4 (T1 – 5.0, T2 – 10.0, T3 – 15.0, T4 – 20.0) on tomatoes, demonstrated significantly superior growth performance than the control (without CFC). Hence, application of CFC @ 10% may be recommended as an excellent organic fertilizer for tomatoes. In conclusion, co-composting CF (1 part) with CD (3 parts) employing keratinolytic bacteria offers an eco-friendly approach for repurposing CF waste into a nitrogen-rich organic fertilizer.

Culturable Diversity and Biological Properties of Bacterial Endophytes Associated with the Medicinal Plants of Vernonia anthelmintica (L.) Willd

As one of the important traditional medicinal plants listed in the Chinese pharmacopoeia, Vernonia anthelmintica (L.) Willd has been shown to possess various biological activities. In this study, we characterized culturable endophytic bacteria associated with the medicinal plant V. anthelmintica collected from Hotan within the Xinjiang autonomous region of China. Bacterial endophytes were identified via 16S rRNA gene sequence analysis and compared to similar sequences from the GenBank. Isolated strains exhibited 99.08–100% similarity to Bacillus haynesii XJB-5, Bacillus proteolyticus XJB-16, Bacillus halotolerans XJB-35, Bacillus safensis XJB-71, Pseudomonas punonensis XJB-7, Lysinibacillus fusiformis XJB-17, Streptococcus lutetiensis XJB-66, Leclercia adecarboxylata XJB-12, Paenibacillus alvei XJB-14, and Pantoea agglomerans XJB-62. The ethyl acetate extracts of the bacterial endophytes demonstrated various pharmacological properties, such as antimicrobial, cytotoxic, antidiabetic, and antioxidant activity, according to a melanin content assay and have shown tyrosinase activity in murine B16 cells. A crude extract of B. halotolerans XJB-35 displayed more powerful biological activities than other bacterial endophytes; therefore, this strain was studied further in order to select the optimized parameters for enhancing the synthesis of bioactive compounds. The optimal culture medium was found to be nutrient broth (NB) medium, using peptone as its carbon source and yeast extract as its nitrogen source. A 24 h incubation time produced the optimal conditions for the maximum growth of B. halotolerans XJB-35 and the production of bioactive compounds. Moreover, we investigated the volatile chemical component of the dichloromethane fraction using GC-MS analysis. Our findings provide valuable information regarding the synthesize of bioactive natural products by B. halotolerans XJB-35 for use by the medicinal and pharmaceutical industries.

Whole-genome analysis of the benzoic acid-degrading bacterium Bacillus halotolerans B28 to reveal its phytoprobiotic effects

Benzoic acid is a representative allelochemical in soils affected by continuous cropping obstacles, and it is also a typical aromatic pollutant, causing a direct or indirect inhibition on crop growth. In this study, a strain B28 that was isolated from the rhizosphere of peanut by using benzoic acid as the sole carbon source and sequenced. Strain B28 contained a single circular chromosome, the complete genome size was 4,132,583 bp, the average GC was 43.89%, with 3928 predicted genes, and based on phylogenomic analyses, B28 was designated as Bacillus halotolerans. The strain B28 with outstanding abilities to biodegrade benzoic acid, enhance plant growth and control soil-borne diseases, which were the key to the phytoprobiotic functions. Genome mining revealed the potential genomic properties associated with plant growth promotion, such as aromatic xenobiotics biodegradation, IAA synthesis, biofilm formation, chemotaxis motility and secondary metabolite synthesis. The effects of strain B28 on the growth of Arachis hypogaea L. (peanut) was evaluated, and the physiological parameters of peanut such as fresh weight, dry weight, plant height and root length were significantly higher after inoculating strain B28. Overall, our present results indicate that Bacillus halotolerans B28 is a potential PGPR strain for benzoic acid bioremediation and organic agriculture application.

Screening of xylanase producing Bacillus species and optimization of xylanase process parameters in submerged fermentation

One of the main process inputs in the microbial enzyme, an environment friendly and an extraordinary catalyst, production is characteristics of the microorganism. This study aimed to screen newly isolated Bacillus species for the xylanase production potentiality and investigate crucial parameters that affect the xylanase producing process. Bacteria samples were isolated from potential agricultural and food sources such as soil, wheat bran, and sourdough. Eight xylanase producing isolates showed 99% homology to Bacillus species according to 16S rRNA sequence analysis. Isolate A67 has been found the best xylanase producer isolate and identified as Bacillus halotolerans DSM 8802. Incubation temperature, initial medium pH, and agitation speed parameters were optimized by RSM in the shake flask scale. The optimum xylanase production points were found as 30 °C, pH 8, and 127.27 rpm under submerged fermentation conditions. Xylanase activity was obtained experimentally as 23.47 U/mL resulting 4.21-fold increase with the statistical optimization. R2 and predicted R2 values that reflects the significance of the designed model were calculated as 0.9964 and 0.9674, respectively. Incubation temperature has been concluded as the most important parameter that affects the xylanase activity for isolate A67. As it has low incubation temperature demand, metabolizes xylan polymer as a carbon source and most of the Bacillus species do not produce any toxin, isolate A67 could have potential for the usage of the lignocellulosic biomass added media to make fermentation cost effective in food-grade xylanase production process.

Compatible Consortium of Endophytic Bacillus halotolerans Strains Cal.l.30 and Cal.f.4 Promotes Plant Growth and Induces Systemic Resistance against Botrytis cinerea.

Evaluating microbial-based alternatives to conventional fungicides and biofertilizers enables us to gain a deeper understanding of the biocontrol and plant growth-promoting activities. Two genetically distinct Bacillus halotolerans strains (Cal.l.30, Cal.f.4) were evaluated for the levels of their compatibility. They were applied individually or in combination under in vitro and greenhouse conditions, using seed bio-priming and soil drenching as inoculum delivery systems, for their plant growth-promoting effect. Our data indicate that application of Cal.l.30 and Cal.f.4 as single strains and as a mixture significantly enhanced growth parameters of Arabidopsis and tomato plants. We investigated whether seed and an additional soil treatment with these strains could induce the expression of defense-related genes in leaves of young tomato seedling plants. These treatments mediated a long lasting, bacterial-mediated, systemic-induced resistance as evidenced by the high levels of expression of RP3, ACO1 and ERF1 genes in the leaves of young tomato seedlings. Furthermore, we presented data showing that seed and soil treatment with B. halotolerans strains resulted in an effective inhibition of Botrytis cinerea attack and development on tomato leaves. Our findings highlighted the potential of B. halotolerans strains as they combine both direct antifungal activity against plant pathogens and the ability to prime plant innate immunity and enhance plant growth.

Optimization of amylase production by the biological control agent Bacillus halotolerans RFP74 using response surface methodology

BackgroundOver the years, excessive use of chemical pesticides to control plant pathogens has caused environmental problems. Therefore, biological solutions such as the use of microorganisms with antimicrobial capacity become indispensable. To inhibit the growth of plant pathogens, biological control agents use different mechanisms, including the production of hydrolytic enzymes. In this study, the production of amylase, an enzyme important for the prevention and control of plant diseases, by a biological control agent Bacillus halotolerans RFP74 was optimized using response surface methodology. ResultsBacillus halotolerans RFP74 inhibited the growth of various phytopathogens including Alternaria and Bipolaris with an inhibition rate of more than 60%. In addition, it also demonstrated an essential production of amylase. Based on previous studies of amylase production in Bacillus, three parameters were considered significant: initial pH of the medium, incubation time, and temperature. Using the central composite design with Design Expert software, the optimized amylase production for B.halotolerans RFP74 is at a temperature of 37 °C, incubation time 51 h and pH 6. ConclusionThe biological control agent B.halotolerans RFP74 inhibited the growth of Alternaria and Bipolaris, demonstrating its broad spectrum of activity. Knowledge of the optimal condition required for the production of hydrolytic enzymes such as amylase provides information on the most effective application of this biological control agent.

Isolation and Identification of Salt-Tolerant Mangrove Endophyte from Red Sea Coast Jeddah, Saudi Arabia

The aim of the study was to isolate and identify the most salt-tolerant endophytic bacteria from the mangrove plants (Avicennia marina) from the Red Sea Jeddah coastal region. In total, 21 endophytic bacteria were isolated from various parts of Avicennia marina cultured under various salt concentrations in laboratory conditions. Out of 21 endophytes, one isolate was selected based on its salt tolerance capacity, the isolate was identified as Bacillus halotolerans using 16S rRNA sequencing. The nucleotide sequence has been deposited under accession number MT858957. Bacillus halotolerans ymk 021 grows under high salinity and temperature. In response to high salinity stress (550 mM) mung bean (Vigna radiata L.) treated with B. halotolerans ymk021 showed significant results in morphological characteristics like fresh root and shoot weight, dry root and shoot weight, and root and shoot length. The ability of this salt-tolerant bacterial endophyte to produce antioxidants in plant may also resolve the major issue of oxidative damage during salinity stress. It may produce antibiotics, essential industrial enzymes too.

Production of biosurfactant by salt-resistant Bacillus in lead-supplemented media: application and toxicity.

A group of biosurfactants are lipopeptides that are produced by some microorganisms, especially Bacillus strains. They are new bioactive agents with anticancer, antibacterial, antifungal, and antiviral activities. Also, they are used in sanitation industries. In this study, a lead-resistant strain of Bacillus halotolerans was isolated for lipopeptide production. This isolate exhibited metal resistance (lead, calcium, chromium, nickel, copper, manganese, and mercury), salt tolerance (12%), and antimicrobial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Saccharomyces cerevisiae. The production of lipopeptide was optimized, concentrated, and then extracted from the polyacrylamide gel in a simple way for the first time. The nature of the purified lipopeptide was determined by FTIR, GC/MS, and HPLC analyses. The purified lipopeptide indicated significant antioxidant properties (90.38% at a concentration of 0.8mgml-1). Also, it had anticancer activity by apoptosis (flow cytometry analysis) in MCF-7 cells, while it had no cytotoxicity on HEK-293 normal cells. Therefore, Bacillus halotolerans lipopeptide has the potential to be used as an antioxidant, antimicrobial, or anticancer agent in the medical and food industries.

Antagonistic Strain Bacillus halotolerans Jk-25 Mediates the Biocontrol of Wheat Common Root Rot Caused by Bipolaris sorokiniana

Common root rot caused by Bipolaris sorokiniana infestation in wheat is one of the main reasons for yield reduction in wheat crops worldwide. The bacterium strain JK-25 used in the current investigation was isolated from wheat rhizosphere soil and was later identified as Bacillus halotolerans based on its morphological, physiological, biochemical, and molecular properties. The strain showed significant antagonism to B. sorokiniana, Fusarium oxysporum, Fusarium graminearum, and Rhizoctonia zeae. Inhibition of B. sorokiniana mycelial dry weight and spore germination rate by JK-25 fermentation supernatant reached 60% and 88%, respectively. The crude extract of JK-25 was found, by Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), to contain the surfactin that exerted an inhibitory effect on B. sorokiniana. The disruption of mycelial cell membranes was observed under laser scanning confocal microscope (LSCM) after treatment of B. sorokiniana mycelium with the crude extract. The antioxidant enzyme activity of B. sorokiniana was significantly reduced and the oxidation product malondialdehyde (MDA) content increased after treatment with the crude extract. The incidence of root rot was significantly reduced in pot experiments with the addition of JK-25 culture fermentation supernatant, which had a significant biological control effect of 72.06%. Its ability to produce siderophores may help to promote wheat growth and the production of proteases and pectinases may also be part of the strain's role in suppressing pathogens. These results demonstrate the excellent antagonistic effect of JK-25 against B. sorokiniana and suggest that this strain has great potential as a resource for biological control of wheat root rot strains.

Co-Culture of Halotolerant Bacteria to Produce Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Using Sewage Wastewater Substrate.

The focus of the current study was the use of sewage wastewater to obtain PHA from a co-culture to produce a sustainable polymer. Two halotolerant bacteria, Bacillus halotolerans 14SM (MZ801771) and Bacillus aryabhattai WK31 (MT453992), were grown in a consortium to produce PHA. Sewage wastewater (SWW) was used to produce PHA, and glucose was used as a reference substrate to compare the growth and PHA production parameters. Both bacterial strains produced PHA in monoculture, but a copolymer was obtained when the co-cultures were used. The co-culture accumulated a maximum of 54% after 24 h of incubation in 10% SWW. The intracellular granules indicated the presence of nucleation sites for granule initiation. The average granule size was recorded to be 231 nm; micrographs also indicated the presence of extracellular polymers and granule-associated proteins. Fourier transform infrared spectroscopy (FTIR) analysis of the polymer produced by the consortium showed a significant peak at 1731 cm-1, representing the C=O group. FTIR also presented peaks in the region of 2800 cm-1 to 2900 cm-1, indicating C-C stretching. Proton nuclear magnetic resonance (1HNMR) of the pure polymer indicated chemical shifts resulting from the proton of hydroxy valerate and hydroxybutyrate, confirming the production of poly(3-hydroxybutyrate-co-3-hydroxy valerate) (P3HBV). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay showed that the copolymer was biocompatible, even at a high concentration of 5000 µg mL-1. The results of this study show that bacterial strains WK31 and 14SM can be used to synthesize a copolymer of butyrate and valerate using the volatile fatty acids present in the SWW, such as propionic acid or pentanoic acid. P3HBV can also be used to provide an extracellular matrix for cell-line growth without causing any cytotoxic effects.

Optimization of Biosurfactant Production using Chrysene Degrading Bacteria Isolated from Marine Water

Biosurfactants were found to be a suitable candidate for environment clean-up and as an alternative to conventional treatment systems. In the present study, a polyaromatic hydrocarbon degrading organism Bacillus halotolerans was screened for its ability to produce biosurfactant during hydrocarbon degradation. The bio-surfactant activity of the organism was screened by using various methods like oil spreading technique, emulsification assay, foam height analysis and parafilm-M test. The design expert software was used to optimize the suitable conditions for the production of biosurfactants. The optimum conditions were determined as pH 6, Chrysene-100 ppm, nitrogen source -1000 ppm and at 144 hrs using the design of experiments. The organism showed good oil degradation capacity and maximum growth was achieved in 6 days. Biosurfactant obtained from the biodegradation medium was confirmed to be lipopeptide using TLC, FTIR and GCMS.

Molecular characterization of a novel strain of Bacillus halotolerans protecting wheat from sheath blight disease caused by Rhizoctonia solani Kühn.

A new Bacillus halotolerans strain Bacillus halotolerans LDFZ001 resistant to sheath blight in wheat is isolated. Bacillus halotolerans LDFZ001 harbors a new kijanimicin biosynthetic gene cluster, and the functional expression of SFP and MFS contribute to its antipathogen ability.

Modification of Thin Film Composite Membrane by Chitosan-Silver Particles to Improve Desalination and Anti-Biofouling Performance.

Reverse osmosis (RO) desalination is a technology that is commonly used to mitigate water scarcity problems; one of its disadvantages is the bio-fouling of the membranes used, which reduces its performance. In order to minimize this problem, this study prepared modified thin film composite (TFC) membranes by the incorporation of chitosan–silver particles (CS–Ag) of different molecular weights, and evaluated them in terms of their anti-biofouling and desalination performances. The CS–Ag were obtained using ionotropic gelation, and were characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The modified membranes were synthetized by the incorporation of the CS–Ag using the interfacial polymerization method. The membranes (MCS–Ag) were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle. Bactericidal tests by total cell count were performed using Bacillus halotolerans MCC1, and anti-adhesion properties were confirmed through biofilm cake layer thickness and total organic carbon (%). The desalination performance was defined by permeate flux, hydraulic resistance, salt rejection and salt permeance by using 2000 and 5000 mg L−1 of NaCl. The MCS–Ag-L presented superior permeate flux and salt rejection (63.3% and 1% higher, respectively), as well as higher bactericidal properties (76% less in total cell count) and anti-adhesion capacity (biofilm thickness layer 60% and total organic carbon 75% less, compared with the unmodified membrane). The highest hydraulic resistance value was for MCS–Ag-M. In conclusion, the molecular weight of CS–Ag significantly influences the desalination and the antimicrobial performances of the membranes; as the molecular weight decreases, the membranes’ performances increase. This study shows a possible alternative for increasing membrane useful life in the desalination process.

Characterization of an Endophytic Antagonistic Bacterial Strain Bacillus halotolerans LBG-1-13 with Multiple Plant Growth-Promoting Traits, Stress Tolerance, and Its Effects on Lily Growth.

Microbial inoculants are an important tool for increasing arable land productivity and decreasing mineral fertilizer application. This study was aimed at isolating and identifying endophytic antagonistic bacteria from lily (Lilium davidii var. unicolor) roots grown in Northwestern China and at evaluating their antifungal activity and plant growth-promoting characteristics. For this purpose, endophytic bacteria were isolated from plant roots, and plant growth-promoting strains were identified. One bacterial strain, isolated from the root part, was identified as Bacillus halotolerans based on 16S rRNA gene sequence analysis and was designated as LBG-1-13. The strain showed antagonistic activities against important plant pathogens of lily including Botrytis cinerea, Botryosphaeria dothidea, and Fusarium oxysporum. The highest percentage of growth inhibition, i.e., 71.65 ± 2.39%, was observed for LBG-1-13 against Botryosphaeria dothidea followed by 68.33 ± 4.70% and 48.22 ± 4.11% against Botrytis cinerea and Fusarium oxysporum, respectively. Meanwhile, the isolated strain also showed plant growth-promoting traits such as the production of indole-3-acetic acid (IAA), siderophore, ACC deaminase, and phosphate solubilization activity. The strain showed ACC deaminase activity and was able to cleave 58.41 ± 2.62 nmol α-ketobutyrate (mg protein)-1 min-1. The strain exhibited tolerance to salt and drought stress in an in vitro experiment. The strain LBG-1-13 was able to grow in the presence of 10% NaCl and 20% polyethylene glycol (PEG) in the growth medium. Inoculation of Lilium varieties, Tresor and Bright Diamond, with LBG-1-13 enhanced plant growth under greenhouse and field conditions, respectively. All these results demonstrated that Bacillus halotolerans LBG-1-13 could be utilized as a good candidate in the biocontrol of lily disease and plant growth promotion in sustainable agriculture.

Characterization of redox and salinity-tolerant alkaline protease from Bacillus halotolerans strain DS5.

Bacillus halotolerans DS5 was isolated and identified as a halophilic microbe according to 16S rRNA analysis and the physical and chemical indices of the strain. A new alkaline protease (designated as prot DS5) from Bacillus halotolerans DS5 was produced, purified, and characterized. After 12 h incubation in the medium with 1% dextrin, 0.5% NaCl, 2% soluble starch, and 1% yeast extract (pH 7.0), it could reach the maximum enzyme activity (279.74 U/ml). The prot DS5 was stable in the pH range of 6.0-12.0 and the temperature range of 40-60°C, with maximal hydrolytic activities at pH 9 and at 50°C. In the presence of Ca2+, Mn2+, Ba2+, Mg2+, and Fe3+, protease activity was enhanced. The prot DS5 was maintained highly stable in NaCl (up to 2.5 mol/L), reducing and oxidizing agents. The prot DS5 also exhibited compatibility in other detergent ingredients, such as non-ionic and anionic surfactants. These properties of prot DS5 make this enzyme suitable for various industrial applications (e.g., detergents and leather).

Bacillus halotolerans KKD1 induces physiological, metabolic and molecular reprogramming in wheat under saline condition

Salt stress decreases plant growth and is a major threat to crop yields worldwide. The present study aimed to alleviate salt stress in plants by inoculation with halophilic plant growth-promoting rhizobacteria (PGPR) isolated from an extreme environment in the Qinghai–Tibetan Plateau. Wheat plants inoculated with Bacillus halotolerans KKD1 showed increased seedling morphological parameters and physiological indexes. The expression of wheat genes directly involved in plant growth was upregulated in the presence of KKD1, as shown by real-time quantitative PCR (RT-qPCR) analysis. The metabolism of phytohormones, such as 6-benzylaminopurine and gibberellic acid were also enhanced. Mining of the KKD1 genome corroborated its potential plant growth promotion (PGP) and biocontrol properties. Moreover, KKD1 was able to support plant growth under salt stress by inducing a stress response in wheat by modulating phytohormone levels, regulating lipid peroxidation, accumulating betaine, and excluding Na+. In addition, KKD1 positively affected the soil nitrogen content, soil phosphorus content and soil pH. Our findings indicated that KKD1 is a promising candidate for encouraging wheat plant growth under saline conditions.