Salt-tolerant Bacterial Strains Research Articles

Enhanced wheat productivity in saline soil through the combined application of poultry manure and beneficial microbes

BackgroundSoil salinity is one of the major menaces to food security, particularly in dealing with the food demand of the ever-increasing global population. Production of cereal crops such as wheat is severely affected by soil salinity and improper fertilization. The present study aimed to examine the effect of selected microbes and poultry manure (PM) on seedling emergence, physiology, nutrient uptake, and growth of wheat in saline soil. A pot experiment was carried out in research area of Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan. Saline soil (12 dS m− 1 w/w) was developed by spiking using sodium chloride, and used in experiment along with two microbial strains (i.e., Alcaligenes faecalis MH-2 and Achromobacter denitrificans MH-6) and PM. Finally, wheat seeds (variety Akbar-2019) were sown in amended and unamended soil, and pots were placed following a completely randomized design. The wheat crop was harvested after 140 days of sowing.ResultsThe results showed a 10–39% increase (compared to non-saline control) in agronomic, physiological, and nutritive attributes of wheat plants when augmented with PM and microbes. Microbes together with PM significantly enhanced seedling emergence (up to 38%), agronomic (up to 36%), and physiological (up to 33%) in saline soil as compared to their respective unamended control. Moreover, the co-use of microbes and PM also improved soil’s physicochemical attributes and enhanced N (i.e., 21.7%-17.1%), P (i.e., 24.1-29.3%), and K (i.e., 28.7%-25.3%) availability to the plant (roots and shoots, respectively). Similarly, the co-use of amendments also lowered the Na+ contents in soil (i.e., up to 62%) as compared to unamended saline control. This is the first study reporting the effects of the co-addition of newly identified salt-tolerant bacterial strains and PM on seedling emergence, physiology, nutrient uptake, and growth of wheat in highly saline soil.ConclusionOur findings suggest that co-using a multi-trait bacterial culture and PM could be an appropriate option for sustainable crop production in salt-affected soil.

Development of Halotolerant Microbial Consortia for Salt Stress Mitigation and Sustainable Tomato Production in Sodic Soils: An Enzyme Mechanism Approach

Salt stress caused by sodic soils is an important constraint that impacts the production of crucial solanaceous vegetable crops globally. Halotolerant poly-extremophiles rhizobacteria can inhabit hostile environments like salinity, drought, etc. The present study was aimed to design a halotolerant micro-formulation using highly salt-tolerant bacterial strains previously isolated from salt-tolerant rice and wheat rhizosphere in sodic soil. Nine halotolerant isolates were examined for plant growth-promoting traits and biomass production in pot studies with sodic soil of pH 9.23 in tomato. Compatible, efficient isolates were aimed to be formulated into different consortia like PGPR-C1, PGPR-C2 and, PGPR-C3 for field evaluation in sodic soils of pH 9.14. Halotolerant rhizobacterial consortia (PGPR-C3) comprising Lysinibacillus spp. and Bacillus spp. were found to produce extracellular enzymes like amylase, protease, cellulase, and lipase, showing significantly enhanced vegetative parameters, yield and lycopene content of tomato hybrid NS585 under salt-stressed sodic soils. PGPR-C3 consortia also showed enhanced plant growth-promoting activities and halo tolerance like high Indole acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase, and antioxidative enzyme activity over the uninoculated control. Further, inoculation with PGPR-C3 consortia resulted in the efficient exclusion of Na+ ions from the rhizosphere through increased absorption of K+. Results of the study reveal that inoculation with PGPR-C3 consortia could alleviate the salt stress and promotes the successful cultivation of tomato crop in sodic soils. It can be considered the best option for eco-friendly, sustainable cultivation of vegetables like a tomato in sodic soils with a high pH range of up to 9.14.

Bacillus Consortia Modulate Transcriptional and Metabolic Machinery of Arabidopsis Plants for Salt Tolerance

Rhizobacteria that are helpful to plants can lessen the impacts of salt stress, and they may hold promise for the development of sustainable agriculture in the future. The present study was intended to explicate consortia of salt-tolerant plant-beneficial rhizobacteria for the amelioration of salinity stress in Arabidopsis plants. Inoculation with both the consortia positively influenced the growth of plants as indicated by total chlorophyll content, MDA content, and antioxidant enzyme activities under stressful conditions.Both the multi-trait consortia altered the expression profiles of stress-related genes including CSD1, CAT1, Wrky, Ein, Etr, and ACO. Furthermore, the metabolomic analysis indicated that inoculated plants modulated the metabolic profiles to stimulate physiological and biochemical responses in Arabidopsis plants to mitigate salt stress. Our study affirms that the consortia of salt-tolerant bacterial strains modulate the transcriptional as well as metabolic machinery of plants to protect them from salinity stress. Nevertheless, the findings of this study revealed that consortia are composed of salt-tolerant bacterial strains viz. Bacillus safensis NBRI 12M, B. subtilis NBRI 28B, and B. subtilis NBRI 33N demonstrated significant improvement in Arabidopsis plants under saline stress conditions.

Wheat plant –Plant Growth Promoting Rhizobacteria (PGPR) interaction to alleviate the salt stress in vitro and in vivo

The current work studied the mechanistic basis of salt tolerant PGPR bacteria in alleviating salinity stress in wheat.Two experiments were conducted at the Agricultural Research Center (ARC), 2021-2022, to evaluate the interaction between wheat var. Misr1 and two salt tolerant PGPR bacterial strains, Azospirillum (A.) brasilense NO40 and Bacillus thuringiensis (Bt) under saline conditions. The staining technique used to detect the colonization effectiveness of applied bacteria. Images of 30-day wheat seedlings were captured and subjected to the following measurements: root area, leaf area, root length, shoot length, and dark green color index (DGCI). TEM was used to look for bacterial colonization in wheat seedling. Chlorophyll, proline, peroxidase activity, rhizosphere dehydrogenase activity and electrical conductivity (EC) were all quantified. Results revealed that the wheat seedling roots inoculated with the salt tolerant bacterial strains produced a highly intense red colour. The colonized bacteria appeared on the outer surface of the root and intercellular space of root tissue. The data showed a significant rise in all measured parameters in the inoculated wheat seedlings with the salt tolerant bacterial strains compared to the non-inoculated wheat seedlings. Additionally, the wheat seedlings inoculated with a mixture of NO40 and Bt showed the best results as compared to that inoculated with only NO40 or with only Bt. Finally, EC values before and after planting with the inoculated wheat seeds revealed a decrease in the salinity of the soil rhizosphere (9.27 mmhos/cm vs. 5.1 mmhos/cm). In conclusion: Salt stress in wheat saline soils was alleviated by bacterial strains studied. Optimum results were obtained from the mixture of A. brasilense and Bt. Results must later be verified in field trials.

Characterization of Halophilic Inulinase Producing Strains of Bacillus and Klebsiella Species Isolated From the Salt Mines of Pakistan

Halophiles are excellent sources of enzymes which are not only salt stable but also perform catalysis under extreme reaction conditions. The habitat of salt mines and its microbial diversity have not been thoroughly explored. In the present study, seven halophilic inulinase-producing bacteria (H1N1–H1N7) were isolated from the Bahadarkhel salt mines of Pakistan, and were identified based on their morphological, biochemical and molecular features. The strains H1N3, H1N4, H1N6, H1N7 were capable of growing at 20% salt concentration and therefore were considered as extremely halotolerant. Inulinase activities of the isolates were detected in inulin-containing broth media, and were further confirmed on inulin-based agar plates. The strains HIN1, H1N3, H1N5, and H1N7 exhibited the maximum zone of clearance (≥15 mm) on inuline agar medium. The strain H1N1 showed the highest zone of clearance of 19 mm. Morphological, biochemical and molecular characterization showed that the inulinase producing isolates were related to Bacillus and Klebsiella genera. The molecular identification was based on 16S rRNA gene sequencing. The strain H1N2 was capable of producing the four tested halozymes including inulinase, amylase, protease, and lipase. The strains HIN3, HIN4, and H1N5 were capable of producing three halozymes, i.e., inulinase, amylase, and protease while the strains H1N6 and H1N7 produced inulinases, lipases and proteases. These salt tolerant bacterial strains exhibiting diverse enzyme characteristics and phylogeny could be highly useful for future practical applications.

Isolation and selection of salt-tolerant bacterial strains capable of solubilizing phosphorus and synthesizing phosphatase enzyme from rice-shrimp soil in Mekong River Delta, Vietnam

The aim of this study was to isolate and select salt tolerant bacteria having both functions in phosphorus solubilization and phosphatase synthesis from rice-shrimp farming soil in saline areas in Mekong River Delta of Vietnam. Phosphorus solubilizing bacteria were isolated on National Botanical Research Institute's Phosphate (NBRIP) agar medium containing 1% NaCl and the activity of phosphatase enzyme was determined by disodium p-nitrophenyl phosphate reagent method at a wavelength of 420 nm. The result showed that from 15 saline soil samples, a total of 95 strains of phosphorus solubilizing bacteria were isolated and 19 of them showed their good phosphorus solubilization. The results about phosphatase activities of these 19 strains illustrated that TBT5-3 bacterial strain was the highest phosphatase producing strain with an amount of 0.377 U/mL after 10 days of incubation. This strain showed its best phosphatase producing capacity when cultured in the liquid culture medium containing pH 5, 1% NaCl, glucose and urea under the shaking speed of 120 rpm. Based on 16S rRNA gene sequence analysis this phosphatase synthesizing bacterial strain was genetically identified as species of Bacillus sp. TBT5-3 since 100% of this train sequence is affiliated with Bacillus megaterium.

Isolation of two salt-tolerant strains from activated sludge and its COD degradation characteristics from saline organic wastewater

The efficient biological treatment of saline wastewater has been limited by the low activities of microorganisms under saline conditions. High salinity poses unbalance osmotic stress across the cell wall and even leads to cell plasmolysis. In this work, we aim to isolate salt-tolerant bacterial strains from activated sludge, and apply them for degrading chemical oxygen demand (COD) of saline organic wastewater. Two salt-tolerant strains were screened and isolated from activated sludge, which was domesticated with salty water for over 300 days. The two strains were identified as Bacillus cereus (strain A) and Bacillus anthracis (strain B) through 16S rRNA sequencing. The degradation characteristics of strain A were explored. The results showed the relative membrane permeability of strain A remained stable under high salt stress, which glycine and proline play an important role to maintain cell osmotic. The protein and soluble sugar amounts of strain were increased by higher salt concentrations. In simulating saline wastewater, the optimum culture temperature, pH, salinity, influent COD concentration and inoculation amount of strain A were 35 °C, 9, 4%, 8000 mg L−1, 6%, respectively. Optimal conditions could provide guidance for the treatment of practical saline wastewater. The linear regression model of each impact factor built based on the result PB experiment revealed that cross-linking time has the most significant influence on COD removal for salt-tolerant strains. It will provide theoretical basis for biological treatment of saline organic wastewater.

Bioremediation of tannery effluent by Cr- and salt-tolerant bacterial strains.

Microorganisms have great potential to control environmental pollution, particularly industrial sources of water pollution. Currently, leather industry is regarded as the most polluting and suffering from negative impacts due to the pollution it adds to the environment. Chromium, one of the hazardous pollutants discharged from tanneries, is highly toxic and carcinogenic in nature. Effective treatment of tannery effluent is a dire need of the era as a part of environmental management. Among all the wastewater treatment technologies, bioremediation is the most effective and environment-friendly tool to manage the water pollution. The present study evaluated the potential of 11 previously isolated bacterial strains, tolerant to high concentrations of salts and Cr for the bioremediation of tannery effluent. Among all the tested strains, Enterobacter sp. HU38, Microbacterium arborescens HU33, and Pantoea stewartii ASI11 were found most effective in reducing biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and chromium (Cr) 70, 63, 57, 87, and 54%, respectively, of tannery effluent and proliferated well under highly toxic conditions, at 9days of incubation. The pollutant removal efficacy of these bacterial strains can be improved by extending the incubation period or by increasing the amount of inoculum.

A halotolerant Enterobacter sp. displaying ACC deaminase activity promotes rice seedling growth under salt stress

Agricultural productivity is proven to be hampered by the synthesis of reactive oxygen species (ROS) and production of stress-induced ethylene under salinity stress. One-aminocyclopropane-1-carboxylic acid (ACC) is the direct precursor of ethylene synthesized by plants. Bacteria possessing ACC deaminase activity can use ACC as a nitrogen source preventing ethylene production. Several salt-tolerant bacterial strains displaying ACC deaminase activity were isolated from rice fields, and their plant growth-promoting (PGP) properties were determined. Among them, strain P23, identified as an Enterobacter sp. based on phenotypic characteristics, matrix-assisted laser desorption ionization-time of flight mass spectrometry data and the 16S rDNA sequence, was selected as the best-performing isolate for several PGP traits, including phosphate solubilization, IAA production, siderophore production, HCN production, etc. Enterobacter sp. P23 was shown to promote rice seedling growth under salt stress, and this effect was correlated with a decrease in antioxidant enzymes and stress-induced ethylene. Isolation of an acdS mutant strain enabled concluding that the reduction in stress-induced ethylene content after inoculation of strain P23 was linked to ACC deaminase activity.

Native halo-tolerant plant growth promoting rhizobacteria Enterococcus and Pantoea sp. improve seed yield of Mungbean (Vigna radiata L.) under soil salinity by reducing sodium uptake and stress injury.

The beneficial microbial-plant interaction plays important role in the soil health, crop growth and productivity. Plant growth promoting rhizobacteria (PGPR) are such beneficial microorganisms, which in association with plant roots not only promote their growth but also help in counteracting the detrimental effects of soil stresses. Salt stress is one such stress, frequently confronted by the plants. The present study aimed at isolation and identification of PGPR inhabiting the mungbean rhizosphere, testing them for salt (NaCl) tolerance and subsequently in salt-supplemented mungbean crop. For this purpose, two salt-tolerant bacterial strains belonging to genus Pantoea and Enterococcus, characterized for their P-solubilization ability, indole acetic acid and siderophore production were selected. These two PGPR were further evaluated for their effect on the salt-stressed mungbean plants, grown at two salt concentrations (5 and 10dS/m). The plants treated with the combination of PGPR showed better performance in growth (16-37%) and yield (22-32%), under salt stress, as compared with control. The increasing salt concentration was found to increase the membrane damage, Na+ concentration in the plants. PGPR treatments effectively reduced the Na+ concentration (17-41%), membrane damage (1.1-1.5 folds) and enhanced the antioxidants i.e. ascorbic acid (8-26%) and glutathione (10-30%) in salt-stressed plants, in comparison to uninoculated stressed plants. Overall, the results indicated that both PGPR were effective as stress mitigators however, in combination they showed relatively better improvement in growth, yield as well as oxidative parameters of the salt-affected plants. These findings about the effects of native salt-tolerant PGPR Pantoea and Enterococcus sp. in mungbean crop are novel.

Characterization of a salt resistant bacterial strain Proteus sp. NA6 capable of decolorizing reactive dyes in presence of multi-metal stress.

Microbial biotechnologies for the decolorization of textile wastewaters have attracted worldwide attention because of their economic suitability and easiness in handling. However, the presence of high amounts of salts and metal ions in textile wastewaters adversely affects the decolorization efficiency of the microbial bioresources. In this regard, the present study was conducted to isolate salt tolerant bacterial strains which might have the potential to decolorize azo dyes even in the presence of multi-metal ion mixtures. Out of the tested 48 bacteria that were isolated from an effluent drain, the strain NA6 was found relatively more efficient in decolorizing the reactive yellow-2 (RY2) dye in the presence of 50gL(-1) NaCl. Based on the similarity of its 16S rRNA gene sequence and its position in a phylogenetic tree, this strain was designated as Proteus sp. NA6. The strain NA6 showed efficient decolorization (>90%) of RY2 at pH 7.5 in the presence of 50gL(-1) NaCl under static incubation at 30°C. This strain also had the potential to efficiently decolorize other structurally related azo dyes in the presence of 50gL(-1) NaCl. Moreover, Proteus sp. NA6 was found to resist the presence of different metal ions (Co(+2), Cr(+6), Zn(+2), Pb(+2), Cu(+2), Cd(+2)) and was capable of decolorizing reactive dyes in the presence of different levels of the mixtures of these metal ions along with 50gL(-1) NaCl. Based on the findings of this study, it can be suggested that Proteus sp. NA6 might serve as a potential bioresource for the biotechnologies involving bioremediation of textile wastewaters containing the metal ions and salts.

Isolation and Characterization of Salt-Tolerant Bacterial Strains in Salt-Affected Soils of Erzurum, Turkey

In the current study, 18 salt-tolerant bacteria were isolated from salt-affected soil of Erzurum, Turkey. Forty-five bacterial isolates were identified and characterized by conventional and molecular techniques. These 45 sequenced isolates were identified as 16 different genus including Bacillus (19 isolates), Staphylococcus (3 isolates), Halobacillus (4 isolates), Zhihengliuella (2 isolates), Oceanobacillus (2 isolates), Halomonas (1 isolate), Nesterenkonia (2 isolates), Promicromonospora (2 isolates), Jeotgalibacillus (2 isolates), Planococcus (2 isolates), Virgibacillus (1 isolate), Terribacillus (1 isolate), Thalassobacillus (1 isolate), Marinibacillus (1 isolate), Gracilibacillus (1 isolate) and Microbacterium (1 isolate). According to the results obtained, investigated bacterial strains have high salt tolerance and significant enzyme activities that can improve soil nutrient cycling and soil fertility. The current article provides the evaluation and diversity of the potential halotolerant and halophilic bacterial strains in salt-affected soils of Erzurum, Turkey.

Isolation and Characterization of Salt-Tolerant Bacterial Strains in Salt-Affected Soils of East Anatolian Region

In the current study, 18 salt-tolerant bacteria were isolated from salt-affected soil in the east Anatolian region. The obtained isolates were identified and characterized by conventional (morphology, physiology, and biochemical tests) and molecular techniques 16 rDNA. Among 18 sequenced isolates, 6 Bacillus, 1 Halomonas, 2 Halobacillus, 2 Zhihengliuella, 2 Oceanobacillus, 1 Virgibacillus, 1 Staphylococcus, 1 Thalassobacillus, 1 Exiguobacterium were identified with high similarity to previously identified strains in the literature. According to the results obtained, investigated bacterial strains have high salt tolerance and significant enzyme activities that can improve soil nutrient cycling and fertility. To the best of our knowledge, the current article is the first study in evaluation and diversity of potential halophlic/halotolerant bacterial strains in salt-affected soils of the east Anatolian region.

Aerobic digestion of tannery wastewater in a sequential batch reactor by salt-tolerant bacterial strains

Among the industries generating hyper saline effluents, tanneries are prominent in India. Hyper saline wastewater is difficult to treat by conventional biological treatment methods. Salt-tolerant microbes can adapt to these conditions and degrade the organics in hyper saline wastewater. In this study, the performance of a bench scale aerobic sequencing batch reactor (SBR) was investigated to treat the tannery wastewater by the salt-tolerant bacterial strains namely Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Styphylococcus aureus. The study was carried out under different operating conditions by changing the hydraulic retention time, organic loading rate and initial substrate concentration. From the results it was found that a maximum COD reduction of 90.4% and colour removal of 78.6% was attained. From this study it was found that the salt-tolerant microorganisms could improve the reduction efficiency of COD and colour of the tannery wastewater.

Comparative study of wild and transformed salt tolerant bacterial strains on Triticum aestivum growth under salt stress

Eleven salt tolerant bacteria isolated from different sources (soil, plants) and their transformed strains were used to study their influence on Triticum aestivum var. Inqlab-91 growth under salt (100 mM NaCl) stress. Salt stress caused reduction in germination (19.4%), seedling growth (46%) and fresh weight (39%) in non-inoculated plants. In general, both wild and transformed strains stimulated germination, seedling growth and fresh weight in salt free and salt stressed conditions. At 100 mM NaCl, Staphylococcus xylosus ST-1 caused 25% increments in seedling length over respective control. Soluble protein content significantly enhanced (49%) under salt stress as compared to salt free control. At 100 mM NaCl parental strain PT-5 resulted about 32% enhancement in protein content over respective control treatment. Salt stress induced the promotion of auxin content in seedlings. Overall, Bacillus subtilis HAa2 and transformed E. coli -SP-7-T, caused 33% and 30% increases in auxin content, respectively, were recorded under salt stress in comparison to control.

Comparative study of wild and transformed salt tolerant bacterial strains on Triticum aestivum growth under salt stress

Eleven salt tolerant bacteria isolated from different sources (soil, plants) and their transformed strains were used to study their influence on Triticum aestivum var. Inqlab-91 growth under salt (100 mM NaCl) stress. Salt stress caused reduction in germination (19.4%), seedling growth (46%) and fresh weight (39%) in non-inoculated plants. In general, both wild and transformed strains stimulated germination, seedling growth and fresh weight in salt free and salt stressed conditions. At 100 mM NaCl, Staphylococcus xylosus ST-1 caused 25% increments in seedling length over respective control. Soluble protein content significantly enhanced (49%) under salt stress as compared to salt free control. At 100 mM NaCl parental strain PT-5 resulted about 32% enhancement in protein content over respective control treatment. Salt stress induced the promotion of auxin content in seedlings. Overall, Bacillus subtilis HAa2 and transformed E. coli -SP-7-T, caused 33% and 30% increases in auxin content, respectively, were recorded under salt stress in comparison to control.

A novel salt-tolerant mutant YWL-01 for the treatment of saline wastewater

The treatment of high-saline wastewater from some salt-end markets including agro-food industry is a serious problem yet to be solved in some coastal cities. The conventional physical-chemical techniques are energy-consuming and their startup and running costs are still high. Biological methods using salt-tolerant bacterial strains for the treatment of hypersaline wastewater provide one possible solution. In this study, one salt-tolerant mutant named YWL-01 was screened out by sewage treatment and proved to be a genetically stable salt-tolerant strain for saline wastewater treatment. First, combined mutagenesis was done on an isolated sewage treatment strain Bacillus Y for the screening of salt tolerance, and 11 mutants were obtained after subculture for many times. Then, a secondary screening test was performed for COD (chemical oxygen demand) and TOC (total organic carbon) removal efficiency analyses. At last, the best mutant YWL-01 with increased capacity to treat saline wastewater was chosen for use. RAPD (Random Amplified Polymorphic DNA) analysis of genetic stability on the mutant YWL-01 showed that it is a hereditary mutant for the treatment of high-saline wastewater.

Biological treatment of tannery wastewater by using salt-tolerant bacterial strains

BackgroundHigh salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater.ResultsFour salt tolerant bacterial strains isolated from marine and tannery saline wastewater samples were identified as Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Staphylococcus aureus. Growth factors of the identified strains were optimized. Tannery saline wastewater obtained from a Common Effluent Treatment Plant (CETP) near Chennai (southern India) was treated with pure and mixed consortia of four salt tolerant bacterial strains. Experiments with optimized conditions and varying salt content (between 2 and 10% (w/v) were conducted. Salt inhibition effects on COD removal rate were noted. Comparative analysis was made by treating the tannery saline wastewater with activated sludge obtained from CETP and with natural habitat microbes present in raw tannery saline wastewater.ConclusionSalt tolerant bacterial mixed consortia showed appreciable biodegradation at all saline concentrations (2%, 4%, 6%, 8% and 10% w/v) with 80% COD reduction in particular at 8% salinity level the consortia could be used as suitable working cultures for tannery saline wastewater treatment.

Efficiency of Different Chemical and Physical Agents for Curing of Plasmid/s from Salt Tolerant Bacterial Strains

Efficiency of Different Chemical and Physical Agents for Curing of Plasmid/s from Salt Tolerant Bacterial Strains