NaCl Tolerance Research Articles

The discovery and characterization of a novel chitinase with dual catalytic domains from a Qinghai-Tibetan Plateau wetland soil metagenome

A novel chitinase (P1724) was discovered from a Qinghai-Tibetan plateau microbial metagenome. P1724 contains two GH18 family catalytic domains and is phylogenetically distant from any of the chitinases studied. P1724 and its truncated versions, P1724(∆cGH18) and P1724(∆nGH18), were produced in Escherichia coli and characterized. Using colloidal chitin as substrate, the three recombinant proteins showed maximum hydrolytic activities at 40 °C, pH 5.0–6.0 and 0–0.5 M NaCl, and were cold adaptive, as they remained active at 4 °C; their chitinase activities were decreased with the presence of Cu2+ and EDTA, but increased with Ba2+ and Ca2+; they all showed both chitobiosidase and endochitinase activities. Compared to P1724(∆nGH18), P1724 and P1724(∆cGH18) shared more similarities in temperature and pH stabilities, NaCl tolerance, and substrate affinity, suggesting the N-terminal GH18 domain contributed more than the C-terminal GH18 did in biochemical characteristics of P1724. kcat/Km value of P1724 was significantly higher than the sum values of P1724(∆cGH18) and P1724(∆nGH18), which indicated that two GH18 domains of P1724 worked cooperatively in degrading chitin. This study has not only broadened the understanding of unknown chitinases in nature but also discussed the strategy of adding additional catalytic domains in enzyme engineering.

Lysinibacillus agricola sp. nov., isolated from soil.

A gram-staining-positive, rod-shaped bacterium, designed strain FJAT-51161T was isolated from farmland soil collected from Fujian Province, China. Growth was observed at 25-40°C (optimum 30°C), pH 7.0-9.0 (optimum 7.0), and NaCl tolerance in the range of 0-7% (w/v), respectively. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that the strain FJAT-51161T belonged to the genus Lysinibacillus, and had the closest relationship with Lysinibacillus xylanilyticus XDB9T (99.0% 16S rRNA sequence similarity). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values based on the genome sequence analysis between strain FJAT-51161T and the closest reference strain were 38.0% for dDDH and 88.7% for ANI, respectively, lower than the prokaryotic species delineation values. Further analysis showed that strain FJAT-51161T shared the fatty acid profiles such as iso-C15:0 (46.7%), iso-C16:0 (15.8%), C16:1 ω7c alcohol (14.0%), anteiso-C15:0 (6.9%) with other members of the genus Lysinibacillus. As the peptidoglycan contained the amino acids alanine, lysine, glycine and aspartic acid, the type A4α was deduced as found in the closest relatives of strain FJAT-51161T. The peptidoglycan of strain FJAT-51161T was L-Lys-D-Asp (type A4α). The main quinone was MK-7 and MK-6. The major polar lipids were diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE). The DNA G + C content is 36.6mol%. Based on the phenotypic characters and taxono-genomics study, strain FJAT-51161T is considered to represent a novel Lysinibacillus species, for which the name Lysinibacillus agricola sp. nov. is proposed. The type strain is FJAT-51161T (GDMCC1.2350T = KCTC 43326T).

Mechanism of nitric oxide enhancing NaCl tolerance of barley seedlings based on physiol-biochemical analysis and LC-MS metabolomics

Nitric oxide (NO) is involved in the abiotic stress of plants and enhanced NaCl tolerance of barley seedlings. However, the internal mechanism is unclear. In this study, the physiology and metabolomics characteristics of barley seedlings with the present of NO and its specific scavenger 2,4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) under NaCl stress were investigated to understand the key function of NO in NaCl tolerance. Results showed that sodium nitroprusside (SNP; a NO donor) alleviated the growth inhibition and oxidative damage caused by 60 mM of NaCl. The 0.2 mM SNP treated barley seedlings exhibited higher antioxidant enzymes activity, total phenolic content, antioxidant capacity, and free amino acids content. However, the 0.5 mM of cPTIO induced the opposite effects. Based on the results of metabolomics analysis, it was found that SNP enhanced glycolysis, galactose, fructose and mannose metabolism, as well as amino acids biosynthesis and tricarboxylic acid metabolisms in barley seedlings compared with NaCl stress. These results indicated that NO could induce barley seedlings tolerance to NaCl stress depending on its roles in enhancing phenolics accumulation, antioxidation enzymes activity, antioxidant capacity as well as accelerating the carbohydrate metabolism and amino acids biosynthesis.

Callus Formation and Regeneration Tendency of Justicia vasica Nees under Saline Conditions

Salinity is one of the major environmental threats to plants because a large number of plants are intolerant to NaCl stress. One such plant, Justicia vasica, which is the subject of our study, is said to have great medicinal properties. However, the natural occurrence and cultivation of this species has been constrained due to various factors including its poor seed germination rate under its normal conditions of habitat, and a low availability of seeds. This study was undertaken to examine the efficiency of callus formation and regenerative tendencies of Justicia vasica under saline conditions. The leaf, shoot tips and inter nodal cuttings were employed for this study using MS media formulated with several concentrations of different kinds of hormonal combinations. This study also tested the effects of different concentrations of NaCl on callus induction and growth. Each experiment was conducted thrice with 12 replicates. A superior level of callus formation was achieved by treating shoot tips with 2.0 mg/l α-naphthalene acetic acid (NAA) and 0.5 mg/l 6-benzyladenine purine (BAP) in combination. From this study, it was concluded that there was no inhibitory action from the medium supplemented with 0.05 mg/l NaCl. The optimal hormonal combination also exhibited highest rate of callus induction and growth with 0.05 mg/l NaCl added. There was no callus necrosis at this saline concentration after 60 days of inoculation. Furthermore, some somatic embryogenic callus displayed the organogenesis of leaf like structures after 75 days of inoculation. The development of salinity tolerance of plants by genetic application has been a vital area on modern agriculture as well as medicinal plant research because more land has been salinized through poor local irrigation practices. The present investigation assumed that the NaCl tolerance of this plant could be effectively obtained in vitro.

Genome-wide identification, characterization, and expression analysis of the monovalent cation-proton antiporter superfamily in maize, and functional analysis of its role in salt tolerance

Na+, K+ and pH homeostasis are important for plant life and they are controlled by the monovalent cation proton antiporter (CPA) superfamily. The roles of ZmCPAs in salt tolerance are not fully elucidated. In this study, we identified 35 ZmCPAs comprising 13 Na+/H+ exchangers (ZmNHXs), 16 cation/H+ exchanger (ZmCHXs), and 6 K+ efflux antiporters (ZmKEAs). All ZmCPAs have transmembrane domains and most of them were localized to plasma membrane or tonoplast. ZmCHXs were specifically highly expressed in anthers, while ZmNHXs and ZmKEAs showed high expression in various tissues. ZmNHX5 and ZmKEA2 were up-regulated in maize seedlings under both NaCl and KCl stresses. Yeast complementation experiments revealed the roles of ZmNHX5, ZmKEA2 in NaCl tolerance. Analysis of the maize mutants further validated the salt tolerance functions of ZmNHX5 and ZmKEA2. Our study highlights comprehensive information of ZmCPAs and provides new gene targets for salt tolerance maize breeding.

Overexpression of Glyoxalase III gene in transgenic sugarcane confers enhanced performance under salinity stress.

The glyoxalase pathway is a check point to monitor the elevation of methylglyoxal (MG) level in plants and is mediated by glyoxalase I (Gly I) and glyoxalase II (Gly II) enzymes in the presence of glutathione. Recent studies established the presence of unique DJ-1/PfpI domain containing protein named glyoxalase III (Gly III) in prokaryotes, involved in the detoxification of MG into D-lactic acid through a single step process. In the present study, eleven transgenic sugarcane events overexpressing EaGly III were assessed for salinity stress (100mM and 200mM NaCl) tolerance. Lipid peroxidation as well as cell membrane injury remained very minimal in all the transgenic events indicating reduced oxidative damage. Transgenic events exhibited significantly higher plant water status, gas exchange parameters, chlorophyll, carotenoid, and proline content, total soluble sugars, SOD and POD activity compared to wild type (WT) under salinity stress. Histological studies by taking the cross section showed a highly stable root system in transgenic events upon exposure to salinity stress. Results of the present study indicate that transgenic sugarcane events overexpressing EaGly III performed well and exhibited improved salinity stress tolerance.

PROBIOTIC POTENTIAL OF SOME LACTOBACILLUS STRAINS ISOLATED FROM RAW MILK

A total of 25 samples of raw cow milk, were collected randomly from street vendors and supermarkets in Zagazig city, Egypt for detection of the probiotic potential of some isolated Lactobacillus strains from raw milk. The obtained results revealed that the Lactobacillus Strains were detected in all the examined samples. The isolated strains were slightly affected by pH 3 and bile condition (0.5%). The obtained results displayed resistance against Erythromycin, Gentamycin and Tetracycline. Meanwhile, Ampicillin, Chloromphnicol, Steptomycin and Vancomycin exhibited an effect against some strains. The isolated strains produced ?-hemolysis, NaCl tolerance was positive for these strains. Also, ? galactosidase was produced.

Probiotic Properties and Immunomodulatory Activity of Lactobacillus Strains Isolated from Dairy Products.

Lactobacilli species are an effective biotherapeutic alternative against bacterial infections and intestinal inflammatory disorders. However, it is important to evaluate their beneficial properties, before considering them as probiotics for medical use. In this study we evaluated some probiotic properties of Lactobacillus rhamnosus GG, Lactobacillus rhamnosus KLSD, Lactobacillus helveticus IMAU70129, and Lactobacillus casei IMAU60214 previously isolated from dairy products and as control Lactobacillus casei Shirota. Experimental evaluations revealed that all strains expressed hydrophobicity (25–40%), auto-aggregation (55–60%), NaCl tolerance (1–4%), adhesion to Caco-2 cells (25–33%), partial inhibition on adherence of Escherichia coli ATCC 35218, Salmonella Typhimurium ATCC 14028, and Staphylococcus aureus ATCC 23219. Cell-free supernatants (CFS) of Lactobacilli also inhibit growth of these pathogens. In immunomodulatory properties a reduction of interleukin-8 (IL-8) and nitric oxide (NO) release was observed in assays with Caco-2 cells stimulated with interleukin-1β (1 ng/mL), or lipopolysaccharide (0.1 µg/mL). On the other hand, the damage induced to Caco-2 cells with sodium dodecyl sulfate (SDS) was attenuated when the cultured cells were pretreated with L. rhamnosus KLDS, L. helveticus IMAU70129 and L. casei IMAU60214. These Lactobacilli possess probiotic properties determined by both an antagonistic activity on pathogenic bacteria and reduction in the inflammatory response of cells treated with SDS, a pro-inflammatory stimulant.

Cadmium stress alleviation potential of Bruguiera cylindrica (L.) Blume enhances in combination with NaCl

A hydroponic experiment in NaCl tolerant mangrove, Bruguiera cylindrica plantlets was done to investigate the interactive effects of CdCl2+NaCl as well as the individual effects of CdCl2. CdCl2 alone results in enhanced level of cell membrane lipid peroxidation, damaging normal structure, and function of the membrane and there by leading to reduction of membrane stability index and thus severely promoting the electrolyte leakage than the combined treatment of CdCl2+NaCl. Antioxidants greatly contribute to cope with the stress by scavenging ROS and were more prominent in individual stress than combined stress. B. cylindrica can be categorized as a highly tolerant mangrove species with a Tolerance Index (TI) of above 60% toward CdCl2+NaCl (TI is 70 and 75% in leaf and root). But TI was only 63 and 67% in leaf and root, respectively, on exposure to CdCl2 alone indicating that this plant is less tolerant to Cd alone. The existence of B. cylindrica depends on the heavy metals being introduced into the mangrove ecosystem and imparts a combination stress along with NaCl. In this regard, B. cylindrica survives up to 0.20 mM CdCl2 along with NaCl. Thus, the high NaCl tolerance mechanisms in this mangrove species could be equally efficient in imparting tolerance toward high concentration of Cd along with NaCl and exhibits phytostabilization in polluted coastal wetlands.

Isolation, Characterization and Identification of Lactic Acid Bacteria as Probiotic

Lactic acid bacteria that grow as the adventitious microflora of foods or that are added to foods as cultures are generally considered to be harmless or even an advantage for human health. The objective of this study was to isolate, screen and identify lactic acid bacteria from different sources. As well, evaluate the more potent lactic acid bacteria isolates for their probiotic characteristics. Ninety-six bacterial isolates were isolated from different 18 sources, 51 (53%) isolates were able to hydrolyze 0.5% bile salts while 28 isolates were able to hydrolyze 1% bile salts. Also, only 11 isolates were able to tolerate 2% bile salts after 6h incubation periods. On the other hand, lactic acid bacteria isolates were able to survive at pH 1.5 and 3.0 as well 8.0. Also, these isolates were potent for cholesterol assimilation, NaCl tolerance, exopolysaccharides production, antioxidant activity. Lactic acid bacteria isolate MS87 that exhibited excellent probiotic characteristics was identified using 16S rRNA sequence as Pediococcus pentosaceus. This study led to suggest that environmental-derived lactic acid bacteria-strains could be used as a potential source of probiotic.

Isolation, Identification and Analysis of Probiotic Characteristics of Lactobacillus spp. from Regional Yoghurts from Surendranagar District, Gujarat

Background: Probiotics are good bacterial species. They confer health benefits to the human gastrointestinal tract. Lactobacillus spp. and Bifidobacterium are the most commonly used probiotic strains.Methods: In the present study; Lactic acid bacteria were isolated from the different regional yoghurt sample (masti, lite and household fermented dahi). Identification and analysis was done by different morphological characterization, biochemical tests and probiotic characterization like pH tolerance, bile salt tolerance, temperature tolerance and NaCl tolerance etc. of isolated lactobacillus spp.Result: This study indicated that Lactobacillus species from yogurt samples have potential probiotic properties.

Isolation of Probiotic Lactobacilli from Indigenous Yogurt and Cheese and Their Antagonistic Roles Against Foodborne Pathogens

Background: Probiotic bacteria are one of the useful dietary supplements for human health. The main reason for selecting probiotics is the lack of prolonged side effects. Objectives: This study aimed to isolate lactobacilli from traditional yogurt and cheese samples collected in Neyshabur city, Khorasan Razavi, Iran, and to characterize them using specific biochemical and molecular assays. Methods: The probiotic potency of bacteria was tested by resistance to acid, bile, NaCl, and organic acid production. Moreover, the antagonistic effects of the isolates were investigated against enteric pathogenic bacteria using the well diffusion method. Bacteriocin production was also investigated using the microtiter plate assay. Results: Four Lactobacillus spp. with > 99% homology to L. reuteri, L. plantarum, and L. acidophilus, were isolated with probiotic potency. The quantitative measurements used in the study with the statistical analysis resulted in the interpretation of good effects against Clostridium perfringens, Salmonella typhi, Staphylococcus aureus, and Listeria monocytogenes. Our isolates exhibited bile salt hydrolase activity, excellent NaCl and acid tolerance (pH = 3), and bacteriocin production. Conclusions: Our results showed that Lactobacillus strains isolated from Neyshabur traditional cheese could be considered good potential probiotic strains and had more antagonistic activity against human pathogens when compared to other samples. Their antibacterial activity was associated with both bacteriocin and organic acids production, but they should be further investigated for their human health benefits.

The Prospects of Lactobacillus oris as a Potential Probiotic With Cholesterol-Reducing Property From Mother's Milk.

This experiment was conducted to characterize potential Lactobacillus spp. isolated from mother's milk and infant feces to obtain new and specific probiotic strains. In this study, seven ascendant strains were identified as Lactobacillus spp. based on their morphological characteristics and biochemical properties. Among them, only one (C-1) isolate was identified as Lactobacillus oris through BioLogTM identification. The study further investigated the isolate through probiotic potentiality tests such as pH and bile tolerance, NaCl tolerance test, gastric juice tolerance, antioxidant activity, resistance to hydrogen, reduction of sodium nitrate, antimicrobial activity, and antibiotic susceptibility test. The result showed that the strain is a potential probiotic based on probiotic capability. The identified strain was most acid-tolerant and retained around 80% viability for up to 4 h at pH 1.0 and 2.0. The isolate showed tolerance against up to 1.50% bile concentration and gastric juice and was able to grow 1–6% NaCl concentrations. Lactobacillus oris showed resistance to most antibiotics as well as antagonistic activity against the tested pathogen, good antioxidant properties, reduction of sodium nitrate and H2O2. The isolate exhibited good intestinal epithelial adhesion properties, and SDS page was performed for secreted protein analysis. Moreover, the strain showed promising cholesterol-lowering properties based on the cholesterol level. This present result indicates that L. oris has superior probiotic properties and can be regarded as a potential probiotic candidate.

Neobacillus sedimentimangrovi sp. nov., a Thermophilic Bacterium Isolated from Mangrove Sediment.

Two Gram-stain positive, rod-shaped, endospore-forming, aerobic, thermophilic strains, designated FJAT-2464T and FJAT-52740, were isolated from the sediment collected from Zhangjiang Estuary Mangrove National Nature Reserve in Fujian Province, China. The 16S rRNA gene sequence similarity between strains FJAT-2464T and FJAT-52740 was 100%. The result suggests that strains FJAT-2464T and FJAT-52740 belong to the same genome species, hence only FJAT-2464T was considered for further analysis. Strain FJAT-2464T showed the highest 16S rRNA gene sequence similarities to the type strains of Neobacillus thermocopriae SgZ-7T (99.9%), Neobacillus cucumis AP-6T (97.6%) and Neobacillus drentensis LMG 21831T (97.5%). Growth was observed at 25-65°C (optimum 60°C), pH 7.0-8.0 (optimum 8.0) with NaCl tolerance up to 1.0% (w/v) (optimum without NaCl %). The cell-wall peptidoglycan contained meso-diaminopimelic acid and MK-7 was the only respiratory quinone. The major fatty acids were iso-C15:0 and anteiso-C15:0. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified aminophospholipid and unidentified lipids. The average nucleotide identity and digital DNA-DNA hybridization values between strain FJAT-2464T and the most closely related strain N. thermocopriae SgZ-7T was below the threshold value for species delineation. Based on the above results, strain FJAT-2464T represents a novel species of the genus Neobacillus, for which the name Neobacillus sedimentimangrovi sp. nov. is proposed. The type strain is FJAT-2464T (= MCCC 1K04406T = KCTC 43264T).

Assessment of Bacterial Community Structure in Saline Sediment Microcosms Exposed for the First Time to the Ionic Liquid 1-Ethyl-3-Methylimidazolium Chloride

Ionic liquids, such as 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), have immense applicability as solvents in different industrial settings including lignocellulosic biofuel production. However, these solvents are toxic to most organisms. Moderate halophiles are an established microbial group that can tolerate [Emim]Cl by employing their general salt-tolerant mechanisms. Anticipating future exposure of [Emim]Cl to natural environments, the present study was designed to evaluate bacterial community structure in slightly saline (20 g L−1 or 2%) sediments of Sambhar Salt Lake, Rajasthan, India, after microcosm enrichment with [Emim]Cl. The sediment used does not have any native [Emim]Cl (100 mM)–tolerant bacteria. However, after a two-step enrichment of 25 days each with 0.5 M and 1.0 M [Emim]Cl, the tolerant colonies increased to 54.9% and 93.0%, respectively. But in similar NaCl enrichment, or control incubations, such colonies were absent. Bacterial 16S rRNA gene amplicon sequence-based alpha diversity in 50 days [Emim]Cl-enriched set was lower than the initial, control and NaCl-enriched sets (Shannon index of 6.71 vs. 8.0–8.26, respectively). Even its bacterial community structure was distinct from the remaining three sets, which clustered together. [Emim]Cl-enriched set has almost fourfold higher abundance of Proteobacteria (50.36%), with Gammaproteobacteria (32.25%) and particularly Enterobacteriaceae (24.19%) members being predominant with a predicted higher abundance of membrane transporters. Cyanobacteria, Actinobacteria and Bacteroidetes were most sensitive groups to [Emim]Cl enrichment. Although moderate halophiles can utilise their general NaCl tolerance mechanisms to resist toxicity of [Emim]Cl, abrupt exposure of the later disturbs microbial population structure and thus demands their meticulous use avoiding environmental contamination.

Combination of mutagenesis and adaptive evolution to engineer salt-tolerant and aroma-producing yeast for soy sauce fermentation.

The moromi fermentation of high-salt liquid-state fermentation (HLF) soy sauce is usually performed in high-brine solution (17-20%, w/w), which decreases the metabolic activity of aroma-producing yeast. To enhance the soy sauce flavors, increasing the salt tolerance of aroma-producing yeasts is very important for HLF soy sauce fermentation. In the present study, atmospheric and room-temperature plasma (ARTP) was first used to mutate the aroma-producing yeast Wickerhamomyces anomalus, and the salt tolerant strains were obtained by selection of synthetic medium with a sodium chloride concentration of 18% (w/w). Furthermore, adaptive laboratory evolution (ALE) was used to improve the salt tolerance of the mutant strains. The results obtained indicated that the combination use of ARTP and ALE markedly increased the NaCl tolerance of the yeast by increasing the cellular accumulation of K+ and removal of cytosolic Na+ , in addition to promoting the production of glycerin and strengthening the integrity of the cell membrane and cell wall. In soy sauce fermentation, the engineered strains improved the physicochemical parameters of HLF soy sauce compared to those produced by the wild-type strain, and the engineered strains also increased the alcohol, acid and aldehyde production, and enriched the types of esters in the soy sauce. The results of the present study indicated that the combination of ARTP mutagenesis and ALE significantly improved the salt tolerance of the aroma-producing yeast, and also enhanced the production of volatiles of HLF soy sauce. © 2021 Society of Chemical Industry.

Sodium Influx and Potassium Efflux Currents in Sunflower Root Cells Under High Salinity.

Helianthus annuus L. is an important oilseed crop, which exhibits moderate salt tolerance and can be cultivated in areas affected by salinity. Using patch-clamp electrophysiology, we have characterized Na+ influx and K+ efflux conductances in protoplasts of salt-tolerant H. annuus L. hybrid KBSH-53 under high salinity. This work demonstrates that the plasma membrane of sunflower root cells has a classic set of ionic conductances dominated by K+ outwardly rectifying channels (KORs) and non-selective cation channels (NSCCs). KORs in sunflower show extreme Na+ sensitivity at high extracellular [Ca2+] that can potentially have a positive adaptive effect under salt stress (decreasing K+ loss). Na+ influx currents in sunflower roots demonstrate voltage-independent activation, lack time-dependent component, and are sensitive to Gd3+. Sunflower Na+-permeable NSCCs mediate a much weaker Na+ influx currents on the background of physiological levels of Ca2+ as compared to other species. This suggests that sunflower NSCCs have greater Ca2+ sensitivity. The responses of Na+ influx to Ca2+ correlates well with protection of sunflower growth by external Ca2+ in seedlings treated with NaCl. It can be, thus, hypothesized that NaCl tolerance in sunflower seedling roots is programmed at the ion channel level via their sensitivity to Ca2+ and Na+.

Potassium Lactate as a Strategy for Sodium Content Reduction without Compromising Salt-Associated Antimicrobial Activity in Salami.

Reformulating recipes of ready-to-eat meat products such as salami to reduce salt content can mitigate the negative health impacts of a high salt diet. We evaluated the potential of potassium lactate (KL) as a sodium chloride (NaCl) replacer during salami production. NaCl and KL stress tolerance comparisons showed that four food-derived Listeria innocua isolates were suitable as biologically safe Listeria monocytogenes surrogates. Effects of the high salt (4% NaCl) concentration applied in standard salami recipes and a low salt (2.8% NaCl) plus KL (1.6%) combination on product characteristics and growth of contaminating Listeria and starter culture were compared. Simulated salami-ripening conditions applied in meat simulation broth and beef showed that the low salt plus KL combination retained similar to superior anti-Listeria activity compared to the high salt concentration treatment. Salami challenge tests showed that the low NaCl plus KL combination had comparable anti-Listeria activity as the high NaCl concentration during ripening and storage. No significant differences were detected in starter culture growth profiles and product characteristics between the high NaCl and low NaCl plus KL combination treated salami. In conclusion, KL replacement enabled a 30% NaCl reduction without compromising the product quality and antimicrobial benefits of high NaCl concentration inclusion.

Exogenous Zinc Induced NaCl Tolerance in Okra (Abelmoschus Esculentus) by Ameliorating Osmotic Stress and Oxidative Metabolism

ABSTRACT Zinc appeared to be an important modulator with specific functions in plant physiology and increase resistance against different abiotic stresses. Many advances regarding role of zinc under abiotic stress in plants have been made since its revelation, therefore, present study was intended to understand the ameliorating role of zinc on morpho-physiological and biochemical responses of the okra varieties (Anmol and Haseena) when exposed to salt stress. A solution culture experiment was conducted to understand the protective role of zinc in relation to growth, physiological, ionic and antioxidant attributes in two okra varieties under saline condition. The growth medium was salinized with three salinity (Control, 80 mM L−1 and 160 mM L−1 NaCl) and one zinc level (30 µM L−1) applied exogenously in combine and sole form. Salt stress significantly reduces plant dry matter accumulation, chlorophyll contents, relative water contents (RWC), membrane stability index (MSI), K+/Na+ ratio and activities of antioxidant enzymes (POD, SOD, APX, CAT) and these effects are more prominent at high salt level (160 mM). Addition of zinc-alleviated salt toxicity is more conspicuous in okra variety Anmol as compared to variety Haseena as demonstrated by increasing RWC, MSI, K/Na ratio and activities of antioxidant enzymes. Our results suggested that zinc induced salt tolerance in Okra which can serve as a potential source to get sustainable production from salt-affected lands.

Marine actinomycetes from Malaysia marine environments with antagonistic potential

Marine actinomycetes have garnered the attention of researchers worldwide due to their ability to produce unique and novel bioactive compounds. This study aimed at assessing the diversity and antagonistic potential of marine actinomycetes isolated from Langkawi Island, Kedah and Tioman Island, Johor. In a total of 215 isolates were successfully recovered of which 52% were obtained from Starch–yeast Extract Agar (SYE), 31.4% from Marine Agar (MA) and 16.3% from Actinomycetes Isolation Agar. Fourteen isolates were found to be positive of Polyketide Synthase Type I (PKS-I) and/or Non-ribosomal Peptide Synthetases (NRPS) genes and these isolates were then subjected to antimicrobial evaluation test against 3 Gram-positive bacteria – Staphylococcus aureus, Methicillinresistant S. aureus, Bacillus subtilis; 4 Gram-negative bacteria – Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Serratia marcescens; and 2 fungi – Candida albicans, Candida parapsilosis. Most isolates were able to inhibit at least one test microorganism. There is, however, no direct correlation between the presence of the biosynthetic genes and antagonistic potential as demonstrated by the lack of antimicrobial activity though PKS-I and/or NRPS genes were present. Molecular identification using the 16S rRNA gene revealed 10 isolates belonging to the genus Streptomyces and each representative of the genera Actinomadura, Rhodococcus, Gordonia and Salinispora. Among the isolates, Streptomyces sp. T55 is a potent antibacterial actinomycete while Streptomyces sp. T109 is a good antifungal agent. Further characterization of marine actinomycetes was conducted using scanning electron microscopy, culture characteristics on several media (SYE, MA, Potato Dextrose Agar, ISP2, ISP3, ISP4, Czapek Agar), NaCl tolerance and carbon sources utilization profile using BIOLOG. Findings from this study demonstrate the potential of Malaysia’s marine environment as a new resource of actinomycetes with biosynthetic capabilities which can be further explored for the development of the natural product.