Salt-tolerant plant growth-promoting Pseudomonas atacamensis KSS-6 in combination with organic manure enhances rice yield, improves nutrient content and soil properties under salinity stress

In the current study salt tolerant-plant growth-promoting rhizobacteria (ST-PGPR) Pseudomonas atacamensis KSS-6, selected on the basis of prominent plant growth-promoting (PGP) and stress tolerance properties was tested as bioinoculant to improve yield of rice grown in saline soil. The ST-PGPR KSS-6 was capable of maintaining the PGP traits up to 200 mM NaCl, however, higher salt stress conditions affected these activities. The study was designed to determine the effect of developed talc-based bioformulation using KSS-6 along with organic manure (OM) on growth and yield of paddy under saline conditions. Bioformulation broadcasting was also done to examine the effect on soil properties. It was found that the combinatorial treatment showed positive impact on growth and yield of rice under saline conditions. Co-application of KSS-6 with OM showed maximum increment in growth, chlorophyll content, plant fresh weight, and dry weight as compared to untreated control plants. Furthermore, the combinatorial treatment improved the nutrient content (P, K, Zn, Fe, Mg, and Mn) by more than 35% and enhanced the biochemical parameters such as proline, flavonoids, carbohydrates, protein, dietary fiber, and antioxidant content of rice grains by more than 32%. Soil parameters including pH and electrical conductivity (EC), moisture content, total organic carbon, OM, sodium, and chloride ions were also improved upon treatment. There was significant lowering of EC from 7.43 to 4.3 dS/m when combination of OM and bacteria were applied. These findings suggest that the application of KSS-6 in the form of bioinoculant could be a promising strategy to mitigate negative impacts of salt stress and enhance the yield and nutritional properties of rice grown in degraded and saline soil.

POS0037 MULTIVARIABLE MENDELIAN RANDOMIZATION STUDY ON BMI-ADJUSTED LINK BETWEEN ADIPONECTIN AND RISK OF DEVELOPING RHEUMATOID ARTHRITIS

Background

Compelling evidence suggests that adiponectin is involved in the pathogenesis of rheumatoid arthritis (RA). Nevertheless, a recent Mendelian randomization (MR) study in Europeans has shown that adiponectin does not have a causal role in the development of RA1.

Objectives

As body-mass index (BMI) is a known risk factor for RA2 and subjects with high BMI have lower circulating levels of adiponectin, we specifically aimed to perform a multivariable MR in both European and East Asian populations to determine if adiponectin has a causal effect on RA development independently of BMI.

Methods

We performed a range of two-sample, univariable, MR analyses to assess the causal effect of adiponectin on RA in European and East Asian individuals. Two different sets (12 in Europeans and 5 in East Asians) of adiponectin-related genetic variants were used as instruments for genetically determined adiponectin levels, to calculate its causal effect on RA risk. Multivariable MR was performed to calculate the effect of adiponectin on RA risk after adjustment for BMI.

Results

Univariable MR did not provide evidence of a causal relationship between circulating adiponectin levels and RA risk in both European (OR 1.06; 95% CI 0.87-1.31; p=0.59) and East Asian (OR 1.04; 95% CI 0.91 – 1.19; p=0.54) individuals (Figure 1). Similarly, there was no evidence of a causal effect of adiponectin on RA in both European (OR 0.97; 95% CI 0.78 – 1.22; p=0.81) and East Asian (OR 0.97; 95% CI 0.72 – 1.31; p=0.85) populations after adding BMI as a confounder in the multivariable MR model (Figure 1).

Figure 1.

Forest plot of the causal effects of adiponectin-associated genetic variants on rheumatoid arthritis after adjustment for body mass index in a multivariable mendelian randomization (MR) analysis. Shown are European (EUR) and East Asian (EAS) populations. An Odds Ratio (OR) is a measure of association between an exposure and an outcome, in which the OR represents the likelihood that an outcome will occur given a particular exposure, compared to the likelihood of the outcome occurring in the absence of that exposure. Statistical analyses were performed with the use of inverse-variance weighted (IVW) estimate, MR-Egger regression weighted median analysis.

Conclusion

This MR study does not support a causal effect of genetically determined adiponectin levels on the risk of developing RA in both European and East Asian populations. By using multivariable MR to account for possible shared genetic predictors between circulating adiponectin levels and BMI we have shown that circulating adiponectin is not causally linked to RA risk after adjustment for BMI.

References

[1]Chen, H. et al. No Causal Association Between Adiponectin and the Risk of Rheumatoid Arthritis: A Mendelian Randomization Study. Frontiers in Genetics 12, doi:10.3389/fgene.2021.670282 (2021).

[2]Bae, S. C. & Lee, Y. H. Causal association between body mass index and risk of rheumatoid arthritis: A Mendelian randomization study. European journal of clinical investigation 49, e13076, doi:10.1111/eci.13076 (2019).

Acknowledgements

We would like to thank Maria Nethander, Jari Martikainen and Malin Östensson from the Bioinformatics Core Facility at the Sahlgrenska Academy for bioinformatics. We would also like to thank all study participants who agreed to have their DNA used for genetic testing and all the people involved in the study consortia who made their data publicly available.

Disclosure of Interests

None declared

POS0295 NO CAUSAL EFFECTS OF GENETICALLY DETERMINED SERUM URATE LEVELS ON THE RISK OF ALL-CAUSE AND SITE-SPECIFIC CANCER: A MENDELIAN RANDOMIZATION STUDY

Background:

Positive associations between urate levels and gout and the risk of some cancer types (urogenital, prostate, gastrointestinal and lung) have been reported in a number of observational studies; however, whether the relationship is causal remains uncertain.

Objectives:

The study aim was to evaluate a causal effect of genetically determined serum urate (SU) concentrations on cancer risks (overall and major cancer types) in individuals with European ancestry using Mendelian randomization (MR) analyses design.

Methods:

We used the individual-level data from two population-based Swedish cohorts including middle-aged subjects (mean follow-up = 21.2 years), Malmö Diet Cancer and Malmö Preventive Project (MDC/MPP), for one-sample MR setting. Data from a total of 17,597 individuals (n = 17,597 for SU at baseline, diagnoses during follow-up: 5659 for all-cause, 516 for bladder, 545 for lung, 791 for bowel, 1521 for prostate and 729 for breast cancer) was included. For two-sample MR, summary-statistic data for SU was obtained from Global Urate Genetic Consortium (GUGC: n = 110,347), while UK-Biobank data was employed for several major cancer outcomes (n = 36,815 for all-cause, 2,245 for bladder, 2,590 for lung, 4,488 for bowel, 6,474 for prostate and 10,274 for breast cancer). The definitions for cancer endpoints were matched for ICD9 and 10 codes between MDC/MPP and UK-Biobank cohorts. For both MR settings, a set of 26 urate-associated single nucleotide variants was selected to build-up the SU instrument (SU-instr) to test for a causal effect of SU on cancer outcomes. Statistical analysis, adjusted for age and sex, was done using multiple conventional MR methodologies and MR package in R (v4.0.2). A p < 0.05 was designated as statistically significant.

Results:

We found no causal effect of our SU-instr on neither all-cause nor site-specific cancer across all MR analyses (all p > 0.05). In MDC/MPP, SU-instr did not show a causal effect on the risk of all-cause [OR = 1.06, p = 0.32], bladder [OR = 0.96, p = 0.84], lung [OR = 1.26, p = 0.17], bowel [OR = 0.96, p = 0.81], prostate [OR = 1.05, p = 0.62], and breast [OR = 0.99, p = 0.98] cancer. Similar findings were made in the two-sample settings. Detailed results are provided in Table 1.

Conclusion:

Our MR study, using a series of causal inference approaches, does not support a causal effect of genetically determined SU for major cancer outcomes. There is no evidence to support changing SU levels by lifestyle or pharmacological intervention to attenuate the risk of major cancer types.

Table 1.

Results from a range of MR analyses for causal effect of SU on cancer risk in MDC/MPP (one-sample MR) and GUGC and UK-Biobank (two-sample MR) cohorts

One-sample MRCancer typeIVW2SLSGRSOR(95% CI)p-causalp-HetOR(95% CI)p-causalOR(95% CI)p-causalBladder0.96(0.68; 1.36)0.840.550.99(0.70; 1.42)0.990.94(0.67; 1.34)0.76Lung1.26(0.90; 1.77)0.170.891.29(0.91; 1.82)0.141.26(0.90; 1.77)0.17Bowel0.96(0.72; 1.28)0.810.440.95(0.72; 1.27)0.770.97(0.73; 1.28)0.83Prostate1.05(0.84; 1.31)0.620.841.04(0.83; 1.30)0.721.04(0.83; 1.30)0.69Breast0.99(0.74; 1.33)0.980.110.98(0.73; 1.32)0.920.98(0.73; 1.32)0.94All-cause1.06(0.93; 1.21)0.320.61.07(0.94; 1.21)0.281.07(0.94; 1.21)0.29Two-sample MRCancer typeIVWWeighted medianMR-EggerOR(95% CI)p-causalp-HetOR(95% CI)p-causalOR(95% CI)p-causalBladder1.02(0.88; 2.16)0.770.361.03(0.86; 2.10)0.71.03(0.83; 2.13)0.75Lung0.86(0.73; 1.08)0.070.040.86(0.73; 1.09)0.090.84(0.66; 1.16)0.15Bowel0.82(0.69; 1.02)0.03< 0.00010.89(0.78; 1.06)0.060.92(0.72;1.67)0.52Prostate1.00(0.91; 2.64)0.970.720.98(0.88; 2.17)0.770.94(0.83; 1.45)0.37Breast0.97(0.88; 1.95)0.670.00021.00(0.91; 2.70)0.990.95(0.81; 1.59)0.46All-cause0.96(0.90; 1.20)0.18< 0.00010.97(0.92; 1.23)0.210.93(0.86; 1.12)0.11

OR; odds ratio, 95% CI; 95% confidence interval, IVW; Inverse variance weighted method, 2SLS; two-stage least square, GRS; genetic risk score, p-Het; p-value for heterogeneity.

Disclosure of Interests:

None declared

Pseudomonas entomophila PE3 and its exopolysaccharides as biostimulants for enhancing growth, yield and tolerance responses of sunflower under saline conditions

Evaluation of plant growth promoting bacteria and the associated metabolites under saline conditions can be a potential eco-friendly remediation and productivity enhancement strategy. Salt-tolerant Pseudomonas entomophila PE3 was isolated from saline soil and screened for plant growth promoting (PGP) traits. The isolate produced indole acetic acid (IAA), gibberellic acid (GA), exopolysaccharides (EPS) and siderophore along with the potential to solubilize potassium (K), zinc (Zn) and phosphorus (P). Maximum stimulation of PGP attributes was recorded at 2% NaCl concentration. To determine the role of EPS, their composition was analyzed (at different salt concentrations) and comparison was done to determine the changes upon exposure to salinity. EPS was found to be rich in carbohydrates, proteins and phenolic compounds. The extracted EPS were also found to possess salt-tolerance properties including antioxidant, hydroxyl scavenging activity, reducing power, emulsification and flocculation potential, and Na⁺ accumulation ability. Interestingly, the salt tolerance properties of EPS were enhanced upon exposure to salinity (2% NaCl). Finally, EPS based bioformulation of isolate PE3 was checked through field assay in saline soil. With promising results on growth promotion and improved salinity tolerance attributes of inoculated sunflower plants, the bioformulation of PE3 amended with EPS can be a breakthrough for remediation of saline-agroecosystems.

Novel Bioformulations Developed from Pseudomonas putida BSP9 and its Biosurfactant for Growth Promotion of Brassica juncea (L.)

In this study, Pseudomonas putida BSP9 isolated from rhizosphere of Brassica juncea was investigated for its plant growth promoting and biosurfactant producing activities. The isolate showed the ability to produce indole acetic acid, siderophore, phosphate solubilization activity and was an efficient producer of biosurfactant. Purification (of the biosurfactant) by thin layer chromatography (TLC) and further characterization by Fourier transform infrared spectroscopy (FTIR) revealed that biosurfactant produced by the isolate belonged to the glycolipid category, which is largely produced by Pseudomonas sp. In addition, liquid chromatography-mass spectroscopy (LC-MS) analysis showed the presence of a mixture of six mono-rhamnolipidic and a di-rhamnolipidic congeners, confirming it as a rhamnolipid biosurfactant. Bioformulations were developed using BSP9 and its biosurfactant to check their impact on promoting plant growth in B. juncea. It was noted from the study that bioformulations amended with biosurfactant (singly or in combination with BSP9) resulted in enhancement in the growth parameters of B. juncea as compared to untreated control. Maximum increment was achieved by plants inoculated with bioformulation that had BSP9 plus biosurfactant. The study also suggested that growth promotion was significant up to a threshold level of biosurfactant and that further increasing the concentration did not further enhance the growth parameter values of the plant. The study proves that novel bioformulations can be developed by integrating plant growth promoting rhizobacteria (PGPR) and their biosurfactant, and they can be effectively used for increasing agricultural productivity while minimizing our dependence on agrochemicals.

Mechanisms of halotolerant plant growth promoting Alcaligenes sp. involved in salt tolerance and enhancement of the growth of rice under salinity stress

In the present study halotolerant bacteria were isolated from saline soil (EC ~ 11.9). Based on salt tolerance and plant growth promoting characteristics isolate AF7 was selected for further study. It was identified as Alcaligenes sp. on the basis of protein profiling and 16S rRNA sequence homology. Interestingly, AF7 showed diverse PGP characters at different salinity levels. While phosphate solubilization activity was expressed up to 300 mM NaCl, siderophore production was shown up to 700 mM, zinc solubilization up to 1000 mM and indole acetic acid (IAA), gibberellic acid (GA) and exopolysaccharides (EPS) production were depicted till 1400 mM. Correlative and regression analysis suggested positive relation between IAA, GA, EPS, siderophore production and zinc solubilization capability of AF7 and salinity up to 300 mM NaCl. EPS was found to be the most significant response and there was 263% increment in presence of 300 mM NaCl when compared to non-saline control. Analysis also showed that while growth promoting attributes were significant up to a threshold salinity level, further increasing the stress deviates the mechanism towards survival involving proline, antioxidant and hydroxyl scavenging activities. Combination of halotolerant AF7 and EPS showed more than twofold increase in the vegetative growth parameters of rice at ~ 170 mM NaCl (EC 9 dS/m). The study shows the mechanisms/metabolites of the plant growth promoting bacterium (PGPB) AF7 prominently involved during the salinity stress. Study also proves that novel bioformulations can be developed by integrative use of EPS and salt tolerant-PGPB which can be effective for saline soils.

Halo-tolerant plant growth promoting rhizobacteria for improving productivity and remediation of saline soils

Background

The collective impact of climate change and soil salinity is continuously increasing the degraded lands across the globe, bringing agricultural productivity and food security under stress. The high concentration of salts in saline soils impose osmotic, ionic, oxidative and water stress in plants. Biological solutions can be the most reliable and sustainable approach to ensure food security and limit the use of agro-chemicals.

Aim of Review

Halo-tolerant plant growth promoting rhizobacteria (HT-PGPR) are emerging as efficient biological tools to mitigate the toxic effects of high salt concentrations and improve the growth of plants, simultaneously remediating the degraded saline soils. The review explains the role of HT-PGPR in mitigating the salinity stress in plants through diverse mechanisms and concurrently leading to improvement of soil quality.

Key Scientific Concepts of Review

HT-PGPR are involved in alleviating the salinity stress in plants through a number of mechanisms evoking multipronged physiological, biochemical and molecular responses. These include changes in expression of defense-related proteins, exopolysaccharides synthesis, activation of antioxidant machinery, accumulation of osmolytes, maintaining the Na⁺ kinetics and improving the levels of phytohormones and nutrient uptake in plants. The modification of signaling by HT-PGPR inoculation under stress conditions elicits induced systemic resistance in plants which further prepares them against salinity stress. The role of microbial-mechanisms in remediating the saline soil through structural and compositional improvements is also important. Development of novel bioinoculants for saline soils based on the concepts presented in the review can be a sustainable approach in improving productivity of affected agro-ecosystems and simultaneously remediating them.

Nanoscale, tunable, and highly sensitive biosensor utilizing hyperbolic metamaterials in the near-infrared range

A plethora of research in recent years has been reported on biosensing in the surface plasmon resonant systems. However, very little research has reported a tunable and highly sensitive biosensor in a nanoscale platform. In this regard, we propose a nanoscale hyperbolic metamaterial (HMM)-based prism coupled waveguide sensor (PCWS) in the near-infrared range. The HMM layer makes up one of the constituents of the PCWS-comprised of a periodically arranged assembly of silver nanostrips. The structure is numerically simulated by the finite difference time domain method. It is demonstrated that the sensitivity of the reflected light can be tuned through the refractive index (RI) of the solution. Moreover, the effects of alteration of constituents of PCWS on the sensitivity have been analyzed. Results show that the sensitivity of PCWS can be harnessed by altering the thickness, slant angle of HMM layer, volume fraction (f) of metal in the HMM layer, and the incidence angle of light. For this purpose, the structure is numerically simulated by the finite difference time domain method. In the optimum design of the proposed sensor, the maximum value of sensitivity is achieved as high as S=3450  nm/refractive index unit with θ=10° and ϕ=10° and a metamaterial thickness of 250 nm. Moreover, the structure has a nanoscale footprint of 600  nm×400  nm×200  nm.

Isolation, Structure and Oxidative Fragmentation of 16-epi-19-S-Vindolinine – an Alkaloid from the Leaves of Catharanthus roseus

A new alkaloid has been isolated from the leaves of Catharanthus roseus. Spectroscopic and degradative studies have established its structure to be 16-epi-19-S-vindolinine

Application of whole cell protein analysis by SDS PAGE to establish the source of Salmonella typhimurium

Salmonella typhimurium isolated from an infant and the powder milk as well as from three different epidemiologically unrelated patients had the same biochemical reactions, antibiogram, serotype and all were non-typable by phage typing. The clonal nature of epidemiologically related isolates was established by SDS PAGE analysis.

Epidemiology of head lice infestation in school children at Peshawar, Pakistan

An epidemiological survey of head lice infestation among school children at Peshawar (Pakistan) was conducted from April to December 1986. Lice were detected by visual inspection and combing of the head. A total sample of 2287 students (1499 girls, 788 boys) aged 8-16 years from six schools revealed an overall prevalence of 46%, with girls showing a higher infestation rate (49%) than the boys (40%). The infestation in girls was more common in one of the three girls' schools surveyed, while in boys it did not differ significantly among different schools. The prevalence decreased as a linear function of age in both sexes. Pediculosis was directly related to hair length, and the rate of decrease with age was uniform in the three hair length categories compared. The infestation was directly related to crowding at home, and was negatively associated with dandruff. Like prevalence, the degree of infestation was higher in girls than in boys and decreased linearly with age in both sexes.

Prostaglandin associated mortality following intravenous injection of catfish epidermal secretions in rabbits

Toxicity of soluble protein extracts from epidermal gel secretions of the catfish, Arius thalassinus, was examined in rabbits. Intravenous injections containing doses as low as 2 mg protein/kg body weight caused mortality in all animals tested. An increase in plasma levels of thromboxane B2 (TXB2) and of 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) were observed following injections. Both the mortality and prostaglandin release were prevented by pretreatment of rabbits with either indomethacin or hydrocortisone. A similar indomethacin sensitive induction of prostaglandin release was noted following the in vitro treatment of arterial tissue sections with gel. Lethality appears to result from gel substances stimulating phospholipase activity to yield arachidonic acid, which is then metabolized to give toxic levels of prostaglandins.

Indole Alkaloids from Trachelospermum jasminoides

The leaves and stems of T. JASMINOIDES have been found to contain indole alkaloids. Five indole alkaloids, coronaridine, voacangine, apparicine, conoflorine, and 19-epi-voacangarine have been isolated. The (13)C-NMR spectra of apparicine and 19-epi-voacangarine are also reported.

Lipid composition of the epidermal gel secretion from the Arabian Gulf catfish (Arius thalassinus Ruppell)

Lipids associated with a threat induced epidermal gel secretion from the catfish, Arius thalassinus, have been analyzed. Phospholipids, neutral lipids and glycolipids are all present and each of these subclasses has been analyzed by thin layer and gas chromatography with a general similarity with membrane lipids being noted. The epidermal gel lipids differed from total liver lipids of the catfish. Fatty acid analysis showed the gel lipid to be rich in the unsaturated fatty acids: oleate (omega 7, C18:1), arachidonate (omega 6, C20:4), and docosahexaenoate (omega 3, C22:6). Some prostaglandins were quantitated in lipid extracts from the epidermal gel.

Toxic effects of the soluble skin secretion from the Arabian Gulf catfish (Arius thallasinus, Ruppell) on plasma and liver enzyme levels

Injection of skin toxin into the marginal ear vein of rabbits resulted in acute respiratory distress and convulsive movements, followed by death within 7 min. Significant increases in total plasma lactate dehydrogenase and the hepatic and cardiac derived isozymes and in glutamic-oxaloacetic and glutamic-pyruvic transaminase activities were observed in animals receiving toxin. Lower doses of toxin increase the survival time and enzyme levels in plasma. Skin toxin produces a time dependent toxic effect on the liver and heart.

Toxicity of flavoglaucin from Aspergillus chevalieri in rabbits

Female rabbits were injected intraperitoneally (i.p.) with purified flavoglaucin from Aspergillus chevalieri. After 2 h the rabbits were bled and the livers removed for enzyme assays. No changes were found for plasma lactate dehydrogenase (LDH) and its isozymes or liver transketolase (TK) activities. A small but not statistically significant increase was found in plasma glutamate pyruvate transaminase activity. A highly significant increase in plasma glutamic oxaloacetate transaminase activity was observed along with an increase in liver LDH which was, however, not quite significant. The liver also showed some histological evidence of hepatic damage.