Biodegradation of carbofuran by Pseudomonas aeruginosa S07: biosurfactant production, plant growth promotion, and metal tolerance.

Pesticides are an indispensable part of modern farming as it aids in controlling pests and hence increase crop yield. But, unmanaged use of pesticides is a growing concern for safety and conservation of the environment. In the present study, a novel biosurfactant-producing bacterium, Pseudomonas aeruginosa S07, was utilized to degrade carbofuran pesticide, and it was obtained at 150 mg/L concentration; 89.2% degradation was achieved on the 5th day of incubation in in vitro culture condition. GC-MS (gas chromatography and mass spectrometry) and LC-MS (liquid chromatography and mass spectrometry) analyses revealed the presence of several degradation intermediates such as hydroxycarbofurnan, ketocarbofuran, and hydroxybenzofuran, in the degradation process. The bacterium was found to exhibit tolerance towards several heavy metals: Cu, Co, Zn, Ni, and Cd, where maximum and least tolerance were obtained against Co and Ni, respectively. Additionally, the bacterium also possesses plant growth-promoting activity showing positive results in nitrogen fixation, phosphate solubilising, ammonia production, and potassium solubilizing assays. Thus, from the study, it can be assumed that the bacterium can be useful in the production of bioformulation for remediation and rejuvenation of pesticide-contaminated sites in the coming days.

Mustard seed–associated endophytes suppress Sclerotinia sclerotiorum causing Sclerotinia rot in mustard crop / Los endófitos asociados a la semilla de mostaza suprimen Sclerotinia sclerotiorum causando la pudrición de Sclerotinia en el cultivo de mostaza

Mustard-rapeseed cultivation is affected by Sclerotinia sclerotiorum resulting in loss of oil yield and degradation of crop quality. This study adopted an environment friendly biocontrol approach of screening mustard endophytes against the pathogen. Two bacterial isolates, Bacillus safensis (TS46 bac4) and Bacillus australimaris (SM2) showed potential biocontrol activity under both in vitro and in vivo conditions. Dual culture assay reported 90% inhibition of fungal growth. The bacterial cell free supernatant of isolate SM2 showed 52.89% inhibition and the other isolate TS46 bac4 showed 57.97% inhibition. The crude (10 mg/ml) and purified (10 mg/ml) metabolite extract of SM2 showed 100% and 97% inhibition respectively. Both crude (10 mg/ml) and purified (7.5 mg/ml) metabolite extract of TS46 bac4 exhibited 99% inhibition of the pathogen. Antifungal lipopeptides: surfactin, iturin and fengycin were identified in bacterial metabolite extract of the isolates. Both strains promoted healthy germination and prevented the formation of any disease symptoms in seedling. The selected Bacillus strains applied by spray method showed better results against fungal infection on mustard leaf and stem. Microscopic studies revealed degradation of fungal mycelial growth by both isolates. These findings support the employment of the bacterial strains as potential biocontrol agents to reduce the effects of S. sclerotiorum in mustard-rapeseed.(AU)

A biosurfactant-producing novel bacterial strain isolated from vermicompost having multiple plant growth-promoting traits.

The nutrient-rich vermicompost which is used as manure for the growth and development of plants is rich in microbial flora. These microbes protect the plants against several infectious pathogenic microbes. As certain microbes are known to produce biosurfactants as metabolites, an investigation was carried out to isolate biosurfactant-producing bacterial strains from vermicompost with the efficient antifungal property. From the study, it was revealed that biosurfactant-producing bacterial strains are present in the vermicompost. A total of nine bacterial strains were isolated from the vermicompost. Among them, one most efficient biosurfactant-producing bacterial strains with antifungal properties have been screened. After molecular characterization of the isolated strain, it was revealed that the bacterial strain is Bacillus licheniformis strain SCV1. The strain produces 3.4 ± 0.1 g/L of crude biosurfactant, which when column purified yields 3.1 ± 0.1 g/L of biosurfactant. The biosurfactant exhibited excellent emulsifying activity (E24 ) of 96.56% against crude oil. The produced biosurfactant was identified as a lipopeptide consisting of a mixer of surfactin and iturin. Furthermore, the biosurfactant exhibited significant antifungal activity against a wide range of phytopathogens, showing 76.3% inhibition against Sclerotinia sclerotiorum, 53% inhibition against Colletotrichum gloeosporioides, 51% against Fusarium verticillioides, and 36% against Corynespora cassicolla. Along with antifungal activities, the stain was found to exhibit multiple plant growth-promoting traits. This study, thus indicates that vermicompost might contain biosurfactant-producing microbes which can render protection to the plant against various phytopathogens by the production of biosurfactants and can also stimulate plant growth.

Wound healing efficacy of rhamnolipid-coated zinc oxide nanoparticle along with its in vivo antibacterial efficacy against Staphylococcus aureus.

Rhamnolipids are microbial metabolites with antibacterial efficacies, which can be further boosted through the application of nanobiotechnology. In this study, the efficacy of rhamnolipid-coated zinc oxide nanoparticles (ZnRL) has been studied for their wound healing efficacy as well as in vivo antibacterial efficacy. Thus, this study evaluates the efficacy of ZnRL to heal an excised infected wound, which was compared with the healing efficacy of rhamnolipid and clindamycin. The study revealed that rhamnolipid-coated zinc oxide nanoparticles possess promising wound healing efficacy with prominent antibacterial activity in the rat model. Prominent wound healing in a Staphylococcus aureus infected excised wound was observed on the 5th day of the treatment when the wound site was treated with 100 µl of 0.5 mg/ml of ZnRL. This concentration of ZnRL was found to exhibit efficient antibacterial activity against the pathogen, thereby decreasing the amount of pathogen in the wound site. ZnRL exhibited efficient wound contraction, thereby decreasing the size of the wound prominently in 5 days. Histological study revealed efficient tissue remodelling in ZnRL-treated skin which resulted in rapid formation of the epidermis and recruitment of various dermal cells within the 5th day of treatment. The study also revealed the non-cytotoxic effect of the nanoparticles in fibroblast cell line L929 and the non-haemolytic effect against blood cells, indicating its potential in pharmaceuticals.

Mustard seed-associated endophytes suppress Sclerotinia sclerotiorum causing Sclerotinia rot in mustard crop.

Mustard-rapeseed cultivation is affected by Sclerotinia sclerotiorum resulting in loss of oil yield and degradation of crop quality. This study adopted an environment friendly biocontrol approach of screening mustard endophytes against the pathogen. Two bacterial isolates, Bacillus safensis (TS46 bac4) and Bacillus australimaris (SM2) showed potential biocontrol activity under both in vitro and in vivo conditions. Dual culture assay reported 90% inhibition of fungal growth. The bacterial cell free supernatant of isolate SM2 showed 52.89% inhibition and the other isolate TS46 bac4 showed 57.97% inhibition. The crude (10 mg/ml) and purified (10 mg/ml) metabolite extract of SM2 showed 100% and 97% inhibition respectively. Both crude (10 mg/ml) and purified (7.5 mg/ml) metabolite extract of TS46 bac4 exhibited 99% inhibition of the pathogen. Antifungal lipopeptides: surfactin, iturin and fengycin were identified in bacterial metabolite extract of the isolates. Both strains promoted healthy germination and prevented the formation of any disease symptoms in seedling. The selected Bacillus strains applied by spray method showed better results against fungal infection on mustard leaf and stem. Microscopic studies revealed degradation of fungal mycelial growth by both isolates. These findings support the employment of the bacterial strains as potential biocontrol agents to reduce the effects of S. sclerotiorum in mustard-rapeseed.

Synthesis, characterization, and evaluation of antibacterial efficacy of rhamnolipid-coated zinc oxide nanoparticles against Staphylococcus aureus.

The antimicrobial efficacy of rhamnolipid is well established against a wide range of pathogens. However little is known about the enhancement of antimicrobial efficacy of rhamnolipid in the form of nanoparticles. With a curiosity of enhancing antimicrobial activity, a study has been carried out to evaluate the antimicrobial efficacy of rhamnolipid-coated zinc oxide nanoparticles. The zinc oxide nanoparticles were synthesized with rhamnolipid, produced by Pseudomonas aeruginosa JS29. The rhamnolipid-coated zinc oxide nanoparticles were characterized by FTIR, XRD, TGA, TEM, and SAED. The antimicrobial and antibiofilm efficacy of the nanoparticles was evaluated against Staphylococcus aureus MTCC 96. FTIR, XRD, TEM, and SAED analyses confirmed that the nanoparticles contain both rhamnolipid and zinc as constituents and are polycrystalline with sizes ranging from 40 to 50 nm. At a concentration of 250 µg/ml, rhamnolipid-coated zinc oxide nanoparticles exhibited 80% growth inhibition of the pathogen. Again, at the same concentration, the nanoparticle was observed to inhibit 78% of biofilm formation while disrupting 100% of preformed biofilm. The nanoparticles demonstrated an enhanced inhibitory and antibiofilm efficacy against the pathogen compared to the individual effect of both rhamnolipid and zinc oxide nanoparticles. With the established non-toxicity of rhamnolipid-coated zinc oxide nanoparticles in fibroblast cell lines, the nanoparticles could be a promising pharmaceutical alternative.