Antifungal potential of Azotobacter species and its metabolites against Fusarium verticillioides and biodegradation of fumonisin

AIMS

In the study, seven Plant Growth Promoting Rhizobacteria (PGPR) Azotobacter species were screened against three strains of Fusarium verticillioides to test its antifungal activity. Azotobacter strains were tested for the degradation of fumonisin produced by F. verticillioides. Secondary metabolites were isolated and characterized from the Azotobacter strains for the first time.

METHODS AND RESULTS

Potential seven Azotobacter species antifungal activity was tested following the dual culture assay against three starins of Fusarium verticillioides namely FVM-42, FVM-86, MTCC156 estimating the substantial zone of inhibition. Azotobacter species AZT-31 and AZT-50 strains significantly inhibited the growth of F. verticillioides recording drastic growth enhancement of maize under in-vitro conditions by calculating the infection incidence, vigour index and germination percentage. As confirmation, dereplication studies were conducted for the reconfirmation of Azotobacter strains by isolating from rhizoplane. Azotobacter strains played a key role in degradation of fumonisin produced by F. verticillioides reporting 98% degradation at 2hr of incubation with the pathogen. Furthermore, in the study first time we have tried to isolate and characterize the secondary metabolites from the Azotobacter strains exhibiting six compounds from the species AZT-31 (2) and AZT-50 (4). Preliminary in-vitro experiments were carriedout using the compounds extracted to check the reduction of infection incidence (90%) and increase in germination percentage upto 50 to 70% when compared to test pathogen.

CONCLUSION

Azotobacter strains referred as PGPR on influencing the growth of plant by producing certain substances that acts as stimulators on inhibiting the growth of pathogen.

SIGNIFICANCE AND IMPACT OF THE STUDY

Future perspective would be the production of active combination of carboxamide compound and Azotobacter species for preventively controlling the phytopathogenic fungi of plants and crops and also towards the treatment of seeds.

Probiotic Properties of Lactic Acid Bacteria Isolated From Neera: A Naturally Fermenting Coconut Palm Nectar

Probiotic bacteria were isolated from different traditional fermented foods as there are several such foods that are not well explored for their probiotic activities. Hence, the present study was conducted to find the potential of lactic acid bacteria (LAB) as probiotics that were isolated from the sap extract of the coconut palm inflorescence - Neera, which is a naturally fermented drink consumed in various regions of India. A total of 75 isolates were selected from the Neera samples collected aseptically in the early morning (before sunrise). These isolates were initially screened for cultural, microscopic, and biochemical characteristics. The initial screening yielded 40 Gram-positive, catalase-negative isolates that were further subjected to acid - bile tolerance with resistance to phenol. Among 40 isolates, 16 survived screening using analysis of cell surface hydrophobicity, auto aggregation with adhesion to epithelial cells, and gastric-pancreatic digestion for gastrointestinal colonization. The isolates were also assessed for antimicrobial, antibiotic sensitivity, and anti-oxidative potential. The safety of these isolates was evaluated by their hemolytic and deoxyribonuclease (DNase) activities. Based on these results, seven isolates with the best probiotic attributes were selected and presented in this study. These LAB isolates, with 51.91-70.34% survival at low pH, proved their resistance to gastric conditions. The cell surface hydrophobicity of 50.32-77.8% and auto aggregation of 51.02-78.95% represented the adhesion properties of these isolates. All the seven isolates exhibited good antibacterial and antifungal activity, showing hydroxyl-scavenging activity of 32.86-77.87%. The results proved that LAB isolated from Neera exhibited promising probiotic properties and seem favorable for use in functional fermented foods as preservatives.

Lactobacillus plantarum MYS6 Ameliorates Fumonisin B1-Induced Hepatorenal Damage in Broilers

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium species is a predominant Group 2B carcinogen occurring in maize and maize-based poultry feeds. It is shown to be nephrotoxic, hepatotoxic, neurotoxic, and immunosuppressing in animals. In this study, we report the ameliorating effects of a probiotic strain, Lactobacillus plantarum MYS6 on FB1-induced toxicity and oxidative damage in broilers. A 6-week dietary experiment consisting of 48 broilers was performed in six treatment groups. Probiotic treatment (10⁹ cells/mL) involved pre-colonization of broilers with L. plantarum MYS6 while co-administration treatment involved supplementation of probiotic and FB1-contaminated diet (200 mg/Kg feed) simultaneously. At the end of the treatment period, growth performance, hematology, serum biochemistry, and markers of oxidative stress in serum and tissue homogenates were evaluated in all the broilers. The histopathological changes in hepatic and renal tissues were further studied. The results demonstrated that administration of L. plantarum MYS6 efficiently improved the feed intake, body weight and feed conversion ratio in broilers. It mitigated the altered levels of hematological indices such as complete blood count, hemoglobin, and hematocrit. Serum parameters such as serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, creatinine, cholesterol, triglycerides, and albumin were significantly restored after administering the probiotic in FB1-intoxicated broilers. Additionally, L. plantarum MYS6 alleviated the levels of oxidative stress markers in serum and tissue homogenate of liver. The histopathological data of liver and kidney further substantiated the overall protection offered by L. plantarum MYS6 against FB1-induced cellular toxicity and organ damage in broilers. Our results indicated that co-administration of probiotic along with the toxin had better effect in detoxification compared to its pre-colonization in broilers. Collectively, our study signifies the protective role of L. plantarum MYS6 in ameliorating the FB1-induced toxicity in the vital organs and subsequent oxidative stress in broilers. The probiotic L. plantarum MYS6 can further be formulated into a functional feed owing to its anti-fumonisin attributes and role in mitigating FB1-induced hepatorenal damage.