Role of Microorganisms in Emission of Nitrous Oxide and Methane in Pulse Cultivated Soil Under Laboratory Incubation Condition

Soil from a pulse cultivated farmers land of Odisha, India, have been subjected to incubation studies for 40 consecutive days, to establish the impact of various nitrogenous fertilizers and water filled pore space (WFPS) on green house gas emission (N₂O & CH₄). C₂H₂ inhibition technique was followed to have a comprehensive understanding about the individual contribution of nitrifiers and denitrifiers towards the emission of N₂O. Nevertheless, low concentration of C₂H₂ (5 ml: flow rate 0.1 kg/cm²) is hypothesized to partially impede the metabolic pathways of denitrifying bacterial population, thus reducing the overall N₂O emission rate. Different soil parameters of the experimental soil such as moisture, total organic carbon, ammonium content and nitrate–nitrogen contents were measured at regular intervals. Application of external N-sources under different WFPS conditions revealed the diverse role played by the indigenous soil microorganism towards green house gas emission. Isolation of heterotrophic microorganisms (Pseudomonas) from the soil samples, further supported the fact that denitrification might be prevailing during specific conditions thus contributing to N₂O emission. Statistical analysis showed that WFPS was the most influential parameter affecting N₂O formation in soil in absence of an inhibitor like C₂H₂.     

Antimicrobial activity and molecular characterization of an endophytic fungus, Quambalaria sp. isolated from Ipomoea carnea

An endophytic fungus displaying considerable antimicrobial activity was isolated from stem tissue of an invasive plant species, Ipomoea carnea. The fungus was identified as Quambalaria sp. and confirmed by ITS rDNA sequence analysis. A BLAST search result of the sequence indicated 97 % homology with Quambalaria cyanescens. Crude metabolites of the fungus showed considerable antimicrobial activity against a panel of clinically significant microorganisms. The metabolites showed highest in vitro activity against Shigella dysenteriae followed by Escherichia coli and Candida albicans. Optimum metabolites production required neutral pH and a 15-day incubation period. Bark extracts amended with fungal media demonstrated higher antimicrobial activity. Optimum metabolites activity was recorded in Czapek Dox broth amended with leaf extracts (CDB + LE) of the host plant. The metabolites showed UV λ-max in ethyl acetate at 284.6 nm with an absorbance value of 1.093. Phylogenetic tree generated by the Maximum Parsimony method showed clustering of our isolate with Q. cyanescens with supported bootstrap of 65 %. Species of Quambalaria are pathogens to Eucalyptus and occurrence of this fungus as endophytes support it to be a latent pathogen. Sequence base analysis and RNA secondary structure study also confirmed such a relationship. Secondary structural features like two hinges and a 5’ dangling end were found to be unique to our isolate. These structural features can also be used as potential barcodes for this fungus. The findings indicate that invasive plant species can be a reliable source of novel endophytes with rich antimicrobial metabolites. The study also validates the assumption that endophytes can become parasites and share a close affinity.