Antimicrobial and Antioxidant Property of a True Mangrove Rhizophora apiculata Bl.

Mangroves are abundant in bioactive natural substances that fight off pathogenic diseases. Different parts of R. apiculata, an abundant mangrove found in Bhitarkanika National Park, India were extracted with methanol and a mixture of solvents methanol/ethanol/chloroform (60 : 20 : 20) to evaluate their antimicrobial properties. The combination solvent extract of bark had the highest zone of inhibition (ZOI) of 18.62 mm against Pseudomonas aeruginosa and a ZOI of 17.41 mm against Streptococcus mitis. Bark extracts had the highest DPPH (43 %) and FRAP (96 %) activities. The combination solvent bark extract of R. apiculata had the highest ZOI of 20.42 mm (lowest MIC of 2.12 µg/ml) against Candida albicans and ZOI of 15.33 mm (MIC of 3.02 µg/mL) against Penicillium chrysogenum. Combination bark extracts of R. apiculata contained flavanols than methanolic extracts. The crude extract of R. apiculata bark made with a mixture of solvents containing more active ingredients could be used in novel drug formulation.

Synergistic effect of Bacillus and Rhizobium on cytological and photosynthetic performance of Macrotyloma uniflorum (Lam.) Verdc. Grown in Cr (VI) contaminated soil.

Macrotyloma uniflorum (horse gram) is considered an under-utilized legume crop despite its nutritional and medicinal values. In India, it has wide acceptance among farming communities. This investigation emphasized on the possible application of two endosymbionts (Bacillus sp. AS03 and Rhizobium sp. AS05) of horse gram cultivated on Cr (VI)-contaminated soil. The photosynthetic performance (PIφ) of Cr treated plants co-inoculated with AS03 and AS05 was significantly improved compared with non-inoculated Cr treated plants based on photosynthetic yield, which was evidenced from the rise in the fluorescence at I-P transient and rate of photosynthesis (pN), indicating synergistic action between plant and bacteria (AS03 and AS05). The smooth electron transport from PS II to PS I was achieved in the Cr stressed plants inoculated with both the bacterial strains. The detrimental effects of Cr toxicity on the root tips were also minimized with bioinoculation as revealed from mitotic index. Plants with dual inoculation of AS03 and AS05 had significantly lesser chromosomal aberration in the roots. Dual inoculation biochar or seed inoculation have beneficial impact on the plant photosynthetic performance along with improved growth of roots in plants treated with Cr (VI). The results of the current work suggest the possitive effect of dual inoculation of Cr tolerant endosymbionts, Bacillus sp. (AS03) and nodulating Rhizobium sp. (AS05), in reducing cytological as well as physiological stress of plants in Cr (VI) contaminated soil.

AM fungi mediated bioaccumulation of hexavalent chromium in Brachiaria mutica-a mycorrhizal phytoremediation approach.

The experiment was designed to evaluate the roles of Rhizophagus irregularis on chlorophyll fluorescence and chromium bioaccumulation in a grass species (Brachiaria mutica) by supplementing Cr+6 at different concentrations. Arbuscular Mycorrhizal Fungi (AMF) association facilitated lessening of chromium level in contaminated soil and enhanced chromium bioavailability in Brachiaria mutica. The mycorrhizal inoculated increased the chlorophyll (0.925 mg/g), carotenoid (0.127 mg/g), protein (2.883 mg/g), proline (0.889 mg/g) contents and activities of antioxidant enzymes like catalase, ascorbate peroxidase and glutathione peroxidase. The mycorrhizal inoculated plants also showed enhanced overall photosynthetic performance (PIϕ = 2.473) and enhanced PS-II to PS-I electron transport as evident from yield parameter (0.712) and TR0/RC (2.419) for 60 mg/kg Cr+6 treatment. The observations suggest that AMF association could defend the plants from chromium stress by elevating the number of antioxidants in plants. Rhizophagus irregularis was found to maintain a successful symbiotic relationship with Brachiaria mutica in chromium contaminated soil. The observations recommended that Rhizophagus irregularis in association with Brachiaria mutica would be an innovative approach for decontamination of Cr+6.