Quorum sensing in bacteria of rice rhizospheres from Chhattisgarh, India.

Quorum sensing is a phenomena used by bacteria for regulation of some important characteristics coordinately. Gram-negative and Gram-positive bacteria, both utilize this system of communication, but they use different signal molecules for this, i.e. Gram-negative bacteria preferentially use acyl homoserine lactone (AHL). Rhizospheric soil is rich in bacterial diversity, with the presence of both types of bacteria. It will be useful if we know the quorum sensing based communications among bacteria present in rhizospheric soil. This work was undertaken with the idea to explore the diversity of AHL producing bacteria in soil. For this, bacteria were isolated from rice rhizosphere from field located in Dhamtari district of Chhattisgarh. To study quorum sensing, detection of AHL production was performed by colorimetry method. Out of total 29 bacterial isolates, only three Gram-negative bacteria showed positive result for AHLs production. These 3 isolates were selected for further study. The isolates were characterized by biochemical test. Other characteristics of these bacteria were also tested, like antibiotic resistance profile, indole test, and capability to biofilm formation, phosphate solubilization as well as their growth in different specific culture media. The Results suggest that AHLs producing bacteria may belong to family of Pseudomonas sp., which are reported in different researches to be part of the PGPR group of organisms. This work forms the base to study the cell-cell communication in plant rhizospheres.

A comparative study of antibacterial and antifungal activities of extracts from four indigenous plants.

A repetitive and wide use of chemical antibiotics has brought a serious threat in the biomedical and clinical sectors by the emergence of multidrug resistant pathogens. Plants have secondary metabolites that make them suitable candidate for natural antimicrobial agent without any side effect. In this study, we assessed comparative antibacterial and antifungal effects of extracts from four Indigenous plants (Nerium sp; Mentha sp; Aloe vera and Eucalyptus sp). Total phenolic and flavonoid content were extracted by microwave-assisted extractor and used for phytochemical assay. Antimicrobial experiment was done by micro dilution technique. A post hoc analysis inbuilt with one-way ANOVA test was used for the compilation of antibiotic sensitivity data and percent inhibition. Total phenolic content was significantly high in Mentha sp. and low in Nerium sp. (All p < 0.05). In antibacterial and antifungal activity higher concentrations of extracts showed a strong activity, which was as good as antibiotics used as control. Results from Eucalyptus sample showed a significant growth reducing capability even at lower concentrations. This study concludes that the plant extracts can be used to treat microbial infections with almost same efficacy as antibiotics and with a lower chance of resistance development.