ABSTRACT
Antipathogenic therapy is an outcome of the quorum-sensing inhibition (QSI) mechanism, which targets autoinducerdependent virulent gene expression in bacterial pathogens. N-acyl homoserine lactone (AHL) acts as a key regulator in the production of virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1 and violacein pigment production in Chromobacterium violaceum. In the present study, the marine bacterial strain SS4 showed potential QSI activity in a concentration-dependent manner (0.5–2 mg/ml) against the AHL-mediated violacein production in C. violaceum (33–86%) and biofilm formation (33–88%), total protease (20–65%), LasA protease (59– 68%), LasB elastase (36–68%), pyocyanin (17–86%) and pyoverdin productions in PAO1. The light and confocal laser scanning microscopic analyses confirmed the reduction of the biofilm-forming ability of PAO1 when treated with SS4 extract. Furthermore, the antibiofilm potential was confirmed through static biofilm ring assay, in which ethyl acetate extract of SS4 showed concentration-dependent reduction in the biofilm-forming ability of PAO1. Thus, the result of this study clearly reveals the antipathogenic and antibiofilm properties of the bacterial isolate SS4. Through 16S rDNA analysis, the strain SS4 was identified as Bacillus sp. (GenBank Accession Number: GU471751).
ABSTRACT
A reliable and reproducible protocol for contamination free plant recovery system from alginated encapsulated uninodal microcuttings of micropropagated Bacopa monnieri L.have been developed after storage at 18oC for 45 days. Node segments excised from freshly micropropagated plants were encapsulated as single explant beads with 3.0 % sodium alginate and 80 mM CaCl2 2 H2O. To find out the optimal concentration of fungicide bavistin for efficient plant recovery, different concentrations of bavistin (1.0 - 15 mg l-1) were incorporated in to the encapsulation medium. 3.0 mg l-1 bavistin showed no reduction in plant conversion and generated maximum number of shoots (45.6 ± 1.69) at high frequency with out any contamination after storage up to 45 days at 18oC. At high concentrations (13 and 15 mg l-1), rupturing of calcium alginate coats after 8 - 9 days and gradual decline in the number of shoots indicates the toxic effect of bavistin on plant conversion. Encapsulated node cuttings stored up to 45 days regenerated shoots (5.2) and multiple shoots (45.6) in MS basal and hormone medium respectively. Maximum shoot length (8.2 ± 0.37 cm) was observed from encapsulsted node cuttings incorporated with 3.0 mg l-1 bavistin on MS basal medium. 90 % of the recovered plantlets were hardened off and successfully established in soil.