Elimination of plasmids pKM 101 and F'lac from Salmonella typhimurium and Escherichia coli by bisammonium salt. The effect of outer membrane pattern

Role of Plasmid in Pesticide Degradation and Metal Tolerance in Two Plant Growth-Promoting Rhizobacteria Bacillus cereus (NCIM 5557) and Bacillus safensis (NCIM 5558)

Disha A (Bacillus cereus) and Disha B (Bacillus safensis) were isolated from pesticide-infested agricultural field and showed tolerance against pesticides, heavy metals, and antibiotics. The isolates exhibited PGPR activities in vitro as well as in field conditions in lentil (Lens culinaris) and cow pea (Vigna unguiculata). Both the Bacillus species could not be grown in mineral salt medium but efficiently grown in the media supplemented with pesticide (imidacloprid/carbendazim) demonstrating the utilization of pesticide as carbon/nitrogen source. The HPLC studies exhibited the pesticide (imidacloprid/carbendazim) degradation by both the bacteria. B. safensis showed better degradation of carbendazim (88.93%) and imidacloprid (82.48%) than that of B. cereus 78.07% and 49.12%, respectively. The bacterial isolates showed high concentration of heavy metal tolerance viz. lead, molybdenum, cadmium, copper, cobalt, and zinc, except mercury. Both the bacteria possessed single plasmid. The plasmid-cured isolates of B. cereus did not tolerate any pesticide, whereas that of B. safensis tolerated all the pesticides, like wild strains. The plasmid curing experiments did not affect the heavy metal tolerance ability of both the bacteria indicating the genomic nature of heavy metal tolerance genes, whereas pesticide resistance genes are plasmid-dependent in B. cereus but genomic in B. safensis.

Condensed lamellar phase in ternary DNA-DLPC-cationic gemini surfactant system: a small-angle synchrotron X-ray diffraction study

We report on a small-angle synchrotron X-ray diffraction study of dilauroylphosphatidylcholine (DLPC) liposomes aggregated with high molecular DNA in the presence of 1,4-butanediammonium-N,N'-dilauryl-N,N,N',N'-tetramethyl gemini surfactant cations (C12GS). The aggregates prepared at the DLPC/C12GS/DNA phosphate group=2:1:1.6 molar ratio in 0.0015 mol x l(-1) NaCl aqueous solution exhibit Bragg reflections due to lamellar lipid bilayer stacking and the Bragg reflection typical of one-dimensional DNA lattice with parallel strands intercalated between lipid bilayers. In this condensed fluid lamellar L(alpha)(c) phase, the interactions between DNA and charged bilayers damp the thermally induced bilayer undulations. The diffraction data obtained with the mixture of DLPC liposomes and DNA (at DNA phosphate group/DLPC=0.8:1 molar ratio) indicate a DNA-lipid interaction in the absence of C12GS.

Antimicrobial efficacy of quaternary bisammonium salts and the effect of their sub-MICs on Pseudomonas aeruginosa virulence factors

Antipseudomonadal activity of homologous series of six quaternary bisammonium salts (QBAS) (4,7-dioxo-3,8-dioxadekan-1,1-[bis(alkyldimethyldiammonium dibromide)] as well as the effect of their subinhibitory concentrations (sub-MICs) on Pseudomonas aeruginosa virulence factors was studied. Antibacterial activity of QBAS increased up to a certain length of the chain and then decreased with further elongation. All the tested sub-MICs of QBAS caused a significant suppression of phospholipase C activity (to 0-41%). Elastase and proteinase activity were less efficiently reduced. A more effective decrease of these activities was only found after treatment with one-fourth of the MICs of the tested substances. QBAS caused only an erratic decrease of alginate production.