Abstract:Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microorganisms. This study provides information on the occurrence of atrazine mineralizing bacterial strains with faster metabolizing ability. The enrichment cultures were tested for the biodegradation of atrazine by high-performance liquid chromatography (HPLC) and mass spectrometry. Nine cultures JS01.Deg01 to JS09.Deg01 were identified as the degrader of atrazine in the enrichment culture. The three isolates JS04.Deg01, JS07.Deg01, and JS08.Deg01 were identified as efficient atrazine metabolizers. Isolates JS04.Deg01 and JS07.Deg01 produced hydroxyatrazine (HA) N-isopropylammelide and cyanuric acid by dealkylation reaction. The isolate JS08.Deg01 generated deethylatrazine (DEA), deisopropylatrazine (DIA), and cyanuric acid by N-dealkylation in the upper degradation pathway and later it incorporated cyanuric acid in their biomass by the lower degradation pathway. The optimum pH for degrading atrazine by JS08.Deg01 was 7.0 and 16S rDNA phylogenetic typing identified it as Enterobacter cloacae strain JS08.Deg01. The highest atrazine mineralization was observed in case of isolate JS08.Deg01, where an ample amount of trzD mRNA was quantified at 72 h of incubation with atrazine. Atrazine bioremediating isolate E. cloacae strain JS08.Deg01 could be the better environmental remediator of agricultural soils and the crop fields contaminated with atrazine could be the source of the efficient biodegrading microbial strains for the environmental cleanup process.

Fresh, dried and powdered samples of leaf, stem and root of Acalypha indica were subjected to fractional distillation in a soxhlet apparatus using solvents such as hexane, chloroform, acetone and methanol. The plant extracts and a synthetic antifungal compound, Clotrimazole (authentic standard) were subjected to TLC and HPLC analyses. The R f (relative front) value of Clotrimazole was 0.371. The plant's leaf, root and stem extracts also gave distinct spots respectively at R f value of 0.371 ± 0.0009. In HPLC, the TLC-separated active compound and Clotrimazole resolved at 1.90 ± 0.2 min (retention time). The amounts of active compound present in root, leaf and stem extracts were 538, 415 and 171 lg/g respectively. From the results of our study, we infer that the active compound isolated from Acalypha indica is more potent in controlling Candida albicans, Aspergillus niger and Escherichia coli. The Active compound present in the plant had more than 100% activity when compared to standard Clotrimazole.

Herbal extracts play an essential role in treating various diseases. The threats in drug resistant pathogenic microbial strains can be prevented by the un-tapped medicinal principles from plants. The present study has been focused to search for powerful antimicrobial natural products from Dictyota acutiloba J. Ag. against human enteric pathogens and dermatophytic fungi. Chloroform and acetone extracts of Dictyota acutiloba exhibited antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA), methicillin susceptible Staphylococcus aureus (MSSA), Enterobacter sp., Pseudomonas aeruginosa MTCC741, Salmonella typhi MTCC733, Bacillus subtilis, Klebsiella pneumoniae MTCC109, Candida albicans and Aspergillus niger MTCC281. Purified compounds A 1 and C 1 by column chromatography, TLC and HPLC inhibited the gram positive, gram negative bacteria and fungi. MIC of C 1 and A 1 ranged between 0.5 and 0.9 lg ml -1 . The absorption maximum of C 1 and A 1 was 355 nm. Structural characterization of these purified molecules can lead to the new therapeutic molecule to fight the pathogenic microorganisms.

We established a soil-free culture capable of dechlorinating polychlorinated biphenyls (PCBs) in Kanechlor-300 and Kanechlor-400 by establishing a PCB-dechlorinating soil culture in liquid medium containing 0.5 mm glass beads. PCB-dechlorination activity in liquid cultures with glass beads appeared to depend on the size of the glass beads, and soil-free cultures with 0.05-, 1.0- or 2.0 mm glass beads did not dechlorinate PCBs. Soil-free culture without glass beads also failed to dechlorinate PCBs. The soil-free culture containing 0.5 mm glass beads dechlorinated 42.6 ± 12.0 mol% in total PCBs. This soil-free culture was more effective than soil culture for dechlorinating PCBs ranging from dichlorinated PCBs to tetrachlorinated PCBs. Clone analysis of the 16S rRNA gene sequences showed that one of the predominant groups of microorganisms in the soil-free culture comprised heat-tolerant and spore-forming bacteria from the phylum Firmicutes. Heat treatment (100 °C, 10 min) did not destroy the PCB-dechlorination activity of the soil-free culture with glass beads. These results suggest that unknown species of the phylum Firmicutes were involved in PCB dechlorination in the soil-free culture. In this study, we succeeded in using a liquid medium containing glass beads as an inorganic soil substitute and showed that such a medium enhances PCB-dechlorination activity. Our study provides valuable information for developing PCB-bioremediation techniques using dechlorinating bacteria in anoxic contaminated soils and sediments.

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