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Degradation study of lindane by novel strains Kocuria sp. DAB-1Y and Staphylococcus sp. DAB-1W.

ABSTRACT:

Background

This study was carried out to isolate and characterize the bacterial strains from lindane-contaminated soil and they were also assessed for their lindane-degrading potential.

Methods

In this study the enrichment culture method was used for isolation of lindane degrading bacterial isolates, in which the mineral salt medium (MSM) supplemented with different concentrations of lindane was used. Further, the screening for the potential lindane degrading isolates was done using the spray plate method and colorimetric dechlorinase enzyme assay. The selected isolates were also studied for their growth response under varying range of temperature, pH, and NaCl. The finally selected isolates DAB-1Y and DAB-1W showing best lindane degradation activity was further subjected to biochemical characterization, microscopy, degradation/kinetic study, and 16S rDNA sequencing. The strain identification were performed using the biochemical characterization, microscopy and the species identifies by 16S rDNA sequence of the two isolates using the standard 16S primers, the 16 S rRNA partial sequence was analyzed through BLAST analysis and phylogenetic tree was generated based on UGPMA clustering method using MEGA7 software. This shows the phylogenetic relationship with the related strains. The two isolates of this study were finally characterized as Kocuria sp. DAB-1Y and Staphylococcus sp. DAB-1W, and their 16S rRNA sequence was submitted to GenBank database with accession numbers, KJ811539 and KX986577, respectively.

Results

Out of the 20 isolates, the isolates DAB-1Y and DAB-1W exhibited best lindane-degrading activity of 94 and 98%, respectively, recorded after 8 days of incubation. The optimum growth was observed at temperature 30 °C, pH 7, and 5% NaCl observed for both isolates. Of the four isomers of hexachlorocyclohexane, isomer α and γ were the fastest degrading isomers, which were degraded up to 86 and 94% by isolates DAB-1Y and up to 93 and 98% by DAB-1W, respectively, reported after 8 days incubation. Isomer β was highly recalcitrant in which maximum 35 and 32% lindane degradation was observed even after 28 days incubation by isolates, DAB-1Y and DAB-1W, respectively. At lower lindane concentrations (1-10 mg/L), specific growth rate increased with increase in lindane concentration, maximum being 0.008 and 0.006/day for DAB-1Y and DAB-1W, respectively. The 16 S rRNA partial sequence of isolate DAB-1Y showed similarity with Kocuria sp. by BLAST analysis and was named as Kocuria sp. DAB-1Y and DAB-IW with Staphylococcus sp. DAB-1W. The 16S rDNA sequence of isolate DAB-1Y and DAB-1W was submitted to online at National Centre of Biotechnology Information (NCBI) with GenBank accession numbers, KJ811539 and KX986577, respectively.

Conclusions

This study has demonstrated that Kocuria sp. DAB-1Y and Staphylococcus sp. DAB-1W were found efficient in bioremediation of gamma-HCH and can be utilized further for biodegradation of environmental contamination of lindane and can be utilized in bioremediation program.

SUBMITTER: Kumar D

PROVIDER: S-EPMC5196013 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Fungi are usually involved in degradation/deterioration of many anthropogenic wastes due to their verse enzyme secretions and adaptive capabilities. In this study, five dominant fungal strains were isolated from an aged lindane polluted site, they were all mixed (100 mg each) together with pent mushroom compost (SMC) and applied to lindane polluted soil (5 kg) at 10, 20, 30, 40% and control 0% (soil with no treatment), these were used to grow M. maximus Jacq for 3 months. To establish lindane degradation, deductions such as Degradation rate (K1), Half-life (t1/2) and Degradation efficiency (DE) were made based on the analyzed lindane concentrations before and after the experiment. We also tested the presence and expressions of phosphoesterases (mpd and opd-A) and catechol 1,2-dioxygenases (efk2 and efk4) genes in the strains. The stains were identified as Aspergillus niger (KY693970); Talaromyces atroroseus (KY488464), Talaromyces purpurogenus (KY488468), Yarrowia lipolytica (KY488469) and Aspergillus flavus (KY693973) through morphological and molecular methods. Combined rhizospheric action of M. maximus and fungi speed up lindane degradation rate, initially detected lindane concentration of 45 mg/kg was reduced to 11.26, 9.34 and 11.23 mg/kg in 20, 30 and 40% treatments respectively making 79.76, 85.93 and 88.67% degradation efficiencies. K1 of 1.29 was recorded in control while higher K1 of 1.60, 1.96 and 2.18 /day were recorded in 20, 30 and 40% treatments respectively. The best t1/2 of 0.32 and 0.35 /day were recorded in 40 and 30% compared to control (0.54 /day). All the strains were also affirmed to possess the tested genes; opd was overexpressed in all the strains except KY693973 while mpd was overexpressed in KY693970, KY488464 but moderately expressed in KY488468, KY488469 and KY693973. However, efk genes were under-expressed in most of the strains except KY488469 and KY693973 which showed moderate expression of efk4. This work suggests that the synergistic association of the identified rhizospheric fungi and M. maximus roots could be used to remove lindane in soil at a limited time period and this combination could be used at large scale.