Identification and characterization of integron mediated antibiotic resistance in pentachlorophenol degrading bacterium isolated from the chemostat

A bacterial consortium was developed by continuous enrichment of microbial population isolated from sediment core of pulp and paper mill e uent in mineral salts medium (MSM) supplemented with pentachlorophenol (PCP) as sole source of carbon and energy in the chemostat. The consortia contained three bacterial strains. They were identified as Escherichia coli, Pseudomonas aeruginosa and Acinetobacter sp. by 16S rRNA gene sequence analysis. Acinetobacter sp. readily degraded PCP through the formation of tetrachloro-phydroquinone (TecH), 2-chloro-1,4-benzenediol and products of ortho ring cleavage detected by gas chromatograph/mass spectrometer (GC-MS). Out of the three acclimated PCP degrading bacterial strains only one strain, Acinetobacter sp. showed the presence of integron gene cassette as a marker of its stability and antibiotic resistance. The strain possessed a 4.17 kb amplicon with 22 ORF’s. The plasmid isolated from the Acinetobacter sp. was subjected to shotgun cloning through restriction digestion by BamHI, HindIII and SalI, ligated to pUC19 vector and transformed into E. coli XLBlue1 , and finally selected on MSM containing PCP as sole source of carbon and energy with ampicillin as antibiotic marker. DNA sequence analysis of recombinant clones indicated homology with integron gene cassette and multiple antibiotic resistance genes.     

Effect of sodium arsenate on microbial growth in a chemostat

Abstract

Microbial transformation of sodium arsenate, the wood preservative and insecticide, is important in assessing the environmental impact of this pesticide. Recent studies using batch culture techniques have shown that arsenate is metabolized to more toxic end products. This study investigated the effect of the chemical on the microbial cells themselves using continuous flow cultures to examine the effect of arsenate on the growth and maintenance requirements of the microbes. Cell yield was lower and maintenance requirements higher at 100 pg/ml arsenate than at 10 μg/ml indicating a greater expenditure of energy by the cells to maintain homeostasis’.