ABSTRACT
The strain JPL-2, capable of degrading fenoxaprop-P-ethyl (FE), was isolated from the soil of a wheat field and identified as Rhodococcus ruber. This strain could utilize FE as its sole carbon source and degrade 94.6% of 100 mg L−1 FE in 54 h. Strain JPL-2 could also degrade other aryloxyphenoxy propanoate (AOPP) herbicides. The initial step of the degradation pathway is to hydrolyze the carboxylic acid ester bond. A novel esterase gene feh, encoding the FE-hydrolyzing carboxylesterase (FeH) responsible for this initial step, was cloned from strain JPL-2. Its molecular mass was approximately 39 kDa, and the catalytic efficiency of FeH followed the order of FE > quizalofop-P-ethyl > clodinafop-propargyl > cyhalofop-butyl > fluazifop-P-butyl > haloxyfop-P-methyl > diclofop-methy, which indicated that the chain length of the alcohol moiety strongly affected the hydrolysis activity of the FeH toward AOPP herbicides.
Subject(s)
Carboxylesterase/genetics , Carboxylesterase/metabolism , Herbicides/metabolism , Oxazoles/metabolism , Propionates/metabolism , Rhodococcus/isolation & purification , Rhodococcus/metabolism , Biotransformation , Cloning, Molecular , Cluster Analysis , Carboxylesterase/chemistry , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , Molecular Sequence Data , Molecular Weight , Phylogeny , /genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Rhodococcus/enzymology , Rhodococcus/genetics , Sequence Analysis, DNA , Soil Microbiology , Substrate Specificity , Triticum/growth & developmentABSTRACT
The effect of sub-lethal concentrations of isoniazid, ethambutol, rifampicin and pyrazinamide on the growth in vitro and the production of both exochelins and mycobactins by the high virulent and the South Indian low virulent strains of M. tuberculosis was examined under iron-deficient and iron-rich conditions. There was a marked decrease in the growth of both strains in the presence of increasing concentrations of all four drugs, the inhibition being total in the presence of minimal inhibitory concentrations of the drugs. It was also observed that the growth-inhibitory effect of all four drugs was slightly reversed in the presence of high concentration of iron in the medium. A significant increase was observed in the concentrations of both siderophores in the presence of all four drugs, under both iron-deficient (or) iron-rich conditions.
Subject(s)
Antitubercular Agents/pharmacology , Iron/metabolism , Iron Chelating Agents/metabolism , Mycobacterium tuberculosis/drug effects , Oxazoles/metabolism , Peptides, Cyclic/biosynthesisABSTRACT
Hemoglobin is known to support the growth of several bacterial species. The growth and the production of siderophores by 4 strains of mycobacteria in the presence of hemoglobin was studied in vitro. The findings were compared with those obtained in the presence of equivalent concentrations of iron in the medium. Increase in the concentrations of hemoglobin caused an appreciable increase in the growth of all 4 strains. This was however, accompanied by a significant decrease in the production of both exochelins and mycobactins. It was also observed that hemoglobin supported the growth of all strains as well as that with free iron and the concentrations of both siderophores was significantly higher in the presence of hemoglobin than in that of free iron.