Biodegradation of tributyl phosphate using Klebsiella pneumoniae sp. S3.

Tributyl phosphate (TBP) has enormous applications in the field of extraction, fuel reprocessing, as defoamers and/or plasticizers. Excessive usage of this organophosphorus compound, poses an environmental threat. The present study deals with microbial degradation of TBP using Klebsiella pneumoniae S3 isolated from the soil. Diauxic growth curve pattern explains a preferential utilization of TBP. The strain S3 was able to biotransform TBP (1,000 mg L⁻¹) to dibutyl phosphate within 48 h and showed higher tolerance towards TBP up to 17.0 g L⁻¹. Toxicity of the parent as well as degraded product was assessed using comet assay. Generation of reactive oxygen species elaborates the oxidative stress imposed upon the bacterial strain by TBP. The antioxidant defense mechanism was studied using various biomarkers namely catalase, glutathione-S-transferase, and superoxide dismutase. The present study describes a faster and eco-friendly alternative for disposal of TBP.

Chromate reduction by Burkholderia cepacia MCMB-821, isolated from the pristine habitat of alkaline crater lake.

The Cr(VI)-reducing bacterial strain MCMB-821 was isolated from the alkaline crater lake of Lonar and was identified as Burkholderia cepacia. MCMB-821 was resistant to 1,000-ppm Cr(VI) and reduced 98% of the 75 ppm Cr(VI) within 36 h at pH 9.0 in the presence of 2% salt and lactose as the electron donor. The chromate-reducing efficiency of MCMB-821 was comparable under both aerobic as well as anaerobic conditions. Electron paramagnetic resonance spectroscopy data suggested that MCMB-821 reduced Cr(VI) to Cr(III) via the formation of transient Cr(V) intermediate. The chromate-reducing ability of MCMB-821 was suppressed in the presence of membrane inhibitors and enhanced in the presence of 2,4-dinitrophenol, suggesting the involvement of electron transport chain in the Cr(VI) bioreduction.

In vivo and in vitro effect of sulfamethazine on hepatic mixed function oxidases in rats.

Sulfamethazine (SMZ) administration (ip, 3 d) of different doses to adult male rats showed significant increases in the electron transport components and activities of aminopyrine N-demethylase and aniline hydroxylase at the the 150 mg SMZ/kg dose level. However, 300 mg SMZ/kg doses produced a significant decrease in cytochrome P-450 and the activity of aminopyrine N-demethylase. In a longer duration study, 300 mg SMZ/kg caused significant decreases in cytochrome P-450 and in the activity of aminopyrine N-demethylase. The inducer dose of 150 mg SMZ/kg and the inhibitory dose of 300 mg SMZ/kg were selected for dosing young male, old male and adult female rats. Sulfamethazine administration to young male rats resulted in a significant induction of electron transport components and drug metabolizing enzymes at both dose levels. However, SMZ treatment of old rats produced significant decreases in electron transport components and aminopryine N-demethylase activity at both dose levels. A significant induction in the levels of electron transport components was observed with 150 mg SMZ/kg in female rats. All other parameters were unchanged. Sulfamethazine resulted in a mixed type of inhibition (Ki = 3.5 mM) of aminopyrine N-demethylase in vitro. Hydroxylated metabolites destructed the spectral and catalytic activity of cytochrome P-450. Our studies suggest that SMZ is a substrate of the mixed function oxidase system and induction is dependent on dosage, age and sex of the animals.

Effect of sulfamethazine on phenobarbital and benzo[a]pyrene induced hepatic microsomal mixed function oxidase system in rats.

Administration of sulfamethazine (300 mg/kg, i.p., single dose) to phenobarbital (80 mg/kg, i.p., 3 days) pretreated rats showed significant decrease in microsomal protein, electron transport components and drug metabolizing enzyme activities, compared with phenobarbital administration alone. Induction of mixed function oxidase enzymes due to phenobarbital was not affected by the pretreatment of sulfamethazine. Sulfamethazine administration to benzo[a]pyrene (20 mg/kg, i.p., 2 days in oil) pretreated rats showed no significant change, but there was a slight decrease in cytochrome P450 and aminopyrine N-demethylase activity, compared with benzo[a]pyrene administration alone. A significant inhibition was observed in aminopyrine N-demethylase activity due to in vitro addition of sulfamethazine (3.5 mM) to microsomal incubations from untreated, sulfamethazine, phenobarbital and benzo[a]pyrene-treated rats. The results indicate that the phenobarbital induced cytochrome P450 is more susceptible to sulfamethazine than benzo[a]pyrene induced cytochrome P450.

Effect of sulfamethazine on mixed function oxidase in chickens.

Sulfamethazine (SMZ) ip administration for 3 d to chickens showed significant induction of cytochrome P-450 levels and in the activities of aminopyrine N-demethylase, aniline hydroxylase and glutathione s-transferase at the dosage of 150 mg SMZ/kg body weight. Cytochrome P-450 and the activity of aniline hydroxylase were significantly decreased at 300 mg SMZ/kg body weight when compared to 150 mg SMZ/kg body weight. Other doses produced no significant changes in the parameters studied. One hundred fifty mg SMZ/kg for 1 or 3 d caused significant induction of cytochrome b5, cytochrome P-450, the drug metabolizing enzymes and glutathione s-transferase; however, 5 d of SMZ produced no significant changes. The in vitro 10 mM SMZ inhibition of aminopyrine N-demethylase and aniline hydroxylase and the induction of enzymes at 150 mg SMZ/kg body weight indicates that SMZ is a substrate of the mixed function oxidase system and may be an inducer of specific forms of cytochrome P-450.