Non-mutagenicity of toluene,o-, m- and p-xylene,o-methylbenzylalcohol and o-methylbenzylsulfate in the Ames assay

Toluene, o-, m- and p-xylene, o-methylbenzylalcohol and o-methylbenzylsulfate were assayed for mutagenicity in the Ames assay. These compounds were unable to revert Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98 and TA100, either with or without metabolic activation by S9 mix derived from livers of rats either untreated or induced with Aroclor 1254.     

Action of Benzoic Acid and its o-, m- and p-Hydroxy-Derivatives on the Dark- and Light-Induced Leaflet Movements in Cassia fasciculata Michx.

Benzoic acid and its o-, m- and p-hydroxy derivatives appliedon excised leaves of Cassia fasciculata modified the dark-induced(scotonasty) and light-induced (photonasty) leaflet movements.Benzoic acid inhibited the scotonastic closure in a dose-dependentmanner from 10^–4M to 10^–3M and promoted the photonasticopening at optimum concentration of 5.10^–4M. These effectswere dependent upon the position of hydroxyl group on the benzoicring, the o-derivative inducing a stronger effect than the m-and p-derivatives. Experiments showed that treatment with o-hydroxybenzoicacid had not to exceed 30–60 min and that the maximumeffect was obtained at pH 5.5. (Received September 16, 1986; Accepted June 22, 1987)     

Comparative Genomic Analysis and Benzene,Toluene, Ethylbenzene,and o-, m-, and p-Xylene (BTEX) Degradation Pathways of Pseudoxanthomonas spadix BD-a59

Pseudoxanthomonas spadix BD-a59, isolated from gasoline-contaminated soil, has the ability to degrade all six BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylene) compounds. The genomic features of strain BD-a59 were analyzed bioinformatically and compared with those of another fully sequenced Pseudoxanthomonas strain, P. suwonensis 11-1, which was isolated from cotton waste compost. The genome of strain BD-a59 differed from that of strain 11-1 in many characteristics, including the number of rRNA operons, dioxygenases, monooxygenases, genomic islands (GIs), and heavy metal resistance genes. A high abundance of phage integrases and GIs and the patterns in several other genetic measures (e.g., GC content, GC skew, Karlin signature, and clustered regularly interspaced short palindromic repeat [CRISPR] gene homology) indicated that strain BD-a59''s genomic architecture may have been altered through horizontal gene transfers (HGT), phage attack, and genetic reshuffling during its evolutionary history. The genes for benzene/toluene, ethylbenzene, and xylene degradations were encoded on GI-9, -13, and -21, respectively, which suggests that they may have been acquired by HGT. We used bioinformatics to predict the biodegradation pathways of the six BTEX compounds, and these pathways were proved experimentally through the analysis of the intermediates of each BTEX compound using a gas chromatograph and mass spectrometry (GC-MS). The elevated abundances of dioxygenases, monooxygenases, and rRNA operons in strain BD-a59 (relative to strain 11-1), as well as other genomic characteristics, likely confer traits that enhance ecological fitness by enabling strain BD-a59 to degrade hydrocarbons in the soil environment.     

Simultaneous determination of 3-nitro tyrosine, o-, m-, and p-tyrosine in urine samples by liquid chromatography-ultraviolet absorbance detection with pre-column cloud point extraction

Stable 3-nitro tyrosine (3-NO(2)-Tyr), o-, m-, and p-tyrosine isomers induced by oxidation of tyrosine residues in protein were considered important biomarkers for the existence of toxic oxidizing agents peroxynitrite (ONOO(-)) and OH*, which could lead to such diseases as acute lung injury, neurodegenerative disorders, atherosclerosis, cancers and many other diseases. Therefore, development of an accurate, simple and sensitive method to simultaneously detect o-, m-, and p-tyrosine and 3-NO(2)-Tyr is necessary. Fluorescence detection is highly sensitive to o-, m-, and p-tyrosine, but it cannot be used to detect 3-NO(2)-Tyr, due to the strong fluorescence-quenching characteristic of the NO(2) group. In this study, we developed a highly sensitive reversed HPLC-UV method, combined with pre-column cloud point extraction (CPE), to simultaneously determine o-, m-, and p-tyrosine and 3-NO(2)-Tyr. The procedure included derivatization of a sample with 6-aminoquinolyl-N-hydroxy-succinimidyl carbomate (AccQ) at 0.20 mol/l borate buffer (pH 8.80) for 30 min at 70 degrees C, and pre-concentration with surfactant cloud point extraction. The surfactant-rich phase was then diluted with deionized water and injected directly into the to HPLC column for analysis. A C(18) column (3.9 mm i.d. x 300 mm) was used for gradient elution separation at 25 degrees C and the detection wavelength was at 254 nm. Nineteen general amino acids showed no interference. The detection limits of p-, o-, m-Tyr and 3-NO(2)-Tyr were between 5 and 15 nmol/l. The linear range was from 0.05 to approximately 100 micromol/l.     

硝基苯类化合物微生物降解研究进展

硝基苯类化合物是一类具有稳定化学性质、高毒性和易在生物体内积累的优先污染物.微生物降解在硝基苯类化合物废水废气治理和污染环境修复方面具有明显优势.从降解菌的驯化筛选、降解途径、降解机理、共代谢、趋化性和分子遗传学角度,阐述了硝基苯类化合物微生物降解研究的最新进展,指出应进一步加强工程菌的构建及其应用开发研究.在硝基苯类化合物污染环境的微生物修复方面,共代谢和混合菌株的协同作用具有重要的应用前景.     

Distribution and elimination of o-125I-benzoate in rats

125I-labelled o-iodobenzoate (OIB) was prepared by means of an isotopic exchange reaction; its distribution and excretion were determined and its pharmacokinetic parameters in rats were calculated. The calculated value of the half-life of OIB elimination was 38.7 +/- 0.7 min, the distribution volume was 278.2 +/- 53.5 ml . kg-1. The rate of elimination activity in urine was in agreement with the above values. On the basis of the developed technique of separation of OIB metabolites by thin-layer chromatography, their relative proportion in rat urine was determined; within 24 h 50% of the eliminated activity was in the original form (as OIB) and the metabolites of o-iodohippurate and o-iodobenzoylglucuronide formed approximately 25% of the activity eliminated in urine each.     

Degradation of nitrobenzene by a Pseudomonas pseudoalcaligenes.

A Pseudomonas pseudoalcaligenes able to use nitrobenzene as the sole source of carbon, nitrogen, and energy was isolated from soil and groundwater contaminated with nitrobenzene. The range of aromatic substrates able to support growth was limited to nitrobenzene, hydroxylaminobenzene, and 2-aminophenol. Washed suspensions of nitrobenzene-grown cells removed nitrobenzene from culture fluids with the concomitant release of ammonia. Nitrobenzene, nitrosobenzene, hydroxylaminobenzene, and 2-aminophenol stimulated oxygen uptake in resting cells and in extracts of nitrobenzene-grown cells. Under aerobic and anaerobic conditions, crude extracts converted nitrobenzene to 2-aminophenol with oxidation of 2 mol of NADPH. Ring cleavage, which required ferrous iron, produced a transient yellow product with a maximum A380. In the presence of NAD, the product disappeared and NADH was produced. In the absence of NAD, the ring fission product was spontaneously converted to picolinic acid, which was not further metabolized. These results indicate that the catabolic pathway involves the reduction of nitrobenzene to nitrosobenzene and then to hydroxylaminobenzene; each of these steps requires 1 mol of NADPH. An enzyme-mediated Bamberger-like rearrangement converts hydroxylaminobenzene to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. The mechanism for release of ammonia and subsequent metabolism are under investigation.     

Expression and bioconversion of recombinant m- and p-hydroxybenzoate hydroxylases from a novel moderate halophile, Chromohalobacter sp.

p-Hydroxybenzoate hydroxylase (pobA) and m-hydroxybenzoate hydroxylase (mobA) genes, from the moderate halophile Chromohalobacter sp. HS-2, were expressed and characterized. Solubilities of overexpressed recombinant MobA and PobA were enhanced by the induction of the heat-shock proteins DnaJ and DnaK. Each MobA and PobA maintained stable activity under high NaCl concentrations. V (max) and K (m) values for MobA with m-hydroxybenzoate were 70?μmol?min(-1)?mg(-1) protein and 81?μM, respectively. Similarly, those of PobA with p-hydroxybenzoate as substrate were 5?μmol?min(-1)?mg(-1) protein and 129?μM, respectively. The Escherichia coli expression system, including induction of heat shock proteins, was used to convert hydroxybenzoates into protocatechuate (3,4-dihydroxybenzoate) and revealed that resting cells harboring mobA converted 15?mM m-hydroxybenzoate to 15?mM protocatechuate while those harboring pobA converted 50?mM p-hydroxybenzoate to 35?mM protocatechuate at 30?°C, respectively.