Bacterial reduction of fensulfothion and its hydrolysis product 4-methylsulfinyl phenol

Oxygen-limited cultures of Klebsiella pneumoniae reduced 4-methylsulfinyl phenol to 4-methylthiophenol. A study of the effect of 4-methylthiophenol on the growth of K. pneumoniae revealed that the specific growth rate was retarded by 40% in the presence of 200 micrograms of the phenol per ml. A soil bacterium, Hafnia sp., was isolated that could reduce the organophosphorus insecticide fensulfothion to fensulfothion sulfide.     

Reduction of fensulfothion to fensulfothion sulfide by Klebsiella pneumoniae.

A cell suspension of Klebsiella pneumoniae converted the organophosphorus pesticide fensulfothion to a product that was shown by chemical oxidation, gas-liquid chromatography, infrared spectrophotometry, and mass spectrometry to be fensulfothion sulfide. Further alteration of this metabolite was not noted.     

Reduction of fensulfothion to fensulfothion sulfide by Klebsiella pneumoniae.

A cell suspension of Klebsiella pneumoniae converted the organophosphorus pesticide fensulfothion to a product that was shown by chemical oxidation, gas-liquid chromatography, infrared spectrophotometry, and mass spectrometry to be fensulfothion sulfide. Further alteration of this metabolite was not noted.     

Effects of AQ4N and its reduction product on radiation-mediated DNA strand breakage

Supercoiled plasmid pBR322 DNA was irradiated in phosphate buffer by 60Co gamma-rays at a dose rate 19.26 Gy/min and total dose of 10 Gy in the presence of a bioreductive antitumour prodrug namely 1,4-bis [?2-(dimethylamino-N-oxide)ethyl? amino] 5, 8-dihydroxyanthracene-9,10-dione (AQ4N) and its DNA affinic reduction product 1,4-bis[?2(dimethylamino)ethyl? amino] 5,8-dihydroxyanthracene-9,10-dione (AQ4) under air and nitrogen. AQ4N and AQ4 were found to protect against radiation-induced plasmid single and double strand breakage as assessed by agarose gel electrophoresis. The differences between the two agents, and between atmospheres of air or nitrogen were negligible. It was also found that the protection efficiencies of the compounds were pH dependent and showed maximum protection at pH 6. These results indicate that protection of DNA by AQ4 and AQ4N against radiation damage is an indirect effect since both agents are equally effective despite major differences in their DNA affinity. It is likely that radiation-induced phosphate buffer radicals are intercepted by AQ4 and AQ4N in a pH-dependent process.     

Mineralization of phenol and its derivatives by Pseudomonas sp. strain CP4

A Pseudomonas sp. strain, CP4, was isolated that used phenol up to 1.5 g/l as sole source of carbon and energy. Optimal growth on 1.5 g phenol/l was at pH 6.5 to 7.0 and 30°C. Unadapted cells needed 72 h to decrease the chemical oxygen demand (COD) of about 2000 mg/l (from 1 g phenol/l) to about 200 mg/l. Adapted cells, pregrown on phenol, required only 65 h to decrease the COD level to below 100 mg/l. Adaptation of cells to phenol also improved the degradation of cresols. Cell-free extracts of strain CP4 grown on phenol or o-, m- or p-cresol had sp. act. of 0.82, 0.35, 0.54 and 0.32 units of catechol 2,3-dioxygenase and 0.06, 0.05, 0.05 and 0.03 units of catechol 1,2-dioxygenase, respectively. Cells grown on glucose or succinate had neither activity. Benzoate and all isomers of cresol, creosote, hydroxybenzoates, catechol and methyl catechol were utilized by strain CP4. No chloroaromatic was degraded, either as sole substrate or as co-substrate.The authors are with the Department of Microbiology and Bioengineering, Central Food Technological Research Institute, Mysore-570 013, India     

稀土元素对土壤中尿素水解及其水解产物行为的影响

以潮土为供试土壤进行土培试验,研究了农用稀土对同时施加的尿素在土壤中形态转化过程影响,当稀土施用量增至10mg/kg^-1烘干土以上时,土壤中尿素水解后所形成的铵态氮含量显著增加,在不同培养时间内,土壤中源自尿素的硝态氮和亚硝态氮含量随稀土施用量增加呈降低趋势;当施用量增至50mg/kg^-1烘干土时,与对照相比的降低程度达显著水平,施加稀土元素后,土壤有效氮含量明显增加,主要由于土壤铵态氮增加所致,结合土壤pH变化,表明稀土施用量高于10mg.kg^-1烘干土时,可明显延缓尿素在潮土中水解进程并抑制水解产物铵态氮的氧化,利于土训对尿素氮固持。     

The oxidation of phenol and its reaction product by horseradish peroxidase and hydrogen peroxide

Phenol and its oxidized products are shown to be substrates in the HRP, H₂O₂ enzyme system. The homogeneous nature of the product of phenol oxidation suggests that the radical generated remains enzyme-bound until coupling occurs. Kinetics of the reaction was investigated and was suggestive of a three substrate ping-pong mechanism.     

A biologically active acid hydrolysis product of saxitoxin.

The preparation, purification, and biological and chemical properties of a decarbamylated product of saxitoxin are described.     

Bacterial degradation of airborne phenol in the phyllosphere

Despite the vast surface area of terrestrial plant leaves and the large microbial communities they support, little is known of the ability of leaf-associated microorganisms to access and degrade airborne pollutants. Here, we examined bacterial acquisition and degradation of phenol on leaves by an introduced phenol degrader and by natural phyllosphere communities. Whole-cell gfp-based Pseudomonas fluorescens bioreporter cells detected phenol on leaves that had previously been transiently exposed to gaseous phenol, indicating that leaves accumulated phenol; moreover, they accumulated it in sites that were accessible to epiphytic bacteria and to concentrations that were at least 10-fold higher than those in the air. After inoculated leaves were exposed to gaseous 14C-phenol, leaves harbouring the phenol-degrading Pseudomonas sp. strain CF600 released eight times more 14CO2 than did leaves harbouring a non-degrading mutant, demonstrating that CF600 actively mineralized phenol on leaves. We evaluated phenol degradation by natural microbial communities on green ash leaves that were collected from a field site rich in airborne organic pollutants. We found that significantly more phenol was mineralized by these leaves when the communities were present than by these leaves following surface sterilization. Thus, phenol-degrading organisms were present in these natural communities and were metabolically capable of phenol degradation. Collectively, these results provide the first direct evidence that bacteria on leaves can degrade an organic pollutant from the air, and indicate that bacteria on leaves could potentially contribute to the natural attenuation of organic air pollutants.     

Starch hydrolysis and its effect on product yield and microbial contamination in yeast ethanol fermentation

The influence of temperature and incubation time on starch gelatinization in wheat, rye and corn grain were studied. Rye starch was the most susceptlble to enzyme hydrolysls. Heat treatment of ground grain during starch gelatinlzation significantly reduced microblal contamination. In the batch fermentation of wheat, a high sugar utillization ranged from 92 to 94%. The highest alcohol yield was 65% from rye starch. The results obtained show that the high pressure cooking used for mash preparation can be replaced successfully by low temperature treatment.The authors are with the Institute of Food Technology of Plant Origin, The University of Agriculture, 60-624 Poznan, ul. Wojska Polskiego 31, Poland.     

Bacterial reduction of hexavalent chromium

Summary Cr(VI)-reducing bacteria are widespread and Cr(VI) reduction occurs under both aerobic and anaerobic conditions. Under aerobic conditions, both NADH and endogenous cell reserves may serve as the electron donor for Cr(VI) reduction. Under anaerobic conditions, electron transport systems containing cytochromes appear to be involved in Cr(VI) reduction. High cell densities are necessary to obtain a significant rate of Cr(VI) reduction. Cr(VI) reduction by bacteria may be inhibited by Cr(VI), oxygen, heavy metals, and phenolic compounds. The optimum pH and temperature observed for Cr(VI) reduction generally coincide with the optimal growth conditions of cells. The optimum redox potential for Cr(VI) reduction has not yet been established.     

Chitosanase-catalyzed hydrolysis of 4-methylumbelliferyl beta-chitotrioside.

4-Methylumbelliferyl beta-chitotrioside [(GlcN)(3)-UMB] was prepared from 4-methylumbelliferyl tri-N-acetyl-beta-chitotrioside [(GlcNAc)(3)-UMB] using chitin deacetylase from Colletotrichum lindemuthianum, and hydrolyzed by chitosanase from Streptomyces sp. N174. The enzymatic deacetylation of (GlcNAc)(3)-UMB was confirmed by (1)H-NMR spectroscopy and mass spectrometry. When the (GlcN)(3)-UMB obtained was incubated with chitosanase, the fluorescence intensity at 450 nm obtained by excitation at 360 nm was found to increase with proportion to the reaction time. The rate of increase in the fluorescence intensity was proportional to the enzyme concentration. This indicates that chitosanase hydrolyzes the glycosidic linkage between a GlcN residue and UMB moiety releasing the fluorescent UMB molecule. Since (GlcN)(3) itself cannot be hydrolyzed by the chitosanase, (GlcN)(3)-UMB is considered to be a useful low molecular weight substrate for the assay of chitosanase. The k(cat) and K(m) values obtained for the substrate (GlcN)(3)-UMB were determined to be 8.1 x 10(-5) s(-1) and 201 microM, respectively. From TLC analysis of the reaction products, the chitosanase was found to hydrolyze not only the linkages between a GlcN residue and UMB moiety, but also the linkages between GlcN residues. Nevertheless, the high sensitivity of the fluorescence detection of the UMB molecule would enable a more accurate determination of kinetic constants for chitosanases.     

Bacterial bioluminescence-identification of fatty acid as product, its quantum yield and a suggested mechanism

By using radioactive decanal the direct transformation of this aldehyde to decanoic acid, with a quantum yield of 0.13, has been demonstrated. A mechanism analogous to that of other better understood bioluminescent reactions is proposed, leading to a product, as yet unisolated from the enzymic reaction, whose fluorescence spectrum is an excellent match for that of the $\text{in vivo}$ luminescence.The extensive examination^1,2,3 of the isolated bacterial luminescence system has resulted in the accepted outline shown. We wish to modify it, in accordance with the previous evidence, by suggesting that ’intermediates I and II‘ in Hastings' terminology² are the same enzyme bound FMNH₂ moiety.

$\text{FMN}{}_2\text{enzyme}\text{?}\text{enzyme FMNH}{}_2$

$\text{enzyme FMNH}{}_2\text{RCHO}\text{?}\text{covalent complex}$

$\text{covalent complex O}{}_2\text{→}\text{P}{}^1\text{RCO}{}_2\text{H}$

A lively controversy has surrounded the attempts to determine whether aldehyde exerts a purely catalytic role² or is transformed in the reaction.⁴ If the aldehyde reacts, then the simplest product is the corresponding carboxylic acid, perhaps formed via the peracid. The most likely alternative reaction would involve enolistation and oxidation at the α-methylene group. We examined the second alternative fairly carefully, and found no evidence for it. We do not wish to report these results in detail at present, since we have now established that the acid corresponding to that formed in a normal autoxidation of the aldehyde is the product. Some indication of the nature of the products of the reaction is available.⁵Since the amount of product in the reaction is restricted to a very low level by the concentrations required, we labelled decanal with tritium at C-2 and thus were able to record the yield with some precision. Although recent work⁶ strongly implies that acid is formed stoichiometrically, the direct measurement of the quantum yield with respect to acid formation is necessary before a mechanism can be written. We have suggested a mechanism compatible with observations in this system, analogous to all cases of bioluminescence for which a mechanism is reasonably well established. This mechanism also leads to a product excited state with excellent agreement around pH7 in fluorescence wavelength to that of the $\text{in vivo}$ luminescence.     

Bacterial 4-alpha-helical bundle cytochromes.

The biological functions of cytochrome c' and bacterioferritin, both haemoproteins with a common 4-alpha-helical bundle structure, are discussed and an example given of one of Kamen's laws, namely: comparative studies of prokaryotic cytochromes and their eukaryotic counterparts are useful. In the present case, the comparison is between bacterioferritin and its animal counterpart, haemoferritin.