Chromatographic separation of methionine,methionine sulphoxide,methionine sulphone,and their products of oral microbial metabolism

The metabolic pathways of methionine sulphoxide and methionine sulphone were investigated employing a combination of gas chromatography, thin-layer chromatography, paper chromatography, and radioactive methods of analyses. Gas chromatographic analysis demonstrated that methionine, methionine sulphoxide, and methionine sulphone all yielded qualitatively similar volatile sulphur compounds, namely, methyl mercaptan, dimethyl disulphide, and small amounts of dimethyl sulphide. The study indicated that the principal pathway of methionine sulphoxide and methionine sulphone metabolism is mediated via methionine which gives rise to methyl mercaptan, part of which is oxidized to dimethyl disulphide. Whereas methionine sulphoxide was readily reduced to methionine, the reduction of methionine sulphone proceeded at a considerably slower rate.     

The organosulphur cycle: aerobic and anaerobic processes leading to turnover of C1-sulphur compounds

Abstract The processes generating and transforming those C₁-organosulphur compounds which are major intermediates in the biogeochemical cycling of sulphur are summarised. The biological and chemical interconversions of the methylated sulphides, methane sulphonate, carbon disulphide and carbonyl sulphide are significantly influenced by diverse microorganisms, including autotrophic thiobacilli, methylotrophs, methanogens and sulphate-reducing bacteria. The major biogenic sulphur gas is dimethyl sulphide. A major atmospheric photochemical oxidation product from this is methane sulphonate, which can contribute to the acidity of rain. New data and ideas on the microbiological fate of methane sulphonate and of natural and anthropogenic carbon disulphide are presented.     

Onion aphid (Neotoxoptera formosana) attractants, in the headspace of Allium fistulosum and A. tuberosum leaves

Abstract:  Attractancy of Allium fistulosum L. and Allium tuberosum Rottl. to adult apterae of the onion aphid, Neotoxoptera formosana (Takahashi), an oligophagous aphid pest of Allium crops, was investigated with a Y-tube olfactometer. The aphids were significantly attracted to both A. fistulosum and A. tuberosum . The headspace components of both plants were extracted with solid-phase microextraction (SPME) and analysed by gas chromatography-mass spectrometry (GC-MS). The main volatile components of A. fistulosum were dipropyl disulphide (relative contents: 67%), 1-propenyl propyl disulphide (23%) and dipropyl trisulphide (6%). In the headspace of A. tuberosum , diallyl disulphide was detected as the main component (58%). Attractancy of dipropyl disulphide, dipropyl trisulphide and diallyl disulphide to the aphids was examined with the Y-tube olfactometer. The aphids were significantly attracted to dipropyl trisulphide and diallyl disulphide at a concentration of 0.01%. Dipropyl disulphide did not significantly attract the aphids at any concentrations tested. It was revealed that attractancy of A. fistulosum and A. tuberosum was caused by dipropyl trisulphide and diallyl disulphide, respectively. The findings suggest that N. formosana uses these sulphur compounds, characteristic components of Allium plants, as olfactory cues to find the host plants.     

Use of the Analysis of the Volatile Faecal Metabolome in Screening for Colorectal Cancer

Diagnosis of colorectal cancer is an invasive and expensive colonoscopy, which is usually carried out after a positive screening test. Unfortunately, existing screening tests lack specificity and sensitivity, hence many unnecessary colonoscopies are performed. Here we report on a potential new screening test for colorectal cancer based on the analysis of volatile organic compounds (VOCs) in the headspace of faecal samples. Faecal samples were obtained from subjects who had a positive faecal occult blood sample (FOBT). Subjects subsequently had colonoscopies performed to classify them into low risk (non-cancer) and high risk (colorectal cancer) groups. Volatile organic compounds were analysed by selected ion flow tube mass spectrometry (SIFT-MS) and then data were analysed using both univariate and multivariate statistical methods. Ions most likely from hydrogen sulphide, dimethyl sulphide and dimethyl disulphide are statistically significantly higher in samples from high risk rather than low risk subjects. Results using multivariate methods show that the test gives a correct classification of 75% with 78% specificity and 72% sensitivity on FOBT positive samples, offering a potentially effective alternative to FOBT.     

Sulphur-containing “perfumes” attract flower-visiting bats

 We tested the attractiveness of individual scent compounds of bat-pollinated flowers to their pollinators, small flower-visiting bats of the genus Glossophaga (Phyllostomidae). Twenty compounds belonging to four different chemical substance classes were tested, both in the laboratory and in the field. In the laboratory, the bats (Glossophaga soricina) approached odour sources spontaneously and without preceding experience. Without ever receiving any reward they preferred the scent of a sulphur-containing compound, dimethyl disulphide, to several other odour components emitted by bat-pollinated flowers, and to scentless controls. In the field, at La Selva station in the tropical lowland rain forest of Costa Rica, G. commissarisi were attracted by two sulphur-containing compounds, dimethyl disulphide and 2,4-dithiapentane, to visit artificial flowers filled with sugar water. Thus, in nectarivorous bats the sense of smell obviously plays an important role in searching for and localising food sources, and even single components of the scent bouquets of bat-pollinated flowers are attractive. The preference for sulphur-containing odours seems to be innate. Accepted: 9 November 1999     

Biofiltration of reduced sulphur compounds and community analysis of sulphur-oxidizing bacteria

The present work aims to use a two-stage biotrickling filters for simultaneous treatment of hydrogen sulphide (H₂S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). The first biofilter was inoculated with Acidithiobacillus thiooxidans (BAT) and the second one with Thiobacillus thioparus (BTT). For separate feeds of reduced sulphur compounds (RSC), the elimination capacity (EC) order was DMDS > DMS > MM. The EC values were 9.8 g_MM-S/m³/h (BTT; 78% removal efficiency (RE); empty bed residence time (EBRT) 58 s), 36 g_DMDS-S/m³/h (BTT; 94.4% RE; EBRT 76 s) and 57.5 g_H2S-S/m³/h (BAT; 92% RE; EBRT 59 s). For the simultaneous removal of RSC in BTT, an increase in the H₂S concentration from 23 to 293 ppmv (EBRT of 59 s) inhibited the RE of DMS (97-84% RE), DMDS (86-76% RE) and MM (83-67% RE). In the two-stage biofiltration, the RE did not decrease on increasing the H₂S concentration from 75 to 432 ppmv.     

Oviposition response of the mosquito,Culex quinquefasciatus to the secondary metabolite(s) of the fungus,Trichoderma viride

Secondary metabolites produced by Trichoderma viride, a deuteromycetes fungus, under submerged culture condition were formulated and evaluated for oviposition attractancy against gravid females of Culex quinquefasciatus mosquito. At a concentration of 10 g ml-1 the formulation showed remarkable attractancy with an oviposition active index (OAI) of +0.52. When the oviposition attractancy of the formulation was compared with a known oviposition attractant, p-cresol, both at 10 g ml-1, the former was found to be more attractive to result in 70% egg laying than the later with 30% egg laying. Thin layer chromatography fractions of the secondary metabolites showed that a fraction with Rf value of 0.88 was highly active as oviposition attractant with an OAI of +0.65. Further work on identification of the active principle(s) of the microbial formulation might lead to an oviposition attractant useful in mosquito vector management.     

Antifungal polysulphides from Petiveria alliacea L

Bioactivity-directed fractionation of the CH(2)Cl(2)/MeOH (2:1, v/v) extract of the roots of Petiveria alliacea, using mutant yeast strains of Saccharomyces cerevisiae and fungi Cladosporium cladosporioides and C. sphaerospermum led to the isolation of dipropyl disulphide (1), dibenzyl sulphide (2), dibenzyl disulphide (3), dibenzyl trisulphide (4), dibenzyl tetrasulphide (5), benzylhydroxymethyl sulphide (6) and di(benzyltrithio) methane (7). Of these, 5-7 are new compounds and this is the first report of the natural occurrence of 2 and 3.     

Molecular analysis of dimethyl sulphide dehydrogenase from Rhodovulum sulfidophilum: its place in the dimethyl sulphoxide reductase family of microbial molybdopterin-containing enzymes

Dimethyl sulphide dehydrogenase catalyses the oxidation of dimethyl sulphide to dimethyl sulphoxide (DMSO) during photoautotrophic growth of Rhodovulum sulfidophilum. Dimethyl sulphide dehydrogenase was shown to contain bis(molybdopterin guanine dinucleotide)Mo, the form of the pterin molybdenum cofactor unique to enzymes of the DMSO reductase family. Sequence analysis of the ddh gene cluster showed that the ddhA gene encodes a polypeptide with highest sequence similarity to the molybdopterin-containing subunits of selenate reductase, ethylbenzene dehydrogenase. These polypeptides form a distinct clade within the DMSO reductase family. Further sequence analysis of the ddh gene cluster identified three genes, ddhB, ddhD and ddhC. DdhB showed sequence homology to NarH, suggesting that it contains multiple iron-sulphur clusters. Analysis of the N-terminal signal sequence of DdhA suggests that it is secreted via the Tat secretory system in complex with DdhB, whereas DdhC is probably secreted via a Sec-dependent mechanism. Analysis of a ddhA mutant showed that dimethyl sulphide dehydrogenase was essential for photolithotrophic growth of Rv. sulfidophilum on dimethyl sulphide but not for chemo-trophic growth on the same substrate. Mutational analysis showed that cytochrome c2 mediated photosynthetic electron transfer from dimethyl sulphide dehydrogenase to the photochemical reaction centre, although this cytochrome was not essential for photoheterotrophic growth of the bacterium.     

Some evidence of the nature of the Golgi-Cox deposit and its biochemical origin

Summary Evidence obtained from simple chemical tests suggests that the black deposit in Golgi-Cox impregnated nerve cells which have been submitted to alkalinisation is black mercuric sulphide. Some sulphydryl and disulphide containing compounds may prove to be useful chemical models for studying the mechanism of this histological method.     

The response of German cockroaches to toxic baits:strain differences and the effects of selection pressure

Strain differences in the response of German cockroaches to toxic baits and their potential to evolve resistance to them was evaluated in choice tests. Percentage bait consumption (amount of bait consumed divided by total food consumed) was used to estimate relative attractancy/repellency of the baits. One strain apparently had low level resistance to abamectin, but no evidence of resistance was found in other strains tested with either Roach Ender or a gel bait (abamectin-based baits). Incipient behavioral resistance occurred in two strains selected for three generations with Roach Ender; a stronger response in a strain selected with the gel bait is attributed to the development of behavioral resistance. Baygon bait was highly repellent. Low level resistance to propoxur caused a large decrease in mortality compared with susceptible strains. Strong behavioral resistance developed in strains selected with Stapleton's Magnetic Roach Food.     

1,4-benzoquinone attracts males of Rhizotrogus vernus Germ

Two candidate attractants, phenol and 1,4-benzoquinone, a synthetic mixture of typical compounds from green-leaf odours [(Z)-3-hexenyl acetate: (Z)-3-hexen-1-ol: benzaldehyde: (E)-2-hexen-1-ol: 1-hexanol; 100:20:10:1:1] and freshly damaged oak leaves were screened for field attractancy in funnel traps in Hungary. Males of two Rhizotrogus spp. (Coleoptera, Scarabaeidae, Melolonthinae), R. aestivus 01. and R. vernus Germ. were caught in larger numbers. While R. aestivus catches were probably chance captures, male R. vernus was significantly attracted to the baits containing 1,4-benzoquinone. This compound represents a promising basis for the development of a monitoring trap for R. vernus.     

Chemolithoutotrophic growth of Thiothrix ramosa

Thiothrix has been shown for the first time to be able to grow chemolithoautotrophically with thiosulphate or carbon disulphide as sole energy substrate. Thiosulphate served as the growth-limiting substrate for Thiothrix ramosa in chemostat culture. Maximum growth yield (Y_max) from yields at growth rates between 0.029–0.075 h^-1 was 4.0 g protein/mol thiosulphate oxidized. The key enzyme of the Calvin cycle, ribulose 1,5-bisphosphate carboxylase, was present in these cells, as were rhodanese, adenylyl sulphate (APS) reductase and sulphur-oxidizing enzyme. Thiosulphate-grown cells oxidized thiosulphate, sulphide, tetrathionate and carbon disulphide. Oxidation kinetics for sulphide, thiosulphate and tetrathionate were biphasic: oxygen consumption during the fast first phase of oxidation indicated oxidation of sulphide, and the sulphane moieties of thiosulphate and tetrathionate, to elemental sulphur, before further oxidation to sulphate. Kinetic constants for these four substrates were determined. T. ramosa also grew mixotrophically in batch culture on lactate with a number of organic sulphur compounds: carbon disulphide, methanethiol and diethyl sulphide. Substituted thiophenes were also used as sole substrates. The metabolic versatility of T. ramosa is thus much greater than previously realised.     

Comparative effect of three rodenticides warfarin,bromadiolone and brodifacoum on the Indian field mouse,Mus booduga gray

Three anticoagulant rodenticides, warfarin, bromadiolone and brodifacoum, were evaluated in the laboratory for their activity against the Indian field mouse, Mus booduga. In oral intubation studies M. booduga was found to be more susceptible to bromadiolone and brodifacoum than warfarin. Feeding studies with 0.005% bromadiolone and brodifacoum baits produced 83% mortality after a single day's feeding while a similar mortality was achieved with 0.025% warfarin only after 6 days of consecutive feeding. The anticoagulant baits were less palatable than the plain (unpoisoned) bait. Laboratory feeding tests confirmed that 0.005% of the active ingredient would be an effective bait concentration for field use of both bromadiolone and brodifacoum. The single-feed potency of bromadiolone and brodifacoum indicate that these rodenticides may be more effective and economical than warfarin in the field.     

Release of volatiles during the flowering period of Hydrosme rivieri (Araceae)

The release of volatile compounds from a flower of Hydrosme rivieri was recorded during the whole flowering period (7 days). The quantities of six odour components (dimethyl disulphide, dimethyl trisulphide, n-alkanes C₁₀, C₁₁, C₁₂ and C₁₃) forming the main part of emanating volatiles were plotted versus time. n-Alkanes started to emanate 3 days before the release of dimethyl disulphide and dimethyl trisulphide (the components with a rotting meat odour).     

Chemolithotrophic potential of a Hyphomicrobium species,capable of growth on methylated sulphur compounds

The yield of Hyphomicrobium EG on dimethyl sulphoxide, dimethyl sulphide and methylamine, considering the metabolic pathways of these compounds, suggested that the organism gained energy from the oxidation of the sulphur moiety of the former compounds. Indeed, a comparison of chemostat cultures of Hyphomicrobium EG grown on methylamine in the presence and absence of sulphide or thiosulphate proved this obligate methylotroph to be a chemolithoheterotroph. The apparent Y_sulphide and Y_thiosulphate were comparable, being 8–10 g dry weight/mol. In batch cultures thiosulphate concentrations up to 10 mM had a stimulatory effect on the growth rate of Hyphomicrobium EG, whereas higher concentrations increased the organisms doubling time.Enzyme- and respiration data showed that the organism had constitutive enzymes for the breakdown of dimethyl sulphoxide although they were clearly regulated to need. Addition of sulphide or thiosulphate to methylamine-limited chemostat cultures of Hyphomicrobium EG not only resulted in the induction of enzymes necessary for their breakdown, but also caused the enzymes for dimethyl sulphoxide metabolism, especially methyl mercaptan oxidase, to be induced. The formation of H₂O₂, a product of the latter enzyme, was reflected in the relatively high catalase activities during growth on dimethyl sulphoxide and in the organisms inability to grow on this compound in the presence of a catalase inhibitor.Abbreviations DMSO dimethyl sulphoxide - DMS dimethyl sulphide - MM methyl mercaptan - TMAO trimethylamine N-oxide - D dilution rate - GSH redticed glutathione - DCPIP 2,6-dichlorophenolindophenol - PMS phenazine methosulphate - PES phenazine ethosulphate - RubPCase ribulose 1,5-bisphosphate carboxylase - PEPCase phosphoenol pyruvate carboxylase - Wurster's blue (TMPD) N,N,N,N-tetramethyl-p-phenylenediamine     

Control of the Indian mole rat with alpha-chlorohydrin: laboratory studies on bait acceptance and antifertility effects

Toxic and antifertility effects of feeding poison baits of a toxicant-sterilant, alpha-chlorohydrin, were studied against the Indian mole rat Bandicota bengalensis . It was found that 0.5% alpha-chlorohydrin bait was the most palatable formulation which delivered the amount of active ingredient equal to or more than MLD (82 mg/kg) to B. bengalensis in a single day's feeding. The rats suffered maximum mortality with this bait concentration both in no-choice and bi-choice feeding trials. Male survivors of 0.5% and 1.0% alpha-chlorohydrin baits showed functional abnormalities of their testes as revealed by loss in testicular weight, decrease in the diameter of seminiferous tubules and thickness of seminiferous epithelium and abnormally low levels of spermatogenic cells. Effect of the poison on epididymis became apparent by the presence of epididymal lesions in caput epididymides and low levels of sperm concentration, live sperms and sperm motility in the cauda epididymal fluid. Our findings on the acceptance and toxiccum-antifertility effects of feeding alpha-chlorohydrin baits suggest field evaluation of this poison for the management of B. bengalensis would be appropriate.     

Qualitative and quantitative responses of Diabroticina (Coleoptera: Chrysomelidae) to cucurbit extracts linked to species, sex, weather and deployment method

Toxic baits and traps for Diabroticina, based on bitter cucurbit extracts, have been utilized for a number of years with inconsistent results. Four species of bitter Cucurbitaceae were compared in the field for their attractancy to species of Diabroticina in Argentina and the United States. The comparisons were made with polyester fabrics treated with known volumes of different cucurbit extracts, against a standard cucurbit extract of bitter Hawkesbury watermelon (Citrullus lanatus (Thunberg) Matsumura and Nakai). The factors evaluated were: the attractancy of the different extracts in terms of beetle numbers, species and sex of the Diabroticina caught; influence of different fabrics on such attraction; and influence of several weather variables on the catches. The most attractive species was Cayaponia bonariensis (Miller) Martinez Crovetto, however, practical considerations indicated that Cucumis myriocarpus Naudin and Hawkesbury watermelon may be better choices from the commercial perspective. No single weather factor could explain the catches throughout the sample range, but different temperature and barometric pressure ranges provided some predictive value. Although the susceptibility to weather conditions and a strong male dominance in the catches raise the question of the usefulness of cucurbitacins as the main component in toxic baits or traps, these drawbacks may prove to be less important in widespread bait applications and Diabroticina management in vegetable crops.     

An in vitro evaluation of the effects of a Yucca schidigera extract and chestnut tannins on composition and metabolic profiles of canine and feline faecal microbiota

The in vitro effect of a Yucca schidigera extract (YSE) and tannins from chestnut wood on composition and metabolic activity of canine and feline faecal microbiota was evaluated. Four treatments were carried out: control diet, chestnut tannins (CT), YSE and CT + YSE. The YSE was added to canine and feline faecal cultures at 0.1 g/l, while CT were added at 0.3 g/l for a 24-h incubation. A total of 130 volatile compounds were detected by means of headspace-solid phase microextraction gas-chromatography/mass spectrometry analyses. Several changes in the metabolite profiles of fermentation fluids were found, including a decrease of alcohols (?19%) and esters (?42%) in feline and canine inoculum, respectively, which was due to the antibacterial properties of tannins. In canine inoculum, after 6 h, YSE + CT caused lower cadaverine concentrations (?37%), while ammonia (?4%) and quinolone (?27%) were reduced by addition of CT. After 24 h, the presence of CT resulted in a decrease of sulphur compounds, such as dimethyl sulphide (?69%) and dimethyl disulphide (?20%). In feline faecal cultures, after 6 h, CT lowered the amount of indole (?48%), whereas YSE tended to decrease trimethylamine levels (?16%). Both in canine and feline inoculum, addition of CT and, to a minor extent, YSE affected volatile fatty acids patterns. In canine faecal cultures, CT exerted a marginal inhibitory effect on Escherichia coli population (?0.45 log 10 numbers of DNA copies/ml), while enterococci were increased (+2.06 log 10 numbers of DNA copies/ml) by YSE. The results from the present study show that YSE and tannins from chestnut wood exert different effects on the composition and metabolism of canine and feline faecal microbiota. In particular, the supplementation of YSE and tannins to diets for dogs and cats may be beneficial due to the reduction of the presence of some potentially toxic volatile metabolites in the animals’ intestine.     

Toxicity of fipronil to German and American cockroaches

Topical and oral toxicity of fipronil, compared to chlorpyrifos, was determined for the German cockroach, Blattella germanica (L.), and American cockroach, Periplaneta americana (L.). Fipronil and Combat bait matrices were evaluated for their attractancies to both species. In the topical toxicity tests, LD50's of fipronil, at 72 h after topical application, were 0.03 and 0.02 µg/g for adult B. germanica and P. americana, respectively. Fipronil was significantly more toxic than topically applied chlorpyrifos (LD50's were 0.06 and 0.16 µg/g for B. germanica and P. americana, respectively). The oral toxicity of fipronil and chlorpyrifos in Petri dish experiments, against both species, was affected by stage (for B. germanica), diet concentration, and feeding assay. Fipronil caused higher mortality of B. germanica than chlorpyrifos in two feeding assays (continuous and abbreviated). Both compounds were equally toxic to adult males of P. americana at all rates. Fipronil caused higher nymphal mortality than chlorpyrifos 48–72 h after exposure in both feeding assays. In large population chamber tests, fipronil bait was more effective and faster in killing P. americana than Raid and Combat. LT50's were 0.8, 2.4, and 7.6 d for fipronil, Raid (a.i. = chlorpyrifos), and Combat (a.i. = hydramethylnon) baits, respectively. Mortality reached 96.5, 93.4, and 84.6%, respectively, at the end of the 14 d test. In the bait attractancy tests, both strains of B. germanica were attracted similarly to fipronil and Combat bait matrices. P. americana were attracted more to fipronil than to Combat bait matrix or to other alternative foods.