Volatile compounds associated with microbial growth on normal and high pH beef stored at chill temperatures

Volatile compounds produced by Pseudomonas fragi and mixed, natural floras on beef of normal pH (5.5-5.8; glucose greater than 1500 micrograms/g) and high pH (6.3-6.8; glucose less than 10 micrograms/g) included a range of alkyl esters and a number of sulphur-containing compounds including dimethylsulphide but not hydrogen sulphide. Production of the last was a property common to the other Gram-negative organisms tested viz. Hafnia alvei, Enterobacter agglomerans, Serratia liquefaciens, Alteromonas putrefaciens and Aeromonas hydrophila, all of which produced similar off-odours and, with the exception of E. agglomerans, 'greening' on high pH meat. Serratia liquefaciens also produced greening of normal pH meat. Acetoin and diacetyl were major end products of Brochothrix thermosphacta but the related 2,3-butanediol was formed only on normal pH meat. The Enterobacteriaceae produced the same compounds but only on normal pH meat and together with Br. thermosphacta were probable sources of these compounds and of the free and esterified branched-chain alcohols detected in the naturally contaminated samples.     

Volatile compounds associated with microbial growth on normal and high pH beef stored at chill temperatures

Volatile compounds produced by Pseudomonas fragi and mixed, natural floras on beef of normal pH (5–5–5–8; glucose < 1500 μg/g) and high pH (6–3–6–8; glucose < 10 μg/g) included a range of alkyl esters and a number of sulphur-containing compounds including dimethylsulphide but not hydrogen sulphide. Production of the last was a property common to the other Gram-negative organisms tested viz. Hafnia alvei, Enterobacter agglomerans, Serratia liquefaciens, Alteromonas putrefaciens and Aeromonas hydrophila , all of which produced similar off-odours and, with the exception of E. agglomerans , 'greening'on high pH meat. Serratia liquefaciens also produced greening of normal pH meat. Acetoin and diacetyl were major end products of Brochothrix thermosphacta but the related 2,3-butanediol was formed only on normal pH meat. The Enterobacteriaceae produced the same compounds but only on normal pH meat and together with Br. thermosphacta were probable sources of these compounds and of the free and esterified branched-chain alcohols detected in the naturally contaminated samples.     

Reduction of nitroaromatic compounds by different Pseudomonas species under aerobic conditions

Summary Pseudomonas sp. CBS3 converted various nitro-aromatic compounds under aerobic resting-cell conditions to the corresponding amino compounds. Mononitro-compounds were reduced to anilines. 1-Chloro-2,4-dinitrobenzene was reduced via the two possible chloronitroanilines to 4-chloro-1,3-diaminobenzene. In the case of 2,4,6-trinitrotoluene, two monoaminodinitrotoluenes and one diaminomononitrotoluene were obtained. In addition to the reduction, in most cases the amines were partially acetylated. In experiments under an argon atmosphere conversion of the nitro-compounds was as fast as under aerobic conditions. Cells of Pseudomonas sp. CBS3 cultivated on complex medium showed higher nitro-reducing activity than those cultivated on mineral salts medium with 4-chlorobenzoate as substrate, which is normally used as medium for this strain. Several other Pseudomonas species (ATCC 4359, ATCC 23937, ATCC 15005, ATCC 17933) also showed nitro-reducing activities. In crude cell-free extracts of Pseudomonas sp. CBS3 an enzyme catalysing the reduction of nitro-aromatics was detected. The enzyme was inactivated by dialysis and was reactivated by the addition of NADH or NADPH. NADPH was the more efficient co-substrate.Offprint requests to: R. Müller     

Volatile components of some Rutaceae species

The volatile components of the aerial parts of Ruta graveolens and Haplophyllum suaveolens, as well as of leaves of Zanthoxylum limoncello, Z. panamense and Z. setulosum have been studied by GC/MS analysis.     

Ornithine-containing lipids of some Pseudomonas species

Ornithine-containing lipids purified by thin-layer chromatography were found to represent 2-15% of the total extractable cellular lipids in two or three strains each of four Pseudomonas species: P. aeruginosa, P. fluorescens, P. stutzeri and P. cepacia. The structures of the ornithine-containing lipids were elucidated by chemical analysis, thin-layer chromatography, gas-liquid chromatography, gas-liquid chromatography/mass spectrometry (electron impact or secondary ion) and infrared absorption spectroscopy. At least six molecular species of ornithine-containing lipids were present in common in all of the preparations of the four Pseudomonas species. The structure which was the most abundantly in P. fluorescens (about 60% of the total amount of the ornithine-containing lipid) was 3-hydroxyhexadecanoic acid amide-linked to ornithine and esterified to hexadecanoic acid. In addition to this structure, 3-hydroxyoctadecenoic acid amide-linked to ornithine and esterified to hexadecanoic acid was a dominant structure in the ornithine-containing lipids of P. aeruginosa, P. stutzeri or P. cepacia. In P. cepacia, another ornithine-containing lipids with a terminal polar fatty acid, 3-hydroxyhexadecanoic acid amide-linked to ornithine and esterified to 2-hydroxynonadecacyclopropanoic acid or 2-hydroxyoctadecenoic acid, was found; its content, which represented 8-11% of the total extractable cellular lipids, was higher than that of the ornithine-containing lipids with a terminal nonpolar fatty acid. These ornithine-containing lipids exhibited hemagglutinating activity. Additionally, it was very interesting that hydroxy fatty acids included in the ornithine-containing lipids were not found in the phospholipids which represented more than 80% of the total extractable cellular lipids.     

Volatile compounds produced by meat pseudomonads and related reference strains during growth on beef stored in air at chill temperatures

Volatile compounds produced by 31 strains of pseudomonads and by reference strains of Pseudomonas fragi and Ps. fluorescens biotype 1 during growth on beef stored at 6°C in air were analysed by gas chromatography-mass spectrometry of headspace gases. Compounds of major sensory significance were ethyl and methyl esters of C₂–C₈ fatty acids and sulphur-containing compounds which included methane- and isopropanethiols and their related sulphides and thioesters but not hydrogen sulphide. Ester production was mainly associated with growth of some, but not all, Ps. fragi and related meat strains but sulphur-containing compounds were produced by all but a single meat strain. A minority of other meat strains produced greater amounts of methyl ketones, secondary alcohols and unsaturated hydrocarbons believed to be of lipid origin.     

Volatile compounds produced by meat pseudomonads and relate reference strains during growth on beef stored in air at chill temperatures

Volatile compounds produced by 31 strains of pseudomonads and by reference strains of Pseudomonas fragi and Ps. fluorescens biotype 1 during growth on beef stored at 6 degrees C in air were analysed by gas chromatography-mass spectrometry of headspace gases. Compounds of major sensory significance were ethyl and methyl esters of C2-C8 fatty acids and sulphur-containing compounds which included methane- and isopropanethiols and their related sulphides and thioesters but not hydrogen sulphide. Ester production was mainly associated with growth of some, but not all, Ps. fragi and related meat strains but sulphur-containing compounds were produced by all but a single meat strain. A minority of other meat strains produced greater amounts of methyl ketones, secondary alcohols and unsaturated hydrocarbons believed to be of lipid origin.     

Methylovorus mays--novel species of aerobic, obligatory methylotrophic bacteria associated with plants

A bacterial strain utilizing methanol as the sole source of carbon and energy was isolated from the maize phyllosphere. Cells are nonpigmented gram-negative motile rods that do not form spores or prosthecae and reproduce by binary fission. The strain does not require vitamins or supplementary growth factors. It is obligately aerobic and urease-, oxidase-, and catalase-positive. The optimum growth temperature is 35-40 degrees C; the optimum pH is 7.0-7.5. The doubling time is 2 h. The bacterium implements the ribulose monophosphate pathway and possesses NAD(+)-dependent 6-phosphogluconate dehydrogenase and enzymes of the glutamate cycle. alpha-Ketoglutarate dehydrogenase and enzymes of the glyoxylate cycle (isocitrate lyase and malate synthase) are absent. Fatty acids are dominated by palmitic (C16:0) and palmitoleic (C16:1) acids. The major phospholipids are phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylcholine. Cardiolipin is present in minor amounts. The dominant ubiquinone is Q8. The bacterial genome contains genes controlling the synthesis and secretion of cytokinins. The G + C content of DNA is 57.2 mol %, as determined from the DNA thermal denaturation temperature (Tm). The bacterium shows low DNA homology (< 10%) with restricted facultative methylotrophic bacteria of the genus Methylophilus (M. methylotrophus NCIMB 10515T and M. leisingerii VKM B-2013T) and with the obligate methylotrophic bacterium (Methylobacillus glycogenes ATCC 29475T). DNA homology with the type representative of the genus Methylovorus, M. glucosetrophus VKM B-1745T, is high (58%). The new isolate was classified as a new species, Methylovorus mays sp. now.     

Volatile organic compounds of some Trichoderma spp. increase growth and induce salt tolerance in Arabidopsis thaliana

Many beneficial effects of Trichoderma spp. on plant growth and/or resistance to biotic/abiotic stresses can result from the production of bioactive compounds including volatile organic compounds (VOCs). We evaluated the effects of the volatile mixtures from 13 strains of different Trichoderma species on induction of tolerance to salt stress (100 mM NaCl) as well as growth promotion of Arabidopsis thaliana. Plants responded differently due to the presence of VOCs from various Trichoderma species ranging from both growth promotion and induction of salt tolerance to no significant changes under any of the conditions tested. In plants exposed for 2 weeks to VOCs of the selected strain, i.e. Trichoderma koningii, there was less H₂O₂ accumulation under salt stress compared to that in control plants. This result may reflect the possible role of VOCs of this strain in plant protection against oxidative damage under salt stress. Together, induction of salt tolerance using VOCs should be added to the known mechanisms of plant vigor enhancement by Trichoderma spp.     

Volatile compounds from Pinus silvestris stimulating the growth of wood-rotting fungi

Summary Certain volatile organic acids stimulated the growth of Stereum sanguinolentum when added through the gas phase or to the liquid nutrient medium. Some of the acids were identified in extract of heat-treated wood of pine (Pinus silvestris), which had been shown (Suolahti, 1951) to have a growth-promoting effect on Stereum sanguinolentum and other wood-rotting fungi.The effect of volatile materials from a heat-treated piece of pine-wood and of caproic acid was tested on 13 other wood-rotting fungi. The growth of 11 of them was stimulated by volatiles from pine-wood, only 2 by caproic acid.The morphology of Coniophora cerebella was altered when volatiles from a neutral fraction of pine-wood extract was added through the gas phase.     

The direct role of aerobic heterotrophic bacteria associated with cyanobacteria in the degradation of oil compounds

This study aimed at evaluating the role of cyanobacteria and their associated aerobic heterotrophic bacteria in biodegradation of petroleum compounds. We investigated the potential of ten non-axenic typical mat-forming cyanobacterial strains to degrade phenanthrene, pristane, n-octadecane, and dibenzothiophene. Five strains (Aphanothece halophyletica, Dactyolococcopsis salina, Halothece strain EPUS, Oscillatoria strain OSC, and Synechocystis strain UNIGA) were able to degrade n-alkanes. In case of the other five strains (Microcoleus chthonoplastes, Oscillatoria sp. MPI 95 OS 01, Halothece strain EPUG, Halomicronema exentricum, and Phormidium strain UNITF) alkanes were not significantly affected. Moderate changes in the concentration of the aromatic compounds were observed for three isolates only. In follow-up experiments with Oscillatoria strain OSC, we demonstrated that the cyanobacteria-associated aerobic heterotrophic bacteria were responsible for the observed biodegradation. The cyanobacteria themselves apparently do not degrade petroleum compounds, but more likely play a significant, indirect role in biodegradation by supporting the growth and activity of the actual degraders.     

Retinoid compounds associated with water blooms dominated by Microcystis species

Retinoic acids play a critical role in vital physiological processes and vertebrate development, and their derivatives can be produced by some cyanobacterial species into surface waters. This study presents important environmentally-relevant information on total retinoid-like activity of field cyanobacterial biomasses and their surrounding waters. Intracellular and extracellular levels of total retinoid-like activity and retinoic acids have been investigated at a set of independent sites with the occurrence of water bloom dominated by widespread species Microcystis aeruginosa. Twelve samples of biomass and surrounding water from seven localities affected by blooms were studied in comparison with samples from M. aeruginosa laboratory cultures. The method for biomass extraction was optimized and final extracts and samples of surrounding water concentrated by solid phase extraction were assessed using in vitro reporter gene bioassay and chemical analyses for all-trans-retinoic acid (ATRA), 9-cis retinoic acid (9-cis RA) and microcystins RR, LR and YR. Methanol was the most efficient solvent for the extraction of compounds with retinoid-like activity. An in vitro bioassay with the P19/A15 transgenic cell line revealed retinoid-like activity in all cyanobacterial biomasses in the range of 356–2838 ng of retinoid acid equivalents (REQ)/g dry mass (dm), while only three of surrounding water samples exhibited detectable retinoid-like activity, in the range of 12.8–28.7 ng REQ/L. Microcystins were detected in all samples, but they elicited no detectable retinoid-like activity up to 10 mg/L. Chemical analyses detected concentrations up to 340 ng/g dm of all-trans-retinoic acid (ATRA) and 84 ng/g dm 9-cis retinoic acid (9-cis RA) in bloom extracts, and up to 19 ng/L ATRA and 2.2 ng/L 9-cis RA in surrounding water. In most samples, ATRA and 9-cis RA contributed relatively little to the total REQs, which indicates the presence of significant amounts of other compounds with retinoic acid receptor-mediated modes of action. The impact of retinoid-like cyanobacterial metabolites could be of importance namely in smaller water bodies with dense water blooms and low dilution.     

Volatile compounds from some wild growing aromatic herbs of the Lamiaceae from southern France

Abstract

The composition of the volatile fraction in selected aromatic plants of the Lamiaceae from garrigue sites in southern France is described. Calamintha nepeta appeared heterogeneous. The oil was dominated by piperitone oxide, and piperitenone oxide or by pulegone and menthone. In Nepeta nepetella, nepetalactone, almost exclusively the (4a-α, 7α, 7a-β)-isomer, made up more than 85% of the essential oil. Dichloromethane extracts from Teucrium polium contained germacrene D or sabinene as main components, α-pinene, β-pinene and β-caryophyllene in varying proportions as further important constituents, and various minor components depending on the origin.