Fermentation of methanethiol and dimethylsulfide by a newly isolated methanogenic bacterium

From dilution series in defined mineral medium, a marine iregular coccoid methanogenic bacterium (strain MTP4) was isolated that was able to grow on methanethiol as sole source of energy. The strain also grew on dimethylsulfide, mono-, di-, and trimethylamine, methanol and acetate. On formate the organism produced methane without significant growth. Optimal growth on MT, with doubling times of about 20 h, occurred at 30°C in marine medium. The isolate required p-aminobenzoate and a further not identified vitamin. Strain MTP4 had a high tolerance to hydrogen sulfide but was very sensitive to mechanical forces or addition of detergents such as Triton X-100 or sodium dodecylsulfate. Methanethiol was fermented by strain MTP4 according to the following equation:

Formation of dimethylsulfide and methanethiol from methoxylated aromatic compounds and inorganic sulfide by newly isolated anaerobic bacteria

Formation of gas and of methylated sulfur compounds was observed in anaerobic enrichment cultures with methoxylated aromatic compounds as substrates. Via direct dilution of mud samples in defined reduced media supplemented with trimethoxybenzoate or syringate two new strains of anaerobic homoacetogenic bacteria (strain TMBS4 and strain SA2) were obtained in pure culture. Both strains produced dimethylsulfide and methanethiol during growth on methoxylated aromatic compounds. Growth tests and determination of stoichiometries demonstrated that the volatile sulfur compounds were formed from the methyl group at the aromatic ring and the sulfide added as reducing agent to the medium (R = aromatic residue): 2 R - O - CH₃ + H₂ S 2 R - OH + (CH₃)₂SDimethylsulfide was the major organic sulfur compound formed, whereas methanethiol appeared only as intermediate in small quantities. The isolates grew also with trihydroxybenzenes such as gallate, phloroglucinol, or pyrogallol without formation of methylated sulfur compounds. The aromatic compounds were degraded to acetate. The freshwater strain TMBS4 also fermented pyruvate. Other aliphatic or aromatic compounds were not utilized. External electron acceptors (sulfate, nitrate, fumarate) were not reduced. Both strains were mesophilic and formed rod-shaped, non-motile, Gram-negative cells. Spore formation was not observed. Tentatively, both isolates can be affiliated to the genus Pelobacter.Abbreviations TMB 3,4,5-trimethoxybenzoate - MT methanethiol - DMS dimethylsulfide     

The distribution and interconversion of ammonium and nitrate in the Skallingen salt marsh (Denmark) and their exchange with the adjacent coastal water

The potential nitrogen sources for the primary production in the intertidal area are nitrogen compounds obtained from mineralization in the sediment and the water column, nitrogen fixation, outflow from rivers and groundwater seeping from the mainland. The available inorganic nitrogen in the adjacent coastal waters decreases from 50–80 μmol NO₃ ^-/l and 6–15 μmol NH₄ ⁺/l in early spring to ca one tenth during the growing season. In the sediment of the tidal flats available ammonia and nitrate vary between 50 and 100 μmol/1 pw. In the salt marsh available ammonia increases from 200–300 nmol NH₄ ⁺/g fwt to approximately double the amount, and the available nitrate varies from 100–300 nmol NO₃ ^-/g fwt (250–750 μmol NO₃ ^-/l pw) to ca one third during the growing season. The exchange of NH₄ ⁺, NO₂ ^- and NO₃ ^- across the sediment water interface has been estimated during tidal cycles under light and dark conditions on the tidal flats. The flux of nitrogen was dependent on the flora and fauna as well as the time of the year. The tidal activity, frequency and length of inundation are considered the driving force in a two-way process between salt marshes and adjacent coastal waters. The role of marsh sediment, tidal water and sediments of the tidal flats as sites of accumulation, consumption and remineralization of organic matter is emphasized. The possible exchange of ammonia and nitrate between the salt marsh and the different compartments of the tidal water is discussed.     

Genetic Linkage in the Horse. II. Distribution of Male Recombination Estimates and the Influence of Age, Breed and Sex on Recombination Frequency

In the present study an extensive amount of data, comprising more than 30,000 offspring in total, was analyzed to evaluate the influence of age and sex on the recombination frequency in the K-PGD segment of the equine linkage group (LG) I and the influence of age, breed and sex on recombination in the Al-Es segment of LG II. A highly significant sex difference is reported for both segments. Male and female recombination values in the K-PGD segment were estimated at 25.8 ± 0.8 and 33.3 ± 2.5%, respectively. Similarly, recombination was less frequent in the male (36.6 ± 0.7%) than in the female (46.6 ± 1.2%) in the Al-Es segment. Comparison of data from two Swedish horse breeds revealed no significant breed differences in either sex for recombination in the Al-Es segment. No evidence of an age effect was found in any segment or sex. The distribution of individual male recombination estimates was also investigated, and a significant heterogeneity among stallions was revealed in the K-PGD segment. The results are discussed in relation to previous studies on factors affecting recombination in mammals.     

The neural connection between the Langerhans receptor cells and the central nervous system in Oikopleura dioica (Appendicularia)

Summary Transmission electron microscopic analysis of serial sections showed that the receptor cells are innervated by only one neuron and not two as previously believed. The neuron's two dendrites constitute the afferent sensory nerves to the caudal ganglion where the neuron's cell body is located. Its neurite was traced a few micrometers, but the synaptic terminals were not identified. This sensory system in Oikopleura is compared with a similar caudal sensory system in the tadpole larva of Diplosoma macdonaldi investigated by Torrence and Cloney. Wiring diagrams are proposed for the two systems. The ganglia, which receive the afferent sensory neurons, are discussed in terms of models for further research on simple integration systems.     

Determination of platinum by neutron activation analysis in nerve tissue from rats treated with cisplatin

Biological Trace Element Research - The analytical method used for the determination of traces of platinum and gold in different tissues of Wistar rats is based on neutron activation analysis with...     

Nutrient distribution in a Swedish tree species experiment

The influence of four tree species on the distribution of nutrients between different compartments of the ecosystem was examined. In a randomized block (n=3) experiment in south-western Sweden, Ca, Mg and K were determined as exchangeable amounts in the mineral soil and as total amounts in the O+A₁ horizons (topsoil) and in the aboveground tree biomass. N contents were determined in all compartments as well as P contents of the aboveground tree biomass and the topsoil. The four tree species planted were: silver fir [Abies alba Mill.] (AA), grand fir [Abies grandis Lindl.] (AG), Norway spruce [Picea abies L. Karst.] (PA) and Japanese larch [Larix leptolepis (Sieb. och Zucc.) Endl.] (LL). At the age of 35–36 years, the total stemwood production of the most productive species, AG, was estimated at 471 m³ ha⁻¹. In relation to AG, LL had produced 80%, PA 73% and AA 37%. The system totals [aboveground tree biomass total + topsoil total + exchangeable (Ca, Mg, K) or total (N) in the mineral soil] of Ca, K and N did not differ significantly at the 5% level between the investigated species. For Mg, the system total in LL was significantly higher than for the other species. There was an indication that LL and AA contained higher amounts of Ca, Mg, K and N in the topsoil but less in the biomass than did AG and PA (partly significant). In the mineral soil, there were no significant differences in the exchangeable pools of Ca and K, nor in the total amounts of N. The biomass nutrient concentrations generally decreased in the order: AA > PA > AG > LL. At stem or whole-tree harvest, the Ca export per biomass unit would more than double in the case of PA compared to LL. LL also contained less N in the biomass than the other species. However, the N content in the biomass did not differ between the most (AG) and the least (AA) productive species, although the production of dry weight biomass (standing + harvested) of AG had been twice that of AA. It is concluded that the nutrient budget of a managed forest may vary considerably depending on the choice of tree species.     

Bacterial Disproportionation of Elemental Sulfur Coupled to Chemical Reduction of Iron or Manganese

A new chemolithotrophic bacterial metabolism was discovered in anaerobic marine enrichment cultures. Cultures in defined medium with elemental sulfur (S⁰) and amorphous ferric hydroxide (FeOOH) as sole substrates showed intense formation of sulfate. Furthermore, precipitation of ferrous sulfide and pyrite was observed. The transformations were accompanied by growth of slightly curved, rod-shaped bacteria. The quantification of the products revealed that S⁰ was microbially disproportionated to sulfate and sulfide, as follows: 4S⁰ + 4H₂O → SO₄^2- + 3H₂S + 2H⁺. Subsequent chemical reactions between the formed sulfide and the added FeOOH led to the observed precipitation of iron sulfides. Sulfate and iron sulfides were also produced when FeOOH was replaced by FeCO₃. Further enrichment with manganese oxide, MnO₂, instead of FeOOH yielded stable cultures which formed sulfate during concomitant reduction of MnO₂ to Mn²⁺. Growth of small rod-shaped bacteria was observed. When incubated without MnO₂, the culture did not grow but produced small amounts of SO₄^2- and H₂S at a ratio of 1:3, indicating again a disproportionation of S⁰. The observed microbial disproportionation of S⁰ only proceeds significantly in the presence of sulfide-scavenging agents such as iron and manganese compounds. The population density of bacteria capable of S⁰ disproportionation in the presence of FeOOH or MnO₂ was high, > 10⁴ cm^-3 in coastal sediments. The metabolism offers an explanation for recent observations of anaerobic sulfide oxidation to sulfate in anoxic sediments.     

Sequence analysis of an actin isoform in the flatworm Diphyllobothrium dendriticum (Cestoda)

We have examined actin cDNA of the flatworm Diphyllobothrium dendriticum (Cestoda). Actin is a contractile protein that has been implicated in a variety of developmental and cellular processes. It is highly conserved and present in all eukaryotic cells. It is of particular interest to analyze evolutionary preserved genes in flatworms, because ancestral flatworms are regarded to play a central role in the evolution of the metazoans (Barnes et al., 1998). Screening a cDNA library of D. dendriticum (UniZap XR, Stratagene) with a human -actin probe resulted in several positive clones. One of the cDNA inserts, Didactl, consisting of 1392 bp was completely sequenced. The established nucleotide sequence revealed a 5 untranslated region of 33 bp, the entire open reading frame of 1128 bp and a 3 untranslated region of 231 bp which ends in a stretch of 21 A residues. The potential polyadenylation signal (AATAAA) is located 14 bp upstream of the poly (A) tail. The deduced amino acid sequence of Didactl is 376 amino acids long. It is a typical invertebrate actin (Fyrberg et al., 1981) resembling more the cytoplasmic than the muscular isoforms of vertebrate actins. Didactl is for example 96% homologous to human cytoplasmic -actin but only 92.6% identical with human smooth muscle -actin. The actin proteins are generally encoded by a multigene family which differs in size from species to species. Most organisms have four to eight genes coding for actin in their genome, but the number of actin genes can also be over 20 (Hamelin et al., 1988). Sequence comparisons of Didactl and the partly sequenced cDNA clones indicate that D. dendriticum has at least four different genes coding for actin in its genome.