Initial reactions in the mineralization of 2-sulfobenzoate by Pseudomonas sp. RW611

Abstract Pseudomonas sp. strain RW611 utilized the ammonium salt of 2-sulfobenzoate as sole source of carbon, sulfur, nitrogen, and energy. The xenobiotic sulfo substituent was dioxygenolytically eliminated as sulfite, which was then slowly oxidized to sulfate. 2,3-Dihydroxybenzoate, which resulted from desulfonation underwent meta -cleavage, mediated by 2,3-dihydroxybenzoate 3,4-dioxygenase activity. This enzyme was inhibited by 3-chlorocatechol and 2,3,4-trihydroxybenzoate.     

Ascaris suum and Onchocerca volvulus: S-adenosylmethionine decarboxylase

Putrescine-dependent S-adenosylmethionine decarboxylase (EC 4.1.1.50) was demonstrated in Ascaris suum and Onchocerca volvulus; activation was found to be about fourfold by putrescine. Mg2+ did not affect the enzyme activity. A. suum was taken as a model nematode and its S-adenosylmethionine decarboxylase was partially purified and characterized. The molecular weight was estimated to be 220,000. The apparent Km-value for adenosylmethionine was determined to be 17 microM. Methylglyoxal bis(guanylhydrazone) and berenil competitively inhibited the enzyme activity; the apparent Ki-values were found to be 0.24 microM and 0.11 microM, respectively. The dependence of filarial worms on uptake and interconversion of putrescine and polyamines as well as properties of the S-adenosylmethionine decarboxylase, different from the host enzyme, points to the polyamine metabolisms as a useful target for chemotherapy.     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Degradation of 1,2,3,4-Tetrachlorobenzene by Pseudomonas chlororaphis RW71

Pseudomonas chlororaphis RW71 mineralized 1,2,3,4-tetrachlorobenzene, a highly recalcitrant pollutant hitherto not known to be degraded by pure cultures, as a sole source of carbon and energy, thereby releasing stoichiometric amounts of chloride. The transient excretion of tetrachlorocatechol in the early growth phase suggests an initial attack by a dioxygenase to form the corresponding dihydrodiol which rearomatizes to the catechol. The activity of chlorocatechol 1,2-dioxygenase in crude cell extracts was found to be extraordinarily high towards 3-chlorocatechol (ratio of 2.6 compared to catechol) and other chlorocatechols, including tetrachlorocatechol, which was transformed at a low but significant rate. Further identification of tetrachloromuconic acid, 2,3,5-trichlorodienelactone, 2,3,5-trichloromaleyl acetic acid, and 2,4-dichloro-3-oxoadipic acid as their methyl esters, together with high specific enzyme activities for chlorinated substrates, implicated a functioning chlorocatechol pathway to be induced during growth.     

Degradation of dioxin-like compounds by microorganisms

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF; PCDD/F, dioxins) have not been commercially produced in bulk amounts, as were polychlorinated biphenyls and other haloaromatic organics. Within the past two decades a lot␣of information has accumulated on the biodegradation of PCDD/F and other dioxin-like compounds because of their toxicity and because of significant environmental concern about many congeners of this class of chemicals. PCDD/F are subjected to reductive dehalogenations leading to less halogenated congeners, which can be attacked efficiently by fungal and bacterial oxidases and dioxygenases. In several cases these compounds can be utilized as carbon and energy sources. Pathways for their enzymatic degradation and the organisation of the corresponding degradative genes have been elucidated. Consequently, biotechnological applications will exploit the degradative potential of such microorganisms for bioremediation of contaminated sites. Received: 29 August 1997 / Received revision: 6 January 1998 / Accepted: 8 January 1998     

Altitudinal Change in the Photosynthetic Capacity of Tropical Trees: A Case Study from Ecuador and a Pantropical Literature Analysis

In tropical mountains, trees are the dominant life form from sea level to above 4,000-m altitude under highly variable thermal conditions (range of mean annual temperatures: <8 to >28°C). How light-saturated net photosynthesis of tropical trees adapts to variation in temperature, atmospheric CO₂ concentration, and further environmental factors, that change along elevation gradients, is not precisely known. With gas exchange measurements in mature trees, we determined light-saturated net photosynthesis at ambient temperature (T) and [CO₂] (A _sat) of 40 tree species from 21 families in tropical mountain forests at 1000-, 2000-, and 3000-m elevation in southern Ecuador. We tested the hypothesis that stand-level averages of A _sat and leaf dark respiration (R _D) per leaf area remain constant with elevation. Stand-level means of A _sat were 8.8, 11.3, and 7.2?μmol?CO₂?m^?2?s^?1; those of R _D 0.8, 0.6, and 0.7?μmol?CO₂?m^?2?s^?1 at 1000-, 2000-, and 3000-m elevation, respectively, with no significant altitudinal trend. We obtained coefficients of among-species variation in A _sat and R _D of 20–53% (n?=?10–16 tree species per stand). Examining our data in the context of a pan-tropical A _sat data base for mature tropical trees (c. 170 species from 18 sites at variable elevation) revealed that area-based A _sat decreases in tropical mountains by, on average, 1.3?μmol?CO₂?m^?2?s^?1?per?km altitude increase (or by 0.2?μmol?CO₂?m^?2?s^?1 per K temperature decrease). The A _sat decrease occurred despite an increase in leaf mass per area with altitude. Local geological and soil fertility conditions and related foliar N and P concentrations considerably influenced the altitudinal A _sat patterns. We conclude that elevation is an important influencing factor of the photosynthetic activity of tropical trees. Lowered A _sat together with a reduced stand leaf area decrease canopy C gain with elevation in tropical mountains.     

Sucrose utilization during ovule and seed development ofGasteria verrucosa (Mill.) H. Duval as monitored by sucrose synthase and invertase localization

Summary The development ofGasteria verrucosa ovules and seeds seems to follow a pattern of growth in which the majority of carbohydrates is first used in the sporophytic tissue (nucellus, integuments, and arillus) around the gametophyte-derived cells. After fertilization the carbohydrates are used for further development of the arillus and seed coat. During the next stage carbohydrates are directed to develop the endosperm, followed by carbohydrate investment in the developing embryo and in storage products. This utilization pattern is deducted from a localization study on sucrose synthase and invertase. These two enzymes break down imported sucrose and are in that perspective used as markers for carbohydrate transport since diffusion is expected to be induced towards cells and tissues with high sucrose-hydrolyzing activities.     

Superior survival and degradation of dibenzo-p-dioxin and dibenzofuran in soil by soil-adapted Sphingomonas sp. strain RW1

The dibenzo-p-dioxin(DD)- and dibenzofuran(DF)-degrading bacterium, Sphingomonas sp. strain RW1, was tagged by insertion of a mini-Tn5 lacZ transposon in order to follow its fate in complex laboratory soil systems. The tagged strain was tested for its ability to survive in soil and degrade DF and DD applied at a concentration of 1 mg/g. Bacteria pre-adapted to soil conditions were found to survive better in DF- and DD-amended soil and degrade the substrate more efficiently than bacteria that had not been subjected to pre-adaptation. The concentration of soil-applied DF and DD, individually and in combination, decreased to less than 2% of the original concentrations within 3 weeks of addition of the RW1 derivative, accompanied by a short, but significant exponential increase in RW1 viable cells. During the same period the native bacterial population in soil was stable while viable fungi declined. Received: 12 November 1996 / Received revision: 21 February 1997 / Accepted: 22 February 1997