Degradation of hydroxyhydroquinone by the strictly anaerobic fermenting bacterium Pelobacter massiliensis sp. nov.

A new rod-shaped, gram-negative, non-sporeforming, strictly anaerobic bacterium (strain HHQ7) was enriched and isolated from marine mud samples with hydroxyhydroquinone (1,2,4-trihydroxybenzene) as sole substrate. Strain HHQ7 fermented hydroxyhydroquinone, pyrogallol (1,2,3-trihydroxybenzene), phloroglucinol (1,3,5-trihydroxybenzene) and gallic acid (3,4,5-trihydroxybenzoate) to 3 mol acetate (plus 1 mol CO₂ in the case of gallic acid) per mol of substrate. Resorcinol accumulated intermediately during growth on hydroxy-hydroquinone. No other aliphatic or aromatic substrates were utilized. Sulfate, sulfite, sulfur, nitrate, and fumarate were not reduced with hydroxyhydroquinone as electron donor. The strain grew in sulfide-reduced mineral medium supplemented with 7 vitamins. The DNA base ratio was 59% G+C. Strain HHQ7 is classified as a new species of the genus Pelobacter, P. massiliensis. Experiments with dense cell suspensions of hydroxyhydroquinone-and pyrogallol-grown cells showed different kinetics of hydroxyhydroquinone and pyrogallol degradation, as well as different patterns of resorcinol accumulation, indicating that these substrates are metabolized by different transhydroxylation reactions.     

A single amino acid substitution changes the substrate specificity of quinoprotein glucose dehydrogenase in Gluconobacter oxydans.

Summary Gluconobacter oxydans contains pyrroloquinoline quinone-dependent glucose dehydrogenase (GDH). Two isogenic G. oxydans strains, P1 and P2, which differ in their substrate specificity with respect to oxidation of sugars have been analysed. P1 can oxidize only d-glucose, whereas P2 is also capable of the oxidation of the disaccharide maltose. To investigate the nature of this maltose-oxidizing property we cloned the gene encoding GDH from P2. Expression of P2 gdh in P1 enables the latter strain to oxidize maltose, indicating that a mutation in the P2 gdh gene is responsible for the change in substrate specificity. This mutation could be ascribed to a 1 by substitution resulting in the replacement of His 787 by Asn.     

Trans-regulatory genes affect Slpa and Slpo expression and act in a tissue-specific manner

The plasma protein C4 and its androgen-dependent homologue Slp are encoded by genes located in the mouse major histocompatibility complex, H-2. The C4 and Slp protein levels and liver mRNA levels are influenced by non-H-2-linked regulatory genes. The allele-specific regulation of C4 expression and the androgen regulation of Slp expression are manifest only in some of the tissues where these genes are expressed. Therefore, we studied tissues in which the effects of the non-H-2 regulatory genes are apparent. We show that these genes only affect the Slp expression in tissues where it is androgen-dependent. This indicates that the non-H-2 regulatory genes most likely act through interaction with the androgen regulation of Slp expression. We also show that liver cells of mice with the Slp ^o allele, which do not produce Slp protein, do express Slp mRNA; this expression is also androgen-induced and regulated by non-H-2 genes. Thus, both the Slp ^a and Slp ^o alleles appear to be regulated in the same way.     

FINE STRUCTURE OF MISTLETOE POLLEN. V. MADAGASCAN AND CONTINENTAL AFRICAN VISCUM L. (VISCACEAE)

Pollen characters of Madagascan and continental African Viscum are described and compared to those in Asia and Australia. The subprolate, tricolporate, nonuniformly sculptured pollen of Madagascan taxa is most similar to that of Asian species. Ultrastructurally, however, the completely granular equatorial ektexine of Madagascan Viscum is most similar to that of continental African taxa. Continental African Viscum, in contrast to Madagascan and Asian species, display a wide variation in pollen shape and apertures. Pollen shape ranges from subprolate to oblate, the latter unique to Africa. The most striking feature of continental Viscum is their variability in aperture number and aperture type. Aperture number varies at both the intra- and interpopulational levels with such variation resolvable to the individual flower—a condition unique to the continent. The only simple (colpate) aperture type in the genus is restricted to Africa. The continental species can be divided into two species groups based on pollen characters: Group I (4 spp.) characterized by strictly tricolporate rounded convex pollen with a rodlet/granular equatorial ektexine structure and Group II (most continental species) possessing multiapertures, concave lobate shape, uniform sculpturing and granular equatorial ektexine. The African V. menyharthii, V. fischeri, V. rotundifolium and V. minimum exhibit no clear Group I or II affinities. An analysis of overall pollen characters in Viscum indicates a trend towards spheroidal shape, multiapertures and uniform sculpturing and ektexine organization. Though pollen characters suggest ties between Australia, Asia and Madagascar, they indicate an even stronger relationship between Madagascar and continental Africa, particularly eastern Africa. The relationship of the majority of African Viscum, excluding those with obvious Madagascan affinities, remains obscure. The unique palynological features of Group II species coupled with their inflorescence structure suggest an independently evolving group.     

Sucrose and ouabain effects on the kinetic properties of a membrane-bound (Na++ K++ Mg2+) ATPase in sugar beet roots

Kinetic studies of a microsomal (Na⁺+ K⁺+ Mg²⁺)ATPase from sugar beet roots ( Beta vulgaris L. cv. Monohill) show that sucrose influences the MgATPase in different ways depending on the presence of K⁺ and/or Na⁺ 1) In the presence of the substrate MgATP and Na⁺ the effect of sucrose follows simple Michaelis-Menten kinetics. 2) In the presence of substrate together with K⁺ or (K⁺+ Na⁺), sucrose has little effect on the ATPase activity. 3) In the presence of Na⁺, onabain acts as an uncompetitive inhibitor with respect to MgATP. 4) In the presence of K⁺ or (K⁺+ Na⁺), the inhibition by ouabain is somewhat depressed and shows non-linearity when 1/v is plotted versus 1/MgATP. 5) Sucrose and Na⁺ activate in a competitive way, so that a successive increase of the Na⁺ level decreases the activation by sucrose. Both K_m and V-values are thereby changed. 6) The sucrose activation in the presence of Na⁺ is also influenced by ouabain. It is, therefore, suggested that Na⁺ may regulate the interference between the Na⁺/K⁺ pump and a sucrose sensitive system.     

Pollen morphology and relationships of the Misodendraceae (Santalales)

The stem–parasitic family Misodendraceae is composed of a single genus, Misoden–drum , of 12 species endemic to the subantarctic Nothofagus forests of Chile and Argentina. Pollen of nine species was examined in the light microscope and scanning and transmission electron microscopes. Pollen is spheroidal (P/E 1 :1), sparsely echi–nate and polyporate. Aperture number is variable within and among species ranging from (3–)4–19 pores scattered randomly over the surface. Ultrastructurally, the pollen wall is composed primarily of endexine with the ektexine represented only by spines and an occasional thin granular layer between these elements. Pollen data indicate ties with the recently resurrected santalalean family Eremolepidaceae including Lepidoceras.     

Development and evaluation of a rapid, simple, sensitive, monoclonal antibody-based co-agglutination test for direct detection of Vibrio cholerae 01

Cholera epidemics caused by Vibrio cholerae 01 continue to represent a major public health concern in many developing countries. A rapid and simple test kit for the detection of V. cholerae 01 has been developed. The kit, CholeraScreen is a monoclonal antibody-based, co-agglutination test and is used directly with stool specimens. It does not include culturing the specimen and is performed without the need for sophisticated laboratory equipment. Specificity of the test was demonstrated, using 118 reference cultures, to which cross-reactions were not observed. Preliminary results of field trials carried out in Guatemala and Bangladesh demonstrated that the test is equally sensitive as conventional culture methods in detecting V. cholerae and, in many cases, more sensitive. The CholeraScreen test is simple, specific, and does not require culturing procedures, making it suitable for direct detection of cells of V. cholerae in clinical specimens, even in the field. Also, the test requires less than five minutes to complete.     

Sequential Transhydroxylations Converting Hydroxyhydroquinone to Phloroglucinol in the Strictly Anaerobic, Fermentative Bacterium Pelobacter massiliensis

The recently isolated fermenting bacterium Pelobacter massiliensis is the only strict anaerobe known to grow on hydroxyhydroquinone (1,2,4-trihydroxybenzene) as the sole source of carbon and energy, converting it to stoichiometric amounts of acetate. In this paper, we report on the enzymatic reactions involved in the conversion of hydroxyhydroquinone and pyrogallol (1,2,3-trihydroxybenzene) to phloroglucinol (1,3,5-trihydroxybenzene). Cell extracts of P. massiliensis transhydroxylate pyrogallol to phloroglucinol after addition of 1,2,3,5-tetrahydroxybenzene (1,2,3,5-TTHB) as cosubstrate in a reaction identical to that found earlier with Pelobacter acidigallici (A. Brune and B. Schink, J. Bacteriol. 172:1070-1076, 1990). Hydroxyhydroquinone conversion to phloroglucinol is initiated in cell extracts without an external addition of cosubstrates. It involves a minimum of three consecutive transhydroxylation reactions characterized by the transient accumulation of two different TTHB isomers. Chemical synthesis of the TTHB intermediates allowed the resolution of the distinct transhydroxylation steps in this sequence. In an initial transhydroxylation, the hydroxyl group in the 1-position of a molecule of hydroxyhydroquinone is transferred to the 5-position of another molecule of hydroxyhydroquinone to give 1,2,4,5-TTHB and resorcinol (1,3-dihydroxybenzene) as products. Following this disproportionation of hydroxyhydroquinone, the 1,2,4,5-isomer is converted to 1,2,3,5-TTHB, an enzymatic activity present only in hydroxyhydroquinone-grown cells. Finally, phloroglucinol is formed from 1,2,3,5-TTHB by transfer of the 2-hydroxyl group to either hydroxyhydroquinone or resorcinol. The resulting coproducts are again cosubstrates in earlier reactions of this sequence. From the spectrum of hydroxybenzenes transhydroxylated by the cell extracts, the minimum structural prerequisites that render a hydroxybenzene a hydroxyl donor or acceptor are deduced.     

Influence of method of application of paclobutrazol on soil residues and growth retardation in a ‘Starkrimson-Delicious’ apple orchard

A 3-year field study was conducted to determine the influence of mode of application of the gibberellin-inhibitor paclobutrazol (PP333), [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl)pentan-3-ol], on PP333 soil residue levels and vegetative growth retardation of 10-year-old Starkrimson Delicious (Malus Domestica Borkh.) spur-type apple trees. Treatments were applied in March, 1986 and consisted of foliar or soil sprays (200 ppm, 7 × applications at petal fall (+) 2, 4, 6, 8, 10 and 12 weeks) or a single soil drench (8.2 g A.I./tree) applied to the collar at petal fall. Foliar sprays were applied with and without a plastic ground cover to evaluate the influence of foliar runoff on the degree of soil absorption and its subsequent effect on vegetative growth. PP333 was extracted over a 3 year period (1986–88) from 400 cm² soil patches located at the drip line of each tree, with the exception of soil drenches which were sampled near the collar. PP333 soil extracts were purified and quantitatively analyzed by HPLC. PP333 soil residue levels following foliar sprays were comparable to the soil spray treatment for each year and decreased at a rate of 50% per year from 1986–1988. Foliar sprays retarded terminal growth in the year of application, whereas the soil spray did not inhibit growth until the following year. PP333 residue levels were highest in the soil drench where growth retardation was evident in 1987 and 1988. The greatest carry-over effect occurred in the soil treatments, especially the soil drench application which resulted in the highest soil residue rates throughout the 3 year period.     

Histopathology of Apple Proliferation in Malus Taxa and Hybrids of Different Susceptibility

Malus taxa and hybrids (“taxa”) grafted with M. pumila cv.‘Golden Delicious’differ significantly in their susceptibility to apple proliferation which is caused by a mycoplasma-like organism (MLO). These differences are correlated with the severity of anatomical aberrations and the numbers of MLOs in the phloem. The roots of declining trees of highly susceptible taxa with a mortality of more than 50 % are characterized by extensive phloem necrosis and the depletion of starch. MLOs are either not detectable or are present in low numbers, or the population appears degenerate when viewed by fluorescence microscopy. In comparable trees of a hybrid of M. sieboldii×M. pumila which shows a high recovery rate, both phloem necrosis and starch depletion are less pronounced, and the MLO numbers are low or the organisms are not detectable. Decline-tolerant taxa such as M. silvestris or M. pumila×M. baccata are little affected. Their phloem conditions and starch content do not differ significantly from that of healthy trees. However, the MLO titer is high. The histopathology of the scion cultivar of all groups examined is rather similar to that of the roots of the decline-tolerant taxa. Only in a late stage of decline, phloem necrosis increases while starch content and MLO numbers decrease in the scions grafted onto highly susceptible stockls.