Bacterial reduction of hexavalent molybdenum to molybdenum blue

A bacterium that was able to tolerate and reduce as high as 50 mM of sodium molybdate to molybdenum blue has been isolated from a metal recycling ground. The isolate was tentatively identified as Serratia sp. strain Dr.Y8 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. ANOVA analysis showed that isolate Dr.Y8 produced significantly higher (P < 0.05) amount of Mo-blue with 3, 5.1 and 11.3 times more molybdenum blue than previously isolated molybdenum reducers such as Serratia marcescens strain Dr.Y6, E. coli K12 and E. cloacae strain 48, respectively. Its molybdate reduction characteristics were studied in this work. Electron donor sources such as sucrose, mannitol, fructose, glucose and starch supported molybdate reduction. The optimum phosphate, pH and temperature that supported molybdate reduction were 5 mM, pH 6.0 and 37°C, respectively. The molybdenum blue produced from cellular reduction exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium, silver, copper and mercury resulted in approximately 61, 57, 80, and 69% inhibition of the molybdenum-reducing activity at 1 mM, respectively. The reduction characteristics of strain Dr.Y8 suggest that it would be useful in future molybdenum bioremediation.     

The influence of starter cultures on the formation of volatile compounds in dry smoked sausages

The differences between the composition of volatile substances in two specimens of dry smoked sausages produced using a standard and experimental (a mixture of propionic acid bacteria and bifidobacteria) cultures were studied by capillary gas chromatography. It was found that the experimental starter culture intensified the flavor-formation processes as compared with the standard culture. The experimental specimen had richer qualitative and quantitative compositions and displayed more intensive aroma and flavor. The contents of lactones and volatile terpenoids in the experimental specimen were much higher than in the control. The organoleptic characteristics of experimental dry smoked sausage specimen were considerably better.     

The ecological significance of toxic nectar

Although plant-herbivore and plant-pollinator interactions have traditionally been studied separately, many traits are simultaneously under selection by both herbivores and pollinators. For example, secondary compounds commonly associated with herbivore defense have been found in the nectar of many plant species, and many plants produce nectar that is toxic or repellent to some floral visitors. Although secondary compounds in nectar and toxic nectar are geographically and phylogenetically widespread, their ecological significance is poorly understood. Several hypotheses have been proposed for the possible functions of toxic nectar, including encouraging specialist pollinators, deterring nectar robbers, preventing microbial degradation of nectar, and altering pollinator behavior. All of these hypotheses rest on the assumption that the benefits of toxic nectar must outweigh possible costs; however, to date no study has demonstrated that toxic nectar provides fitness benefits for any plant. Therefore, in addition to these adaptive hypotheses, we should also consider the hypothesis that toxic nectar provides no benefits or is tolerably detrimental to plants, and occurs due to previous selection pressures or pleiotropic constraints. For example, secondary compounds may be transported into nectar as a consequence of their presence in phloem, rather than due to direct selection for toxic nectar. Experimental approaches are necessary to understand the role of toxic nectar in plant-animal interactions.     

Apport de la tomographie par émission de positons au 18F-fluorodéoxyglucose (TEP-FDG) dans la prise en charge du cancer du canal anal

ObjectiveTo evaluate the contribution of FDG-PET in the management of anal carcinoma, with special emphasis on its impact on therapeutic strategy.Materials and methodsFrom March 2005 to August 2008, 48 PET were performed on 43 patients with anal epidermoid carcinoma, in initial staging (IS: 20 exams), therapeutic response assessment (TRA: 11), and recurrence assessment (RA: 17). We compared initial therapeutic strategies defined on conventional assessment results, to final ones chosen after PET.ResultsPET revealed lesions that were undetected by conventional investigation in 23% of cases (IS: 25%; TRA: 18%; RA: 23%) and cleared suspicious lesions in 21% of cases (IS: 10%; TRA: 18%; RA: 35%). It influenced the therapeutic strategy, and sometimes even modified it radically, in 44% of cases (IS: 35%; TRA: 54%; RA: 47%). This therapeutic impact was stronger in settings with diagnostic ambiguity, in which PET allowed to specify the diagnosis and to orientate consequently the therapeutic choice.ConclusionPET is interesting in the management of anal carcinoma, especially in uncertain diagnostic settings, in which the metabolic information brought allows to influence the therapeutic choice in almost half of the cases.     

The distribution of Escherichia coli recA protein bound to duplex DNA with single-stranded ends

A short single-stranded tail on one end of an otherwise duplex DNA molecule enables recA protein, in the presence of ATP and MgCl2, to form a complex with the DNA which extends into the duplex portion of the molecule. Nuclease protection studies at a concentration of MgCl2 which permits homologous pairing showed that cleavage by restriction endonucleases at sites throughout the duplex region was inhibited, whereas digestion by DNase I was not affected. These results indicate that recA protein binds to the duplex portion of tailed DNA allowing access by DNase I to a random sample of the many sites at which it cleaves, but providing limited protection of the relatively rare restriction sites. Electron microscopy revealed that the recA nucleoprotein complex with duplex DNA is indeed a segmented or interrupted filament that, with time, extends further from the single-stranded tail into the duplex region. recA protein binding extended into the duplex region more rapidly for duplexes with 5' tails than for those with 3' tails. These observations show that recA protein translocates from a single-stranded region into duplex DNA in the form of a segmented filament by a mechanism that is not strongly polarized.     

Seasonal changes in the cecal microflora of the high-arctic Svalbard reindeer (Rangifer tarandus platyrhynchus)

The dominant cecal bacteria in the high-arctic Svalbard reindeer were characterized, their population densities were estimated, and cecal pH was determined in summer, when food quality and availability is good, and in winter, when it is very poor. In summer the total culturable viable bacterial population was (8.9 +/- 5.3) X 10(8) cells ml-1, whereas in winter it was (1.5 +/- 0.7) X 10(8) cells ml-1, representing a decrease to 17% of the summer population density. Of the dominant species of cultured bacteria, Butyrivibrio fibrisolvens represented 23% in summer and 18% in winter. Streptococcus bovis represented 17% in summer and 5% in winter. Bacteroides ruminicola represented 10% in summer and 26% in winter. In summer and winter, respectively, the proportion of the viable population showing the following activities was as follows: fiber digestion, 36 and 48%; cellulolysis, 10 and 6%; xylanolysis, 33 and 48%; and starch utilization, 77 and 71%. The most abundant cellulolytic species in summer was Butyrivibrio fibrisolvens, representing 62% of the total cellulolytic population, and in winter it was Ruminococcus albus, representing 80% of the total cellulolytic population. The most abundant xylanolytic species in summer was Butyrivibrio fibrisolvens, and in winter it was Bacteroides ruminicola, representing 59 and 54% of the xylanolytic isolates in summer and winter, respectively. The cecal bacterial of the Svalbard reindeer have the ability to digest starch and the major structural carbohydrates of the diet that are not digested in the rumen. The cecum in these animals has the potential to contribute very substantially to the digestion of the available plant material in both summer and winter.     

Antiphytovirale Aktivität von Rhamnolipid aus Pseudomonas aeruginosa

A rhamnolipid released by Pseudomonas aeruginosa 196 Aa into the culture medium reduced the number of local lesions induced by tobacco mosaic virus on leaves of the hypersensitive host Nicotiana glutinosa L. by up to 90%. The content of potato virus X in the systemically infected host Nicotiana tabacum L. ‘Samsun’ is decreased in inoculated as well as in secondarily infected leaves by up to 50%. In a smaller degree red clover mottle virus is influenced in the systemic host Pisum sativumconvar.speciosum (Dierb.) Alef ‘Nadja’.     

Studies on a leukocyte elastase inhibitor present in the culture medium of inflamed synovial tissue

The spent medium of cultured inflamed synovial tissue contains a potent inhibitor of leukocyte elastase. This leukocyte elastase inhibitor has no effect on leukocyte cathepsin G and pancreatic elastase is only marginally affected. The inhibitor is a glycoprotein, stable to heat, acid and reductive alkylation. Pretreatment of the inhibitor with either trypsin or chymotrypsin results in its inactivation.     

Changes in the levels of wheat- and barley-germ agglutinin during embryogenesis in vivo,in vitro and during germination

Radioimmunoassay has been used to measure levels of wheat-germ agglutinin and barley-germ agglutinin during embryogenesis and germination. The two lectins exhibited similar patterns of accumulation during grain maturation in vivo and both decreased to low levels after imbibition of harvest-ripe grains for 3 d. Precocious germination of immature wheat and barley embryos excised and cultured in vitro could be prevented either by inclusion of abscisic acid or mannitol in the culture medium. Changes in the level of wheat-germ agglutinin induced by in vitro culture depended on the maturation stage of the embryo. No direct correlation was found between application of exogenous abscisic acid and accumulation of the lectin.