[Occurrence of verotoxin-producing Escherichia coli (VTEC) in fecal swabs from slaughter cattle and sheep--an observation from a meat hygiene view]. / Vorkommen verotoxinbildender Escherichia coli (VTEC) in Kottupfern von Schlachtrindern und Schlachtschafen--eine Betrachtung aus fleischhygienischer Sicht.

Fecal samples from 544 beef cattle and 140 sheep were investigated by PCR for verotoxin (VT)-producing Escherichia coli (VTEC) without and with an enrichment step. 6.1% (after enrichment 14%) of cattle samples and 10% (after enrichment 29.2%) of sheep samples were VT-PCR-positive. Moreover, a noticeable age-depending prevalence in cattle was found. Eleven VTEC strains isolated from fecal samples of 5 cattle and 6 sheep were taken for further characterization. None of the strains belonged to serogroup O157. But, as reported previously, we also found in this study strains with virulence genes that are associated with increased pathogenicity. The importance of slaughter hygiene and of bacteriological monitoring of carcass contamination has to be pointed out.

Changes of glaciers in the Andes of Chile and priorities for future work.

Glaciers in the Andes of Chile seem to be shrinking and possibly loosing mass, but the number and types of studies conducted, constrained mainly by data availability, are not sufficient to provide a synopsis of glacier changes for the past or future or explain in an explicit way causes of the observed changes. In this paper, we provide a systematic review of changes in glaciers for the entire country, followed by a discussion of the studies that have provided evidence of such changes. We identify a missing type of work in distributed, physically-oriented modelling studies that are needed to bridge the gap between the numerous remote sensing studies and the specific, point scale works focused on process understanding. We use an advanced mass balance model applied to one of the best monitored glaciers in the region to investigate four main research issues that should be addressed in modelling studies for a sound assessment of glacier changes: 1) the use of physically-based models of glacier ablation (energy balance models) versus more empirical models (enhanced temperature index approaches); 2) the importance of the correct extrapolation of air temperature forcing on glaciers and in high elevation areas and the large uncertainty in model outputs associated with it; 3) the role played by snow gravitational redistribution; and 4) the uncertainty associated with future climate scenarios. We quantify differences in model outputs associated with each of these choices, and conclude with suggestions for future work directions.

Prevalence and characteristics of verotoxin-producing Escherichia coli (VTEC) in stool samples from asymptomatic human carriers working in the meat processing industry in Switzerland.

A total of 5590 stool samples from healthy employees in the meat industry were screened by PCR for verotoxin-producing Escherichia coli (VTEC). The PCR product of VT-encoding genes was detected in 3. 5% of the samples. Phenotypic and genotypic traits of 47 VTEC strains isolated from asymptomatic carriers were characterized. A variety of serotypes was found; one strain belonged to the serotype O157:H7. The majority of the isolates proved to be VT2-positive. Fifty-seven percent of the verotoxin-producing strains harboured the genes for one or several additional virulence associated factors, including intimin (eae, 8.5%), the 60 MDa plasmid (42.5%), enterohaemolysin (EHEC-hlyA, 38.3%), the heat-stable enterotoxin (astA, 6.4%), a serin protease (espP, 6.4%), colicin production (col D157, 12.8%) and a secretion system II (etpD, 10.6%). None of the strains was positive for a specific enzyme with catalase-peroxidase activity (katP).

A family of flavoproteins in the domains Archaea and Bacteria.

A family of flavoproteins, called A-type flavoproteins, is described. It consists of 14 protein sequences of 385-597 amino acids in length, 7 from methanogens (domain: Archaea), 5 from phototrophic prokaryotes, one from Escherichia coli, and a partial sequence from the sulfate reducer Desulfovibrio gigas (domain: Bacteria). No similar sequence could be found in the domain Eucarya. All sequences show significant similarity over a 385-400 amino acid portion overlapping a recognizable flavodoxin signature starting at positions 245-285 of the common core sequence. Cofactor analysis and, to some extent, analysis of the primary structure of six A-type flavoproteins, three of which are structurally characterized here, support the existence of four sub-families: (a) simple flavoproteins binding only FMN; (b) diflavin flavoproteins binding FMN and FAD; (c) a flavorubredoxin binding FMN and iron; (d) a hemoflavoprotein. The possible involvement of A-type flavoproteins in the metabolism of oxygen, as suggested for D. gigas hemoflavoprotein [Gomes, C. M., Silva, G., Oliveira, S., LeGall, J., Liu, M.-Y., Xavier, A. V., Rodrigues-Pousada, C. & Teixeira, M. (1997) J. Biol. Chem. 272, 22502-22508], is discussed.

Characterization of Methanobacterium thermoautotrophicum Marburg mutants defective in regulation of L-tryptophan biosynthesis.

Three nitrosoguanidine-induced mutants of the archaeon Methanobacterium thermoautotrophicum Marburg resistant to 5-methyltryptophan were isolated and characterized. They were found to take up L-tryptophan, as wild-type cells, via an energy-dependent, low-affinity transport system specific for L-tryptophan, with a Km of 300 microM and a Vmax of 7 nmol/mg (dry weight)/min. Resistance to 5-methyltryptophan was not due to feedback-resistant anthranilate synthase but to constitutive expression of the trp genes, as measured by the specific activities of anthranilate synthase and tryptophan synthase, the enzymes encoded by trpEG and trpB, respectively, of the trpEGCFBAD gene cluster. Estimation of trpE mRNA obtained from mutant cells grown in minimal medium with or without L-tryptophan suggested that constitutive expression resulted from deficient transcriptional regulation. The enhanced expression of the trp genes in the mutants was found to result in intracellular L-tryptophan pools that were two- to fourfold higher than in the wild type. Sequencing of the region upstream of trpE revealed in two mutants point mutations mapping on the 5'-side of the archaeal box A, whereas in the third mutant this region did not differ from that of the wild type. These results suggest that (i) in M. thermoautotrophicum the 5-methyltryptophan-resistant phenotype arises from lesions in components of a regulatory system controlling transcription of the trp genes and (ii) cis-acting sequence elements in front of the trpE promoter may form part of this system.