A mutation effecting gluconate catabolism in Escherichia coli: The locus for the main high affinity transport / Una mutación que afecta el catabolismo del gluconato en Escherichia coli: el locus para el transporte principal de alta afinidad

The bioH-malA region of the E.coli chromosome (min 75.5) includes the gntT gene which encodes a high affinity transport for gluconate. Other gnt loci have not been characterized in this region; nevertheless, because lesion in it affect severely the utilization of gluconate, it has been suggested as being more complex. This region was investigated with respect to gluconate catabolism through the characterization of suitable E.coli strains lysogenized with a specialized transducing phage carrying the bioH-malA region of the bacterial chromosome (cI857st68h80d2bioH-malA). It was found that the region transduced by this phage while includes the gntT gene lacks other gnt loci that might code additional activities for transport of gluconate or its phosphorylation. Moreover, the pleiotropic lesion gntM2, previously mapped into this region and suggested as altering gntT or a presumptive regulator gene that might be involved in this catabolism, resulted recessive in lysogens (partial diploids) containing the defective prophage. The results obtained supported the idea that gntM2 is an allele of gntT; consequently those results suggested the precise position of this gene on the cromosomic map and the central role that its product might have in the initial incorporation of gluconate in E.coli.

Tratamientos analíticos de muestras de IFN alfa 2b h-rec, para su cuantificación por ELISA / Analyticaltreatments of rec-h alpha 2b interferon samples for their quantitation by ELISA

La obtención de interferón 2b humanos recombinante (IFN alfa 2b hr) en E. coli, en forma insoluble, hace necesario el estudio del ratamiento de las muestras para su cuantificación mediante un sistema inmunoenzimático tipo ELISA. De los sistemas analíticos ensayados para la extracción de proteina insoluble, el óptimo resultó una modificación del tapón L aemmli con un 1 % de SDS y 2,5 % de 2-merceptoetanol. Las proteinas de la cepa productora y la mayoría de los sistemas tampones empleados no influyeron sobre el reconocimiento inmunológico del interferón a diluciones mayores de 1/500

Recombinant fusion protein for simple detection of Escherichia coli heat-stable enterotoxin by GM1 enzyme-linked immunosorbent assay.

A recombinant gene fusion protein composed of an Escherichia coli heat-stable enterotoxin (STa) peptide epitope fused to the amino end of the cholera toxin B subunit was used to detect STa produced by clinical isolates of enterotoxigenic E. coli (STa-ETEC) by a single monoclonal antibody-based inhibition GM1 enzyme-linked immunosorbent assay. In this test, 100% sensitivity and 100% specificity were observed for use of the recombinant protein in either its purified form or as crude Vibrio cholerae culture supernatants in detection of STa-ETEC.

Fimbria-like adhesive factor (EAF 44) from verocytotoxigenic Escherichia coli of bovine origin.

An adhesin with fimbria-like properties was present in four strains of verocytotoxigenic Escherichia coli isolated from diarrhoeic calves in Brazil.

Production, purification and partial characterization of a new adhesive factor (F42) produced by enterotoxigenic Escherichia coli isolated from pigs.

Production of the F42 adhesive factor by porcine enterotoxigenic Escherichia coli (ETEC) grown on minimal solid medium was glucose-dependent. The addition of alanine and sodium acetate to this medium repressed the expression of this antigen whose production was also inhibited when the pH of the growing medium was lower than 7.4. The antigen was extracted from F42-positive ETEC grown in minimal liquid medium supplemented with 0.5% glucose. The cells were suspended in buffered 1 M NaCl and heated at 60 degrees C. The supernatant was then treated with ammonium sulphate and the resulting precipitate treated with deoxycholate followed by chromatography of the deoxycholate-soluble material on Sepharose-4B. The molecular weight of F42 purified antigen was near 31,000 daltons and its pI 3.2, as determined by polyacrylamide gel electrophoresis and isoelectric focusing, respectively. Immunoelectrophoretic studies showed that the purified F42 antigen presented a slight anodic migration and was recognized only by its homologous antiserum.

Diagnóstico presuntivo de Escherichia coli enterotoxigênica através de provas de hemoaglutinaçäo / Presumptive diagnosis of enterotoxigenic Escherichia coli by hemagglutination tests

Foram realizadas provas de hemoaglutinaçäo empregando-se hemácias bovinas e humanas, com o objetivo de se comparar os padröes de hemoaglutinaçäo apresentados por amostras de Escherichia coli enterotoxigênicas e enteropatogênicas clássicas e näo enteropatogênicas e averiguar se este procedimento poderia ser empregado para uma demonstraçäo presuntiva de amostras enterotoxigênicas. A análise estatística, através do teste do X2 (p <0,01), evidenciou diferenças significativas entre os padröes de hemoaglutinaçäo exibidos pelas amostras enterotoxigênicas e amostras näo produtoras de enterotoxinas. Este resultado, acrescido do fato de que o método é simples, rápido e barato recomenda o seu emprego no diagnóstico presuntivo de Escherichia coli enterotoxigênica, pois, a pesquisa de enterotoxinas é um procedimento praticamente impossível de ser realizado, rotineiramente, por laboratórios de diagnóstico

Preliminary characterization of Escherichia coli isolated from pigs with diarrhoea in Venezuela.

The aetiology of neonatal porcine diarrhoea was studied in 15 different herds located in the north-western region of Venezuela. Of 56 strains of Escherichia coli analyzed, 16 (28.6%) were shown to produce heat-stable (STa) enterotoxin, as detected by infant mouse assay. Only four of these STa+ isolates also possessed the K88 pilus antigen, two were 987P+ and none possessed the K99 antigen, leaving 10 STa+ samples in which no pilus antigen was identified. Among the 40 STa negative samples were six K88+ specimens, one K99+, four 987P+, one which reacted as K88+ + K99+ and one K88+ + 987P+. Considering as pathogenic any strain showing at least one of the characters studied, pathogenic E. coli were detected with an overall frequency of 42.9%, being more prevalent during the second week of life. An electrophoretic analysis of the plasmid content of the field isolates of E. coli, revealed the presence of numerous species of extrachromosomal DNA, although no direction association could be made between a particular plasmid and any of the pathogenic characteristics identified. Results of Southern blot analysis indicate that the STa enterotoxin was preferentially encoded within an endemic plasmid of 4.9 Md. Other plasmids present in the E. coli isolates could be related to antibiotic resistance. With the exception of one strain, all E. coli isolates were resistant to more than one of the nine drugs tested; multiresistant E. coli were frequently isolated, including four strains which were resistant to seven antibiotics.

Survival and enumeration of the fecal indicators Bifidobacterium adolescentis and Escherichia coli in a tropical rain forest watershed.

The density of Bifidobacterium spp., fecal coliforms, Escherichia coli, and total anaerobic bacteria, acridine orange direct counts, percentages of total bacterial community activity and respiration, and 12 physical and chemical parameters were measured simultaneously at six sites for 12 months in the Mameyes River rain forest watershed, Puerto Rico. The densities of all bacteria were higher than those reported for uncontaminated temperate rivers, even though other water quality parameters would indicate that all uncontaminated sites were oligotrophic. The highest densities for all indicator bacteria were at the site receiving sewage effluent; however, the highest elevation site in the watershed had the next highest densities. Correlations between bacterial densities, nitrates, temperature, phosphates, and total phosphorus indicated that all viable counts were related to nutrient levels, regardless of the site sampled. In situ diffusion chamber studies at two different sites indicated that E. coli could survive, remain physiologically active, and regrow at rates that were dependent on nutrient levels of the ambient waters. Bifidobacterium adolescentis did not survive at either site but did show different rates of decline and physiological activity at the two sites. Bifidobacteria show promise as a better indicator of recent fecal contamination in tropical freshwaters than E. coli or fecal coliforms; however, the YN-6 medium did not prove to be effective for enumeration of bifidobacteria. The coliform maximum contaminant levels for assessing water usability for drinking and recreation appear to be unworkable in tropical freshwaters.

Studies on phage internal proteins. VI. Interaction of bacteriophage T4 internal proteins with T4 DNA in vivo and in vitro.

Internal proteins are basic proteins bound to the DNA of T4 coliphage. Centrifugation in sucrose gradients was employed to isolate DNA-internal proteins complexes formed in vitro. Polyacrylamide gel electrophoresis of radioactive internal proteins in the presence of sodium dodecyl sulfate followed by autoradiography of the gels was used to identify the DNA-bound proteins and to determine their respective abundance in these complexes as well as in the bacteriophage head. The internal proteins were found to bind to the phage DNA (in vitro experiments) at the same ratio as that of internal proteins associated with the viral DNA within the phage head (in vivo binding).