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G Cornelis

Publications and source records attributed to G Cornelis.

At least 55 records · Page 3Linked to original sources
PubMed1979

Multiple integration sites for the lactose transposon Tn 951 on plasmid RP 1 and establishment of a coordinate system for Tn 951.

Various molecules generated by transposition of the lactose transposon Tn 951 from plasmid pGC1 to plasmid RP1 were examined by DNA heteroduplex and restriction endonuclease analysis. Tn 951 was found to transpose to at least eight different sites on RP 1 in both possible orientations. A coordinate system for the lactose transposon Tn 951 is constructed.

DNA Restriction Enzymes↗
PubMed1978

Tn951: a new transposon carrying a lactose operon.

A new transposon, Tn951, is described, which derives from plasmid pGC1, originally isolated from Yersinia enterocolitica. Tn951 is 16.6 kb long and presumably flanked by small inverted repeats. It carries the lac genes i, z and y. This lac system is homologous to the E. coli lac operon. However, homology is restricted to 5.6 kb. The DNA sequences surrounding the lac operons on Tn951 and E. coli are nonhomologous. This leads to speculations about the origin of the E. coli lac operon itself.

Base Sequence↗
PubMed1978

Fermentation of raffinose by lactose-fermenting strains of Yersinia enterocolitica and by sucrose-fermenting strains of Escherichia coli.

Introduction of plasmids carrying the lacY gene (lactose permease gene) into Yersinia enterocolitica results in cells being able to ferment both lactose and raffinose. Transfer of such plasmids into Escherichia coli C600 (lacY) confers ability to ferment lactose but not raffinose. Derivatives of C600 that ferment both lactose and sucrose (Lac+ Scr+ strains) are able to ferment raffinose, but do not grow well on raffinose minimal medium. Fermentation of raffinose by Lac+ strains of Y. enterocolitica, and by Lac+ Scr+ strains of E. coli, is explained in terms of transport of raffinose via the lac permease and subsequent breakdown catalyzed by invertase.

Conjugation, Genetic↗
PubMed1976

Properties of pGC1, a lac plasmid orginating in Yersinia enterocolitica 842.

pGC1, a self-transmissible lac plasmid that originated in Yersinia enterocolitica 842, is described. This plasmid is freely transmissible between strains of Y. enterocolitica and from such strains to strains of Escherichia coli. The plasmid can also be transferref among G. coli strains and back to Y. enterocolitica, although at a greatly reduced frequency. pGC1 has a molecular weight of about 33.0 x 10(6), has a base composition of about 44 mol% guanine plus cytosine, and is fi-.

Conjugation, Genetic↗
PubMed1975

Beta-lactamases from Yersinia enterocolitica.

Two beta-lactamases, A and B, have been shown to be present in a strain of Yersinia enterocolitica (w222). Beta-Lactamase A hydrolyses a variety of penicillins and cephalosporins. This enzyme is sensitive to thiol reagents, is only partially inhibited by 0-1 mM-cloxacillin and has a molecular weight of approximatley 20,000.beta-Lactamase B shows strong cephalosporinase activity but does not hydrolyse some of the penicillins. It is more resistant than beta-lactamase A to thiol reagents, is completely inhibited by 0-1 mM-cloxacillin and has a molecular weight of about 34,000. With cephaloridine as a substrate, which is readily hydrolysed by both enzymes, about 85% of the total activity of a cell extract is due to beta-lactamase A and 15% to B. Addition of 6-aminopenicillanic acid to the culture during growth results in a 2-to4-fold selective increase in the amount of beta-lactamase B. Two beta-lactamases similar to enzymes A and B have been found in five other strains of Y. enterocolitica. In contrast, only one beta-lactamase, similar to enzyme B, has been detected in a different strain of Y. enterocolitica (H66), which is abnormal in that it is sensitive to ampicillin. Addition of 6-aminopenicillanic acid to cultures of this strain results in an 8-to 10-fold increase in beta-lactamase production.

Amidohydrolases↗
PubMed1975

Restriction of DNA in Yersinia enterocolitica detected by recipient ability for a derepressed R factor from Escherichia coli.

A derepressed R factor, RY2drd2, was transferred at a frequency of 5x10minus 3 between two strains of Yersinia enterocolitica mated on a membrane. Under the same conditions transfer of this R factor from Escherichia coli to Y. enterocolitica was observed at a frequency of only 7-7x10minus 6. This frequency was greatly increased when the recipient strain was heat-treated before mating. Heat exposure for optimum fertility was 50 to 52 degrees C for a period of 2 to 3 min. Mutants of Y. enterocolitica were isolated which were infected by RY2drd2 from E. coli or from Y. enterocolitica at the same frequency. These observations strongly suggest that a DNA restriction and modification system in Y. enterocolitica causes its low recipient ability for plasmids from other species.

Conjugation, Genetic↗
PubMed1975

Distribution of beta-lactamases A and B in some groups of Yersinia enterocolitica and their role in resistance.

Yersinia enterocolitica W222 (serological group 3) synthesized two different intracellular beta-lactamases, called A and B. Enzyme B was more sensitive than A to inhibition by cloxacillin. The minimum inhibitory concentrations of various beta-lactam antibiotics for strains of Y. enterocolitica of groups 3 and 9 and the effect of cloxacillin on these concentrations suggested differential roles for beta-lactamases of types A anb B in penicillin and cephalosporin resistance. Type B enzymes protected Y. enterocolitica against cephalothin and cephalosporin C, wheras type A enzymes protected very efficiently against carbenicillin. Protection against other beta-lactam antibiotics was exerted by both enzymes. However, while both enzymes readily hydrolysed cephaloridine and showed no crypticity with this substrate, they only conferred a very weak protection against it. This may be because cephaloridine reached its target quickly, before it was degraded. The resistance of strains of Y. enterocolitica from groups I, 2 and I6 was also explicable in terms of a two-enzyme system, whereas strains belonging to group 5b produced only a type B lactamase and were sensitive to carbenicillin.

Amidohydrolases↗