Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Southern hybridization analysis revealed that the region homologous to Escherichia coli lacZ was present on the chromosomal DNAs of beta-galactosidase-positive Shigella strains, such as Shigella dysenteriae serovar 1 and Shigella sonnei strains, whereas this region was absent from chromosomal DNAs of beta-galactosidase-negative strains of Shigella flexneri and Shigella boydii. We found that the lacY-A region was deficient in S. dysenteriae serovar 1 and believe that this is the reason for the slow fermentation of lactose by this strain. S. sonnei strains possessed the region which hybridized with E. coli lacY-A despite their slow hydrolysis of lactose. The whole lactose-fermenting region was cloned from S. sonnei and compared with the cloned lac operon of E. coli K-12. Both clones directed the synthesis of beta-galactosidase in an E. coli K-12 strain lacking indigenous beta-galactosidase activity (strain JM109-1), and we observed no difference in the expression of beta-galactosidase activity in S. sonnei and E. coli. However, E. coli JM109-1 harboring the lactose-fermenting genes of S. sonnei exhibited the slow lactose fermentation phenotype like the parental strain. S. sonnei strains had no detectable lactose permease activities. E. coli JM109-1 harboring the lactose-fermenting genes of S. sonnei had a detectable permease activity, possibly because of the multicopy nature of the cloned genes, but this permease activity was much lower than that of strain JM109-1 harboring the lac operon of E. coli K-12. From these results we concluded that slow lactose fermentation by S. sonnei is due to weak lactose permease activity.
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PMID:Possible mechanisms underlying the slow lactose fermentation phenotype in Shigella spp. 174 53

One hundred and fourteen strains of non-lactose fermenters and 127 lactose fermenters on MacConkey's agar have been compared in the 5% and 1% lactose tests and in beta-galactosidase production, using ortho-nitro-phenyl-beta-D-galactopyranoside (O.N.P.G.) as a test substance. The superiority of the O.N.P.G. test in the number of positive results and its rapidity is shown. In general, late or non-lactose fermenting strains of genera, usually lactose-positive, yield a rapidly positive O.N.P.G. reaction. Forty-one wild strains of Salmonella, Proteus, Providencia, and Pseudomonas aeruginosa were found negative in all three tests. Of 1,075 stock strains of Salmonella examined in the O.N.P.G. test, all were negative except nine; four of these were lactose-positive strains. For practical purposes, Salmonella strains in Great Britain may be regarded as O.N.P.G. negative. Among 100 stock strains of Arizona there was considerable variation of behaviour in the O.N.P.G. test and in the 5% and 1% lactose tests. Most strains of Arizona can be considered to yield a positive O.N.P.G. test but a minority give a negative result. The test is recommended for routine use in the differentiation of Salmonella from other enterobacteria and for use in bacterial identification. The 5% lactose fermentation test in parallel is suggested when the O.N.P.G. test is used for isolating routine pathogens, because organisms such as Shigella sonnei, Shigella dysenteriae 1, and Pasteurella pseudotuberculosis are O.N.P.G. positive.
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PMID:BETA-GALACTOSIDASE AND LACTOSE FERMENTATION IN THE IDENTIFICATION OF ENTEROBACTERIA INCLUDING SALMONELLAE. 1414 33

The chief function of the Cpx two-component system is perceiving various cell envelope stresses, but CpxR is also known to regulate the expression of the type III secretion system (TTSS) of Shigella sonnei through transcription of the primary regulator virF. Here, we have isolated novel cpxA mutants that exhibited decreased TTSS expression from Escherichia coli HW1273, which carries the virulence plasmid of S. sonnei. The cpxA deletion strain of HW1273 expressed beta-galactosidase activity levels from the virF-lacZ fusion similar to those of HW1273. However, the second regulator InvE (VirB) and the TTSS component IpaB proteins were apparently expressed at a low level. In the cpxA strain, beta-galactosidase activity levels from the invE-lacZ transcriptional fusion remained similar to those of HW1273, whereas the beta-galactosidase activity level from the translational fusion of invE-lacZ was reduced to 21% of that of HW1273. Therefore, the deletion of the cpxA gene influenced TTSS expression chiefly at the posttranscriptional processing of InvE. In addition, the cpxA deletion strain of S. sonnei showed the same phenotype. These results indicate that the Cpx two-component system is involved in virulence expression through posttranscriptional processing of the regulatory protein InvE, a novel feature of the Cpx two-component system in posttranscriptional processing and virulence expression of Shigella.
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PMID:A sensor of the two-component system CpxA affects expression of the type III secretion system through posttranscriptional processing of InvE. 1560 94