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

Iron is known to depress Shiga toxin production by Shigella dysenteriae 1, and temperature has been shown to regulate several genes required for Shigella invasiveness. In this study, the influence of iron and temperature on regulation of a highly related toxin, Shiga-like toxin I (SLT-I) of enterohemorrhagic Escherichia coli, was examined in strains lysogenic for the toxin-converting coliphage 933J and in strains carrying the cloned slt-I genes on a high-copy-number plasmid vector. For comparison, S. dysenteriae 1 was included in these studies. As expected, iron suppressed Shiga toxin synthesis, and reduced growth temperature was also found to decrease Shiga toxin production. Iron also suppressed SLT-I synthesis in E. coli lysogenized with phage 933J but did not demonstrably repress toxin synthesis in E. coli strains carrying the cloned slt-I genes. Temperature had no effect on SLT-I synthesis. Mini-Mu lac operon fusions were then isolated in the cloned slt-I genes and used to test for regulation of beta-galactosidase by iron. Iron did not decrease beta-galactosidase production in strains that harbored these operon fusion plasmids. Taken together, these results indicate that iron but not temperature represses SLT-I synthesis when the slt-I genes are phage associated but this suppression is not easily demonstrated when the slt-I genes are cloned on a high-copy-number plasmid.
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PMID:Effects of iron and temperature on Shiga-like toxin I production by Escherichia coli. 312 8

The ompA genes of Escherichia coli and Shigella dysenteriae have been used to construct a group of enterobacterial surface expression vectors for foreign genes. Linker oligonucleotides were inserted into the sequence corresponding to the third or fourth outer domain to allow in-frame sandwich fusion of foreign genes or epitopes into ompA. Influenza haemagglutinin was inserted without its leader peptide and anchor sequences and shown to be transferred as an ompA fusion protein to the bacterial surface in large amounts. The stability of this system depends on the stem structure (i.e. the bottom part) of the haemagglutinin unit which apparently initiates the folding process that extends into the ompA segment. This fusion construct can be used as a vector system and has been used to transfer to the bacterial surface several other proteins inserted into it, including beta-galactosidase, foot-and-mouth disease virus (FMDV) and malaria antigens. All are exported from the cytoplasm across both the inner and outer membranes to become exposed on the bacterial surface. Very hydrophobic segments or inserts with distinct secondary structures, such as the capsid protein, VP1 of FMDV, will, however, block this process.
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PMID:OmpA fusion proteins for presentation of foreign antigens on the bacterial outer membrane. 779 62

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