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 total of 314 strains of Haemophilus, isolated from clinical samples, were studied for the production of beta-galactosidase and beta-xylosidase. None of the H. influenzae strains studied (9 beta-lactamase positive strains and 129 beta-lactamase negative strains) possessed these enzymes. Both enzymes were almost constantly observed among strains of H. paraphrophilus (10 strains studied) and of H. paraphrohaemolyticus (9 strains studied). Among the other species (H. parainfluenzae, 55 strains; H. haemolyticus, 5 strains; H. parahaemolyticus, 97 strains), beta-galactosidase was present in about 30% of the strains studied whereas beta-xylosidase was detected occasionally (3% of the strains studied). Detection of these two enzymes could be a valuable test for the taxonomic study of the genus Haemophilus. However, the type of substrate used for the detection of beta-xylosidase is important: use of the para-nitro-phenyl-beta-xylopyranoside yielded more positive results than the use of its ortho-isomer.
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PMID:Significance of the detection of beta-galactosidase and of beta-xylosidase in the taxonomic study of the genus Haemophilus. 11 91

Possible Haemophilus influenzae colonies in cultures of sputum samples are currently identified by tests for dependence on X and V factors. This method requires further overnight culture and may give a relatively high number of false negative results. Identification of suspected H. influenzae colonies by a 5-min test for production of indole and beta-galactosidase followed by a 1-h porphyrin test was compared with tests for dependence on X and V factors. A commercially produced form of the rapid tests (Haemstrip, Lab M, Bury, Lancs) was used to test 252 potential haemophilus colonies from cultures of sputum samples on heated blood agar. Colonies that were beta-galactosidase-positive after 5 min were considered to be non-H. influenzae and those that were beta-galactosidase-negative but indole-positive were considered to be H. influenzae. At this stage the test had a sensitivity of 99.4% and a specificity of 90.9%. After 1 h, only colonies that were beta-galactosidase- and porphyrin-negative were considered to be H. influenzae, the sensitivity was then 99.5% and the specificity 100%. Similar results were found with colonies from sputum cultures on selective heated blood agar containing bacitracin. The X and V dependence and Haemstrip results were in 97.6% agreement in a double blind test. Of 100 non-haemophilus colonies tested by Haemstrip, two pseudomonads could have been identified as H. influenzae by this method. The high positive predictive value of Haemstrip results depends partly on the initial recognition of potential haemophilus colonies.
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PMID:Provisional identification of Haemophilus influenzae from sputum cultures within 1 h by rapid enzyme tests. 190 45

DNA sequencing, RNA mapping, and protein expression experiments revealed the presence of a gene, tfoX+, encoding a 24.9-kDa polypeptide, that is transcribed divergently from a common promoter region with the Haemophilus influenzae rec-1+ gene. H. influenzae strains mutant for tfoX failed to bind transforming DNA and were transformation deficient. Primer extension experiments utilizing in vivo total RNA from precompetent and competent H. influenzae cells demonstrated that transcription of tfoX+ increased immediately upon competence induction, suggesting that tfoX+ is an early competence gene. Similar experiments showed that the expression of the late competence-specific gene, com101A+, was tfoX+ dependent. Moreover, expression of plasmid-borne tfoX+ in H. influenzae resulted in constitutive competence. The addition of cyclic adenosine monophosphate (cAMP) to strains carrying a tfoX::lacZ operon fusion resulted in an immediate increase in beta-galactosidase activity that correlated with an increase in genetic transformability. Collectively, our results suggest that TfoX may play a key role in the development of genetic competence by regulating the expression of late competence-specific genes.
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PMID:Identification of a DNA transformation gene required for com101A+ expression and supertransformer phenotype in Haemophilus influenzae. 772 7

Changes in intracellular 3',5' cyclic AMP (cAMP) concentration regulate the development of natural competence in Haemophilus influenzae. In Escherichia coli, cAMP levels are modulated by a cAMP phosphodiesterase encoded by the cpdA gene. We have used several approaches to demonstrate that the homologous icc gene of H. influenzae encodes a functional cAMP phosphodiesterase and that this gene limits intracellular cAMP and thereby influences competence and other cAMP-dependent processes. In E. coli, expression of cloned icc reduced both cAMP-dependent sugar fermentation and beta-galactosidase expression, as has been shown for cpdA. In H. influenzae, an icc null mutation increased cAMP-dependent sugar fermentation and competence development in strains where these processes are limited by mutations reducing cAMP synthesis. When endogenous production of cAMP was eliminated by a cya mutation, an icc strain was 10,000-fold more sensitive to exogenous cAMP than an icc+ strain. The icc strain showed moderately elevated competence under noninducing conditions, as expected, but had subnormal competence increases at onset of stationary phase in rich medium, and on transfer to a nutrient-limited medium, suggesting that excessive cAMP may interfere with induction. Consistent with this finding, a cya strain cultured in 1 mM cAMP failed to develop maximal competence on transfer to inducing conditions. Thus, by limiting cAMP levels, the H. influenzae cAMP phosphodiesterase may coordinate its responses to nutritional stress, ensuring optimal competence development.
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PMID:A 3',5' cyclic AMP (cAMP) phosphodiesterase modulates cAMP levels and optimizes competence in Haemophilus influenzae Rd. 972 Dec 75

The small DNA binding protein Fis is involved in several different biological processes in Escherichia coli. It has been shown to stimulate DNA inversion reactions mediated by the Hin family of recombinases, stimulate integration and excision of phage lambda genome, regulate the transcription of several different genes including those of stable RNA operons, and regulate the initiation of DNA replication at oriC. fis has also been isolated from Salmonella typhimurium, and the genomic sequence of Haemophilus influenzae reveals its presence in this bacteria. This work extends the characterization of fis to other organisms. Very similar fis operon structures were identified in the enteric bacteria Klebsiella pneumoniae, Serratia marcescens, Erwinia carotovora, and Proteus vulgaris but not in several nonenteric bacteria. We found that the deduced amino acid sequences for Fis are 100% identical in K. pneumoniae, S. marcescens, E. coli, and S. typhimurium and 96 to 98% identical when E. carotovora and P. vulgaris Fis are considered. The deduced amino acid sequence for H. influenzae Fis is about 80% identical and 90% similar to Fis in enteric bacteria. However, in spite of these similarities, the E. carotovora, P. vulgaris, and H. influenzae Fis proteins are not functionally identical. An open reading frame (ORF1) preceding fis in E. coli is also found in all these bacteria, and their deduced amino acid sequences are also very similar. The sequence preceding ORF1 in the enteric bacteria showed a very strong similarity to the E. coli fis P region from -53 to +27 and the region around -116 containing an ihf binding site. Both beta-galactosidase assays and primer extension assays showed that these regions function as promoters in vivo and are subject to growth phase-dependent regulation. However, their promoter strengths vary, as do their responses to Fis autoregulation and integration host factor stimulation.
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PMID:Identification and characterization of the fis operon in enteric bacteria. 981 52