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)

We have isolated promoters inducible by paraquat, a superoxide radical-generating agent, from Escherichia coli, using promoter-probing plasmid pJAC4 (Y.S. Koh and J.H. Roe, Korean J. Microbiol. 31:267-273, 1993). One promoter clone pqi-5 (pqi denotes paraquat-inducible gene) was mapped at 21.8 min on the E. coli chromosome by using the Kohara phage library. We constructed an operon fusion of the lacZ gene with the pqi-5 promoter to monitor the expression of the gene in the single-copy state. LacZ expression was induced about 7- to 13-fold by 77 to 780 microM paraquat. Other known superoxide generators such as menadione, phenazine methosulfate, and plumbagin also induced the expression of beta-galactosidase in this fusion strain. On the other hand, no significant induction was observed with treatment with hydrogen peroxide, ethanol, and heat shock. Induction of beta-galactosidase was significantly reduced by introducing a delta sox-8::cat or soxS3::Tn10 mutation into the fusion strain, indicating that pqi-5 is a member of the soxRS regulon. A DNA fragment containing the pqi-5 promoter was cloned and sequenced from the Kohara phage E2E5. We identified two pqi-5 open reading frames (ORFs); ORF-A encodes a predicted protein of 342 amino acids, and ORF-B is truncated at the cloning site. The transcription start site from the pqi-5 promoter was determined by primer extension and S1 nuclease protection analyses. Northern (RNA) and S1 analyses indicated that there are two kinds of pqi-5 transcript; one covers ORF-A only and the other covers ORF-A and possibly also ORF-B.
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PMID:Isolation of a novel paraquat-inducible (pqi) gene regulated by the soxRS locus in Escherichia coli. 775 Dec 75

The root-associated biological control bacterium Pseudomonas aureofaciens 30-84 produces a range of exoproducts, including protease and phenazines. Phenazine antibiotic biosynthesis by phzXYFABCD is regulated in part by the PhzR-PhzI quorum-sensing system. Mutants defective in phzR or phzI produce very low levels of phenazines but wild-type levels of exoprotease. In the present study, a second genomic region of strain 30-84 was identified that, when present in trans, increased beta-galactosidase activity in a genomic phzB::lacZ reporter and partially restored phenazine production to a phzR mutant. Sequence analysis identified two adjacent genes, csaR and csaI, that encode members of the LuxR-LuxI family of regulatory proteins. No putative promoter region is present upstream of the csaI start codon and no lux box-like element was found in either the csaR promoter or the 30-bp intergenic region between csaR and csaI. Both the PhzR-PhzI and CsaR-CsaI systems are regulated by the GacS-GacA two-component regulatory system. In contrast to the multicopy effects of csaR and csaI in trans, a genomic csaR mutant (30-84R2) and a csaI mutant (30-84I2) did not exhibit altered phenazine production in vitro or in situ, indicating that the CsaR-CsaI system is not involved in phenazine regulation in strain 30-84. Both mutants also produced wild-type levels of protease. However, disruption of both csaI and phzI or both csaR and phzR eliminated both phenazine and protease production completely. Thus, the two quorum-sensing systems do not interact for phenazine regulation but do interact for protease regulation. Additionally, the CsaI N-acylhomoserine lactone (AHL) signal was not recognized by the phenazine AHL reporter 30-84I/Z but was recognized by the AHL reporters Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136(pCF240). Inactivation of csaR resulted in a smooth mucoid colony phenotype and formation of cell aggregates in broth, suggesting that CsaR is involved in regulating biosynthesis of cell surface components. Strain 30-84I/I2 exhibited mucoid colony and clumping phenotypes similar to those of 30-84R2. Both phenotypes were reversed by complementation with csaR-csaI or by the addition of the CsaI AHL signal. Both quorum-sensing systems play a role in colonization by strain 30-84. Whereas loss of PhzR resulted in a 6.6-fold decrease in colonization by strain 30-84 on wheat roots in natural soil, a phzR csaR double mutant resulted in a 47-fold decrease. These data suggest that gene(s) regulated by the CsaR-CsaI system also plays a role in the rhizosphere competence of P. aureofaciens 30-84.
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PMID:A second quorum-sensing system regulates cell surface properties but not phenazine antibiotic production in Pseudomonas aureofaciens. 1152 37

In previous study, it has already been confirmed that the wild type strain of Pseudomonas sp. M18 isolated from the agricultural soil can produce two antifungal agents phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt). Biosynthesis and secretion of these secondary metabolites contribute to its biological control and suppression of soilborne pathogenic fungi. As main regulators, GacA and RsmA differentially exert global regulation on production of PCA and Plt, respectively. In order to study the regulatory mechanism of secondary metabolites production in Pseudomonas sp. M18, a gacArsmA double mutant, designated as M18GR, was constructed with insertional mutation. Then, the mutant M18G, M18R, M18GR and the wild type strain M18 were inoculated into PPM or King's medium B (KMB), respectively. During cultivation of strain M18 and its derivatives, their PCA and Pit were respectively detected with High Performance Liquid Chromatography (HPLC). The results showed that PCA production in the mutant M18GR was lower than that in the mutant M18G and higher than that in the mutant M18R. Plt production in the mutant M18GR was, however, much less than that in the mutant M18R and much more than that in the strain M18 and the mutant M18G. With these observations, it is tempting to suggest that biosynthesis of PCA and Plt regulated by GacA or RsmA seem to occur at posttranscriptional level, not at transcriptional level. This regulation on secondary metabolites seems to be indirectly mediated by other unknown factors. Meanwhile, based on the construction of two translational fusions, gacA'-'lacZ and rsmA'-'lacZ, the assay of beta-galactosidase activities in KMB medium indicated that both GacA and RsmA did not have autoinduction of their own gene expression, respectively. Although GacA did not influence expression of the rsmA gene, RsmA could exert some positive influence on the gacA gene expression in Pseudomonas sp. M18.
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PMID:[Analysis of mechanism and relationship of GacA and RsmA, two regulators of antibiotics production in Pseudomonas sp. M18]. 1703 49

In Gram-negative bacteria, global regulator QscR controls the expression of many virulence determinants, secondary metabolites, stationary phase genes and genes involved in biofilm formation through quorum sensing (QS) systems. QscR binds the promoter region of target genes and regulates the gene expression at the transcriptional level. Using homologous recombination technique a chromosomal qscR inactivated mutant strain M-18Q was constructed in Pseudomonas sp. M-18, a strain of plant-growth-promoting rhizobacteria, which could inhibit several soilborn phytopathogens by producing secondary metabolites including phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt) in one single strain. To further study the effect of QscR on the synthesis of Plt and PCA in the wild type strain M-18, the dynamic curves of Plt and PCA produced respectively by M-18 and M-18Q strains were measured in both KMB and PPM mediums. The synthesis of PCA was much more activated in the mutant than in the wild type both in KMB and PPM mediums. The PCA production in the mutant strain is four-to-six fold over that in the wild type in the PPM medium, reaching 480 pg/mL, and three-to-five fold in the KMB medium, reaching 140 microg/mL. The synthesis of Plt, however, was not detected in PPM medium and was nearly not influenced by the QscR protein in KMB medium. PCA production was inhibited but Plt biosynthesis was not altered after complementation with qscR gene in trans in the strain of M-18Q. The regulation of qscR gene on PCA production was further confirmed by the analysis of beta-galactosidase activities from the translational phzA '-' lacZ fusion, in which phzA is the first enzyme gene of the phenazine biosynthesis pathway. These results indicate that QscR can control PCA production negatively but not Plt production in M-18, and show that QscR functions as a global regulator to differently regulate the synthesis of PCA and Plt on the gene expression level.
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PMID:[Construction of Pseudomonas sp. M18 qscR- mutant and its regulation on biosynthesis of PCA and Plt]. 1755 30

A new bacterium with potential biocontrol ability, Pseudomonas sp. M18, was isolated from the soil of agricultural field in suburb of Shanghai (China). It had been demonstrated that biosynthesis and secretion of phenazine-1-carboxylic acid and pyoluteorin in Pseudomonas sp. M18 contributes to its suppression of soilborne pathogens. In order to study the correlation and regulatory mechanism of two antifungal compounds biosynthesis, the mutant M18T and M18Z1 were constructed with insertion of the gentamycin resistance gene cassette (aacC1), respectively. With introduction of the translational fusion pMEAZ (pltA'-' lacZ) into the wild type strain MI8 or the pit-mutant M18T, respectively, it was found that beta-galactosidase activities of the mutant M18T (pMEAZ) are remarkably enhanced by adding a certain amount of pyoluteorin in KMB medium. The results indicated that pyoluteorin might positively autoinduce expression of the pit gene loci. In investigating the correlation of two antifungal agents, it was showed that the pyoluteorin-negative mutant MI8T produces the same level of phenazine-1-carboxylic acid in comparison with the wild type strain M18. Overexpression of the plt gene loci does not result in decrease of phenazine-1-carboxylic acid in a pltZ-mutant of Pseudomonas sp. M18. However, the distinct decrease of phenazine-1-carboxylic acid biosynthesis does lead to enhanced biosynthesis of pyoluteorin in the mutant M18Z1. Addition of phenazine-1-carboxylic acid in KMB medium makes the mutant M18S produce less pyoluteorin. These results indicated that a special correlation of secondary antifungal agents biosynthesis seems to be existed in Pseudomonas sp. M18, i.e., production of pyoluteorin does not exert any influence on expression of the phz gene cluster, while phenazine-1-carboxylic acid makes negative impact on the biosynthesis of pyoluteorin.
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PMID:[Autoinduction of pyoluteorin and correlation between phenazine-1-carboxylic acid and pyoluteorin in Pseudomonas sp. M18]. 1767 2

The qscR gene, encoding a quorum sensing regulator, was cloned and the qscR-null mutant strain M-18Q derived from Pseudomonas sp. M-18 was constructed to study the effect of the qscR gene on biosynthesis of phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt) in strain M-18. Results showed that the PCA produced in the mutant increased four- to six-fold, while the synthesis of Plt was barely influenced in comparison with the wild type. The results were confirmed by complementation with the qscR gene in trans in strain M-18Q. The negative effect of the qscR gene on PCA production was further confirmed by analysis of beta-galactosidase activities from the translational phzA'-lacZ' fusion. Furthermore, by introducing a qscR-lacZ transcriptional fusion vector to strains M-18, M-18Q, and M-18G, a gacA inactivation mutant in strain M-18, respectively, it was found that beta-galactosidase activity in both strain M-18G and strain M-18Q was decreased to half that in the wild type. This suggested that QscR might be involved in autoinducing its own gene expression and act as an intermediate in GacA-dependent gene regulation as well. The result was further demonstrated by the overexpression of the gacA gene in strain M-18Q.
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PMID:QscR acts as an intermediate in gacA-dependent regulation of PCA biosynthesis in Pseudomonas sp. M-18. 1817 22