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The phaC, phaP, phaR, and phaZ genes are involved in the synthesis, accumulation, and degradation of poly-β-hydroxybutyrate (PHB). These genes encode the PHB synthase, phasin, regulatory protein, and PHB depolymerase, respectively, and are located in the same locus in the genome of Rhodobacter sphaeroides FJ1, a purple nonsulfur bacterium capable of producing PHB. We have previously found that the PhaR protein binds to the promoter regions of phaP, phaR, and phaZ and represses their expression. In this study, we determined that PhaR binds to an 11-bp palindromic sequence, 5′- N3 -3′, located at nucleotides −69 to −59 and −97 to −87 relative to the translation start site of phaP. Substitution of the three spacer nucleotides with any three or four nucleotides in this sequence had no effect on PhaR binding, but all other base deletions or substitutions in this sequence abolished its ability to bind PhaR both in vitro and in vivo. These results suggest that PhaR regulates the expression of phaP in R. sphaeroides FJ1. [ABSTRACT FROM AUTHOR]

A cluster of genes encoding polyhydroxybutyrate (PHB) depolymerase ( phaZ), PHB synthase ( phaC), phasin ( phaP), and the regulator protein ( phaR) was previously identified in Rhodobacter sphaeroides FJ1 ( R. sphaeroides FJ1). In this study, we investigated the role of the PhaR protein on the expression of the pha genes. Immunoblot analysis revealed that the expressions of phaP, phaZ and phaR genes in wild-type cells of R. sphaeroides FJ1 are repressed during the active growth phase, with the exception of phaC. A phaR deletion mutant of R. sphaeroides FJ1 was constructed, and the basal level of phaP and phaZ expression in this mutant was markedly increased. Electrophoretic mobility shift assays demonstrated that PhaR binds to the promoter region of phaP as well as those of phaR and phaZ. These results suggest that the PhaR protein is a repressor of phaP, phaR, and phaZ genes in R. sphaeroides FJ1. [ABSTRACT FROM AUTHOR]

Abstract   Xanthomonas axonopodis pv. citri (X. axonopodis pv. citri) possesses two lexA genes, designated lexA1 and lexA2. Electrophoretic mobility shift data show that LexA1 binds to both lexA1 and lexA2 promoters, but LexA2 does not bind to the lexA1 promoter, suggesting that LexA1 and LexA2 play different roles in regulating the expression of SOS genes. In this study, we have determined that LexA2 binds to a 14-bp dyad–spacer–dyad palindromic sequence, 5′-TGTACAAATGTACA-3′, located at nucleotides −41 to −28 relative to the translation start site of lexA2 of X. axonopodis pv. citri. The two spacer nucleotides in this sequence can be changed from AA to TT without affecting LexA2 binding; all other base deletions or substitutions abolish LexA2 binding. The LexA1 binding sequence in the promoter region of lexA2 is TTAGTACTAAAGTTATAA and is located at −133 to −116, and that in the lexA1 gene is AGTAGTAATACTACT located at nucleotides −19 to −5 relative to the translation start site of lexA1. Any base change in the latter sequence abolishes LexA1 binding. [ABSTRACT FROM AUTHOR]

Thermophilic actinomycetes strains were isolated from various environment in Taiwan and screened for degradation of poly(ethylene succinate) (PES), poly(e-caprolactone) (PCL) and/or poly(β-hydroxybutyrate) (PHB) by the clear-zone method. Out of 341 strains of thermophilic actinomycetes, 105 isolates were PHB-degraders (30.8%), 198 isolates were PCL-decomposers (58.1%), and 99 isolates could degrade PES (29.0%). Furthermore, 77 isolates could degrade both PHB and PCL (22.6%), 35 isolates could degrade both PHB and PES (10.3%), 81 isolates could degrade both PES and PCL (23.8%) and 31 isolates could degrade the three polyesters used in this study (9.1%). Base on the morphological and chemical characteristics, these 31 isolates belonging to Actinomadura (12.9%), Microbispora (25.8%), Streptomyces (48.4%), Thermoactinomyces (9.7%) and Saccharomonospora genus (3.22%). [ABSTRACT FROM AUTHOR]

Abstract??TwouvrA-like genes, designateduvrA1anduvrA2, that may be involved in nucleotide excision repair inXanthomonas axonopodispv. citri (X. a. pv. citri) strain XW47 were characterized. TheuvrA1 gene was found to be 2,964?bp in length capable of encoding a protein of 987 amino acids. TheuvrA2 gene was determined to be 2,529?bp with a coding potential of 842 amino acids. These two proteins share 71 and 39% identity, respectively, in amino acid sequence with the UvrA protein ofEscherichia coli. Analyses of the deduced amino acid sequence revealed that UvrA1 and UvrA2 have structures characteristic of UvrA proteins, including the Walker A and Walker B motifs, zinc finger DNA binding domains, and helix-turn-helix motif with a polyglycine hinge region. TheuvrA1 oruvrA2 mutant, constructed by gene replacement, was more sensitive to DNA-damaging agents methylmethane sulfonate (MMS), mitomycin C (MMC), or ultraviolet (UV) than the wild type. TheuvrA1 mutant was four orders of magnitude more sensitive to UV irradiation and two orders of magnitude more sensitive to MMS than theuvrA2mutant. TheuvrA1uvrA2 double mutant was one order of magnitude more sensitive to MMS, MMC, or UV than theuvrA1 single mutant. These results suggest that UvrA1 plays a more important role than UvrA2 in DNA repair inX. a.pv. citri. BothuvrA1 anduvrA2 genes were found to be constitutively expressed in the wild type andlexA1 orlexA2 mutant ofX. a. pv. citri, and treatment of these cells with sublethal dose of MMC did not alter the expression of these two genes. Results of electrophoresis mobility shift assays revealed that LexA1 or LexA2 does not bind to either theuvrA1 or theuvrA2 promoter. These results suggest thatuvrAexpression inX. a. pv. citri is not regulated by the SOS response system. [ABSTRACT FROM AUTHOR]

We previously identified and characterized a lexA gene from Xanthomonas axonopodis pv. citri. For this study, we cloned and expressed a lexA homologue from X. axonopodis pv. citri. This gene was designated lexA2, and the previously identified lex1 gene was renamed lexA1. The coding region of lexA2 is 606 bp long and shares 59% nucleotide sequence identity with lexA1. Analyses of the deduced amino acid sequence revealed that LexA2 has structures that are characteristic of LexA proteins, including a helix-turn-helix DNA binding domain and conserved amino acid residues required for the autocleavage of LexA. The lexA2 mutant, which was constructed by gene replacement, was 4 orders of magnitude more resistant to the DNA-damaging agent mitomycin C at 0.1 μg/ml and 1 order of magnitude more resistant to another DNA-damaging agent, methylmethane sulfonate at 30 pg/ml, than the wild type. A lexA1 lexA2 double mutant had the same degree of susceptibility to mitomycin C as the lexA1 or lexA2 single mutant but was 1 order of magnitude more resistant to methylmethane sulfonate at 30 μg/ml than the lexA1 or lexA2 single mutant. These results suggest that LexA1 and LexA2 play different roles in regulating the production of methyltransferases that are required for repairing DNA damage caused by methylmethane sulfonate. A mitomycin C treatment also caused LexA2 to undergo autocleavage, as seen with LexA1. The results of electrophoresis mobility shift assays revealed that LexA2 does not bind the lex A1 promoter. It binds to both the lexA2 and aecA promoters. However, neither LexA2 nor LexAl appears to regulate recA expression, as lexA1, lexA2, and lexA1 lexA2 mutants did not become constitutive for recA transcription and RecA production. These results suggest that recA expression in X. axonopodis pv. citri is regulated by mechanisms that have yet to be identified. [ABSTRACT FROM AUTHOR]

Examines the A protein of the filamentous bacteriophage Cf of Xanthomonas campestris pv. citri. Expression of the gene encoding the A protein of Cf; Introduction of the genomic DNA of a filamentous bacteriophage by electroporation; Abolition of the infectivity of Cf by inactivation of the A protein gene.