bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reiterated DNA sequences defining genomic diversity within the species Mycoplasma hyorhinis
Authors: Taylor M. A. , Ferrell R. V. , Wise K. S. , McIntosh M. A. 
Published: October 2006

SummaryGenomic restriction fragments isolated from Mycoplasma hyorhinis and Mycoplasma hyopneumoniae were shown by DNA hybridization and nucleotide sequence analyses to contain sequences common to these two species, as well as another porcine‐derived mycoplasma, Mycoplasma flocculare. Intraspecies hybridization experiments using these fragments as probes indicated that the sequence is highly redundant in several strains of M. hyorhinis, but that there is diversity in the sizes of restriction fragments detected among these strains. In contrast, repetition of the sequence was limited in M. hyopneumoniae and M. flocculare, and no homologies to this repeated element were apparent in mycoplasma species isolated from animal hosts other than the swine. The reiterated sequence may reflect intraspecies genomic diversification in M. hyorhinis and its selective presence in otherwise unrelated species raises the possibility that it has been horizontally transmitted between these organisms.
Mutations of putP that alter the lithium sensitivity of Salmonella typhimurium
Authors: Myers R. S. , Maloy S. R. 
Published: October 2006

SummaryThe putP gene encodes the major proline permease in Salmonella typhimurium that couples transport of proline to the sodium electrochemical gradient. To identify residues involved in the cation binding site, we have isolated putP mutants that confer resistance to lithium during growth on proline. Wild‐type S. typhimurium can grow well on proline as the sole carbon source in media supplemented with NaCl, but grows poorly when LiCl is substituted for NaCl. In contrast to the growth phenotype, proline permease is capable of transporting proline via Na+/proline or Li+/proline symport. Therefore, we selected mutants that grow well on media containing proline as the sole carbon source in the presence of lithium ions. All of the mutants assayed exhibit decreased rates of Li+pro‐line and Na+/proline cotransport relative to wild type. The location of each mutation was determined by deletion mapping: the mutations cluster in two small deletion intervals at the 5′ and 3′ termini of the putP gene. The map positions of these lithium resistance mutations are different from the locations of the previously isolated substrate specificity mutations. These results suggest that Lir mutations may define domains of the protein that fold to form the cation binding site of proline permease.
Molecular cloning of a Salmonella typhi LT‐like enterotoxin gene
Authors: Fernández M. , Sierra‐Madero J. , de la Vega H. , Vázquez M. , López‐Vidal Y. , Ruíz‐Palacios G. M. , Calva E. 
Published: October 2006

SummaryDiarrhoea is a common event during typhoid fever; nevertheless, the possible participation of a diarrhoea‐inducing enterotoxin has not been described (Roy et al., 1985). Recombinant bacteriophage λ FDC1 was isolated from a genomic library of Salmonella typhi, the causal agent of typhoid fever, by screening with a probe for the B subunit gene of the heat‐labile, cholera‐like, Escherichia coli enterotoxin (LT). λ FDC1 codes for an enterotoxin that causes secretion in rat ileal loops, that elongates Chinese hamster ovary (CHO) cells, that is recognized by antibodies against LT, and does not bind in vitroto ganglioside GM1. These results should allow further studies towards elucidating a possible role for the S. typhi enterotoxin in the pathogenesis of typhoid fever.
Sequences required for regulation of arginine biosynthesis promoters are conserved between Bacillus subtilis and Escherichia coli
Authors: Smith M. C. M. , Czaplewski L. , North A. K. , Baumberg S. , Stockley P. G. 
Published: October 2006

SummaryThe region required for regulation of a previously characterized arginine‐regulatable promoter upstream from the argC gene in the argCAEBD‐cpa‐argF cluster of Bacillus subtilis was defined by integration of argC‐lacZ translational fusions into the chromosome at a site distant from the arginine loci. Some sequence similarity was detected between the argC regulatory region and the well‐characterized Escherichia coli arginine operators (ARG boxes). This similarity was shown to be functional in vivo in that the B. subtilis repressor regulated the E. coli arginine genes, but the E. coli repressor, even when encoded by a multicopy plasmid, could not repress the B. subtilis argC promoter. In vitro binding studies using purified repressors on DNA fragments encoding operators from both E. coli and B. subtilis demonstrated interactions by both proteins.
Molecular characterization of a gene from Saccharopolyspora erythraea (Streptomyces erythraeus) which is involved in erythromycin biosynthesis
Authors: Dhillon N. , Hale R. S. , Cortes J. , Leadlay P. F. 
Published: October 2006

SummaryA 7.3 kbp DNA fragment, encompassing the erythromycin (Em) resistance gene (ermE) and a portion of the gene cluster encoding the biosynthetic genes for erythromycin biosynthesis in Saccharopolyspora erythraea (formerly Streptomyces erythraeus) has been cloned in Streptomyces lividans using the plasmid vector pIJ702, and its nucleotide sequence has been determined using a modified dideoxy chain‐termination procedure. In particular, we have examined the region immediately 5′ of the resistance determinant, where the tandem promoters for ermE overlap the promoters for a divergently transcribed coding sequence (ORF). Disruption of this ORF using an integrational pIJ702‐based plasmid vector gave mutants which were specifically blocked in erythromycin biosynthesis, and which accumulated 3‐O‐α‐L‐mycarosylerythronolide B: this behaviour is identical to that of previously described eryC1 mutants. The eryC1‐gene product, a protein of subunit Mr 39200, is therefore involved either as a structural or as a regulatory gene in the formation of the deoxyamino‐sugar desosamine or in its attachment to the macro‐lide ring.
Transcriptionai induction of Streptomyces cacaoiβ‐lactamase by a β‐lactam compound
Authors: Forsman M. , Lindgren L. , Haggström B. , Jaurin B. 
Published: October 2006

SummaryThe soil bacterium Streptomyces cacaoi produces an extracellular β‐lactamase. The β‐lactamase expression could be induced by the β‐lactam compound 6‐amino penicillinoic acid (6‐APA). In liquid cultures, a 50‐fold increase in β‐lactamase expression was observed within the first three hours after addition of 6‐APA. Using the cloned β‐lactamase gene as a probe, it was shown that this increase was mediated at the level of transcriptional initiation. The start point of the induced β‐lactamase transcript was determined, and the nucleotide sequence of the promoter region was analysed. No noticeable homology was found to control regions of inducible β‐lactamase genes of other bacteria. A striking feature was the presence of six direct repeats (ten base pairs each) upstream of the promoter region. Thus, an example of an inducible regulatory gene system in this Gram‐positive microorganism is presented. Also, the primary structure of the β‐lactamase was deduced, showing a high degree of homology with class A β‐lactamases.
Isolation of Erwinia chrysanthemi mutants altered in pectinolytic enzyme production
Authors: Hugouvieux‐Cotte‐Pattat N. , Robert‐Baudouy J. 
Published: October 2006

SummaryVarious mutations in the pectin catabolic pathway of Erwinia chrysanthemi were isolated by selection of Mu‐lac insertions, resulting in expression of the lac genes inducible by pectin degradation products. This approach allowed us to isolate lacZ fusions with the genes pelC, pelD, ogl and pem, encoding pectate lyases PLc and PLd, oligogalacturonate lyase and pectin methytesterase, respectively. Moreover, we obtained mutations affecting the regulation of pectinolytic enzymes; a locus called peel appeared to be involved in induction of pectate tyases and pectin methylesterase. A second locus, called pect, may encode an activator protein acting on pectate lyase production. Both peel and pecL expression are induced in the presence of pectic polymers. The expression of the pem gene was studied in more detail by analysis of the pem‐lacZ fusions. The expression of pem appears to be controlled by the negative regulatory gene kdgR, which controls alt the genes involved in pectin degradation (pem, pel, ogl, kduD, kduf, kdgK, kdgA). This study confirmed that 2‐keto‐3‐deoxy‐gluconate is a key intermediate for the induction of the pectin catabolic pathway. The three genes pem, pelD and pecl were localized in the same region, near the ade‐377 marker on the genetic map of the E. chrysanthemi strain 3937. The pem gene was located more precisely on an 18kb DNA fragment containing the pelADE cluster. However, this 18 kb DNA fragment did not complement the pecl mutation. The pecL mutations were located near the ile‐2 marker on the genetic map of E. chrysanthemi strain 3937.
Mitochondrial cytochrome b genes with a six‐nucleotide deletion or single‐nucleotide substitutions confer resistance to antimycin A in the yeast Kluyveromyces lactis
Authors: Coria R. , Garcfa M. , Brunner A. 
Published: October 2006

SummaryExtrachromosomal mutants resistant to antimycin, from the yeast Kluyveromyces lactis, have been isolated, genetically characterized, and assigned to two specific genetic loci (Brunner et al., 1987). In the present work the cytochrome b nucleotide sequence from six of these mutants was determined. Five mutants had single point mutations, corresponding to transverslons. In one mutant, a six‐base‐pair deletion, beginning at nucleotide 689, was observed. The amino acid sequence derived from the coding strand showed that, in three independent antimycin‐resistant mutants, a change of asparagine 31 into lysine took place (two of these mutants are also resistant to diuron). Two other mutants showed a change from lysine 228 into isoleucine (or methionine). Leucine 230, isoleucine 231, and threonine 232, were lost in the deletion mutant and were replaced by serine.
pH‐regulated gene expression in Salmonella: genetic analysis of aniG and cloning of the earA regulator
Authors: Foster J. W. , Aliabadi Z. 
Published: October 2006

SummaryThe recently described aniG locus exhibits a series of unique regulatory features. The gene is exogenously coinduced by acid and D‐mannose, its expression is maximal under anaerobiosis, and the system is regulated in an unusual manner by cyclic AMP. The external acid regulatory locus, earA, is a repressor protein that mediates the acid and mannose control of aniG. The earA locus was cloned and found to code for a 33 K protein associated with membrane‐ and soluble fractions. A second locus, earB, was located immediately upstream from earA. The earB locus or its product interferes with the repression of aniG by EarA. Mutations in crp and cya were found to prevent transcription of aniG but only in an earA+ background. Analysis of an earA‐cat fusion established that crp does not affect earA expression.While the physiological role of aniG/earA is unclear, this system serves as a model for external pH‐regulated gene expression. The present data indicate that it is used to sense the presence of mannose in an acidic extracellular environment. This is particularly intriguing in that the system is not involved in the utilization of mannose as a carbon source.
Stability of ColE1‐like and pBR322‐like plasmids in Escherichia coli
Authors: Ayala‐Sanmartin J. , Gómez‐Eichelmann M. C. 
Published: October 2006

SummaryThe average copy number, the level of ampicillin resistance conferred by one plasmid, and the degree of plasmid multimerization were determined for several ColE1‐like and pBR322‐like plasmids. From the results obtained, the variance of the units of partition corresponding to each plasmid studied was calculated. Experimentally determined plasmid stability was compared with that calculated using the variance of the units of partition and the ratio between the generation times of plasmid‐free and of plasmid‐carrying cells, assuming that the units of partition are distributed randomly between daughter cells.Stability of the pBR322‐like plasmids present mainly as monomers in the bacterial host was consistent with random partitioning, whereas pBR322‐like plasmids, present mainly as dimers, and the ColE1‐like plasmid showed greater stability than that predicted with random partitioning at cell division.
Mutations in genes downstream of the rpoN gene (encoding σ54) of Klebsiella pneumoniae affect expression from σ54‐dependent promoters
Authors: Merrick M. J. , Coppard J. R. 
Published: October 2006

SummaryTwo open reading frames (ORFs), designated ORF95 and ORF162, downstream of the Klebsiella pneumoniaeσ54 structural gene (rpoN) have been sequenced and shown to encode polypeptides of 12kD and 16kD, respectively. ORFs homologous to ORF95 are present downstream of four out of five rpoN genes sequenced to date from a range of Gram‐negative bacteria, and ORF162 is also conserved, at least in Pseudomonas putida. Chromosomal mutations have been created in each gene using a kan cassette and both have the same phenotype, i.e. they cause an increase in the level of expression from σ54‐dependent promoters. We propose that the products of both genes function to modulate the activity of Eσ54, although a physiological role for these proteins has not yet been identified.
Analysis of the yopA gene encoding the Yop1 virulence determinants of Yersinia spp.
Authors: Skurnik M. , Wolf‐Watz H. 
Published: October 2006

SummaryThe Yop proteins of Yersinia are important virulence determinants. The Yop1 protein sequences of Yersinia pestis, Yersinia pseudotuberculosis, and two Yersinia enterocolitica serotypes, O:3 and O:8, deduced from the nucleotide sequences of the corresponding yopA genes, were compared. Most differences were found in the hydrophilic domains of the proteins, whereas the hydrophobic domains were conserved. The amino acid sequences revealed a signal sequence 25 amino acids long. No cysteine residues were present, even though Yop1 forms a polymeric structure.The transcription startpoint of yop4 was determined by primer extension. The coding region and transcription startpoint were separated by a leader sequence 270 nucleotides long. The yopA promoter sequence of Y. pestis is identical to the corresponding sequence of Y. pseudotuberculosis and transcription studies revealed that this promoter is active in Y. pestis. Thus, the inability of Y. pestis to express the Yop1 protein is due to a single base pair deletion In the coding region of the yopA gene of Y. pestis (Rosqvist et al., 1988).
Sense and antisense transcripts of traM, a conjugal transfer gene of the antibiotic resistance plasmid R100
Authors: Dempsey W. B. 
Published: October 2006

SummaryThe region of the antibiotic resistance plasmid R100 that encodes the plasmid‐specific transfer gene traM has two tandemly aligned promoters separated by 145 nucleotides. The principal transcripts are 705 and 562 nucleotides long. Minor transcripts are 1550 and 1700 nucleotides long. The 705‐base transcript appears to encode an 11 kD traM protein. The 562‐base transcript does not encode a detectable protein. When sub‐cloned on short fragments, the promoter for the 562‐base transcript initiates efficiently but that for the 705 site does not. The 3′ ends of the 705 and 562 base transcripts end inside the traJ ORF. Thus they provide additional sense RNA to compete with traJ for finP, the antisense translational regulator of traJ. A model is proposed for the participation of these sense and antisense transcripts in the control of expression of the traJ gene.
Expression of gonococcal protein II in Escherichia coli by translational fusion
Authors: Palmer L. , Brooks G. F. , Falkow S. 
Published: October 2006

SummaryAprotein II (P.II) gene from Neisseria gonorrhoeae was cloned in Escherichia coli and characterized by DNA sequence analysis. As with other reported P.II sequences, this gene contains an ATG initiation codon which is out of frame with respect to the remainder of the P.II amino acid sequence. A translational fusion was constructed in E. coli which linked the P.II sequence to the signal peptide of β‐lactamase. This P.II fusion differs from the gonococcal protein only in the first seven residues at the N terminus. In E. coli, the P.II fusion product exhibits properties analogous to those of P.II in N. gonorrhoeae. The P.II fusion product is a major component of the E. coli outer membrane and it is exposed on the cell surface. The P.II fusion protein also exhibits the heat‐modifiable phenotype of gonococcal P.II.
Transcription of the sulA‐ompA region of Escherichia Coli during the SOS response and the role of an antisense RNA molecule
Authors: Cole S. T. , Honoré N. 
Published: October 2006

SummaryThe transcriptional pattern of the 22 min region of the Escherichia coli chromosome containing the linked sulA and ompA genes, which encode an SOS‐inducible inhibitor of cell division and a constitutively expressed, major outer membrane protein, respectively, has been re‐examined. During normal growth, the sulA gene was repressed whereas the ompA gene produced a stable 1250 nucleotide transcript. Counter‐transcription of sulA occurred from a promoter situated in the sulA‐ompA intergenic region and the product of this transcriptional circuit, named isf, is a 353 nucleotide untranslated RNA. Since the isf RNA is complementary to the 3‐end of the sulA transcript, it could modulate sulA function by serving as an anti‐messenger.On induction of the SOS‐response, massive transcription of sulA took place, resulting in the ‘silencing’ of the isf gene, production of an abundant ∼615 nucleotide sulA mRNA and a novel hybrid transcript of ∼2100 nucleotides encoding both the SulA and OmpA proteins. Production of the latter RNA species, caused by transcription reading through the sulA terminator, the intergenic region and the coding sequences, was accompanied by a decrease in the abundance of the ompA mRNA as a result of promoter occlusion. However, the amount of OmpA protein produced was only slightly reduced.
Transcriptional regulation of F plasmid gene srnB: rifampicin‐promoted in vitro readthrough of a terminator in the leader region
Authors: Akimoto S. , Sakikawa T. , Ono K. , Ono T. , Ohnishi Y. 
Published: October 2006

SummarysrnB is an F‐plasmid encoded gene, otherwise silent, whose expression is induced by added rifampicin, leading to the release of cellular Mg2+ and degradation of stable RNA. In the absence of rifampicin, transcripts from the srnB gene were relatively short. S1 nuclease mapping revealed that the short mRNA species terminated within the leader, at the 3’end of a potential stem‐and‐loop structure. A deletion in the stem‐loop resulted in constitutive synthesis of the mRNA that extended beyond the termination site into the structural gene. Even with the wild‐type gene, transcription continued beyond the terminator sequence in the presence of added rifampicin. Most of the transcripts synthesized in the presence of rifampicin were long enough to encode the srnB protein. We hypothesize from these results that RNA polymerase associated with rifampicin can read through the terminator to induce srnB expression.
Characterization of Rhizobium phaseoli Sym plasmid regions involved in nodule morphogenesis and host‐range specificity
Authors: Cevallos M. A. , Vázquez M. , Dávalos A. , Espín G. , Sepúlveda J. , Quinto C. 
Published: October 2006

SummaryTwo nodulation regions from the symbiotic plasmid (pSym) of Rhizobium phaseoil CE‐3 were identified. The two regions were contained in overlapping cosmids pSM927 and pSM991. These cosmids, in a R phaseoli pSym‐cured strain background, induced ineffective nodules on Phaseolus vulgaris roots.Transconjugants of Rhizobium meliloti harbouring pSM991 induced nodule‐like structures on bean roots, suggesting that this cosmid contains host‐range determinants.Analysis of deletions and insertional mutations in the sequences of pSM991 indicated that the genes responsible for the induction and development of nodules in P. vulgaris are organized in two regions 20kb apart. One region, located in a 6.8kb Eco RI fragment, includes the common nodABC genes. The other region, located in a 3.5kb EcoRI fragment, contains information required for host‐range determination.
An overlap between osmotic and anaerobic stress responses: a potential role for DNA supercoiling in the coordinate regulation of gene expression
Authors: Bhriain N. Ni , Dorman C. J. , Higgins C. F. 
Published: October 2006

SummaryThe regulation of several genes in response to osmotic and anaerobic stress has been examined. We have demonstrated a clear overlap between these two regulatory signals. Thus, the osmotically induced proU and ompC genes require anaerobic growth for optimum induction while the anaerobically induced tppB gene is also regulated by osmolarity. Furthermore, normal expression of tppB and ompC requires the positive regulatory protein OmpR, yet this requirement can be partially, or even fully, overcome by altering the growth conditions. Finally, the pleiotropic, anaerobic regulatory locus, oxrC, is also shown to affect expression of the osmoticalty regulated proU gene. The oxrC mutation is shown to affect the level of negative supercoiling of plasmid DNA and its effects on gene expression can be explained as secondary consequences of altered DNA topology. We suggest that there is a class of ‘stress‐regulated’ genes that are regulated by a common mechanism in response to different environmental signals. Furthermore, our data are consistent with the notion that this regulatory overlap is mediated by changes in DNA supercoiling in response to these environmental stresses.
A novel, non‐invasive promoter probe vector: cloning of the osmoregulated proU promoter of Escherichia coli K12
Authors: Park S. F. , Stirling D. A. , Hulton C. S. J. , Booth I. R. , Higgins C. F. , Stewart G. S. A. B. 
Published: October 2006

SummaryWe have constructed a novel promoter probe plasmid pSB40, containing a unique lac‐α‐tetracycline marker gene tandem, which allows for both positive and negative selection of active promoters. Promoters cloned in pSB40 can be readily mobilized as EcoR1 cassettes. Using this vector we have performed a non‐invasive analysis of the E. coli chromosome for promoters regulated by osmotic upshift. Only one such promoter, subsequently identified as part of the proU operon, was isolated. A sequence of 253bp, sufficient to mediate osmotic regulation of the proU promoter, was defined. This E coli promoter was normally regulated in Salmonella typhimurium, Klebsiella and Citrobacter but not in Shigella. A proU‐luxAB fusion plasmid was constructed and used to monitor in vivo real‐time kinetics of proU induction following osmotic upshock.
Differential gene expression during sporulation in Bacillus subtilis: regulation of the spoVJ gene
Authors: Errington J. , Wootten L. , Dunkerley J.C. , Foulger D. 
Published: October 2006

SummaryThe process of spore formation in the Gram‐positive bacterium Bacillus subtilis is a simple developmental system controlled by 50 or more genes. The complex pattern of regulatory interactions between these genes is beginning to be elucidated. spoVJ is a poorly characterized locus in which mutations affect spore development at a relatively late stage (Stage V). We have now cloned and physically characterized the SpoVJ locus, and analysed its expression by lacZ fusion. Expression of spoVJ is temporally delayed until about two hours after the initiation of sporulation. Its expression is also spatially restricted to the mother cell compartment; as such, it represents the earliest known mother‐cell‐specific event. Control of spoVJ transcription is complex: expression is dependent upon the products of all of the spo0 genes and on some of the spoII genes butitis independent of all later genes except spoIIID. As spoIIID mutations do not affect prespore development, this gene must be an important early determinant of mother‐cell‐specific gene expression.