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M J Bailey

Publications and source records attributed to M J Bailey.

At least 55 records · Page 3Linked to original sources
PubMed1998

The use of solid physical models for the study of macromolecular assembly.

The use of modern technology in the construction of accurate solid macromolecular models based on atomic coordinates and electron density functions has led us to re-examine the usefulness of physical models as tools for understanding molecular assembly and for designing detailed experimental and computational studies of the assembly process. Recent developments include the construction of new models, which have provided insights into the assembly of viruses and light harvesting complexes.

Biomedical Engineering↗
PubMed1997

Description of a novel plasmid replicative origin from a genetically distinct family of conjugative plasmids associated with phytosphere microflora.

A novel replicative origin (oriV) from a conjugative, mercury resistance plasmid (pQBR11, 304 kbp) has been cloned and sequenced. Homology to the pQBR11 oriV-containing 3.55 kbp BamHI fragment (pCV1200) was restricted to one of five genetically distinct classes (group I) of narrow host range, mega-plasmids that persist as a genetic component of the pseudomonad community indigenous to the microflora of sugar beet. The oriV of pQBR11 was located within a unique sequence of 300 bp which initiated the replication of pUC derived suicide vectors in Pseudomonas putida UWC1. The limited size of the DNA sequence required to initiate replication, and the presence of two 15/16 bp directly repeated motifs, indicate that this group of mega-plasmids contain a single origin of replication, which initiates replication via a host-polymerase dependent rolling circle mechanism.

Base Sequence↗
PubMed1997

Manipulation of baculovirus vectors.

Baculovirus expression vectors provide an excellent system for the synthesis of recombinant proteins in insect cells. This article presents sufficient background information to allow the nonspecialist to understand the basic principles of the technology and the development of baculovirus expression vectors. A summary of the most commonly used plasmids and viruses is presented. Detailed techniques are described to enable recombinant baculoviruses to be constructed. These methods include the protocols required for propagating insect cells in culture and their subsequent infection with viruses.

Animals↗
PubMed1997

RfaH and the ops element, components of a novel system controlling bacterial transcription elongation.

The RfaH protein controls the transcription of a specialized group of Escherichia coli and Salmonella operons that direct the synthesis, assembly and export of the lipopolysaccharide core, exopolysaccharide, F conjugation pilus and haemolysin toxin. RfaH is a specific regulator of transcript elongation; its loss increases transcription polarity in these operons without affecting initiation from the operon promoters. The operons of the RfaH-dependent regulon contain a short conserved 5' sequence, the ops element, deletion of which increases operon polarity to an extent similar to that caused by loss of RfaH. The ops element is also present upstream of polysaccharide gene clusters of Shigella flexneri, Yersinia enterocolitica, Vibrio cholerae and Klebsiella pneumoniae and the RP4 fertility operon of Pseudomonas aeruginosa, suggesting that this is a widely spread control system. The mechanistic coupling of RfaH and the ops element has been demonstrated in vitro and in vivo, and we suggest that the ops element recruits RfaH and potentially other factors to the RNA polymerase complex, modifying the complex to increase its processivity and allowing transcription to proceed over long distances.

Bacterial Proteins↗
PubMed1997

The acquisition of indigenous plasmids by a genetically marked pseudomonad population colonizing the sugar beet phytosphere is related to local environmental conditions.

The transfer of naturally occurring conjugative plasmids from the indigenous microflora to a genetically modified population of bacteria colonizing the phytospheres of plants has been observed. The marked strain (Pseudomonas fluorescens SBW25EeZY6KX) was introduced as a seed dressing to sugar beets (Beta vulgaris var. Amethyst) as part of a field experiment to assess the ecology and genetic stability of deliberately released bacterial inocula. The sustained populations of the introduced strain, which colonized the phytosphere, were assessed throughout the growing season for the acquisition of plasmids conferring mercury resistance (Hg(supr)). Transconjugants were isolated only from root and leaf samples collected within a narrow temporal window coincident with the midseason maturation of the crop. Conjugal-transfer events were recorded during this defined period in two separate field release experiments conducted over consecutive years. On one occasion seven of nine individual plants sampled supported transconjugant P. fluorescens SBW25EeZY6KX, demonstrating that conjugative gene transfer between bacterial populations in the phytosphere may be a common event under specific environmental conditions. The plasmids acquired in situ by the colonizing inocula were identified as natural variants of restriction digest pattern group I, III, or IV plasmids from five genetically distinct groups of large, conjugative mercury resistance plasmids known to persist in the phytospheres of sugar beets at the field site. These data demonstrate not only that gene transfer may be a common event but also that the genetic and phenotypic stability of inocula released into the natural environment cannot be predicted.

Journal Article↗
PubMed1997

Impact of Plasmid pQBR103 Acquisition and Carriage on the Phytosphere Fitness of Pseudomonas fluorescens SBW25: Burden and Benefit.

The phytosphere population densities of Pseudomonas fluorescens SBW25EeZY6KX (lacZX aph xylE) carrying pQBR103 (Hg(supr) Tra(sup+), 330 kbp) declined significantly relative to plasmid-free populations after seed inoculation. As the sugar beet plants matured, ca. 100 days after planting, simultaneous selections for plasmid-carrying hosts were observed in the phyllospheres and rhizospheres of field-grown plants. The recovery of these populations to densities indistinguishable from the densities of plasmid-free inocula (4 x 10(sup5) CFU/g in the rhizosphere) demonstrates that phytosphere-associated plasmids confer a specific fitness advantage to host bacteria.

Journal Article↗
PubMed1997

Developments in the use of lasers for the treatment of benign prostatic hypertrophy.

Benign prostatic hyperplasia (BPH) is an almost inevitable part of the aging process in men. Symptoms of BPH include slowing and interruption of the urinary stream, incomplete bladder emptying, hesitancy, post-micturition dribbling, frequency and nocturia. These symptoms may not cause an individual any inconvenience, but can lead to considerable interference to quality of life. In more severe cases, and especially if complications such as urinary retention occur, surgical relief of the obstruction is indicated. Traditionally, this has been by trans-urethral resection of the prostate (TURP). However, in the past decade, attempts to find alternative treatments to TURP have been stimulated by the desire to avoid the morbidity of TURP. The use of laser energy in this context has been evolving rapidly, and is the subject of this review.

Journal Article↗
PubMed1996

Physical and genetic map of the Pseudomonas fluorescens SBW25 chromosome.

Pseudomonas fluorescens is a saprophytic bacterium commonly isolated from soil, water, and the surfaces and tissues of plants and animals. The species has important applications in biotechnology because it can enhance plant growth and protect crops against disease. A complete physical map of the 6.63 Mbp P. fluorescens SBW25 chromosome was constructed using data obtained from combinations of one- and two-dimensional electrophoresis of completely or partially digested chromosomal DNA with end labelling. In total, 139 restriction sites (15 PacI, 53 SpeI, 71 XbaI) were placed on the physical map and complete maps of the circular chromosome were obtained for both PacI and SpeI; only XbaI fragments linking SpeI fragments were positioned. The average resolution of restriction sites was 48 kbp. A genetic map was derived from the physical map by southern hybridization and 31 genes were positioned including oriC, rDNA operons (rnnA-E), recA, gacA, and pyvD.

Blotting, Southern↗
PubMed1996

Suppression of transcription polarity in the Escherichia coli haemolysin operon by a short upstream element shared by polysaccharide and DNA transfer determinants.

Expression of the Escherichia coli hlyCABD operon encoding synthesis, maturation and export of haemolysin toxin was strongly dependent upon a 35 bp DNA sequence, spanning the element GGCGGTAG, located 2 kbp upstream. When the hly operon was placed under the control of the inducible tac promoter, expression remained dependent upon this element, when transcribed in its native orientation 3' of the promoter. The increase in ptac-directed transcription was strongest for the distal, export genes of the hly operon, and was particularly striking when ptac and the element were placed far upstream. The element did not influence transcript stability, and we suggest that it is a key component of a novel regulatory mechanism may suppresses transcription polarity within operons. The mechanism that be of widespread importance in bacterial gene expression because the 8 bp element is present in many Gram-negative species as an upstream component of operons encoding the production of toxins and the surface assembly of polysaccharides and components required for the conjugal transfer of DNA. We name it the ops element for operon polarity suppressor.

Bacterial Proteins↗
PubMed1996

Increased distal gene transcription by the elongation factor RfaH, a specialized homologue of NusG.

The Escherichia coli RfaH protein is required for the expression of operons directing synthesis and export of the toxin haemolysin, the lipopolysaccharide core, and the F-factor sex pilus. Mutation of rfaH increases transcriptional polarity along all three operons. By demonstrating strong RfaH-dependent suppression of transcription polarity in vitro, we have established RfaH as a novel transcriptional activator, and we reveal that RfaH is a homologue of the essential protein NusG that modulates general transcriptional pausing and termination in prokaryotes. Full transcription of the distal genes from an upstream promoter required RfaH and the 5' cls-acting ops element, both in vivo and in vitro. In vivo the requirement for the ops element was suppressed by overexpressing RfaH, and in vitro the presence of ops lowered the concentration of RfaH required to stimulate transcript elongation. We suggest that RfaH directs transcript elongation in an analogous way to NusG, but does so in a subset of bacterial operons primarily engaged in the production of extracellular components required for virulence and fertility.

Amino Acid Sequence↗
PubMed1995

Site directed chromosomal marking of a fluorescent pseudomonad isolated from the phytosphere of sugar beet; stability and potential for marker gene transfer.

A plasmid-free, non-pathogenic, ribosomal RNA group 1 fluorescent pseudomonad, Pseudomonas fluorescens SBW25, was selected from the microflora of sugar beet (Beta vulgaris) and modified to contain constitutively expressed marker genes. By site directed homologous recombination a KX cassette [kanamycin resistance (kanr) and catechol 2,3 dioxygenase (xylE)] and a ZY cassette [lactose utilization (lacZY, beta-galactosidase, lactose permease)] were introduced at least 1 Mbp apart on the 6.6 Mbp bacterial chromosome. Separate sites were selected to provide sensitive detection methods and allow assessments of marker gene stability of the genetically modified micro-organism (GMM), SBW25EeZY6KX, when it colonized the leaves and roots of sugar beet plants following seed inoculation.

Base Sequence↗
PubMed1995

Requirement for FlhA in flagella assembly and swarm-cell differentiation by Proteus mirabilis.

Swarming by Proteus mirabilis is characterized by cycles of rapid population migration across surfaces, following differentiation of typical rods into long, aseptate swarm cells that overexpress flagella and virulence factors, particularly haemolysin. A non-swarming Tn5phoA mutant was unable to synthesize flagella, to fully elongate or to induce high levels of the toxin. The mutation lay within a 2091 bp gene encoding a homologue of the Escherichia coli FlhA belonging to a family of proteins that are required for assembly of flagella or virulence proteins and that are suggested to act either directly in membrane translocation and/or in regulating synthesis of the export apparatus. In trans expression of multicopy flhA restored cell elongation and migration and generated differentiation-specific hyperexpression of flagellin and toxin genes to levels above those seen in the wild-type strain. Transcription of flhA was strongly induced during differentiation, from its own putative sigma 28 promoter. The results suggest a mechanistic coupling of flagella assembly and swarm-cell differentiation.

Amino Acid Sequence↗
PubMed1994

Plasmids isolated from the sugar beet phyllosphere show little or no homology to molecular probes currently available for plasmid typing.

From a representative sample of bacteria, isolated from mature sugar beet leaves (Beta vulgaris) grown at three separate locations in the UK, 79 (18%) were shown to contain plasmids ranging in size from 10 kb to 200 kb. A sensitive colony blot method was developed to facilitate the screening of both Gram-negative and Gram-positive isolates to determine the distribution of known plasmid incompatibility groups among plasmids isolated from the natural environment using the collection of inc/rep probes derived from basic replicons [rep FIA, FIIA, FIB, HI1, HI2, I1, B/O, L/M, N, P, Q, U, W and X, as described by Couturier et al. (1988) Microbiol Rev 52, 375-395]. After hybridization with each of the radiolabelled replicon probes, 54 of these 79 plasmid-containing natural isolates, which included Erwinia spp., Pseudomonas spp. and Gram-positive bacteria, failed to react. Reactivity was observed with 25 of the 29 Klebsiella and Erwinia isolates investigated. Of the plasmid-containing Enterobacteriaceae examined, 18 reacted with the repFIB probe, six with the repFIIA probe and one isolate, Erwinia salicis SBN169, hybridized to both. Southern hybridization demonstrated that the different isolates which shared homology with the repFIB probe contained a common 1 kb PstI fragment.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1994

Phenotypic and genotypic diversity of fluorescent pseudomonads isolated from field-grown sugar beet.

A sample of 30 fluorescent pseudomonads isolated from the phyllosphere of sugar beet throughout a single growing season and shown to be closely related on the basis of fatty acid methyl ester (FAME) analysis was subjected to detailed phenotypic and genotypic characterization. Phenotypic traits were assessed on the basis of biochemical properties, assimilation of sole carbon sources, FAME analysis, organic pyrolysate content (MS-pyrolysis), and total cellular protein profiles. With the exception of total cellular protein profiles, numerical analysis of the data revealed two main clusters, each of which was divided into several subclusters. Numerical analysis of total cellular protein data failed to differentiate isolates into two main clusters, but nevertheless grouped isolates into six subclusters. On the basis of biochemical and carbon source assimilation profiles, 19 isolates were identified as Pseudomonas fluorescens biovar V, eight isolates as P. fluorescens biovar III and three isolates as P. syringae pathovar syringae. In general, all methods of phenotypic analysis grouped isolates according to time of sampling and leaf type. Genome analysis was undertaken by pulsed-field gel electrophoresis (PFGE) of PacI, SpeI, SwaI and XbaI macrorestriction fragments and revealed the presence of eight distinct genomic (clonal) groups. These groups correlated closely with the clusters generated by numerical analysis of phenotypic data, but there was no correlation between macrorestriction fragment profile and isolate identification; in fact the variation in macrorestriction fragment patterns within P. fluorescens biovars was as great as the variation detected between biovars, and between P. fluorescens and P. syringae. Statistical evaluation of macrorestriction fragment patterns revealed two examples of recent strain divergence: one was due to the presence of a 400 kbp plasmid within one isolate of a collection of nine otherwise genomically identical isolates, and the other was observed between two phenotypically similar isolates sampled 220 d apart. Genetic variation was expressed in terms of nucleotide diversity (pi) and pairwise comparisons yielded values ranging from 0.0029 to 0.1517. The mean intrapopulation genetic variation was high (0.0993), but limited genetic variation was detected among isolates sampled on each occasion. Taken together this suggests a population comprised of a variety of apparently distantly related clones (genomic groups), each adapted to local conditions. Genome sizes were estimated from the sum of SpeI restriction fragments and ranged from 4.2 to 5.5 Mbp. Examination of the distribution of XbaI, SpeI, SwaI and PacI restriction endonuclease sites showed that the distribution of SpeI sites differed significantly from the expected (random) distribution.

Bacterial Proteins↗
PubMed1994

Endoscopic laser ablation of the prostate. A new technique for treating prostate problems.

Bladder outflow obstruction due to benign prostatic enlargement affects up to a third of men over the age of 50. To date, the only reliable form of treatment is surgical, mainly by transurethral resection of the prostate (TURP). An alternative technique, endoscopic laser ablation of the prostate (ELAP) has recently been introduced to overcome some of the drawbacks of TURP. ELAP involves directing laser energy via a specially designed side-firing fibre at the enlarged portion of the prostate. The fibre, passed into the prostate through a cystoscope, carries the energy from the laser to the prostate causing heating of the prostate and subsequent shrinkage of the gland. The operation is performed under general or spinal anaesthetic and is quicker to perform than a TURP. Because the laser causes virtually no bleeding, patients can be treated as day cases or go home the day after surgery. A catheter is left in the bladder and is removed as an out-patient a few days later. The early results of ELAP are comparable to TURP, but complications and length of hospital stay are less.

Humans↗
PubMed1993

Comparison of the fatty acid profiles of Borrelia, Serpulina and Leptospira species.

Fatty acid methyl ester (FAME) derivatives were examined as a means of characterizing Borrelia burgdorferi isolates and distinguishing them from other spirochaetes. Analysis was performed using a gas liquid chromatography column in conjunction with Microbial Identification System (MIS) software. Reproducible FAME profiles were produced which distinguished Borrelia species, Serpulina hyodysenteriae and Leptospira icterohaemorrhagiae. Furthermore, the FAME profiles of four recognized Borrelia species (including two American isolates of Borrelia burgdorferi, B31 and JD1) were distinct from one another and from the BSK II medium in which they were grown. The results confirm previous reports that FAME profiles of bacteria represent a diagnostic phenotypic property and suggest that they may have applications in the chemotaxonomic classification of Borrelia species.

Borrelia↗