Molecular analysis of type 3 fimbrial genes from <Emphasis Type="Italic">Escherichia coli</Emphasis>, <Emphasis Type="Italic">Klebsiella</Emphasis> and <Emphasis Type="Italic">Citrobacter</Emphasis> species

Background  

Catheter-associated urinary tract infection (CAUTI) is the most common nosocomial infection in the United States and is caused by a range of uropathogens. Biofilm formation by uropathogens that cause CAUTI is often mediated by cell surface structures such as fimbriae. In this study, we characterised the genes encoding type 3 fimbriae from CAUTI strains of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter koseri and Citrobacter freundii.     

Remobilization of <Emphasis Type="Italic">Tol2</Emphasis> transposons in <Emphasis Type="Italic">Xenopus tropicalis</Emphasis>

Background  

The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring Tol2 element from Oryzias latipes efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, Xenopus tropicalis. Tol2 transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency.     

Immunoreactivity of the <Emphasis Type="Italic">Mycobacterium avium</Emphasis> subsp. <Emphasis Type="Italic">paratuberculosis</Emphasis> 19-kDa lipoprotein

Background  

The Mycobacterium tuberculosis 19-kDa lipoprotein has been reported to stimulate both T and B cell responses as well as induce a number of Th1 cytokines. In order to evaluate the Mycobacterium avium subsp. paratuberculosis (M. avium subsp. paratuberculosis) 19-kDa lipoprotein as an immunomodulator in cattle with Johne's disease, the gene encoding the 19-kDa protein (MAP0261c) was analyzed.     

Recombinant production of <Emphasis Type="Italic">Streptococcus equisimilis</Emphasis> streptokinase by <Emphasis Type="Italic">Streptomyces lividans</Emphasis>

Background  

Streptokinase (SK) is a potent plasminogen activator with widespread clinical use as a thrombolytic agent. It is naturally secreted by several strains of beta-haemolytic streptococci. The low yields obtained in SK production, lack of developed gene transfer methodology and the pathogenesis of its natural host have been the principal reasons to search for a recombinant source for this important therapeutic protein. We report here the expression and secretion of SK by the Gram-positive bacterium Streptomyces lividans. The structural gene encoding SK was fused to the Streptomyces venezuelae CBS762.70 subtilisin inhibitor (vsi) signal sequence or to the Streptomyces lividans xylanase C (xlnC) signal sequence. The native Vsi protein is translocated via the Sec pathway while the native XlnC protein uses the twin-arginine translocation (Tat) pathway.     

Few amino acid positions in <Emphasis Type="Italic">rpoB</Emphasis> are associated with most of the rifampin resistance in <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>

Background  

Mutations in rpoB, the gene encoding the β subunit of DNA-dependent RNA polymerase, are associated with rifampin resistance in Mycobacterium tuberculosis. Several studies have been conducted where minimum inhibitory concentration (MIC, which is defined as the minimum concentration of the antibiotic in a given culture medium below which bacterial growth is not inhibited) of rifampin has been measured and partial DNA sequences have been determined for rpoB in different isolates of M. tuberculosis. However, no model has been constructed to predict rifampin resistance based on sequence information alone. Such a model might provide the basis for quantifying rifampin resistance status based exclusively on DNA sequence data and thus eliminate the requirements for time consuming culturing and antibiotic testing of clinical isolates.     

A non-sense mutation in the putative anti-mutator gene <Emphasis Type="Italic">ada/alkA</Emphasis> of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> and <Emphasis Type="Italic">M. bovis</Emphasis> isolates suggests convergent evolution

Background  

Previous studies have suggested that variations in DNA repair genes of W-Beijing strains may have led to transient mutator phenotypes which in turn may have contributed to host adaptation of this strain family. Single nucleotide polymorphism (SNP) in the DNA repair gene mutT1 was identified in MDR-prone strains from the Central African Republic. A Mycobacteriumtuberculosis H37Rv mutant inactivated in two DNA repair genes, namely ada/alkA and ogt, was shown to display a hypermutator phenotype. We then looked for polymorphisms in these genes in Central African Republic strains (CAR).     

Common genomic features of <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> subsp. <Emphasis Type="Italic">doylei</Emphasis> strains distinguish them from <Emphasis Type="Italic">C. jejuni</Emphasis> subsp. <Emphasis Type="Italic">jejuni</Emphasis>

Background  

Campylobacter jejuni has been divided into two subspecies: C. jejuni subsp. jejuni (Cjj) and C. jejuni subsp. doylei (Cjd). Nearly all of the C. jejuni strains isolated are Cjj; nevertheless, although Cjd strains are isolated infrequently, they differ from Cjj in two key aspects: they are obtained primarily from human clinical samples and are associated often with bacteremia, in addition to gastroenteritis. In this study, we utilized multilocus sequence typing (MLST) and a DNA microarray-based comparative genomic indexing (CGI) approach to examine the genomic diversity and gene content of Cjd strains.     

Attenuation of fibrosis <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> with <Emphasis Type="Italic">SPARC</Emphasis> siRNA

Introduction  

SPARC is a matricellular protein, which, along with other extracellular matrix components including collagens, is commonly over-expressed in fibrotic diseases. The purpose of this study was to examine whether inhibition of SPARC can regulate collagen expression in vitro and in vivo, and subsequently attenuate fibrotic stimulation by bleomycin in mouse skin and lungs.     

The iron-sulfur cluster assembly genes <Emphasis Type="Italic">iscS</Emphasis> and <Emphasis Type="Italic">iscU</Emphasis> of <Emphasis Type="Italic">Entamoeba histolytica</Emphasis> were acquired by horizontal gene transfer

Background  

Iron-sulfur (FeS) proteins are present in all living organisms and play important roles in electron transport and metalloenzyme catalysis. The maturation of FeS proteins in eukaryotes is an essential function of mitochondria, but little is known about this process in amitochondriate eukaryotes. Here we report on the identification and analysis of two genes encoding critical FeS cluster (Isc) biosynthetic proteins from the amitochondriate human pathogen Entamoeba histolytica.     

<Emphasis Type="Italic">AtMRP6</Emphasis>/<Emphasis Type="Italic">AtABCC6</Emphasis>, an ATP-Binding Cassette transporter gene expressed during early steps of seedling development and up-regulated by cadmium in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Background  

ABC proteins constitute one of the largest families of transporters found in all living organisms. In Arabidopsis thaliana, 120 genes encoding ABC transporters have been identified. Here, the characterization of one member of the MRP subclass, AtMRP6, is described.     

Evolution of <Emphasis Type="Italic">mal</Emphasis> ABC transporter operons in the <Emphasis Type="Italic">Thermococcales</Emphasis> and <Emphasis Type="Italic">Thermotogales</Emphasis>

Background  

The mal genes that encode maltose transporters have undergone extensive lateral transfer among ancestors of the archaea Thermococcus litoralis and Pyrococcus furiosus. Bacterial hyperthermophiles of the order Thermotogales live among these archaea and so may have shared in these transfers. The genome sequence of Thermotoga maritima bears evidence of extensive acquisition of archaeal genes, so its ancestors clearly had the capacity to do so. We examined deep phylogenetic relationships among the mal genes of these hyperthermophiles and their close relatives to look for evidence of shared ancestry.     

Evolutionary history of <Emphasis Type="Italic">Wolbachia</Emphasis> infections in the fire ant <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

Background  

Wolbachia are endosymbiotic bacteria that commonly infect numerous arthropods. Despite their broad taxonomic distribution, the transmission patterns of these bacteria within and among host species are not well understood. We sequenced a portion of the wsp gene from the Wolbachia genome infecting 138 individuals from eleven geographically distributed native populations of the fire ant Solenopsis invicta. We then compared these wsp sequence data to patterns of mitochondrial DNA (mtDNA) variation of both infected and uninfected host individuals to infer the transmission patterns of Wolbachia in S. invicta.     

In vitro selection of resistance in <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Klebsiella</Emphasis> spp. at <Emphasis Type="Italic">in vivo</Emphasis> fluoroquinolone concentrations

Background  

Fluoroquinolones are potent antimicrobial agents used for the treatment of a wide variety of community- and nosocomial- infections. However, resistance to fluoroquinolones in Enterobacteriaceae is increasingly reported. Studies assessing the ability of fluoroquinolones to select for resistance have often used antimicrobial concentrations quite different from those actually acquired at the site of infection. The present study compared the ability to select for resistance of levofloxacin, ciprofloxacin and prulifloxacin at concentrations observed in vivo in twenty strains of Escherichia coli and Klebsiella spp. isolated from patients with respiratory and urinary infections. The frequencies of spontaneous single-step mutations at plasma peak and trough antibiotic concentrations were calculated. Multi-step selection of resistance was evaluated by performing 10 serial cultures on agar plates containing a linear gradient from trough to peak antimicrobial concentrations, followed by 10 subcultures on antibiotic-free agar. E. coli resistant strains selected after multi-step selection were characterized for DNA mutations by sequencing gyrA, gyrB, parC and parE genes.     

An intragenic distribution bias of DNA uptake sequences in <Emphasis Type="Italic">Pasteurellaceae</Emphasis> and <Emphasis Type="Italic">Neisseriae</Emphasis>

   

Most sequenced strains from Pasteurellaceae and Neisseriae contain hundreds to thousands of uptake sequence (US) motifs in their genome, which are associated with natural competence for DNA uptake. The mechanism of their recognition is still unclear, and I searched for intragenic location patterns of these motifs for clues about their distribution. In all cases, one orientation of the US has a higher occurrence in the reading frame, and in all Pasteurellaceae, the US and the reverse complement motifs are biased towards the gene termini. These findings could help design experimental set-ups to study preferential DNA uptake, thereby further unravelling the phenomenon of natural competence.     

<Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> inhibits <Emphasis Type="Italic">in-vitro Candida</Emphasis> biofilm development

Background  

Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as Candida spp. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of Pseudomonas aeruginosa and six different species of Candida comprising C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis, and C. dubliniensis in dual species biofilm development.     

Cloning and expression of <Emphasis Type="Italic">mel</Emphasis> gene from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Previous work from our laboratory has shown that most of Bacillus thuringiensis strains possess the ability to produce melanin in the presence of l-tyrosine at elevated temperatures (42 °C). Furthermore, it was shown that the melanin produced by B. thuringiensis was synthesized by the action of tyrosinase, which catalyzed the conversion of l-tyrosine, via l-DOPA, to melanin. In this study, the tyrosinase-encoding gene (mel) from B. thuringiensis 4D11 was cloned using PCR techniques and expressed in Escherichia coli DH5 . A DNA fragment with 1179 bp which contained the intact mel gene in the recombinant plasmid pGEM1179 imparted the ability to synthesize melanin to the E. coli recipient strain. The nucleotide sequence of this DNA fragment revealed an open reading frame of 744 bp, encoding a protein of 248 amino acids. The novel mel gene from B.thuringiensis expressed in E. coli DH5 conferred UV protection on the recipient strain.