The minimal mobile element

Microbiology (Impact Factor: 2.56). 01/2003; 148(Pt 12):3756-60. DOI: 10.1099/00221287-148-12-3756
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Available from: Lori A S Snyder, Sep 29, 2015
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    • "Such organization is reminiscent of minimal mobile elements, where an acquired cassette-like is located between highly conserved flanking genes (Saunders and Snyder, 2002). The majority of these cassettes encode restriction and modification systems (Snyder et al., 2007). "
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    ABSTRACT: Neisseriacae do not exhibit Dam methyltransferase activity and, instead of the dam gene, possess drg (dam replacing gene) inserted in the leuS/dam locus. The drg locus in Neisseria gonorrhoeae FA1090 has a lower GC-pairs content (40.5%) compared to the whole genome of N. gonorrhoeae FA1090 (52%). The gonococcal drg gene encodes a DNA endonuclease Drg, with GmeATC specificity. Disruption of drg or insertion of the dam gene in gonococcal genome changes the level of expression of genes as shown by transcriptome analysis. For the drg-deficient N. gonorrhoeae mutant, a total of 195 (8.94% of the total gene pool) genes exhibited an altered expression compared to the wt strain by at least 1.5 fold. In Dam-expressing N. gonorrhoeae mutant, the expression of 240 genes (11% of total genes) was deregulated. Most of these deregulated genes were involved in translation, DNA repair, membrane biogenesis and energy production as shown by cluster of orthologous group analysis. In vivo, the inactivation of drg gene causes the decrease of the number of live neisserial cells and long lag phase of growth. The insertion of dam gene instead of drg locus restores cell viability. We have also shown that presence of the drg gene product is important for N. gonorrhoeae FA1090 in adhesion, including human epithelial cells, and biofilm formation. Biofilm produced by drg-deficient strain is formed by more dispersed cells, compared to this one formed by parental strain as shown by scanning electron and confocal microscopy. Also adherence assays show a significantly smaller biomass of formed biofilm (OD570= 0.242 +/- 0.038) for drg-deficient strain, compared to wild type strain (OD570= 0.378 +/- 0.057). Dam-expressing gonococcal cells produce slightly weaker biofilm with embedded in extracellular matrix cells. This strain has also a 5 times reduced ability for adhesion to human epithelial cells. In this context, the presence of Drg is more advantageous for N. gonorrhoeae biology than Dam presence.
    Frontiers in Microbiology 12/2014; 5. DOI:10.3389/fmicb.2014.00712 · 3.99 Impact Factor
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    • "Homologous recombination at the conserved flanking genes would account for this phenomenon whereby gene organization was identical between distantly related genomes but different between the closely related ST60 genomes. These regions displayed characteristics of minimal mobile elements , which were defined as variable regions among the closest relatives in sequence composition and gene content between specific conserved flanking genes (Saunders and Snyder 2002; Snyder et al. 2007). Among the nine regions, only the glnD-guaB region (fig. "
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    ABSTRACT: The study of genetic and phenotypic variation is fundamental for understanding the dynamics of bacterial genome evolution and untangling the evolution and epidemiology of bacterial pathogens. Neisseria meningitidis (Nm) is among the most intriguing bacterial pathogens in genomic studies due to its dynamic population structure and complex forms of pathogenicity. Extensive genomic variation within identical clonal complexes in Nm has been recently reported and suggested to be the result of homologous recombination, but the extent to which recombination contributes to genomic variation within identical clonal complexes has remained unclear. In this study, we sequenced two Nm strains of identical serogroup (C) and multi-locus sequence type (ST60), and conducted a systematic analysis with an additional 34 Nm genomes. Our results revealed that all gene content variation between the two ST60 genomes was introduced by homologous recombination at the conserved flanking genes, and 94.25% or more of sequence divergence was caused by homologous recombination. Recombination was found in genes associated with virulence factors, antigenic outer membrane proteins, and vaccine targets, suggesting an important role of homologous recombination in rapidly altering the pathogenicity and antigenicity of Nm. Recombination was also evident in genes of the restriction and modification systems, which may undermine barriers to DNA exchange. In conclusion, homologous recombination can drive both gene content variation and sequence divergence in Nm. These findings shed new light on the understanding of the rapid pathoadaptive evolution of Nm and other recombinogenic bacterial pathogens.
    Genome Biology and Evolution 07/2013; 5(9). DOI:10.1093/gbe/evt116 · 4.23 Impact Factor
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    • "Of the 5 previously reported genes disrupted by CREE insertion [8,21,22], 4 are associated with CREE in these two gonococcal genome sequences (Table 3). In the case of NMA2121, this CDS is not present in strain FA1090 as it is part of a Minimal Mobile Element [22,39,40], which facilitates horizontal exchange of gene cassettes between genome sequences. "
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    ABSTRACT: The Correia Repeat Enclosed Element (CREE) of the Neisseria spp., with its inverted repeat and conserved core structure, can generate a promoter sequence at either or both ends, can bind IHF, and can bind RNase III and either be cleaved by it or protected by it. As such, the presence of this element can directly control the expression of adjacent genes. Previous work has shown differences in regulation of gene expression between neisserial strains and species due to the presence of a CREE. These interruptions perhaps remove the expression of CREE-associated genes from ancestral neisserial regulatory networks. Analysis of the chromosomal locations of the CREE in Neisseria gonorrhoeae strain FA1090 and N. gonorrhoeae strain NCCP11945 has revealed that most of the over 120 copies of the element are conserved in location between these genome sequences. However, there are some notable exceptions, including differences in the presence and sequence of CREE 5' of copies of the opacity protein gene opa, differences in the potential to bind IHF, and differences in the potential to be cleaved by RNase III. The presence of CREE insertions in one strain relative to the other, CREE within a prophage region, and CREE disrupting coding sequences, provide strong evidence of mobility of this element in N. gonorrhoeae. Due to the previously demonstrated role of these elements in altering transcriptional control and the findings from comparing the two gonococcal genome sequences, it is suggested that regulatory differences orchestrated by CREE contribute to the differences between strains and also between the closely related yet clinically distinct species N. gonorrhoeae, Neisseria meningitidis, and Neisseria lactamica.
    BMC Genomics 03/2009; 10(1). DOI:10.1186/1471-2164-10-70 · 3.99 Impact Factor
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