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Genomic integration and expression of the Aggregatibacter actinomycetemcomitans catalase gene in Aggregatibacter aphrophilus.

ABSTRACT: OBJECTIVE:To test the hypothesis that virulence genes of Aggregatibacter actinomycetemcomitans can be expressed and confer fitness advantages in the closely related Aggregatibacter aphrophilus. DESIGN:Clinical isolates of A. aphrophilus were screened for natural competence with marked genomic DNA from A. actinomycetemcomitans and A. aphrophilus. The gene katA of A. actinomycetemcomitans D7S-1 and its flanking regions were constructed and inserted into a comparable locus in the genome of a naturally competent A. aphrophilus strain by a markerless protocol via natural transformation. Mutants of A. actinomycetemcomitans with or without katA were also constructed by a similar protocol. Discs soaked with either 0.03% hydrogen peroxide or broth culture of Streptococcus gordonii Challis were placed on the agar with cultures of A. actinomycetemcomitans or A. aphrophilus. The size of the growth inhibition zone associated with the disc was measured after 2-day culture. RESULTS:Five of the 13A. aphrophilus strains exhibited a transformation frequency of 10-6 or higher. The intra- and inter-species transformation frequencies were comparable. The inhibition zones for katA-negative strains of A. actinomycetemcomitans or A. aphrophilus were 3- to 7-fold larger than those associated with katA-positive strains (p<0.05). CONCLUSIONS:There was no apparent species barrier for the transfer and expression of A. actinomycetemcomitans katA in A. aphrophilus. The inserted A. actinomycetemcomitans-specific katA gene in A. aphrophilus strain NJ8700 conferred resistance to inhibition by hydrogen peroxide or S. gordonii. The potential to swap genes between these two closely related oral species may be an alternative approach for investigating the virulence determinants of A. actinomycetemcomitans.

SUBMITTER: Yang YA

PROVIDER: S-EPMC5792192 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Genomic integration and expression of the Aggregatibacter actinomycetemcomitans catalase gene in Aggregatibacter aphrophilus.

Yang Yuting Alice YA Cheng Ya-An YA Chen Casey C

Archives of oral biology 20171205

<h4>Objective</h4>To test the hypothesis that virulence genes of Aggregatibacter actinomycetemcomitans can be expressed and confer fitness advantages in the closely related Aggregatibacter aphrophilus.<h4>Design</h4>Clinical isolates of A. aphrophilus were screened for natural competence with marked genomic DNA from A. actinomycetemcomitans and A. aphrophilus. The gene katA of A. actinomycetemcomitans D7S-1 and its flanking regions were constructed and inserted into a comparable locus in the gen ...[more]

PMID: 29223024

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Project description:Gram-negative facultative Aggregatibacter actinomycetemcomitans is an oral pathogen associated with periodontitis. The genetic heterogeneity among A. actinomycetemcomitans strains has been long recognized. This study provides a comprehensive genomic analysis of A. actinomycetemcomitans and the closely related nonpathogenic Aggregatibacter aphrophilus. Whole genome sequencing by Illumina MiSeq platform was performed for 31 A. actinomycetemcomitans and 2 A. aphrophilus strains. Sequence similarity analysis shows a total of 3,220 unique genes across the 2 species, where 1,550 are core genes present in all genomes and 1,670 are variable genes (accessory genes) missing in at least 1 genome. Phylogenetic analysis based on 397 concatenated core genes distinguished A. aphrophilus and A. actinomycetemcomitans. The latter was in turn divided into 5 clades: clade b (serotype b), clade c (serotype c), clade e/f (serotypes e and f), clade a/d (serotypes a and d), and clade e' (serotype e strains). Accessory genes accounted for 14.1% to 23.2% of the A. actinomycetemcomitans genomes, with a majority belonging to the category of poorly characterized by Cluster of Orthologous Groups classification. These accessory genes were often organized into genomic islands (n = 387) with base composition biases, suggesting their acquisitions via horizontal gene transfer. There was a greater degree of similarity in gene content and genomic islands among strains within clades than between clades. Strains of clade e' isolated from human were found to be missing the genomic island that carries genes encoding cytolethal distending toxins. Taken together, the results suggest a pattern of sequential divergence, starting from the separation of A. aphrophilus and A. actinomycetemcomitans through gain and loss of genes and ending with the divergence of the latter species into distinct clades and serotypes. With differing constellations of genes, the A. actinomycetemcomitans clades may have evolved distinct adaptation strategies to the human oral cavity.

Dataset Information

Genomic integration and expression of the Aggregatibacter actinomycetemcomitans catalase gene in Aggregatibacter aphrophilus.

Publications

Genomic integration and expression of the Aggregatibacter actinomycetemcomitans catalase gene in Aggregatibacter aphrophilus.

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