Molecular Characterization Classification

In common with many other genera, the classification of Actinomyces has been revolutionized by the application of 16S rRNA nucleotide sequence analysis. Early results were obtained by laborious reverse transcriptase meth-ods.[2] However, rapid advances in DNA amplification, sequencing techniques, and data analysis software enabled the comprehensive phylogenetic analysis of the genus.[3] As a result, some former Actinomyces species have been transferred to other genera (e.g., Arcanobacterium pyo-genes) and some novel genera (e.g., Actinobaculum, Varibaculum) and a plethora of novel species have been described. These include, from human sources, A. radingae, A. turicensis, A. europaeus, A. graevenitzii, A. radicidentis, A. urogenitalis, A. funkei, and Actinomy-ces cardiffensis. Additional novel species are indicated both from organisms cultivated from clinical materials1-4-1 and from uncultivated clones.[5,6] Furthermore, these and other studies have demonstrated extensive genetic heterogeneity within strains currently assigned to the A. naeslundii/viscosus complex and, to a lesser extent, within A. israelii, A. odontolyticus, and some other species.

The robustness of current classification is ensured by the use of a polyphasic taxonomic approach, whereby phylogenetic divisions are supported by those derived from chemotaxonomic markers and phenotypic characteristics. Determination of cell wall sugars and amino acids, fatty acids, phospholipids, and menaquinones, and whole-cell protein profiling by sodium dodecyl sulfate poly-acrylamide gel electrophoresis (SDS-PAGE) has been utilized. Collectively, these analyses indicate that the genus Actinomyces represents at least three separate genera, as yet to be formally classified.[7]

Many clinicians and clinical microbiologists view taxonomic revisions as purely academic exercises—at best, irrelevant, and, at worst, confusing. However, a robust and discriminatory classification system, coupled with reliable means of identification, is a prerequisite for a meaningful analysis of prevalence, habitats, clinical associations, and potential pathogenicity of microorganisms. In addition, knowledge of genetic specificity and diversity within target species is essential for the development of DNA probes for direct detection of pathogens in clinical materials.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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