The pathogenesis and molecular mechanisms underlying Listeria virulence have been particularly well studied. Many of the genes encoding proteins involved in Listeria pathogenesis are clustered in a 9-kb chromosomal fragment that is involved in functions essential to intra-cellular survival. This locus comprises genes coding for the hemolysin (hlyA), the phospholipases C (plcA and plcB), the actin-polymerizing protein (actA), the metal-oprotease (mpl), and the virulence factor regulator (prfA). Some other genetic determinants also implicated in the virulence of the bacteria, such as, for example, the internalin locus (inlAB), the invasion-associated protein gene (iap), or the clp stress response mediator locus, were also identified outside of the virulence cluster (for a review, see Ref. ). Heterogeneity in the virulence of L. monocytogenes strains has been observed. Whereas in most cases this heterogeneity is unexplained, attenuated or nonvirulent strains could be associated with truncated forms of the virulence factors InlA and ActA.[6-9]
Was this article helpful?
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.