Four newly identified CRISPR-Cas9 inhibitor proteins encoded by Listeria monocytogenes prophages prevent Cas9 binding and gene editing in bacteria and human cells, including currently the most widely used Cas9 from Streptococcus pyogenes. Image credit: Benjamin J. Rauch et al, doi: 10.1016/j.cell.2016.12.009.
The group A streptococcus bacterium (Streptococcus pyogenes, or GAS) is a form of β-hemolytic Streptococcus bacteria responsible for most cases of streptococcal illness. Other types (B, C, D, and G) may also cause infection. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes.
Bacitracin test done on a lawn of Streptococcus pyogenes grown on blood agar. The zone of inhibition around the bacitracin disc, approx 14mm measuring the entire length of the zone, indicates sensitivity. The zone of inhibition is red because the red blood cells did not lyse. Grown for 24 hrs at 37 degree's C.