The triple protease mutant P. gingivalis fared worse, infecting only about a third of all cells at the same m.o.i. Although it is possible that some cells were infected at levels below the threshold of visible fluorescence, and therefore, were scored as uninfected, we can conclude that infection of HGF by P. gingivalis is a relatively inefficient process and that the Arg- and Lys-gingipains are not absolutely essential for invasion but improve the efficiency. Here, HGF is linked to infection.