Flagella can tether the bacterium to an exposed site with an accessible GM1 or asialoGM1 moiety as a very early event in establishing the nidus of infection, as described by Feldman et al. In the PAO1Tn::serA mutant, flagella were observed by conventional staining as shown in Fig 3, similar to that observed in the wild-type strain. Here, PHGDH is linked to infection.