PTPA and infection: Interference with V‐ATPase recruitment and dephosphorylation of VPS33B by PtpA are both required for the inhibition of phagosome acidification and phagosome‐lysosome fusion.7 Interestingly, although deletion of PtpA restricts bacterial growth within human THP‐1 cells,8 a deletion mutant was not attenuated for growth or virulence during in vivo infection of mice.9 This discrepancy was attributed to potential species differences affecting the activity of PtpA, such that reduced activity in a particular species would obscure any defect caused by its deletion.