Similar considerations can explain the mild attenuation of B. suis 1330 ribose kinase (rbsk) and 6-phosphogluconate dehydrogenase (gnd) Tn5 mutants observed in macrophage-like human THP-1 cells 48 h after infection (log CFU reduction for both mutants of 1.8 vs. 5 for genes involved in amino acid synthesis) (Köhler et al., 2002). Here, RBKS is linked to infection.