Upon halting protein synthesis with tetracycline or chloramphenicol, we found strains E1, E5, KR99, RB3, and RB 16-17 were still capable of reducing tellurite, supporting a constitutive system. In cells of E4(1) reduction was inhibited, indicating de novo preparations are required. To further support the idea that the enzyme(s) responsible for reduction are constitutive, reduction in the cell lysates was analyzed (Figure 3). Lysates of E1, E5, KR99, RB3, and RB 16-17 cells were capable of reducing K2TeO3 without prior exposure (Figure 3A), whereas those of E4(1) could not (Figure 3B), even following exposure (Figure 3C).