Growth of AAP in the presence of different K2TeO3 concentrations confirmed these bacteria possess a high level resistance. Strains appear to be similar, resisting and reducing up to 1500 µg/mL, however, optimal growth and reduction occurred at 500 µg/mL K2TeO3 for E1, E4(1), E5, and KR99, while 100 µg/mL K2TeO3 was best for RB3 and RB 16-17. With respect to media composition, we observed that it does have an effect, as has been previously reported . Although many different carbon sources and combinations were tested, only three media compositions gave optimal growth and reduction. Strains E4(1), RB3, and RB 16-17 performed best in complex RO medium, while E5 and KR99 preferred defined MS medium containing a combination of glutamate, malate, and pyruvate. E1 showed the best results in MS medium with glutamate and pyruvate, however, some yeast extract was still required, suggesting a need for the undefined component of this complex organic substrate. To determine if the specific combination, but not the increased organics, was responsible for increased growth and reduction with tellurite, each individual source was tested at 3.0 g/L. Single organic carbon sources at increased concentrations were not as good as the combination. All tested strains grew and reduced K2TeO3 optimally at pH 9.0 and aeration was achieved at 200 rpm (Table 1). However, reduction still occurred at 100 and 300 rpm, albeit at much reduced levels.