Despite the interest in bacterial-tellurite interactions, little is known about the influence of this toxic oxyanion on aerobic anoxygenic phototrophs (AAP), which possess very high level resistance. This study is the first to address the impact of tellurite on the pigments of AAP. Three important effects of the metalloid are reported. First, tellurite (100 μg/ml) induced enhanced expression of carotenoids and/or bacteriochlorophyll (BChl) in Erythrobacter litoralis, T4; Erythromonas ursincola, KR-99; Citromicrobium bathyomarinum, JF-1; and Erythrobacter relative, EG15. Second, the influence of tellurite on cellular pigments depended strongly on culture conditions, particularly tellurite concentration (0-500 μg/ml) and organics (0.6-3 g/l). A five-fold decrease in carbon source changed the effect of the metalloid from inhibitory (42%) to stimulatory (180%) on pigment synthesis in Erythromicrobium ramosum, E5. Third, thin layer chromatography revealed tellurite (500 μg/ml) induced expression of BChl precursors such as Mg protoporphyrin in T4, constituting the first report of tetrapyrole intermediates in AAP. The metalloid also increased the synthesis of zeaxanthin, spirilloxanthin and β-carotene in T4 but inhibited others (e.g. bacteriorubixanthinal), and altered their characteristics by red- and blue-shifting the absorption peaks. Results are discussed in the context of oxidative defense mechanisms induced in AAP by tellurite.
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