Evaluation of copper uptake in individual spores of Streptomyces coelicolor and endogenic nanoparticles formation to modulate the secondary metabolism.

Copper modulates secondary metabolism in Streptomyces. Although the cytosolic copper concentration is controlled by several chaperones and transporters, the formation of copper nanoparticles (NPs) and its relation to the antibiotic production has never been established in the model Streptomyces coelicolor. In this work, state-of-the-art analytical tools are used to evaluate the incorporation of copper in individual spores of S. coelicolor at different exposure concentrations (40, 80, and 160 μM Cu). Among them, the use of single cell-inductively coupled plasma-mass spectrometry revealed incorporation levels in the range of 2 to 2.5 fg/spore (median) increasing up to 4.75 fg/spore at the upper exposure concentrations. The copper storage within the spores in the form of NPs was evaluated using a combination of single particle-inductively coupled plasma-mass spectrometry and transmission electron microscopy. The obtained data confirmed the presence of NPs in the range of 8 to 40 (mean size 21 nm) inside S. coelicolor spores. The presence of the NPs was correlated with the actinorhodin production in liquid non-sporulating cultures amended with up to 80 μM Cu. However, further increase to 160 μM Cu, yielded to a significant decrease in antibiotic production. Secondary metabolism is activated under stressful conditions and cytosolic copper seems to be one of the signals triggering antibiotic production. Particularly, NP formation might contribute to modulate the secondary metabolism and prevent for copper toxicity. This work describes, for first time, the formation of endogenous copper NPs in S. coelicolor and reveals their correlation with the secondary metabolism.