bAlthough Streptomyces coelicolor is not resistant to tellurite, it possesses several TerD domain-encoding (tdd) genes of unknown function. To elucidate the function of tdd8, the transcriptomes of S. coelicolor strain M145 and of a tdd8 deletion mutant derivative (the ⌬tdd8 strain) were compared. Several orthologs of Mycobacterium tuberculosis genes involved in dormancy survival were upregulated in the deletion mutant at the visual onset of prodiginine production. These genes are organized in a putative redox stress response cluster comprising two large loci. A binding motif similar to the dormancy survival regulator (DosR) binding site of M. tuberculosis has been identified in the upstream sequences of most genes in these loci. A predicted role for these genes in the redox stress response is supported by the low NAD ؉ /NADH ratio in the ⌬tdd8 strain. This S. coelicolor gene cluster was shown to be induced by hypoxia and NO stress. While the tdd8 deletion mutant (the ⌬tdd8 strain) was unable to maintain calcium homeostasis in a calcium-depleted medium, the addition of Ca 2؉ in ⌬tdd8 culture medium reduced the expression of several genes of the redox stress response cluster. The results shown in this work are consistent with Tdd8 playing a significant role in calcium homeostasis and redox stress adaptation.

No abstract

TerD-domain-encoding genes (tdd genes) are highly represented in the Streptomyces coelicolor genome. One of these, the tdd8 gene, was recently shown to have a crucial influence on growth, differentiation, and spore development of this filamentous bacterium. The investigation of the potential role of tdd genes has been extended here to tdd7 (SCO2367) and tdd13 (SCO4277). Both genes are highly expressed in bacteria grown in liquid-rich medium (tryptic soy broth). However, the deletion of these genes in S. coelicolor showed contrasting effects regarding developmental patterns, sporulation, and antibiotic production. Deletion of the tdd7 gene induced a reduction of growth in liquid medium, wrinkling of the mycelium on solid medium, and poor spore and actinorhodin production. On the other hand, deletion of the tdd13 gene did not significantly affect growth in liquid medium but induced a small colony phenotype on solid medium with abundant sporulation and overproduction of undecylprodigiosin. Although their exact functions remain undefined, the present data suggest a major involvement of TerD proteins in the proper development of S. coelicolor.