P081

1:University of Veterinary Medicine Hannover; 2:Helmholtz Centre for Infection Research

Cobalt is an important transition metal, incorporated e.g. in corrinoid metalloproteins such as the essential vitamin B12. 90% of all bacteria possess vitamin B12 dependent enzymes involved in central metabolic processes and host-pathogen interaction, however only 25-30% are able to produce vitamin B12 de novo, including many non-tuberculous mycobacteria (NTM) such as Mycobacterium abscessus. For the production of vitamin B12, cobalt uptake is essential. An important system for cobalt import, e.g. in Salmonella Typhimurium, is the energy-dependent ECF transporter CbiMNQO. Genes are present in many other bacteria. Associated regulators of this system are unknown. No cobalt importers including CbiMNQO have been analyzed in mycobacteria.

We analyzed an operon encoding for a putative CbiMNQO transporter (msmeg_2607-2610) in the non-pathogenic model organism M. smegmatis (MSwt), associated with an ArsR/SmtB family regulator (msmeg_2606, designated CbiR) and genes involved in vitamin B12 biosynthesis (msmeg_2616-2618). By transcriptome analyses of MSwt and an MS∆cbiR mutant, we identified the CbiR regulon, including cbiMNQO, and a CbiR binding motif. A cobalt/nickel (Co/Ni) dependent regulation of cbiMNQO by CbiR was shown by RT-PCR, reporter studies and ChIP-Seq analyses of cultures grown in metal depleted Sauton’s medium or supplemented with different cations. A MS∆cbiMN transporter mutant was analyzed for metal dependent growth and vitamin B12 production. Compared to MSwt no difference was observed. However, this is the first report of a regulator involved in Co/Ni dependent regulation of a putative Co/Ni importer CbiMNQO in mycobacteria. These findings might help understanding cobalt/nickel homeostasis in other mycobacteria and identifying potential NTM-treatment strategies.