MliR, a novel MerR-like regulator of iron uptake, impacts metabolism, membrane remodeling and cell adhesion in the marine Bacteroidetes Bizionia argentinensis

LEONARDO PELLIZZA; BIALER, MG; SIEIRA RODRIGO; ARAN, MARTÍN

Congreso; SAIB LVIII ANNUAL MEETING; 2022

The MerR family is a group of transcriptional activators with conserved N-terminal helix-turn-helix DNA binding domains and variable C-terminal effector binding regions. In most MerR proteins, the effector binding domain (EBD) contains a cysteine center that is suitable for metal binding and mediates the response to environmental stimuli such as oxidative stress, heavy metals or antibiotics. Here, we present a novel transcriptional regulator classified in the MerR superfamily that lacks an EBD domain and lacks conserved metal-binding sites and cysteine residues. This regulator of the psychrotolerant Bacteroidetes Bizionia argentinensis JUB59 is involved in iron homeostasis and has been named MliR (MerR-like iron responsive regulator). In silico analyzes analyses have shown that homologs of the MliR protein are widespread among different bacterial species. Deletion of the mliR gene resulted in reduced cell growth, increased cell adhesion and filament formation. Genome-wide transcriptome analysis revealed that genes associated with iron homeostasis were down-regulated in the mliR deletion mutant. Using NMR-based metabolomics, ICP-MS, fluorescence microscopy and biochemical analysis, we assessed metabolic and phenotypic changes associated with mliR deletion. This work provides the first evidence for a MerR family regulator involved in iron homeostasis and contributes to expanding our current knowledge of the relevant metabolic pathways and cellular remodeling mechanisms involved in the adaptive response to iron availability in bacteria.