Speakers

• Dr. Isabelle Michaud-Soret — Centre National de la Recherche Scientifique
• Dr Olivier Neyrolles — Centre National de la Recherche Scientifique
• Prof Ricardo Louro — Universidade Nova de Lisboa

Abstract

The 28th International Biometals Webinars featured two distinct but related studies on metal homeostasis. The first explored a novel layer of spatial control, termed "effluxosomes," in bacterial metal homeostasis within *Mycobacterium tuberculosis*. P1B-type ATPases (CtpC, CtpG, CtpV), vital for the efflux of heavy metals like zinc, cadmium, and copper, operate in conjunction with small chaperone-like proteins (PacL1, PacL2, PacL3). These PacL proteins are critical for ATPase stability and metal resistance, forming mobile clusters averaging 10-13 spots per cell in the bacterial plasma membrane. These dynamic effluxosomes, stabilized by a specific JGXXT motif, also associate with diverse stress-response proteins, suggesting broader physiological roles beyond metal detoxification.

The second study investigated the evolutionary origin of siderophores, crucial small molecules for iron acquisition. Phylogenomic analysis of siderophore synthesis and processing enzymes on a calibrated tree of life revealed that siderophore synthases emerged between 4.5 and 3.5 billion years ago, predating oxygenic photosynthesis. However, siderophore-reducing enzymes and esterases appeared approximately 1 billion years later. This temporal disparity suggests an initial role for siderophores beyond iron scavenging. It is hypothesized that early siderophores evolved to prevent the encrustation of neutrophilic iron-oxidizing microbes by ferric minerals, a balance critical for UV protection and cellular division in the early Earth's environment.

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