[SCAN] Scavenging for iron using siderophores: how did we get here?

Title: Scavenging for iron using siderophores: how did we get here?

Speaker: Ricardo Louro

From: Inorganic Biochemistry and NMR lab, ITQB NOVA

Abstract: Iron is an essential element for nearly all life forms on Earth due to its role in the assembly and function of numerous metalloenzymes.

However, its water solubility in the contemporary oxidizing conditions is very low, being mostly found in minerals that are not readily bio accessible. It is widely accepted that the use of siderophores, small molecules that bind and solubilize iron, emerged as a response to the dramatic reduction in bioavailability of this metal in aquatic environments caused by precipitation of iron oxides associated with the Great Oxidation Event (GOE). However, our recently reported molecular clock analysis of the time of emergence of siderophore biosynthesis and utilization genes challenges this view and argues for an emergence of these secondary metabolites that largely predates GOE. The emergence of NIS siderophore synthases is found to predate by more than 1 Gy that of ferric siderophore reductases and esterases, which in turn also predate the GOE by approximately 1 Gy. This temporal gap is surprising given that these enzymes are essential for microorganisms to obtain iron from siderophores. This timing of events raises questions about the original ecological drivers for the emergence of siderophores. We offer an alternative hypothesis for the origin of siderophores, which is their use in ferric mineral dissolution to avoid incrustation of neutrophilic iron oxidisers by metabolically generated ferric iron minerals. This hypothesis has since received support from observations in contemporary nitrite-reducing iron-oxidizing bacteria. The observations and hypothesis reported here highlight the importance of environmental microbe-mineral interactions, beyond nutrient acquisition, as critical selective forces in early Earth, and offer an unexpected narrative of the timing and drivers of siderophore evolution.

SCANs are weekly seminars that happen every Wednesday at noon by in-house researchers and invited speakers at ITQB NOVA.