Iron dependent gene regulation and siderophore systems in Vibrionaceae

Abstract

Bacteria live in fluctuating environments, which they sense and respond to through gene regulation. Availably of iron is an example of an element fluctuating and that can Bacteria sense.Iron is an essential micronutrient that is scares in several environments, especially in a host. The ferric uptake regulator, Fur, is the major iron level sensing protein and regulator of iron acquisition systems in Bacteria. Fur act in a repressive manner. Under low iron conditions, Fur is inactive and iron acquisition systems are expressed. Within the Vibrionaceae bacterial family, there are several pathogen representatives with sophisticated iron acquisition systems. The iron acquisition systems are essential for survival and the virulence of the pathogen colonizing a host. In the present work, the cold-adapted fish pathogen Vibrionaceae representative, Aliivibrio salmonicida, has been used as a model for understanding the Fur regulon and the immediate responses of iron limitations. Also, the siderophore-based iron acquisition systems of the Vibrionaceae family have been investigated. In Paper 1, transcriptomic studies resulted in identification of the first transcriptional responses of A. salmonicida to iron limitations. Pan-transcriptome studies identified shared and unique strategies to iron limitations between the Vibrionaceae representatives, A. salmonicida, Vibrio vulnificus, and Vibrio cholerae. In Paper 2, transcriptomic studies of an A. salmonicida fur null mutant provide deeper and more fine-grained data of the Fur regulon in A. salmonicida. Also, targets are predicted for the sRNA RyhB and novel small RNA predictions are provided. Paper 3, provide deeper understanding of the patterns, origin, distribution, and evolution of Vibrionaceae siderophore biosynthesis systems and receptors. Overall, results from these studies have increased our understanding of the A. salmonicida Fur regulon and strategies of surviving iron limitations. For the Vibrionaceae siderophore based iron acquisition systems, we have broadened the knowledge of distribution of the siderophore biosynthesis systems, receptors and the evolution within the family.