Iron Acquisition from Natural Organic Matter by an Aerobic Pseudomonas mendocina Bacterium: Siderophores and Cellular Iron Status

Abstract

This research investigated the potential role of siderophores in aerobic microbial Fe acquisition from natural organic matter (NOM; XAD-8 isolate and reverse osmosis concentrate pre- and post-Chelex® treatment) through the use of a siderophore-producing Pseudomonas mendocina wild type (WT) bacterium and an engineered mutant (Mt) that was incapable of siderophore production. NOM had complex effects on microbial growth under Fe-limited conditions as measured by optical density, most likely because of the presence of other toxic (trace) metals such as Al, NOM binding interference with additional trace metal nutrients, and/or biofilm development. However, a bioassay for cellular Fe status showed that both WT and Mt readily acquired Fe naturally associated with NOM. Thus, while siderophores may be useful for Fe acquisition from NOM by P. mendocina, they do not appear to be essential for this process.

Keywords:

• Pseudomonas, natural organic matter, siderophores, aerobe, iron acquisition

Acknowledgments

K. M. Kuhn's efforts in this research were supported by a National Science Foundation Graduate Research Fellowship (NSF DGE08-22217) and C. A. Dehner's by a Bayer Predoctoral Fellowship from the Center for Environmental Science and Technology (CEST) at Notre Dame. We thank CEST for use of many of the analytical instruments used in this research. The authors thank two anonymous reviewers whose comments greatly improved the quality of this manuscript.