Changes in growth, lanthanide binding, and gene expression in Pseudomonas alloputida KT2440 in response to light and heavy lanthanides

Pseudomonas alloputida KT2440 is a ubiquitous, soil-dwelling bacterium that metabolizes recalcitrant and volatile carbon sources. The latter are utilized by two redundant, Ca- and lanthanide (Ln)-dependent, pyrroloquinoline quinone-dependent alcohol dehydrogenases (PQQ ADH), PedE and PedH, whose expression is regulated by Ln availability. P. alloputida KT2440 is the best-studied, non-methylotroph in the context of Ln-utilization. We report the most comprehensive differential gene expression analysis, to date, for any Ln-utilizing microbe. Combined with microfluidic cultivation and single-cell elemental analysis, we studied the impact of light and heavy Ln when growing P. alloputida KT2440 with 2-phenylethanol as the carbon and energy source. Light Ln (La, Ce, Nd) and a mixture of light and heavy Ln (La, Ce, Nd, Dy, Ho, Er, Yb) had a positive effect on growth, while supplementation with heavy Ln (Dy, Ho, Er, Yb) exerted fitness costs. These were likely a consequence of mismetallation and oxidative stress. Gene expression analysis showed that the Ln sensing and signaling machinery, the two-component system PedS2R2 and PedH, responds differently to (non-)utilizable Ln. We broadened the understanding of the Ln switch in P. alloputida KT2440 and could show that it operates as a dimmer switch, modulating the pool of PQQ ADH dependent on Ln availability. Determined quantities of cell-associated Ln suggest a role for Ln beyond alcohol oxidation. The usability of Ln governs the response of P. alloputida KT2440 to different Ln elements.