Flagella restoration in Pseudomonas Fluorescens Pf0-1 in response to environmental signals

Abstract

Rhizobacteria such as Pseudomonas fluorescens are important contributors for plant health due to their involvement with nutrient uptake, regulating plant immunity and preventing colonization of pathogens. Pseudomonas fluorescens Pf0-1 is able to mediate movement by using microscopic hair-like structures called flagella. Flagella synthesis is controlled by the gene fleQ which is the master regulator because it directly impacts bacterial motility. Interestingly, findings from Taylor et al., (2015a) identify mutants that lack fleQ and eventually regain motility due to rewiring of their gene regulatory networks. Rewiring is strongly dependent on mutations found within genes that are evolutionarily related to fleQ. While mutations can influence proteins leading to crosstalk between regulatory networks, environmental signals can also influence crosstalk in a post-translational manner. Bacterial enhancer-binding proteins (bEBPs) such as FleQ are a subset of two-component regulatory systems which are influenced by the environment. We predict that bEBPs may crosstalk when environmental conditions lead to their activation. We hypothesize that bEBPs closely related to FleQ can activate depending on environmental signals and act as a substitute for FleQ without the need for mutations. In this study we identified and tested AauR, MifR and NtrC as three bEBPs which are closely related to FleQ. We also studied environmental conditions that contain glutamate, alpha ketoglutarate and ammonia as they can lead to the activation of one of these bEBPs restoring motility in P. fluorescens Pf0-1ΔfleQ strains. Additionally, by using a GFP reporter plasmid, we sought to measure gene expression data in correlation to motility restoration. This study looks to identify environmental conditions that can lead to the activation of these three bEBPs as they can restore motility in P. fluorescens Pf0-1ΔfleQ strains. Gene expression data was also collected through the use of a GFP reporter plasmid to measure fluorescence when each of the different regulators are substituted for fleQ. This research looks to provide an insight on how crosstalk between different regulatory pathways can restore detrimental gene deletions such as motility.