Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen causing infections in a variety of plant and animal hosts. The gene mcpB, part of the chemosensory gene cluster II, encodes a soluble chemoreceptor whose function remains unknown. Previous studies show that the cheB2 gene, also located in the chemosensory cluster II, is involved in a specific response during infection and it is required for full pathogenicity of P. aeruginosa. To determine whether the McpB (or Aer2) chemoreceptor is involved in virulence processes, we generated a mcpB mutant and tested its phenotype using a virulence-measuring system. This system was developed by our group and is based on different bioassays using organisms living at different soil trophic levels, including microbial, nematode, arthropod, annelid, and plant model systems. The deletion of mcpB resulted in an attenuation of bacterial virulence in different infection models, and wild-type virulence was restored following genetic complementation of the mutant strain. Our study indicates that the McpB chemoreceptor is linked to virulence processes and may constitute the basis for the development of alternative strategies against this pathogen.
Highlights
The Gram-negative bacterium Pseudomonas aeruginosa is a widespread opportunistic human pathogen responsible for multiple hospital-acquired infections, mainly in immunocompromised and cystic fibrosis patients[1,2]
We evaluated the effects of the wild-type P. aeruginosa PAO1 (PAO1 wt) and ΔmcpB on the number of eggs laid, number of juvenile and adult nematodes, and death rates[25,32]
Our results showed that the ΔmcpB exhibited lower nematicidal activities compared to the PAO1 wt strain (Fig. 2)
Summary
The Gram-negative bacterium Pseudomonas aeruginosa is a widespread opportunistic human pathogen responsible for multiple hospital-acquired infections, mainly in immunocompromised and cystic fibrosis patients[1,2]. Other chemosensory pathways are associated with type IV pili-mediated taxis or have been shown to regulate alternative cell functions, such as the modulation of the intracellular levels of the bacterial second messengers cAMP and c-di-GMP11–13. Gene cluster II encodes proteins of the Che[2] pathway, which was originally associated with aerotaxis[15] but its function remains controversial, since this role in aerotaxis could not be reproduced in subsequent studies[14,16]. Cluster II consists of eight genes encoding the chemosensory proteins CheB2, CheD, CheR2, CheW2, CheA2 and CheY, as well as the chemoreceptors McpB (Aer2) and McpA14 (Fig. 1B). Proteins encoded by cluster II have been shown to form complexes that co-localize at cell poles, and the requirement of McpB for the formation of these complexes has been demonstrated[16]. The PAS-type ligand binding domain of McpB contains bound heme[18] and a recent study showed that oxygen is the native ligand of McpB19
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