Establishment of an induced memory response in Pseudomonas aeruginosa during infection of a eukaryotic host

Abstract

In a given habitat, bacterial cells often experience recurrent exposures to the same environmental stimulus. The ability to memorize the past event and to adjust current behaviors can lead to efficient adaptation to the recurring stimulus. Here we demonstrate that the versatile bacterium Pseudomonas aeruginosa adopts a virulence phenotype after serial passage in the invertebrate model host Galleria mellonella. The virulence phenotype was not linked to the acquisition of genetic variations and was sustained for several generations, despite cultivation of the ex vivo virulence-adapted P. aeruginosa cells under rich medium conditions in vitro. Transcriptional reprogramming seemed to be induced by a host-specific food source, as reprogramming was also observed upon cultivation of P. aeruginosa in rich medium supplemented with polyunsaturated long-chain fatty acids. The establishment of induced memory responses adds a time dimension and seems to fill the gap between long-term evolutionary genotypic adaptation and short-term induced individual responses. Efforts to unravel the fundamental mechanisms that underlie the carry-over effect to induce such memory responses will continue to be of importance as hysteretic behavior can serve survival of bacterial populations in changing and challenging habitats.

Parallel evolutionary paths to produce more than one Pseudomonas aeruginosa biofilm phenotype

“…Figure 5a depicts the in vivo virulence phenotype of cluster A, B, and C isolates as determined in the Galleria mellonella assay. 59 In stark contrast to isolates of cluster A and C, isolates of cluster B were almost avirulent. An in vitro infection assay using human epithelial A549 cells showed a significant reduced cytotoxicity of cluster B isolates ( Fig.…”

“…To determine biofilm structures in a high content screen, we used our strain collection of 414 well-characterized clinical P. aeruginosa isolates, for which in vivo virulence data in the Galleria mellonella infection model 59 and images of the colony morphology (including hemolysis on Columbia agar) 72 were available. Furthermore, transcriptional profiles under planktonic conditions have been recorded for all 414 strains in the frame of a previous study.…”

“…A collection of 414 clinical P. aeruginosa isolates, which have previously been sampled from several clinical microbiology laboratories across Europe, 42,59,72 was screened for biofilm phenotypes through the use of a high content static microtiter plate assay combined with automated CLSM. 73 In brief, bacteria were grown overnight in LB at 37°C and 100 µl of bacterial suspension with an adjusted OD 600 of 0.002 were added to the wells of a sterile half-area 96-well µClear microtiter plate (Greiner Bio-One, Austria).…”

Expression of the MexXY Aminoglycoside Efflux Pump and Presence of an Aminoglycoside-Modifying Enzyme in Clinical Pseudomonas aeruginosa Isolates Are Highly Correlated

“…We analyzed efflux pump gene expression in 412 clinical P. aeruginosa isolates, which have been previously collected from different laboratories and clinics and for which transcriptional profiles have been recorded (28). The RNA sequencing (RNA-Seq) data of the clinical isolates have been uploaded to NCBI's Gene Expression Omnibus on November 2, 2020 by guest http://aac.asm.org/ Downloaded from (GSE122938).…”

Untargeted LC-MS Metabolomics Differentiates Between Virulent and Avirulent Clinical Strains of Pseudomonas aeruginosa

“…Hence, we tested whether the virulence properties of P. aeruginosa clinical strains can be differentiated by untargeted LC-MS metabolomics. Metabolomics data for 35 clinical isolates recovered from diverse infection sites were acquired, stratified according to in vivo virulence phenotypes in the Galleria mellonella infection model [34] and biofilm phenotypes [15] and analyzed for discriminating markers. Data on the metabolite level and metabolic profiles were investigated, and a statistical model was generated to differentiate virulent and avirulent strains based solely on LC-MS data.…”