Long-term culturing of Pseudomonas aeruginosa in static, minimal nutrient medium results in increased pyocyanin production, reduced biofilm production, and loss of motility

TL;DR

This study shows how Pseudomonas aeruginosa adapts to low-nutrient environments, leading to changes in traits like pyocyanin production and motility.

Contribution

The study reveals novel phenotypic and genotypic adaptations of P. aeruginosa under long-term low-nutrient conditions.

Findings

Adaptation to low-nutrient environments increased pyocyanin production and decreased biofilm formation and motility.

Some evolved isolates showed increased virulence/competitiveness against phagocytic predators.

Adaptation led to reduced cell size and decreased generation time in some strains.

Abstract

Pseudomonas aeruginosa is a multidrug-resistant
opportunistic human pathogen that can survive in many natural and
anthropogenic environments. It is a leading cause of morbidity in
individuals with cystic fibrosis and is one of the most prevalent pathogens
associated with nosocomial infections in the United States. It has been
shown that this organism can survive and persist in low-nutrient
environments, such as sink drains. How adaptation to these types of
environments influences the phenotypic traits of this organism has not been
well studied. Here, we implemented an experimental evolution system in which
six strains of P. aeruginosa were subjected to low-nutrient
conditions over the course of 12 weeks and assessed phenotypic and genotypic
changes that occurred as a result of adaptation to such environments. We
observed that adaptation to low-nutrient environments resulted in decreased
generation time, reduced cell size, reduced biofilm formation, increased
pyocyanin production, and decreased motility for some of the strains.
Furthermore, some of the evolved isolates were significantly more
virulent/competitive against a phagocytic predator. This study is
significant as it allows us to predict how this organism will evolve in
hospital and domestic environments and can help us improve treatment options
for patients.

Human commensal and pathogenic organisms undergo dynamic cycles across
human and non-human environments. Despite the crucial implications for
human health, the understanding of bacterial adaptations to these
diverse environments and their subsequent impact on human-bacterial
interactions remains underexplored. This study shows how
Pseudomonas aeruginosa, an opportunistic human
pathogen, adapts phenotypically in response to a shift from high
nutrients (like those found in the human body) to low nutrients (like
those found in many other environments, like sink drains). This work
also shows that, in some cases, resistance to predatory forces can
evolve in the absence of a predator. This work is important as it
contributes to the growing body of knowledge concerning how external,
non-host-related abiotic conditions influence host–pathogen
interactions.

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