Generalized Growth of Estuarine, Household and Clinical Isolates of Pseudomonas aeruginosa.

Kelly E Diaz,Paul E Turner,Ogochukwu Onyiri,Susanna K Remold,Peter A Raymond,Maura Bozeman

doi:10.3389/fmicb.2018.00305

Kelly E Diaz, Paul E Turner + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2018.00305

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Abstract

Pseudomonas aeruginosa is an opportunistic pathogen of particular concern to immune-compromised people, such as cystic fibrosis patients and burn victims. These bacteria grow in built environments including hospitals and households, and in natural environments such as rivers and estuaries. However, there is conflicting evidence whether recent environments like the human lung and open ocean affect P. aeruginosa growth performance in alternate environments. We hypothesized that bacteria recently isolated from dissimilar habitats should grow differently in media containing artificial versus natural resources. To test this idea, we examined growth of P. aeruginosa isolates from three environments (estuary, household, and clinic) in three media types: minimal-glucose lab medium, and media prepared from sugar maple leaves or big bluestem grass. We used automated spectrophotometry to measure high-resolution growth curves for all isolate by media combinations, and studied two fitness parameters: growth rate and maximum population density. Results showed high variability in growth rate among isolates, both overall and in its dependence on assay media, but this variability was not associated with habitat of isolation. In contrast, total growth (change in absorbance over the experiment) differed overall among habitats of isolation, and there were media-specific differences in mean total growth among habitats of isolation, and in among-habitat variability in the media-specific response. This was driven primarily by greater total growth of estuary isolates when compared with those from other habitats of origin, and greater media-specific variability among household isolates than those from other habitats of origin. Taken together, these results suggest that for growth rate P. aeruginosa bacteria appear to be broad generalists without regard to current or recent habitat, whereas for total growth a signature of recent ecological history can be detected.

Highlights

Pseudomonas aeruginosa bacteria thrive in a wide variety of environments, and can be free-living in both natural and built-environment settings (Kimata et al, 2003; Khan et al, 2007; Remold et al, 2011; Kidd et al, 2012; Selezska et al, 2012; Purdy-Gibson et al, 2015)
Because growth performance can be interpreted in multiple ways, comparisons between the isolates were made using two summary parameters that address different aspects of performance: the maximum growth rate of each isolate in each medium was assessed using Curve Fitter2, and the total growth was measured as total change in absorbance in each medium type
We address two competing hypotheses: (i) that P. aeruginosa bacteria are broad generalists, and that the phenotypic variability among isolates is not associated with current or recent ecology, and (ii) that isolates from the same habitat are more phenotypically similar to one another than they are to isolates from different habitats

Summary

Introduction

Pseudomonas aeruginosa bacteria thrive in a wide variety of environments, and can be free-living in both natural and built-environment settings (Kimata et al, 2003; Khan et al, 2007; Remold et al, 2011; Kidd et al, 2012; Selezska et al, 2012; Purdy-Gibson et al, 2015). These bacteria are opportunistic pathogens of humans, especially important in respiratory and urinary. Does recent ecological history affect P. aeruginosa growth performance across habitats?

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