scholarly journals Protozoan predation drives adaptive divergence in Pseudomonas fluorescens SBW25; ecology meets experimental evolution.

2021 ◽  
Author(s):  
Farhad S. Golzar ◽  
Gayle C. Ferguson ◽  
Heather L Hendrickson
Keyword(s):  
Pseudomonas Fluorescens ◽  
Adaptive Divergence ◽  
Predator Prey ◽  
Solid Media ◽  
Short Period ◽  
Bacterial Mutants ◽  
Evolution Experiment ◽  
Grazing Resistance ◽  
Pseudomonas Fluorescens Sbw25 ◽  
Air Liquid Interface

Protozoan predators can affect the structure of bacterial communities, but investigations of how predation might influence bacterial evolution and antagonistic behaviours are scarce. Here, we performed a 20-day predator-prey evolution experiment on solid media to investigate the effect of continuous protozoan predation on bacterial traits using Pseudomonas fluorescens SBW25 as prey and Naegleria gruberi as an amoeboid predator. We observed the divergence of colony morphotypes coincident with an increase in bacterial grazing resistance and relative prey fitness in selected bacterial isolates. When subjected to these resistant prey, N. gruberi show reduced activity (increased encystment) and limited replication. An investigation of the mutations responsible for predation resistance reveals mutations in wspF and amrZ genes, affecting biofilm formation and motility. The bacterial mutants in the wspF gene successfully colonise the air-liquid interface and produce robust cellulose biofilms that prevent predation. The mutation in the amrZ mutant withstands predation but this variant produces low levels of cellulose and limited swarming motility. Our findings suggest that protozoan predation can profoundly influence the course of genetic and phenotypic evolution in a short period.

The Pseudomonas fluorescens SBW25 wrinkly spreader biofilm requires attachment factor, cellulose fibre and LPS interactions to maintain strength and integrity

Microbiology ◽  
2005 ◽  
Vol 151 (9) ◽  
pp. 2829-2839 ◽  
Author(s):  
Andrew J. Spiers ◽  
Paul B. Rainey
Keyword(s):  
Pseudomonas Fluorescens ◽  
Insertion Site ◽  
Cellulose Fibre ◽  
Cellulose Fibres ◽  
Pseudomonas Fluorescens Sbw25 ◽  
Increased Strength ◽  
Biofilm Development ◽  
Air Liquid Interface ◽  
Attachment Factor ◽  
Fibre Matrix

The wrinkly spreader (WS) isolate of Pseudomonas fluorescens SBW25 forms a substantial biofilm at the air–liquid interface. The biofilm is composed of an extracellular partially acetylated cellulose-fibre matrix, and previous mutagenesis of WS with mini-Tn5 had identified both the regulatory and cellulose-biosynthetic operons. One uncharacterized WS mutant, WS-5, still expressed cellulose but produced very weak biofilms. In this work, the mini-Tn5 insertion site in WS-5 has been identified as being immediately upstream of the tol-pal operon. Like Tol-Pal mutants of other Gram-negative bacteria, WS-5 showed a ‘leaky-membrane’ phenotype, including the serendipitous ability to utilize sucrose, increased uptake of the hydrophilic dye propidium iodide, and the loss of lipopolysaccharide (LPS) expression. WS-5 cells were altered in relative hydrophobicity, and showed poorer recruitment and maintenance in the biofilm than WS. The WS-5 biofilm was also less sensitive to chemical interference during development. However, growth rate, cellulose expression and attachment were not significantly different between WS and WS-5. Finally, WS-5 biofilms could be partially complemented with WS-4, a biofilm- and attachment-deficient mutant that expressed LPS, resulting in a mixed biofilm with significantly increased strength. These findings show that a major component of the WS air–liquid biofilm strength results from the interactions between LPS and the cellulose matrix of the biofilm – and that in the WS biofilm, cellulose fibres, attachment factor and LPS are required for biofilm development, strength and integrity.

scholarly journals The Role of a P1-Type ATPase from Pseudomonas fluorescens SBW25 in Copper Homeostasis and Plant Colonization

2007 ◽  
Vol 20 (5) ◽  
pp. 581-588 ◽  
Author(s):  
Xue-Xian Zhang ◽  
Paul B. Rainey
Keyword(s):  
Pseudomonas Fluorescens ◽  
Mutant Strain ◽  
Copper Ions ◽  
Biological Significance ◽  
Copper Homeostasis ◽  
Plant Colonization ◽  
Wild Type ◽  
Pseudomonas Fluorescens Sbw25 ◽  
Plant Surfaces

The genome of the plant-colonizing bacterium Pseudomonas fluorescens SBW25 possesses a putative copper-transporting P1-type ATPase (CueA) that is induced on the plant surfaces. Using a chromosomally-integrated cueA-'lacZ fusion, we show that transcription of cueA can be induced (in vitro) by ions of copper, silver, gold, and mercury. To investigate the biological significance of cueA, a nonpolar cueA deletion mutant (SBW25ΔcueA) was constructed. This mutant strain displayed a twofold reduction in its tolerance to copper compared with the wild-type strain; however, no change was observed in the sensitivity of the mutant strain to silver, gold, or mercury ions. To obtain insight into the ecological significance of cueA, the competitive ability of SBW25ΔcueA was determined relative to wild-type SBW25 in three environments (none contained added copper): minimal M9 medium, the root of sugar beet (Beta vulgaris), and the root of pea (Pisum sativum). Results showed that the fitness of SBW25ΔcueA was not different from the wild type in laboratory medium but was compromised in the two plant environments. Taken together, these data demonstrate a functional role for CueA in copper homeostasis and reveal an ecologically significant contribution to bacterial fitness in the plant rhizosphere. They also suggest that copper ions accumulate on plant surfaces.

scholarly journals The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings

Microbiology ◽  
2006 ◽  
Vol 152 (6) ◽  
pp. 1867-1875 ◽  
Author(s):  
Xue-Xian Zhang ◽  
Andrew George ◽  
Mark J. Bailey ◽  
Paul B. Rainey
Keyword(s):  
Sugar Beet ◽  
Pseudomonas Fluorescens ◽  
Bacterial Colonization ◽  
Temporal Distribution ◽  
Tetracycline Resistance ◽  
Dependent Manner ◽  
In The Wild ◽  
Pseudomonas Fluorescens Sbw25 ◽  
Functional Analyses

The ability to monitor the spatial and temporal distribution of signals in complex environments is necessary for an understanding of the function of bacteria in the wild. To this end, an existing recombinase-based transcriptional reporter strategy (recombinase-based in vivo expression technology, RIVET) has been extended and applied to the plant-colonizing bacterium Pseudomonas fluorescens SBW25. Central to the project was a rhizosphere-inducible locus, rhi14, which functional analyses show is hutT, a histidine-inducible gene that is required for histidine utilization. A transcriptional fusion between hutT and a promoterless site-specific recombinase (tnpR mut168) results in excision of a chromosomally integrated tetracycline-resistance cassette in a histidine-dependent manner. The dose- and time-responsiveness of the promoterless recombinase to histidine closely mirrored the histidine responsiveness of an identical hutT fusion to promoterless lacZ. To demonstrate the effectiveness of the strategy, the activity of hutT was monitored on sugar beet seedlings. Low levels of transcriptional activity were detected in the phyllosphere, rhizosphere and in plant extract, but not in vermiculite devoid of seedlings. The histidine concentration in the rhizosphere was estimated to be 0.6 μg ml−1. The ecological significance of the hut locus was examined by competing a hutT deletion mutant against the wild-type during colonization of sugar beet seedlings. No impact on competitive fitness was detected, suggesting that the ability to utilize plant-derived histidine is not essential for bacterial colonization.

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