Adaptive radiation of Pseudomonas fluorescens SBW25 in experimental microcosms provides an understanding of the evolutionary ecology and molecular biology of A-L interface biofilm formation

Pseudomonas fluorescens Pf0-1 is one of the model organisms for biofilm research. Our previous transposon mutagenesis study suggested a requirement for the de novo purine nucleotide biosynthesis pathway for biofilm formation by this organism. This study was performed to verify that observation and investigate the basis for the defects in biofilm formation shown by purine biosynthesis mutants. Constructing deletion mutations in 8 genes in this pathway, we found that they all showed reductions in biofilm formation that could be partly or completely restored by nucleotide supplementation or genetic complementation. We demonstrated that, despite a reduction in biofilm formation, more viable mutant cells were recovered from the surface-attached population than from the planktonic phase under conditions of purine deprivation. Analyses using scanning electron microscopy revealed that the surface-attached mutant cells were 25~30% shorter in length than WT, which partly explains the reduced biomass in the mutant biofilms. The laser diffraction particle analyses confirmed this finding, and further indicated that the WT biofilm cells were smaller than their planktonic counterparts. The defects in biofilm formation and reductions in cell size shown by the mutants were fully recovered upon adenine or hypoxanthine supplementation, indicating that the purine shortages caused reductions in cell size. Our results are consistent with surface attachment serving as a survival strategy during nutrient deprivation, and indicate that changes in the cell size may be a natural response of P. fluorescens to growth on a surface. Finally, cell sizes in WT biofilms became slightly smaller in the presence of exogenous adenine than in its absence. Our findings suggest that purine nucleotides or related metabolites may influence the regulation of cell size in this bacterium.

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-5-0581 ◽

2007 ◽

Vol 20 (5) ◽

pp. 581-588 ◽

Cited By ~ 21

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.

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Contribution of the Pseudomonas fluorescens MFE01 Type VI Secretion System to Biofilm Formation

PLoS ONE ◽

10.1371/journal.pone.0170770 ◽

2017 ◽

Vol 12 (1) ◽

pp. e0170770 ◽

Cited By ~ 22

Author(s):

Mathias Gallique ◽

Victorien Decoin ◽

Corinne Barbey ◽

Thibaut Rosay ◽

Marc G. J. Feuilloley ◽

...

Keyword(s):

Pseudomonas Fluorescens ◽

Biofilm Formation ◽

Secretion System ◽

Type Vi Secretion System ◽

Type Vi Secretion

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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 ◽

10.1099/mic.0.28731-0 ◽

2006 ◽

Vol 152 (6) ◽

pp. 1867-1875 ◽

Cited By ~ 31

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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