Commensal Complexity

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Science  17 Aug 2012:
Vol. 337, Issue 6096, pp. 779
DOI: 10.1126/science.337.6096.779-a

Strains of the Pseudomonas fluorescens group of commensal bacteria offer plants protection against pathogens through the production of antibiotics or the stimulation of plant resistance. The specific protections offered vary between strains, suggesting that genetic variation may underlie these differences. In order to investigate this, Loper et al. sequenced seven plant-associated strains that differed with respect to species, location on the plant, and mechanism of protection. A comparison of these genomes to three previously sequenced strains showed that whereas approximately 50% of the genes overlapped among all sequenced P. fluorescens strains, forming a core genome, the remaining genomic properties were highly variable and could be used to distinguish three pan-genomic complexes, with a high number of strain-specific elements and genes. Within the clades, specific genes and genetic elements tended to be found only within a select subset or single strains, some of which underlie phenotypic characteristics and may be involved in multitrophic interactions such as the production of secondary metabolites and components of the type III secretion system. The tremendous genetic diversity observed among these strains highlights how such investigations can help us better understand the complexities of species interactions.

PLoS Genet. 8, e1002784 (2012).

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