title: Kin discrimination between sympatric Bacillus subtilis isolates.
abstract: Kin discrimination, broadly defined as differential treatment of conspecifics according to their relatedness, could help biological systems direct cooperative behavior toward their relatives. Here we investigated the ability of the soil bacterium Bacillus subtilis to discriminate kin from nonkin in the context of swarming, a cooperative multicellular behavior. We tested a collection of sympatric conspecifics from soil in pairwise combinations and found that despite their history of coexistence, the vast majority formed distinct boundaries when the swarms met. Some swarms did merge, and most interestingly, this behavior was only seen in the most highly related strain pairs. Overall the swarm interaction phenotype strongly correlated with phylogenetic relatedness, indicative of kin discrimination. Using a subset of strains, we examined cocolonization patterns on plant roots. Pairs of kin strains were able to cocolonize roots and formed a mixed-strain biofilm. In contrast, inoculating roots with pairs of nonkin strains resulted in biofilms consisting primarily of one strain, suggestive of an antagonistic interaction among nonkin strains. This study firmly establishes kin discrimination in a bacterial multicellular setting and suggests its potential effect on ecological interactions.
authors.affiliation: Department of Microbiology and Immunobiology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia;
authors.forename: Polonca
authors.initials: P
authors.lastname: Stefanic
authors.affiliation: Department of Microbiology and Immunobiology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia;
authors.forename: Barbara
authors.initials: B
authors.lastname: Kraigher
authors.affiliation: Harvard Medical School, Boston, MA 02115.
authors.forename: Nicholas Anthony
authors.initials: NA
authors.lastname: Lyons
authors.affiliation: Harvard Medical School, Boston, MA 02115.
authors.forename: Roberto
authors.initials: R
authors.lastname: Kolter
authors.affiliation: Department of Microbiology and Immunobiology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; ines.mandic@bf.uni-lj.si.
authors.forename: Ines
authors.initials: I
authors.lastname: Mandic-Mulec
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000502:physiology*; D001483:Base Sequence; D018441:Biofilms; D016000:Cluster Analysis; D017931:DNA Primers / Q000235:genetics; D056265:Microbial Interactions / Q000502:physiology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D017931:DNA Primers
keywords: antagonism; biofilm; kin recognition; social evolution; swarming