The aim of this work is the taxonomic characterization of three biosurfactant-producing bacterial isolates from the Churince system at Cuatro Ciénegas Basin (CCB) in the Mexican State of Coahuila, and the
study of the possible role of biosurfactant production in their ecology and evolution. We determined that
these isolates belong to aPseudomonas koreensislineage endemic to CCB, using standard taxonomical
techniques, phylogenetic analysis of three chromosomal loci and phenotypic characterization. This new
lineage has the distinct capacity to produce a biosurfactant when compared with previously reported
P. koreensisisolates recovered from agricultural soils in Korea. We present evidence suggesting that
the biosurfactant secreted by CCBP. koreensisstrains is involved in their ability to compete with a CCB
Exiguobacterium aurantiacumstrain (m5-66) used as a model organism in competition experiments. Furthermore, the ethyl acetate extract of culture supernatant of CCBP. koreensisstrains results in growth
inhibition not only ofE. aurantiacumm5-66, but also of aBacillus subtilistype strain (ATCC6633). Based
on these results we propose that the production of biosurfactant could be of ecological importance and
could play a role in the separation of theP. koreensisCCB lineage.