Intraspecific diversity in biofilm communities is associated with enhanced
survival and growth of the individual biofilm populations. In here, we
assess if this apparent cooperative behavior still holds as the number of
different strains in a biofilm increases. Using E. coli as a model organism,
the influence of intraspecific diversity in biofilm populations composed of
up to six different E. coli strains, was assessed. Biofilm quantification was
evaluated by crystal violet (CV) staining and colony forming units (CFU)
counts. In general, with the increasing number of strains in a biofilm, an
increase in cell counts and a decrease in matrix production was
observed. This observation was confirmed by cluster analysis that
indicated that after 24h of biofilm formation the best model, according to
the Bayesian information criterion (BIC), consisted of three clusters that
grouped together biofilms with an equal number of strains. It hence
appears that increased genotypic diversity in a biofilm leads E. coli to
maximize the production of its offspring, in detriment of the production of
public goods (i.e. matrix components), that would be beneficial to all
strains individually and the consortium as a whole. Apart from the
ecological implications, these results can be explored in the area of
clinical biofilms, as a decrease in matrix production might render these
intraspecies biofilms more sensitive to antimicrobial agents
