To identify variants correlated with the ability to grow axenically (ie in the absence of prey organisms) we resequenced mutant Dictyostelium discoideum strains and compared them to their wild-type parent. We identified a single locus that is compromised in every mutant strain: most mutants carry short deletions that result in frameshifts, but we also found nonsense and missense SNPs and an in-frame inversion that leads to an 8 amino-acid substitution. Deletion of the gene enables slow axenic growth, confirming that a single mutation in this gene, axeB, is sufficient to confer the phenotype, but that further mutations are necessary for the fast growth phenotype of standard laboratory strains.
Less...