realized in has disposition at some time artificially mutated Brucella macrophage - Brucella interaction attenuated disposition B. abortus pheA mutant MUTATION: The product of pheA gene is specifically dedicated to the biosynthesis of phenylalanine. The B. abortus pheA mutant with mini-Tn5 disruption displays nutritional defects in vitro. Experimental findings with the B abortus ilvD, trpB, and pheA mutants suggest that tryptophan and phenylalanine are available to the brucellae in their intracellular niche but that other amino acids (eg, leucine, isoleucine, or valine) are not. The pheA::miniTn5 mutant displayed attenuation in macrophages but not in mice [Alcantara et al., 2004]. See. PMID:15271960