Impact of Facultative Bacteria on the Metabolic Function of an Obligate Insect-Bacterial Symbiosis

Abstract

Although microbial colonization of the internal tissues of animals generally causes septicemia and death, various animals are persistently associated with benign or beneficial microorganisms in their blood or internal organs. The metabolic consequences of these persistent associations for the animal host are largely unknown. Our research on the facultative bacterium Hamiltonella , localized primarily to the hemolymph of pea aphids, demonstrated that although Hamiltonella imposed no major reconfiguration of the aphid metabolome, it did alter the metabolic relations between the aphid and its obligate intracellular symbiont, Buchnera . Specifically, Buchnera produced more histidine in Hamiltonella- positive aphids to support both Hamiltonella demand for histidine and Hamiltonella -induced increase in host demand. This study demonstrates how microorganisms associated with internal tissues of animals can influence specific aspects of metabolic interactions between the animal host and co-occurring microorganisms.