Sialic acid utilization by the soil bacterium Corynebacterium glutamicum

The ability to use the sialic acid, N-acetylneuraminic acid, Neu5Ac, as a nutrient has been characterized in a number of bacteria, most of which are human pathogens that encounter this molecule because of its presence on mucosal surfaces. The soil bacterium Corynebacterium glutamicum also has a full complement of genes for sialic acid catabolism, and we demonstrate that it can use Neu5Ac as a sole source of carbon and energy and isolate mutants with a much reduced growth lag on Neu5Ac. Disruption of the cg2937 gene, encoding a component of a predicted sialic acid-specific ABC transporter, results in a complete loss of growth of C. glutamicum on Neu5Ac and also a complete loss of [14C]-Neu5Ac uptake into cells. Uptake of [14C]-Neu5Ac is induced by pregrowth on Neu5Ac, but the additional presence of glucose prevents this induction. The demonstration that a member of the Actinobacteria can transport and catabolize Neu5Ac efficiently suggests that sialic acid metabolism has a physiological role in the soil environment.