Investigation of an Uncharacterized Aeromonas Protein involved in Host Colonization
The gut microbiota consists of a diverse community of microbes, living within the digestive tracts of humans, animals, and insects. While some microbes can cause infectious diseases, other microbes are vital for the development and physiology of the host. Although it is known that microbes affect host health and development, the colonization dynamics of these microbes are still unknown. In the Guillemin lab, we study these host-microbe interactions using zebrafish as a model organism to understand how microbes colonize the host gut. Aeromonas is a normal bacterial resident of the zebrafish gut that we recently discovered produces an uncharacterized double cache domain containing protein ZOR0001_03237 (3237). This protein, 3237, affects the colonization of Aeromonas in zebrafish by decreasing the rate of colonization. To further explore how 3237 could be involved in colonization, we investigated the predicted structure for clues. Based on sequence, 3237 is hypothesized to have a periplasmic sensing region that contains tandem cache domains, a transmembrane region and a cytoplasmic diguanylate cyclase signaling domain. This study focused on identifying ligands that bind to the periplasmic region of 3237. A thermal shift assay was utilized to screen over 200 possible ligands. The amino acids proline, valine and isoleucine were identified to bind to the periplasmic region and increase the melting temperature of 3237 12-19 degrees Celsius. In addition, Aeromonas strains that have loss-of-function mutations in 3237 show increased swimming behavior over wild type in soft agar swim plates and have decreased growth in defined media. These phenotypes suggest that 3237 is involved in aiding Aeromonas to sense environmental cues and dictate motility. The identification of specific amino acid ligands and preliminary characterization of Aeromonas phenotypes when lacking 3237 have provided new insight on how this novel protein might affect colonization of the zebrafish gut.