An Insight Into the Microbial Diversity and Expression of Cysteine Protease Inhibitors (Cystatin) in \u3ci\u3eRickettsia parkeri\u3c/i\u3e Infected \u3ci\u3eAmblyomma maculatum\u3c/i\u3e

Abstract

Amblyomma maculatum (Gulf Coast tick) is an emerging tick species of public health significance in United States. It is a competent vector of Rickettsia parkeri, an etiological agent of a human rickettsiosis. In this study, we investigated the spotted fever group of rickettsial diversity in A. maculatum based on rickettsial ompA gene PCR. Our results showed A. maculatum harbors R. parkeri, R. amblyommii, and R. endosymbiont of A. maculatum. While only R. parkeri was detected in female salivary glands which suggest its ability to traffic from midgut to salivary glands via hemocoel. The presence of R. parkeri was further confirmed by probe based qPCR assay. We found R. parkeri infection rate ranged 12-40% in field collected ticks. We also provided evidence of R. parkeri infection transovarially and transstadially transmitted in A. maculatum. We used a pyrosequencing approach to further study all possible bacterial diversity residing in field collected A. maculatum. The huge bacterial profiling in A. maculatum provided the basis of Amblyomma-bacterial interactions particularly in relation to R. parkeri. On the other side, we observed cystatins temporal transcriptional expression in A. maculatumacross the blood meal cycle and our finding suggested their importance during blood feeding. Further, we saw R. parkeri differentially regulates gene expressions of cystatins in A. maculatum, suggesting a possible role of cystatins in R. parkeri infection in ticks. This study encourages further study to assess the exact relationship of R. parkeri with bacterial diversity in A. maculatum and cystatins role during tick blood feeding and R. parkeri transmission. Link to doctoral dissertation - http://aquila.usm.edu/dissertations/1381