Studies of protein synthesis in the Bacteroidia

The Bacteroidia represent an important group of bacteria, abundant in intestinal tracts of mammals, including humans. Protein synthesis in the Bacteroidia differs substantially from that of well-studied bacteria, such as Escherichia coli. This project will uncover the unique way in which proteins are made in the Bacteroidia. The knowledge gained in this work may spur advances in biotechnology and medicine, particularly with respect to antibiotic development and human microbiome function. This project will also have broader impact by providing (i) research training for undergraduate and graduate students and (ii) summer research opportunities for local high school students (Columbus Public Schools). The textbook model of translation initiation in bacteria entails base pairing between a Shine-Dalgarno (SD) sequence of mRNA and the anti-SD (ASD) element of 16S rRNA. In Bacteroidia, virtually all mRNAs lack a SD sequence even though ribosomes of these organisms carry an intact ASD. Recent structural studies explain the basis of this apparent paradox. The 3’ tail of 16S rRNA is sequestered in a pocket formed by ribosomal proteins bS21, bS18, and bS6 on the 30S platform, an interaction which occludes the ASD. In the rare cases when SD elements are present, this interaction allows SD to be used for regulatory purposes (one such case is autoregulation of bS21 production), but generally it may enhance initiation on SD-less mRNAs in these organisms. Bacteroidia ribosomes also contain a novel protein, bL38, whose function remains unclear. This project aims to elucidate unique aspects of protein synthesis in the Bacteroidia, using Flavobacterium johnsoniae as a model. Specifically, the work will address: (1) how the platform pocket contributes to translation initiation in F. johnsoniae; (2) what role bL38 plays in F. johnsoniae, and (3) whether bS18-depleted ribosomes regulate protein synthesis in Bacteroides thetaiotaomicron, a member of order Bacteroidales. The results will provide fundamental insight on mechanisms of translation initiation, translation regulation, and ribosome assembly in diverse bacteria. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.