Poster abstracts

Poster number 57 submitted by Theresa Rogers

tRNA-like small RNA in Bacillus cereus

Theresa E. Rogers (Department of Microbiology, The Ohio State University), Sandro Ataide (Department of Microbiology, The Ohio State University), Michael Ibba (Department of Microbiology, The Ohio State University)

Abstract:
tRNA^Other is a tRNA-like small RNA of unknown function in Bacillus cereus that is aminoacylated in vitro by the concerted effort of unrelated class I and II lysyl-tRNA synthetases (LysRS). In vivo analyses revealed that class I LysRS and tRNA^Other were mainly produced during stationary phase, while class II LysRS was produced in both exponential and stationary phases. tRNA^Other could not be detected in polysomes isolated from cells collected during exponential or early stationary phases, indicating a function beyond translation. tRNA^Other is encoded within a pathogenicity island together with several putative virulence factors. To investigate the role of tRNA^Other in B. cereus, we deleted the corresponding gene and screened for changes in growth phenotype compared to wild-type. Deletion of tRNA^Other was not deleterious, and growth in rich media and ability to sporulate were virtually unchanged. Changes were observed in stationary phase, such as de-regulation of the production of a bacteriocin-like inhibitory susbstance and increased responsiveness to various germinants. Extensive screening for growth phenotype changes (~1900 conditions) was carried out by performing phenotypic microarray analyses (BIOLOG, Inc.). These studies revealed significant changes; B. cereus ΔtRNA^Other gained resistance to several antibiotics, but also acquired sensitivity to a number of compounds including antibiotics, cationic detergents and positively charged ionophores. Changes in gene expression between the wild-type and ΔtRNA^Other strains were explored by transcriptional microarrays. Surprisingly, almost no changes in transcript levels were observed between wild-type and ΔtRNA^Other strains collected during stationary phase. In contrast, many significant transcript level changes were observed between wild-type and ΔtRNA^Other strains collected during mid-exponential growth. Among these, changes were observed for several transcriptional regulators, ABC transporters, and genes involved in sporulation and germination. The function of tRNA^Other as a regulatory RNA is currently being investigated.

Keywords: tRNA, small RNA, LysRS