PhD highlights: Christian Ramos

Title: Roles played by Hfq-like RNA chaperones and sRNAs on the virulence of Burkholderia cepacia complex bacteria

Abstract:Burkholderia cenocepacia J2315 is a multi-drug resistant opportunistic Human pathogen with a large and complex genome, able to cause life-threatening infections (Sousa et al., 2011). Hfq-like RNA chaperones and small non-coding regulatory RNAs (sRNAs) have been shown to play important roles in the virulence of a limited number of bacterial pathogens. In these pathogens, no information was available on neither RNA chaperones nor sRNAs. Therefore, we aimed to characterized these proteins and identify sRNAs playing a role on virulence.

The B. cenocepacia J2315 is almost unique among bacterial pathogens by having the hfqand hfq2 genes, encoding two RNA chaperones (Sousa et al., 2010), which were both found as required for stress resistance and full virulence towards the nematodeCaenorhabditis elegans. These genes are differentially expressed, with the levels of hfqmRNA depending on sigma-70 and the levels of hfq2 mRNA depending on the CepR quorum-sensing regulator (Ramos et al., 2011). The molecular characterization of h2cR revealed that low levels of hfq2 mRNA in the exponential phase are due to negative regulatory action of the sigma-70-dependent cis-encoded h2cR sRNA (Ramos et al., 2012), whereas the low levels of hfq mRNA at the stationary phase are due to the trans-encoded Hfq2-dependent MtvR sRNA (Ramos et al., submitted). The h2cR, as well as twenty-four additional sRNAs (Bcj1-Bcj24), and the MtvR sRNA were identified based on co-purification experiments with Hfq (Ramos et. al, 2013) or Hfq2, respectively. The functional and molecular characterization of MtvR revealed a major role as a global regulator, involved among other important traits, in antibiotic resistance (Ramos et al., submitted).

The identification and functional characterization of sRNAs from a Burkholderia cepaciacomplex (Bcc) organism added a new layer of knowledge and useful tools for the study of post-transcriptional regulation in Bcc organisms (Fig. 1). Ongoing and future work is focused on the detailed functional and molecular characterization of virulence-associated sRNAs and their possible exploitation as novel therapeutic molecules.



Professor Jorge H. Leitão, Professor Leonilde M. Moreira, Dr. Jörg Becker (IGC), Dr. Silvia Sousa, André Grilo, Paulo Costa and Joana Feliciano, who made important contributes for the accomplishment of the research project are acknowledged. Financial support from the Calouste Gulbenkian Foundation, through a Doctoral Scholarship and the Foundation for Science and Technology, Portugal (contracts PTDC/EBB-BIO/098352/2008 and PTDC/BIA-MIC/119091/2010) is also acknowledged.


Ramos CG, Sousa SA, Grilo AM, Feliciano JR, Leitão JH. (2011), The second RNA chaperone Hfq2, is also required for survival to stress and the full virulence ofBurkholderia cenocepacia J2315. J. Bacteriol. 193:1515-1526.

Ramos CG, Da Costa PJP, Döring G, Leitão JH. (2012), The novel cis-encoded small RNA h2cR is a negative regulator of hfq2 in Burkholderia cenocepacia. PLoS ONE7:e47896.

Ramos CG, Grilo AM, da Costa PJP, Leitão JH. (2013), Experimental identification of small non-coding regulatory RNAs in the opportunistic human pathogenBurkholderia cenocepacia J2315. Genomics 101:139-148.

Sousa SA, Ramos CG, Leitão, JH. (2010), The hfq gene is required for stress resistance and full virulence of Burkholderia cepacia to the nematode Caenorhabditis elegans. Microbiology 156: 896 – 908.

Sousa SA, Ramos CG, Moreira LM, Leitão JH. (2011), Burkholderia cepaciacomplex: emerging multi-host pathogens equipped with a wide range of virulence factors and determinants. Int. J. Microbiol. 2011 (doi:10.1155/2011/607575).

PhD Degree: Biotechnology; Year of conlusion: 2011

Institution: Instituto Superior Técnico, Universidade Técnica de Lisboa

Supervision: Jorge H. Leitão and Leonilde M. Moreira

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