Abstract
Most bacterial small RNAs (sRNAs) are post-transcriptional regulators involved in adaptive responses, controlling gene expression by modulating translation or stability of their target mRNAs often in concert with the RNA chaperone Hfq. Neisseria meningitides, the leading cause of bacterial meningitis, is able to adapt to different host niches during human infection. However, only a few sRNAs and their functions have been fully described to date. Recently, transcriptional expression profiling of N. meningitides in human blood ex vivo revealed 91 differentially expressed putative sRNAs. Here we expanded this analysis by performing a global transcriptome study after exposure of N. meningitides to physiologically relevant stress signals (e.g. heat shock, oxidative stress, iron and carbon source limitation). and we identified putative sRNAs that were differentially expressed in vitro. A set of 98 putative sRNAs was obtained by analyzing transcriptome data and 8 new sRNAs were validated, both by Northern blot and by primer extension techniques. Deletion of selected sRNAs caused attenuation of N. meningitides infection in the in vivo infant rat model, leading to the identification of the first sRNAs influencing meningococcal bacteremia. Further analysis indicated that one of the sRNAs affecting bacteremia responded to carbon source availability through repression by a GntR-like transcriptional regulator. Both the sRNA and the GntR-like regulator are implicated in the control of gene expression from a common network involved in energy metabolism.
Highlights
The essential role of small RNA transcripts for the regulation of many biological functions, especially gene expression, is well-established for many organisms
Regulatory small RNA (sRNA) transcripts are a heterogeneous group of molecules, which modulate a wide range of physiological processes through different mechanisms
The cultures were added to an equal volume of frozen medium to bring the temperature immediately to 4°C and cells were harvested by centrifugation at 3000 rpm for 20 min for RNA extraction
Summary
The essential role of small RNA (sRNA) transcripts for the regulation of many biological functions, especially gene expression, is well-established for many organisms. High-density array experiments together with a new bioinformatic tool named chipSAD have been employed in order to investigate differential transcriptional expression of Neisseria meningitidis in whole human blood [45]. This analysis revealed the presence of 91 differentially expressed putative sRNAs after incubation in human blood, six of which were successfully validated by 5’-3’ RACE, including NrrF [45]. We evaluated deletion mutants of 7 sRNAs in the in vivo infant rat model of bacteremia, identifying the first 4 sRNAs important for meningococcal fitness during infection
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