AP contributed to study design and coordination, helped to draft selleck chemicals llc the manuscript and critically revised its final version. All authors read and approved the final manuscript.”
“Background

Hfq is a ubiquitous and abundant bacterial protein which assembles into ~12 kDa ring-shaped homohexamers that resemble those formed by the Sm proteins of the eukaryotic splicing complex [1, 2]. It was originally identified in the model bacterium Escherichia coli as a host factor essential for Qβ RNA bacteriophage replication [3]. In uninfected bacteria Hfq retains the ability to bind many mRNAs and trans-acting antisense small non-coding regulatory RNAs (sRNAs), thereby influencing, selleck chemical directly or indirectly, on the stability and/or translation of functionally diverse RNA molecules [4–6]. This variety of interactions place Hfq at a crucial node in bacterial post-transcriptional regulatory networks underlying a wide range of cellular processes and pathways [6–8]. Consequently, mutations in the hfq gene were early

observed to have a severe impact on bacterial physiology resulting in alterations in growth rate, cell morphology and tolerance to harsh environments [9]. In several enterobacteria and other facultative intracellular mammal pathogens these deficiencies ultimately compromise virulence traits such as motility, host invasion or growth/survival in the intracellular niche [10–16]. The virulence-related phenotypes of the hfq mutants have Linsitinib price been shown to be largely dependent on the deregulation of the membrane homeostasis and RpoS- or RpoE-mediated stress response pathways, which have been reported to involve the activity of sRNAs in Edoxaban some of these pathogenic bacteria [15, 17–19]. The α subdivision of the proteobacteria includes diverse species which share the capacity to establish a variety of long-term interactions with higher eukaryotes [20]. The pleiotropic phenotype conferred by hfq mutations is also common to all α-proteobacteria representatives in which the Hfq function has been genetically addressed. For example, in Brucella

spp. the Hfq defective mutants showed osmosensitivity, reduction in the fitness of long-term cultures and impaired survival into host macrophages, further supporting the relevant role of this protein in the establishment and maintenance of chronic intracellular infections [21, 22]. Besides its general contribution to stress adaptation Hfq has been also shown to influence the nitrogen fixation process in free-living (Rhodobacter capsulatus) and symbiotic (Azorhizobium caulinodans and Rhizobium leguminosarum bv. viciae) α-proteobacterial diazotrophs [23–26]. In these microorganisms Hfq acts as a positive post-transcriptional regulator of nifA, the gene encoding the major transcriptional activator of the genes coding for the nitrogenase complex. However, in contrast to the situation in A.