Moraxella catarrhalis Expresses an Unusual Hfq Protein

Department of Microbiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9048, USA.
Infection and immunity (Impact Factor: 3.73). 07/2008; 76(6):2520-30. DOI: 10.1128/IAI.01652-07
Source: PubMed


The Hfq protein is recognized as a global regulatory molecule that facilitates certain RNA-RNA interactions in bacteria. BLAST
analysis identified a 630-nucleotide open reading frame in the genome of Moraxella catarrhalis ATCC 43617 that was highly conserved among M. catarrhalis strains and which encoded a predicted protein with significant homology to the Hfq protein of Escherichia coli. This protein, containing 210 amino acids, was more than twice as large as the Hfq proteins previously described for other
bacteria. The C-terminal half of the M. catarrhalis Hfq protein was very hydrophilic and contained two different types of amino acid repeats. A mutation in the M. catarrhalis hfq gene affected both the growth rate of this organism and its sensitivity to at least two different types of stress in vitro.
Provision of the wild-type M. catarrhalis hfq gene in trans eliminated these phenotypic differences in the hfq mutant. This M. catarrhalis hfq mutant exhibited altered expression of some cell envelope proteins relative to the wild-type parent strain and also had a
growth advantage in a continuous flow biofilm system. The presence of the wild-type M. catarrhalis hfq gene in trans in an E. coli hfq mutant fully reversed the modest growth deficiency of this E. coli mutant and partially reversed the stress sensitivity of this E. coli mutant to methyl viologen. The use of an electrophoretic mobility shift assay showed that this M. catarrhalis Hfq protein could bind RNA derived from a gene whose expression was altered in the M. catarrhalis hfq mutant.

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Available from: Ahmed Attia
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    • "Attia et al. demonstrated a growth advantage for a Moraxella catarrhalis hfq mutant over the wild-type in a continuous flow biofilm system. The authors suggest this phenotype results from altered gene expression in the Δhfq background leading to changes in the overall outer membrane architecture [53]. In accordance with this hypothesis, Meibom et al. found expression of an outer membrane protein (FTL_0535) and several Type IV pili-associated proteins (FTL_0797, FTL_0798, and FTL_0827) upregulated in a F. tularensis LVS hfq mutant strain [13]. "
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    ABSTRACT: The RNA-binding protein Hfq is recognized as an important regulatory factor in a variety of cellular processes, including stress resistance and pathogenesis. Hfq has been shown in several bacteria to interact with small regulatory RNAs and act as a post-transcriptional regulator of mRNA stability and translation. Here we examined the impact of Hfq on growth, stress tolerance, and gene expression in the intracellular pathogen Francisella novicida. We present evidence of Hfq involvement in the ability of F. novicida to tolerate several cellular stresses, including heat-shock and oxidative stresses, and alterations in hfq gene expression under these conditions. Furthermore, expression of numerous genes, including several associated with virulence, is altered in a hfq mutant strain suggesting they are regulated directly or indirectly by Hfq. Strikingly, we observed a delayed entry into stationary phase and increased biofilm formation in the hfq mutant. Together, these data demonstrate a critical role for Hfq in F. novicida growth and survival.
    Preview · Article · May 2011 · PLoS ONE
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    • "Because the hfq mutant grew slower in DMEM (g, WT ~ 25 min and g, hfq ~ 60 min) than in LB (g, WT ~ 25 min and g, hfq ~ 40 min), LB medium was used for cell growth in the experiments below unless stated otherwise. The decreased growth phenotype of the hfq mutant, shared by other bacterial pathogens (Ding et al., 2004; Sittka et al., 2007; Attia et al., 2008), might be due to drastically increased energy consumption caused by elevated LEE expression and subsequent protein secretion since a hfq ler double mutant, devoid of LEE expression, exhibited similar growth as an E. coli K-12 hfq mutant strain (data not shown). "
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