Novel iron-regulated and Fur-regulated small regulatory RNAs in Aggregatibacter actinomycetemcomitans

Department of Oral Biology, School of Dental Medicine, University at Buffalo, State University of New York, Buffalo, NY, USA  Department of Microbiology and Immunology, University at Buffalo, State University of New York, Buffalo, NY, USA  Witebsky Center for Microbial Pathogenesis and Immunology, The School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY, USA.
Molecular oral microbiology 10/2012; 27(5):327-49. DOI: 10.1111/j.2041-1014.2012.00645.x
Source: PubMed

ABSTRACT Iron can regulate biofilm formation via non-coding small RNA (sRNA). To determine if iron-regulated sRNAs are involved in biofilm formation by the periodontopathogen Aggregatibacter actinomycetemcomitans, total RNA was isolated from bacteria cultured with iron supplementation or chelation. Transcriptional analysis demonstrated that the expression of four sRNA molecules (JA01-JA04) identified by bioinformatics was significantly upregulated in iron-limited medium compared with iron-rich medium. A DNA fragment encoding each sRNA promoter was able to titrate Escherichia coli ferric uptake regulator (Fur) from a Fur-repressible reporter fusion in an iron uptake regulator titration assay. Cell lysates containing recombinant AaFur shifted the mobility of sRNA-specific DNAs in a gel shift assay. Potential targets of these sRNAs, determined in silico, included genes involved in biofilm formation. The A. actinomycetemcomitans overexpressing JA03 sRNA maintained a rough phenotype on agar, but no longer adhered to uncoated polystyrene or glass, although biofilm determinant gene expression was only modestly decreased. In summary, these sRNAs have the ability to modulate biofilm formation, but their functional target genes remain to be confirmed.

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    • "However there is a previous report of other iron-responsive sRNAs encoded by a Pasteurellaceae species. Work by Amarasinghe et al. reported the presence of four Fur-regulated sRNAs, JA01 through JA04, in Aggregatibacter actinomycetemcomitans (Aa) strain HK1651R [60]. BLAST analysis of these four sRNAs reveled that JA01 is only conserved among Aa strains. "
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    • "It is proposed that these ncRNAs could be interacting with biofilm-associated genes, including the flp fimbrial operon and genes associated with EPS, according to in silico models (Amarasinghe et al., 2012). So far the ability of these iron-regulated ncRNAs to modulate biofilm formation has been demonstrated, but their functional target genes remain to be elucidated (Amarasinghe et al., 2012). The ncRNAs are sometimes part of complex regulatory networks that finally induce biofilm formation by posttranscriptional control. "
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