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Having the capacity to detect and identify pathogens that can be employed in a bioterror attack is critical from both a public health and defence perspective. Immunodiagnostic assays are useful tools for enhancing such detection capabilities. In order to develop an immunodiagnostic assay for the detection of Francisella tularensis, a murine monoclonal antibody (MAb) was developed, using the live vaccine strain (LVS) of F. tularensis as the inoculating antigen. A single MAb, F94G2-1, which is specific for the lipopolysaccharide (LPS) of this bacterium was developed and characterized. An indirect ELISA using purified LPS was effective in determining reactivity of the MAb against its target. An immunodotblot and a manually printed antigen microarray were also tested as suitable detection methods. Both assays showed that MAb F94G2-1 has excellent specificity for F. tularensis LPS and demonstrate the utility of using the same MAb in a variety of immunodiagnostic applications.

Relationships between feeding status and the biliary concentrations of biliverdin and metabolites of polycyclic aromatic hydrocarbons (PAH) have been investigated in plaice (Pleuronectes platessa) from the Firth of Clyde, Scotland. Plaice were caught at three times of the day, and kept, without feeding, in tanks for up to 24h. The mean concentrations of biliary PAH metabolites 2-OH naphthalene, 1-OH pyrene and 3-OH benzo-[a]-pyrene (3-OH B[a]P) were found to increase slightly over a 24h non-feeding period (only significant for 3-OH benzo-[a]-pyrene). This effect was not observed for mean biliary concentrations of 1-OH phenanthrene. During this period of starvation, bile volume, total amounts of all PAH metabolites in the gall bladder, and biliary biliverdin concentrations all significantly increased. No significant relationships (P>0.05) were found between indicators of feeding status and individual PAH metabolite concentrations, confusing the rationale for normalisation of data to account for differences in feeding status between fish. Normalisation of PAH metabolite concentrations to biliverdin concentrations did not consistently reduce the variance of the metabolite data for fish sampled after the same starvation period. However, the variation between mean metabolite concentrations of fish suffering different starvation periods was reduced by biliverdin normalisation for most of the metabolites measured. It is therefore recommended that biliary PAH metabolite data should be presented as raw concentrations, except in cases where there may be significant differences in feeding status between groups of fish. In such instances biliverdin normalised data should also be reported and observational guides such as bile volume and stomach contents may aid in the interpretation of data.

The protein FinO represses F-plasmid conjugative transfer by facilitating interactions between the mRNA of the major F-plasmid transcriptional activator, TraJ, and an antisense RNA, FinP. FinO is known to bind stem-loop structures in both FinP and traJ RNAs; however, the mechanism by which FinO facilitates sense-antisense pairing is poorly understood. Here we show that FinO acts as an RNA chaperone to promote strand exchange and duplexing between minimal RNA targets derived from FinP. This strongly suggests that FinO may function to destabilize internal secondary structures within FinP and traJ RNAs that would otherwise act as a kinetic trap to sense-antisense pairing. The energy for FinO-catalyzed base-pair destabilization does not arise from ATP hydrolysis but appears to be supplied directly from FinO RNA binding free energy. An analysis of the activities of mutants that are specifically deficient in strand exchange but not RNA-binding activity demonstrates that strand exchange is essential to the ability of FinO to mediate sense-antisense RNA recognition, and that this function also plays a role in repression of conjugation in vivo.

F-like plasmid transfer is mediated by the FinOP fertility inhibition system. Expression of the F positive regulatory protein, TraJ, is controlled by the action of the antisense RNA, FinP, and the RNA-binding protein FinO. FinO binds to and protects FinP from degradation and promotes duplex formation between FinP and traJ mRNA, leading to repression of both traJ expression and conjugative F transfer. FinP antisense RNA secondary structure is composed of two stem-loops separated by a 4-base single-stranded spacer and flanked on each side by single-stranded tails. Here we show that disruption of the expected Watson-Crick base pairing between the loops of FinP stem-loop I and its cognate RNA binding partner, traJ mRNA stem-loop Ic, led to a moderate reduction in the rate of duplex formation in vitro. In vivo, alterations of the anti-ribosome binding site region in the loop of FinP stem-loop I reduced the ability of the mutant FinP to mediate fertility inhibition and to inhibit TraJ expression when expressed in trans at an elevated copy number. Alterations of intermolecular complementarity between the stems of these RNAs reduced the rate of duplex formation. Our results suggest that successful interaction between stem-loop I of FinP and stem-loop Ic of traJ mRNA requires that base pairing must proceed from an initial loop-loop interaction through the top portion of the stems for stable duplex formation to occur.

The Cpx (conjugative plasmid expression) stress response of Escherichia coli is induced in response to extracytoplasmic signals generated in the cell envelope, such as misfolded proteins in the periplasm. Detection of stress is mediated by the membrane-bound histidine kinase, CpxA. Signaling of the response regulator CpxR by activated CpxA results in the expression of several factors required for responding to cell envelope stress. CpxA was originally thought to be required for the expression of the positive regulator of the F plasmid transfer (tra) operon, TraJ. It was later determined that constitutive gain-of-function mutations in cpxA led to activation of the Cpx envelope stress response and decreased TraJ expression. In order to determine the nature of the downregulation of TraJ, the level of expression of TraJ, TraM, and TraY, the F-encoded regulatory proteins of the F tra region, was determined both in a cpxA* background and in a wild-type background in which the Cpx stress response was induced by overexpression of the outer membrane lipoprotein, NlpE. Our results suggest that TraJ downregulation is controlled by a posttranscriptional mechanism that operates in the cytoplasm in response to upregulation of the Cpx stress response by both the cpxA* gain-of-function mutation and the overexpression of NlpE.