Essential Role of the Iron-Regulated Outer Membrane Receptor FauA in Alcaligin Siderophore-Mediated Iron Uptake in Bordetella Species

Phenotypic analysis using heterologous host systems localized putative Bordetella pertussis ferric alcaligin transport genes and Fur-binding sequences to a 3.8-kb genetic region downstream from the alcR regulator gene. Nucleotide sequencing identified a TonB-dependent receptor family homolog gene, fauA, predicted to encode a polypeptide with high amino acid sequence similarity with known bacterial ferric siderophore receptors. In Escherichia coli, the fauA genes of both B. pertussis and Bordetella bronchiseptica directed the production of a 79-kDa polypeptide, approximating the predicted size of the mature FauA protein. B. bronchiseptica fauA insertion mutant BRM17 was unable to utilize ferric alcaligin, and in complementation analyses ferric alcaligin utilization was restored to this mutant by supplying the wild-type fauA gene in trans. Mutant BRM18, carrying a nonpolar in-frame fauA deletion mutation, was defective in ferric alcaligin utilization and 55Fe-ferric alcaligin uptake and no longer produced a 79-kDa iron-regulated outer membrane protein. In complementation analyses, BRM18 merodiploids bearing the wild-type fauA gene in trans regained ferric alcaligin siderophore transport and utilization functions and produced the 79-kDa protein. Analysis of a plasmid-borne fauA-lacZ operon fusion confirmed that fauA is subject to iron regulation at the transcriptional level and that cis-acting transcriptional control elements mediating fauA iron repressibility reside within the 3.8-kb PstI fauA DNA region. Moreover, expression of the fauA-lacZ fusion gene under iron starvation conditions was shown to be alcR dependent. FauA is a 79-kDa iron-regulated outer membrane receptor protein required for transport and utilization of ferric alcaligin siderophore complexes by Bordetella species. Originally published Journal of Bacteriology, Vol. 181, No. 19, Oct 199

Assessing Working Memory in Mild Cognitive Impairment with Serial Order Recall.

BACKGROUND: Working memory (WM) is often assessed with serial order tests such as repeating digits backward. In prior dementia research using the Backward Digit Span Test (BDT), only aggregate test performance was examined. OBJECTIVE: The current research tallied primacy/recency effects, out-of-sequence transposition errors, perseverations, and omissions to assess WM deficits in patients with mild cognitive impairment (MCI). METHODS: Memory clinic patients (n = 66) were classified into three groups: single domain amnestic MCI (aMCI), combined mixed domain/dysexecutive MCI (mixed/dys MCI), and non-MCI where patients did not meet criteria for MCI. Serial order/WM ability was assessed by asking participants to repeat 7 trials of five digits backwards. Serial order position accuracy, transposition errors, perseverations, and omission errors were tallied. RESULTS: A 3 (group)×5 (serial position) repeated measures ANOVA yielded a significant group×trial interaction. Follow-up analyses found attenuation of the recency effect for mixed/dys MCI patients. Mixed/dys MCI patients scored lower than non-MCI patients for serial position 3 (p \u3c 0.003) serial position 4 (p \u3c 0.002); and lower than both group for serial position 5 (recency; p \u3c 0.002). Mixed/dys MCI patients also produced more transposition errors than both groups (p \u3c 0.010); and more omissions (p \u3c 0.020), and perseverations errors (p \u3c 0.018) than non-MCI patients. CONCLUSIONS: The attenuation of a recency effect using serial order parameters obtained from the BDT may provide a useful operational definition as well as additional diagnostic information regarding working memory deficits in MCI

Bordetella Interspecies Allelic Variation in AlcR Inducer Requirements: Identification of a Critical Determinant of AlcR Inducer Responsiveness and Construction of an alcR(Con) Mutant Allele

Previous studies established the critical roles of AlcR and alcaligin inducer in positive regulation of alcaligin siderophore biosynthesis and transport genes in Bordetella pertussis and Bordetella bronchiseptica. Transcriptional analyses using plasmid-borne alcR genes of B. pertussis UT25 and B. bronchiseptica B013N to complement the alcR defect of B. bronchiseptica strain BRM13 (ΔalcR1 alcA::mini-Tn5 lacZ1) revealed interspecies differences in AlcR inducer requirements for activation of alcABCDER operon transcription. Whereas the B. pertussis UT25 AlcR protein retained strong inducer dependence when produced from multicopy plasmids, B. bronchiseptica B013N alcR partially suppressed the alcaligin requirement for transcriptional activation. Functional analysis of AlcR chimeras produced by interspecies domain swapping and interspecies reciprocal site-specific mutagenesis determined that the phenotypic difference in AlcR inducer dependence was due to a single amino acid difference within the proposed inducer-binding and multimerization domain of AlcR. Structural predictions guided the design of a mutant AlcR protein with a single amino acid substitution at this critical position, AlcR(S103T), that was fully constitutive not only when produced from multicopy plasmids but also at a single-copy gene dosage. These results indicate that AlcR residue 103 affects a critical determinant of alcaligin inducer dependence of AlcR-mediated transcriptional activation. The alcR(S103T) mutant allele is the first alcR(Con) mutant allele identified