The Fimbria Gene Cluster of Nonencapsulated Haemophilus influenzae

Abstract

The occurrence of fimbria gene clusters in nonencapsulatedHaemophilus influenzae strains from chronic bronchitis patients (n = 58), patients with acute otitis media (n = 13), and healthy carriers (n = 12) was determined by DNA hybridization and PCR, based on sequences of fimbriate H. influenzae type b. Although an average of 18% of all nonencapsulated strains had a fimbria gene cluster consisting ofhifA to hifE inserted in the chromosome betweenpurE and pepN, differences in the frequency of fimbria cluster-positive strains were observed, depending on the source of isolates. The compositions of the fimbria gene clusters of seven strains from chronic bronchitis patients and one strain from an otitis media patient were analyzed in more detail. After enrichment for fimbria expression, the promoter of the gene cluster contained 10 TA repeats (n = 2), leading to optimal positioning between the −10 and −35 promoter regions. The promoter regions of five fimbria-negative strains were sequenced; four were found to have nine TA repeats, and one had only four TA repeats. The protein sequence of three ganglioside GM1-specific HifA adhesins consisted of conserved regions intermingled with regions of sequence diversity.hifA appeared to be flanked by intergenic regions that varied between strains and contained both direct and inverted DNA repeats. Since noncoding DNA between hifA andpurE has not been found in H. influenzae type b, these DNA sequences are probably not essential for fimbria expression. An analysis of strains lacking the gene cluster revealed the presence of similar sequences in 13 of 15 strains from chronic bronchitis patients, 5 of 5 strains from otitis media patients, and 3 of 5 strains from healthy carriers. The lengths of these intergenic regions were the same for multiple isolates of strains obtained during persistent infections. The presence or absence and the composition of the fimbria gene cluster and other sequences between the flanking genespurE and pepN suggest that the fimbria gene cluster was originally contained on a mobile element.

Phylogeography and population structure of the biologically invasive phytopathogen Erwinia amylovora inferred using minisatellites

“…These two VNTRs on plasmid pEA29 were included in our study since the plasmid is virtually ubiquitous and since the different rate of evolution and different copy numbers between bacterial chromosomes and plasmids might harbour interesting additional information. Since variations in repeat numbers have previously been linked to phenotypic effects giving rise to selective advantages in H. influenzae (Hood et al, 1996;Geluk et al, 1998;Zaleski et al, 2005), possible phenotypic effects were evaluated also in the case of E. amylovora, however without obtaining any obvious result. Ten of the repeat regions with a repeat unit equal to or larger than 6 bp were tested by PCR on an initial set of 30 strains from diverse geographical origin (Table S1).…”

“…Variable number of tandem repeats have also been proposed to play a role in functional gene evolution by several modes of action. Increasing number of repeats in Shine-Dalgarno sequence can affect gene expression levels (Geluk et al, 1998). Within coding regions, a change in the number of repeats can disrupt the coding frame, resulting in altered length of protein product or change the three-dimensional structure of the gene product as shown in virulence genes of Haemophilus influenzae (Hood et al, 1996).…”

Molecular determinants of the pathogenesis of disease due to non-typable Haemophilus influenzae

“…hifA is transcribed in one direction, and hifB^hifE are transcribed divergently as a polycistronic transcript [89]. The organization of the pilus gene cluster is identical in type b and non-typable strains [90]. Interestingly, aspects of this general organization are similar to other chaperone/usher assembly systems, including location of the gene encoding the major pilus subunit at one end of the locus, the assembly genes within the center of the gene cluster, and the minor structural subunits downstream from these elements [91].…”

Molecular determinants of the pathogenesis of disease due to non-typableHaemophilus influenzae

“…hifA is transcribed in one direction, and hifB – hifE are transcribed divergently as a polycistronic transcript [89]. The organization of the pilus gene cluster is identical in type b and non‐typable strains [90]. Interestingly, aspects of this general organization are similar to other chaperone/usher assembly systems, including location of the gene encoding the major pilus subunit at one end of the locus, the assembly genes within the center of the gene cluster, and the minor structural subunits downstream from these elements [91].…”