Simultaneous presence of two different copies of the 16S rRNA gene in Bartonella henselae

Abstract

Bartonella henselae is an emerging pathogen of increasing medical significance. Previous investigations have revealed two different 16S rRNA gene variants among B. henselae isolates, resulting in delineation of the B. henselae population into 16S RNA type I and type II isolates. While studying 191 B. henselae isolates by multi-locus sequence typing (MLST) we detected three isolates that could not be assigned to a distinct 16S RNA type upon direct sequencing because of ambiguous nucleotides in a distinct region of the 16S rRNA gene. Cloning and sequencing of the target region of the 16S rRNA gene suggested that these atypical isolates contained different 16S rRNA gene copies. Southern blot and hybridization experiments confirmed the presence of two different 16S RNA gene copies in each isolate. The isolates were further analysed by 16S RNA type-specific PCR, which assigned them to both 16S RNA types I and II. These results suggest that a small percentage of B. henselae isolates may harbour two different 16S rRNA gene copies. These isolates, which accounted for 1.6 % of the isolates in our study, have probably emerged by horizontal gene transfer. The implications of these findings for identification and genotyping studies on B. henselae are discussed. INTRODUCTIONBartonella henselae is the causative agent of a wide variety of infectious diseases including cat scratch disease, bacillary angiomatosis, prolonged fever ('fever of unknown origin'), and endocarditis (Spach & Koehler, 1998). Domestic cats represent the main host and reservoir for B. henselae. Infected cats develop a relapsing bacteraemia of several months' duration during which B. henselae may be transmitted to other cats or humans by Ctenocephalides felis (cat flea) or cat scratch or bite injuries.Identification of Bartonella species is usually based on molecular methods rather than biochemical reactions because of the fastidious and relatively inert nature of bartonellae. Analysis of the nucleotide sequence of the 16S rRNA gene was the first molecular method used for the identification of B. henselae (Relman et al., 1990). Bergmans et al. (1996) detected a 3 bp difference between the partial 16S rRNA sequences of clinical B. henselae isolates obtained from Dutch patients with cat scratch disease and divided the isolates into two distinct genotypes, 16S RNA type I and type II. Subsequently, isolates belonging to the 16S RNA types I or II were detected by different investigators in other countries (Birtles et al., 2002;Chang et al., 2002; Drancourt et al., 1996; Guptill et al., 2004;Melter et al., 2003;Sander et al., 1997). The 16S RNA types were designated 16S RNA alleles 1 and 2 and included in the MLST scheme for B. henselae (Iredell et al., 2003).We have recently studied the molecular epidemiology of B. henselae isolates from different hosts and various geographical regions by MLST (Arvand et al., 2007). During that study and in subsequent investigations, a total of 191 B. henselae isolates were subjected to direct 16S rRNA gene sequencing. Three of...

Horizontal Transfers and Gene Losses in the Phospholipid Pathway of Bartonella Reveal Clues about Early Ecological Niches

“…The gene is located in a genomic locus, where the upstream side is a group of four ORFs ending with the hisS (histidyl-tRNA synthetase) gene. The downstream side of gpsA in lineage 2 Bartonella genomes is an rRNA operon, which is typically present in all Bartonella genomes as two to three copies (Viezens and Arvand 2008; Guy et al 2013). The horizontal transfer of gpsA (He) into lineages 1 and 2 seems to have interrupted an ORF present in all bartonellae, which in lineage 2 bartonellae is still present with a residual sequence (fig.…”

Ecological fitness and strategies of adaptation ofBartonellaspecies to their hosts and vectors

“…These authors concluded that human isolates come from a limited subset of B. henselae strains. More recent analysis using multi-locus sequence typing (MLST) [5, 68, 87, 132] or multiple-locus variable-number tandem-repeat analysis (MLVA) also support the wide diversity of feline strains and the clustering of human cases within the broad range of feline isolates [17, 98]. A small percentage of B. henselae isolates may harbor two different 16S rRNA gene copies and these isolates may have emerged by horizontal gene transfer [132].…”

A genome-wide study of recombination rate variation in Bartonella henselae

“…An examination of polymorphisms in spacer regions showed similar levels of genetic diversity of the human and feline B. henselae strains [21], with some evidence for a history of recombination [18]. This was substantiated by the finding of hybrid 16S rRNA alleles in a small fraction (< 2%) of the population [22]. The rRNA genes are located inside the amplified region of the chromosome and the increased copy number of these genes could potentially increase their propensity for recombination [16].…”