ACI1 lactamase of Acidaminococcus intestini is carried in a highly modular mobile genetic island
Abstract number: P891
Objective: To characterize the genetic environment of blaACI-1 gene present in the chromosome of human Acidaminococcus intestini and the possible events involved in its horizontal gene transfer.
Methods:b-lactam resistant RYC-MR95, RYC-MR02, RYC-MR88, RYC-MR24, RYC-MR37 strains of A. intestini were collected from clinical samples at our Hospital. Genome extraction, pyrosequenciation and inverse PCR plus sequenciation were used in the characterization process. Bioinformatics analysis included BLAST, Artemis, database search and neighbour-joining (NJ) for phylogenetic trees.
Results: A 55,797 bp DNA sequence flanked by 67 bp direct repeats (DRs), carrying blaACI-1 gene and presenting two large serine-recombinases was detected in RYC-MR95. This sequence constitutes the core element. Such element was found to be inserted into a greater one (100,778 bp), also flanked by 54 bp DRs, carrying a single recombinase. Southern blot assays using several orfs as probes revealed the presence of 2 copies of the core element in A. intestini chromosome. The second copy, of 55.8 Kb, lacking the blaACI-1 gene, had an insertion of 55,131 bp, and the complex was flanked by the same 67 bp DRs than the first core element. The Acidaminococcus sp. D21 complete genome sequence (EMBL), has only one copy of the core element, which was inserted in the same site that the second copy in A. intestini RYC-MR95, whereas the specific site of insertion for the first copy was empty in Acidaminococcus sp D21. These results suggest horizontal gene transfer events. To confirm this point several housekeeping and ACI-1 element genes were sequenced in all the strains of the study, belonging to different Acidaminococcus species. The phylogenetic tree obtained by NJ discriminated the branches for different species, while the phylogenetic trees obtained using genes from core element showed a mixture between branches, suggesting horizontal gene transfer. Such element shows modules from different origins, including genes of five different functional groups: recombinases, polymerases and endonucleases, virulence, transcriptional regulation and methylases and phage origin genes.
Conclusions: A mobile sequence of 55.8 Kb was found in two sites in the chromosome of A. intestini RYC-MR95. According to known sequence in Acidaminococcus sp. D21 these sites are site-specific suggesting mobilization by site-specific recombinases. Different functional modules from different origins suggest a modular evolution.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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