Intragenic tandem repeat variation between Legionella pneumophila strains.
BACKGROUND
Bacterial genomes harbour a large number of tandem repeats, yet the possible phenotypic effects of those found within the coding region of genes are only beginning to be examined. Evidence exists from other organisms that these repeats can be involved in the evolution of new genes, gene regulation, adaptation, resistance to environmental stresses, and avoidance of the immune system.


RESULTS
In this study, we have investigated the presence and variability in copy number of intragenic tandemly repeated sequences in the genome of Legionella pneumophila, the etiological agent of a severe pneumonia known as Legionnaires' disease. Within the genome of the Philadelphia strain, we have identified 26 intragenic tandem repeat sequences using conservative selection criteria. Of these, seven were "polymorphic" in terms of repeat copy number between a large number of L. pneumophila serogroup 1 strains. These strains were collected from a wide variety of environments and patients in several geographical regions. Within this panel of strains, all but one of these seven genes exhibited statistically different patterns in repeat copy number between samples from different origins (environmental, clinical, and hot springs).


CONCLUSIONS
These results support the hypothesis that intragenic tandem repeats could play a role in virulence and adaptation to different environments. While tandem repeats are an increasingly popular focus of molecular typing studies in prokaryotes, including in L. pneumophila, this study is the first examining the difference in tandem repeat distribution as a function of clinical or environmental origin.
Coil
David A
DA
Laboratory of Bacteriology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
Vandersmissen
Liesbeth
L
Ginevra
Christophe
C
Jarraud
Sophie
S
Lammertyn
Elke
E
Anné
Jozef
J
D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D014644:Genetic Variation; D016680:Genome, Bacterial; D006801:Humans; D016952:Legionella pneumophila / Q000145:classification / Q000235:genetics*; D020080:Tandem Repeat Sequences
D004269:DNA, Bacterial