CONTRIBUTION OF HORIZONTAL GENE-TRANSFER AND DELETION EVENTS TO DEVELOPMENT OF DISTINCTIVE PATTERNS OF FIMBRIAL OPERONS DURING EVOLUTION OFSALMONELLA SEROTYPES
Aj. Baumler et al., CONTRIBUTION OF HORIZONTAL GENE-TRANSFER AND DELETION EVENTS TO DEVELOPMENT OF DISTINCTIVE PATTERNS OF FIMBRIAL OPERONS DURING EVOLUTION OFSALMONELLA SEROTYPES, Journal of bacteriology, 179(2), 1997, pp. 317-322
Only certain serotypes of Salmonella represent 99% of all human clinic
al isolates. We determined whether the phylogenetic distribution of fi
mbrial operons would account for the host adaptations observed for Sal
monella serotypes. We found that three fimbrial operons, fim, lpf, and
agf, were present in a lineage ancestral to Salmonella. While the fim
and agf fimbrial operons were highly conserved among all Salmonella s
erotypes, sequence analysis suggested that the lpf operon was lost fro
m many distantly related lineages. As a consequence, the distribution
of the lpf operon cannot be explained easily and may be a consequence
of positive and negative selection in different hosts for the presence
of these genes. Two other fimbrial operons, sef and pef, each entered
two distantly related Salmonella lineages and each is present only in
a small number of serotypes. These results show that horizontal gene
transfer and deletion events have created unique combinations of fimbr
ial operons among Salmonella serotypes. The presence of sef and pef co
rrelated with serotypes frequently isolated from common domesticated a
nimals.