The irp2 gene codes for a 190 kDa protein (HMWP2) synthesized
when highly pathogenic Yersinia are grown under conditions of
iron starvation. In this work, the presence of irp2 in strains
of Y. pestis isolated from different hosts during several
plague outbreaks in the foci of Northeast Brazil was studied.
For this purpose, 53 strains were spotted onto nylon filters
and their DNA was hybridized with the A13 probe which is a 1
kb fragment of the irp2 coding sequence. All strains except
two hybridized with the probe. However, when the initial stock
culture of these two strains were analyzed, they both proved
to be positive with the A13 probe, indicating that the locus
was lost after subculture in vitro but was always present in
vivo. To examine the degree of conservation of the chromosomal
fragment carrying irp2 among Brazilian strains, the
hybridization profiles of 15 strains from different outbreaks,
different hosts and different foci were compared. The
hybridization profiles of these strains were all identical
when their DNA was digested with either EcoRI, EcoRV or AvaII,
indicating that the restriction sites surrounding the irp2
locus are very well conserved among Northeast Brazilian
strains of Y. pestis. Altogether, these results suggest that
the irp2 chromosomal region should be of prime importance for
the bacteria during their multiplication in the host.
