A. Aguilar et al., Two genes from the capsule of Aeromonas hydrophila (serogroup 0 : 34) confer serum resistance to Escherichia coli K12 strains, RES MICROB, 150(6), 1999, pp. 395-402
The Escherichia coli DH5 alpha strain as well as other K12-derived strains
are unable to produce O-specific lipopolysaccharide and are thus rough and
serum-sensitive. One representative recombinant clone (COS-SR1) containing
Aeromonas hydrophila (serogroup O:34) chromosomal DNA conferred serum resis
tance to E. coli K12 strains. Genetic, biochemical, and immunological studi
es suggested that the two genes (orf1 and wcaJ) identified in a subclone (p
AC-SR9) of COS-SR1 are necessary for the production of the colanic acid cap
sule at 37 degrees C on E. coli DH5a, rendering the strain serum-resistant.
A. hydrophila strains from serogroup O:34 are able to produce capsule when
they grow both in synthetic medium and in an autolysate of fish viscera. H
owever, defined weal insertion mutants of A. hydrophila 1051-88 (serogroup
O:34) are unable to produce capsule on these media. This strongly suggests
that both genes belong to the gene cluster responsible for capsule producti
on (wca) of A. hydrophila 1051-88 (serogroup O:34). (C) Elsevier, Paris.