S. Swart et al., RHICADHESIN-MEDIATED ATTACHMENT AND VIRULENCE OF AN AGROBACTERIUM-TUMEFACIENS CHVB MUTANT CAN BE RESTORED BY GROWTH IN A HIGHLY OSMOTIC MEDIUM, Journal of bacteriology, 176(12), 1994, pp. 3816-3819
Cyclic beta-1,2-glucan is considered to play a role in osmoadaptation
of members of the family Rhizobiaceae in hypotonic media. Agrobacteriu
m tumefaciens chvB mutants, lacking beta-1,2-glucan, exhibit a pleiotr
opic phenotype, including nonmotility, attachment deficiency, and avir
ulence. Here we report that by growth of chvB mutant cells in tryptone
-yeast extract medium supplemented with 7 mM CaCl2 and 100 mM NaCl2 th
e mutant cells become motile, attach to pea root hair tips, and are vi
rulent on kalanchoe; leaves. Moreover, whereas chvB mutants grown in t
ryptone-yeast extract medium containing 7 mM CaCl2 do not produce acti
ve rhicadhesin, addition of 100 mM NaCl to this medium resulted in res
toration of rhicadhesin activity. The presence of CaCl2 appeared to be
required for attachment, virulence, and activity of rhicadhesin. The
results support a role for cyclic beta-1,2-glucan in osmoadaptation an
d strengthen the notion that rhicadhesin is required for attachment an
d virulence of A. tumefaciens.