A role of extracellular polysaccharides of Xanthomonas campestris pv. citri in bacterial adhesion to citrus leaf tissues in preinfectious stage.

Abstract

Unwashed bacterial cells of Xanthomonas campestris pv. citri were found to adhere preferentially to a wounded portion of citrus leaf tissues rather than intact leaf surfaces. Washed bacterial cells of X. campestris pv. citri and unwahhed bacterial cells of a colony mutant lacking the ability to produce extracellular polysaccharides (EPS) hardly adhered even to wounded tissues of citrus leaves.The adhesion of unwashed bacterial cells was inhibited when the wounded leaf tissues were pretreated either with D-glucosamine, pronase or low pH citrate buffer. The adhesion of unwashed bacterial cells was also observed to the disks of various nonhost tissues to an extent, but it was not influenced by the pretreatment with D-glucosamine solution at all.These results suggested that X. campestris pv. citri adhered to host tissues through the EPS-agglutinin interaction and that the process might involved in the initial step for establishing the host-parasite relationship in citrus canker.