Specificity of the Envelopment of Bacteria and Other Particles in Cotton Cotyledons

Abstract

During the hypersensitive response of cotyledons of incompatible cotton line Im 216 following infiltration with a suspension of Xanthomonas capestris pv. malvacearum, bacterial cells were observed by transmission electron microscopy to be enveloped by fibrillar materials and often covered by more dense cuticlelike materials on the host cell wall surfaces. Cells of the same pathovar were never enveloped in compatible cotton line Ac 44, whereas all cells of incompatible pathovar X. campestris pv. campestris were enveloped. In Ac 44, envelopes formed (without an accompanying hypersensitive response) around cells of compatible X. campestris pv. malvacearum that had been killed by heat, rifamycin, or UV light. Polystyrene latex particles 0.5 .mu.m in diameter were not enveloped in cotyledons of either cotton line. However, the Gram-positive bacterium Micrococcus lysodeikticus and corn starch grains were both enveloped in Ac 44. Bacteria and other hydrophilic particles are apparently generally enveloped at the surface of cotton cell walls, but during compatible interactions envelopment is actively prevented.