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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #210919

Title: The role of cellulose and O-antigen capsule in the colonization of plants by Salmonella

Author
item Barak Cunningham, Jeri
item JAHN, COURTNEY
item GIBSON, DEANNA
item CHARKOWSKI, AMY

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2007
Publication Date: 12/1/2007
Citation: Barak Cunningham, J.D., Jahn, C.E., Gibson, D.L., Charkowski, A.O. 2007 The role of cellulose and O-antigen capsule in the colonization of plants by Salmonella. Molecular Plant-Microbe Interactions. 20(9) 1083-1091

Interpretive Summary: Numerous salmonellosis outbreaks have been associated with vegetables, in particular sprouted seeds. Thin aggregative fimbriae (Tafi), a component of the extracellular matrix responsible for multicellular behavior, are important for Salmonella enterica attachment and colonization of plants. Here we demonstrate that the other surface polymers comprising the extracellular matrix, cellulose and O-antigen capsule, also play a role in colonization of plants. Mutations in bacterial cellulose synthesis and O-antigen capsule assembly and translocation reduced the ability to attach to and colonize alfalfa sprouts. A colanic acid mutant was unaffected in plant attachment or colonization. Tafi, cellulose synthesis, and O-antigen capsule, all of which contribute to attachment and colonization of plants are all regulated by AgfD, suggesting that AgfD is a key regulator for survival outside of hosts of Salmonella. The cellulose biosynthesis regulator, adrA, mutant was not affected in the ability to attach to or colonize plants; however, promoter probe assays revealed expression by cells attached to alfalfa sprouts. Furthermore, qRT-PCR revealed differential expression of agfD and adrA between planktonic and plant-attached cells. In addition, there was no correlation among mutants between biofilm formation in culture and attachment to plants. Outside of animal hosts, S. enterica appears to rely on an arsenal of adhesins to persist on plants, which can act as vectors and perpetuate public health concerns.

Technical Abstract: Numerous salmonellosis outbreaks have been associated with vegetables, in particular sprouted seeds. Thin aggregative fimbriae (Tafi), a component of the extracellular matrix responsible for multicellular behavior, are important for Salmonella enterica attachment and colonization of plants. Here we demonstrate that the other surface polymers comprising the extracellular matrix, cellulose and O-antigen capsule, also play a role in colonization of plants. Mutations in bacterial cellulose synthesis (bcsA) and O-antigen capsule assembly and translocation (yihO) reduced the ability to attach to and colonize alfalfa sprouts. A colanic acid mutant was unaffected in plant attachment or colonization. Tafi, cellulose synthesis, and O-antigen capsule, all of which contribute to attachment and colonization of plants are all regulated by AgfD, suggesting that AgfD is a key regulator for survival outside of hosts of Salmonella. The cellulose biosynthesis regulator, adrA, mutant was not affected in the ability to attach to or colonize plants; however, promoter probe assays revealed expression by cells attached to alfalfa sprouts. Furthermore, qRT-PCR revealed differential expression of agfD and adrA between planktonic and plant-attached cells. In addition, there was no correlation among mutants between biofilm formation in culture and attachment to plants. Outside of animal hosts, S. enterica appears to rely on an arsenal of adhesins to persist on plants, which can act as vectors and perpetuate public health concerns.