A calcium-dependent bacterial surface protein is involved in the attachment of rhizobia to peanut roots

DARDANELLI,M; ANGELINI, J.; FABRA, A.

CANADIAN JOURNAL OF MICROBIOLOGY

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Lugar: Otawa; Año: 2003 vol. 49 p. 399 - 405

0008-4166

As part of a project to characterize molecules involved in the crack-entry infection process leading to nodule development,a microscopic assay was used to visualize the attachment of cells of Bradyrhizobium sp. strains SEMIA 6144and TAL 1000 (labelled by introducing a plasmid expressing constitutively the green fluorescent protein GFP-S65T) toArachis hypogaea L. (peanut). Qualitative and quantitative results revealed that attachment was strongly dependent onthe growth phase of the bacteria. Optimal attachment occurred when bacteria were at the late log or early stationaryphase. Cell surface proteins from the Bradyrhizobium sp. strains inhibited the attachment when supplied prior to theattachment assay. Root incubation with a 14-kDa protein (eluted from sodium dodecyl sulphate ? gel electrophoresis ofthe cell surface fraction) prior to the attachment assay resulted in a strong decrease of attachment. The adhesin appearedto be a calcium-binding protein, since cells treated with EDTA were found to be able to bind to adhesin-treatedpeanut roots. Since this protein has properties identical to those reported for rhicadhesin, we propose that this adhesinis also involved in the attachment process of rhizobia to root legumes that are infected by the crack-entry process