Non-heritable change of a spirochaete's phenotype by decoration of the cell surface with exogenous lipoproteins

Genetic transformation of Borrelia spp. is limited in development and has f ound application in only one species. For a non-genetic approach for manipu lating the phenotype of these spirochaetes, we determined whether exogenous recombinant lipoproteins would incorporate in the cell's outer membrane. U sing unlabelled or I-125-labelled Osp proteins, Osp-specific monoclonal ant ibodies, proteinase K and formaldehyde as reagents, we found that decoratio n of spirochaetes had the following characteristics. (i) Purified recombina nt OspA or OspD lipoproteins associated with Borrelia burgdorferi and B. he rmsii cells that lacked abundant lipoproteins of their own. (ii) This decor ation of the cells with exogenous OspA did not affect cell's viability. (ii i) The decoration was concentration and temperature dependent and stable fo r at least 24 h. (iv) Like native OspA, the recombinant OspA decorating the cells was accessible to antibodies and proteases and could be cross-linked to the integral outer membrane protein, P66. (v) Decoration of viable B. b urgdorferi and B. hermsii with OspA rendered the cells susceptible to killi ng by OspA-specific antiserum. Such non-genetic alteration of the surface o f a bacterium may be used to study functions and properties of lipoproteins in situ.