Lectin microarray reveals binding profiles of Lactobacillus casei strains in a comprehensive analysis of bacterial cell wall polysaccharides.

We previously showed a pivotal role of the polysaccharide (PS) moiety in the cell wall of the Lactobacillus casei strain Shirota (YIT 9029) as a possible immune modulator (E. Yasuda M. Serata, and T. Sako, Appl. Environ. Microbiol. 74:4746-4755, 2008). To distinguish PS structures on the bacterial cell surface of individual strains in relation to their activities, it would be useful to have a rapid and high-throughput methodology. Recently, a new technique called lectin microarray was developed for rapid profiling of glycosylation in eukaryotic polymers and cell surfaces. Here, we report on the development of a simple and sensitive method based on this technology for direct analysis of intact bacterial cell surface glycomes. The method involves labeling bacterial cells with SYTOX Orange before incubation with the lectin microarray. After washing, bound cells are directly detected using an evanescent-field fluorescence scanner in a liquid phase. Using this method, we compared the cell surface glycomes from 16 different strains of L. casei. The patterns of lectin-binding affinity of most strains were found to be unique. There appears to be two types of lectin-binding profiles: the first is characterized by a few lectins, and the other is characterized by multiple lectins with different specificities. We also showed a dramatic change in the lectin-binding profile of a YIT 9029 derivative with a mutation in the cps1C gene, encoding a putative glycosyltransferase. In conclusion, the developed technique provided a novel strategy for rapid profiling and, more importantly, differentiating numerous bacterial strains with relevance to the biological functions of PS.