Phenotypic heterogeneity usually refers to phenotypic variation not associated to genetic variation, nor induced by environmental stimuli. The phenotypic heterogeneity processes described for some complex bacterial traits is causing a shift on how bacterial phenotypes are studied, from traditional assessments by averaging populations to single-cell analysis focused on bacterial individual phenotypes and how these distribute within the population. The structure of the lipopolysaccharide (LPS) layer on the outer membrane in gram-negative bacteria is often subjected to phase variation, a form of phenotypic variation critical for virulence in animal pathogens. Here, we apply single-cell expression analyses to wbpL, a conserved Pseudomonas syringae glycosyltransferase-encoding gene essential for the synthesis of the o-antigen component of LPS. We show that expression of wbpL displays phenotypic heterogeneity in P. syringae pv. phaseolicola growing in rich medium, reaching bistable expression in minimal media, where the population splits into WbpL ON and WpbL OFF subpopulations. In planta, wbpL expression is also heterogeneous, displaying intermingled ON/OFF with comparable viability. Finally, we followed expression of wbpL within the spatial context of apoplastic microcolonies. detecting heterogeneity within each microcolony, but also found that microcolonies displayed overall differences in fluorescence intensity that correlated size, with smaller microcolonies displaying higher levels of wbpL expression.