Stock Photo - Ralstonia mannitolilytica colorized SEM, x 6 740, the line represents 5 microns. Ralstonia mannitolilytica is Gram_positive bacillus, not sporulated, strict aerobe, saprophyte, living in the environment water, soil and plants. Not pathogenic in itself, this bacterium can be at the origin of hospital_acquired infections, meningites and respiratory infections in immunocompromised patients opportunistic disease. Ralstonia mannitolilytica Ralstonia Burkholderiaceae Burkholderiales Proteobacteria Bacterium. Magnified 6,740x, this scanning electron micrograph SEM depicted a grouping of Ralstonia mannitolilytica bacteria, which was harvested from a pure culture. Ralstonia spp.are gram_negative bacteria found in the environment, primarily in water, soil, and on plants. Occasionally, Ralstonia spp. are isolated from clinical samples, e.g., respiratory secretions of cystic fibrosis patients, and are developing a reputation as being an opportunistic pathogen in immunocompromised individuals.