Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2004
Publication Date: 5/1/2004
Citation: Cohen, M.F., Han, X.Y., Mazzola, M. 2004. Molecular and physiological comparison of azospirillum spp. isolated from rhizoctonia solani mycelia, wheat rhizosphere and human skin wounds. Canadian Journal of Microbiology. 50:291-297. Interpretive Summary: Azospirillum spp. bacteria are commonly found on the roots of certain plants, especially grasses, and are generally recognized to promote growth of their hosts. It is known that the mechanisms involved in the colonization of plants by bacteria, such as Pseudomonas and Burkholderia, are similar to those involved in bacterial colonizaton of fungi and animals. We have found that an Azospirillum spp. isolated from wheat is nearly identical to one isolated from the fungus Rhizoctonia solani AG 5, a pathogen of apple roots. Comparisons with known bacteria showed close identity of our isolates with strains isolated from human wounds that had previously been misidentified as "Roseomonas" spp. We propose that these strains be reclassified as Azospirillum spp. Our results raise the possibility that Azospirillum may be able to colonize hosts other than plants.
Technical Abstract: Four strains of bacteria isolated from diverse sources were identified as species of Azospirillum, a genus typically found isolated associated with plant roots. Strains RC1 and LOD4 were isolated from the mycelium of the apple root pathogen Rhizoctonia solani AG 5, and the rhizosphere of wheat grown in apple orchard soil, respectively. Strains C610 and F4626, previously misclassified as Roseomonas genomospecies 3 and 6, were isolated from human wounds. All strains demonstrated strong similarities in 16S rRNA gene sequences and in many phenotypic traits, including the ability to fix N2. Cells of strains RC1, LOD4 and C610 but not of F4626 could be induced to flocculate by incubation with 10 mM glycerol or fructose in medium containing 0.5 mM NO3**-. Our results provide strong evidence for reclassifying "Roseomonas" spp. 3 and 6 into the genus Azospirillum and expand the range of potential sources for Azospirillum spp. to include fungi. The isolation of Azospirillum spp. from human wounds warrants further investigation.