An unknown bacterium that occurred as an experimental contaminant on a dilute nutrient broth (DNB) plate was characterized by phenotypic and phylogenetic analysis.The organism was found to be obligately aerobic, catalase positive, mesophilic, non-marine (NaCl intolerant), and rod-shaped in morphology. Under low-nutrient conditions the bacterium produced a highly active low-molecular weight agarase that caused softening and pitting of the agar around the bacterial colonies. This was considered to be unusual, since agar is a marine product. A portion of the 16s rRNA gene from this organism was amplified by PCR, cloned, and submitted for DNA sequencing. Phylogenetic analysis of the 16S rRNA gene identified the microbe as a member of the genus Sphingomonas , although a species match was not found. This laboratory provisionally named this terrestrial organism Sphingomonas alginolyticus due to its ability to degrade agar.