A novel tripeptide, 1, was isolated from the extracellular extract of a Pseudomonas-Alteromonas bacterium that was associated with the Black Sea sponge Dysidea fragilis. Compound 1 contains the novel beta-aminopimelic acid described for the first time from a natural product. The structure of 1 is suggested on the basis of the analysis of spectroscopic data and chemical degradation.