Gram-negative, pleomorphic cells of a 6-day-old culture of Streptobacillus moniliformis DSM 12112T are arranged in chains and clumps and display irregular, lateral bulbar swellings, that resemble a ‘string of beads’ or a necklace – the translation of the Latin word moniliformis. The 0.1–0.7 × 1–5 µm sized bacteria tend to pleomorphism and might form up to 150 µm unbranched filaments. Oil immersion, ×1000 magnification. Bar, 5 µm.