A genus of very small, coccoid to ellipsoidal, pleomorphic, nonmotile and nonsporulating, gram-negative, rod-shaped bacteria. It was named for Edward Francis, who studied the tularemia bacterium. Fastidious and strictly aerobic, it grows at 98.6°F (37°C) within several days, but only in enriched media such as coagulated egg yolk or glucose-cysteine-blood-agar. The genus is catalase-negative. Acid is produced from several carbohydrates; indole, urease, gelatinase, and nitrate reductase are not formed. The genome deoxyribonucleic acid contains 32–36 mol % guanine plus cytosine. The organisms occur in natural waters of the Northern Hemisphere, and can be parasitic and pathogenic in birds, anthropods, and mammals, including humans.