The cultural, physiological, and biochemical characters of 21 strains of Lactobacillus coryniformis, isolated from Iraqi cheese, were investigated. Some of the strains grew at 45 degrees C. All possessed the following characteristics: they did not contain DAP; no growth in 4% taurocholate or in 9% NaCl; growth in 6.5% NaCl; milk mostly coagulated within 3 to 60 days with final activity of 0.85--1.09% and pH 4.05; xylose, (D+)tagatose, inulin, and trehalose not fermented; ribose fermented by only one strain and arabinose by another; pyruvate, malate, and fumarate decomposed in the presence of glucose with formation of carbon dioxide; CO2 was produced from gluconate by 20 out of 21 strains. The mean total amount of lactate, produced after 41 days at 30 degrees C, was 42.6 +/- 2.5 mumoles per ml, of L(+)lactate 17.8 +/- 1.1, and of % L(+)lactate of total lactate 42.3 +/- 1.7. The isolates degraded pyruvate (111 mumoles/ml) in the presence of glucose (55.5 mumoles/ml) with lactate as the major product, together with acetate 5.8%, ethanol 8.15%, acetoin 1.95%, and diacetyl 2.50% yield on a molar basis after 60 days at 30 degrees C. Diacetyl and acetoin could be formed from pyruvate plus glucose, but not from either glucose alone, citrate alone, or from citrate plus glucose. The mean total amount of diacetyl plus acetoin, after 26 days at 30 degrees C, was 1059.6 +/- 24.0 micrograms/ml, of diacetyl 92.8 +/- 2.2, and of % diacetyl of the total diacetyl plus acetoin was 8.8 +/- 0.3. L. coryniformis differs from L. plantarum in morphology, in not containing DAP, in failure to grow in 4% taurocholate, in not fermenting ribose and trehalose, and in not decomposing tartrate.