We have recently developed a new L-lysine-producing mutant of Corynebacterium glutamicum by 'genome breeding' consisting of characterization and reconstitution of a mutation set essential for high-level production. The strain AHP-3 was examined for L-lysine fermentation on glucose at temperatures above 35degreesC, at which no examples of efficient L-lysine production have been reported for this organism. We found that the strain had inherited the thermotolerance that the original coryneform bacteria was endowed with, and thereby grew and produced L-lysine efficiently up to 41degreesC. A final titer of 85 g/l after only 28 h was achieved at temperatures around 40degreesC, indicating the superior performance of the strain developed by genome breeding. When compared with the traditional 30degreesC fermentation, the 40degreesC fermentation allowed an increase in yield of about 20% with a concomitant decrease in final growth level, suggesting a significant transition of carbon flux distribution in glucose metabolism. DNA array analysis of metabolic changes between the 30degreesC and 40degreesC fermentations identified several differentially expressed genes in central carbon metabolism although we could not find stringent control-like global induction of amino-acid-biosynthetic genes in the 40degreesC fermentation. Among these changes, two candidates were picked out as the potential causes of the increased production at 40degreesC; decreased expression of the citrate synthase gene gltA and increased expression of malE, the product of which involves regeneration of pyruvate and NADPH.