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Characterization of a Corynebacterium glutamicum Lactate Utilization Operon Induced during Temperature-Triggered Glutamate Production

2005; American Society for Microbiology; Volume: 71; Issue: 10 Linguagem: Inglês

10.1128/aem.71.10.5920-5928.2005

1098-5336

Corinna Stansen, Davin Uy, Stéphane Delaunay, Lothar Eggeling, Jean‐Louis Goergen, Volker F. Wendisch,

Biofuel production and bioconversion

ABSTRACT Gene expression changes of glutamate-producing Corynebacterium glutamicum were identified in transcriptome comparisons by DNA microarray analysis. During glutamate production induced by a temperature shift, C. glutamicum strain 2262 showed significantly higher mRNA levels of the NCgl2816 and NCgl2817 genes than its non-glutamate-producing derivative 2262NP. Reverse transcription-PCR analysis showed that the two genes together constitute an operon. NCgl2816 putatively codes for a lactate permease, while NCgl2817 was demonstrated to encode quinone-dependent l -lactate dehydrogenase, which was named LldD. C. glutamicum LldD displayed Michaelis-Menten kinetics for the substrate l -lactate with a K m of about 0.51 mM. The specific activity of LldD was about 10-fold higher during growth on l -lactate or on an l -lactate-glucose mixture than during growth on glucose, d -lactate, or pyruvate, while the specific activity of quinone-dependent d -lactate dehydrogenase differed little with the carbon source. RNA levels of NCgl2816 and lldD were about 18-fold higher during growth on l -lactate than on pyruvate. Disruption of the NCgl2816- lldD operon resulted in loss of the ability to utilize l -lactate as the sole carbon source. Expression of lldD restored l -lactate utilization, indicating that the function of the permease gene NCgl2816 is dispensable, while LldD is essential, for growth of C. glutamicum on l -lactate.