Achromobacter denitrificans Strain YD35 Pyruvate Dehydrogenase Controls NADH Production To Allow Tolerance to Extremely High Nitrite Levels

作者：Doi Yuki; Shimizu Motoyuki; Fujita Tomoya; Nakamura Akira; Takizawa Noboru; Takaya Naoki^*

来源：Applied and Environmental Microbiology, 2014, 80(6): 1910-1918.

DOI：10.1128/AEM.03316-13

We identified the extremely nitrite-tolerant bacterium Achromobacter denitrificans YD35 that can grow in complex medium containing 100mMnitrite (NO2-) under aerobic conditions. Nitrite induced global proteomic changes and upregulated tricarboxylate (TCA) cycle enzymes as well as antioxidant proteins in YD35. Transposon mutagenesis generated NO2- -hypersensitive mutants of YD35 that had mutations at genes for aconitate hydratase and alpha-ketoglutarate dehydrogenase in the TCA cycle and a pyruvate dehydrogenase (Pdh) E1 component, indicating the importance of TCA cycle metabolism to NO2- tolerance. A mutant in which the pdh gene cluster was disrupted (Delta pdh mutant) could not grow in the presence of 100mM NO2-. Nitrite decreased the cellular NADH/NAD(+) ratio and the cellular ATP level. These defects were more severe in the Delta pdh mutant, indicating that Pdh contributes to upregulating cellular NADH and ATP and NO2- -tolerant growth. Exogenous acetate, which generates acetyl coenzyme A and then is metabolized by the TCA cycle, compensated for these defects caused by disruption of the pdh gene cluster and those caused by NO2-. These findings demonstrate a link between NO2- tolerance and pyruvate/acetate metabolism through the TCA cycle. The TCA cycle mechanism in YD35 enhances NADH production, and we consider that this contributes to a novel NO2- -tolerating mechanism in this strain.

• 出版日期2014-3