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Respiration metabolism reduces oxidative and acid stress to improve long‐term survival of Lactococcus lactis
Author(s) -
Rezaïki Lahcen,
Cesselin Bénédicte,
Yamamoto Yuji,
Vido Karin,
Van West Evelien,
Gaudu Philippe,
Gruss Alexandra
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2004.04217.x
Subject(s) - respiration , biology , lactococcus lactis , cellular respiration , biochemistry , oxidative phosphorylation , metabolism , fermentation , oxidative stress , aeration , oxygen , bacteria , mitochondrion , chemistry , lactic acid , genetics , ecology , botany , organic chemistry
Summary The impact of oxygen on a cell is strongly dependent on its metabolic state: survival in oxygen of free‐living Lactococcus lactis , best known as a fermenting, acidifying bacterium, is generally poor. In contrast, if haem is present, L. lactis uses oxygen to switch from fermentation to respiration metabolism late in growth, resulting in spectacularly improved long‐term survival. Oxygen is thus beneficial rather than detrimental for survival if haem is provided. We examined the effects of respiration on oxygen toxicity by comparing integrity of stationary phase cells after aerated growth without and with added haem. Aeration (no haem) growth caused considerable cellular protein and chromosomal DNA damage, increased spontaneous mutation frequencies and poor survival of recA mutants. These phenotypes were greatly diminished when haem was present, indicating that respiration constitutes an efficient barrier against oxidative stress. Using the green fluorescent protein as an indicator of intracellular oxidation state, we showed that aeration growth provokes significantly greater oxidation than respiration growth. Iron was identified as a main contributor to mortality and DNA degradation in aeration growth. Our results point to two features of respiration growth in lactococci that are responsible for maintaining low oxidative damage: One is a more reduced intracellular state, which is because of efficient oxygen elimination by respiration. The other is a higher pH resulting from the shift from acid‐forming fermentation to respiration metabolism. These results have relevance to other bacteria whose respiration capacity depends on addition of exogenous haem.