Respiration capacity and consequences in XXXX .

@entity7878 @entity26 @entity1446
We recently reported that the well-studied fermenting bacterium @entity7878 could grow via a respirative metabolism in the presence of @entity26 when a @entity1446 source is present. Respiration induces profound changes in @entity7878 metabolism, and improvement of @entity26 tolerance and long-term survival. Compared to usual fermentation conditions, biomass is approximately doubled by the end of growth, acid production is reduced, and large amounts of normally minor end products accumulate. Lactococci grown via respiration survive markedly better after long-term storage than fermenting cells. We suggest that growth and survival of lactococci are optimal under respiration-permissive conditions, and not under fermentation conditions as previously supposed. Our results reveal the uniqueness of the @entity7878 respiration model. The well-studied 'aerobic' bacteria express multiple terminal cytochrome oxidases, which assure respiration all throughout growth; they also synthesize their own @entity1446 . In contrast, the @entity7878 cydAB genes encode a single cytochrome oxidase (bd), and @entity1446 must be provided. Furthermore, cydAB genes mediate respiration only late in growth. Thus, lactococci exit the lag phase via fermentation even if @entity1446 is present, and start respiration in late exponential phase. Our results suggest that the spectacularly improved survival is in part due to reduced intracellular oxidation during respiration. We predict that lactococcal relatives like the Enterococci, and some Lactobacilli, which have reported respiration potential, will display improved survival under respiration-permissive conditions.
