title: Increasing acidification of nonreplicating Lactococcus lactis deltathyA mutants by incorporating ATPase activity.
abstract: Lactococcus lactis MBP71 deltathyA (thymidylate synthase) cannot synthesize dTTP de novo, and DNA replication is dependent on thymidine in the growth medium. In the nonreplicating state acidification by MBP71 was completely insensitive to bacteriophages (M. B. Pedersen, P. R. Jensen, T. Janzen, and D. Nilsson, Appl. Environ. Microbiol. 68:3010-3023, 2002). For nonreplicating MBP71 the biomass increased 3.3-fold over the first 3.5 h, and then the increase stopped. The rate of acidification increased 2.3-fold and then started to decrease. Shortly after inoculation the lactic acid flux was 60% of that of exponentially growing MBP71. However, when nonspecific ATPase activity was incorporated into MBP71, the lactic acid flux was restored to 100% but not above that point, indicating that control over the flux switched from ATP demand to ATP supply (i.e., to sugar transport and glycolysis). As determined by growing nonreplicating cells with high ATPase activity on various sugar sources, it appeared that glycolysis exerted the majority of the control. ATPase activity also stimulated the rate of acidification by nonreplicating MBP71 growing in milk, and pH 5.2 was reached 40% faster than it was without ATPase activity. We concluded that ATPase activity is a functional means of increasing acidification by nonreplicating L. lactis.
authors.affiliation: Department of Genomics and Strain Development. Research, Development, and Application, Chr. Hansen A/S, DK-2970 Hørsholm, Denmark. MartinB.Pedersen@dk.chr-hansen.com
authors.forename: Martin B
authors.initials: MB
authors.lastname: Pedersen
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Koebmann
authors.forename: Peter R
authors.initials: PR
authors.lastname: Jensen
authors.forename: Dan
authors.initials: D
authors.lastname: Nilsson
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D002876:Chromosomes, Bacterial; D019344:Lactic Acid / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D013223:Statistics as Topic
chemical_list: D019344:Lactic Acid; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases