Lactose metabolism in Streptococcus lactis: studies with a mutant lacking glucokinase and mannose-phosphotransferase activities

Journal Article · Mon Apr 01 00:00:00 EST 1985 · J. Bacteriol.; (United States)

OSTI ID:5646058

Thompson, J; Chassy, B M; Egan, W

A mutant of Streptococcus lactis 133 has been isolated that lacks both glucokinase and phosphoenolpyruvate-dependent mannose- phosphotransferase (mannose-PTS) activities. The double mutant S. lactis 133 mannose-PTSd GK- is unable to utilize either exogenously supplied or intracellularly generated glucose for growth. Fluorographic analyses of metabolites formed during the metabolism of (/sup 14/C)lactose labeled specifically in the glucose or galactosyl moiety established that the cells were unable to phosphorylate intracellular glucose. However, cells of S. lactis 133 mannose-PTSd GK- readily metabolized intracellular glucose 6-phosphate, and the growth rates and cell yield of the mutant and parental strains on sucrose were the same. During growth on lactose, S. lactis 133 mannose-PTSd GK- fermented only the galactose moiety of the disaccharide, and 1 mol of glucose was generated per mol of lactose consumed. For an equivalent concentration of lactose, the cell yield of the mutant was 50% that of the wild type. The specific rate of lactose utilization by growing cells of S. lactis 133 mannose-PTSd GK- was ca. 50% greater than that of the wild type, but the cell doubling times were 70 and 47 min, respectively. High-resolution /sup 31/P nuclear magnetic resonance studies of lactose transport by starved cells of S. lactis 133 and S. lactis 133 mannose-PTSd GK- showed that the latter cells contained elevated lactose-PTS activity. Throughout exponential growth on lactose, the mutant maintained an intracellular steady-state glucose concentration of 100 mM.

• Research Organization: National Institute of Dental Research, Bethesda, MD
• OSTI ID: 5646058
• Journal Information: J. Bacteriol.; (United States), Vol. 162:1
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
GLUCOSE
PHOSPHORYLATION
LACTOSE
METABOLISM
PHOSPHOTRANSFERASES
ENZYME ACTIVITY
STREPTOCOCCUS
GROWTH
CARBON 14 COMPOUNDS
METABOLITES
MUTANTS
NUCLEAR MAGNETIC RESONANCE
PHOSPHORUS 31
TRACER TECHNIQUES
ALDEHYDES
BACTERIA
CARBOHYDRATES
CHEMICAL REACTIONS
DISACCHARIDES
ENZYMES
HEXOSES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
MONOSACCHARIDES
NUCLEI
ODD-EVEN NUCLEI
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
RESONANCE
SACCHARIDES
STABLE ISOTOPES
TRANSFERASES
550501* - Metabolism- Tracer Techniques