Membrane alteration is necessary but not sufficient for effective glutamate secretion in Corynebacterium glutamicum

Abstract

We showed recently that secretion of glutamate in biotin-limited cells of Corynebacterium glutamicum is mediated by carrier systems in the plasma membrane (C. Hoischen -and R. Kramer, Arch. Microbiol. 151:342-347, 1989). In view of the generally accepted hypothesis that glutamate efflux is directly caused by alterations of the membrane, it was necessary to examine the kind of correlation between changes in lipid content and composition of the bacterial membrane and glutamate secretion activity. Two new experimental approaches were'used. (i) Changes in lipid content and composition were analyzed in glutamate-producing cells which were forced to switch to nonproducers by addition of biotin in a short-term fermentation. (ii) The time courses of both the fatty acid or phospholipid composition and the efflux activity were analyzed within the first minutes of the switch from high to low secretion activity. The following results were obtained. (i) The time course of the change i,n fatty acid or phospholipid content and composition was not related to the change in secretion behavior. (ii) There was no specific fatty acid or phospholipid compound which regulated glutamate efflux. (iii) High efflux activity could only be induced when the total lipid content of the membrane was reduced.

Biochemical and genetic characterization of the membrane‐associated malate dehydrogenase (acceptor) from Corynebacterium glutamicum

“…The activity is opti-is surprising that the activation of Mqo from C. glutamicum can be achieved with lipids from E. coli, since the main component mally stimulated by Q-1, a benzoquinone. Naphthoquinones of this lipid preparation is the zwitterionic phosphatidylethanol-∆G°′ for the quinone-dependent reaction is very favourable for oxaloacetate formation, equal to Ϫ55.0 kJ/mol when ubiquinone amine, whereas the main lipid in C. glutamicum is the anionic phosphatidylglycerol [34]. The Mqo from M. smegmatis was is the acceptor or Ϫ18.9 kJ/mol when menaquinone is the acceptor.…”

Osmosensor and Osmoregulator Properties of the Betaine Carrier BetP from Corynebacterium glutamicum in Proteoliposomes

“…Proteoliposomes are an ideal tool to test the second alternative. E. coli plasma membranes consist of 80% phosphatidyl ethanolamine, 15% phosphatidyl glycerol, and 5% diphosphatidyl glycerol (33), whereas those of C. glutamicum contain mainly phosphatidyl glycerol (87%) and minor amounts of other phospholipids (5% phosphatidyl inositolmannoside, 3% phosphatidyl inositol, 2.5% phosphatidic acid, and 1% diphosphatidyl glycerol) (34). Unfortunately, no stable liposomes could be prepared from lipid extracts of C. glutamicum cells, although various extraction procedures have been applied (results not shown).…”

Production of glutamic acid by Corynebacterium glutamicum using dates syrup as carbon source

“…The growths of cells were determined by measuring the absorbance at 600 nm spectrophotometrically (Shimadzu 24016), according to the methods of Hoischen et al (1990). Absorbency was converted to dry weight by using a standard curve.…”

“…Fifty milliliter (50 ml) of fermentation media were added to the flasks (250ml). To each flask, the 1 ml inoculums of a 24-h-old culture was added and incubated in a rotary flask shaker at 150 rpm at 31°C (Hoischen et al, 1990).…”