Rasmussen L J, Møller P L, Atlung T
Department of Microbiology, Technical University of Denmark, Copenhagen.
J Bacteriol. 1991 Oct;173(20):6390-7. doi: 10.1128/jb.173.20.6390-6397.1991.
The anaerobic expression of pfl is reduced both in a strain mutated in the pgi gene and in a pfkA pfkB double mutant strain when cells are grown in medium supplemented with glucose. When cells are grown in medium supplemented with either fructose or pyruvate, no reduction is observed in these strains. The amount of pyruvate in the cells may be responsible for the reduced expression of pfl in the strains mutated in the genes encoding the glycolytic enzymes. Because of the lowered oxygen concentration in the medium, the expression of pfl is induced when an exponentially growing culture enters the stationary phase. This induction is increased when the Casamino Acid concentration is raised 10-fold or when the medium is supplemented with NaCl. Superhelicity of DNA is decreased in a pgi mutant strain grown in medium supplemented with glucose. The superhelicity is also changed, but the opposite way, in a wild-type strain grown in medium supplemented with Casamino Acids at a high concentration or 0.3 M sodium chloride. Our data show that changes in superhelicity do not affect the aerobic expression of pfl but might be important for the anaerobic induction of pfl.
当细胞在添加葡萄糖的培养基中生长时，pgi基因突变菌株和pfkA pfkB双突变菌株中pfl的厌氧表达均降低。当细胞在添加果糖或丙酮酸的培养基中生长时，在这些菌株中未观察到表达降低。细胞中丙酮酸的量可能是编码糖酵解酶的基因突变菌株中pfl表达降低的原因。由于培养基中氧浓度降低，当指数生长的培养物进入稳定期时，pfl的表达被诱导。当酪蛋白氨基酸浓度提高10倍或培养基添加NaCl时，这种诱导作用增强。在添加葡萄糖的培养基中生长的pgi突变菌株中，DNA的超螺旋性降低。在添加高浓度酪蛋白氨基酸或0.3M氯化钠的培养基中生长的野生型菌株中，超螺旋性也发生变化，但方向相反。我们的数据表明，超螺旋性的变化不影响pfl的需氧表达，但可能对pfl的厌氧诱导很重要。
