Chatterjee A K, Ross H, Sanderson K E
Can J Microbiol. 1976 Oct;22(10):1549-60. doi: 10.1139/m76-227.
Mutants of Salmonella typhimurium with defects in the heptose region of the lipopolysaccharide (LPS) molecule (heptose-deficient, chemotype Re) leak periplasmic enzymes (acid phosphatase (EC 3.1.3.2), cyclic phosphodiesterase, ribonuclease I (EC 3.1.4.22), and phosphoglucose isomerase (EC 5.3.1.9) (PGI is at least partially periplasmic in E. coli and S. typhimurium; see below)) and do not leak an internal enzyme (glucose-6-phosphate dehydrogenase) into the growth medium. The extent of this leakage is markedly increased at higher temperature (42 degrees C). Leakage of periplasmic enzymes from the strains lacking units distal to heptose I in the LPS molecule (chemotype Rd2) occurs only at 42 degrees C, and not at 30 or 37 degrees C. The extent of leakage of these enzymes from smooth strain and mutants of other LPS chemotypes (Rc, Rd1) is not significant, and is not influenced by growth temperatures. The kinetics of leakage of periplasmic enzymes after shift to 42 degrees C in nutrient broth reveal an accelerated release into the medium from heptose-deficient strains of cyclic phosphodiesterase and ribonuclease I after 30 min at 42 degrees C, and phosphoglucose isomerase after 60 min at 42 degrees C; at 30 degrees C the rate of release of cyclic phosphodiesterase and ribonuclease I is relatively slower. After 60 min at 42 degrees C in nutrient broth, growth of these strains has either slowed down or stopped. In L-broth, which permits the growth of the heptose-deficient strain (SA1377) at 42 degrees C, leakage of cyclic phosphodiesterase and phosphoglucose isomerase occurs, whereas there is no detectable leakage of these enzymes from the isogenic smooth strain (SA1355). Thus, leakage of the periplasmic enzymes from the heptose-deficient strain occurs with or without growth. Mg2+ (0.75 mM), sodium chloride (50 mM), and sucrose (100 mM) in nutrient broth at 42 degrees C prevent the leakage of these enzymes. The shedding of LPS from the heptose-deficient as well as the smooth strains is enhanced by high temperature (42 degrees C), whereas considerable leakage of protein occurs only in the heptose-deficient strain at 42 degrees C and not in the smooth strain. The smooth and heptose-deficient strains are equally sensitive to osmotic shock although a significant proportion of acid phosphatase and cyclic phosphodiesterase activities from the heptose-deficient cells grown at 42 degrees C comes off in the Tris-NaCl wash step suggesting a rather loose attachment of these enzymes onto the cell surface.
鼠伤寒沙门氏菌在脂多糖（LPS）分子庚糖区域存在缺陷的突变体（庚糖缺陷型，化学型Re）会渗漏周质酶（酸性磷酸酶（EC 3.1.3.2）、环磷酸二酯酶、核糖核酸酶I（EC 3.1.4.22）和磷酸葡萄糖异构酶（EC 5.3.1.9）（在大肠杆菌和鼠伤寒沙门氏菌中，磷酸葡萄糖异构酶至少部分存在于周质中；见下文）），但不会将内部酶（葡萄糖-6-磷酸脱氢酶）渗漏到生长培养基中。在较高温度（42℃）下，这种渗漏程度会显著增加。LPS分子中缺乏庚糖I远端单元的菌株（化学型Rd2）的周质酶渗漏仅发生在42℃，而在30℃或37℃时不发生。这些酶从光滑菌株和其他LPS化学型（Rc、Rd1）突变体中的渗漏程度不显著，且不受生长温度影响。在营养肉汤中转移至42℃后，周质酶的渗漏动力学显示，在42℃下30分钟后，环磷酸二酯酶和核糖核酸酶I从庚糖缺陷型菌株加速释放到培养基中，42℃下60分钟后磷酸葡萄糖异构酶加速释放；在30℃时，环磷酸二酯酶和核糖核酸酶I的释放速率相对较慢。在营养肉汤中42℃下60分钟后，这些菌株的生长要么减缓要么停止。在L肉汤中，庚糖缺陷型菌株（SA1377）能在42℃生长，会发生环磷酸二酯酶和磷酸葡萄糖异构酶的渗漏，而从同基因光滑菌株（SA1355）中未检测到这些酶的渗漏。因此，无论生长与否，庚糖缺陷型菌株都会发生周质酶的渗漏。营养肉汤中42℃的Mg2 +（0.75 mM）、氯化钠（50 mM）和蔗糖（100 mM）可防止这些酶的渗漏。高温（42℃）会增强庚糖缺陷型菌株和平滑菌株中LPS的脱落，而只有庚糖缺陷型菌株在42℃时会发生大量蛋白质渗漏，光滑菌株则不会。光滑菌株和庚糖缺陷型菌株对渗透压休克同样敏感，尽管在42℃生长的庚糖缺陷型细胞中，相当一部分酸性磷酸酶和环磷酸二酯酶活性在Tris - NaCl洗涤步骤中脱落，这表明这些酶在细胞表面的附着相当松散。
