Wells J E, Russell J B
Section of Microbiology, Cornell University, Ithaca, New York 14853, USA.
Appl Environ Microbiol. 1996 Apr;62(4):1342-6. doi: 10.1128/aem.62.4.1342-1346.1996.
Growing cultures of Fibrobacter succinogenes assimilated more ammonia than could be accounted for by cellular protein, RNA, or DNA and released large amounts of nonammonia nitrogen. The difference between net and true growth was most dramatic at low dilution rates, but mathematical derivations indicated that the lysis rate was a growth rate-independent function. The lysis rate was sevenfold greater than the true maintenance rate (0.07 h-1 versus 0.01 h-1). Because slowly growing cells had as much proton motive force and ATP as fast-growing cells, lysis was not a starvation response per se. Stationary-phase cells had a lysis rate that was 10-fold less than that of growing cells. Rapidly growing cells were not susceptible to phenylmethylsulfonyl fluoride, but phenylmethylsulfonyl fluoride increased the lysis rate of the cultures when they reached the stationary phase. This latter result indicated that autolysins of stationary-phase cells were being inactivated by a serine proteinase. When growing cells were treated with the glycolytic inhibitor iodoacetate, the proteinase-dependent transition to the stationary phase was circumvented, and the rate of lysis could be increased by as much as 50-fold.
正在生长的琥珀酸纤维杆菌培养物吸收的氨比细胞蛋白质、RNA或DNA所能解释的要多，并释放出大量非氨态氮。净生长和实际生长之间的差异在低稀释率时最为显著，但数学推导表明，裂解率是一个与生长速率无关的函数。裂解率比实际维持率高7倍（分别为0.07 h-1和0.01 h-1）。由于生长缓慢的细胞与快速生长的细胞具有相同的质子动力和ATP，因此裂解本身并非饥饿反应。稳定期细胞的裂解率比生长细胞低10倍。快速生长的细胞对苯甲基磺酰氟不敏感，但当培养物进入稳定期时，苯甲基磺酰氟会增加其裂解率。后一结果表明，稳定期细胞的自溶素被一种丝氨酸蛋白酶灭活。当用糖酵解抑制剂碘乙酸处理生长细胞时，可规避蛋白酶依赖的向稳定期的转变，且裂解率可提高多达50倍。
