Kaplan H B, Greenberg E P
J Bacteriol. 1985 Sep;163(3):1210-4. doi: 10.1128/jb.163.3.1210-1214.1985.
The enzymes for luminescence in Vibrio fischeri are induced by the accumulation of a species-specific metabolite (autoinducer) in the culture medium. Tritium-labeled autoinducer was used to study the mechanism of autoinduction. When 3H-autoinducer was added to suspensions of V. fischeri or Escherichia coli, cellular concentrations equaled external concentrations. For V. fischeri, equilibration of 3H-autoinducer was rapid (within 20 s), and greater than 90% of the cellular tritium remained in unmodified autoinducer. When V. fischeri or E. coli cells containing 3H-autoinducer were transferred to autoinducer-free buffer, 85 to 99.5% of the radiotracer escaped from the cells, depending on the strain. Concentrations of autoinducer as low as 10 nM, which is equivalent to 1 or 2 molecules per cell, were sufficient for induction, and the maximal response to autoinducer occurred at about 200 nM. If external autoinducer concentrations were decreased to below 10 nM after induction had commenced, the induction response did not continue. Based on this study, a model for autoinduction is described wherein autoinducer association with cells is by simple diffusion and binding of autoinducer to its active site is reversible.
费氏弧菌中产生发光的酶是由培养基中一种物种特异性代谢物（自诱导物）的积累所诱导的。用氚标记的自诱导物来研究自诱导机制。当将³H-自诱导物添加到费氏弧菌或大肠杆菌的悬浮液中时，细胞内浓度与细胞外浓度相等。对于费氏弧菌，³H-自诱导物的平衡很快（在20秒内），并且超过90%的细胞内氚保留在未修饰的自诱导物中。当将含有³H-自诱导物的费氏弧菌或大肠杆菌细胞转移到不含自诱导物的缓冲液中时，85%至99.5%的放射性示踪剂从细胞中逸出，这取决于菌株。低至10 nM的自诱导物浓度就足以诱导，自诱导物的最大响应发生在约200 nM时。如果在诱导开始后将外部自诱导物浓度降低到10 nM以下，诱导反应就不会继续。基于这项研究，描述了一种自诱导模型，其中自诱导物与细胞的结合是通过简单扩散，并且自诱导物与其活性位点的结合是可逆的。
