Adaptation to temperature stress by Vibrio fischeri facilitates this microbe's symbiosis with the Hawaiian bobtail squid (Euprymna scolopes)

For microorganisms cycling between free-living and host-associated stages, where reproduction occurs in both of these lifestyles, an interesting inquiry is whether adaptation to stress during the free-living stage can impact microbial fitness in the host. To address this topic, the mutualism between the Hawaiian bobtail squid (Euprymna scolopes) and the marine bioluminescent bacterium Vibrio fischeri was utilized. Using microbial experimental evolution, V. fischeri was selected to low (8⁰C), high (34⁰C), and fluctuating temperature stress (8⁰C/34⁰C) for 2,000 generations. The temperatures 8⁰C and 34⁰C were the lower and upper growth limits, respectively. V. fischeri was also selected to benign temperatures (21⁰C and 28⁰C) for 2,000 generations, which served as controls. V. fischeri demonstrated significant adaptation to low, high, and fluctuating temperature stress. V. fischeri did not display significant adaptation to the benign temperatures. Adaptation to stressful temperatures facili...对于可在自由生活与宿主关联两种生活史阶段间循环，且两种模式下均可完成繁殖的微生物而言，一个颇具研究价值的科学问题是：自由生活阶段的逆境适应是否会影响其在宿主内的微生物适合度。 为解答该问题，本研究采用夏威夷短尾鱿鱼（Euprymna scolopes）与海洋生物发光细菌费氏弧菌（Vibrio fischeri）之间的互利共生体系作为研究模型。 借助微生物实验进化技术，我们将费氏弧菌分别置于低温（8℃）、高温（34℃）以及波动温度胁迫（8℃/34℃）条件下传代培养2000代。其中8℃与34℃分别为该菌的生长下限与上限温度。 同时，我们将费氏弧菌置于适宜温度（21℃与28℃）条件下传代培养2000代，以此作为对照实验组。 实验结果表明，费氏弧菌对低温、高温及波动温度胁迫均产生了显著的适应性演化；而在适宜温度条件下，该菌未出现显著的适应性变化。 对胁迫温度的适应性演化可促