Increases in seawater temperature can cause coral bleaching through loss of symbiotic algae (dinoflagellates of the family Symbiodiniaceae). Corals can recover from bleaching by recruiting algae into host cells from the residual symbiont population or from the external environment. However, the high coral mortality that often follows mass-bleaching events suggests that recovery is often limited in the wild. Here, we examine the effect of pre-exposure to heat stress on the capacity of symbiotic algae to infect cnidarian hosts using the Aiptasia (sea-anemone)-Symbiodiniaceae model system. We found that the symbiont strain Breviolum sp. CS-164 (ITS2 type B1), both free-living and in symbiosis, loses the capacity to infect the host following exposure to heat stress. This loss of infectivity is reversible, however, a longer exposure to heat stress increases the time taken for reversal. Under the same experimental conditions, the loss of infectivity was not observed in another strain Breviolum psygmophilum CCMP2459 (ITS2 type B2). Our results suggest that recovery from bleaching can be limited by the loss of symbiont infectivity following exposure to heat stress.

海水温度升高会通过共生藻类（共生菌科的鞭毛藻）的损失而引起珊瑚白化。通过将藻类从残留的共生菌种群或外部环境中募集到宿主细胞中，珊瑚可以从漂白中恢复。但是，大规模白化事件后珊瑚死亡率很高，这表明在野外恢复通常受到限制。在这里，我们使用Aiptasia（海葵）-Symbiodiniaceae模型系统检查预暴露于热胁迫下对共生藻类感染CN宿主的能力的影响。我们发现共生菌株Breviolumsp。自由活动和共生的CS-164（ITS2类型B1）在暴露于热应激后丧失了感染宿主的能力。这种传染性的丧失是可逆的，但是，长时间暴露于热应激会增加逆转所需的时间。在相同的实验条件下，另一株短生嗜热菌CCMP2459（ITS2 B2型）未观察到传染性的丧失。我们的结果表明，从漂白中恢复可能受到暴露于热应激后共生菌感染力丧失的限制。