Host-symbiont stress response to lack-of-sulfide in the giant ciliate mutualism

The mutualism between the thioautotrophic bacterial ectosymbiont
Candidatus Thiobius zoothamnicola and the giant ciliate Zoothamnium niveum
thrives in a variety of shallow-water marine environments with highly
fluctuating sulfide emissions. To persist over time, both partners must
reproduce and ensure the transmission of symbionts before the sulfide
stops, which enables carbon fixation of the symbiont and nourishment of
the host. We experimentally investigated the response of this mutualism to
depletion of sulfide. We found that colonies released some initially
present but also newly produced macrozooids until death, but in fewer
numbers than when exposed to sulfide. The symbionts on the colonies
proliferated less without sulfide, and became larger and more rod-shaped
than symbionts from freshly collected colonies that were exposed to
sulfide and oxygen. The symbiotic monolayer was severely disturbed by
growth of other microbes and loss of symbionts. We conclude that the
response of both partners to the termination of sulfide emission was
remarkably quick. The development and the release of swarmers continued
until host died and thus this behavior contributed to the continuation of
the association.

化能自养硫细菌外共生体（thioautotrophic bacterial ectosymbiont）*Candidatus Thiobius zoothamnicola*与大型纤毛虫*Zoothamnium niveum*之间的互利共生关系，可在硫化物排放高度波动的多种浅海海洋环境中存续。为实现长期稳定存在，双方共生伙伴必须在硫化物耗尽前完成繁殖并确保共生菌的传递——硫化物是共生菌进行碳固定、宿主获取营养的关键物质基础。本研究通过实验探究了该互利共生体系对硫化物耗竭的响应。结果显示，宿主群落会在死亡前释放部分初始留存及新产生的大虫体，但释放数量相较于暴露于硫化物环境时更少。在无硫化物条件下，群落表面的共生菌增殖能力显著减弱，且相较于新鲜采集的、同时暴露于硫化物与氧气环境中的共生菌，其个体更大、形态更偏向杆状。共生菌单层膜因其他微生物的增殖与共生菌的流失而遭到严重破坏。综上，双方共生伙伴对硫化物排放终止的响应速度极快。游动细胞的发育与释放会持续至宿主死亡，因此该行为有助于维持共生体系的长期存续。

搜集汇总

背景与挑战

背景概述

该数据集研究了巨型纤毛虫与硫氧化细菌共生体在硫化物缺乏条件下的应激反应，包含实验观察和测量数据。研究发现，硫化物缺乏导致共生体形态变化和宿主行为改变，共生体单层受到干扰。