悉生条件下3株嗜盐古菌对卤虫生长及其抗弧菌感染的影响

嗜盐古菌存在于高盐水体中,是高盐环境微生物种群的重要组成部分。本研究利用从日晒盐场结晶池卤水中分离得到的3株红色嗜盐古菌,分别命名为Haloarcula sp.HG-1、Haloferax sp.KN-4和Halorubrum sp.IT-5。采用悉生实验系统,探讨不同盐度(30、100和150)条件下3株古菌能否作为卤虫(Artemia)的唯一饵料,并比较其作为饵料对卤虫存活、生长和抗鳗弧菌(Vibrio anguillarum)感染能力的影响。结果表明,在盐度30的悉生系统中,投喂3株古菌组卤虫存活率和体长均保持较高水平;鳗弧菌攻毒条件下,卤虫存活率有所下降,其中投喂Haloferax sp.KN-4菌株组卤虫抗鳗弧菌感染能力最强。正常和攻毒条件下,在盐度100和盐度150悉生系统中分别投喂3株古菌,卤虫均保持较高存活率和体长,其中投喂Haloarcula sp.HG-1菌株组卤虫具有最高存活率和最长体长,但攻毒组卤虫存活率和生长普遍优于未攻毒组,这可能与高盐条件下V.anguillarum毒力下降有关。本研究利用"卤虫-古菌"悉生实验系统,证实了3株嗜盐古菌均可作为卤虫的唯一饵料,为卤虫提供营养;利用"卤虫-古菌-致病菌"攻毒实验系统,证实3株嗜盐古菌均可以增强卤虫抗鳗弧菌感染能力。本研究结果为研究古菌在高盐环境食物链中的作用提供了基础数据。

Comparison of three halophilic archaea on growth and Vibrio anguillarum challenge resistance of Artemia under gnotobiotic conditions

Halophilic archaea inhabit hypersaline environments and are an important component of microbial communities. High salt concentration enable archaea cells accumulating bioactive compounds with unique molecular structure and biochemical functions. Therefore, archaea are also important resources for commercial application. As a non-selective filter feeder, Artemia plays an important role in the food chains of hypersaline environments, even though the high salinity of such environments limits the complexity of the food web. It is well known that Artemia populations are supported by rich phytoplankton communities. Recently, the important role of microbiota in the life cycle of Artemia and in hypersaline food chain has drawn much interest. The present study focused on archaea, which are important but often neglected microorganisms that comprise the third domain of life. Their cells contain ether-linked membrane lipids, instead of the ester-lipids found in bacterial and eukaryotic cells. Archaea are considered unsuitable as a food resource for aquatic animals, since the ether-linked lipids are difficult to digest and do not provide the essential fatty acids needed to support animal growth and survival.
Three red halophilic archaea strains (Haloarcula sp. HG-1, Haloferax sp. KN-4, and Halorubrum sp. IT-5) were isolated from a crystallization pond of a solar saltworks. The gnotobiotic Artemia culture system was used to determine whether Artemia can survive on a sole diet of halophilic archaea and to investigate the effect of halophilic archaea on Artemia survival, growth, and resistance to Vibrio anguillarum at different salinities (30, 100, and 150, respectively). The archaea cells were cultured at 100 and 150, with modified CM medium. All three halophilic archaea strains grew faster at 150, and under the condition of salinity 100, the growth of Haloarcula sp. HG-1 and Haloferax sp. KN-4 is better than that of Halorubrum sp. IT-5.
The Artemia that were fed the three archaeal strains exhibited higher survival rates and body lengths when cultured at salinity 30 than when cultured at salinity 100 or salinity 150. The greatest survival rate was observed when the Artemia were fed Halorubrum sp. IT-5 at salinity 100, whereas the greatest body length was observed when the Artemia were fed Haloarcula sp. HG-1 at salinity 100. When challenged with V. anguillarum, the survival rate of all groups decreased, but the greatest survival rate and body length were observed when the Artemia were fed Haloferax sp. KN-4. At salinity 100 and 150, all the Artemia groups exhibited high rates of survival and growth. However, the V. Anguillarum-challenged Artemia generally exhibited greater survival rates and body lengths than the unchallenged groups, thereby indicating that the virulence of V. anguillarum decreased at high salinity and the cells could be ingested as food by Artemia.
In conclusion, using a gnotobiotic Artemia-archaea experimental system, the present study provides evidence that Artemia can survive and grow on a sole diet of halophilic archaea over a wide range of salinities (30-150). In addition, halophilic archaea can improve Artemia survival and resistance against V. anguillarum, a pathogen that frequently occurs in marine aquaculture systems. These results provide a basis for investigating the role of archaea in the food chains of hypersaline environments.