Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Front Cell Infect Microbiol. 2019 Mar 27;9:72. doi: 10.3389/fcimb.2019.00072. eCollection 2019.
(Blastocladiomycota) is a facultative pathogenic chytrid that causes irreversible damage to some green microalgae. Specific attacks leading to culture collapse under different conditions have only been described in the lucrative microalga , while generating biomass for ketocarotenoid astaxanthin production, both indoors and outdoors. In order to manage the infection, parasite propagules (zoospores/amoeboid swarmers), the initiators of the disease, must be studied. Until now, no report on isolated propagules has been published. Here, we report on a reproducible method for the stimulation of propagule release and their isolation from fungal cultures in synthetic media and infected cultures, and we further studied their development under different conditions. The isolated propagules featured different spore morphotypes, with coatless spherical spores and amoeboid swarmers being the most dominant in the first pulse of propagule release in both cultures. Inoculating the pure propagules with the host, in both the presence and absence of nitrogen, resulted in epidemic development in both green and red cells; however, in red cells, the epidemic developed more quickly in the presence of nitrogen. Biologically non-active autoclaved host cells were used to distinguish the initial stages of recognition from more progressive stages of the epidemics; on these cells, propagules encysted but did not develop further. These results prove the existence of heat-stable recognition sites on the host and an obligatory signal transduction from the host to support fungal cyst development. The propagule isolation method described herein is a breakthrough that will enable researchers to study the influence of different substances on the propagules, specifically as the initiators of the infection, and thus assist in the management of chytrid diseases. Moreover, it will be useful in studying host-parasite recognition and, therefore, will increase our understanding of the multiple chytrid infections found in nature.
（芽枝霉目）是一种兼性致病的壶菌，会对一些绿藻造成不可逆转的损害。在有经济价值的微藻中，只有在不同条件下导致培养物崩溃的特定攻击才被描述过，而在室内和室外，这些藻类都被用来产生用于生产酮类胡萝卜素虾青素的生物质。为了对感染进行管理，必须研究寄生虫的繁殖体（游动孢子/变形体），它们是疾病的启动因子。到目前为止，还没有关于分离繁殖体的报道。在这里，我们报告了一种可重复的方法，用于刺激繁殖体的释放，并从真菌培养物和感染的培养物中分离它们，我们还进一步研究了它们在不同条件下的发育。分离的繁殖体具有不同的孢子形态，在两种培养物中，无壳的球形孢子和变形体是第一次繁殖体释放脉冲中最主要的形态。用宿主接种纯繁殖体，无论是在有氮还是无氮的情况下，都会导致绿藻和红藻的流行发展；然而，在有氮的情况下，红藻中的流行发展更快。生物上非活性的灭菌宿主细胞被用来区分识别的初始阶段和流行的更进展阶段；在这些细胞上，繁殖体包囊但不再进一步发育。这些结果证明了宿主上存在热稳定的识别位点，以及从宿主到支持真菌胞囊发育的信号转导的强制性。本文所述的繁殖体分离方法是一个突破，它将使研究人员能够研究不同物质对繁殖体的影响，特别是作为感染的启动因子，从而有助于控制壶菌病。此外，它将有助于研究宿主-寄生虫的识别，因此，将增加我们对自然界中发现的多种壶菌感染的理解。
