Department of Environmental Science, Toho University, Miyama 2-1-1, 275-8510 Funabashi, Chiba, Japan.
Microb Ecol. 2012 Feb;63(2):358-68. doi: 10.1007/s00248-011-9913-9. Epub 2011 Jul 30.
Freshwater fungi have received little attention by scientific research in recent years, especially fungi of the pelagic zone. Recently, parasitic fungi, termed chytrids, have been found to play important roles in aquatic food webs. Yet, the diversity and community structure of planktonic fungi including chytrids are not well studied. In this study, we examined the temporal fluctuations of freshwater fungi, including chytrids, in Lake Inba by using molecular techniques of denaturing gradient gel electrophoresis (DGGE). DGGE profiles, and associated sequence analysis, indicated that chytrids were present on all sampling dates from May to October (n = 12). In addition, analysis showed that a large proportion of the sequences belonged to chytrids of both parasitic and saprotrophic species. This finding was supported by microscopic observations using Calcofluor white to stain chytrids infecting various phytoplankton species. The percentages of infection by chytrids on two dominant diatom species, Aulacoseira granulata and Aulacoseira ambigua, showed a similar seasonal pattern in the DGGE band profiles. From the phylogenetic analysis and microscopic identification, the chytrids infecting the two diatoms are likely to be affiliated to Chytriomyces sp. and Zygorhizidium sp.. This is the first study to show that DGGE is a useful preliminary approach for examining the diversity of planktonic fungi including chytrids. Our results indicate both parasitic and saprotrophic chytrids are a significant component of freshwater fungi inhabiting the pelagic zone of Lake Inba, Japan. Further modification of DGGE, together with new molecular techniques and microscopic observation, would reveal the hidden diversity and ecological significance of planktonic fungi in aquatic ecosystems.
近年来，淡水真菌在科学研究中受到的关注较少，尤其是浮游带的真菌。最近，寄生真菌（称为壶菌）被发现对水生食物网起着重要作用。然而，浮游真菌（包括壶菌）的多样性和群落结构尚未得到很好的研究。在这项研究中，我们通过使用变性梯度凝胶电泳（DGGE）等分子技术，研究了入间湖淡水真菌（包括壶菌）的时间波动。DGGE 图谱和相关的序列分析表明，从 5 月到 10 月（共 12 次采样）的所有采样日期都存在壶菌。此外，分析表明，很大一部分序列属于寄生和腐生种的壶菌。这一发现得到了使用 Calcofluor white 染色感染各种浮游植物的壶菌的显微镜观察的支持。在 DGGE 带图谱中，两种优势硅藻（Aulacoseira granulata 和 Aulacoseira ambigua）上的壶菌感染率表现出相似的季节性模式。从系统发育分析和显微镜鉴定来看，感染这两种硅藻的壶菌可能属于 Chytriomyces sp. 和 Zygorhizidium sp.。这是首次表明 DGGE 是一种有用的初步方法，可用于检查包括壶菌在内的浮游真菌多样性的研究。我们的结果表明，寄生和腐生壶菌是栖息在日本入间湖浮游带的淡水真菌的重要组成部分。进一步改进 DGGE 技术，并结合新的分子技术和显微镜观察，将揭示水生生态系统中浮游真菌的隐藏多样性和生态意义。
