Lauer Antje, Simon Mary Alice, Banning Jenifer L, Lam Brianna A, Harris Reid N
Department of Biology, James Madison University, Harrisonburg, VA, USA.
ISME J. 2008 Feb;2(2):145-57. doi: 10.1038/ismej.2007.110. Epub 2007 Dec 13.
Among the microbiota of amphibian skin are bacteria that produce antifungal compounds. We isolated cutaneous bacteria from the skins of three populations of the nest-attending plethodontid salamander Hemidactylium scutatum and subsequently tested the bacterial isolates against two different fungi (related to Mariannaea elegans and Rhizomucor variabilis) that were obtained from dead salamander eggs. The culturable antifungal bacteria were phylogenetically characterized based on 16S rRNA phylogeny, and belonged to four phyla, comprising 14 bacterial families, 16 genera and 48 species. We found that about half of the antifungal bacterial genera and families were shared with a related salamander species, but there was virtually no overlap at the species level. The proportion of culturable antifungal bacterial taxa shared between two large populations of H. scutatum was the same as the proportion of taxa shared between H. scutatum and Plethodon cinereus, suggesting that populations within a species have unique antifungal bacterial species. Approximately 30% of individuals from both salamander species carried anti-M. elegans cutaneous bacteria and almost 90% of P. cinereus and 100% of H. scutatum salamanders carried anti-R. variabilis cutaneous bacteria. A culture independent method (PCR/DGGE) revealed a shared resident bacterial community of about 25% of the entire resident bacterial community within and among populations of H. scutatum. Thus, the culturable antifungal microbiota was far more variable on salamander skins than was the bacterial microbiota detected by PCR/DGGE. The resident cutaneous antifungal bacteria may play an important role in amphibians' innate defense against pathogens, including the lethal chytrid fungus Batrachochytrium dendrobatidis.
在两栖动物皮肤的微生物群中，有些细菌能产生抗真菌化合物。我们从三种巢居的无肺螈科蝾螈——北美东部细趾蟾（Hemidactylium scutatum）的皮肤中分离出皮肤细菌，随后针对从死亡蝾螈卵中获取的两种不同真菌（与秀丽玛丽安娜霉（Mariannaea elegans）和可变根毛霉（Rhizomucor variabilis）相关）对分离出的细菌进行了测试。基于16S rRNA系统发育对可培养的抗真菌细菌进行了系统发育特征分析，它们属于四个门，包括14个细菌科、16个属和48个种。我们发现，大约一半的抗真菌细菌属和科与一种相关蝾螈物种共有，但在物种水平上几乎没有重叠。北美东部细趾蟾两个大种群之间共享的可培养抗真菌细菌分类单元比例，与北美东部细趾蟾和灰红背无肺螈（Plethodon cinereus）之间共享的分类单元比例相同，这表明一个物种内的种群拥有独特的抗真菌细菌物种。两种蝾螈物种中约30%的个体携带抗秀丽玛丽安娜霉的皮肤细菌，而灰红背无肺螈近90%的个体和北美东部细趾蟾100%的个体携带抗可变根毛霉的皮肤细菌。一种非培养方法（PCR/DGGE）显示，北美东部细趾蟾种群内部和种群之间共享的常驻细菌群落约占整个常驻细菌群落的25%。因此，蝾螈皮肤上可培养的抗真菌微生物群比通过PCR/DGGE检测到的细菌微生物群变化大得多。常驻皮肤抗真菌细菌可能在两栖动物对病原体（包括致命的蛙壶菌（Batrachochytrium dendrobatidis））的先天防御中发挥重要作用。
