Archaeal diversity and community structure in a Swedish barley field: Specificity of the EK510R/(EURY498) 16S rDNA primer

The aim of this study was to analyze a total euryarchaeal community at DNA and RNA levels in a Swedish barley field with relation to soil depth (0-10 and 20-30 cm layers), soil fraction (bulk soil and rhizosphere) and time (August and November sample collection). Amplification of 16S rRNA gene using the archaeal universal A2F and Euryarchaea specific EK510R/(EURY498) primer pair, combined with denaturing gradient gel electrophoresis (DGGE), revealed distinct differences between rDNA and rRNA DGGE profiles. The soil depth, time, or rhizosphere effects did not significantly influence Archaeal community structure. Surprisingly, sequence analysis of DGGE-derived amplicons revealed the presence of Euryarchaea as well as uncultured soil Crenarchaea affiliated with group 1. In agreement, sequence comparison analyses showed that the majority of uncultured Crenarchaea group 1 had almost 100% sequence complementarity to the 3' end of the EK510R/(EURY498) primer. Therefore, we propose that EK510R/(EURY498R) is a universal archaeal primer rather than a Euryarchaea specific SSUrRNA primer. Hence, considerable care should be taken during application of this primer in studies of euryarchaeal biodiversity in soil environments.