Crenarchaeal community assembly and microdiversity in developing soils at two sites associated with deglaciation

Non-thermophilic Crenarchaeota are recognized as ubiquitous and abundant components of soil microbial communities. Previous studies of the foreland of the receding Rotmoosferner glacier in the Austrian Central Alps have demonstrated that crenarchaeal communities in soil at different stages of development are distinct from each other, with Group 1.1b crenarchaeal populations dominating throughout the successional gradient, while Group 1.1c crenarchaea are present in mature soils only. To determine whether this highly structured succession was unique to the Rotmoosferner glacier foreland, 1.1b and 1.1c communities were compared with those present along a successional gradient at Odenwinkelkees glacier, 125 km away, by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA reverse transcription polymerase chain reaction products. Similarities in community structure were observed; 1.1b communities were present throughout both successional gradients (though lacking the defined structure at Odenwinkelkees) and 1.1c communities were present only in mature soil. Comigration of bands on DGGE gels indicated that a number of similar crenarchaeal populations were present at both sites. To compare populations, and examine microscale diversity, 16S rRNA genes and complete 16S-23S internal transcribed spacer (ITS) regions representing six major band positions in DGGE analysis were amplified, cloned and sequenced and represented four 1.1b and two 1.1c lineages. The data provide no evidence of endemism, but large differences in the rate of sequence divergence in the ITS region (relative to that in 16S rRNA genes) were observed. Two of the 1.1b lineages (each possessing > 98% 16S rRNA gene similarity) had relatively long and highly divergent ITS sequences. In contrast, two other 1.1b and two 1.1c lineages (each possessing > 99% 16S rRNA gene similarity) exhibited markedly less variation in their respective 16S-23S ITS regions. The results reveal common patterns in the ecology and assembly of crenarchaeal communities in spatially separated soil systems and may indicate different evolutionary rates between soil crenarchaea lineages.