Local diversity of heathland Cercozoa explored by in-depth sequencing

ISME J. 2016 Oct;10(10):2488-97. doi: 10.1038/ismej.2016.31. Epub 2016 Mar 8.

Abstract

Cercozoa are abundant free-living soil protozoa and quantitatively important in soil food webs; yet, targeted high-throughput sequencing (HTS) has not yet been applied to this group. Here we describe the development of a targeted assay to explore Cercozoa using HTS, and we apply this assay to measure Cercozoan community response to drought in a Danish climate manipulation experiment (two sites exposed to artificial drought, two unexposed). Based on a comparison of the hypervariable regions of the 18S ribosomal DNA of 193 named Cercozoa, we concluded that the V4 region is the most suitable for group-specific diversity analysis. We then designed a set of highly specific primers (encompassing ~270 bp) for 454 sequencing. The primers captured all major cercozoan groups; and >95% of the obtained sequences were from Cercozoa. From 443 350 high-quality short reads (>300 bp), we recovered 1585 operational taxonomic units defined by >95% V4 sequence similarity. Taxonomic annotation by phylogeny enabled us to assign >95% of our reads to order level and ~85% to genus level despite the presence of a large, hitherto unknown diversity. Over 40% of the annotated sequences were assigned to Glissomonad genera, whereas the most common individually named genus was the euglyphid Trinema. Cercozoan diversity was largely resilient to drought, although we observed a community composition shift towards fewer testate amoebae.

MeSH terms

  • Biodiversity*
  • Cercozoa / classification
  • Cercozoa / genetics
  • Cercozoa / isolation & purification*
  • DNA Primers / genetics
  • DNA, Ribosomal / genetics
  • High-Throughput Nucleotide Sequencing
  • Phylogeny
  • Soil / parasitology*

Substances

  • DNA Primers
  • DNA, Ribosomal
  • Soil