Rapid TaqMan-Based Quantification of Chlorophylld-Containing Cyanobacteria in the Genus Acaryochloris

Abstract

ABSTRACTReports of the chlorophyll (Chl)d-containing cyanobacteriumAcaryochlorishave accumulated since its initial discovery in 1996. The majority of this evidence is based on amplification of the gene coding for the 16S rRNA, and due to the wide geographical distribution of these sequences, a global distribution ofAcaryochlorisspecies was suggested. Here, we present a rapid, reliable, and cost-effective TaqMan-based quantitative PCR (qPCR) assay that was developed for the specific detection ofAcaryochlorisspecies in complex environmental samples. The TaqMan probe showed detection limits of ∼10 16S rRNA gene copy numbers based on standard curves consisting of plasmid inserts. DNA from fiveAcaryochlorisstrains, i.e., MBIC11017, CCMEE5410, HICR111A, CRS, and Awaji-1, exhibited amplification efficiencies of >94% when tested in the TaqMan assay. When used on complex natural communities, the TaqMan assay detected the presence ofAcaryochlorisspecies in four out of eight samples of crustose coralline algae (CCA), collected from temperate and tropical regions. In three out of these TaqMan-positive samples, the presence of Chldwas confirmed via high-performance liquid chromatography (HPLC), and corresponding cell estimates ofAcaryochlorisspecies amounted to 7.6 × 101to 3.0 × 103per mg of CCA. These numbers indicate a substantial contribution of Chld-containing cyanobacteria to primary productivity in endolithic niches. The new TaqMan assay allows quick and easy screening of environmental samples for the presence ofAcaryochlorisspecies and is an important tool to further resolve the global distribution and significance of this unique oxyphototroph.