Quantifying microbial diversity: Morphotypes, 16S rRNA genes, and carotenoids of oxygenic phototrophs in microbial mats

We quantified the diversity of oxygenic phototrophic microorganisms present in eight hypersaline microbial mars on the basis of three cultivation-inde pendent approaches. Morphological diversity was studied by microscopy. The diversity of carotenoids was examined by extraction from mat samples and hi gh-pressure liquid chromatography analysis. The diversity of 16S rRNA genes from oxygenic phototrophic microorganisms was investigated by extraction o f total DNA from mat samples, amplification of 16S rRNA gene segments from cyanobacteria and plastids of eukaryotic algae by phylum-specific PCR, and sequence-dependent separation of amplification products by denaturing-gradi ent gel electrophoresis. A numerical approach was introduced to correct for crowding the results of chromatographic and electrophoretic analyses. Dive rsity estimates typically varied up to twofold among mats. The congruence o f richness estimates and Shannon-Weaver indices based on numbers and propor tional abundances of unique morphotypes, 16S rRNA genes, and carotenoids un veiled the underlying diversity of oxygenic phototrophic microorganisms in the eight mat communities studied.