Floral nectar of animal-pollinated plants is commonly infested with microorganisms,
yet little is known about the microorganisms inhabiting the floral nectar
of orchids. In this study, we investigated microbial communities occurring
in the floral nectar of seven Epipactis (Orchidaceae) species. Culturable bacteria
and yeasts were isolated and identified by partially sequencing the small subunit
(SSU) ribosomal RNA (rRNA) gene and the D1/D2 domains of the large subunit
(LSU) rRNA gene, respectively. Using three different culture media, we
found that bacteria were common inhabitants of the floral nectar of Epipactis.
The most widely distributed bacterial operational taxonomic units (OTUs) in
nectar of Epipactis were representatives of the family of Enterobacteriaceae, with
an unspecified Enterobacteriaceae bacterium as the most common. In contrast
to previous studies investigating microbial communities in floral nectar, very
few yeast species (mainly of the genus Cryptococcus) were observed, and most
of them occurred in very low densities. Total OTU richness (i.e., the number of
bacterial and yeast OTUs per orchid species) varied between 4 and 20. Cluster
analysis revealed that microbial communities of allogamous species differed
from those of autogamous and facultatively autogamous species. This study
extends previous efforts to identify microbial communities in floral nectar and
indicates that the floral nectar of the orchids investigated mainly contained bacterial
communities with moderate phylogenetic diversity