Reassessment of the cyanobacterial family Microchaetaceae and establishment of new families Tolypothrichaceae and Godleyaceae

Abstract

The family Microchaetaceae is a large group of heterocytous cyanobacteria, whose members bear typical morphological features of uniseriate heteropolar filaments never terminated by thin hairs and with simple false branching. However, phylogenetic analyses of the gene for 16S rRNA showed that members of this traditionally morphologically delimited family form several distant groups and therefore the current concept is hereafter indefensible. In this study, we provide reassessment of the status of the family Microchaetaceae based on morphology, ecology, biogeography, and phylogeny of 16S rRNA gene. Thorough examination of strains of the nominate genus Microchaete revealed their affiliation to two groups, Nostocaceae and Rivulariaceae, and their distant position to other traditional members of Microchaetaceae such as Tolypothrix, Hassallia, and Coleodesmium. To reflect the phylogenetic relationships and to accommodate members of the traditional family Microchaetaceae that are clearly not related to any of the Microchaete representatives, we propose establishment of two new families, Tolypothrichaceae and Godleyaceae. Based on both molecular and morphological evidence, we also provide a description of three new species of the genus Fortiea.