Strains of the cyanobacterial genera Calothrix and Rivularia isolated from the Baltic Sea display cryptic diversity and are distantly related to Gloeotrichia and Tolypothrix

Abstract

Strains of the cyanobacterial genus Calothrix display pronounced tapering filaments. These cyanobacteria are benthic, have a worldwide distribution and are among the most easily recognizable cyanobacterial genera. However, it is not clear whether cyanobacterial strains assigned to the genus Calothrix constitute a natural monophyletic group. We sequenced 16S rRNA genes from 42 cyanobacterial cultures and environmental samples belonging to the genus Calothrix, and the morphologically similar genera Rivularia, Gloeotrichia and Tolypothrix. Phylogenetic analysis of the 16S rRNA gene identified large sequence diversity among the Calothrix morphotype strains. Our results demonstrate that Calothrix, Gloeotrichia and Tolypothrix do not form a monophyletic group but instead display a high level of genetic diversity. The evolutionary distances between cyanobacteria, morphologically identified as Calothrix, suggest that they belong to at least five different genera. Our results also suggest that the genus Gloeotrichia is distantly related to the genus Calothrix. We found correlations between genetic grouping and morphology in redundancy analysis. However, morphology alone was not sufficiently reliable to distinguish strains from different 16S rRNA gene clusters. The high level of diversity that we observed confirms the hypothesis that the Rivulariaceae are species rich.

A novel cohabitation between two diazotrophic cyanobacteria in the oligotrophic ocean

“…BECID14 accession no. AM230671) (Sihvonen et al, 2007) to the subtropical South Pacific Ocean (i.e. BC001 accession no.…”

“…BC001), littoral zone of the Baltic Sea (Rivularia sp. XP16B) or from a small planktonic marine cyanobacterial colony in La Paz, Baja California (Rippka et al, 1979;Chacón et al, 2006;Sihvonen et al, 2007) (Figure 2a). In all of the aforementioned studies, the apparent habitat for the closest hits to hetDA were surface associated or aggregated organisms, findings that are consistent with the hetDA-Trichodesmium aggregate observed at Sta.…”

Abundance, viability and diversity of the indigenous microbial populations at different depths of the NEEM Greenland ice core

“…Because of the relative low similarity, we constructed another clone library from this ice core sample using the cyanobacteria specific 16S rRNA gene primers CYA106F-CYA781R (Nubel et al 1997). Analysis of 30 sequences showed highest similarity to the genus Calothrix, order Nostocales, also common in glacial environments (Sihvonen et al 2007;Komá rek et al 2012). …”

Silica Biomineralization of Calothrix-Dominated Biofacies from Queen's Laundry Hot-Spring, Yellowstone National Park, USA

“…However, little is known about their genetic diversity from the natural environment due to the lack of data pertaining to the biodiversity of Calothrix present across habitats (Sihvonen et al, 2007). The filamentous cyanobacterium Calothrix has been observed to occupy the upper 1-2 mm of microbial mats formed in silicadominated hot-springs across YNP (Walter, 1976).…”