Extending the ecological distribution of Desmonostoc genus: proposal of Desmonostoc salinum sp. nov., a novel Cyanobacteria from a saline–alkaline lake

Cyanobacteria is an ancient phylum of oxygenic photosynthetic microorganisms found in almost all environments of Earth. In recent years, the taxonomic placement of some cyanobacterial strains, including those belonging to the genus Nostoc sensu lato, have been reevaluated by means of a polyphasic approach. Thus, 16S rRNA gene phylogeny and 16S–23S internal transcribed spacer (ITS) secondary structures coupled with morphological, ecological and physiological data are considered powerful tools for a better taxonomic and systematics resolution, leading to the description of novel genera and species. Additionally, underexplored and harsh environments, such as saline–alkaline lakes, have received special attention given they can be a source of novel cyanobacterial taxa. Here, a filamentous heterocytous strain, Nostocaceae CCM-UFV059, isolated from Laguna Amarga, Chile, was characterized applying the polyphasic approach; its fatty acid profile and physiological responses to salt (NaCl) were also determined. Morphologically, this strain was related to morphotypes of the Nostoc sensu lato group, being phylogenetically placed into the typical cluster of the genus Desmonostoc. CCM-UFV059 showed identity of the 16S rRNA gene as well as 16S–23S secondary structures that did not match those from known described species of the genus Desmonostoc, as well as distinct ecological and physiological traits. Taken together, these data allowed the description of the first strain of a member of the genus Desmonostoc from a saline–alkaline lake, named Desmonostoc salinum sp. nov., under the provisions of the International Code of Nomenclature for algae, fungi and plants. This finding extends the ecological coverage of the genus Desmonostoc, contributing to a better understanding of cyanobacterial diversity and systematics

Phylogenetic insights into the diversity of homocytous cyanobacteria from Amazonian rivers

The Amazon Rainforest holds great tropical biodiversity, mainly because of its favourable climatic conditions. The high temperatures, luminosity and humidity coupled with the nutritional simplicity of cyanobacteria allow undiscovered diversity to flourish within this group of microorganisms. Some efforts to reveal this diversity have been attempted; however, most were focused on the microscopic observation of environmental samples without any genetic information. Very few studies focusing on morphological, ecological and molecular criteria have been conducted, and none have been devoted to homocytous cyanobacteria forms in Amazonia region. Therefore, the genetic relationships amongst strains retrieved from this ecosystem with regard to other environments from Brazil and the world have not been tested and, consequently, the Amazonian strains would naturally be assumed as novel to science. To examine these relationships, cultured homocytous cyanobacteria isolated from two Amazonian rivers (Amazonas and Solimões) were evaluated using a phylogenetic perspective, considering the 16S rRNA gene sequence. A total of eleven homocytous cyanobacterial strains were isolated. Morphologically, they were identified as Pseudanabaena, Leptolyngbya, Planktothrix and Phormidium, but genetically they were included in the typical clusters of Planktothrix, Pseudanabaena, Cephalothrix, Pantanalinema and Alkalinema. These three latter genera have been detected in other Brazilian ecosystems only (Pantanal, Atlantic Rainforest and Pampa), while those remaining have been extensively found in many parts of the world. The data provided here indicate that Amazonian rivers support a homocytous cyanobacterial diversity previously reported from other geographical and ecological environments

Heterocyte-forming cyanobacteria from Brazilian saline-alkaline lakes

Studies investigating the diversity of cyanobacteria from tropical environments are scarce, especially those devoted to the isolation and molecular characterization of the isolated strains. Among the Brazilian biomes, Pantanal has mainly been examined through microscopic observation of environmental samples, resulting in lists of morphotypes without any genetic information. Recently, two studies were conducted evaluating the morphologic and genetic diversity of cultured non-heterocytous cyanobacteria in this biome, which resulted in the separation and description of two novel genera. In order to complement the diversity of cultured cyanobacteria from saline-alkaline lakes in Pantanal, the present study is dedicated to the examination of cultured nitrogen-fixing heterocytous cyanobacteria from this extreme and underexplored environment. A total of fourteen cyanobacterial strains were isolated. According to morphological examination they belong to the order Nostocales and to the subsections IV.I and IV.II, according to the International Code of Nomenclature for Algae, Fungi and Plants and the Bergey’s Manual of Systematic Bacteriology, respectively. Phylogenetic evaluation of their 16S rRNA gene sequences resulted in the formation of five clusters. Among them, one is clearly related to the genus Anabaenopsis whilst the remaining clusters may represent new genetic lineages. These novel sequences aid in the delimitation of problematic groups, especially those containing sequences belonging to mixed genera. The application of both morphologic and phylogenetic studies has proven to be an important tool in resolving problematic groups in cyanobacteria systematics. This strategy is essential in order to detect novel cyanobacteria genera from other tropical environments

Pantanalinema gen. nov. and Alkalinema gen. nov.: novel pseudanabaenacean genera (Cyanobacteria) isolated from saline-alkaline lakes

International audienceThe genus Leptolyngbya Anagnostidis & Komárek (1988) was described from a set of strains identified as "LPP-group B". The morphology within this group is not particularly informative and underestimates the group's genetic diversity. In the present study, two new pseudanabaenacean genera related to Leptolyngbya morphotypes, Pantanalinema gen. nov. and Alkalinema gen. nov., are described under the provisions of the International Code of Nomenclature for algae, fungi, and plants, based on a polyphasic approach. Pantanalinema gen. nov. has sheaths and trichomes with slight gliding motility, which distinguish this genus from Alkalinema gen. nov., that possesses trichomes arranged in an ornate (interwoven) pattern. Pantanalinema and Alkalinema 16S rRNA gene sequences exhibited low identity compared to each other (≤ 91.6 %) and compared to other sequences from known pseudanabaenacean genera (≤ 94.3 and 93.7 %, respectively). In a phylogenetic reconstruction, six Pantanalinema and four Alkalinema sequences formed two separate and robust clades (99 % of bootstrap value), with the genera Oculatella and Phormidesmis, respectively, as the closest related groups. Intergenic spacer (ITS) sequences and secondary structures of Pantanalinema and Alkalinema did not correspond to any previous descriptions. The Pantanalinema and Alkalinema strains were able to survive and produce biomass at a range of pH values (4-11) and were also able to alter the culture medium to pH values ranging from 8.40-9.9. These data indicate that cyanobacterial communities in underexplored environments, such as the Pantanal wetlands, are promising sources of novel taxa