Monilinema gen. nov., a homocytous genus (Cyanobacteria, Leptolyngbyaceae) from saline–alkaline lakes of Pantanal wetlands, Brazil

Abstract

Cyanobacteria morphotypes with simple morphology, mainly thin filamentous homocytous strains, comprise a taxonomically complex group and represent a challenge in systematic studies. However, the polyphasic approach applied nowadays to investigate the cyanobacterial diversity has emerged as a powerful tool to undercover cryptic taxa and to set up a more natural classification system. Yet, studies exploring the cultured diversity of cyanobacteria from extreme tropical environments have paved the way to the discovery of new cyanobacteria taxa, enabling the description of Pantanalinema, Alkalinema, and Cephalothrix as novel genera from saline–alkaline lakes in Pantanal wetlands (Brazil). The present study investigated a set of cyanobacterial strains resembling Leptolyngbya morphotypes by means of its morphology, 16S ribosomal RNA (16S rRNA) phylogeny, and ITS secondary structures. Based on the shape and structure of their trichomes, the low levels of 16S rRNA identity coupled with the distinct phylogenetic position with regard to well establish genera, and their divergent ecological feature, these strains must be accommodated into a novel genus, named as Monilinema gen. nov., described under the provisions of the International Code of Nomenclature for algae, fungi, and plants. Accordingly, based on the singularity of the D1–D1′ and V3 helixes, these strains should be considered as a single species, Monilinema alkalinum.

Nodosilinea hunanesis sp. nov. (Prochlorotrichaceae, Synechococcales) from a Freshwater Pond in China Based on a Polyphasic Approach

“…It is difficult to put forward a morphological feature to distinguish the phylogenetically distinct taxa from the groups characterized by these thin filamentous cyanobacteria, such as Leptolyngbya. Many genetically distinct species have been classified as Leptolyngbya based only on morphology, prompting many taxonomists to attempt to split this polyphyletic group into new genera to better understand the classification of Leptolyngbya [7,20,21,[24][25][26][27][28][29][50][51][52]. Building the genus Nodosilinea [7] by splitting it from Leptolyngbya was another significant example, representing the effort to narrowly define the genus.…”