Cyanobacterial Diversity in Microbial Mats from the Hypersaline Lagoon System of Araruama, Brazil: An In-depth Polyphasic Study

Abstract

Microbial mats are complex, micro-scale ecosystems that can be found in a wide range of environments. In the top layer of photosynthetic mats from hypersaline environments, a large diversity of cyanobacteria typically predominates. With the aim of strengthening the knowledge on the cyanobacterial diversity present in the coastal lagoon system of Araruama (state of Rio de Janeiro, Brazil), we have characterized three mat samples by means of a polyphasic approach. We have used morphological and molecular data obtained by culture-dependent and -independent methods. Moreover, we have compared different classification methodologies and discussed the outcomes, challenges, and pitfalls of these methods. Overall, we show that Araruama's lagoons harbor a high cyanobacterial diversity. Thirty-six unique morphospecies could be differentiated, which increases by more than 15% the number of morphospecies and genera already reported for the entire Araruama system. Morphology-based data were compared with the 16S rRNA gene phylogeny derived from isolate sequences and environmental sequences obtained by PCR-DGGE and pyrosequencing. Most of the 48 phylotypes could be associated with the observed morphospecies at the order level. More than one third of the sequences demonstrated to be closely affiliated (best BLAST hit results of ≥99%) with cyanobacteria from ecologically similar habitats. Some sequences had no close relatives in the public databases, including one from an isolate, being placed as “loner” sequences within different orders. This hints at hidden cyanobacterial diversity in the mats of the Araruama system, while reinforcing the relevance of using complementary approaches to study cyanobacterial diversity.

Morphological and Molecular Identification of Microcystin-Producing Cyanobacteria in Nine Shallow Bulgarian Water Bodies

“…This approach includes different molecular techniques and is increasingly employed for the analysis of environmental samples (e.g., [12][13][14][15][16][17][18][19]). However, the assignment of taxa to sequences is often a challenge in molecular-based classification methods applied to environmental samples [19,20]. For early detection of potentially toxigenic cyanobacteria and cyanotoxins, rapid, reliable, and economically effective molecular approaches based on a PCR (polymerase chain reaction) targeting genes involved in the biosynthesis of cyanotoxins have been developed in the past 15 years [21].…”

The Effects of Salts and Osmoprotectants on Enzyme Activities of Fructose-1,6-biphosphate Aldolases in a Halotolerant Cyanobacterium, Halothece sp. PCC 7418

“…4 EDTA was added to a final concentration of 5 mM. 5 This activity shows CI-FBA activity in the Halothece extract. 6 Not detected.…”

“…Hereafter, we refer to Halothece 7418 CI-FBA and CII-FBA as H2846 and H2847, respectively, according to a previous report [4]. Halothece 7418, formerly identified as Aphanothece halophytica [5], is a halotolerant cyanobacterium, which was originally isolated from the Dead Sea, that can grow under high salinity concentrations of up to 3.0 M NaCl and an alkaline pH of 11 [6]. This strain is a remarkable example of cyanobacterial tolerance to high salt concentrations.…”

Introduction: Recent developments in cyanobacterial research with special reference to aquatic habitats, molecular ecology and phylogenetic taxonomy

“…The fact that cyanobacterial taxonomy is in the middle of vigorous change presents a barrier for successful application of next generation sequencing (NGS) methods to investigate the biodiversity of cyanobacteria. The assignment of taxa to sequences is often a challenge in molecular-based classification methods applied to environmental samples (Ramos et al, 2017). The studies published within the current special section have attempted to move forward some of the issues mentioned above and provide future prospects for research in cyanobacterial 1 Scientific meetings are held every third year and organized by the International Association for Cyanophyte/Cyanobacteria research (IAC), a group of international scientists founded in 1958 in Austria in order to optimize standards of taxonomic and ecological studies of this prokaryotic group of photosynthetic oxygenic organisms.…”