Morphological and molecular characterization of cyanobacterial isolates from the mouth of the Amazon River

Abstract

The Amazon region contains a great diversity of species, and the Amazon River basin accounts for almost 20% of all the freshwater in the world. Despite the favorable environmental conditions in this region, little is known about the cyanobacterial diversity of this waterbody, especially at the mouth of the river. In this paper, we used the polyphasic approach to identify 14 cyanobacterial strains isolated in the Amazon River on the inlet site from a drinking water supply located close to the river mouth. The isolated strains were characterized based on morphology, behavior in culture, 16S rRNA gene sequencing, phylogenetic analysis and potential for toxin production. The isolated strains belong to seven different genera, namely, Alkalinema, Cephalothrix, Limnothrix, Leptolyngbya, Phormidium, Pseudanabaena and an unidentified Nostocales taxa that may represent a new genus. Strikingly, there were no new species, nor detection of gene clusters associated with cyanotoxin production. However, the phylogenetic placements of the Amazonian strains of Limnothrix and Pseudanabaena provide new insight into the taxonomy of these genera, reinforcing the need for taxonomic revision.

First Detection of Microcystin-LR in the Amazon River at the Drinking Water Treatment Plant of the Municipality of Macapá, Brazil

“…Ten cyanobacteria taxa were identified in the microscopic monitoring of raw water from the Amazon River: Limnothrix planctonica, Alkalinema pantanalense, Leptolyngbya sp., Pseudanabaena sp., Raphidiopsis sp., Anabaena sp., Dolichospermum sp., Geitlerinema splendidum , Cephalothrix lacustris , and an unidentified cyanobacteria named Morphoespecies 1. The most frequent taxa were identified by polyphasic taxonomy [22], whereas the other taxa were identified only by morphology (microscopy). All of the cyanobacteria had filamentous forms.…”

“…To link a species to MC-LR production, it would be necessary to isolate the cyanobacteria and then search for the cyanotoxin-related marker in each cyanobacterial strain [30]. This process has already been performed with strains isolated from the water intake of the DWTP of Macapá, but none of these strains presented the potential for the production of microcystin, saxitoxin, anatoxin, or cylindrospermopsin [22]. In any case, the toxin (chemical) was detected by ELISA and LC-MS methods, indicating that some “still unknown” Amazonian cyanobacterial strain is producing such a metabolite.…”

“…For all these reasons, there are no studies available on cyanobacterial density and cyanotoxin production in Amapá. Even cyanobacterial taxonomic studies are scarce [22].…”

Hydrodynamic Modeling and Simulation of Water Residence Time in the Estuary of the Lower Amazon River

“…In other words, the longer the water remains in the control volume, the greater the likelihood of passive flow agents remaining in the body of water. However, depending on the passive agent in the flow, this characteristic can be positive, for example, nutrients to feed the aquatic biota, or negative, to disperse pollutants [18,22,23,35,[43][44][45].…”

“…Although the present contribution helps better understanding the mechanisms involved in Rt quantification, new scientific efforts must be made to provide information about the functioning of these aquatic ecosystems in the Amazonian estuarine complex. It is still necessary to deepen the subject, asthe ecological relevance of its aquatic biodiversity richness are still potentially unknown [18], because studies carried out in HZs in lower Amazon River are very rare, but these processes still continue and are naturally dependent on Rt.…”