Morphological, biochemical and molecular characterization of Anabaena, Aphanizomenon and Nostoc strains (Cyanobacteria, Nostocales) isolated from Portuguese freshwater habitats

Abstract

Studies of cyanobacterial nostocacean taxa are important to the global scientific community, mainly because a significant number of beneficial strains that belong to the order Nostocales fix atmospheric nitrogen, thus contributing to the fertility of agricultural soils worldwide, while others behave as nuisance microorganisms in aquatic ecosystems due to their involvement in toxic bloom events. However, in spite of their ecological importance and environmental concerns, their identification and taxonomy are still problematic and doubtful, often being based on current morphological and physiological studies, which generate confusing classification systems and usually vary under different conditions. Therefore, the present research aimed to investigate through a polyphasic approach differences in morphological, biochemical and genotypic features of three nostocacean cyanobacterial strains isolated from central-western Portuguese shallow freshwater bodies. Morphometric, genetic (16S rRNA, nifH and hetR fragments) and biochemical (fatty acid methyl ester; FAME profiles) data were used to characterize the strains. Morphological analysis and sequencing of 16S rRNA fragments showed that the strains belonged to Anabaena cylindrica (UTAD_A212), Aphanizomenon gracile (UADFA16) and Nostoc muscorum (UTAD_N213) species. These strains showed clear distinct morphological and genetic features, allowing easy allocation to their respective genera. The same happened by using partial sequences of hetR and nifH genes, in spite of the scarcity of deposited sequences. Biochemical characterization showed that the FAME profiles obtained were consistent with both morphological and molecular analyses. It was suggested that the ratio of monounsaturated to polyunsaturated FAMEs, together with the unsaturation index, could be used as genus-specific chemotaxonomic biomarkers.

Cyanobacteria in Scandinavian coastal waters — A potential source for biofuels and fatty acids?

“…In our study, ratios of SAFA/MUFA + PUFA (Table 2) in D. lemmermannii under f/2 and N depletion and in A. flos-aquae under N depletion are comparable to ratios obtained by Galhano et al [48].…”

“…FA results from the present study (Table 2) and those obtained in Li et al [52] suggest that FA seem to be more sensitive to environmental parameters than anticipated, leading to consequences in the FA use as characteristic markers. Consequently, ratios between MUFA, PUFA and SAFA seem to be highly variable for different cyanobacterial species [48], but appear rather constant within certain species under comparable environmental conditions [53]. The amount of 18:1(n-7) in D. lemmermannii and A. flos-aquae throughout the treatments is far higher compared to N. spumigena.…”

“…Results are related to the overall TFA contents (Table 2) and indicate how the ratios of SAFA, MUFA and PUFA may develop under certain nutrient conditions. Galhano et al [48] observed SAFA of 61.7%, MUFA of 24.8% and PUFA of 13.5% in Aphanizomenon gracile and SAFA of 46.3%, MUFA of 17.7% and PUFA of 36.0% in Anabaena cylindrica. The results for both species are, in terms of SAFA, similar to our species Table 3 Pigment concentration [μg mm flos-aquae and 15:1 in Anabaena affinis; these FA could not be identified in our analysis but seem to be of less taxonomic value [50].…”

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“…Moreover, due to their high biomass accumulation capacity, they have the potential to be used in many biotechnological applications like biofuel (biogas, bioethanol, butanol and biodiesel) productions (Sarsekeyeva et al, 2014). Furthermore, they have the potential to produce many bioactive compounds, proteins, pigments and polysaccharides (Galhano et al, 2011). Cyanobacteria as being a global primary producer requires water, carbon dioxide, inorganic substances and light for the maintenance of their life cycle.…”

Identificación y caracterización molecular de cianobacterias tropicales de los géneros Nostoc, Calothrix, Tolypothrix y Scytonema (Nostocales: Nostocaceae), con posible potencial biotecnológico

“…Se reportan estudios de caracterización molecular y morfológica de cianobacterias del orden Nostocales en suelos minerales y en regiones como Australia, el continente asiático, europeo y Sur América (Galhano et al, 2011;Arima et al, 2012;Quesada & Vincent, 2012;Silva & de Jesús, 2013).…”