Dominance of potentially toxic cyanobacteria on the waterfront of Santarém, Tapajós River, Brazilian Amazon

The present study carried out an evaluation of physicochemical parameters of waters from the low Tapajós river, and the identification of dominant cyanobacteria in the blooms that occurred in a transect bordering the Santarém city waterfront, in the State of Pará, Brazilian Amazon. Five (5) sampling stations were selected along the waterfront (RT-E1, RT-E2, RT-E3, RT-E4, RTE5), where water, phytoplankton and general environmental data were collected during 10 field campaigns, at intervals of 48 hours, between January 13th and 31st 2015, at the very beginning of the rainy season. The sample collections were conducted at an average depth of 2.3 meters, always early in the morning and following the procedures of the Collection and Preservation Guide and Water Samples of the Brazilian National Water Agency. Quantitative analyses of the physicochemical parameters were performed, namely: hydrogenionic potential (pH); water temperature (ºC); turbidity (NTU); electrical conductivity (EC); Dissolved Oxygen (DO); nitrate (NO-3); nitrite (NO-2); ammonium ion (NH4); ammonia (NH3); orthophosphate (PO43-); phosphate (P2O5); phosphorus (P); iron (Fe) and chlorophyll a (Chlo a). General descriptive statistics were calculated. For counting of individuals, the efficiency was superior to 80%, reaching a total of 3,910 individuals, from which 38% are species of the Cyanophyta division. The following species were dominant: Synechocystis aquatilis Microcystis aeruginosa, Dolichospermum spiroides, Nostoc sp. Except for S. aquatilis, all the others are cyanotoxin producers that can be released into the water after cell disruption. The presence of cyanobacteria potentially producing cyanotoxins is of concern and should be considered in the diagnosis of waterborne diseases, such as hepatic infections that affect the riverine population of the Tapajós river.

Microcystins production and antibacterial activity of cyanobacterial strains of Synechocystis, Synechococcus and Romeria isolated from water and coral reef organisms of Brazilian coast

Cyanobacteria are widely distributed in terrestrial, freshwater and marine environments, and over the past decades have been recognized as a powerful source of bioactive compounds. In this study, some cyanobacterial strains were isolated from samples of seawater, brackish water and tissue of reef benthic invertebrates (zoanthid Protopalythoa variabilis, the sponges Cynachrella sp. and Haliclona sp., the coral Siderastrea stellata, and ascidians), collected at the states of Paraíba and Rio Grande do Norte (Northeast of Brazil), during the period between July 2010 and February 2014. After standard isolation methods, the cultivation of the strains was carried out in acclimatized culture chamber (25 °C) under constant aeration, for 15 days at 12-hour photoperiod, using Conway and BG11 media made with filtered seawater. After ethanolic and methanolic extracts, the strains were analysed for the microcystin production by the ELISA technique and for the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa by the agar well diffusion method. The detection of the mcyB gene, one of the genes related to the microcystin synthesis, was done by the Polymerase Chain Reaction (PCR) technique. The majority of the eighteen cyanobacterial strains belonged to Synechococcaceae Family. The genera of Synechocystis, Synechococcus and Romeria were represented by ten, six and two strains, respectively. The production of microcystins was observed in five strains belonging to the genus Synechocystis. The presence of mcyB gene was detected in 12 strains of cyanobacteria: Synechocystis (three strains), Synechococcus (six strains) and Romeria (two strains). Only one strain (Synechocystis aquatilis) showed both the microcystin production and the mcyB gene presence. The antibacterial activity was observed for one strain of Romeria gracilis, one strain of Synechocystis aquatilis and two strains of Synechococcus sp. The ethanolic extracts of R. gracilis strain and two Synechococcus spp. strains inhibited the growth of P. aeruginosa. Among methanolic extracts of cyanobacteria, only one strain of S. aquatilis showed activity against S. aureus, and one R. gracilis strain against P. aeruginosa. Some cyanobacterial strains studied were positive for the microcystin production and antibacterial activity against pathogenic bacteria S. aureus and P. aeuruginosa, and may be further explored for additional biotechnological applications.

Cambios fisiológicos, bioquímicos y ultraestructurales inducidos por el campo magnético en Synechocystis aquatilis

Los estudios ultraestructurales en Synechocystis se centran principalmente en el ficobilisoma (PBS); sin embargo existen pocos informes sobre el efecto del campo magnético a este nivel. El objetivo de la investigación fue examinar los principales efectos fisiológicos, cambios bioquímicos y ultraestructurales inducidos por el campo magnético estático (SMF) en un rango moderado de inducción (β: 35-45 mT), con el fin de obtener evidencias para explicar la estrategia de respuesta a nivel celular y molecular de S. aquatilis (cepa local), explorando el potencial de SMF en el crecimiento y / o control de la toxicidad de esta cianobacteria ante mínimas variaciones del campo. Los cultivos control alcanzaron la máxima densidad celular el día 15, pero aquellos expuestos a 37,7 mT obtuvieron máximos el día 7, mientras que los expuestos a 44,3 mT el día 13, con diferentes valores de kmáx: 8 826,67 ± 538,40; 4 175,00 ± 459,62 y 3 943,75 ± 937,71, respectivamente (a = 0,05). De acuerdo con las evidencias ultraestructurales se observan modificaciones en la disposición de los tilacoides inducida por SMF, variando la distribución y las distancias entre los tilacoides y las membranas tilacoidales. Estos cambios deben tener implicación a nivel funcional, probablemente como respuesta celular para mantener la eficiencia fotosintética. Los resultados sugieren que el SMF (37,7 y 44,3 mT) induce cambios significativos en el crecimiento y la ultraestructura de esta cianobacteria planctónica, y cambios discretos moleculares que implican a la composición pigmentaria y el potencial tóxico.

Growth performance and biochemical composition of nineteen microalgae collected from different Moroccan reservoirs

Macro- and microalgae have recently received much attention due to their valuable chemical constituents. In order to increase existing data, the authors studied nineteen microalgae species isolated from different reservoirs in the Fez region (northern Morocco), undertaking experiments to determine for each species the specific growth rate, their total amounts of proteins, carbohydrates and lipids and the influence of the growth phase on these chemical constituents. Conditions of cultivation were as follows: light intensity equal to 300 μmol photons m-2 s-1, with a temperature regime of 25/20°C (day/night) and a 16/8 (light/dark) photoperiod cycle. The growth rates of the nineteen studied species of microalgae showed a wide variation between species, ranging from 0.27 g l-1 d-1 for Chlamydomonas ovalis to 3.64 g l-1 d-1 for Chlorococcum wemmeri. Protein, carbohydrate and lipid contents varied greatly between taxa and within genera. Ankistrodesmus falcatus, Chlamydomonas ovalis, Chlorococcum sp., Hyaloraphidium contortum, Scenedesmus protuberans, and Synechocystis aquatilis tended to synthesize proteins, the concentrations exceeding 20% dry weight (DW). Ankistrodesmus falcatus, Ankistrodesmus sp., Chlorococcum wemmeri, Coenocystis sp., Isocystis sp., Lyngbya bergei, Oscillatoria amphibia, Polytoma papillatum, Scenedesmus protuberans, Scenedesmus sp. and Synechocystis aquatilis showed a high capacity for lipid storage, greater than 20% DW. For carbohydrate contents, only Scenedesmus protuberans and Scenedesmus quadricauda showed an excessive level compared to other scanned species with 29.21% and 24.76% DW, respectively.

Allelopathic activity of the norharmane-producing cyanobacterium Synechocystis aquatilis against cyanobacteria and microalgae

The cyanobacterium Synechocystis aquatilis was observed growing as a monospecies in enriched phytoplankton samples in the laboratory, indicating its allelopathic activity on coexisting phytoplankton species. Therefore, the present study screened the culture medium of an axenic strain of this cyanobacterium for the presence of allelechemicals with algicidal properties by thin-layer chromatography (TLC). The allelopathic effect of S. aquatilis was evaluated by co-cultivation of target species of toxic cyanobacteria and green algae with this cyanobacterium, as well as by evaluation of norharmane (β-carboline 9H-pyrido(3,4-b) indole) crude extract prepared from the culture medium of Synechocystis. The growth of target algal species was measured as a cell density after 6 days incubation. The results showed that S. aquatilis produced the indole alkaloid norharmane with large quantities in the culture medium (86 μg l−1). In co-cultivation experiments, S. aquatilis inhibited the growth of all tested cyanobacteria and green algae. Norharmane crude extract exhibited stronger inhibition of cyanobacteria (EC50 = 4.6–4.8 μg ml−1) than green algae (EC50= 6.3–6.4 μg ml−1) in a concentration-dependent manner, indicating its apparent role in the allelopathic activity of S. aquatilis. The possible applicability of the allelochemical, norharmane, as an algicide to prevent the formation of harmful algal bloom was discussed.

Differences in the ultrastructure of two selected taxa of phytoplankton in a thermally stratified Lake Holzmaar (Germany)

This paper presents the results of ultrastructural studies and ecological aspects of some phytoplankton species belonging to the groups of cyanobacteria (Planktothrix rubescens, Synechocystis aquatilis) and green algae (Desmodesmus grahneisii). Specimens were collected during summertime from the mesotrophic and stratified Lake Holzmaar (Western Germany) as planktonic forms from the pelagic zone. The highest cyanobacterium concentration was detected in the metalimnion, where the alkaline pH, low phosphorus and high nitrogen contents were recorded. P. rubescens was characterized by straight filaments up to 1000 μm long and 5.4-8 μm wide and numerous aerotopes in cells. The accompanying algae were identified by ultrastructural analysis and photographic documentation was provided. In the case of D. grahneisii, chloroplast was situated in the parietal part of cell, with one large, oval pyrenoid and, in addition, the granular and spiny cell wall was an important taxonomical criterium for the Desmodesmus genus. This is in contrast with the cyanobacterium S. aquatilis, in which a homogeneous content with visible chromatoplasma was mostly distributed throughout the cell. This algal association was stable in the epilimnion characterized by the presence of high temperature, pH values (>8), nitrate nitrogen and oxygen concentrations