Changes in oligopeptide production by toxic cyanobacterial strains under iron deficiency

Abstract

Cyanobacteria produce several peptides whose functions and regulation mechanisms are not well understood. Iron availability has previously been suggested as a potential factor controlling production of microcystin, the best studied of these peptides, although results were not always consistent. Here, we examined how production of several peptides by 3 cyanobacterial strains changed in response to iron starvation or limitation. Experiments were run with 2 strains of Radiocystis fernandoii (28 and 86) and one of Planktothrix agardhii (27). The peptide spectra were analyzed and the gene expression of 2 peptides was assessed. Under iron starvation (no iron) all microcystin variants and one cyanopeptolin were significantly reduced in R. fernandoii 28 and P. agardhii 27. Only one compound, anabaenopeptin in P. agardhii 27, increased significantly. The strain R. fernandoii 86 did not show any significant modification in response to iron deprivation. Under moderate limitation, most peptides also decreased, although less abruptly. Conversely, changes in gene expression showed that genes coding for microcystin and aeruginosin were differentially expressed and were significantly higher under iron deprivation. This is consistent with previous findings that suggested that microcystin is produced to overcome stress. The lack of microcystin production despite the increased gene transcription is discussed in light of previous findings. This result might be due to either modifications of the cell metabolic state as a result of shortage of some important enzymes under iron deprivation or to microcystin loss as a result of its binding to proteins or other potential sink sources in the cell.

Cyanobacteria and Their Metabolites in Mono- and Polidominant Shallow Eutrophic Temperate Lakes

“…P . agardhii is a well-documented producer of various cyanometabolites (MC-RR, MC-YR, dmMC-RR, dmMC-LR, MC-LR, Asp3 MC-LR, APs B and F) [ 53 , 54 , 55 ].…”

Liver dysfunction and energy storage mobilization in traíra, Hoplias malabaricus (Teleostei, Erythrinidae) induced by subchronic exposure to toxic cyanobacterial crude extract

“…In the tropical environments, the Radiocystis genus has commonly found in cyanobacterial blooms being still mistaken with Microcystis and described as potent MC producer 7–9 . The Radiocystis fernandoi R28 strain, isolated from an oligotrophic reservoir in Minas Gerais, Brazil, produces MC having two major variants: MC‐YR and MC‐RR and other minor oligopeptides 10–12 . This R. fernandoi strain is an excellent cyanobacterial model in ecotoxicological studies to evaluate the toxicity of these two important MC variants once the MC‐LR is not produced.…”

“…[7][8][9] The Radiocystis fernandoi R28 strain, isolated from an oligotrophic reservoir in Minas Gerais, Brazil, produces MC having two major variants: MC-YR and MC-RR and other minor oligopeptides. [10][11][12] This R. fernandoi strain is an excellent cyanobacterial model in ecotoxicological studies to evaluate the toxicity of these two important MC variants once the MC-LR is not produced. Most studies were done using purified MC but, in the environment, fish may be exposed to a mixture of MC and other potentially toxic molecules.…”

Biotransformations, Antioxidant System Responses, and Histopathological Indexes in the Liver of Fish Exposed to Cyanobacterial Extract

“…Although many microcystin congeners are toxic, MC‐LR has been extensively studied because of its high toxicity to animals and humans (Atencio et al 2008; Charmichael and Boye 2016; Chen et al 2016). Radiocystis fernandoi toxin production has been categorized in few studies (Vieira et al 2003; Lombardo et al 2006; Pereira et al 2012, 2015; Pereira and Giani 2014), and some R. fernandoi strains have been reported to produce MC‐LR (Vieira et al 2003; Lombardo et al 2006). The R. fernandoi strain R28, isolated from cyanobacterial blooms in the Furnas power plant reservoir (20°40′S; 46°19′W), Minas Gerais, Brazil, primarily produces the MC‐RR and MC‐YR congeners but does not produce the MC‐LR, even when cultivated at different light intensities, nutrient deficiencies, and cell densities (Pereira et al 2012, 2015; Pereira and Giani 2014).…”

“…Radiocystis fernandoi toxin production has been categorized in few studies (Vieira et al 2003; Lombardo et al 2006; Pereira et al 2012, 2015; Pereira and Giani 2014), and some R. fernandoi strains have been reported to produce MC‐LR (Vieira et al 2003; Lombardo et al 2006). The R. fernandoi strain R28, isolated from cyanobacterial blooms in the Furnas power plant reservoir (20°40′S; 46°19′W), Minas Gerais, Brazil, primarily produces the MC‐RR and MC‐YR congeners but does not produce the MC‐LR, even when cultivated at different light intensities, nutrient deficiencies, and cell densities (Pereira et al 2012, 2015; Pereira and Giani 2014). Because of this, the R. fernandoi strain is an excellent model to study the toxic action of these 2 congeners, MC‐RR and MC‐YR.…”