An examination of the antibiotic effects of cylindrospermopsin on common gram‐positive and gram‐negative bacteria and the protozoan Naegleria lovaniensis

Abstract

The importance of the toxin cylindrospermopsin to the function and fitness of the cyanobacteria that produce it remains a matter of conjecture. Given that the structure of cylindrospermopsin has commonalities with other antibacterial protein synthesis inhibitors, such as streptomycin, authors tested the possibility that the toxin might act as an antibacterial compound that can kill competing microbes. Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa were tested by the minimal inhibitory concentration method and significant antibacterial activity was only observed at a cylindrospermopsin concentration of 300 lg mL 21 after exposure for 5 days. No effect on log phase growth of E. coli was observed for this same toxin concentration. Protein synthesis was inhibited by cylindrospermopsin in E. coli 70S extracts, reduced by 25% compared with controls when treated with 41.5 lg mL 21 of the toxin; however, a much greater reduction of 97% was observed for chloramphenicol in the same experiment. Naegleria lovaniensis, a phagotrophic protozoan, was more susceptible to cylindrospermopsin, with a decrease in the number of N. lovaniensis plaques after 24-h treatment with 5-50 lg mL 21 of toxin and an LC 50 of 60 lg mL 21. Given these results, cylindrospermopsin is clearly not antibacterial at concentrations found in environmental waters, nor will it adversely affect N. lovaniensis at these concentrations. For organisms that are able to ingest cylindrospermopsin-producing cells, the response of N. lovaniensis to the toxin suggests that only a few ingested cells would be enough to kill predatory organisms with similar susceptibility. # 2008 Wiley Periodicals, Inc. Environ Toxicol 23: 36-43, 2008.

Interpreting the Possible Ecological Role(s) of Cyanotoxins: Compounds for Competitive Advantage and/or Physiological Aide?

“…In many systems, the biomass of protozoans often exceeds that of metazoans, in fact, protozoans are often the most important grazers on phytoplankton [46]. Unsurprisingly, a number of studies have demonstrated adverse effects of cyanotoxins on protozoans: For example, CYN is toxic to the amoeba Naegleria lovaniensis [47], and the protozoans Spirostomum ambiguum and Tetrahymena termophyla are both sensitive to MC [48]. Conversely, a number of protozoan grazers are known to actively feed and grow on toxic cyanobacteria [46,49].…”

Influence of Two Depuration Periods on the Activity and Transcription of Antioxidant Enzymes in Tilapia Exposed to Repeated Doses of Cylindrospermopsin under Laboratory Conditions

“…Different studies have revealed the environmental toxicity of CYN towards different groups of organisms, including amphibians [11], gastropods [12], fish [13,14], plants [15], and aquatic macrophytes [16], as well as antibacterial activity [17]. CYN exposure has hepatotoxic, nephrotoxic and general cytotoxic effects and can also lead to fetal toxicity, tumor initiation, micronucleus induction and chromosome loss [4,5].…”

Aphanizomenon gracile (Nostocales), a cylindrospermopsin-producing cyanobacterium in Polish lakes

“…Moreover, mutagenic and carcinogenic effects of CYN have also been demonstrated (Humpage et al 2000; Falconer and Humpage 2001; Bazin et al 2010). Recent studies have revealed the environmental toxicity of CYN towards different groups of organisms, including amphibians (Kinnear et al 2007), gastropods (White et al 2006), fish (Gutiérrez-Praena et al 2012), plants (Metcalf et al 2004), and aquatic macrophytes (Kinnear et al 2008), as well as antibacterial activity (Rasmussen et al 2008). Two other structural variants of CYN have been isolated: deoxy-cylindrospermopsin (Norris et al 1999) and 7-epicylindrospermopsin (Banker et al 2000).…”