Evidence that sulfur metabolism plays a role in microcystin production by Microcystis aeruginosa

Microcystin production by Microcystis aeruginosa: Direct regulation by multiple environmental factors

“…Under sulphur limitation a reallocation towards the synthesis of low sulphur proteins and the degradation of high sulphur proteins of cells is generally observed (e.g. Giordano et al, 2005), and dependence on the sulphur amino acid, methionine, for MCYST production has been inferred from studies on N-limited chemostats of M. aeruginosa MASH-01A19 (Long, 2010). It is plausible that cellular pools of the methyl donor Sadenosylmethionine (SAM; required for MCYST synthesis; Moffitt and Neilan, 2000;Tillett et al, 2000) which is in turn dependent upon methionine, could be limiting under low SO 4 2À supply and therefore impede MCYST production (Long, 2010).…”

“…Giordano et al, 2005), and dependence on the sulphur amino acid, methionine, for MCYST production has been inferred from studies on N-limited chemostats of M. aeruginosa MASH-01A19 (Long, 2010). It is plausible that cellular pools of the methyl donor Sadenosylmethionine (SAM; required for MCYST synthesis; Moffitt and Neilan, 2000;Tillett et al, 2000) which is in turn dependent upon methionine, could be limiting under low SO 4 2À supply and therefore impede MCYST production (Long, 2010). Interestingly, the expression of both type I and type IV RuBisCOs from M. aeruginosa PCC 7806 (the former being central to CO 2 -fixation within carboxysomes and the latter being involved in the methionine salvage pathway) have been found to be sulphurdependent (Carré -Mlouka et al, 2006), and relationships between MCYSTs and RuBisCO have been proposed previously (Jä hnichen et al, 2001;Zilliges, 2007;Zilliges et al, 2011).…”

“…For summary see Sivonen and Jones (1999) and Long (2001). The effect of SO 4 2À had not been examined previously despite its potential importance (Long, 2010).…”

“…Both fractions were analysed separately by HPLC. For sample preparation and analysis see Long (2010). Total MCYST concentrations were calculated as sum of intra-and extracellular concentrations.…”

Internal nutrient loading may increase microcystin concentrations in freshwater lakes by promoting growth ofMicrocystispopulations

“…Indeed, laboratory experiments have demonstrated that physicochemical variables can directly affect microcystin production by Microcystis cells. For example, rates of toxin production have been shown to be altered by temperature (Ame´and Wunderlin, 2005), light (Deblois and Juneau, 2010), nitrogen (Dai et al, 2008), phosphorus (Bickel et al, 2000;Oh et al, 2000), inorganic carbon (Jahnichen et al, 2007), iron (Lukacˇand Aegerter, 1993;Sevilla et al, 2008) and sulfur (Long, 2010). However, cellular microcystin quotas of cyanobacteria exposed to different environmental conditions usually do not vary by more than five-fold (Sivonen and Jones, 1999).…”