Phosphate Limitation Increases Content of Protease Inhibitors in the Cyanobacterium Microcystis aeruginosa

Abstract

Increased anthropogenic nutrient input has led to eutrophication of lakes and ponds, resulting worldwide in more frequent and severe cyanobacterial blooms. In particular, enhanced availability of phosphorus (P) can promote cyanobacterial mass developments and may affect the content of secondary metabolites in cyanobacteria, such as protease inhibitors (PIs). PIs are common among cyanobacteria and have been shown to negatively affect herbivorous zooplankton. Here, we test the hypothesis that P-limitation reduces the growth of Microcystis, but increases the content of PIs. In batch culture experiments with eight different initial phosphate concentrations (5–75 µM) we determined growth, stoichiometry, and PI content of Microcystis aeruginosa NIVA Cya 43. This strain produces the protease inhibitor BN920 that is converted by chlorination to CP954, which constitutes the major PI in this strain. C:N:P-ratios of the biomass indicated variation of P-limitation with treatment and time. When normalized to biomass, the PI content varied up to nearly nineteen-fold with treatment and time and was highest in the low-P treatments, especially during the mid-exponential growth phase. However, these effects were alleviated under nitrogen co-limitation. The content of CP954 showed an inverse u-shaped response to growth rate and C:N-ratio of the cyanobacterial biomass, whereas it increased with cyanobacterial C:P. The results indicate that P-limitation supports a higher content of defensive PIs and may indirectly foster cyanobacterial blooms by increasing the negative interference of cyanobacteria with their consumers.

Anabaenopeptins: What We Know So Far

“…These data match the result of Teikari and colleagues [ 94 ], who studied the same Anabaena strain and encountered higher quantities of transcripts belonged to anabaenopeptins, anabaenopeptilide, and microcystins gene clusters under low-phosphate conditions. Phosphate limitation also increases the content of protease inhibitors of the cyanobacterium M. aeruginosa NIVA CYA 43 [ 95 ].…”

Multiclonal study of Daphnia magna with respect to adaptation to toxic cyanobacteria

“…In this context, it has to be noted that the protease inhibitor content of a cyanobacterial strain may vary. As shown for strain NIVA Cya 43 (Burberg et al 2019, 2020), Schwarzenberger et al (2013 b ) demonstrated that the protease inhibitor content of M. aeruginosa strain BM25 was strongly affected by available nutrient ratios. In accordance with the carbon‐nutrient‐balance hypothesis (van de Waal et al 2014) the content of the N‐containing protease inhibitors in BM25 decreased under N‐limitation (C : N = 13) and increased under P‐limitation (C : P = 234).…”

Coupling dairy wastewaters for nutritional balancing and water recycling: sustainable heterologous 2-phenylethanol production by engineered cyanobacteria

“…On the other hand, phosphates were sufficient for supporting cyanobacteria growth, even at the lowest concentrations measured (Table 1). High phosphate loads definitely promote the cyanobacterial biomass accumulation (Burberg et al, 2020), as indicated in the context of eutrophication. This phenomenon is often attributed to the high content of phosphates in cleaning agents and fertilizers, and even the influence of climate change can promote phosphates accumulation in waterbodies (Forber et al, 2018;Wilson et al, 2019).…”