Further, two morphologically and optically highly similar strains of the filamentous click here bloom-forming Nodularia spumigena were included: strain HEM from University of Helsinki, Microbiology division (Sivonen et

al. 1989), and one with an undocumented culturing history that we conservatively annotate Nodularia sp. from the TV collection. All species are common in the Baltic Sea. Nutrient replete cultures were grown on sterile modified BG-11 media with salinity adjusted to the Baltic Sea at 8.3 g NaCl L−1, pH = 7.4, and added vitamin B12 (0.02 μg L−1). Silicate was added to the diatom cultures at 0.044 g Na2SiO3·5H2O L−1. BG11 medium is rich in Histone Methyltransferase inhibitor nitrate (N:P approximately 100:1), so cultures that were left to grow and age in a particular batch were expected to eventually become starved of phosphorous. To induce nitrogen starvation instead, selected cultures were periodically refreshed with medium with reduced (10%) nitrate (N treatment) or no nitrate (-N treatment). These treatments were expected to induce fixation of elemental nitrogen in the Nodularia strains. Light conditions were 12/12 h light/dark from fluorescent tubes Selleckchem Nutlin 3 at low/medium/high light treatments of 20, 70 or

350 μmol photons m−2 s−1, respectively, using green filters to mimic the Baltic Sea environment in the low and medium light levels. The green filters also increased production of phycobilipigments, particularly in the Synechococcus strains. The cultures were kept in suspension by daily gentle

mixing, and bubbling with filtered air for 15 min every hour. The complete combination of treatments and sampling times (i.e. aging of the cultures) is presented in Table 1. Cultures that exhibited no growth after up to 2 weeks were removed from the experiment. Cultures that underwent significant visual changes were sampled more than once. The different treatments resulted MTMR9 in a total of 31 sampling events of cyanobacterial cultures and 15 sampling events of the algal cultures. Table 1 Culturing conditions Cultured species Culturing conditions (light, nutrients) 20, +N 70, +N 70, N 350, N 350, −N Synechococcus sp. CCY9201a 5, 8 7, 8   8 2 Synechococcus sp. CCY9202a 12, 14, 19 5, 8, 11,12   8   Nodularia spumigena HEMb 14, 17 7, 14, 17 12, 21 11, 14, 16   Nodularia sp.c   7, 13, 17 12, 21 11, 23   Brachiomonas submarina TV15c   7, 17, 11, 34   8 2, 7 Thalassiosira pseudonana TV5c   12, 13, 14, 17, 24, 34   7 2 The numbers under each growth regime indicate the time (days) that the respective culture was left to grow/age after inoculation, before sampling took place. Growth light intensities (values in column headers) have units μmol photons m−2 s−1. Nitrogen additions are indicated with +N, N, −N for nitrogen replete, nitrogen limited and nitrogen deplete conditions aErnst et al. (2003) bSivonen et al.