a Axenic M. vaginatus PCC9802 on nitrogen-deplete (N−) and nitrogen-replete (N+) solid medium. A Wilcox test shows significant differences (P < 0.001). b Co-cultured with various heterotrophic bacteria under N− conditions. Legend shows strain denomination and (†) denotes isolates matching known cyanosphere members. A Kruskal–Wallis test with chi-squared p value adjustments shows significant differences between axenic M. vaginatus on N− medium and co-cultures with isolates, Arthrobacter sp. O80 and Massilia sp. METH4 (P < 0.01 and <0.009, respectively), but not others. Co-cultures with S. marcescens D1, Geodermatophilus sp. B17, and Paenibacillus sp. S14 resulted in death of M. vaginatus and could not be quantified.