Algicidal bacteria against cyanobacteria: Practical knowledge from laboratory to application

The use of algicidal bacteria has gained prominence as natural solution to control the worrying increase of harmful algal blooms worldwide. However, although cyanobacterial blooms (cyanoHABs) often dominate freshwater bodies, recent reviews on the subject have addressed cyanobacteria in the second place and focused more on bacteria-algae interactions. This article provides a critical review of the fundamental aspects of searching for, isolating and assaying candidate algicidal bacteria targeting cyanobacteria. Possible species-specific interactions and the different modes of action of bacteria against different species of cyanobacteria are also discussed. It has been observed that there is a clear bias in the literature toward the genus Microcystis, being by far the most studied and reviewed to date. This contrasts with the numerous studies showing cyanobacterial blooms dominated by other harmful species, such as the genera Planktothrix, Aphanizomenon or Raphidiopsis. To add new knowledge to the lack of current studies on these genera, a separate experimental section has been included in this review with research results on the sensitivity of nine harmful freshwater cyanobacteria and two green algae to different bacteria and algicidal compounds. Finally, certain ecological and biosafety risks that must be taken into account when applying algicidal bacteria as a bioaugmentation strategy are also highlighted. Overall, this review is presented as an attempt to outline the knowledge gathered over the last thirty years of research, while raising new questions and debates on key issues that remain poorly understood.