Raphidiopsis raciborskii is a nitrogen-fixing freshwater cyanobacterium that recently gained attention due to its high invasiveness potential, toxicity, and harmful blooms, which can negatively impact biodiversity, ecosystem functions, and water quality. Despite its ecological significance, factors controlling this species’ occurrence and bloom dynamics remain poorly understood. Cyanophages, viruses that infect cyanobacteria, may play a crucial role in microbial population and community dynamics through host lysis, horizontal gene transfer, and metabolic reprogramming [1,2]. Understanding these interactions in freshwater ecosystems is essential for advancing our knowledge of cyanophage ecology and may provide insights into the mechanisms by which viruses regulate cyanobacterial activity, growth, and transcription. Investigations into transcriptional regulation of host cyanobacteria by viral infection are also crucial for the assessment and development of phage-based technologies for the mitigation of harmful algal blooms.
To investigate the transcriptional response of R. raciborskii to cyanophage infection as well as to establish a transcriptional scheme for cyanophage, we used R. raciborskii strain KLL07 and its lytic cyanophage Cr-LKS4 as a model virus-host system. In this study, control and infection treatments were established by adding either filter-sterilized growth medium or cyanophage suspensions at the multiplicity of infection of three (MOI = 3) in four biological replicates to unialgal yet non-axenic cultures. The experiment lasted 120 hours, with samples collected every 4-8 hours for cell and phage abundance measurements, DNA and RNA sequencing, and proteomic analysis.
We will present results on cyanobacterial and cyanophage dynamics during the infection experiment along with differential gene expression analysis during different infection stages (adsorption, DNA replication and lysis) of R. raciborskii. Additionally, changes in R. raciborskii microbiome composition induced by the cyanophage-mediated lysis of the photosynthetic host will be presented. These findings will contribute to a better understanding of the ecological significance of freshwater cyanophages and their impact on cyanobacteria growth and succession.