Fig. 1: Experimental design and impacts of a protist on cyanobacteria and cyanobacteria virocells (cyanovirocells).

A Experimental design. Synechococcus WH8102 cells were infected with the T4-like myophage S-SSM5 to generate cyanovirocells. Cyanovirocells were studied over the course of infection either alone (“Cyanovirocells only” treatment) or in the presence of the protist Oxyrrhis marina (“Cyanovirocells with protist”). Arrows denote the comparisons: all treatments are compared against the Control to detect significant changes to the transcripts, metabolites, and photosynthetic efficiency. In addition, the focus of this study is the cyanovirocell responses to the presence of a protist, which is the contrast between cyanovirocells only and cyanovirocells with protist. B Fluorescent microscopic image of O. marina with ingested Synechococcus cells (protists were stained red with WGA - Alexa 488 and Synechococcus were detected with phycoerythrin pigment autofluorescence). Image was acquired using Zeiss LSM 710 confocal microscope with a 63× (1.4 N.A.) objective. C General infection dynamics of Synechococcus infected with S-SSM5, followed over 55 h post phage addition. This time course captures multiple cycles of infection. D Cell and phage abundances over the course of this study. Samples for genome-wide transcriptomics, endo-metabolomics, exo-metabolomics, and microscopy and photosynthetic efficiency measurements were taken every 2 h between 2 and 12 h post phage and/or protist addition. This time course captures a population-level view of infection, whereby more than one infection cycle is taking place (shaded in gray): the phages released from “infection cycle 1” infect new cells and undergo “infection cycle 2+” (i.e., two or more asynchronized infection cycles may be happening at this time). Both the burst size (here depicted as 4 phages released per infected cell), and the number of infection cycles are simplified. Cell abundance decreases significantly from start to end of ‘omics sampling during phage infection (t-test, p value <0.05), with or without protist (indicated by an asterisk for each treatment), and it does not significantly change in the presence of the protist alone. All experiments included a minimum of three biological replicates and the average with standard error is shown.