Marine cyanobacteria are the most abundant photosynthetic organisms on earth and contribute significantly to global primary production. Phages influence many microbial processes including the population dynamics, diversity and evolution of their hosts. However, our ability to accurately determine the extent of microbial infection and phage impact on the above processes is severely limited by the lack of appropriate methods. Here I present work towards developing the solid-phase PCR polony method for quantification of the extent of cyanobacterial infection by podoviruses at the single-cell level. Using a model host-phage system in the lab, I found that in-gel heat lysis was sufficient for cell permeabilization and that the polony method can detect viral DNA inside infected cells. Viral DNA was detected at all stages of the infection cycle. Furthermore, an increasing number of infected cells were detected when higher phage-to-host ratios were used for infection. The results were similar to those obtained when a lab-based lysis method was used for assessing the extent of infection. These data indicate that the polony method will be an effective approach for estimating the proportion of infected cells in cyanobacterial populations in the oceans.
