A Single-Cell Analysis of Virioplankton Adsorption, Infection, and Intracellular Abundance in Different Bacterioplankton Physiologic Categories

Abstract

Culture studies of phage-host systems have shown that phage proliferation strongly depends on the physiological state of the host, but it is still unclear to what extent this holds true within aquatic ecosystems. We used a combination of flow sorting and electron microscopy to explore how the frequency of bacterial cells with attached viruses (FCAV), of visibly infected cells, and the number of intracellular viruses are distributed within five physiologic categories: cells with high (HNA) and low (LNA) nucleic acid content, with a compromised membrane, in division, and with an intact-looking morphology. FCAV was not different between the cellular physiologic categories, suggesting low influence of host physiology on viral adsorption. Infected cells were found within all the physiologic categories, besides the dividing cells, but showed different levels of new virion production, with the abundance of intracellular viruses ranked as follows: HNA > intact-looking cells > LNA > compromised membrane cells. These results favor the physiological control hypothesis of viral progeny production. The calculation of viral production rate of the HNA and LNA cells show that viral infection of HNA cells likely accounts for the majority of viral production. It also show that cells considered as less active can still act as resources for phages, although they contain much less intracellular phage particles.