Cultivated single-stranded DNA phages that infect marine Bacteroidetes prove difficult to detect with DNA-binding stains.

This is the first description of cultivated icosahedral single-stranded DNA (ssDNA) phages isolated on heterotrophic marine bacterioplankton and with Bacteroidetes hosts. None of the 8 phages stained well with DNA-binding stains, suggesting that in situ abundances of ssDNA phages are drastically underestimated using conventional methods for enumeration.