Transport of marine tracer phage particles in soil

Marine phages have been applied to trace ground- and surface water flows. Yet, information on their transport in soil and related particle intactness is limited. Here we compared the breakthrough of two lytic marine tracer phages (Pseudoalteromonas phages PSA-HM1 and PSA-HS2) with the commonly used Escherichia virus T4 in soil- and sand-filled laboratory percolation columns. Phages showed high mass recoveries in the effluents and a higher transport velocity than non-reactive tracer Br^-. Comparison of effluent gene copy numbers (CN) to physically-determined phage particle counts (VP) or infectious phage counts (PFU) showed that PSA-HM1 and PSA-HS2 retained high phage particle intactness (I_p > 81%), in contrast to T4 (I_p < 36 %). Our data suggest that marine phages – in addition to groundwater applications - may also be applied in soil to mimic the transport of (bio-) colloids or anthropogenic nanoparticles of similar traits. CN-based enumeration thereby allows for highly sensitive quantification and thus for the detection of even highly diluted marine tracer phages in environmental samples.