BACTERIAL SURFACE ROUGHNESS AFFECTS VIRAL ATTACHMENT IN SEAWATER

Viruses influence microbial community structure and biogeochemical cycles in marine environments. Viral attachment to non-host bacterial surfaces could influence host viral infection rates, however the mechanism of such viral attachment is unknown. In this study, we examined the variability of bacterial surface roughness in seawater and the relationship between bacterial roughness and attachment of (presumed) non-host viruses. We measured surface roughness of natural bacterial assemblages (NBA; obtained from 0.2–3.0 µm fractionated seawater) and three different bacterial isolates [Vibrio sp. SWAT3 (Long and Azam 2001), Alteromonas sp. TW7 (Bidle and Azam 2001) and AltSIO (Pedler et al 2014)] by atomic force microscopy (AFM). The root mean square deviation of surface roughness (Rq) of NBA was 2–15 nm. The Rq of isolates (2–10 nm) was different for different species and growth phases (except for AltSIO). Viral attachment to SWAT3 and TW7 showed positive linear relationships between roughness and viral attachment. In contrast, there was no correlation between viral attachment and other parameters measured: cell hydrophobicity, concentration of transparent exopolymer particles and % live cells. Furthermore, the cell surface adhesion measurement by AFM indicated that the rougher cells were less sticky and/or less negatively charged than the smoother cells. Our results indicated that bacterial surface roughness might play a role in controlling viral attachment in the ocean with possible ecological and biogeochemical implications. Further, our observations raise questions on the underlying mechanisms.