Organic particle scavenging by marine bacteria: influences of bacterial nanoscale surface properties

Marine bacteria contribute to biogeochemical cycles by scavenging organic nanoparticles such as cell fragments, viruses, excretions from phytoplankton and bacteria, and naturally occurring polymeric substances. Nonetheless, bacterial surface properties influencing this process remain poorly understood. A previous study found that marine bacteria exhibit significant variation in surface roughness, which affects nanoparticle attachment, influencing bacterial survival and marine biogeochemical cycles. However, cell surface characteristics such as Young's modulus and adhesiveness have rarely been measured. This study investigated bacterial nanoscale surface properties and their effects on nanoparticle attachment. Atomic force microscopy was employed to measure these parameters of 559 individual bacterial cells collected from Okinawa coastal waters. These results revealed significant variation in Young's modulus (6-21,000 kPa) and adhesiveness (86-1,200 pN). Subsequent coincubation experiments with polystyrene beads and virus-like particles, as model nanoparticles, demonstrated a significant negative correlation between Young's modulus and the attachment of virus-like particles, whereas no significant relationships were observed for other factors. Our results suggest that measuring bacterial surface properties provides novel insights into their strategies for resource utilization and their contribution to marine biogeochemical cycles.IMPORTANCESurface properties of marine bacteria are believed to influence their ability to acquire nanoparticles for nutrition. However, studies on these properties are limited, and the relationship with nanoparticle attachment remains unclear. This study measured Young's modulus and adhesiveness of marine bacteria, investigating their variability and their influence upon nanoparticle attachment. This work sheds light on biophysical mechanisms driving bacterial nanoparticle utilization, as well as ecological and biogeochemical implications of bacterial surface properties in marine environments.