Enzymes at the Ocean–Atmosphere Boundary: Lipase Modulation of Lipid Packing and Water Loss in Sea Spray Aerosols

Abstract

The Burkholderia cepacia complex (BCC) comprises marine bacteria that secrete Burkholderia cepacia lipase (BCL), an enzyme that hydrolyzes ester-linked substrates. BCL is enriched at the ocean–air interface and can be transferred to the atmosphere via sea spray aerosols (SSAs), which contain salts, organic matter, and microorganisms. SSAs influence the Earth’s radiative balance through cloud formation and can contribute to respiratory exposure. Because BCL has been linked to severe infections in immunocompromised individuals, its presence in SSAs may have implications for both climate-relevant processes and human health. Here, we quantify water evaporation from saline solutions with and without BCL beneath marine-relevant lipid monolayers. Lipid monolayers suppress evaporation relative to pure salt solutions, whereas the addition of BCL restores water loss to near–salt-solution levels, indicating disruption of the interfacial barrier. To probe the molecular basis of this effect, we performed classical all-atom molecular dynamics simulations of BCL in marine-relevant lipid monolayer and bilayer systems, followed by simulations of full-scale, heterogeneous nascent SSA models. Simplified model slab systems reveal BCL conformational dynamics and interfacial stability, while realistic aerosol models reproduce experimental trends and highlight the roles of curvature and lipid packing in modulating water loss. These results demonstrate that structural complexity critically shapes protein behavior at air–water interfaces and emphasize the need for realistic aerosol models in studies of marine interfacial processes.