Development of Styrene Maleic Acid Lipid Particles as a Tool for Studies of Phage-Host Interactions

Abstract

The infection of a bacterium by a phage starts with attachment to a receptor molecule on the host cell surface by the phage. As receptor-phage interactions are crucial to successful infections, they are major determinants of phage host-range and by extension of the broader effects that phages have on bacterial communities. Many receptor molecules, particularly membrane proteins, are difficult to isolate because their stability is supported by their native membrane environments. Styrene maleic acid lipid particles (SMALPs), a recent advance in membrane protein studies, are the result of membrane solubilizations by styrene maleic acid (SMA) co-polymer chains. SMALPs thereby allow for isolation of membrane proteins while maintaining their native environment. Here, we explore SMALPs as a tool to isolate and study phage-receptor interactions. We show that SMALPs produced from taxonomically distant bacterial membranes allow for receptor-specific decrease of viable phage counts of several model phages that span the three largest phage families. After characterizing the effects of incubation time and SMALP concentration on the activity of three distinct phages, we present evidence that the interaction between two model phages and SMALPs is specific to bacterial species and the phage receptor molecule. These interactions additionally lead to DNA ejection by nearly all particles at high phage titers. We conclude that SMALPs are a potentially highly useful tool for phage host-interaction studies. IMPORTANCE Bacteriophages (viruses that infect bacteria or phages) impact every microbial community. All phage infections start with the binding of the viral particle to a specific receptor molecule on the host cell surface. Due to its importance in phage infections, this first step is of interest to many phage-related research and applications. However, many phage receptors are difficult to isolate. Styrene maleic acid lipid particles (SMALPs) are a recently developed approach to isolate membrane proteins in their native environment. In this study we explore SMALPs as a tool to study phage-receptor interactions. We find that different phage species bind to SMALPs, while maintaining specificity to their receptor. We then characterize the time and concentration dependence of phage-SMALP interactions, and furthermore show that they lead to genome ejection by the phage. Combined, the results presented here show that SMALPs are a useful tool for future studies of phage-receptor interactions.

Mechanisms of Formation, Structure, and Dynamics of Lipoprotein Discs Stabilized by Amphiphilic Copolymers: A Comprehensive Review

“…As reviewed by Overduin and Esmaili, SMA is effective for solubilizing both monomeric and oligomeric proteins as well as those that are unstable, low-abundance, or lipid-dependent [ 13 ]. Extraction using polymers can be used to study specific interactions of membrane proteins with other membrane proteins [ 13 ], with lipids [ 122 , 135 , 136 , 137 , 138 ], and with ligands or substrates [ 115 , 116 , 126 , 128 , 139 ] and even to study phage–host interactions [ 140 ]. Following extraction with SMA, MPs can later be reconstituted back into lipid bilayers for functional studies [ 119 , 122 ].…”

A single-step extraction and immobilization of soybean lipolytic enzymes by using a purpose-designed copolymer of styrene and maleic acid as a membrane lysis agent

“…Another important factor affecting formation of such nanodisc is a lipid type of which it was contained. Solubilization of the Gram-negative E. coli membranes upon PSMA addition yielded the nanodiscs with the size diameter of around 10 nm, while that of the Gram-positive B. subtilis membranes showed larger size between 50 and 100 nm [ 36 ]. Taken together with the DLS results in Fig.…”

Biological insights from SMA-extracted proteins

“…This approach enables a quantitative, real-time measurement of binding assays with relatively low concentrations of purified protein. The use of SMA-solubilised bacteria as a tool to isolate and study phage-receptor interactions has been investigated [ 69 ]. It was found that specific interactions could be detected between different phage and their target bacteria, which led to DNA ejection by the phage.…”