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The interaction between nanoparticles (NPs) and bacterial cell envelopes is crucial for designing effective antibacterial materials against multi-drug-resistant pathogens. However, the current understanding assumes a uniform bacterial cell wall. This study challenges that assumption by investigating how bacterial cell wall curvature impacts antibacterial NP action. Focusing on Janus NPs, which feature segregated hydrophobic and polycationic ligands and previously demonstrated high efficacy against diverse bacteria, we found that these NPs preferentially target and disrupt bacterial poles. Experimental and computational approaches reveal that curvature at E. coli poles induces conformational changes in lipopolysaccharide (LPS) polymers on the outer membrane, exposing underlying lipids for NP-mediated disruption. We establish that curvature-induced targeting by Janus NPs depends on the outer membrane composition and is most pronounced at physiologically relevant LPS densities. This work demonstrates that high-curvature regions of bacterial cell walls are “weak spots” for Janus NPs, thereby aiding the development of more effective targeted therapies. 

Background Nanoparticles (NPs) hold promise as alternatives to antibiotics in the fight against multi-drug-resistant bacteria. However, concerns about their cytotoxicity, particularly their effects on mammalian cells, must be thoroughly addressed to ensure therapeutic safety. Amphiphilic Janus NPs, which have segregated hydrophobic and polycationic ligands on two hemispheres, have previously been shown to exhibit potent antibacterial activity. Methods In this study, we evaluated the cytotoxicity of amphiphilic Janus NPs in immune and cancer cell lines. Cytotoxicity assays were performed to assess the effects of Janus NPs on cell viability and membrane integrity, with a particular focus on how internalization of the nanoparticles influenced cellular responses. Results The results revealed that both immune and cancer cells exhibited negligible cytotoxic effects when exposed to Janus NPs. However, phagocytic immune cells demonstrated greater susceptibility to membrane damage and viability loss, suggesting that internalization plays a significant role in nanoparticle-induced cytotoxicity. Conclusions Amphiphilic Janus NPs show great potential as highly effective antibacterial agents with minimal cytotoxicity. While immune cells may be more vulnerable to nanoparticle-induced damage due to their internalization capacity, these findings support the further investigation of Janus NPs for clinical applications. 

Protein lipidation plays critical roles in regulating protein function and localization. However, the chemical diversity and specificity of fatty acyl group utilization have not been investigated using untargeted approaches, and it is unclear to what extent structures and biosynthetic origins ofS-acyl moieties differ fromN- andO-fatty acylation. Here, we show that fatty acylation patterns inCaenorhabditis elegansdiffer markedly between different amino acid residues. Hydroxylamine capture revealed predominant cysteineS-acylation with 15-methylhexadecanoic acid (isoC17:0), a monomethyl branched-chain fatty acid (mmBCFA) derived from endogenous leucine catabolism. In contrast, enzymatic protein hydrolysis showed that N-terminal glycine was acylated almost exclusively with straight-chain myristic acid, whereas lysine was acylated preferentially with two different mmBCFAs and serine was acylated promiscuously with a broad range of fatty acids, including eicosapentaenoic acid. Global profiling of fatty acylated proteins using a set of click chemistry–capable alkyne probes for branched- and straight-chain fatty acids uncovered 1,013S-acylated proteins and 510 hydroxylamine-resistantN- orO-acylated proteins. Subsets ofS-acylated proteins were labeled almost exclusively by either a branched-chain or a straight-chain probe, demonstrating acylation specificity at the protein level. Acylation specificity was confirmed for selected examples, including theS-acyltransferase DHHC-10. Last, homology searches for the identified acylated proteins revealed a high degree of conservation of acylation site patterns across metazoa. Our results show that protein fatty acylation patterns integrate distinct branches of lipid metabolism in a residue- and protein-specific manner, providing a basis for mechanistic studies at both the amino acid and protein levels. 

Phagocytosis is a critical immune function for infection control and tissue homeostasis. During phagocytosis, pathogens are internalized and degraded in phagolysosomes. For pathogens that evade immune degradation, the prevailing view is that virulence factors are required to disrupt the biogenesis of phagolysosomes. In contrast, we present here that physical forces from motile pathogens during cell entry divert them away from the canonical degradative pathway. This altered fate begins with the force-induced remodeling of the phagocytic synapse formation. We used the parasiteToxoplasma gondiias a model because liveToxoplasmaactively invades host cells using gliding motility. To differentiate the effects of physical forces from virulence factors in phagocytosis, we employed magnetic forces to induce propulsive entry of inactivatedToxoplasmainto macrophages. Experiments and computer simulations show that large propulsive forces hinder productive activation of receptors by preventing their spatial segregation from phosphatases at the phagocytic synapse. Consequently, the inactivated parasites are engulfed into vacuoles that fail to mature into degradative units, similar to the live motile parasite’s intracellular pathway. Using yeast cells and opsonized beads, we confirmed that this mechanism is general, not specific to the parasite used. These results reveal new aspects of immune evasion by demonstrating how physical forces during active cell entry, independent of virulence factors, enable pathogens to circumvent phagolysosomal degradation.