Humic acid and tryptophan prolong virus survival and infectivity: Molecular interactions and mechanisms.

Virus-induced infectious diseases represent one of the most significant threats to global public health. Dissolved organic matter (DOM) constitutes a critical component of aquatic environments and often influences the environmental behavior of microorganisms due to its unique structure and properties. However, research in this area remains limited, particularly concerning the effects of DOM on viral persistence in water. This study systematically investigated the influence of humic acid (HA) and tryptophan (Try) on the aggregation and survival characteristics of viruses, and utilized molecular docking technology to reveal the potential mechanism at the molecular level by which HA and Try prolong the survival time of bacteriophage MS2 (increased T99 value). The molecular docking results showed that HA and Try molecules could stably bind to specific sites of bacteriophage MS2 capsid protein through various intermolecular forces such as hydrogen bonds and van der Waals forces. The binding energy (HA: -6.93 to -10.73 kcal/mol; Try: -4.33 to -5.14 kcal/mol) indicated that this was a spontaneous and thermodynamically favorable interaction. This tight binding directly interfered with and disrupted the hydrogen bond network that maintains the natural conformation of bacteriophage MS2 capsid protein, resulting in a reduction of α-helices and β-sheets within the capsid protein, promoting the unfolding of the secondary structure of the capsid protein. Consequently, it enhanced the aggregation of virus particles and prolonged the survival time of the virus. In summary, our research provides valuable theoretical insights and practical implications for mitigating health risks associated with waterborne pathogens.