Isolation of Antagonistic Bacterial Strains and Their Antimicrobial Volatile Organic Compounds Against <i>Pseudogymnoascus destructans</i> in <i>Rhinolophus ferrumequinum</i> Wing Membranes

White-nose syndrome (WNS), caused by the fungus <i>Pseudogymnoascus destructans</i> (<i>Pd</i>), has led to significant mortality and species endangerment in North America. Bats in eastern China, however, carry low loads of <i>Pd</i> and do not exhibit disease, suggesting natural resistance. To explore potential defenses, we isolated and screened antagonistic bacteria from the wing membranes of <i>Rhinolophus ferrumequinum</i> for their ability to inhibit <i>Pd</i> growth. We employed the plate delineation isolation method to obtain 74 single strains, which were then screened for antagonistic effects through contact and non-contact inhibition experiments. A total of 18 antagonistic strains were isolated. After sequencing and comparison with the NCBI database, we identified eight known species and three unidentified species of antagonistic bacteria: <i>Pseudomonas carnis</i>, <i>Buttiauxella ferragutiae</i>, <i>Paraburkholderia fungorum</i>, <i>Arthrobacter rhombi</i>, <i>Serratia liquefaciens</i>, <i>Paeniglutamicibacter gangotriensis</i>, <i>Brevibacterium aurantiacum</i>, <i>Acinetobacter lactucae</i>, <i>Pseudomonas</i> sp., <i>Brevibacterium</i> sp., and <i>Acinetobacter</i> sp. Seventeen isolated strains showed varying degrees of inhibition by contact, while five species, including <i>P. carnis</i>, <i>B. ferragutiae</i>, <i>S. liquefaciens</i>, <i>P. gangotriensis</i>, and <i>Brevibacterium</i> sp., also inhibited <i>Pd</i> via non-contact mode. We utilized solid-phase microextraction coupled with GC-MS to obtain approximately 20 volatile compounds, all of which exhibited inhibitory effects on the growth of <i>Pd</i>, including ketones, aldehydes, and sulfur ethers. Notably, 5 ppm of 1-undecene, dimethyl trisulphide, and 2-nonanone each independently inhibited <i>Pd</i> growth. These findings suggest that the antagonistic strains and their VOCs might help protect bats from WNS. Understanding the interactions between <i>Pd</i> and skin flora, along with their VOCs, may be crucial in mitigating bats' vulnerability to WNS and developing effective mitigation strategies in the future.