Antibacterial properties and mechanism of action for serum obtained from the Chinese alligator (Alligator sinensis)

Chinese alligator (Alligator sinensis) is one of the rarest endangered reptiles found in China and possesses strong immune potential. This study tested the antibacterial ability of Chinese alligator serum (CAS) against Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa and analyzed the underlying mechanisms. Results showed that the CAS had a marked antibacterial effect on K. pneumoniae, E. coli, and P. aeruginosa. However, S. aureus was only mildly affected, and this effect disappeared when incubated with Protease K. The serum proteome revealed that the antibacterial ability of CAS was produced by interactions between various proteins and that the complement proteins played a major antibacterial role. Furthermore, the prediction of the structure and function of complement component 3 revealed eight potential protein binding sites and one nucleic acid binding site that were likely related to the broad-spectrum antibacterial ability of this serum. This study provided evidence that CAS elicits significant antibacterial effects against some pathogens and provides the basis for further development of novel antibacterial drugs.

扬子鳄（Alligator sinensis）是中国境内现存最为珍稀的濒危爬行动物之一，且具备极强的免疫潜力。本研究检测了扬子鳄血清（Chinese alligator serum, CAS）对肺炎克雷伯菌（Klebsiella pneumoniae）、大肠埃希菌（Escherichia coli）、金黄色葡萄球菌（Staphylococcus aureus）及铜绿假单胞菌（Pseudomonas aeruginosa）的抗菌活性，并剖析了其潜在作用机制。实验结果显示，CAS对肺炎克雷伯菌、大肠埃希菌及铜绿假单胞菌均具有显著抗菌活性；但对金黄色葡萄球菌仅表现出微弱抑制效果，且该活性经蛋白酶K（Protease K）孵育后完全消失。血清蛋白质组学分析表明，CAS的抗菌活性源于多种蛋白质之间的协同作用，其中补体蛋白（complement proteins）发挥了核心抗菌功能。此外，对补体成分3（complement component 3）的结构与功能预测显示，其存在8个潜在蛋白质结合位点与1个核酸结合位点，这些位点或与该血清的广谱抗菌活性密切相关。本研究证实了CAS对部分病原菌具有显著抗菌活性，为新型抗菌药物的后续研发提供了理论依据。