On November 15, the Seventh Affiliated Hospital, Sun Yat-sen University invited Professor John Mekalanos for academic exchanges who presented a lecture "Bacterial cGAS-like Enzymes Synthesize Diverse Nucleotide Second Messengers". Professor John Mekalanos is a member of National Academy of Sciences and Chair of Department of Microbiology and Immunobiology. Vice President Yihang Pan of the Seventh Affiliated Hospital, SYSU presided over the forum. In this forum, more than 50 people punctuated, including Deyin Guo, Dean of School of Medicine, SYSU, Deputy Dean Yuan Chen, Deputy Secretary of the Party Committee Xiaoqiu Ding, Assistant Dean Xingding Zhang，Professor Wenjing Zhao，Associate Professor Xiangyu Mou，Director Shiyang Li and colleagues from our hospital and other health and medical institutions in Guangming district.

Academician John Mekalanos is the Lehman Professor at Harvard Medical School, and he since 1996 has served as Chair of the Department of Microbiology and Immunobiology (formerly Microbiology and Molecular Genetics). His research crosses multiple facets of bacterial pathogenesis with an emphasis on using genetic and functional genomic approaches to explore virulence gene regulation and host-pathogen interactions. Dr. Mekalanos has received various great honors, including election to the National Academy of Sciences and American Academy of Microbiology, the Eli Lilly Award and AAAS Newcomb Cleveland Prize. Notably, Dr. Mekalanos was chosen as the first recipient of the Drexel Medicine Prize in Infectious Disease and received the Sanofi-Institut Pasteur Award for Biomedical Research in 2012. His laboratory has invented various genetic tools that have been successfully applied in such domain for decades, pioneering new approaches to understanding bacterial virulence from the gene to the genomic levels. Recently, the Mekalanos laboratory reported the discovery of the Type VI secretion system and dramatically progressed the understanding of this novel organelle dynamically functions. His group has contributed to the development of prototype vaccines effective against cholera, typhoid, anthrax and other encapsulated microorganisms, as well as to seeking evidence supporting that bacteriophages control cholera epidemics in natural endemic settings.

At the forum, Academician John Mekalanos introduced the new bacterial cGAS-like protein and its new second messenger. Human cGAS(cyclic GMP-AMP synthase) is a type of Nucleotidyltransferase that binds to DNA and activates both STING and interferon type I, enabling them to target for many autoimmune diseases and cancers as medical drugs. Recently, the Mekalanos group developed a method for the expression of human cGAS protein in Vibrio cholerae, successfully analyzing part of the structure and function of cGAS. It was found within that the cyclic-di-GMP-AMP plays a critical role in the metabolism and pathogenesis of bacteria. Meanwhile, further research has shown a new cyclic nucleotide in the system can activate a variety of bacterial receptor proteins. The cyclic nucleotides, acting as second messengers in regulating the composition of the human intestinal flora, may provide a new research perspective and treatment for human diseases associated with intestinal flora. This concept caused listeners’ interest so much and led to in-depth discussion further.