Transport And Regμlation Mechanism Of Molybdenum In Pseudomonas Aeruginosa T6SS

Pseudomonas aeruginosa is a typical Gram-negative bacterium that causes chronic infection in patients with cystic fibrosis(CF).Bacterial anaerobic growth occurs during CF chronic lung infection,and intracellμlar molybdenum can promote bacterial anaerobic respiration and survival under anaerobic conditions to affect bacterial infection and pathogenicity of the host.The Type VI Secretion System(T6SS)is discovered a new secretory system in recent years.Due to the presence of three sets of T6 SS in Pseudomonas aeruginosa,its structure,regμlation mechanism and function are also complex and diverse.Pre-laboratory secretome analysis revealed that Mod A is a potential effector protein of T6 SS and a substrate binding protein of molybdate transport system,which can promote the acquisition of molybdenum by bacteria.However,the Mod A molybdenum transport mechanism and regμlation network involved in T6 SS is not very clear,as a breakthrough point.In this study,the mod A-Flag expression plasmid was transferred into three core component mutants of the type VI secretion system to detect the secretion of Mod A,and the resμlts indicated that Mod A was secreted by H2-T6 SS.At the same time,it was considered that the secretion of Mod A was affected by molybdenum and its secretion at different molybdenum concentrations was detected.The resμlts showed that under the condition of high molybdenum,the expression of H2-T6 SS and the secretion of Mod A were inhibited and activated under anaerobic conditions.It was further shown that Mod A relies on H2-T6 SS to transport molybdenum;at the same time,Western,q RT-PCR,EMSA and other experiments showed that Anr specifically activates H2-T6 SS expression and promotes Mod A secretion under anaerobic conditions.In addition,we identified a receptor membrane protein Icm P that interacts with Mod A by in vitro protein interactions.Western resμlts showed that the expression of △icm P was also inhibited by high molybdenum,indicating that Icm P is involved in the transport of molybdenum.Further studies have also found that the T6SS-Mod A-Icm P system provides growth advantages for P.aeruginosa in bacterial competition under anaerobic conditions and is critical for bacterial virμlence.Based on the above resμlts,we finally found that Anr activates H2-T6 SS under anaerobic conditions,promoting the secretion of Mod A,and under Icm P-mediated Mod A relies on H2-T6 SS to promote the transport of molybdenum,thereby promote anaerobic metabolism and growth of bacteria.A novel molybdenum transport system that relies on T6 SS for transmembrane transport of molybdenum transport is revealed.