ABSTRACT
Our studies tried to demonstrate Eha (Et haemolysin activator) could regulate the resistance of the bacterium against acidification to survive in the macrophage and explain its underlying molecular mechanism.When the bacteria infected the macrophages at time intervals,intracellular survival rate in bafilomycin-treated macrophages was higher than that with untreated cells,and the rate of wild type ET 13 was higher than that of its eha mutant,respectively (P＜0.05).The survival rate of the wild type was higher than that of the mutant under acid treatment (P＜0.05).To determine the conditions that induced the highest eha expression,we constructed a pMP220-Peha LacZ plasmid and determined the lacZ expression under different conditions.After exposure of pH6.3 medium for 2 h time,we performed the whole transcriptomic profiles of the wild type and mutant by RNA-sequencing.We identified 147 differentially-expressed genes ([log2 ratio| ≥1),113 and 34 of which were significantly up-and down-regulated,respectively in the mutant,comparing with the wild type.These findings were validated by qRT-PCR.GO functional analysis revealed that these genes were divided into 25 categories,including the bacterial catalysis,cellular composition,combination,localization,metabolism,processing,and transportation.Based on the KEGG database,these genes were distributed in 55 pathways,such as two-component system,ABC transporters,and microbial metabolism in diverse environments.Overall,Eha is an important regulator to affect all kinds of target genes and pathways for E.tarda to adapt to an acid environment.These results could be helpful for further investigations of the mechanisms by which E.tarda survives in macrophages.