A new cis-encoded sRNA, BsrH, regulating the expression of hemH gene in Brucella abortus 2308

A total of 129 sRNA candidates were identified in Brucella abortus 2308 in our previous work, and one candidate with potential to regulate expression of hemH gene was further analyzed in this study. We found that the novel sRNA can inhibit the expression of hemH and called it BsrH (Brucella sRNA regulating HemH). The expression level of BsrH was tested in four different stress conditions. A significant upregulation was detected during the growth in acidic and Brucella minimal media, as well as in the presence of hydroxyl peroxide, while iron deficiency caused the opposite effect. As expected, BsrH strongly affected the survival ratio of the Brucella cells under iron-limitation conditions, though overexpression of BsrH did not affect Brucella virulence. Thus, we conclude that BsrH plays a regulatory role in bacterial heme biosynthesis and can be considered as the first Brucella sRNA involved in stress responses.