AUTHOR=Ning Huanhuan , Liang Xuan , Xie Yanling , Bai Lu , Zhang Wei , Wang Lifei , Kang Jian , Lu Yanzhi , Ma Yanling , Bai Guangchun , Bai Yinlan 

TITLE=c-di-AMP Accumulation Regulates Growth, Metabolism, and Immunogenicity of Mycobacterium smegmatis

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.865045

DOI=10.3389/fmicb.2022.865045

ISSN=1664-302X

ABSTRACT=<p>Cyclic dimeric adenosine monophosphate (c-di-AMP) is a ubiquitous second messenger of bacteria involved in diverse physiological processes as well as host immune responses. <italic>MSMEG_2630</italic> is a c-di-AMP phosphodiesterase (<italic>cnpB</italic>) of <italic>Mycobacterium smegmatis</italic>, which is homologous to <italic>Mycobacterium tuberculosis Rv2837c</italic>. In this study, <italic>cnpB</italic>-deleted (Δ<italic>cnpB</italic>), -complemented (Δ<italic>cnpB</italic>::C), and -overexpressed (Δ<italic>cnpB</italic>::O) strains of <italic>M. smegmatis</italic> were constructed to investigate the role of c-di-AMP in regulating mycobacterial physiology and immunogenicity. This study provides more precise evidence that elevated c-di-AMP level resulted in smaller colonies, shorter bacteria length, impaired growth, and inhibition of potassium transporter in <italic>M. smegmatis</italic>. This is the first study to report that elevated c-di-AMP level could inhibit biofilm formation and induce porphyrin accumulation in <italic>M. smegmatis</italic> by regulating associated gene expressions, which may have effects on drug resistance and virulence of mycobacterium. Moreover, the <italic>cnpB</italic>-deleted strain with an elevated c-di-AMP level could induce enhanced Th1 immune responses after <italic>M. tuberculosis</italic> infection. Further, the pathological changes and the bacteria burden in Δ<italic>cnpB</italic> group were comparable with the wild-type <italic>M. smegmatis</italic> group against <italic>M. tuberculosis</italic> venous infection in the mouse model. Our findings enhanced the understanding of the physiological role of c-di-AMP in mycobacterium, and <italic>M. smegmatis cnpB</italic>-deleted strain with elevated c-di-AMP level showed the potential for a vaccine against tuberculosis.</p>