AUTHOR=Shi Hongmei , Li Ting , Xu Jintian , Yu Jifang , Yang Shanshan , Zhang Xian-En , Tao Shengce , Gu Jing , Deng Jiao-Yu 

TITLE=MgrB Inactivation Confers Trimethoprim Resistance in Escherichia coli

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.682205

DOI=10.3389/fmicb.2021.682205

ISSN=1664-302X

ABSTRACT=<p>After several decades of use, trimethoprim (TMP) remains one of the key access antimicrobial drugs listed by the World Health Organization. To circumvent the problem of trimethoprim resistance worldwide, a better understanding of drug-resistance mechanisms is required. In this study, we screened the single-gene knockout library of <italic>Escherichia coli</italic>, and identified <italic>mgrB</italic> and other several genes involved in trimethoprim resistance. Subsequent comparative transcriptional analysis between Δ<italic>mgrB</italic> and the wild-type strain showed that expression levels of <italic>phoP</italic>, <italic>phoQ</italic>, and <italic>folA</italic> were significantly upregulated in Δ<italic>mgrB</italic>. Further deleting <italic>phoP</italic> or <italic>phoQ</italic> could partially restore trimethoprim sensitivity to Δ<italic>mgrB</italic>, and co-overexpression of <italic>phoP/Q</italic> caused TMP resistance, suggesting the involvement of PhoP/Q in trimethoprim resistance. Correspondingly, MgrB and PhoP were shown to be able to modulated <italic>folA</italic> expression <italic>in vivo</italic>. After that, efforts were made to test if PhoP could directly modulate the expression of <italic>folA</italic>. Though phosphorylated PhoP could bind to the promotor region of <italic>folA in vitro</italic>, the former only provided a weak protection on the latter as shown by the DNA footprinting assay. In addition, deleting the deduced PhoP box in Δ<italic>mgrB</italic> could only slightly reverse the TMP resistance phenotype, suggesting that it is less likely for PhoP to directly modulate the transcription of <italic>folA</italic>. Taken together, our data suggested that, in <italic>E. coli</italic>, MgrB affects susceptibility to trimethoprim by modulating the expression of <italic>folA</italic> with the involvement of PhoP/Q. This work broadens our understanding of the regulation of folate metabolism and the mechanisms of TMP resistance in bacteria.</p>