Affiliation:
1. Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
2. National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
Abstract
ABSTRACT
Co-trimoxazole, a fixed-dose combination of sulfamethoxazole (SMX) and trimethoprim (TMP), has been used for the treatment of bacterial infections since the 1960s. Since it has long been assumed that the synergistic effects between SMX and TMP are the consequence of targeting 2 different enzymes of bacterial folate biosynthesis, 2 genes (
pabB
and
nudB
) involved in the folate biosynthesis of
Escherichia coli
were deleted, and their effects on the susceptibility to antifolates were tested. The results showed that the deletion of
nudB
resulted in a lag of growth in minimal medium and increased susceptibility to both SMX and TMP. Moreover, deletion of
nudB
also greatly enhanced the bactericidal effect of TMP. To elucidate the mechanism of how the deletion of
nudB
affects the bacterial growth and susceptibility to antifolates, 7,8-dihydroneopterin and 7,8-dihydropteroate were supplemented into the growth medium. Although those metabolites could restore bacterial growth, they had no effect on susceptibilities to the antifolates. Reverse mutants of the
nudB
deletion strain were isolated to further study the mechanism of how the deletion of
nudB
affects susceptibility to antifolates. Targeted sequencing and subsequent genetic studies revealed that the disruption of the tetrahydromonapterin biosynthesis pathway could reverse the phenotype caused by the
nudB
deletion. Meanwhile, overexpression of
folM
could also lead to increased susceptibility to both SMX and TMP. These data suggested that the deletion of
nudB
resulted in the excess production of tetrahydromonapterin, which then caused the increased susceptibility to antifolates. In addition, we found that the deletion of
nudB
also resulted in increased susceptibility to both SMX and TMP in
Salmonella enterica
. Since dihydroneopterin triphosphate hydrolase is an important component of bacterial folate biosynthesis and the tetrahydromonapterin biosynthesis pathway also exists in a variety of bacteria, it will be interesting to design new compounds targeting dihydroneopterin triphosphate hydrolase, which may inhibit bacterial growth and simultaneously potentiate the antimicrobial activities of antifolates targeting other components of folate biosynthesis.
Funder
National Natural Science Foundation of China
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
6 articles.
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