The Natural Antimicrobial trans-Cinnamaldehyde Interferes with UDP-N-Acetylglucosamine Biosynthesis and Cell Wall Homeostasis in Listeria monocytogenes

Abstract

Trans-cinnamaldehyde (t-CIN), an antimicrobial compound from cinnamon essential oil, is of interest because it inhibits various foodborne pathogens. In the present work, we investigated the antimicrobial mechanisms of t-CIN in Listeria monocytogenes using a previously isolated yvcK::Himar1 transposon mutant which shows hypersensitivity to t-CIN. Time-lapse microscopy revealed that t-CIN induces a bulging cell shape followed by lysis in the mutant. Complementation with wild-type yvcK gene completely restored the tolerance of yvcK::Himar1 strain to t-CIN and the cell morphology. Suppressor mutants which partially reversed the t-CIN sensitivity of the yvcK::Himar1 mutant were isolated from evolutionary experiments. Three out of five suppression mutations were in the glmU-prs operon and in nagR, which are linked to the biosynthesis of the peptidoglycan precursor uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc). GlmU catalyzes the last two steps of UDP-GlcNAc biosynthesis and NagR represses the uptake and utilization of N-acetylglucosamine. Feeding N-acetylglucosamine or increasing the production of UDP-GlcNAc synthetic enzymes fully or partially restored the t-CIN tolerance of the yvcK mutant. Together, these results suggest that YvcK plays a pivotal role in diverting substrates to UDP-GlcNAc biosynthesis in L. monocytogenes and that t-CIN interferes with this pathway, leading to a peptidoglycan synthesis defect.

Imbalance of peptidoglycan biosynthesis alters the cell surface charge of Listeria monocytogenes

“…Compared to the wildtype, the eslB mutant was more sensitive towards t -Cin and fosfomycin ( Fig. 3 ), which target the UDP-Glc N Ac biosynthetic pathway and MurA, respectively ( Marquardt et al, 1994 , Pensinger et al, 2021 , Sun et al, 2021 ). In contrast, the resistance towards d -cycloserine, nisin, vancomycin, moenomycin, penicillin, ampicillin and bacitracin ( Fig.…”

“…To identify the exact process of peptidoglycan biosynthesis, which is impaired in the eslB mutant, we performed a screen with antibiotics targeting different steps of this process. The absence of eslB only affected the resistance towards t -Cin and fosfomycin, which reduce the synthesis of UDP-Glc N Ac and inhibit MurA, respectively ( Marquardt et al, 1994 , Pensinger et al, 2021 , Sun et al, 2021 ). Surprisingly, we observed an increased resistance of the eslB mutant towards tunicamycin.…”

“…Recent findings suggest that the UDP-Glc N Ac biosynthetic pathway can be inhibited by trans -cinnamaldehyde ( t -Cin) ( Fig. 1 )( Pensinger et al, 2021 , Sun et al, 2021 ). UDP-Glc N Ac is also consumed by TarO/TagO, which catalyzes the first committed step for the synthesis of WTA ( Soldo et al, 2002 ).…”

Imbalance of peptidoglycan biosynthesis alters the cell surface charge of Listeria monocytogenes

“…Compared to the wildtype, the eslB mutant was more sensitive towards t -Cin and fosfomycin (Fig. 2), which target the UDP-Glc N Ac biosynthetic pathway and MurA, respectively (Marquardt et al, 1994; Pensinger et al, 2021; Sun et al, 2021). In contrast, the resistance towards D-cycloserine, nisin, vancomycin, moenomycin, penicillin, ampicillin and bacitracin (Fig.…”

“…Recent findings suggest that the UDP-Glc N Ac biosynthetic pathway can be inhibited by trans -cinnamaldehyde ( t -Cin) (Fig. 1)(Pensinger et al, 2021; Sun et al, 2021). UDP-Glc N Ac is also consumed by TarO/TagO, which catalyzes the first committed step for the synthesis of WTA (Soldo et al, 2002).…”