Thailandamide, a Fatty Acid Synthesis Antibiotic That Is Coexpressed with a Resistant Target Gene

Abstract

Microbes encode many uncharacterized gene clusters that may produce antibiotics and other bioactive small molecules. Methods for activating these genes are needed to explore their biosynthetic potential. A transposon containing an inducible promoter was randomly inserted into the genome of the soil bacterium to induce antibiotic expression. This screen identified the polyketide/nonribosomal peptide thailandamide as an antibiotic and discovered its regulator, AtsR. Mutants of resistant to thailandamide had mutations in the gene for acetyl coenzyme A (acetyl-CoA) carboxylase, which is one of the first enzymes in the fatty acid synthesis pathway. A second copy of in the thailandamide synthesis gene cluster keeps resistant to its own antibiotic. These genetic techniques will likely be powerful tools for discovering other unusual antibiotics.

Do Global Regulators Hold the Key to Production of Bacterial Secondary Metabolites?

“…thaC or accA-2 is responsible for resistance against Thailandamide (B. thailandensis and closely related species are resistant to Thailandamide). The presence of a second copy of accA (thaC) likely affords the resistance to Thailandamide, which further strengthens the inference that AccA is the target for Thailandamide [43,44], as cells that express thaC are less susceptible to Thailandamide activity. It is interesting to note that several Burkholderia spp., which lack the tha gene cluster still encode a thaC homolog [43].…”

“…This prompted the suggestion that the otherwise broad-spectrum activity of Thailandamide is limited by poor uptake in Gram-negative bacteria [43]. A study involving insertional mutation for characterization of new antibiotics revealed Thailandamide B to be the major product formed by B. thailandensis [44]; this is contrary to other analyses, where Thailandamide A was shown to be the major product [43,[45][46][47]. Thailandamide B was revealed to have bactericidal activity and it was shown to be toxic to human cells as well.…”

“…Further, in B. subtilis, over-expression of mutant AccA was sufficient to relieve the Thailandamide-induced inhibition. Thus, the cellular target for Thailandamide was suggested to be AccA protein or the AccA/AccD complex, which is involved in the first committed step of fatty-acid biosynthesis [43,44].…”

“…As noted below, increased AHL-dependent production of ScmR might explain such repression. Recently, it has been shown that transposon-mediated disruption of momS (BTH_I0633) led to increased production of Thailandamide B. MomS has 66% sequence identity to AtsR (Adhesion and Type Six Secretion System Regulator), which has been shown to be a global regulator in B. cenocepacia [44].…”

Current methods for inhibiting antibiotic resistant bacteria by targeting bacterial cell metabolism and disrupting antibiotic elimination through the AcrAB-Tolc efflux pump

“…Novel synthetic antibiotics as capistruin and malleilactone block bacterial cell transformation, inducing more antibiotic production from those bacterial cells. The antibiotic, bactobulin, can connect to the luxI-luxR proteins responsible for quorum sensing (Wozniak et al, 2018). The LuxI-R linkage to bactobulin stimulates a molecule that inhibits bacterial translation in the ribosome.…”