Dataset Information

Screening for inhibitors of mutacin synthesis in Streptococcus mutans using fluorescent reporter strains.

ABSTRACT:

Background

Within the polymicrobial dental plaque biofilm, bacteria kill competitors by excreting mixtures of bacteriocins, resulting in improved fitness and survival. Inhibiting their bacteriocin synthesis might therefore be a useful strategy to eliminate specific pathogens. We used Streptococcus mutans, a highly acidogenic inhabitant of dental plaque, as a model and searched for natural products that reduced mutacin synthesis. To this end we fused the promoter of mutacin VI to the GFP+ gene and integrated the construct into the genome of S. mutans UA159 by single homologous recombination.

Results

The resulting reporter strain 423p - gfp?+ was used to screen 297 secondary metabolites from different sources, mainly myxobacteria and fungi, for their ability to reduce the fluorescence of the fully induced reporter strain by >?50% while growth was almost unaffected (>?90% of control). Seven compounds with different chemical structures and different modes of action were identified. Erinacine C was subsequently validated and shown to inhibit transcription of all three mutacins of S. mutans. The areas of the inhibition zones of the sensor strains S. sanguinis and Lactococcus lactis were reduced by 35% to 61% in comparison to controls in the presence of erinacine C, demonstrating that the amount of active mutacins in the culture supernatants of S. mutans was reduced. Erinacines are cyathane diterpenes that were extracted from cultures of the edible mushroom Hericium erinaceus. They have anti-inflammatory, antimicrobial and neuroprotective effects. For erinacine C, a new biological activity was found here.

Conclusions

We demonstrate the successful development of a whole-cell fluorescent reporter for the screening of natural compounds and report that erinacine C suppresses mutacin synthesis in S. mutans without affecting cell viability.

SUBMITTER: Premnath P

PROVIDER: S-EPMC5870221 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Publications

Screening for inhibitors of mutacin synthesis in Streptococcus mutans using fluorescent reporter strains.

Premnath Priyanka P Reck Michael M Wittstein Kathrin K Stadler Marc M Wagner-Döbler Irene I

BMC microbiology 20180327 1

<h4>Background</h4>Within the polymicrobial dental plaque biofilm, bacteria kill competitors by excreting mixtures of bacteriocins, resulting in improved fitness and survival. Inhibiting their bacteriocin synthesis might therefore be a useful strategy to eliminate specific pathogens. We used Streptococcus mutans, a highly acidogenic inhabitant of dental plaque, as a model and searched for natural products that reduced mutacin synthesis. To this end we fused the promoter of mutacin VI to the GFP+ ...[more]

PMID: 29580208

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Project description:UNLABELLED:Lantibiotics are ribosomally synthesized peptide antibiotics composed of an N-terminal leader peptide that is cleaved to yield the active antibacterial peptide. Significant advancements in molecular tools that promote the study of lantibiotic biosynthesis can be used in Streptococcus mutans. Herein, we further our understanding of leader peptide sequence and core peptide structural requirements for the biosynthesis and transport of the lantibiotic mutacin 1140. Our study on mutacin 1140 biosynthesis shows a dedicated secondary cleavage site within the leader peptide and the dependency of transport on core peptide posttranslational modifications (PTMs). The secondary cleavage site on the leader peptide is found at the -9 position, and secondary cleavage occurs before the core peptide is transported out of the cell. The coordinated cleavage at the -9 position was absent in a lanT deletion strain, suggesting that the core peptide interaction with the LanT transporter enables uniform cleavage at the -9 position. Following transport, the LanP protease was found to be tolerant to a wide variety of amino acid substitutions at the primary leader peptide cleavage site, with the exception of arginine at the -1 position. Several leader and core peptide mutations produced core peptide variants that had intermediate stages of PTM enzyme modifications, supporting the concept that PTM enzyme modifications, secondary cleavage, and transport are occurring in a highly coordinated fashion. IMPORTANCE:Mutacin 1140 belongs to the class I lantibiotic family of ribosomally synthesized and posttranslationally modified peptides (RiPPs). The biosynthesis of mutacin 1140 is a highly efficient process which does not lead to a discernible level of production of partially modified core peptide variants. The products isolated from an extensive mutagenesis study on the leader and core peptides of mutacin 1140 show that the posttranslational modifications (PTMs) on the core peptide occur under a highly coordinated dynamic process. PTMs are dictated by the distance of the core peptide modifiable residues from PTM enzyme active sites. The formation of lanthionine rings aids in the formation of successive PTMs, as was observed in a peptide variant lacking a C-terminal decarboxylation.

Dataset Information

Screening for inhibitors of mutacin synthesis in Streptococcus mutans using fluorescent reporter strains.

Background

Results

Conclusions

Publications

Screening for inhibitors of mutacin synthesis in Streptococcus mutans using fluorescent reporter strains.

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