Integrated proteomic and metabolomic analysis reveals that rhodomyrtone reduces the capsule in Streptococcus pneumoniae

Abstract

The emergence of antibiotic-resistant pathogenic bacteria is a healthcare problem worldwide. We evaluated the antimicrobial activity of rhodomyrtone, an acylphloroglucinol present in Rhodomyrtus tomentosa leaves, against the human Gram-positive pathogen Streptococcus pneumoniae. The compound exhibited pronounced anti-pneumococcal activity against a broad collection of clinical isolates. We studied the effects at the molecular level by integrated proteomic and metabolomic analysis. The results revealed alterations in enzymes and metabolites involved in several metabolic pathways including amino acid biosynthesis, nucleic acid biosynthesis, glucid, and lipid metabolism. Notably, the levels of two enzymes (glycosyltransferase and UTP-glucose-1-phosphate uridylyltransferase) and three metabolites (UDP-glucose, UDP-glucuronic acid and UDP-N-acetyl-D-galactosamine) participating in the synthesis of the pneumococcal capsule clearly diminished in the bacterial cells exposed to rhodomyrtone. Rhodomyrtone-treated pneumococci significantly possessed less amount of capsule, as measured by a colorimetric assay and visualized by electron microscopy. These findings reveal the utility of combining proteomic and metabolomic analyses to provide insight into phenotypic features of S. pneumoniae treated with this potential novel antibiotic. This can lead to an alternative antibiotic for the treatment of S. pneumoniae infections, because of the growing concern regarding antimicrobial resistance.

Antibacterial mechanism of rhodomyrtone involves the disruption of nucleoid segregation checkpoint in Streptococcus suis

“…Antibacterial activity of rhodomyrtone against S. suis was in the same range (0.5-2 µg/ml) in other pathogenic Gram-positive bacteria such as S. pneumoniae, S. pyogenes, S. aureus and B. subtilis (Limsuwan et al 2011;Mitsuwan et al 2017;Sianglum et al 2011 and. In this study, rhodomyrtone had antibacterial potency equivalent to common and effective drug used for treatment of S. suis infection such as penicillin, ampicillin and vancomycin.…”

Peer Review #1 of "Multi-omic profiling to assess the effect of iron starvation in Streptococcus pneumoniae TIGR4 (v0.1)"

“…There are very few studies on metabolomics in bacteria. We have recently published a work of proteomics and metabolomics integration in the pneumococcus to study the effect of an antimicrobial compound (Mitsuwan et al 2017). Very recently, Leonard and colleagues have described the metabolome inventory of a non-encapsulated S. pneumoniae TIGR4 in a chemically-defined medium, and using three techniques: 1 H-NMR, HPLC-MS and GC-MS (Leonard et al 2018).…”

“…Spots excision, protein digestion, peptide desalting and mass spectrometry analysis was performed as already described by our group (Mitsuwan et al 2017) with slight modifications: after mass spectra acquisition using a MALDI-TOF/TOF (4800 Proteomics Analyzer, Applied Biosystems) mass spectrometer in the m/z range 800 to 4,000, Mascot 2.0 search engine (Matrix Science Ltd., London) was used for protein identification running on GPS Explorer TM software v3.5 (Applied Biosystems) over the National Center for Biotechnology Information (NCBI) protein database (updated monthly). Search setting allowed one missed cleavage with the selected trypsin enzyme, Streptococcus pneumoniae for taxonomy restrictions, cysteine carbamidomethylation as a fixed modification, methionine oxidation as a variable modification, a MS/MS fragment tolerance of 0.2 Da, and a precursor mass tolerance of 10 ppm.…”

Multi-omic profiling to assess the effect of iron starvation inStreptococcus pneumoniaeTIGR4

“…Total cellular proteins and secreted proteins were obtained as described ( Mitsuwan et al, 2017 ). Briefly, to obtain cellular proteins, pellets were washed three times in sterile phosphate buffered saline (PBS) pH 7.4.…”