Kumbicins A–D: Bis-Indolyl Benzenoids and Benzoquinones from an Australian Soil Fungus, Aspergillus kumbius

A soil survey conducted in southern Queensland, Australia, identified a novel isolate belonging to the genus Aspergillus subgenus Circumdati section Circumdati, Aspergillus kumbius FRR6049. Cultivation and fractionation of secondary metabolites from A. kumbius revealed a unique chemotype comprising three new bis-indolyl benzenoids, kumbicins A–C, and a new bis-indolyl benzoquinone, kumbicin D, along with the previously reported compounds asterriquinol D dimethyl ether, petromurins C and D, aspochracin, its N-demethyl analogue JBIR-15, and neohydroxyaspergillic acid. The structures of kumbicins A–D were assigned by detailed spectroscopic analysis. Kumbicin C was found to inhibit the growth of mouse myeloma cells (IC50 0.74 μg mL–1) and the Gram-positive bacterium Bacillus subtilis (MIC 1.6 μg mL–1).

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Release factor-dependent ribosome rescue by BrfA in the Gram-positive bacterium Bacillus subtilis

Nature Communications ◽

10.1038/s41467-019-13408-7 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 5

Author(s):

Naomi Shimokawa-Chiba ◽

Claudia Müller ◽

Keigo Fujiwara ◽

Bertrand Beckert ◽

Koreaki Ito ◽

...

Keyword(s):

Bacillus Subtilis ◽

Stop Codon ◽

Release Factor ◽

Positive Bacterium ◽

Gram Positive ◽

E Coli ◽

Cryo Electron Microscopy ◽

Dead End ◽

Bacterium Bacillus Subtilis ◽

Bacterium Bacillus

AbstractRescue of the ribosomes from dead-end translation complexes, such as those on truncated (non-stop) mRNA, is essential for the cell. Whereas bacteria use trans-translation for ribosome rescue, some Gram-negative species possess alternative and release factor (RF)-dependent rescue factors, which enable an RF to catalyze stop-codon-independent polypeptide release. We now discover that the Gram-positive Bacillus subtilis has an evolutionarily distinct ribosome rescue factor named BrfA. Genetic analysis shows that B. subtilis requires the function of either trans-translation or BrfA for growth, even in the absence of proteotoxic stresses. Biochemical and cryo-electron microscopy (cryo-EM) characterization demonstrates that BrfA binds to non-stop stalled ribosomes, recruits homologous RF2, but not RF1, and induces its transition into an open active conformation. Although BrfA is distinct from E. coli ArfA, they use convergent strategies in terms of mode of action and expression regulation, indicating that many bacteria may have evolved as yet unidentified ribosome rescue systems.

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Inducible Transport of Citrate in a Gram-positive Bacterium, Bacillus subtilis

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)62427-5 ◽

1971 ◽

Vol 246 (4) ◽

pp. 1032-1040

Author(s):

Klaus Willecke ◽

Arthur B. Pardee

Keyword(s):

Bacillus Subtilis ◽

Positive Bacterium ◽

Gram Positive ◽

Bacterium Bacillus Subtilis ◽

Bacterium Bacillus

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ResQ, a release factor-dependent ribosome rescue factor in the Gram-positive bacterium Bacillus subtilis

10.1101/732420 ◽

2019 ◽

Author(s):

Naomi Shimokawa-Chiba ◽

Claudia Müller ◽

Keigo Fujiwara ◽

Bertrand Beckert ◽

Koreaki Ito ◽

...

Keyword(s):

Bacillus Subtilis ◽

Stop Codon ◽

Release Factor ◽

Active Conformation ◽

Positive Bacterium ◽

Gram Positive ◽

E Coli ◽

Dead End ◽

Bacterium Bacillus Subtilis ◽

Bacterium Bacillus

SummaryRescue of the ribosomes from dead-end translation complexes, such as those on truncated (non-stop) mRNA, is essential for the cell. Whereas bacteria use trans-translation for ribosome rescue, some Gram-negative species possess alternative and release factor (RF)-dependent rescue factors, which enable an RF to catalyze stop codon-independent polypeptide release. We now discover that the Gram-positive Bacillus subtilis has an evolutionarily distinct ribosome rescue factor named ResQ. Genetic analysis shows that B. subtilis requires the function of either trans-translation or ResQ for growth, even in the absence of proteotoxic stresses. Biochemical and cryo-EM characterization demonstrates that ResQ binds to non-stop stalled ribosomes, recruits homologous RF2, but not RF1, and induces its transition into an open active conformation. Although ResQ is distinct from E. coli ArfA, they use convergent strategies in terms of mode of action and expression regulation, indicating that many bacteria may have evolved as yet unidentified ribosome rescue systems.

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The Disulfide Stress Response and Protein S-thioallylation Caused by Allicin and Diallyl Polysulfanes in Bacillus subtilis as Revealed by Transcriptomics and Proteomics

Antioxidants ◽

10.3390/antiox8120605 ◽

2019 ◽

Vol 8 (12) ◽

pp. 605 ◽

Cited By ~ 4

Author(s):

Bui Khanh Chi ◽

Nguyen Thi Thu Huyen ◽

Vu Van Loi ◽

Martin Clemens Horst Gruhlke ◽

Marc Schaffer ◽

...

Keyword(s):

Bacillus Subtilis ◽

Stress Response ◽

Protein S ◽

Low Molecular Weight ◽

Positive Bacterium ◽

Translation Factors ◽

Proteome Level ◽

Phenotype Analysis ◽

Bacterium Bacillus Subtilis ◽

Bacterium Bacillus

Garlic plants (Allium sativum L.) produce antimicrobial compounds, such as diallyl thiosulfinate (allicin) and diallyl polysulfanes. Here, we investigated the transcriptome and protein S-thioallylomes under allicin and diallyl tetrasulfane (DAS4) exposure in the Gram-positive bacterium Bacillus subtilis. Allicin and DAS4 caused a similar thiol-specific oxidative stress response, protein and DNA damage as revealed by the induction of the OhrR, PerR, Spx, YodB, CatR, HypR, AdhR, HxlR, LexA, CymR, CtsR, and HrcA regulons in the transcriptome. At the proteome level, we identified, in total, 108 S-thioallylated proteins under allicin and/or DAS4 stress. The S-thioallylome includes enzymes involved in the biosynthesis of surfactin (SrfAA, SrfAB), amino acids (SerA, MetE, YxjG, YitJ, CysJ, GlnA, YwaA), nucleotides (PurB, PurC, PyrAB, GuaB), translation factors (EF-Tu, EF-Ts, EF-G), antioxidant enzymes (AhpC, MsrB), as well as redox-sensitive MarR/OhrR and DUF24-family regulators (OhrR, HypR, YodB, CatR). Growth phenotype analysis revealed that the low molecular weight thiol bacillithiol, as well as the OhrR, Spx, and HypR regulons, confer protection against allicin and DAS4 stress. Altogether, we show here that allicin and DAS4 cause a strong oxidative, disulfide and sulfur stress response in the transcriptome and widespread S-thioallylation of redox-sensitive proteins in B. subtilis. The results further reveal that allicin and polysulfanes have similar modes of actions and thiol-reactivities and modify a similar set of redox-sensitive proteins by S-thioallylation.

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