20 research outputs found
Insectâassociated bacteria assemble the antifungal butenolide gladiofungin by nonâcanonical polyketide chain termination
Genome mining of one of the protective symbionts ( Burkholderia gladioli ) of the invasive beetle Lagria villosa revealed a cryptic gene cluster that codes for the biosynthesis of a novel antifungal polyketide with a glutarimide pharmacophore. Targeted gene inactivation, metabolic profiling, and bioassays led to the discovery of the gladiofungins as previouslyâoverlooked components of the antimicrobial armory of the beetle symbiont, which are highly active against the entomopathogenic fungus Purpureocillium lilacinum . By mutational analyses, isotope labeling, and computational analyses of the modular polyketide synthase, we found that the rare butenolide moiety of gladiofungins derives from an unprecedented polyketide chain termination reaction involving a glycerolâderived C3 building block. The key role of an Aâfactor synthase (AfsA)âlike offloading domain was corroborated by CRISPRâCasâmediated gene editing, which facilitated precise excision within a PKS domain
Multimodal Molecular Imaging and Identification of Bacterial Toxins Causing Mushroom Soft Rot and Cavity Disease
Soft rot disease of edible mushrooms leads to rapid degeneration of fungal tissue and thus severely affects farming productivity worldwide. The bacterial mushroom pathogen Burkholderia gladioli pv. agaricicola has been identified as the cause. Yet, little is known about the molecular basis of the infection, the spatial distribution and the biological role of antifungal agents and toxins involved in this infectious disease. We combine genome mining, metabolic profiling, MALDI-Imaging and UV Raman spectroscopy, to detect, identify and visualize a complex of chemical mediators and toxins produced by the pathogen during the infection process, including toxoflavin, caryoynencin, and sinapigladioside. Furthermore, targeted gene knockouts and in vitro assays link antifungal agents to prevalent symptoms of soft rot, mushroom browning, and impaired mycelium growth. Comparisons of related pathogenic, mutualistic and environmental Burkholderia spp. indicate that the arsenal of antifungal agents may have paved the way for ancestral bacteria to colonize niches where frequent, antagonistic interactions with fungi occur. Our findings not only demonstrate the power of label-free, in vivo detection of polyyne virulence factors by Raman imaging, but may also inspire new approaches to disease control. © 2021 The Authors. ChemBioChem published by Wiley-VCH Gmb
Effect of Crystal Size on Framework Defects and Water Uptake in Fluoride Mediated Silicaliteâ1
The
relationship between framework defects and crystal size in
fluoride mediated silicalite-1 was investigated through nitrogen physisorption,
X-ray diffraction, and vapor adsorption of ethanol and water on samples
with crystal sizes ranging from 0.4 to 30 ÎŒm in the <i>b</i> direction of the silicalite-1 crystals. X-ray diffraction
reveals a shift in the lattice system from a predominantly monoclinic
phase in smaller crystals to an orthorhombic phase in the larger crystals. <sup>29</sup>Si MAS studies reveal minimal differences in framework silanol
defect concentration. An H-4 type hysteresis in 77 K N<sub>2</sub> adsorption isotherm and BdB-FHH pore size analysis reveal the presence
of slit-like pores and a larger average pore size as well as a larger
volume fraction of âmicrofissuresâ in the larger crystals.
Pure vapor adsorption measurements show more than a 2-fold increase
in water uptake from 0.21 mmol/g to 0.51 mmol/g from the smallest
to largest samples at 308 K near unit activity, while ethanol uptake
remains on the order of 2.4 mmol/g for all samples. An increase in
desorption hysteresis with crystal size and negligible differences
in isosteric heats of adsorption of water lend support to the presence
of microfissure defects in the larger samples. IAST predications for
binary adsorption of ethanol and water in the silicalite-1 samples
reveal a 2-fold ethanol/water selectivity enhancement for dilute (<5
wt % EtOH) solutions when crystal size is reduced. This systematic
study of N<sub>2</sub> physisorption, framework composition, and ethanol/water
adsorption highlights the critical role that crystal size plays in
the adsorption process, which can have significant implications for
biofuel processes that produce dilute aqueous ethanol as a raw product