Project description:Rapid modulation of gene expression is a key feature for the success of bacteria, particularly for those that rapidly have to adapt to different niches. The lifecycles of Photorhabdus and Xenorhabdus involve a mutualistic association with nematodes as well as an entomopathogenic phase1,2, both of which rely on the production of numerous specialized metabolites (SMs) 3,4. Several regulators have been previously implicated in the regulation of SM production in these genera3,4. However, the molecular underpinnings regulating SM production and the role of small regulatory RNAs (sRNAs) in this process are unknown. Here we describe the mechanism underlying RNA-mediated control of SM synthesis. We show that the Hfq-dependent sRNA, ArcZ, is an essential requirement for SM production. We discovered that ArcZ directly base-pairs with the mRNA encoding HexA, a key repressor of SM genes. We further demonstrate that the ArcZ regulon is not restricted to SM production, but rather modulates up to ~15% of the transcriptional output in both Photorhabdus and Xenorhabdus. Together, our study shows that sRNAs are crucial for SM production in these species, reveals previously unknown targets for biosynthetic pathway manipulations, and offers a new tool for the (over)production, isolation and identification of unknown natural products.
2020-08-25 | PXD019095 | Pride
Project description:Bacterial resistance against Siderophores
Project description:Iron is an essential cofactor for a wide range of cellular processes. Previous studies have shown that siderophore-mediated uptake and intracellular handling of iron are crucial for virulence of Aspergillus fumigatus. Here we show that the bzip-type transcription factor HapX plays a crucial role in the transcriptional remodeling required for adaption to iron starvation in this opportunistic fungal pathogen. HapX was found to be interconnected in a negative feed-back loop with the previously identified iron regulator SreA: SreA repressed expression of hapX during iron sufficiency and HapX repressed sreA during iron starvation. Genome-wide transcriptional profiling and analysis of selected metabolites (protophorphyrine IX, siderophores and amino acids) indicated extensive metabolic remodeling in response to iron starvation. HapX was found to participate in both, repression and activation of genes during iron starvation. HapX was in particular required for repression of iron-dependent and mitochondrial-localized activities including respiration, TCA cycle, amino acid metabolism, iron-sulfur-cluster biosynthesis and heme biosynthesis. Pathways positively affected by HapX included production of siderophores and the ribotoxin and major allergen AspF1. Analysis of the free amino acid pool revealed HapX-dependent coordination of the production of siderophores with the supply of its precursor ornithine. Consistent with the hapX expression pattern, HapX-deficiency was deleterious with respect to growth rate and conidiation during iron depleted but not iron-replete conditions. HapX-deficiency caused significant attenuation of virulence in a murine model aspergillosis underlining that A. fumigatus faces iron starvation in the host and that the HapX-dependent metabolic reprogramming is therefore crucial for virulence.
Project description:Xenorhabdus griffiniae was grown for 24 hours with and without being in close proximity to their host nematode Steinernema hermaphrodtium.
Project description:Iron is an essential cofactor for a wide range of cellular processes. Previous studies have shown that siderophore-mediated uptake and intracellular handling of iron are crucial for virulence of Aspergillus fumigatus. Here we show that the bzip-type transcription factor HapX plays a crucial role in the transcriptional remodeling required for adaption to iron starvation in this opportunistic fungal pathogen. HapX was found to be interconnected in a negative feed-back loop with the previously identified iron regulator SreA: SreA repressed expression of hapX during iron sufficiency and HapX repressed sreA during iron starvation. Genome-wide transcriptional profiling and analysis of selected metabolites (protophorphyrine IX, siderophores and amino acids) indicated extensive metabolic remodeling in response to iron starvation. HapX was found to participate in both, repression and activation of genes during iron starvation. HapX was in particular required for repression of iron-dependent and mitochondrial-localized activities including respiration, TCA cycle, amino acid metabolism, iron-sulfur-cluster biosynthesis and heme biosynthesis. Pathways positively affected by HapX included production of siderophores and the ribotoxin and major allergen AspF1. Analysis of the free amino acid pool revealed HapX-dependent coordination of the production of siderophores with the supply of its precursor ornithine. Consistent with the hapX expression pattern, HapX-deficiency was deleterious with respect to growth rate and conidiation during iron depleted but not iron-replete conditions. HapX-deficiency caused significant attenuation of virulence in a murine model aspergillosis underlining that A. fumigatus faces iron starvation in the host and that the HapX-dependent metabolic reprogramming is therefore crucial for virulence. A. fumigatus 293 and hapX mutants were grown in the presence and absence of iron and in cultures shifted from no iron to iron-containing conditions after 1 h incubation. Hybridizations were performed with biological replicates for wt vs hapX +/- iron. For the iron-shift experiments, there were biological replicates for wt in both conditions and for hapX in -iron but there was only a single biological sample for hapX iron-shift sample. All hybs were performed with flip-dye pairs.