Project description:Burkholderia species are associated with several life-threatening human infections, often resulting in high morbidity and mortality rates due to their innate resistance to antibiotics. To improve clinical outcomes, new therapies targeting conserved, yet unique, Burkholderia pathways are needed. One such pathway is the Burkholderia O-linked protein glycosylation system, essential for virulence in Burkholderia cenocepacia and Burkholderia pseudomallei. This system relies on the O-Glycosylation gene Cluster (OGC), a five-gene cluster sufficient and required for the generation of a trisaccharide Gal-GalNAc-GalNAc used for protein glycosylation, and the distally encoded oligosaccharyltransferase, pglL, responsible for ligating glycans to glycoproteins. Previous work has shown that the OGC cluster can be removed, but individual mutations associated with late-stage glycan biosynthesis are essential. Here, we explore the essentiality of late-stage O-linked glycan biosynthesis in B. cenocepacia, revealing that the completion and translocation of the O-linked trisaccharide is necessary for viability and bacterial fitness. Using inducible systems, we demonstrate toxicity dependent on multiple OGC genes and the initiation of O-linked glycan biosynthesis. Upon loss of late-stage biosynthesis, mutants exhibit notable growth defects and profound sensitivity to stresses. Proteomics and glycoproteomic analysis show that blocking late-stage glycan biosynthesis inhibits protein glycosylation and drives large membrane proteomic changes. Finally, we demonstrate that OGC mediated toxicity is not limited to blockages but can also occur via the overexpression of steps within O-linked glycan biosynthesis. Combined, these findings suggest that the O-linked glycan biosynthesis pathway of B. cenocepacia is extremely sensitive to dysregulation and may be an ideal target for the development of antimicrobial therapies.
Project description:DPANN are a widespread and highly diverse group of archaea characterised by their small size, reduced genome, limited metabolic pathways, and symbiotic existence. DPANNs are predominantly obligate ectosymbionts that depend on their host for their survival and proliferation. Despite the recent expansion in this clade, the structural and molecular details of host recognition, host-DPANN intercellular communication, and host adaptation in response to DPANN attachment remain unknown. Here, we used electron cryotomography (cryo-ET) to reveal that the Candidatus Micrarchaeota” (ARM-1) interacts with its host through intercellular proteinaceous nanotubes. These tubes (~4.5 nm wide) originate in the host, extend all the way to the DPANN cytoplasm and act like tunnels for intercellular exchange. Combining cryo-ET and sub-tomogram averaging, we revealed the in situ architectures of host and DPANN S-layers and the structures of the nanotubes in their primed and extended states, providing mechanistic insights into substrate exchange. Additionally, we performed comparative proteomics and genomic analyses to identify host proteomic changes in response to the DPANN attachment. Our results showed striking alterations in host-proteome during symbiosis and upregulation/downregulation of key cellular pathways. Collectively, these results provided unprecedented insights into the structural basis of host-DPANN communication and deepen our understanding of the host ectosymbiotic relationships.
Project description:Burkholderia species are associated with several life-threatening human infections, often resulting in high morbidity and mortality rates due to their innate resistance to antibiotics. To improve clinical outcomes, new therapies targeting conserved, yet unique, Burkholderia pathways are needed. One such pathway is the Burkholderia O-linked protein glycosylation system, essential for virulence in Burkholderia cenocepacia and Burkholderia pseudomallei. This system relies on the O-Glycosylation gene Cluster (OGC), a five-gene cluster sufficient and required for the generation of a trisaccharide β-Gal-(1,3)–α-GalNAc-(1,3)–β-GalNAc used for protein glycosylation, and the distally encoded oligosaccharyltransferase, pglL, responsible for ligating glycans to glycoproteins. Previous work has shown that the OGC cluster can be removed, but individual mutations associated with late-stage glycan biosynthesis are essential. Here, we explore the essentiality of late-stage O-linked glycan biosynthesis in B. cenocepacia, revealing that the completion and translocation of the O-linked trisaccharide is necessary for viability and bacterial fitness. Using inducible systems, we demonstrate toxicity dependent on multiple OGC genes and the initiation of O-linked glycan biosynthesis. Upon loss of late-stage biosynthesis, mutants exhibit notable growth defects and profound sensitivity to stresses. Proteomics and glycoproteomic analysis show that blocking late-stage glycan biosynthesis inhibits protein glycosylation and drives large membrane proteomic changes. Finally, we demonstrate that OGC mediated toxicity is not limited to blockages but can also occur via the overexpression of steps within O-linked glycan biosynthesis. Combined, these findings suggest that the O-linked glycan biosynthesis pathway of B. cenocepacia is extremely sensitive to dysregulation and may be an ideal target for the development of antimicrobial therapies.
Project description:Levoglucosan is produced in the pyrolysis of cellulose and starch, including from bushfires or the burning of biofuels, and is deposited from the atmosphere across the surface of the earth. We describe two levoglucosan degrading Paenarthrobacter spp. (Paenarthrobacter nitrojuajacolis LG01 and Paenarthrobacter histidinolovorans LG02) that were isolated by metabolic enrichment on levoglucosan as sole carbon source. Genome sequencing and proteomics analysis revealed expression of a series of gene clusters encoding known levoglucosan degrading enzymes, levoglucosan dehydrogenase (LGDH, LgdA), 3-keto-levoglucosan b-eliminase (LgdB1) and glucose 3-dehydrogenase (LgdC), along with an ABC transporter cassette and associated solute binding protein. However, no homologues of 3-ketoglucose dehydratase (LgdB2) were evident. The expressed gene clusters contained a range of putative sugar phosphate isomerase/xylose isomerases with weak similarity to LgdB2. Sequence similarity network analysis of genome neighbors revealed that homologues of LgdA, LgdB1 and LgdC are generally conserved in a range of bacteria in the phyla Firmicutes, Actinobacteria and Proteobacteria. One sugar phosphate isomerase/xylose isomerase cluster (LgdB3) was identified with limited distribution mutually exclusive with LgdB2. LgdB1, LgdB2 and LgdB3 adopt similar predicted 3D folds suggesting overlapping function in processing intermediates in LG metabolism. Our findings highlight the diversity within the LGDH pathway through which bacteria utilize levoglucosan as a nutrient source.
Project description:Comparative proteomics of Bacteroides thetaiotaomicron samples comparing the total membrane (TM) and outer membrane vesicles (OMV) of WT B. thetaiotaomicron and delta 4364