Project description:Xenorhabdus nematophila is a Gram-negative bacterium, mutually associated with the soil nematode Steinernema carpocapsae and this nematobacterial complex is parasitic for a broad spectrum of insects. The transcriptional regulator OxyR is widely conserved in bacteria, but the OxyR regulon can vary significantly between species. OxyR activates the transcription of a set of genes that influence cellular defense against oxidative stress. It is also involved in the virulence of several bacterial pathogens. The aim of this study was to identify the X. nematophila OxyR regulon and investigate its role in the bacterial life cycle. An oxyR-mutant was constructed in X. nematophila and phenotypically characterized in vitro and in vivo after reassociation with its nematode partner. OxyR plays a major role during the X. nematophila resistance to oxidative stress in vitro. Transcriptome analysis allowed the identification of 59 genes differentially regulated in the oxyR mutant compared to the parental strain. In vivo, the oxyR mutant was able to reassociate with the nematode as efficiently as the control strain. These nematobacterial complexes harboring the oxyR mutant symbiont were able to rapidly kill the insect larvae in less than 48h after infestation, suggesting that factors other than OxyR could also allow X. nematophila to cope with oxidative stress encountered during this phase of infection in insect. The significant increased number of offspring of the nematobacterial complex when reassociated with the X. nematophila oxyR mutant compared to the control strain, revealed a potential role of OxyR during this symbiotic stage of the bacterial life-cycle.
Project description:Protein secretion into extracellular space is an important virulence mechanism both among Gram negative and Gram-positive bacteria. Prevotella intermedia, an important species associated with periodontitis, is known to be resistant to several antibiotics. Since P. intermedia is a part of normal oral microbiota, its complete elimination is not possible. Despite the remarkable clinical significance P. intermedia has, little is known about the molecular basis for its virulence. The aim of this study was to characterize the secretome of P. intermedia in biofilm and planktonic life mode. Proteins in the secretome preparations were identified by nanoLC-ESI-MS/MS. The biofilm secretome showed 109 proteins while the planktonic secretome showed 136 proteins. The biofilm and the planktonic secretomes contained 17 and 33 signal-peptide bearing proteins, 13 and 18 lipoproteins, respectively. Proteins with predicted virulence potential were 39 in biofilm and 44 in planktonic secretomes, respectively. Gene ontology analysis revealed that the biofilm secretome displayed a markedly higher percent proteins compared to planktonic secretome in terms of cellular amino acid metabolic process, nitrogen compound metabolic process, protein binding and methyltransferase and kinase activities. In conclusion, this study revealed differences in the protein profiles of P. intermedia biofilm and planktonic secretomes. This may set a basis for asking further questions into molecular mechanisms how this species exerts its virulence potential in the oral cavity.
Project description:Series of DNA microarrays (4) comparing the M. catarrhalis strain 035E and M. catarrhalis oxyR mutant response to 50 mM hydrogen peroxide. Wild-type cells and oxyR mutant cells were exposed to 50 mM hydrogen peroxide for 15 minutes. RNA was extracted and DNA microarray analysis performed. 4 biologic replicates were studied. One dye swap was included in this series analysis. Control oxyR mutant cells exposed to water
Project description:The study aimed to identify role of OxyR during growth on different electron acceptors when E. coli are growing anaerobically. Wt and OxyR null cells were grown on nitrate and fumarate medium anaerobically. Each condition was done in duplicate. RNA was extracted using Qiagen RNeasy kit after stabilization of RNA with RNA protect bacteria reagent. Hybridization and further processing was done based on Affymetrix protocols on E. coli Genome 2.0 arrays.
