Project description:Investigation of whole genome gene expression to identify overlooked sRNAs and sORFs. Background The completion of numerous genome sequences has introduced an era of whole-genome study. However, many real genes, including small RNAs (sRNAs) and small ORFs (sORFs), are missed in genome annotation. In order to improve genome annotation, we sought to identify novel sRNAs and sORFs in Shigella, the principal etiologic agents of bacillary dysentery or shigellosis. Results Firstly, we identified 64 sRNAs in Shigella which is experimentally validated in other bacteria based on sequence conservation. Secondly, among possible approaches to search for sRNAs, we employed computer-based and tiling array based methods, followed by RT-PCR and northern blots. This allowed us to identify 12 sRNAs in Shigella flexneri strain 301. We also find 29 candidate sORFs. Conclusions This investigation provides an updated and comprehensive annotation of the Shigella genome, increases the expected numbers of sORFs and sRNAs with the corresponding impact on future functional genomics and proteomics studies. Our method can be used for the large scale reannotation of sRNAs and sORFs in any microbe whose genome sequence is available.
Project description:Investigation of whole genome gene expression to identify overlooked sRNAs and sORFs. Background The completion of numerous genome sequences has introduced an era of whole-genome study. However, many real genes, including small RNAs (sRNAs) and small ORFs (sORFs), are missed in genome annotation. In order to improve genome annotation, we sought to identify novel sRNAs and sORFs in Shigella, the principal etiologic agents of bacillary dysentery or shigellosis. Results Firstly, we identified 64 sRNAs in Shigella which is experimentally validated in other bacteria based on sequence conservation. Secondly, among possible approaches to search for sRNAs, we employed computer-based and tiling array based methods, followed by RT-PCR and northern blots. This allowed us to identify 12 sRNAs in Shigella flexneri strain 301. We also find 29 candidate sORFs. Conclusions This investigation provides an updated and comprehensive annotation of the Shigella genome, increases the expected numbers of sORFs and sRNAs with the corresponding impact on future functional genomics and proteomics studies. Our method can be used for the large scale reannotation of sRNAs and sORFs in any microbe whose genome sequence is available. Study using total RNA recovered from five conditions.
Project description:Background Compelling evidence indicates that Shigella species, the etiologic agents of bacillary dysentery, as well as enteroinvasive Escherichia coli, are derived from multiple origins of Escherichia coli and form a single pathovar. To further understand the genome diversity and virulence evolution of Shigella, comparative genomic hybridization microarray analysis was employed to compare the gene content of E. coli K-12 with those of 43 Shigella strains from all serotypes. Results For the 43 strains subjected to CGH microarray analyses, the common backbone of the Shigella genome was estimated to contain more than 1,900 open reading frames, with a mean number of 729 undetectable ORFs. The mosaic distribution of absent regions indicated that insertions and/or deletions have led to the highly diversified genomes of pathogenic strains. Conclusion These results support the hypothesis that by gain and loss of functions, Shigella species became successful human pathogens through convergent evolution from diverse genomic backgrounds. Moreover, we also found many specific differences between different lineages, providing a window into understanding bacterial speciation and taxonomic relationships. Keywords: comparative genomic hybridization
Project description:Virulent bacteriophages (or phages) are viruses that specifically infect and lyse a bacterial host. When multiple phages co-infect a bacterial host, the extent of lysis, dynamics of bacteria-phage and phage-phage interactions are expected to vary. The objective of this study is to identify the factors influencing the interaction of two virulent phages with different Pseudomonas aeruginosa growth states (planktonic, an infected epithelial cell line, and biofilm) by measuring the bacterial time-kill and individual phage replication kinetics. A single administration of phages effectively reduced P. aeruginosa viability in planktonic conditions and infected human lung cell cultures, but phage-resistant variants subsequently emerged. In static biofilms, the phage combination displayed initial inhibition of biofilm dispersal, but sustained control was achieved only by combining phages and meropenem antibiotic. In contrast, adherent biofilms showed tolerance to phage and/or meropenem, suggesting a spatiotemporal variation in the phage-bacterial interaction. The kinetics of adsorption of each phage to P. aeruginosa during single- or co-administration were comparable. However, the phage with the shorter lysis time depleted bacterial resources early and selected a specific nucleotide polymorphism that conferred a competitive disadvantage and cross-resistance to the second phage. The extent and strength of this phage-phage competition and genetic loci conferring phage resistance, are, however, P. aeruginosa genotype dependent. Nevertheless, adding phages sequentially resulted in their unimpeded replication with no significant increase in bacterial host lysis. These results highlight the interrelatedness of phage-phage competition, phage resistance and specific bacterial growth state (planktonic/biofilm) in shaping the interplay among P. aeruginosa and virulent phages.