Unknown,Transcriptomics,Genomics,Proteomics

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Processing-Independent CRISPR RNAs Limit Natural Transformation in Neisseria meningitidis

ABSTRACT: In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis. dRNA-seq approach for RNA samples from cultures of N. lactamica 020-06, harvested at mid-log. Two cDNA libraries from total RNA were prepared to distinguish between transcripts with either primary orprocessed 5’ ends: one library is generated from untreated RNA, whereas the other is treated with terminator exonuclease (TEX),

ORGANISM(S): Neisseria lactamica 020-06

SUBMITTER: Konrad Förstner

PROVIDER: E-GEOD-44582 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Baart2007 - Genome-scale metabolic network of Neisseria meningitidis (iGB555) This model is described in the article: Modeling Neisseria meningitidis metabolism: from genome to metabolic fluxes. Baart GJ, Zomer B, de Haan A, van der Pol LA, Beuvery EC, Tramper J, Martens DE. Genome Biol. 2007; 8(7): R136 Abstract: BACKGROUND: Neisseria meningitidis is a human pathogen that can infect diverse sites within the human host. The major diseases caused by N. meningitidis are responsible for death and disability, especially in young infants. In general, most of the recent work on N. meningitidis focuses on potential antigens and their functions, immunogenicity, and pathogenicity mechanisms. Very little work has been carried out on Neisseria primary metabolism over the past 25 years. RESULTS: Using the genomic database of N. meningitidis serogroup B together with biochemical and physiological information in the literature we constructed a genome-scale flux model for the primary metabolism of N. meningitidis. The validity of a simplified metabolic network derived from the genome-scale metabolic network was checked using flux-balance analysis in chemostat cultures. Several useful predictions were obtained from in silico experiments, including substrate preference. A minimal medium for growth of N. meningitidis was designed and tested successfully in batch and chemostat cultures. CONCLUSION: The verified metabolic model describes the primary metabolism of N. meningitidis in a chemostat in steady state. The genome-scale model is valuable because it offers a framework to study N. meningitidis metabolism as a whole, or certain aspects of it, and it can also be used for the purpose of vaccine process development (for example, the design of growth media). The flux distribution of the main metabolic pathways (that is, the pentose phosphate pathway and the Entner-Douderoff pathway) indicates that the major part of pyruvate (69%) is synthesized through the ED-cleavage, a finding that is in good agreement with literature. This model is hosted on BioModels Database and identified by: MODEL1507180069. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Campylobacter jejuni is currently the leading cause of bacterial gastroenteritis in humans. Comparison of multiple Campylobacter strains revealed a high genetic and phenotypic diversity. However, little is known about differences in transcriptome organization, gene expression, and small RNA (sRNA) repertoires. Here we present the first comparative primary transcriptome analysis based on the differential RNAM-bM-^@M-^Sseq (dRNAM-bM-^@M-^Sseq) of four C. jejuni isolates. Our approach includes a novel, generic method for the automated annotation of transcriptional start sites (TSS), which allowed us to provide genome-wide promoter maps in the analyzed strains. These global TSS maps are refined through the integration of a SuperGenome approach that allows for a comparative TSS annotation by mapping RNAM-bM-^@M-^Sseq data of multiple strains into a common coordinate system derived from a whole-genome alignment. Considering the steadily increasing amount of RNAM-bM-^@M-^Sseq studies, our automated TSS annotation will not only facilitate transcriptome annotation for a wider range of pro- and eukaryotes but can also be adapted for the analysis among different growth or stress conditions. Our comparative dRNAM-bM-^@M-^Sseq analysis revealed conservation of most TSS, but also single-nucleotide-polymorphisms (SNP) in promoter regions, which lead to strain-specific transcriptional output. Furthermore, we identified strain-specific sRNA repertoires that could contribute to differential gene regulation among strains. In addition, we identified a novel minimal CRISPR-system in Campylobacter of the type-II CRISPR subtype, which relies on the host factor RNase III and a trans-encoded sRNA for maturation of crRNAs. This minimal system of Campylobacter, which seems active in only some strains, employs a unique maturation pathway, since the crRNAs are transcribed from individual promoters in the upstream repeats and thereby minimize the requirements for the maturation machinery. Overall, our study provides new insights into strain-specific transcriptome organization and sRNAs, and reveals genes that could modulate phenotypic variation among strains despite high conservation at the DNA level. Our dRNA-seq study of multiple C. jejuni strains represents the first comparative analysis of the primary transcriptomes of multiple strains and provides new insights into riboregulation in this bacterial pathogen.

Project description:Background: Prokaryotes have relatively small genomes, densely-packed and apparently dominated by protein-encoding sequences. However, data now generated by high throughput RNA sequencing (RNA-seq) reveal surprisingly more-complex transcriptomes with many previously unrecognized and unanticipated non-coding small and antisense transcripts. To date, such studies have investigated primarily Bacteria. Here, we report the transcripts present in ThermococcusM-BM- kodakarensis, a model hyperthermophilic Archaeon, synthesized under different growth and metabolic conditions. Results: cDNA libraries, generated from RNA preparations isolated from cells growing in media with sulfur or pyruvate, with sulfur to stationary phase, and growing with pyruvate but with sulfur added 20 min before RNA isolation, have been deep-sequenced. The results identify >2,700 sites of transcription initiation, establish a genome-wide map of transcripts, and consensus sequences for transcription initiation and post-transcription regulatory elements in T. kodakarensis. Primary transcription start sites (TSS) are identified upstream of 1,254 annotated genes, including ~78M-BM- % of those predicted by promoter locations, and an additional 644 primary TSS and their promoters have been identified within genes. Most of the mRNAs have a 5'-untranslated region (5'-UTR) between 10 and 50 nt long (median length = 16 nt), ~20 % have 5'-UTRs from 50 to 300 nt long, ~14 % are leaderless with 5'-UTRs M-bM-^IM-$8 nt, and ~50% contain a consensus ribosome binding sequence. The results also identify TSS for 1,018 antisense transcripts, most with sequences complementary to either the 5'- or 3'-region of a sense mRNA. The data confirm the presence of transcripts from all three CRISPR loci, the RNase P and 7S RNAs, all tRNAs and rRNAs and 69 snoRNAs predicted to be encoded in the T. kodakarensis genome. Two transcripts, putatively identified as riboswitches, were present in RNA preparations isolated from growing but not from stationary phase cells. The procedure used is designed to identify TSS but, assuming that the number of cDNA reads correlates with transcript abundance, the data obtained also provide a semi-quantitative overview of global operon expression. They document substantial differences in gene expression under different physiological conditions and are consistent with previous observations of substrate-dependent specific gene expression. Many previously unrecognized and unanticipated small RNAs have been identified, some with relative low GC contents (M-bM-^IM-$50%) and sequences that do not fold readily into base-paired secondary structures, contrary to the classical expectations for non-coding RNAs in a hyperthermophile. Conclusion: We have identified >2,700 TSS that include almost all of the primary sites of transcription initiation upstream of annotated genes, and also many secondary sites, sites within genes and sites resulting in antisense transcripts. The T.M-BM- kodakarensis genome is small (~2.1 Mbp) and tightly packed with protein-encoding genes, but the results reveal the presence of many non-coding RNAs and predict extensive RNA-based regulation in T. kodakarensis. cDNA libraries were generated and sequenced from RNA isolated from T.M-BM- kodakarensis cells growing exponentially (Sexp) and to stationary phase (Sstat) in ASW-YT medium with sulfur, growing exponentially in ASW-YT with pyruvate (Pexp), and from cells growing exponentially in pyruvate but 20 min after sulfur addition (PS). The cDNAs were generated after first incubating the RNA preparations with terminator exonuclease (TEX). TEX does not degrade primary transcripts with a 5'-triphosphate (Sharma et al., 2010) but does digest RNAs generated by transcript processing that have a 5'-monophosphate. As a control and to fully document all transcripts, a cDNA library (C) was also generated and sequenced from an aliquot of an RNA preparation isolated from the cells growing exponentially with sulfur that was not exposed to TEX digestion.

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Processing-Independent CRISPR RNAs Limit Natural Transformation in Neisseria meningitidis

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