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Complete DNA sequence and detailed analysis of the Yersinia pestis KIM5 plasmid encoding murine toxin and capsular
L E Lindler1, G V Plano, V Burland
1Department of Bacterial Diseases, Division of Communicable Diseases and Immunology, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100, USA. Dr._Luther_Lindler@wrsmtp-ccmail.army.mil
Abstract:
Yersinia pestis, the causative agent of plague, harbors at least three plasmids necessary for full virulence of the organism, two of which are species specific. One of the Y. pestis-specific plasmids, pMT1, is thought to promote deep tissue invasion, resulting in more acute onset of symptoms and death. We determined the entire nucleotide sequence of Y. pestis KIM5 pMT1 and identified potential open reading frames (ORFs) encoded by the 100,990-bp molecule. Based on codon usage for known yersinial genes, homology with known proteins in the databases, and potential ribosome binding sites, we determined that 115 of the potential ORFs which we considered could encode polypeptides in Y. pestis. Five of these ORFs were genes previously identified as being necessary for production of the classic virulence factors, murine toxin (MT), and the fraction 1 (F1) capsule antigen. The regions of pMT1 encoding MT and F1 were surrounded by remnants of multiple transposition events and bacteriophage, respectively, suggesting horizontal gene transfer of these virulence factors. We identified seven new potential virulence factors that might interact with the mammalian host or flea vector. Forty-three of the remaining 115 putative ORFs did not display any significant homology with proteins in the current databases. Furthermore, DNA sequence analysis allowed the determination of the putative replication and partitioning regions of pMT1. We identified a single 2,450-bp region within pMT1 that could function as the origin of replication, including a RepA-like protein similar to RepFIB, RepHI1B, and P1 and P7 replicons. Plasmid partitioning function was located ca. 36 kb from the putative origin of replication and was most similar to the parABS bacteriophage P1 and P7 system. Y. pestis pMT1 encoded potential genes with a high degree of similarity to a wide variety of organisms, plasmids, and bacteriophage. Accordingly, our analysis of the pMT1 DNA sequence emphasized the mosaic nature of this large bacterial virulence plasmid and provided implications as to its evolution.
Insights
The Yersinia pestis pMT1 plasmid sequence reveals a mosaic structure with 115 potential genes, including known virulence factors and novel candidates, offering insights into plague's evolution.
Area of Science:
- Microbiology
- Genomics
- Molecular Biology
Background:
- Yersinia pestis causes plague and harbors virulence plasmids.
- The pMT1 plasmid is crucial for Y. pestis virulence, potentially causing severe symptoms.
Purpose of the Study:
- To determine the complete nucleotide sequence of the Y. pestis KIM5 pMT1 plasmid.
- To identify and characterize open reading frames (ORFs) and potential virulence factors encoded by pMT1.
Main Methods:
- Whole genome sequencing of Y. pestis KIM5 pMT1.
- Bioinformatic analysis of identified ORFs, including homology searches and codon usage analysis.
- Identification of replication and partitioning regions.
Main Results:
- The 100,990-bp pMT1 plasmid sequence was determined, revealing 115 potential ORFs.
- Five ORFs corresponded to known virulence factors (murine toxin and F1 capsule).
- Seven novel potential virulence factors were identified, alongside replication and partitioning regions similar to bacteriophage systems.
Conclusions:
- The pMT1 plasmid exhibits a mosaic structure, suggesting horizontal gene transfer in its evolution.
- The identified genes and regulatory regions provide a foundation for understanding Y. pestis pathogenesis and its interaction with hosts and vectors.