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Virulence and arsenic resistance in Yersiniae.

ABSTRACT: The genus Yersinia contains three pathogenic species: Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica. Only a few biotypes and serotypes of Y. enterocolitica are pathogenic, and these form two distinct groups: some are of low virulence, and they are encountered worldwide; others, mainly encountered in North America, are markedly more virulent. All pathogenic yersiniae possess a 70-kb virulence plasmid called pYV which encodes secreted antihost proteins called Yops as well as a type III secretion machinery that is required for Yop secretion. Genes encoding Yop synthesis and secretion are tightly clustered in three quadrants of the pYV plasmid. We show here that in the low-virulence strains of Y. enterocolitica, the fourth quadrant of the plasmid contains a new class II transposon, Tn2502. This transposon encodes a defective transposase, but transposition can be complemented in trans by Tn2501, another class II transposon. Tn2502 was not detected in the pYV plasmids of the more virulent American strains of Y. enterocolitica, of Y. pseudotuberculosis, and of Y. pestis. Tn2502 confers arsenite and arsenate resistance. This resistance involves four genes; three are homologous to the arsRBC genes present on the Escherichia coli chromosome, but no homolog of the fourth one, arsH, has been found. The systematic presence of such a resistance operon on a virulence plasmid is unusual and could be related to the recent spread of low-virulence Y. enterocolitica strains. The presence of this ars operon also constitutes the first significant difference between the pYV plasmids from different Yersinia species.

SUBMITTER: Neyt C

PROVIDER: S-EPMC178738 | biostudies-other | 1997 Feb

REPOSITORIES: biostudies-other

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Virulence and arsenic resistance in Yersiniae.

Neyt C C Iriarte M M Thi V H VH Cornelis G R GR

Journal of bacteriology 19970201 3

The genus Yersinia contains three pathogenic species: Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica. Only a few biotypes and serotypes of Y. enterocolitica are pathogenic, and these form two distinct groups: some are of low virulence, and they are encountered worldwide; others, mainly encountered in North America, are markedly more virulent. All pathogenic yersiniae possess a 70-kb virulence plasmid called pYV which encodes secreted antihost proteins called Yops as well as a type ...[more]

PMID: 9006011

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Project description:BackgroundArsenic is known as a toxic metalloid, which primarily exists in inorganic form [As(III) and As(V)] and can be transformed by microbial redox processes in the natural environment. As(III) is much more toxic and mobile than As(V), hence microbial arsenic redox transformation has a major impact on arsenic toxicity and mobility which can greatly influence the human health. Our main purpose was to investigate the distribution and diversity of microbial arsenite-resistant species in three different arsenic-contaminated soils, and further study the As(III) resistance levels and related functional genes of these species.ResultsA total of 58 arsenite-resistant bacteria were identified from soils with three different arsenic-contaminated levels. Highly arsenite-resistant bacteria (MIC > 20 mM) were only isolated from the highly arsenic-contaminated site and belonged to Acinetobacter, Agrobacterium, Arthrobacter, Comamonas, Rhodococcus, Stenotrophomonas and Pseudomonas. Five arsenite-oxidizing bacteria that belonged to Achromobacter, Agrobacterium and Pseudomonas were identified and displayed a higher average arsenite resistance level than the non-arsenite oxidizers. 5 aoxB genes encoding arsenite oxidase and 51 arsenite transporter genes [18 arsB, 12 ACR3(1) and 21 ACR3(2)] were successfully amplified from these strains using PCR with degenerate primers. The aoxB genes were specific for the arsenite-oxidizing bacteria. Strains containing both an arsenite oxidase gene (aoxB) and an arsenite transporter gene (ACR3 or arsB) displayed a higher average arsenite resistance level than those possessing an arsenite transporter gene only. Horizontal transfer of ACR3(2) and arsB appeared to have occurred in strains that were primarily isolated from the highly arsenic-contaminated soil.ConclusionSoils with long-term arsenic contamination may result in the evolution of highly diverse arsenite-resistant bacteria and such diversity was probably caused in part by horizontal gene transfer events. Bacteria capable of both arsenite oxidation and arsenite efflux mechanisms had an elevated arsenite resistance level.

Project description:In the foodborne pathogen Listeria monocytogenes, arsenic resistance is encountered primarily in serotype 4b clones considered to have enhanced virulence and is associated with an arsenic resistance gene cluster within a 35-kb chromosomal region, Listeria genomic island 2 (LGI2). LGI2 was first identified in strain Scott A and includes genes putatively involved in arsenic and cadmium resistance, DNA integration, conjugation, and pathogenicity. However, the genomic localization and sequence content of LGI2 remain poorly characterized. Here we investigated 85 arsenic-resistant L. monocytogenes strains, mostly of serotype 4b. All but one of the 70 serotype 4b strains belonged to clonal complex 1 (CC1), CC2, and CC4, three major clones associated with enhanced virulence. PCR analysis suggested that 53 strains (62.4%) harbored an island highly similar to LGI2 of Scott A, frequently (42/53) in the same location as Scott A (LMOf2365_2257 homolog). Random-primed PCR and whole-genome sequencing revealed seven novel insertion sites, mostly internal to chromosomal coding sequences, among strains harboring LGI2 outside the LMOf2365_2257 homolog. Interestingly, many CC1 strains harbored a noticeably diversified LGI2 (LGI2-1) in a unique location (LMOf2365_0902 homolog) and with a novel additional gene. With few exceptions, the tested LGI2 genes were not detected in arsenic-resistant strains of serogroup 1/2, which instead often harbored a Tn554-associated arsenic resistance determinant not encountered in serotype 4b. These findings indicate that in L. monocytogenes, LGI2 has a propensity for certain serotype 4b clones, exhibits content diversity, and is highly promiscuous, suggesting an ability to mobilize various accessory genes into diverse chromosomal loci.IMPORTANCEListeria monocytogenes is widely distributed in the environment and causes listeriosis, a foodborne disease with high mortality and morbidity. Arsenic and other heavy metals can powerfully shape the populations of human pathogens with pronounced environmental lifestyles such as L. monocytogenes Arsenic resistance is encountered primarily in certain serotype 4b clones considered to have enhanced virulence and is associated with a large chromosomal island, Listeria genomic island 2 (LGI2). LGI2 also harbors a cadmium resistance cassette and genes putatively involved in DNA integration, conjugation, and pathogenicity. Our findings indicate that LGI2 exhibits pronounced content plasticity and is capable of transferring various accessory genes into diverse chromosomal locations. LGI2 may serve as a paradigm on how exposure to a potent environmental toxicant such as arsenic may have dynamically selected for arsenic-resistant subpopulations in certain clones of L. monocytogenes which also contribute significantly to disease.

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Virulence and arsenic resistance in Yersiniae.

Publications

Virulence and arsenic resistance in Yersiniae.

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