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Chromosomal rearrangements formed by rrn recombination do not improve replichore balance in host-specific Salmonella enterica serovars.

Matthews TD, Edwards R, Maloy S - PLoS ONE (2010)

Bottom Line: Only 48 out of 1,440 possible arrangement types were identified in 212 host-specific strains.While the replichores of most naturally-occurring arrangement types were well-balanced, most theoretical arrangement types had imbalanced replichores.Furthermore, the most common types of rearrangements did not change replichore balance.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America.

ABSTRACT

Background: Most of the ∼2,600 serovars of Salmonella enterica have a broad host range as well as a conserved gene order. In contrast, some Salmonella serovars are host-specific and frequently exhibit large chromosomal rearrangements from recombination between rrn operons. One hypothesis explaining these rearrangements suggests that replichore imbalance introduced from horizontal transfer of pathogenicity islands and prophages drives chromosomal rearrangements in an attempt to improve balance.

Methodology/principal findings: This hypothesis was directly tested by comparing the naturally-occurring chromosomal arrangement types to the theoretically possible arrangement types, and estimating their replichore balance using a calculator. In addition to previously characterized strains belonging to host-specific serovars, the arrangement types of 22 serovar Gallinarum strains was also determined. Only 48 out of 1,440 possible arrangement types were identified in 212 host-specific strains. While the replichores of most naturally-occurring arrangement types were well-balanced, most theoretical arrangement types had imbalanced replichores. Furthermore, the most common types of rearrangements did not change replichore balance.

Conclusions/significance: The results did not support the hypothesis that replichore imbalance causes these rearrangements, and suggest that the rearrangements could be explained by aspects of a host-specific lifestyle.

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Related in: MedlinePlus

Estimated vs. physical replichore balance.While the calculator slightly underestimated replichore balance (dashed line  =  perfect fit), the estimates of replichore balance were statistically the same as the physically mapped arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).
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pone-0013503-g004: Estimated vs. physical replichore balance.While the calculator slightly underestimated replichore balance (dashed line  =  perfect fit), the estimates of replichore balance were statistically the same as the physically mapped arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).

Mentions: To validate the calculator, balance estimates were generated using the average region sizes of the sequenced Typhi strains CT18 and Ty2 [33], [53] and compared to the balance calculated from the physical mapping of 29 Typhi strains with unique arrangement types [27] (Figure 4). Replichore imbalance in these arrangement types varied from 1–55°. While the calculator slightly underestimated the physical balance, mostly due to strain-specific increases in region size from insertions, the balance estimates from the calculator statistically agree with the physical balance of these arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).


Chromosomal rearrangements formed by rrn recombination do not improve replichore balance in host-specific Salmonella enterica serovars.

Matthews TD, Edwards R, Maloy S - PLoS ONE (2010)

Estimated vs. physical replichore balance.While the calculator slightly underestimated replichore balance (dashed line  =  perfect fit), the estimates of replichore balance were statistically the same as the physically mapped arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2957434&req=5

pone-0013503-g004: Estimated vs. physical replichore balance.While the calculator slightly underestimated replichore balance (dashed line  =  perfect fit), the estimates of replichore balance were statistically the same as the physically mapped arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).
Mentions: To validate the calculator, balance estimates were generated using the average region sizes of the sequenced Typhi strains CT18 and Ty2 [33], [53] and compared to the balance calculated from the physical mapping of 29 Typhi strains with unique arrangement types [27] (Figure 4). Replichore imbalance in these arrangement types varied from 1–55°. While the calculator slightly underestimated the physical balance, mostly due to strain-specific increases in region size from insertions, the balance estimates from the calculator statistically agree with the physical balance of these arrangement types (P<0.01, paired Student's t test; Pearson's correlation  = 0.982).

Bottom Line: Only 48 out of 1,440 possible arrangement types were identified in 212 host-specific strains.While the replichores of most naturally-occurring arrangement types were well-balanced, most theoretical arrangement types had imbalanced replichores.Furthermore, the most common types of rearrangements did not change replichore balance.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America.

ABSTRACT

Background: Most of the ∼2,600 serovars of Salmonella enterica have a broad host range as well as a conserved gene order. In contrast, some Salmonella serovars are host-specific and frequently exhibit large chromosomal rearrangements from recombination between rrn operons. One hypothesis explaining these rearrangements suggests that replichore imbalance introduced from horizontal transfer of pathogenicity islands and prophages drives chromosomal rearrangements in an attempt to improve balance.

Methodology/principal findings: This hypothesis was directly tested by comparing the naturally-occurring chromosomal arrangement types to the theoretically possible arrangement types, and estimating their replichore balance using a calculator. In addition to previously characterized strains belonging to host-specific serovars, the arrangement types of 22 serovar Gallinarum strains was also determined. Only 48 out of 1,440 possible arrangement types were identified in 212 host-specific strains. While the replichores of most naturally-occurring arrangement types were well-balanced, most theoretical arrangement types had imbalanced replichores. Furthermore, the most common types of rearrangements did not change replichore balance.

Conclusions/significance: The results did not support the hypothesis that replichore imbalance causes these rearrangements, and suggest that the rearrangements could be explained by aspects of a host-specific lifestyle.

Show MeSH
Related in: MedlinePlus