Scattering of the rRNA genes on the physical map of the circular chromosome of Leptospira interrogans serovar icterohaemorrhagiae

Abstract

Leptospira interrogans is a pathogenic bacterium with a low G+C content (34 to 39%). The restriction enzymes NotI, AscI, and SrfI cut the chromosome of L. interrogans serovar icterohaemorrhagiae into 13, 3, and 5 fragments separable by one- and two-dimensional pulsed-field gel electrophoresis (PFGE). The genome is composed of a circular 4.6-Mbp chromosome and a 0.35-Mbp extrachromosomal element. A physical map of the chromosome was constructed for NotI, AscI, and SrfI by using single and double digests, or partial NotI digests obtained at random or by cross-protection of NotI sites by FnuDII methylase, and linking clones. rRNA genes were found to be widely scattered on the chromosome.

IS1500, an IS3-like element from Leptospira interrogans

“…DNA electrophoresis and hybridization. Genomic DNA was prepared and separated by either continuous-field gel electrophoresis (CFGE) or PFGE using the protocols described previously by Baril et al (1992), Zuerner (1991) and Zuerner e t al. (1993b).…”

“…During earlier physical genomic mapping studies of L. interrogans (serovar icterobaemorrbagiae strain Verdun and serovar pomona strain RZ11) several cloned sequences were independently isolated and found to hybridize with multiple restriction fragments (Baril et al, 1992 ;Zuerner, 1993 ;Zuerner e t al., 1993b). Cross-hybridization analysis showed that several different clones shared common sequences, suggesting that they were part of a related group of repetitive elements.…”

“…Pulsed-field gel electrophoresis (PFGE) studies of L. interrogans $emu lato reveals extensive heterogeneity (Herrmann e t al., 1991(Herrmann e t al., , 1992 suggesting that this is a common phenomenon throughout this genus. During construction of physical and genetic maps of L. interrogans serovars icterohaemorrhagiae strain Verdun (Baril et al, 1992) and pomona strain R Z l l (Zuerner, 1991) several additional repetitive sequence elements were isolated, including an element related to the IS3 family of insertion elements. In this study we characterize copies of an IS3-like element from L. interrogans, and report its distribution in the genus Leptospira.…”

Physical and genetic map of the Serpulina hyodysenteriae B78T chromosome

“…Evidence suggesting that Leptospira interrogans has two circular chromosomal replicons has recently been presented (40). Spirochete genomes range in size from 1 Mb in Treponema pallidum (28,36) to 4.75 to 5 Mb in L. interrogans (1,38).…”

“…Genetic maps have been constructed for only two spirochetes, Borrelia burgdorferii (4,7,25) and L. interrogans (1,40). The limited comparison that is possible between these two genetic maps indicates that the genetic organizations of these two spirochetes are different.…”