Chromosomal Location Determines the Rate of Intrachromosomal Homologous Recombination in Salmonella. 2021

Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
Department of Medical Biochemistry and Microbiology, Biomedical Center, Uppsala University, Uppsala, Sweden.

Homologous recombination is an important mechanism directly involved in the repair, organization, and evolution of prokaryotic and eukaryotic chromosomes. We developed a system, based on two genetic cassettes, that allows the measurement of recombinational repair rates between different locations on the chromosome. Using this system, we analyzed 81 different positional combinations throughout the chromosome to answer the question of how the position and orientation of sequences affect intrachromosomal homologous recombination. Our results show that recombination was possible between any two locations tested in this study and that recombinational repair rates varied by just above an order of magnitude. The observed differences in rate do not correlate with distance between the recombination cassettes or with distance from the origin of replication but could be explained if each location contributes individually to the recombination event. The relative levels of accessibility for recombination vary 5-fold between the various cassette locations, and we found that the nucleoid structure of the chromosome may be the major factor influencing the recombinational accessibility of each chromosomal site. Furthermore, we found that the orientation of the recombination cassettes had a significant impact on recombination. Recombinational repair rates for the cassettes inserted as direct repeats are, on average, 2.2-fold higher than those for the same sets inserted as inverted repeats. These results suggest that the bacterial chromosome is not homogenous with regard to homologous recombination, with regions that are more or less accessible, and that the orientation of genes affects recombination rates. IMPORTANCE Bacterial chromosomes frequently carry multiple copies of genes at separate chromosomal locations. In Salmonella, these include the 7 rrn operons and the duplicate tuf genes. Genes within these families coevolve by homologous recombination, but it is not obvious whether their rates of recombination reflect general rates of intrachromosomal recombination or are an evolved property particularly associated with these conserved genes and locations. Using a novel experimental system, we show that recombination is possible between all tested pairs of locations at rates that vary by just above 1 order of magnitude. Differences in rate do not correlate with distance between the sites or distance to the origin of replication but may be explained if each location contributes individually to the recombination event. Our results suggest the existence of bacterial chromosomal domains that are differentially available for recombination and that gene orientation affects recombination rates.

UI MeSH Term Description Entries
D002876 Chromosomes, Bacterial Structures within the nucleus of bacterial cells consisting of or containing DNA, which carry genetic information essential to the cell. Bacterial Chromosome,Bacterial Chromosomes,Chromosome, Bacterial
D004260 DNA Repair The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones. DNA Damage Response
D012475 Salmonella A genus of gram-negative, facultatively anaerobic, rod-shaped bacteria that utilizes citrate as a sole carbon source. It is pathogenic for humans, causing enteric fevers, gastroenteritis, and bacteremia. Food poisoning is the most common clinical manifestation. Organisms within this genus are separated on the basis of antigenic characteristics, sugar fermentation patterns, and bacteriophage susceptibility.
D059765 Homologous Recombination An exchange of DNA between matching or similar sequences. Homologous Recombinations,Recombination, Homologous,Recombinations, Homologous

Related Publications

Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
January 2004, Methods in molecular biology (Clifton, N.J.),
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
January 1994, The EMBO journal,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
February 2019, Bio-protocol,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
December 1992, Molecular and cellular biology,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
July 1997, Genetics,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
October 1996, Carcinogenesis,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
May 1995, Plant molecular biology,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
January 1994, Tsitologiia,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
June 1999, Genetics,
Eva Garmendia, and Gerrit Brandis, and Lionel Guy, and Sha Cao, and Diarmaid Hughes
February 2000, Molecular & general genetics : MGG,
Copied contents to your clipboard!