Evolution of Cell Shape DNA Replication Termination Pseudomonas Phage Hunt Lactococcal Phage Ecology Horizontal Gene Transfer

Research: Horizontal Gene Transfer and Chromosome Architecture

Bacteria have numerous short repeated DNA sequences within their genomes; some of these are artifacts of mutation during replication. Some of these artefactual sequences have been seized on by proteins and are now used during cell division to facilitate chromosome segregation. I developed techniques to identify these repeated sequences and dubbed them Architecture IMparting Sequences (AIMS). AIMS, patterned by mutation, are found in nearly every bacterial genome that has been sequenced to date and evidence of their utility continues to mount in the field of chromosome segregation.

The grand conclusion of that work (still in progress) was the idea that AIMS constrain horizontal gene transfer by negatively impacting DNA segregation when they are brought into chromosomes in non-permissive orientations. These disadvantageous HGT events would therefore be lost in a population, not because of the genes they contain but because the AIMS present would negatively effect DNA metabolism. This constraint on gene transfer would tend to permit organisms with similar AIMS to exchange DNA while more distantly related organisms would experience less gene exchange. Such constraints may be contributing to the observed cohesion in large families of bacteria instead of the panmictic genome blending that unconstrained transfer might be expected to generate. This project can ultimately be thought of as the first study of the effect of the genetic material itself on bacterial evolution.  

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Figure previously published in Hendrickson, H. (2012) The Lion and the Mouse: How Bacteriophages Create, Liberate and Decimate Pathogens.  In P. Hyman & S. Abedon (Eds.Bacteriophages in Health and Disease (pp - ). Oxford, UK: CABI.