# Extensive Phenotypic Changes Associated with Large-scale Horizontal Gene Transfer

## TL;DR

Large-scale horizontal gene transfer in bacteria causes extensive phenotypic changes, affecting stress sensitivity and behavior.

## Contribution

The study reveals how large gene transfers impact cellular networks and evolutionary trajectories in real time.

## Key findings

- A 1Mb megaplasmid transfer in Pseudomonas stutzeri caused sensitization to various stresses.
- The transfer altered bacterial behavior and shifted pleiotropic relationships in the genome.
- The system offers a foundation to study evolutionary consequences of gene integration.

## Abstract

Horizontal gene transfer often leads to phenotypic changes within recipient organisms independent of any immediate evolutionary benefits. While secondary phenotypic effects of horizontal transfer (i.e. changes in growth rates) have been demonstrated and studied across a variety of systems using relatively small plasmid and phage, little is known about how size of the acquired region affects the magnitude or number of such costs. Here we describe an amazing breadth of phenotypic changes which occur after a large-scale horizontal transfer event (~1Mb megaplasmid) within Pseudomonas stutzeri including sensitization to various stresses as well as changes in bacterial behavior. These results highlight the power of horizontal transfer to shift pleiotropic relationships and cellular networks within bacterial genomes. They also provide an important context for how secondary effects of transfer can bias evolutionary trajectories and interactions between species. Lastly, these results and system provide a foundation to investigate evolutionary consequences in real time as newly acquired regions are ameliorated and integrated into new genomic contexts.