# SHARK: A Specialized Host for Assembling R6K Plasmids

## TL;DR

SHARK is a new type of E. coli strain designed to make it easier and more efficient to work with R6K plasmids for genome engineering.

## Contribution

The SHARK strains are engineered for efficient R6K plasmid maintenance and cloning, surpassing commercial alternatives.

## Key findings

- SHARK strains are over 100 times more efficient than commercial Pir strains for transforming large and complex cloning reactions.
- SHARK strains are built from the DH10B derivative and include a genome-encoded pir gene for stable R6K plasmid maintenance.
- All SHARK strains and genetic tools are publicly available to support genome engineering projects.

## Abstract

R6K plasmids are
commonly used for a wide range of genome engineering
applications due to their ability to support transient delivery of
genetic cargos in many hosts. The maintenance of R6K plasmids requires
specific strains. Unfortunately, many of these have obscure backgrounds,
limited availability and were not built for efficient cloning. To
address this issue, we present the construction and characterization
of a series of Pir E. coli strains
called SHARK that are built from the DH10B derivative, Marionette-Clo.
All SHARK strains have a genome encoded pir gene
for stable R6K plasmid maintenance and a λCI gene for tight unconditional repression of specific genes on plasmids.
We show that SHARK strains are >100-fold more efficient than a
commercial
Pir strain when transformed with large and complex cloning reactions.
SHARK is intended to help facilitate the cloning of R6K plasmids for
challenging genome engineering projects, with all strains and genetic
tools for their assembly being made publicly available.