Plasmids help antibiotic resistance to travel between bacteria
12 April 2011
The part of bacterial DNA that often carries antibiotic
resistance can move between different types of bacteria and adapt to
widely differing bacterial species, shows a study by the University of
Gothenburg and Chalmers University of Technology.
The results are published in the journal Nature Communications
More bacteria are becoming resistant to common antibiotics, and
more are becoming resistant to all known antibiotics. The problem is
known as multi-resistance, and is generally described as one of the
most significant future threats to public health. Antibiotic
resistance can arise in bacteria in our environment and in our
bodies. Antibiotic resistance can then be transferred to the
bacteria that cause human diseases, even if the bacteria are not
related to each other.
A large proportion of gene transfer between bacteria takes place
with the aid of what are known as conjugative plasmids, a part of
the bacterial DNA. A plasmid can only exist and multiply inside a
cell, where it uses the cell’s machinery, but can then be
transferred to another cell and in that way spread between bacteria.
The research team studied a group of the known carriers of
antibiotic resistance genes: IncP-1 plasmids. Using advanced DNA
analysis, the researchers have succeeded in mapping the origin of
different IncP-1 plasmids and their mobility between different
“Our results show that plasmids from the IncP-1 group have
existed in, and adapted to, widely differing bacteria. They have
also recombined, which means that a single plasmid can be regarded
as a composite jigsaw puzzle of genes, each of which has adapted to
different bacterial species”, says Peter Norberg, a researcher in
the Institute of Biomedicine at the University of Gothenburg. This
indicates very good adaptability and suggests that these plasmids
can move relatively freely between, and thrive in, widely differing
“IncP-1 plasmids are very potent ‘vehicles’ for transporting
antibiotic resistance genes between bacterial species. Therefore, it
does not matter much in what environment, in what part of the world,
or in what bacterial species antibiotic resistance arises.
Resistance genes could relatively easily be transported from the
original environment to bacteria that infect humans, through IncP-1
plasmids, or other plasmids with similar properties, as ‘vehicles’,”
says Professor Malte Hermansson of the Department of Cell and
Molecular Biology at the University of Gothenburg.
It has been known for some time that plasmids are important in
the spread of antibiotic resistance. The research team’s findings
show that IncP-1 plasmids can move, and have moved, between widely
differing bacterial species and in addition have interacted directly
with one another, which can increase the potential for gene
The study The IncP-1 Plasmid Backbone Adapts to Different Host
Bacterial Species and Evolves Through Homologous Recombination.
Peter Norberg, Maria Bergström and Malte Hermansson at the
University of Gothenburg, in cooperation with Vinay Jethava and
Devdatt Dubhashi at the Chalmers University of Technology.
1. Peter Norberg, Maria Bergström, Vinay Jethava, Devdatt
Dubhashi, Malte Hermansson. The IncP-1 plasmid backbone adapts
to different host bacterial species and evolves through homologous
recombination. Nature Communications, Volume: 2, Article
number: 268. DOI: