New insight into chlamydia genetics
A Southampton team has made a breakthrough in Chlamydia genetics, overcoming a significant challenge in the field.
Chlamydia is the leading bacterial sexually transmitted infection, causing infertility, pelvic inflammatory disease, and chronic pain in women around the world. It is also the most prevalent cause of infectious blindness in developing countries. The best hope to prevent its ongoing spread is through vaccination.
However, research in understanding the bacterium’s biology has been hampered by its unusual developmental cycle: it only grows inside human cells, raising specific technical challenges that make it harder to study.
As a result, scientists have had difficulty in delivering DNA to the bacterial cells – a process that makes analysing gene function much easier.
In a new study, Southampton scientists have introduced a new technique to Chlamydia research, called Transposon Directed Insertion Site Sequencing (TraDIS). This will give researchers more insight into the genetics of Chlamydia.
The Southampton team, led by Dr Colette O’Neill from the Faculty of Medicine, adapted TraDIS for use in Chlamydia, developing new molecular techniques along the way to add to the Chlamydia genetic toolbox. This method allows small pieces of DNA to “jump” into the bacterium’s genome at a specific time point in the Chlamydia growth cycle, randomly mutating and therefore inactivating genes. Working with Dr Jade Forster in the Southampton WISH lab, Dr O’Neill then applied cutting edge sequencing technology to identify the genes that were mutated.
The study identified 36 unique mutated sites within the Chlamydia genome, and thus gained proof of principle of the methodology.
The findings of this study will allow further studies to take place to assess which genes are essential to survival under different growth conditions to enable a better understanding of gene function in Chlamydia.
Dr O’Neill explained: “For many years, scientists have struggled to use mass genetics approaches on Chlamydia due to its unique lifecycle and the specific growth conditions in which it needs to be studied. However, our work is the first mutagenesis approach that will enable us to mutate each and every gene in the chlamydial genome using a “jumping” gene called a transposon.
“This will hopefully give us more information on the genes of this important human pathogen, so we can identify which are essential for growth and therefore can become a target for vaccine development or new treatments.”
The study was funded by the Wellcome Trust and published in Wellcome Open Research.
The success of this project has led to a three-year biomedical resources grant from the Wellcome Trust to refine the technique and share the mutants through the internationally recognised Chlamydia Biobank (www.chlamydiabionbak.co.uk) established in Southampton.
The project was a multi-team effort between the Chlamydia Research Group (Prof Ian Clarke, Rachel Skilton, Dr Sarah Pearson), the Southampton WISH lab (Dr Jade Forster), the Southampton Biomedical Research Centre (Dr David Cleary), the Wellcome Trust Sanger Institute (Prof Nick Thomson), and Duquesne University (Prof David Lampe).
Main image: Confocal microscope image of immunofluorescently stained Chlamydia-infected eukaryotic cells. Green = chlamydia; blue = eukaryotic cell DNA; red = eukaryotic cell membrane. Credit: Rachel Skilton.