|Colonies of the transformed Mycoplasma mycoides bacterium. Click to enlarge.|
Researchers at the J. Craig Venter Institute (JCVI) have successfully transplanted the genome from one species of bacterium into another.
The work, published online in the journal Science, by JCVI’s Carole Lartigue and colleagues, outlines the methods and techniques used to change one bacterial species, Mycoplasma capricolum, into another, Mycoplasma mycoides large colony (LC), by replacing the genome of the former with that of the latter.
The successful completion of this research is important because it is one of the key proof of principles in synthetic genomics that will allow us to realize the ultimate goal of creating a synthetic organism. We are committed to this research as we believe that synthetic genomics holds great promise in helping to solve issues like climate change and in developing new sources of energy.—J. Craig Venter, Ph.D., president and chairman, JCVI
Genome transplantation is an essential enabling step in the field of synthetic biology as it is a key mechanism by which chemically synthesized chromosomes can be activated into viable living cells. The ability to transfer the naked DNA isolated from one species into a second microbial species paves the way for next experiments to transplant a fully synthetic bacterial chromosome into a living organism and if successful, “boot up” the new entity, according to JCVI scientists.
The JCVI team devised several key steps to enable the genome transplantation. First, an antibiotic selectable marker gene was added to the M. mycoides LC chromosome to allow for selection of living cells containing the transplanted chromosome.
Then the team purified the DNA or chromosome from M. mycoides LC so that it was free from proteins (“naked DNA”). This M. mycoides LC chromosome was then transplanted into the M. capricolum cells. After several rounds of cell division, the recipient M. capricolum chromosome disappeared having been replaced by the donor M. mycoides LC chromosome, and the M. capricolum cells took on all the phenotypic characteristics of M. mycoides LC cells.
As a test of the success of the genome transplantation, the team used two methods—2D gel electrophoresis and protein sequencing—to prove that all the expressed proteins were now the ones coded for by the M. mycoides LC chromosome.
Two sets of antibodies that bound specifically to cell surface proteins from each cell were reacted with transplant cells, to demonstrate that the membrane proteins switch to those dictated by the transplanted chromosome not the recipient cell chromosome. The new, transformed organisms show up as bright blue colonies in images of blots probed with M. mycoides LC specific antibody.
The group chose to work with these species of mycoplasmas for several reasons: the small genomes of these organisms which make them easier to work with, their lack of cell walls, and the team’s experience and expertise with mycoplasmas. The mycoplasmas used in the transplantation experiment are also relatively fast growing, allowing the team to ascertain success of the transplantation sooner than with other species of mycoplasmas.
While we are excited by the results of our research, we are continuing to perfect and refine our techniques and methods as we move to the next phases and prepare to develop a fully synthetic chromosome.—Dr. Carole Lartigue
This research was funded by Synthetic Genomics Inc. Synthetic Genomics, which was founded by Venter, recently entered a research and development partnership with BP focused first on gaining a better understanding of the natural microbial communities in various hydrocarbon formations such as oil, natural gas, coal and shale. The next step in the partnership is then to develop organisms optimized for the enhancement or increased production of subsurface hydrocarbons. (Earlier post.)
Venter is also one of the signatories of the Ilulissat Statement, which calls for an international effort to advance synthetic biology that would not only propel research, but do so while developing protective measures against accidents and abuses of synthetic biology. (Earlier post.)
Carole Lartigue, John I. Glass, Nina Alperovich, Rembert Pieper, Prashanth P. Parmar, Clyde A. Hutchison III, Hamilton O. Smith, J. Craig Venter; “Genome Transplantation in Bacteria: Changing One Species to Another”; Science DOI: 10.1126/science.1144622