Friday Science Review: June 3, 2011
June 3, 2011
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Horizontal Gene Transfer: Bacterial Adaptation
McGill University ♦ Fudan University, China ♦ Published in PLoS ONE, May 20, 2011
The bacterium S. aureus can cause a host of problems in humans, companion animals, and cattle. Its ability to adapt and circumvent the effects of antibiotics allow it to persist, while virulence factors, acquired via horizontal gene transfer (HGT) with surrounding microflora, give S. aureus the capacity to cause disease relatively easily. The mobile genetic elements that allow for HGT to occur can come in different fashions, including viruses, plasmids, and other elements that may be self-transmissible or piggy-back with mobile viruses and plasmids. By comparing the genetic content of different strains of S. aureus researchers were able to evaluate sequence diversities from different sources to measure the extent that HGT contributes to genetic diversity. Comparative genomic analyses of strains derived from cows, sheep, chickens, and humans revealed that they are all highly associated with one another. Although the Serine-Aspartate Repeat (Sdr) family proteins in S. aureus are of unknown function, they have previously been correlated with human disease. Researchers were able to type S. aureus with regional differences in sdr gene distribution and make associations between specific distributions and clinical samples. At least one new insertion sequence observed was responsible for the HGT that allowed the sdrC gene to migrate between strains.
Eggs from Skin
University of Guelph ♦ University of Western Ontario ♦ Queen’s University
Published in PLoS ONE, May 19, 2011
A group that previously isolated stem cells from fetal pig skin has isolated multipotent stem cells from mouse skin and shown that they can differentiate into oocyte-like cells in vitro and in vivo. Researchers used a flourescent marker linked to the gene OCT-4 under the control of a germ cell-specific DNA enhancer element to see if germ cells would arise from mouse stem cells upon differentiation in culture. After cells were allowed to differentiate, a small fraction were GFP+, indicating that germ cells were indeed forming. Germ cells were greatly enlarged reaching diameters of up to 45 microns and expressed oocyte-specific markers. In terms of their visual appearance the similarity was striking; both natural oocytes and oocytes derived from stem cells were identical in size and exhibited zona pellucida-like structures. The in vivo germ cell potential of skin-derived stem cells was assessed by mixing them with newborn ovarian cells and transplanting them into the mouse. Dissection revealed that GFP+ cells also appeared in vivo. This study establishes a new model for studying oogenesis and germ cell formation in vitro.