I am pleased to announce one of my photographs is on the cover of the most recent issue of Cell. And not just for any old research story, either. This one involves the citrus mealybug Planococcus citri and a Russian doll progression of microbes that live inside other microbes inside the insect. It’s a real mind-bender about how evolution mixes and matches parts.
Summary: The smallest reported bacterial genome belongs to Tremblaya princeps, a symbiont of Planococcus citri mealybugs (PCIT). Tremblaya PCIT not only has a 139 kb genome, but possesses its own bacterial endosymbiont, Moranella endobia. Genome and transcriptome sequencing, including genome sequencing from a Tremblaya lineage lacking intracellular bacteria, reveals that the extreme genomic degeneracy of Tremblaya PCIT likely resulted from acquiring Moranella as an endosymbiont. In addition, at least 22 expressed horizontally transferred genes from multiple diverse bacteria to the mealybug genome likely complement missing symbiont genes. However, none of these horizontally transferred genes are from Tremblaya, showing that genome reduction in this symbiont has not been enabled by gene transfer to the host nucleus. Our results thus indicate that the functioning of this three-way symbiosis is dependent on genes from at least six lineages of organisms and reveal a path to intimate endosymbiosis distinct from that followed by organelles.
Here’s the paper: Husnik et al 2013. Horizontal Gene Transfer from Diverse Bacteria to an Insect Genome Enables a Tripartite Nested Mealybug Symbiosis. Cell – 20 June 2013 (Vol. 153, Issue 7, pp. 1567-1578). http://dx.doi.org/10.1016/j.cell.2013.05.040
Ed Yong provides a more digestable explanation: Snug as as Bug in a Bug in a Bug
More photographs from this series in my galleries: Planococcus citri at alexanderwild.com.
Incidentally, the photo was a commissioned piece just for the Cell cover. You didn’t know I take commissions? Well, now you do. If you’d like a nice photograph to help aim your research at your favorite journal, drop me a line.