Biology
June 2015
image sorces
Nature Reviews
7
a high proportion of guanine and cytosine – two of the four chemical bases of DNA. Scientists previously thought that the smaller a bacterial genome, the less guanine and cytosine its DNA would have. In further research of Hodgkinia, McCutcheon found a very fragmented genome with many separate variations throughout. Though this last discovery was set-aside for the time, it was just seen one year ago that that fragmented genome is a symbol of the mutation rate of the bacteria.
As the cicada gives food and shelter to the bacteria, the bacteria produces the essential acids necessary for life that cannot be found in a diet of tree sap.
In looking at another species of cicada located in South America, McCutcheon determined that the Hodgkinia had actually split into separate coexisting species over time. This caused the insect to have to rely on having double the amount of bacteria to produce only the same amount of amino acids from having only one species of Hodgkinia, an inefficient evolution. After this discovery McCutcheon returned to his initial specimen with the fragmented bacteria genome, and this was when he concluded that this fragmented Hodgkinia genome would actually lead to many different types of Hodgkinia over time, he was also able to make a conclusion on the correlation between the evolution of the Hodgkinia, and the length of life of the cicada.
Cicadas with long lives tend to have many different kinds of Hodgkinia mutations that had formed over time. However, these mutations tend to crowd out other symbionts from flourishing. This discovery of Hodgkinia mutation paves the way to further study into the occurrence of genetic difference from evolution that does not, paradoxically, help the organisms survive.
sources
Science Daily