Читать книгу Algorithms in Bioinformatics - Paul A. Gagniuc - Страница 44

How much of the genome can be transferred to the nucleus or can be permanently lost in evolution? The complete loss of DNA in an organelle is a possibility. Among the organelles that have lost their genome in evolution is the hydrogenosome. Hydrogenosomes are cell organelles that have a double membrane and synthesize ATP via hydrogen-producing fermentations [117]. Hydrogenosomes were once mitochondria and are a classic example of complete mitochondrial genome loss [118]. Considering the hydrogenosome example, it is reasonable to assume that all eukaryotes may contain an organelle of mitochondrial ancestry [119]. However, DNA in the hydrogenosomes of some anaerobic ciliates has been detected [120]. Ciliates are protists with hair-like organelles (i.e. cilia) used for propulsion and adherence inside liquid media. Cases of genome-containing hydrogenosomes show that these organelles are somewhere toward the end of their reductive evolution period. It can also mean that the loss of the genome is not just a one-way street, which would have important implications for elucidating the occurrence of life on Earth. A basic question arises when considering the above: Are the genome-less hydrogenosomes organisms in their own way? This is an interesting question because it shows the versatility of life and the ideas discussed in the “Philosophical transactions” chapter or in the “Viruses vs. the spark of metabolism” subchapter.