The progressing AIDS epidemic has prompted a revival of interest in pneumocytosis, a respiratory infection which appears only in immunodepressed humans and can be fatal if treatment is not given. The agent responsible is a microscopic fungus, albeit usually non-pathogenic, which lives in the pulmonary alveoli. Searching for possible sources of human contamination in animal reservoirs proved negative: only the species specific for humans, Pneumocystis jirovecii, can trigger pneumonia in humans. This work has at the same time revealed the existence of numerous other species of pneumocysts in Mammals: primates, domestic animals, rodents, marsupials, and so on. Attempts at cross-infestation between hosts of different species have confirmed the high degree of pneumocyst host-specificity: each animal species harbours a different pneumocyst. Preliminary investigations on hereditary relationships between pneumocysts, using molecular data (from mitochondrial or nuclear DNA sequence comparison), suggested that this specificity would result from a process of strict co-evolution between host and parasite.
Reconstitution of the evolutionary relationship between pneumocysts and consequent verification of this hypothesis was conducted by the IRD researchers. Working with other institutes (1), they compared the sequences of three genes from samples taken from the respiratory passages or lung tissue of about 20 Primate species. The relationships between the micro-organisms were then compared with those of their hosts (2). The phylogenetic trees obtained appeared very similar, the pneumocyst phylogeny following mirror-like that of the Primates. The few differences observed appeared at the branching-off of pneumocysts of three South-American monkeys: the saki (Pithecia pithecia), the squirrel monkey (Saimiri sciureus) and the owl monkey (Aotus nancymai). Previous work on the phylogeny of these monkeys shows a comparable uncertainty concerning the evolutionary relationship of these three species. Thus, the pneumocyst phylogeny is similar to that of its hosts, even when it is uncertain.
The finding of a co-phylogeny situation confirms the hypothesis of a strict co-evolution between the host and its parasite over geologic time. Pneumocystosis is probably not therefore linked to the emergence of a new pathological agent. It is caused by a symbiotic opportunist micro-organism, which only becomes pathological when the host’s immune defences decline. Beyond its interest for understanding the epidemiology of a severe parasitic disease linked to the development of AIDS, this investigation suggests that the pneumocysts, which are genetically independent organisms, may provide taxonomists with a series of new markers for elucidating phylogenetic relationships between Mammals. The value of these markers is increased by the fact that they have not been subjected to pressures from the external environment, seeing that the pneumocysts live as symbionts in their hosts’ lungs.
Marie Guillaume | alfa
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy