Archaea are a separate group of microbes that resemble bacteria (see box). The research team, consisting of Joshua Hamm, Su Ding, Nicole Bale, Jaap Damsté and Anja Spang, conducts research into DPANN archaea, which have very small cells and relatively little genetic material. These DPANN archaea make up about half of all known archaea, and depend on other microbes for survival. They attach to their host and absorb lipids from the host as building blocks for their membrane, their own ‘coat’.
Picky eaters
Until now, it was thought that these parasitic archaea simply absorbed all the lipids from their host to make their membrane. But researchers Ding and Hamm have now shown for the first time that a specific parasitic archaeon, Candidatus Nanohaloarchaeum antarcticus, does not contain all the lipids of its host Halorubrum lacusprofundi contains, but only a selection of them. “In other words: Approx. N. antarcticus is a picky eater,” Hamm concludes.
Archaea, bacteria and higher organismsArchaea are single-celled organisms that were long thought to be a specific group of bacteria. Like bacteria, they do not have a nucleus with DNA or other organelles in their cells. However, since the 1970s, microbiologists no longer regard archaea as bacteria, but classify them as a separate domain within all life forms. So now we have archaea, bacteria and eukaryotes. The latter domain includes all animals and plants that have a nucleus with genetic material in their cells. |
Host responds to parasite
By analyzing what lipids the host contained in the presence and absence of their parasites, Ding and Hamm were also able to demonstrate that the host responds to the presence of the parasite. The host adapts its membrane: the type of lipids and their amounts change. Certain lipids themselves are also modified, so that their effect changes. The result is an increased metabolism of the host, and a more flexible membrane that is also more difficult for the parasite to penetrate. That change can have consequences for the host, Hamm explains. “If a microbe’s membrane changes, it can affect how well that microbe can cope with changes in its environment, for example in temperature or acidity.”
New technology is a game changer
The development of a new analytical technique by Su Ding turned out to be a game changer for this microbiological research. Until now, when analyzing lipids, scientists had to know exactly which group of lipids they were looking for in order to identify them in the analysis. Ding designed a new technique that allows researchers to look at all lipids at the same time – including unknown ones. “If we had used the classical approach, we probably would not have seen the change in lipids in the host. But with the new approach it was very clear.”
New insight
The microbiologists are very enthusiastic about these new findings. “It not only sheds new light on the interactions between different archaea; it provides a completely new insight into the fundamentals of microbial ecology,” says Hamm. “Especially that we have now shown that these parasitic microbes can modify the metabolism of other microbes, which can then cause that host microbe to respond differently to the environment In further research we need to examine the extent to which this affects the stability of microbial populations in a changing environment.”
Text: NIOZ
Photo: Joshua Hamm
