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Research

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GLOBAL WARMING DAMAGES SYMBIOTIC ORGANISMS

http://www.asm.org/index.php/mbiosphere/item/468-global-warming-damages-symbiotic-organisms

The collaborative work is described in a recent study published online in the journal mBio, a journal of the American Society for Microbiology. Experiments showed that when heat-susceptible bacteria living symbiotically in the guts of insects are exposed to increased temperatures, both the bacteria and the insect are negatively impacted. The research illustrates another way global warming will wreak havoc on life as we know it, setting off deleterious chain reactions among organisms living in symbiosis.

Specifically, the investigators demonstrated that when the southern green stinkbug was reared inside an incubator, in which temperature was controlled at 2.5 °C higher than outside, there was a significant reduction in the symbiont bacteria that sparked severe fitness defects in the insect (ie. retarded growth, reduced size). At higher temperatures, no nymphs were able to reach the adult stage. Global warming is predicted to raise the average temperature by 2.5 °C by 2100.

“Considering that many microbial symbionts are vulnerable to high temperature stress, such symbionts can be the Achilles’ heel of symbiont-dependent organisms in this warming world,” said Dr. Fukatsu. He said that people should keep in mind that global warming might impact diverse organisms, not necessarily directly, but possibly indirectly via affecting unseen microbial associates. “Coral breaching, in which symbiotic photosynthetic algae of corals are killed by high temperature and coral reefs are severely damaged, is regarded as a serious environmental issue, but plausibly, similar phenomena may be ubiquitously found in the ecosystem,” said Dr. Fukatsu.

Collapse of Insect Gut Symbiosis under Simulated Climate Change

Global warming impacts diverse organisms not only directly but also indirectly via other organisms with which they interact. Recently, the possibility that elevated temperatures resulting from global warming may substantially affect biodiversity through disrupting mutualistic/parasitic associations has been highlighted. Here we report an experimental demonstration that global warming can affect a pest insect via suppression of its obligate bacterial symbiont. The southern green stinkbug Nezara viridula depends on a specific gut bacterium for its normal growth and survival. When the insects were reared inside or outside a simulated warming incubator wherein temperature was controlled at 2.5°C higher than outside, the insects reared in the incubator exhibited severe fitness defects (i.e., retarded growth, reduced size, yellowish body color, etc.) and significant reduction of symbiont population, particularly in the midsummer season, whereas the insects reared outside did not. Rearing at 30°C or 32.5°C resulted in similar defective phenotypes of the insects, whereas no adult insects emerged at 35°C. Notably, experimental symbiont suppression by an antibiotic treatment also induced similar defective phenotypes of the insects, indicating that the host’s defective phenotypes are attributable not to the heat stress itself but to the suppression of the symbiont population induced by elevated temperature. These results strongly suggest that high temperature in the midsummer season negatively affects the insects not directly but indirectly via the heat-vulnerable obligate bacterial symbiont, which highlights the practical relevance of mutualism collapse in this warming world.

Study demonstrates role of gut bacteria in neurodegenerative diseases

http://louisville.edu/medicine/news/study-demonstrates-role-of-gut-bacteria-in-neurodegenerative-diseases