Primary symbionts

In another gutless marine worm, the oligochaete Olavius al-garvensis, three partners participate in an unusual mutualism. The worm harbors two different primary symbionts in immediate proximity below its cuticle between extensions of epidermal cells. By performing comparative 16S rRNA sequencing and... 

Tetratrophic interactions between a host plant, a phytophagous pest (primary host), a hymenopteran parasitoid or symbiont (secondary host) and a hymenopteran hyperparasitoid (which parasitizes the secondary host) are of considerable importance, because hyperparasitism can significantly reduce populations of economically beneficial parasitoids [11]. Hyperparasitoids use host-marking (=spacing) pheromones, sex pheromones [12], and host-detection cues [42], but they also show additional chemically mediated interactions with the other partners. These include detection of the primary host s secretions by the hyperparasitoid [43], detection of plant volatiles by the hyperparasitoid [44], and detection of the hyperparasitoid s secretions by the primary host [45] or by the secondary host. The latter causes the secondary host to avoid locations where the hyperparasitoid is foraging [46]. 

For most of the world s plants mycorrhizae are the primary interface between physiologically active areas of the root and the external environment. Hence it is likely that many, perhaps most, allelochemical interactions Involving higher plant roots are mediated by the fungal symbiont. Herein we briefly review past research dealing with allelopathic effects on mycorrhizae, and discuss how interaction between mycorrhizae and chemicals may influence structural and functional aspects of ecosystems. Most studies to date have dealt with EM in forest ecosystems, and this is where our discussion will focus. 

Given that mitochondria, powerhouses of most eukaryotic cells, apparently emerged before chloroplasts, the most intriguing questions are centred around the nature of a primary host for the mitochondrial symbiont. These questions are the following ... 

Rubisco of Bacterial Endosymbionts of Hydrothermal Vent Animals Undersea hydrothermal vents support remarkable ecosystems. At these extreme depths there is no light to support photosynthesis, yet thriving vent communities are found. Much of their primary productivity occurs through chemosynthesis carried out by bacterial symbionts that live in specialized organs (trophosomes) of... 

Lichens are very sensitive indicators of sulphur dioxide pollution and their absence has been reported in many parts of the world. The primary target for the action of sulphur dioxide seems to be the algal symbiont, but the fungal symbiont is also negatively affected. 

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