ECOLOGY/EVOLUTION: Recruiting a Luminous Partner

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Science  22 Sep 2000:
Vol. 289, Issue 5487, pp. 2005b

Symbioses between multicellular animals and microorganisms are commonplace in marine habitats. While a good deal is known about the mutual benefits derived from these associations, the mechanisms by which the partners make contact and establish a symbiosis every generation have remained mysterious. The turbulence of the marine environment and the vanishingly low concentrations of free-floating microbial cells present a substantial challenge.

The Hawaiian squid Euprymna scolopes has within its mantle cavity a light-emitting organ that depends for its function on colonization by the luminous bacterium Vibrio fischeri. Using a combination of transgenic and confocal microscopy techniques, Nyholm et al. find that the juvenile squid harvest their microbial partner by creating ciliary currents that cause the bacteria to aggregate on a mucus-like matrix; when Vibrio are present in the surrounding medium, this matrix is formed in response to a chemical signal that has not yet been identified. Several hours after inoculation and aggregation, the captured cells actively migrate along mucus strands to colonize the internal crypt spaces of the light-emitting organ. This partnership may typify mechanisms by which aquatic hosts increase the likelihood of encountering and capturing rare symbionts. — AMS

Acknowledgments

Proc. Natl. Acad. Sci. U.S.A.97, 10231 (2000).

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