Big Bacteria Sightings

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Science  10 Aug 2007:
Vol. 317, Issue 5839, pp. 723
DOI: 10.1126/science.317.5839.723a

Although communities of unusually large bacteria, like the gigantic 1-mm-diameter Thiomargarita spp. found off the Namibian coast in 1999, have only recently been discovered in marine sediments, it seems that they might occur widely in the benthos. During a long inter-El Niño (1998 to 2004) period along the western coast of South America, Gallardo and Espinoza discovered that fairly large (roughly 1 × 100 mm) filamentous bacteria could be recovered from sulfidic sediments overlain by oxygen-deficient water. As the El Niño-Southern Oscillation persisted, repeat sampling showed that the community shifted from a mixed eukaryote plus megabacteria (Thioploca spp.) composition to an exclusively anaerobic complex of the newly discovered filamentous bacteria (with an accompanying loss of megafauna). These macrobacteria appear to be diverse, presumably representing many ecotypes, and there are several phenotypes, some motile and some containing refractive sulfur granules. The authors speculate that very similar assemblages may have been present in anoxic pre-Cambrian oceans. — CA

Int. Microbiol. 10, 97 (2007).

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