Aerotaxis in Desulfovibrio

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Journal Article
Environmental Microbiology, 1999, 1 (6), pp. 489 - 494
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Aerotaxis of two sulphate-reducing bacteria, the freshwater strain Desulfovibrio desulfuricans CSN (DSM 9104) and the marine strain Desulfovibrio oxyclinae N13 (DSM 11498), was studied using capillary microslides, microscopy and oxygen microsensors. The bacteria formed ring-shaped bands in oxygen diffusion gradients surrounding O2bubbles, which were placed into anoxic sulphate-free cell suspensions in capillary microslides. The radial expansion of the oxic volume by diffusion was stopped by aerobic respiration. Bands were formed by cells avoiding high O2levels near the O2bubble, as well as by cells entering from the surrounding anoxic zone. At the inner edge of the bands, O2levels of up to 20% air saturation (50μM O2) were found, while the outer edge always coincided with the oxic-anoxic interface. Ring diameters and O2concentrations at the inner edge of the band depended on the cell density and the strain used in the suspension. Band formation did not occur in the absence of an electron donor (S mM lactate) or when N2gas bubbles were used. Both strains were highly motile with velocities of ≈ 32 μm s-1during forward runs, and 7 μm s-1during backward runs respectively. Within the bands, cells moved in circles of about 20 μm diameter, while cells outside the band exhibited straighter or only slightly bent traces. It is concluded that the capacity of respiration at high rates and the positive and negative aerotactical responses of Desulfovibrio provide an efficient strategy for removing O2from the habitat in situations where sufficient electron donors and high cell densities are present.
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