OXYGEN RESPONSES AND MAT FORMATION BY BEGGIATOA SPP

  • 1 January 1985
    • journal article
    • research article
    • Vol. 50  (2) , 373-382
Abstract
The behavioral response of single Beggiatoa sp. filaments moving on a gas-permeable membrane was studied by the combined use of microscopy and oxygen microelectrodes during controlled oscillations of O2 tension. The bacteria reacted to increasing O2 by reversing the direction of movement. The same step-up phobic response to O2 was observed when a filament tip or loop glided into a stable microgradient of increasing O2. The response was sensitive to a change in O2 tension of < 5% of air saturation min-1. The response time was 20-50 s. Frequently, only part of the filament responded, which led to the formation of sharp bends, loops and coils. This partial response facilitated the positioning of the long filaments within the narrow O2-H2S interface. The structure of whole Beggiatoa mats on sediment surfaces varied from loose to dense in relation to shallow or steep O2 gradients in the 0.3-2-mm-thick unstirred boundary layer. In an illuminated sediment, Beggiatoa spp. lived together with photosynthetic organisms and migrated vertically in accordance with light/dark variations. The combined effect of phobic responses to light and O2 can explain this migration.