Response of fluoranthene-degrading bacteria to surfactants |
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Authors: | P A Willumsen U Karlson P H Pritchard |
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Institution: | (1) Department of Marine Ecology and Microbiology, National Environmental Research Institute, Roskilde, Denmark e-mail: paw@dmu.dk Tel.: +45 46301200 Fax: +45 46301114, DK;(2) US Naval Research Laboratory (Code 6115), Environmental Quality Science Section, Washington, DC 20375, USA, US |
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Abstract: | A prerequisite for surfactant-enhanced biodegradation is that the microorganisms survive, take up substrate and degrade it
in the presence of the surfactant. Two Mycobacterium and two Sphingomonas strains, degrading fluoranthene, were investigated for their sensitivity towards non-ionic chemical surfactants. The effect
of Triton X-100 and Tween 80 above their critical micelle concentration on mineralization of 14C]-glucose and 14C]-fluoranthene was measured in shaker cultures. Tween 80 had no toxic effect on any of the tested strains. The surfactant
inhibited fluoranthene mineralization by the hydrophobic Mycobacterium spp. slightly, but more than doubled that by the two less hydrophobic Sphingomonas strains. Triton X-100 inhibited fluoranthene mineralization by all strains, yet this was more pronounced for the Sphingomonas spp. Both surfactants caused cell wall permeabilization, as shown by transient colouring of surfactant-containing media.
Inhibition of glucose mineralization, indicating non-specific toxic effects of Triton X-100, was observed only for the Sphingomonas strains and the toxicity was caused by micelle-to-cell interactions. These strains, however, appeared to recover from initial
Triton X-100 toxicity within 50–500 h of exposure. The ratio of surfactant concentration to initial cell density was found
to determine critically the bacterial response to surfactants. For both Sphingomonas and Mycobacterium strains, this work indicates that fluoranthene solubilized in surfactant micelles is only partially available for mineralization
by the bacteria tested. However, our results suggest that optimal conditions for polycyclic aromatic hydrocarbon mineralization
can be developed by selection of the proper surfactant, bacterial strains, cell density and incubation conditions.
Received: 6 February 1998 / Received revision: 19 June 1998 / Accepted: 19 June 1998 |
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