Abstract
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Applied and Environmental Microbiology |
| Vol/bind | 67 |
| Udgave nummer | 12 |
| Sider (fra-til) | 5410-5419 |
| ISSN | 0099-2240 |
| DOI | |
| Status | Udgivet - 2001 |
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I: Applied and Environmental Microbiology, Bind 67, Nr. 12, 2001, s. 5410-5419.
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › peer review
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TY - JOUR
T1 - Motility of Marichromatium gracile in Response to Light, Oxygen, and Sulfide
AU - Thar, Roland Matthias
AU - Kühl, Michael
PY - 2001
Y1 - 2001
N2 - The motility of the purple sulfur bacterium Marichromatium gracile was investigated under different light regimes in a gradient capillary setup with opposing oxygen and sulfide gradients. The gradients were quantified with microsensors, while the behavior of swimming cells was studied by video microscopy in combination with a computerized cell tracking system. M. gracile exhibited photokinesis, photophobic responses, and phobic responses toward oxygen and sulfide. The observed migration patterns could be explained solely by the various phobic responses. In the dark, M. gracile formed an ~500-µm-thick band at the oxic-anoxic interface, with a sharp border toward the oxic zone always positioned at ~10 µM O2. Flux calculations yielded a molar conversion ratio Stot/O2 of 2.03:1 (Stot = [H2S] + [HS] + [S2]) for the sulfide oxidation within the band, indicating that in darkness the bacteria oxidized sulfide incompletely to sulfur stored in intracellular sulfur globules. In the light, M. gracile spread into the anoxic zone while still avoiding regions with >10 µM O2. The cells also preferred low sulfide concentrations if the oxygen was replaced by nitrogen. A light-dark transition experiment demonstrated a dynamic interaction between the chemical gradients and the cell's metabolism. In darkness and anoxia, M. gracile lost its motility after ca. 1 h. In contrast, at oxygen concentrations of >100 µM with no sulfide present the cells remained viable and motile for ca. 3 days both in light and darkness. Oxygen was respired also in the light, but respiration rates were lower than in the dark. Observed aggregation patterns are interpreted as effective protection strategies against high oxygen concentrations and might represent first stages of biofilm formation.
AB - The motility of the purple sulfur bacterium Marichromatium gracile was investigated under different light regimes in a gradient capillary setup with opposing oxygen and sulfide gradients. The gradients were quantified with microsensors, while the behavior of swimming cells was studied by video microscopy in combination with a computerized cell tracking system. M. gracile exhibited photokinesis, photophobic responses, and phobic responses toward oxygen and sulfide. The observed migration patterns could be explained solely by the various phobic responses. In the dark, M. gracile formed an ~500-µm-thick band at the oxic-anoxic interface, with a sharp border toward the oxic zone always positioned at ~10 µM O2. Flux calculations yielded a molar conversion ratio Stot/O2 of 2.03:1 (Stot = [H2S] + [HS] + [S2]) for the sulfide oxidation within the band, indicating that in darkness the bacteria oxidized sulfide incompletely to sulfur stored in intracellular sulfur globules. In the light, M. gracile spread into the anoxic zone while still avoiding regions with >10 µM O2. The cells also preferred low sulfide concentrations if the oxygen was replaced by nitrogen. A light-dark transition experiment demonstrated a dynamic interaction between the chemical gradients and the cell's metabolism. In darkness and anoxia, M. gracile lost its motility after ca. 1 h. In contrast, at oxygen concentrations of >100 µM with no sulfide present the cells remained viable and motile for ca. 3 days both in light and darkness. Oxygen was respired also in the light, but respiration rates were lower than in the dark. Observed aggregation patterns are interpreted as effective protection strategies against high oxygen concentrations and might represent first stages of biofilm formation.
U2 - 10.1128/AEM.67.12.5410-5419.2001
DO - 10.1128/AEM.67.12.5410-5419.2001
M3 - Journal article
SN - 0099-2240
VL - 67
SP - 5410
EP - 5419
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 12
ER -