Lomans B P, den Camp H J, Pol A, Vogels G D
Department of Microbiology and Evolutionary Biology, Faculty of Science, University of Nijmegen, NL-6525 ED Nijmegen, The Netherlands.
Appl Environ Microbiol. 1999 Feb;65(2):438-43. doi: 10.1128/AEM.65.2.438-443.1999.
Degradation of dimethyl sulfide and methanethiol in slurries prepared from sediments of minerotrophic peatland ditches were studied under various conditions. Maximal aerobic dimethyl sulfide-degrading capacities (4.95 nmol per ml of sediment slurry. h-1), measured in bottles shaken under an air atmosphere, were 10-fold higher than the maximal anaerobic degrading capacities determined from bottles shaken under N2 or H2 atmosphere (0.37 and 0. 32 nmol per ml of sediment slurry. h-1, respectively). Incubations under experimental conditions which mimic the in situ conditions (i. e., not shaken and with an air headspace), however, revealed that aerobic degradation of dimethyl sulfide and methanethiol in freshwater sediments is low due to oxygen limitation. Inhibition studies with bromoethanesulfonic acid and sodium tungstate demonstrated that the degradation of dimethyl sulfide and methanethiol in these incubations originated mainly from methanogenic activity. Prolonged incubation under a H2 atmosphere resulted in lower dimethyl sulfide degradation rates. Kinetic analysis of the data resulted in apparent Km values (6 to 8 microM) for aerobic dimethyl sulfide degradation which are comparable to those reported for Thiobacillus spp., Hyphomicrobium spp., and other methylotrophs. Apparent Km values determined for anaerobic degradation of dimethyl sulfide (3 to 8 microM) were of the same order of magnitude. The low apparent Km values obtained explain the low dimethyl sulfide and methanethiol concentrations in freshwater sediments that we reported previously. Our observations point to methanogenesis as the major mechanism of dimethyl sulfide and methanethiol consumption in freshwater sediments.
我们研究了在不同条件下，从贫营养泥炭地沟渠沉积物制备的泥浆中，二甲基硫醚和甲硫醇的降解情况。在空气氛围中振荡的瓶子中测得的最大好氧二甲基硫醚降解能力（每毫升沉积物泥浆每小时4.95纳摩尔），比在氮气或氢气氛围中振荡的瓶子中测定的最大厌氧降解能力（分别为每毫升沉积物泥浆每小时0.37和0.32纳摩尔）高10倍。然而，在模拟原位条件（即不振荡且有空气顶空）的实验条件下进行的培养表明，由于氧气限制，淡水沉积物中二甲基硫醚和甲硫醇的好氧降解很低。用溴乙烷磺酸和钨酸钠进行的抑制研究表明，这些培养中，二甲基硫醚和甲硫醇的降解主要源于产甲烷活性。在氢气氛围下长时间培养导致二甲基硫醚降解速率降低。对数据的动力学分析得出好氧二甲基硫醚降解的表观Km值（6至8微摩尔），这与硫杆菌属、生丝微菌属和其他甲基营养菌报道的表观Km值相当。二甲基硫醚厌氧降解的表观Km值（3至8微摩尔）处于相同数量级。获得的低表观Km值解释了我们之前报道的淡水沉积物中二甲基硫醚和甲硫醇的低浓度。我们的观察结果表明，产甲烷作用是淡水沉积物中二甲基硫醚和甲硫醇消耗的主要机制。
