He Jianzhong, Holmes Victor F, Lee Patrick K H, Alvarez-Cohen Lisa
726 Davis Hall, Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720-1710, USA.
Appl Environ Microbiol. 2007 May;73(9):2847-53. doi: 10.1128/AEM.02574-06. Epub 2007 Mar 2.
Bacteria belonging to the genus Dehalococcoides play a key role in the complete detoxification of chloroethenes as these organisms are the only microbes known to be capable of dechlorination beyond dichloroethenes to vinyl chloride (VC) and ethene. However, Dehalococcoides strains usually grow slowly with a doubling time of 1 to 2 days and have complex nutritional requirements. Here we describe the growth of Dehalococcoides ethenogenes 195 in a defined mineral salts medium, improved growth of strain 195 when the medium was amended with high concentrations of vitamin B(12), and a strategy for maintaining Dehalococcoides strains on lactate by growing them in consortia. Although strain 195 could grow in defined medium spiked with approximately 0.5 mM trichloroethene (TCE) and 0.001 mg/liter vitamin B(12), the TCE dechlorination and cellular growth rates doubled when the vitamin B(12) concentration was increased 25-fold to 0.025 mg/liter. In addition, the final ratios of ethene to VC increased when the higher vitamin concentration was used, which reflected the key role that cobalamin plays in dechlorination reactions. No further improvement in dechlorination or growth was observed when the vitamin B(12) concentration was increased to more than 0.025 mg/liter. In defined consortia containing strain 195 along with Desulfovibrio desulfuricans and/or Acetobacterium woodii and containing lactate as the electron donor, tetrachloroethene ( approximately 0.4 mM) was completely dechlorinated to VC and ethene and there was concomitant growth of Dehalococcoides cells. In the cultures that also contained D. desulfuricans and/or A. woodii, strain 195 cells grew to densities that were 1.5 times greater than the densities obtained when the isolate was grown alone. The ratio of ethene to VC was highest in the presence of A. woodii, an organism that generates cobalamin de novo during metabolism. These findings demonstrate that the growth of D. ethenogenes strain 195 in defined medium can be optimized by providing high concentrations of vitamin B(12) and that this strain can be grown to higher densities in cocultures with fermenters that convert lactate to generate the required hydrogen and acetate and that may enhance the availability of vitamin B(12).
属于脱卤球菌属的细菌在氯乙烯的完全解毒过程中起着关键作用，因为这些微生物是已知的唯一能够将二氯乙烯进一步脱氯生成氯乙烯（VC）和乙烯的微生物。然而，脱卤球菌菌株通常生长缓慢，倍增时间为1至2天，并且营养需求复杂。在此，我们描述了脱卤产乙烯菌195在限定的矿物盐培养基中的生长情况，当培养基用高浓度的维生素B12进行改良时，菌株195的生长得到改善，以及通过在混合培养物中培养来维持脱卤球菌菌株以乳酸为营养源的策略。虽然菌株195能够在添加了约0.5 mM三氯乙烯（TCE）和0.001 mg/升维生素B12的限定培养基中生长，但当维生素B12浓度增加25倍至0.025 mg/升时，TCE脱氯和细胞生长速率增加了一倍。此外，使用较高维生素浓度时，乙烯与VC的最终比例增加，这反映了钴胺素在脱氯反应中所起的关键作用。当维生素B12浓度增加到超过0.025 mg/升时，未观察到脱氯或生长有进一步改善。在含有菌株195以及脱硫脱硫弧菌和/或木醋杆菌且以乳酸作为电子供体的限定混合培养物中，四氯乙烯（约0.4 mM）被完全脱氯生成VC和乙烯，同时脱卤球菌细胞也随之生长。在还含有脱硫脱硫弧菌和/或木醋杆菌的培养物中，菌株195细胞生长达到的密度比该分离菌株单独培养时获得的密度高1.5倍。在木醋杆菌存在的情况下，乙烯与VC的比例最高，木醋杆菌是一种在代谢过程中能从头合成钴胺素的微生物。这些发现表明，通过提供高浓度的维生素B12可以优化脱卤产乙烯菌195在限定培养基中的生长，并且该菌株与能将乳酸转化以产生所需氢气和乙酸且可能提高维生素B12可用性的发酵菌共培养时可以生长到更高的密度。
