The dechlorinating Dehalococcoides mccartyi species requires acetate as carbon source, but little is known on its growth under acetate limiting conditions. In this study, we observed growth and dechlorination of a D. mccartyi-containing mixed consortium in a fixed-carbon-free medium with trichloroethene in the aqueous phase and H₂/CO₂ in the headspace. Around 4 mM formate was produced by day 40, while acetate was constantly below 0.05 mM. Microbial community analysis of the consortium revealed dominance by D. mccartyi and Desulfovibrio sp. (57 and 22% 16S rRNA gene copies, respectively). From this consortium, Desulfovibrio sp. strain F1 was isolated and found to produce formate and acetate (1.2 mM and 48 µM, respectively, by day 24) when cultivated alone in the above mentioned medium without trichloroethene. An established co-culture of strain F1 and D. mccartyi strain 195 demonstrated that strain 195 could grow and dechlorinate using acetate produced by strain F1; and that acetate was constantly below 25 µM in the co-culture. To verify that such low level of acetate is utilizable by D. mccartyi, we cultivated strain 195 alone under acetate-limiting conditions and found that strain 195 consumed acetate to below detection (5 µM). Based on the acetate consumption and cell yield of D. mccartyi, we estimated that on average 1.2 × 10⁸ acetate molecules are needed to supply carbon for one D. mccartyi cell. Our study suggests that Desulfovibrio may supply a steady but low amount of fixed carbon to dechlorinating bacteria, exhibiting important implications for natural bio-attenuation when fixed carbon is limited.

中文翻译：

---

Dehalococcoidesides mccartyi种在产生有限乙酸盐的自养联合体中的生长。

脱氯的麦卡迪氏菌需要乙酸盐作为碳源，但在乙酸盐限制条件下的生长情况鲜为人知。在这项研究中，我们观察到了含D. mccartyi的混合财团在无碳固定介质中的生长和脱氯，其中三氯乙烯在水相中，H ₂ / CO ₂在顶部空间中。到第40天，产生了约4 mM的甲酸盐，而乙酸盐始终低于0.05 mM。该财团的微生物群落分析显示，D。mccartyi和Desulfovibrio sp。占主导地位。（分别为57％和22％的16S rRNA基因拷贝）。来自这个财团的Desulfovibriosp。分离出菌株F1，发现在上述不含三氯乙烯的培养基中单独培养时，菌株F1产生甲酸和乙酸盐（到第24天分别为1.2mM和48μM）。已建立的菌株F1和麦卡氏梭菌195的共培养表明，菌株195可以使用菌株F1产生的乙酸盐生长并脱氯。在共培养中，乙酸盐始终低于25 µM。为了验证D. mccartyi可利用如此低的乙酸盐含量，我们在乙酸盐限制条件下单独培养了195号菌株，发现195号菌株消耗的乙酸盐含量低于检测值（5 µM）。根据D. mccartyi的乙酸盐消耗量和细胞产量，我们估计平均为1.2×10 ⁸需要乙酸盐分子为一个麦卡氏梭菌细胞提供碳。我们的研究表明，脱硫弧菌可能为脱氯细菌提供稳定但少量的固定碳，当固定碳受到限制时，对自然生物衰减显示出重要意义。