Aminobacter MSH1-Mineralisation of BAM in Sand-Filters Depends on Biological Diversity

BAM (2,6-dichlorobenzamide) is a metabolite of the pesticide dichlobenil. Naturally occurring bacteria that can utilize BAM are rare. Often the compound cannot be degraded before it reaches the groundwater and therefore it poses a serious threat to drinking water supplies. The bacterial strain Aminobacter MSH1 is a BAM degrader and therefore a potential candidate to be amended to sand filters in waterworks to remediate BAM polluted drinking water. A common problem in bioremediation is that bacteria artificially introduced into new diverse environments often thrive poorly, which is even more unfortunate because biologically diverse environments may ensure a more complete decomposition. To test the bioaugmentative potential of MSH1, we used a serial dilution approach to construct microcosms with different biological diversity. Subsequently, we amended Aminobacter MSH1 to the microcosms in two final concentrations; i.e. 105 cells mL-1 and 107 cells mL-1. We anticipated that BAM degradation would be most efficient at “intermediate diversities” as low diversity would counteract decomposition because of incomplete decomposition of metabolites and high diversity would be detrimental because of eradication of Aminobacter MSH1. This hypothesis was only confirmed when Aminobacter MSH1 was amended in concentrations of 105 cells mL-1.Our findings suggest that Aminobacter MSH1 is a very promising bioremediator at several diversity levels.

BAM（2,6-dichlorobenzamide，2,6-二氯苯甲酰胺）是农药敌草腈（dichlorbenil）的代谢产物。自然界中能够降解并利用BAM的细菌十分罕见。该化合物往往在抵达地下水前尚未被降解，因此对饮用水供水安全构成严重威胁。细菌菌株Aminobacter MSH1属于BAM降解菌，因此可作为潜在修复菌剂投加至水厂的砂滤系统中，用于修复受BAM污染的饮用水体。生物修复领域常见的难题在于：人工引入至全新多样化环境中的细菌往往生长状况不佳，而这一情况尤为令人遗憾——因为生物多样性更高的环境本可实现更彻底的污染物降解。为验证MSH1的生物强化修复潜力，我们采用系列稀释法构建了具有不同生物多样性的微宇宙体系（microcosms）。随后，我们以两种终浓度将Aminobacter MSH1投加至微宇宙体系中：分别为10⁵ cells·mL⁻¹与10⁷ cells·mL⁻¹。我们曾推测，BAM降解效率将在"intermediate diversities"条件下达到最高：低多样性环境会因代谢物降解不完全而抑制整体降解过程，高多样性环境则会因Aminobacter MSH1被清除而不利于降解。该假说仅在以10⁵ cells·mL⁻¹的浓度投加Aminobacter MSH1时得到了验证。我们的研究结果表明，在多种多样性水平下，Aminobacter MSH1都是极具应用前景的生物修复菌剂。