Lezcano María Ángeles, Morón-López Jesús, Agha Ramsy, López-Heras Isabel, Nozal Leonor, Quesada Antonio, El-Shehawy Rehab
IMDEA Water Institute, Alcalá de Henares, Madrid 28805, Spain.
Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin 12587, Germany.
Toxins (Basel). 2016 Nov 3;8(11):318. doi: 10.3390/toxins8110318.
The microcystin biodegradation potential of a natural bacterial community coexisting with a toxic cyanobacterial bloom was investigated in a water reservoir from central Spain. The biodegradation capacity was confirmed in all samples during the bloom and an increase of A gene copies was found with increasing microcystin concentrations. Among the 24 microcystin degrading strains isolated from the bacterial community, only 28% showed presence of A gene, strongly supporting the existence and abundance of alternative microcystin degradation pathways in nature. In vitro degradation assays with both ⁺ and bacterial genotypes (with presence and absence of the complete gene cluster, respectively) were performed with four isolated strains ( sp. IM-1, IM-2 and IM-3; IM-4) and two bacterial degraders from the culture collection ( Y2; 2C20). Differences in microcystin degradation efficiencies between genotypes were found under different total organic carbon and total nitrogen concentrations. While ⁺ strains significantly improved microcystin degradation rates when exposed to other carbon and nitrogen sources, strains showed lower degradation efficiencies. This suggests that the presence of alternative carbon and nitrogen sources possibly competes with microcystins and impairs putative non- microcystin degradation pathways. Considering the abundance of the bacterial population and the increasing frequency of eutrophic conditions in aquatic systems, further research on the diversity of this population and the characterization and conditions affecting non- degradation pathways deserves special attention.
在西班牙中部的一个水库中，研究了与有毒蓝藻水华共存的天然细菌群落对微囊藻毒素的生物降解潜力。在水华期间的所有样品中均证实了生物降解能力，并且随着微囊藻毒素浓度的增加，发现A基因拷贝数增加。从细菌群落中分离出的24株微囊藻毒素降解菌株中，只有28%显示存在A基因，有力地支持了自然界中存在其他微囊藻毒素降解途径且其丰度较高。使用四株分离菌株（嗜麦芽窄食单胞菌sp. IM-1、IM-2和IM-3；苍白杆菌IM-4）以及两株来自培养物保藏中心的细菌降解菌（鞘氨醇单胞菌Y2；贪噬菌2C20），对具有⁺和⁻细菌基因型（分别具有完整的基因簇和不具有完整的基因簇）进行了体外降解试验。在不同的总有机碳和总氮浓度下，发现基因型之间微囊藻毒素降解效率存在差异。当暴露于其他碳源和氮源时，⁺菌株显著提高了微囊藻毒素的降解率，而⁻菌株显示出较低的降解效率。这表明其他碳源和氮源的存在可能与微囊藻毒素竞争，并损害假定的非途径微囊藻毒素降解途径。考虑到⁻细菌种群的丰度以及水生系统中富营养化状况的增加频率，对该种群的多样性以及影响非降解途径的特征和条件进行进一步研究值得特别关注。
