Rachedi Kounouz, Zermane Ferial, Tir Radja, Ayache Fatima, Duran Robert, Lauga Béatrice, Karama Solange, Simon Maryse, Boulahrouf Abderrahmane
Université Frères Mentouri, Faculté des Sciences de la Nature et de la Vie, Laboratoire de Génie Microbiologique et Applications, Constantine, Algeria; Université Frères Mentouri, Institut de la Nutrition, de l'Alimentation et des Technologies Agro-Alimentaires (INATAA), Constantine, Algeria.
Université Frères Mentouri, Faculté des Sciences de la Nature et de la Vie, Laboratoire de Génie Microbiologique et Applications, Constantine, Algeria; Université Frères Mentouri, Faculté des Sciences de la Nature et de la Vie, Département de Microbiologie, Constantine, Algeria.
Braz J Microbiol. 2018 Jan-Mar;49(1):79-86. doi: 10.1016/j.bjm.2017.05.004. Epub 2017 Aug 9.
Repeated application of pesticides disturbs microbial communities and cause dysfunctions on soil biological processes. Granstar 75 DF is one of the most used sulfonylurea herbicides on cereal crops; it contains 75% of tribenuron-methyl. Assessing the changes on soil microbiota, particularly on the most abundant bacterial groups, will be a useful approach to determine the impact of Granstar herbicide. For this purpose, we analyzed Actinobacteria, which are known for their diversity, abundance, and aptitude to resist to xenobiotic substances. Using a selective medium for Actinobacteria, 42 strains were isolated from both untreated and Granstar treated soils. The number of isolates recovered from the treated agricultural soil was fewer than that isolated from the corresponding untreated soil, suggesting a negative effect of Granstar herbicide on Actinobacteria community. Even so, the number of strains isolated from untreated and treated forest soil was quite similar. Among the isolates, resistant strains, tolerating high doses of Granstar ranging from 0.3 to 0.6% (v/v), were obtained. The two most resistant strains (SRK12 and SRK17) were isolated from treated soils showing the importance of prior exposure to herbicides for bacterial adaptation. SRK12 and SRK17 strains showed different morphological features. The phylogenetic analysis, based on 16S rRNA gene sequencing, clustered the SRK12 strain with four Streptomyces type strains (S. vinaceusdrappus, S. mutabilis, S. ghanaensis and S. enissocaesilis), while SRK17 strain was closely related to Streptomyces africanus. Both strains were unable to grow on tribenuron methyl as unique source of carbon, despite its advanced dissipation. On the other hand, when glucose was added to tribenuron methyl, the bacterial development was evident with even an improvement of the tribenuron methyl degradation. In all cases, as tribenuron methyl disappeared, two compounds were detected with increased concentrations. These by-products appeared to be persistent and were not degraded either chemically or by the studied strains. Based on these observations, we suggested that bacterial activity on carbon substrates could be directly involved in the partial breakdown of tribenuron methyl, by generating the required acidity for the first step of the hydrolysis. Such a process would be interesting to consider in bioremediation of neutral and alkaline tribenuron methyl-polluted soils.
反复施用农药会扰乱微生物群落，并导致土壤生物过程功能失调。巨星75 DF是谷物作物上使用最广泛的磺酰脲类除草剂之一；它含有75%的苯磺隆。评估土壤微生物群的变化，特别是最丰富细菌类群的变化，将是确定巨星除草剂影响的一种有用方法。为此，我们分析了放线菌，它们以其多样性、丰度和抵抗外源物质的能力而闻名。使用一种针对放线菌的选择性培养基，从未经处理和经巨星处理的土壤中分离出42株菌株。从处理过的农业土壤中回收的分离株数量少于从未经处理的相应土壤中分离出的数量，这表明巨星除草剂对放线菌群落有负面影响。即便如此，从未经处理和处理过的森林土壤中分离出的菌株数量相当相似。在这些分离株中，获得了耐受0.3%至0.6%（v/v）高剂量巨星的抗性菌株。两个抗性最强的菌株（SRK12和SRK17）是从处理过的土壤中分离出来的，这表明先前接触除草剂对细菌适应的重要性。SRK12和SRK17菌株表现出不同的形态特征。基于16S rRNA基因测序的系统发育分析将SRK12菌株与四种链霉菌属菌株（葡萄紫链霉菌、可变链霉菌、加纳链霉菌和嗜虫链霉菌）聚类在一起，而SRK17菌株与非洲链霉菌密切相关。尽管苯磺隆已大量消散，但这两种菌株都不能以苯磺隆作为唯一碳源生长。另一方面，当向苯磺隆中添加葡萄糖时，细菌生长明显，甚至苯磺隆的降解有所改善。在所有情况下，随着苯磺隆的消失，检测到两种浓度增加的化合物。这些副产物似乎具有持久性，既不能通过化学方法降解，也不能被所研究的菌株降解。基于这些观察结果，我们认为细菌对碳底物的活性可能直接参与苯磺隆的部分分解，通过产生水解第一步所需的酸度。在中性和碱性苯磺隆污染土壤的生物修复中考虑这样一个过程将很有意思。
