Bacterial diversity and aerobic catabolic competence of dioxin-degrading bacterial strains isolated from a polluted soil in the tropics were explored. Isolation of bacteria occurred after 12 months of consecutive enrichment, with dioxin congeners serving as the only sources of carbon and energy. Seventeen strains that were isolated were subsequently screened for dioxin metabolic competence. Among these isolates, five had unique amplified ribosomal DNA restriction analysis (ARDRA) patterns out of which two exhibiting good metabolic competence were selected for further investigation. The two strains were identified as Bacillus sp. SS2 and Serratia sp. SSA1, based on their 16S rRNA gene sequences. Bacterial growth co-occurred with dioxin disappearance and near stoichiometric release of chloride for one ring of the chlorinated congeners. The overall percentage removal of dibenzofuran (DF) by strain SS2 was 93.87%; while corresponding values for 2,8-dichlorodibenzofuran (2,8-diCDF) and 2,7-dichlorodibenzo-p-dioxin (2,7-diCDD) were 86.22% and 82.30% respectively. In the case of strain SSA1, percentage removal for DF, 2,8-diCDF and 2,7-diCDD were respectively 98.9%, 80.97% and 70.80%. The presence of two dioxin dioxygenase catabolic genes (dxnA1 and dbfA1) was investigated. Only the dbfA1 gene could be amplified in SS2 strain. Results further revealed that strain SS2 presented higher expression levels for the alpha-subunit of DF dioxygenase (dbfA1) gene during growth with dioxins. The expression level for dbfA1 gene was higher when growing on DF than on the other chlorinated analogs. This study gives an insight into dioxin degradation, with the catabolic potential of strains SS2 and SSA1 (an enteric bacterium) within the sub-Sahara Africa. It further shows that dioxin catabolic potential might be more prevalent in different groups of microorganisms than previously believed. Few reports have demonstrated the degradation of chlorinated congeners of dioxins, particularly from sub-Saharan African contaminated systems.

中文翻译：

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由热带污染土壤获得的细菌菌株对二氯二苯并二恶英和二氯呋喃进行好氧降解。

探索了从热带地区污染土壤中分离出的降解二恶英的细菌菌株的细菌多样性和需氧代谢能力。在连续富集12个月后，分离出细菌，其中二恶英同源物是唯一的碳和能量来源。随后从分离出的十七个菌株中筛选二恶英代谢能力。在这些分离物中，有五种具有独特的扩增核糖体DNA限制性内切酶分析（ARDRA）模式，从中选择了两种表现出良好代谢能力的基因进行进一步研究。这两个菌株被鉴定为芽孢杆菌。SS2和Serratiasp。SSA1，基于其16S rRNA基因序列。一环氯化同类物的细菌生长与二恶英消失和氯化物接近化学计量释放的氯化物同时发生。SS2菌株对二苯并呋喃（DF）的总去除率为93.87％；而2,8-二氯二苯并呋喃（2,8-diCDF）和2,7-二氯二苯并-对二恶英（2,7-diCDD）的相应值分别为86.22％和82.30％。在菌株SSA1的情况下，DF，2,8-diCDF和2,7-diCDD的去除百分数分别为98.9％，80.97％和70.80％。研究了两个二恶英双加氧酶分解代谢基因（dxnA1和dbfA1）的存在。只有dbfA1该基因可以在SS2菌株中扩增。结果进一步显示，菌株SS2在二恶英生长期间呈现出较高的DF双加氧酶（dbfA1）基因的α亚基表达水平。在DF上生长时，dbfA1基因的表达水平高于其他氯化类似物。这项研究对撒哈拉以南非洲地区SS2和SSA1（肠细菌）菌株的分解代谢潜力提供了二恶英降解的见解。它进一步表明，二恶英分解代谢潜能可能比以前认为的在不同种类的微生物中更为普遍。很少有报告显示二恶英的氯化同类物的降解，特别是来自撒哈拉以南非洲受污染系统的降解。