A previous cultivation-independent investigation of the microbial community structure of natural oil and asphalt seeps in the Kurdistan Region of Iraq (KRI) revealed the dominance of uncultured bacterial taxa belonging to the phyla Deferribacterota and Coprothermobacterota and the orders Thermodesulfobacteriales, Thermales, and Burkholderiales. Here we report on a cultivation-dependent approach to identify members of these groups involved in hydrocarbon degradation in the KRI oil and asphalt seeps. For this purpose, we set up anoxic crude oil-degrading enrichment cultures based on cultivation media known to support the growth of members of the above-mentioned taxonomic groups. During 100–200 days incubation periods, nitrate-reducing and fermentative enrichments showed up to 90% degradation of C₈–C₁₇ alkanes and up to 28% degradation of C₁₈–C₃₃ alkanes along with aromatic hydrocarbons. Community profiling of the enrichment cultures showed that they were dominated by diverse bacterial taxa, which were rare in situ community members in the investigated seeps. Groups initially targeted by our approach were not enriched, possibly because their members are slow-growing and involved in the degradation of recalcitrant hydrocarbons. Nevertheless, the enriched taxa were taxonomically related to phylotypes recovered from hydrocarbon-impacted environments as well as to characterized bacterial isolates not previously known to be involved in hydrocarbon degradation. Marker genes (assA and bssA), diagnostic for fumarate addition-based anaerobic hydrocarbon degradation, were not detectable in the enrichment cultures by PCR. We conclude that hydrocarbon biodegradation in our enrichments occurred via unknown pathways and synergistic interactions among the enriched taxa. We suggest, that although not representing abundant populations in situ, studies of the cultured close relatives of these taxa will reveal an unrecognized potential for anaerobic hydrocarbon degradation, possibly involving poorly characterized mechanisms.

先前对伊拉克库尔德斯坦地区（KRI）的天然油和沥青渗漏微生物群落结构进行的独立于培养的研究表明，未培养的细菌类群占主导地位，属于菌种Deferribacterota和Coprothermobacterota，并且顺序为Thermodesulfobacteriales，Thermales和Burkholderiales。在这里，我们报告了一种依赖于耕作的方法，以识别参与KRI油和沥青渗漏的烃降解的这些族群中的成员。为此，我们基于已知支持上述生物分类群成员生长的培养基建立了缺氧降解原油的富集培养物。在100-200天的潜伏期中，硝酸盐还原和发酵富集显示C ₈ –C降解高达90％_17种烷烃以及最多₁₈％的C ₁₈ –C ₃₃烷烃与芳烃的降解。丰富文化的社区概况表明，它们被多种细菌分类所支配，这在所研究的渗漏中是很少见的原位社区成员。我们的方法最初针对的组没有得到充实，这可能是因为它们的成员增长缓慢并且参与了难降解碳氢化合物的降解。然而，富集的分类群在分类学上与从受碳氢化合物影响的环境中回收的系统型有关，并且与以前不参与碳氢化合物降解的特征性细菌分离株有关。标记基因（assA和bssAPCR不能在富集培养物中检测到富马酸酯加成型厌氧烃降解的诊断）。我们得出的结论是，我们富集区中的烃类生物降解是通过未知途径和富集类群之间的协同相互作用发生的。我们建议，尽管不能代表原地丰富的种群，但对这些分类单元的近亲的培养研究表明，厌氧碳氢化合物的降解潜力尚未得到认可，可能涉及机制较差的特征。