Section for Microbiology, Department of Biology, Aarhus University, Denmark; Center for Electromicrobiology, Aarhus University, Denmark; Center for Geomicrobiology, Aarhus University, Denmark.
Department for Molecular Biology and Genetics, Aarhus University, Denmark.
Syst Appl Microbiol. 2021 Sep;44(5):126236. doi: 10.1016/j.syapm.2021.126236. Epub 2021 Jul 22.
Cable bacteria are multicellular filamentous bacteria within the Desulfobulbaceae that couple the oxidation of sulfide to the reduction of oxygen over centimeter distances via long distance electron transport (LDET). So far, none of the freshwater or marine cable bacteria species have been isolated into pure culture. Here we describe a method for establishing a stable single-strain cable bacterium culture in partially sterilized sediment. By repeated transfers of a single cable bacterium filament from freshwater pond sediment into autoclaved sediment, we obtained strain GS, identified by its 16S rRNA gene as a member of Ca. Electronema. This strain was further propagated by transferring sediment clumps, and has now been stable within its semi-natural microbial community for several years. Its metagenome-assembled genome was 93% complete, had a size of 2.76 Mbp, and a DNA G + C content of 52%. Average Nucleotide Identity (ANI) and Average Amino Acid Identity (AAI) suggest the affiliation of strain GS to Ca. Electronema as a novel species. Cell size, number of outer ridges, and detection of LDET in the GS culture are likewise consistent with Ca. Electronema. Based on these combined features, we therefore describe strain GS as a new cable bacterium species of the candidate genus Electronema, for which we propose the name Candidatus Electronema aureum sp.nov. Although not a pure culture, this stable single-strain culture will be useful for physiological and omics-based studies; similar approaches with single-cell or single-filament transfers into natural medium may also aid the characterization of other difficult-to-culture microbes.
缆细菌是脱硫杆菌科中的多细胞丝状细菌，通过长距离电子传递（LDET）将硫化物的氧化与氧气的还原耦合在厘米距离内。到目前为止，尚未从淡水或海洋缆细菌物种中分离出纯培养物。在这里，我们描述了一种在部分灭菌沉积物中建立稳定的单一菌株缆细菌培养物的方法。通过将单个缆细菌丝从淡水池塘沉积物中反复转移到灭菌沉积物中，我们获得了菌株 GS，其 16S rRNA 基因鉴定为 Ca. Electronema 的成员。该菌株通过转移沉积物团进一步繁殖，现已在其半自然微生物群落中稳定存在数年。其宏基因组组装基因组的完整性为 93%，大小为 2.76 Mbp，DNA G+C 含量为 52%。平均核苷酸同一性（ANI）和平均氨基酸同一性（AAI）表明菌株 GS 与 Ca. Electronema 的隶属关系为一个新物种。GS 培养物的细胞大小、外脊数量和 LDET 的检测也与 Ca. Electronema 一致。基于这些综合特征，我们将菌株 GS 描述为一种新的缆细菌属候选属 Electronema 的物种，我们建议将其命名为新的缆细菌属候选属 Electronema aureum sp.nov。尽管不是纯培养物，但这种稳定的单一菌株培养物将有助于生理和组学研究；类似的方法，通过单细胞或单丝转移到天然培养基中，也可能有助于其他难以培养的微生物的特征描述。
