Ultrastructure of organohalide-respiring Dehalococcoidia revealed by cryo-electron tomography

Posted: 2021-11-17 20:00:00
Dehalococcoides mccartyi (Dhc) and Dehalogenimonas spp. (Dhgm) are members of the class Dehalococcoidia, phylum Chloroflexi, characterized by streamlined genomes and a strict requirement for organohalogens as electron acceptors. Here, we used cryo-electron tomography to reveal morphological and ultrastructural features of Dhc strain BAV1 and 'Candidatus Dehalogenimonas etheniformans' strain GP cells at unprecedented resolution. Dhc cells were irregularly shaped discs (890 ± 110 nm long, 630 ± 110 nm wide and 130 ± 15 nm thick) with curved and straight sides that intersected at acute angles, whereas Dhgm cells appeared as slightly flattened cocci (760 ± 85 nm). The cell envelopes were composed of a cytoplasmic membrane (CM), a paracrystalline surface layer (S-layer) with hexagonal symmetry and ∼22 nm spacing between repeating units, and a layer of unknown composition separating the CM and the S-layer. Cell surface appendages were only detected in Dhc cells, whereas both cell types had bundled cytoskeletal filaments. Repetitive globular structures, ∼5 nm in diameter and ∼9 nm apart, were observed associated with the outer leaflet of the CM. We hypothesized that those represent organohalide respiration (OHR) complexes and estimated ∼30,000 copies per cell. In Dhgm cultures, extracellular lipid vesicles (20 - 110 nm in diameter) decorated with putative OHR complexes but lacking an S-layer were observed. The new findings expand our understanding of the unique cellular ultrastructure and biology of organohalide-respiring Dehalococcoidia. Importance: Dehalococcoidia respire organohalogen compounds and play relevant roles in bioremediation of groundwater, sediments and soils impacted with toxic chlorinated pollutants. Using advanced imaging tools, we have obtained 3-dimensional images at macromolecular resolution of whole Dehalococcoidia cells revealing their unique structural components. Our data detail the overall cellular shape, cell envelope architecture, cytoskeletal filaments, the likely localization of enzymatic complexes involved in reductive dehalogenation, and the structure of extracellular vesicles. The new findings expand our understanding of the cell structure-function relationship in Dehalococcoidia with implications for Dehalococcoidia biology and bioremediation.

参考サイト PubMed: exsome

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7月 03, 2021 バイオアソシエイツ


UCLAヘルスの研究者らは、パーキンソン病と多系統萎縮症(MSA)というよく似た2つの運動障害を見分けることができる血液検査を開発した。この検査法は、脳細胞から送り出されて血液中に混入する「 エクソソーム 」と呼ばれる微小な小胞の内容物を分析することで、パーキンソン病を識別するもので、現在は研究用に限定されている。 今回の研究成果は、2021年5月15日付でActa…

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