J. Craig Venter Institute, San Diego, CA, United States of America.
Exobiology Branch, NASA Ames Research Center, Mountain View, CA, United States of America.
PLoS One. 2020 Feb 19;15(2):e0227152. doi: 10.1371/journal.pone.0227152. eCollection 2020.
The opportunistic pathogens Burkholderia cepacia and Burkholderia contaminans, both genomovars of the Burkholderia cepacia complex (BCC), are frequently cultured from the potable water dispenser (PWD) of the International Space Station (ISS). Here, we sequenced the genomes and conducted phenotypic assays to characterize these Burkholderia isolates. All recovered isolates of the two species fall within monophyletic clades based on phylogenomic trees of conserved single-copy core genes. Within species, the ISS-derived isolates all demonstrate greater than 99% average nucleotide identity (with 95-99% of genomes aligning) and share around 90% of the identified gene clusters from a pangenomic analysis-suggesting that the two groups are each composed of highly similar genomic lineages and their members may have all stemmed from the same two founding populations. The differences that can be observed between the recovered isolates at the pangenomic level are primarily located within putative plasmids. Phenotypically, macrophage intracellularization and lysis occurred at generally similar rates between all ISS-derived isolates, as well as with their respective type-terrestrial strain references. All ISS-derived isolates exhibited antibiotic sensitivity similar to that of the terrestrial reference strains, and minimal differences between isolates were observed. With a few exceptions, biofilm formation rates were generally consistent across each species. And lastly, though isolation date does not necessarily provide any insight into how long a given isolate had been aboard the ISS, none of the assayed physiology correlated with either date of isolation or distances based on nucleotide variation. Overall, we find that while the populations of Burkholderia present in the ISS PWS each maintain virulence, they are likely are not more virulent than those that might be encountered on planet and remain susceptible to clinically used antibiotics.
机会性病原体伯克霍尔德菌和伯克霍尔德菌污染菌，都是伯克霍尔德菌复合群（BCC）的基因组变种，经常从国际空间站（ISS）的饮用水分配器（PWD）中培养出来。在这里，我们对这些伯克霍尔德菌分离株进行了基因组测序和表型分析，以对其进行特征描述。所有恢复的两个物种的分离株都基于保守的单拷贝核心基因的系统发育树，形成单系分支。在种内，ISS 来源的分离株均表现出大于 99%的平均核苷酸同一性（95-99%的基因组匹配），并且从泛基因组分析中共享约 90%的鉴定基因簇，这表明这两个群体各自由高度相似的基因组谱系组成，它们的成员可能都源自同一两个原始种群。在泛基因组水平上，可以观察到回收分离株之间的差异主要位于假定的质粒内。表型上，巨噬细胞内化和裂解在所有 ISS 来源的分离株之间以及它们各自的陆地参考株之间以相似的速度发生。所有 ISS 来源的分离株都表现出与陆地参考株相似的抗生素敏感性，并且在分离株之间观察到最小的差异。除了少数例外，生物膜形成率在每个物种中基本一致。最后，虽然分离日期不一定能说明给定的分离株在 ISS 上存在的时间长短，但所检测的生理特征与分离日期或基于核苷酸变异的距离均无相关性。总体而言，我们发现，虽然 ISS PWS 中存在的伯克霍尔德菌种群保持了毒力，但它们的毒力不太可能比在地球上可能遇到的毒力更强，并且仍然对临床上使用的抗生素敏感。
