Mycoavidus sp. Strain B2-EB: Comparative Genomics Reveals Minimal Genomic Features Required by a Cultivable Burkholderiaceae-Related Endofungal Bacterium
Mycoavidus sp. Strain B2-EB: Comparative Genomics Reveals Minimal Genomic Features Required by a Cultivable Burkholderiaceae-Related Endofungal Bacterium
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DOI：
10.1128/aem.01018-20
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发表时间：
2020-09-01
影响因子：
4.4
通讯作者：
Nishizawa, Tomoyasu
中科院分区：
文献类型：
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作者：
Guo, Yong;Takashima, Yusuke;Nishizawa, Tomoyasu
专性细菌内共生体对许多真核生物的存在至关重要。这种内细菌的特征通常是基因组减少和对宿主的代谢依赖性，这可能导致难以在纯培养物中分离它们。隶属于Mycoavidus-Glomeribacter分支的Burkholdiaceae家族相关内生真菌细菌可以与真菌被孢霉亚门和Glomeromycotina亚门相关。本研究成功获得了一株存在于小孢被孢霉（Mortierella parvispora）中的可培养内共生细菌Mycoavidus sp. strain B2-EB。B2-EB基因组（1.88 Mb）代表了细长被孢霉的内生真菌细菌Mycoavidus cysteinexigens（2.64-2.80 Mb）和丛枝菌根真菌的未培养的内共生体“Glomeribacter gigasporarum”（1.37 - 2.36 Mb）中最小的基因组。尽管基因组大小减小，但菌株B2-EB显示出高基因组完整性，表明B2-EB基因组的非退化性减少。与其他已知的Mycoavidus基因组中大比例的转座因子（TE）（占总基因组长度的7.2%至11.5%）相比，TE仅占B2-EB基因组的2.4%。这种模式，以及B2-EB基因组中高比例的单拷贝基因，表明B2-EB基因组达到了相对进化稳定的状态。这些结果代表了可培养的内生真菌细菌中最精简的结构，并表明内生真菌生活方式和人工培养所需的最小基因组特征。这项研究使我们能够了解伯克霍尔德菌相关的内共生菌的基因组进化，并阐明微生物interactions.IMPORTANCE本研究试图分离一种新的内细菌，Mycoavidus SP。B2-EB（JCM 33615），窝藏在真菌宿主小孢被孢霉E1425（JCM 39028）。我们报告了该菌株的全基因组序列，该菌株具有相对较高的基因组完整性和精简的基因组结构，基因组大小减小。这些信息表明了内生真菌生活方式和人工培养所需的最小基因组特征，这进一步加深了我们对真菌内共生体基因组减少的理解，并为工程合成微生物组的生物技术开发扩展了培养资源。
Obligate bacterial endosymbionts are critical to the existence of many eukaryotes. Such endobacteria are usually characterized by reduced genomes and metabolic dependence on the host, which may cause difficulty in isolating them in pure cultures. Family Burkholderiaceae-related endofungal bacteria affiliated with the Mycoavidus-Glomeribacter clade can be associated with the fungal subphyla Mortierellomycotina and Glomeromycotina. In this study, a cultivable endosymbiotic bacterium, Mycoavidus sp. strain B2-EB, present in the fungal host Mortierella parvispora was obtained successfully. The B2-EB genome (1.88 Mb) represents the smallest genome among the endofungal bacterium Mycoavidus cysteinexigens (2.64-2.80 Mb) of Mortierella elongata and the uncultured endosymbiont "Candidatus Glomeribacter gigasporarum" (1.37 to 2.36 Mb) of arbuscular mycorrhizal fungi. Despite a reduction in genome size, strain B2-EB displays a high genome completeness, suggesting a nondegenerative reduction in the B2-EB genome. Compared with a large proportion of transposable elements (TEs) in other known Mycoavidus genomes (7.2 to 11.5% of the total genome length), TEs accounted for only 2.4% of the B2-EB genome. This pattern, together with a high proportion of single-copy genes in the B2-EB genome, suggests that the B2-EB genome reached a state of relative evolutionary stability. These results represent the most streamlined structure among the cultivable endofungal bacteria and suggest the minimal genome features required by both an endofungal lifestyle and artificial culture. This study allows us to understand the genome evolution of Burkholderiaceae-related endosymbionts and to elucidate microbiological interactions.IMPORTANCE This study attempted the isolation of a novel endobacterium, Mycoavidus sp. B2-EB (JCM 33615), harbored in the fungal host Mortierella parvispora E1425 (JCM 39028). We report the complete genome sequence of this strain, which possesses a reduced genome size with relatively high genome completeness and a streamlined genome structure. The information indicates the minimal genomic features required by both the endofungal lifestyle and artificial cultivation, which furthers our understanding of genome reduction in fungal endosymbionts and extends the culture resources for biotechnological development on engineering synthetic microbiomes.