@article {cho_genomic_2024,
	title = {Genomic analyses of Symbiomonas scintillans show no evidence for endosymbiotic bacteria but does reveal the presence of giant viruses},
	journal = {PLOS Genetics},
	volume = {20},
	number = {4},
	year = {2024},
	note = {Publisher: Public Library of Science},
	pages = {e1011218},
	abstract = {Symbiomonas scintillans Guillou et Chr{\'e}tiennot-Dinet, 1999 is a tiny (1.4 μm) heterotrophic microbial eukaryote. The genus was named based on the presence of endosymbiotic bacteria in its endoplasmic reticulum, however, like most such endosymbionts neither the identity nor functional association with its host were known. We generated both amplification-free shotgun metagenomics and whole genome amplification sequencing data from S. scintillans strains RCC257 and RCC24, but were unable to detect any sequences from known lineages of endosymbiotic bacteria. The absence of endobacteria was further verified with FISH analyses. Instead, numerous contigs in assemblies from both RCC24 and RCC257 were closely related to prasinoviruses infecting the green algae Ostreococcus lucimarinus, Bathycoccus prasinos, and Micromonas pusilla (OlV, BpV, and MpV, respectively). Using the BpV genome as a reference, we assembled a near-complete 190 kbp draft genome encoding all hallmark prasinovirus genes, as well as two additional incomplete assemblies of closely related but distinct viruses from RCC247, and three similar draft viral genomes from RCC24, which we collectively call SsVs. A multi-gene tree showed the three SsV genome types branched within highly supported clades with each of BpV2, OlVs, and MpVs, respectively. Interestingly, transmission electron microscopy also revealed a 190 nm virus-like particle similar the morphology and size of the endosymbiont originally reported in S. scintillans. Overall, we conclude that S. scintillans currently does not harbour an endosymbiotic bacterium, but is associated with giant viruses.},
	keywords = {Eukaryota, Gene prediction, genomics, metagenomics, RCC24, RCC257, Shotgun sequencing, Transcriptome analysis, Viral genomics, Whole genome amplification},
	issn = {1553-7404},
	doi = {10.1371/journal.pgen.1011218},
	url = {https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1011218},
	author = {Cho, Anna and Lax, Gordon and Livingston, Samuel J. and Masukagami, Yumiko and Naumova, Mariia and Millar, Olivia and Husnik, Filip and Keeling, Patrick J.}
}
@article {Kashiyama2019,
	title = {Taming chlorophylls by early eukaryotes underpinned algal interactions and the diversification of the eukaryotes on the oxygenated Earth},
	journal = {The ISME Journal},
	year = {2019},
	note = {Publisher: Springer US tex.mendeley-tags: RCC164,RCC22,RCC24,RCC375,RCC916},
	month = {feb},
	pages = {1},
	abstract = {Extant eukaryote ecology is primarily sustained by oxygenic photosynthesis, in which chlorophylls play essential roles. The exceptional photosensitivity of chlorophylls allows them to harvest solar energy for photosynthesis, but on the other hand, they also generate cytotoxic reactive oxygen species. A risk of such phototoxicity of the chlorophyll must become particularly prominent upon dynamic cellular interactions that potentially disrupt the mechanisms that are designed to quench photoexcited chlorophylls in the phototrophic cells. Extensive examination of a wide variety of phagotrophic, parasitic, and phototrophic microeukaryotes demonstrates that a catabolic process that converts chlorophylls into nonphotosensitive 132,173-cyclopheophorbide enols (CPEs) is phylogenetically ubiquitous among extant eukaryotes. The accumulation of CPEs is identified in phagotrophic algivores belonging to virtually all major eukaryotic assemblages with the exception of Archaeplastida, in which no algivorous species have been reported. In addition, accumulation of CPEs is revealed to be common among phototrophic microeukaryotes (i.e., microalgae) along with dismantling of their secondary chloroplasts. Thus, we infer that CPE-accumulating chlorophyll catabolism (CACC) primarily evolved among algivorous microeukaryotes to detoxify chlorophylls in an early stage of their evolution. Subsequently, it also underpinned photosynthetic endosymbiosis by securing close interactions with photosynthetic machinery containing abundant chlorophylls, which led to the acquisition of secondary chloroplasts. Our results strongly suggest that CACC, which allowed the consumption of oxygenic primary producers, ultimately permitted the successful radiation of the eukaryotes throughout and after the late Proterozoic global oxygenation.},
	keywords = {Biochemistry, Biogeochemistry, Cellular microbiology, microbial ecology, RCC164, RCC22, RCC24, RCC375, RCC916},
	issn = {1751-7362},
	doi = {10.1038/s41396-019-0377-0},
	url = {http://www.nature.com/articles/s41396-019-0377-0},
	author = {Kashiyama, Yuichiro and Yokoyama, Akiko and Shiratori, Takashi and Hess, Sebastian and Not, Fabrice and Bachy, Charles and Gutierrez-Rodriguez, Andres and Kawahara, Jun and Suzaki, Toshinobu and Nakazawa, Masami and Ishikawa, Takahiro and Maruyama, Moe and Wang, Mengyun and Chen, Man and Gong, Yingchun and Seto, Kensuke and Kagami, Maiko and Hamamoto, Yoko and Honda, Daiske and Umetani, Takahiro and Shihongi, Akira and Kayama, Motoki and Matsuda, Toshiki and Taira, Junya and Yabuki, Akinori and Tsuchiya, Masashi and Hirakawa, Yoshihisa and Kawaguchi, Akane and Nomura, Mami and Nakamura, Atsushi and Namba, Noriaki and Matsumoto, Mitsufumi and Tanaka, Tsuyoshi and Yoshino, Tomoko and Higuchi, Rina and Yamamoto, Akihiro and Maruyama, Tadanobu and Yamaguchi, Aika and Uzuka, Akihiro and Miyagishima, Shinya and Tanifuji, Goro and Kawachi, Masanobu and Kinoshita, Yusuke and Tamiaki, Hitoshi}
}
