著者

Ryuji Yanase Yukinori Nishigami Masatoshi Ichikawa Tohru Yoshihisa Seiji Sonobe

出版者

Japan Society of Protistology

雑誌

Journal of Protistology (ISSN:2433412X)

巻号頁・発行日

vol.51, pp.1-6, 2018-03-05 (Released:2018-03-08)

参考文献数

24

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The free-living ciliate protist Lacrymaria olor has an extendable neck, which extends up to 8 times longer than its cell body. Previous papers assessed several ultrastructural features of L. olor; however, dynamic features of the extension and contraction cycle of the neck have been unclear. As a first step to understand the mechanism of such dynamic processes, we tried to characterize the neck deformation of living L. olor using a high-speed camera and image processing. These analyses defined the four different cell states, namely, active, resting, activation and inactivation, and highlighted the features of the neck deformation of L. olor depending upon the cell states. Our analyses will make it possible to elucidate further details of the L. olor neck deformation mechanism.

著者

Liudmyla Gaponova Toshinobu Suzaki Md Shafiqul Islam Andrii Kolosiuk

出版者

Japan Society of Protistology

雑誌

Journal of Protistology (ISSN:2433412X)

巻号頁・発行日

vol.53, pp.e004, 2021-12-23 (Released:2021-12-23)

参考文献数

22

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Actinophryid and centrohelid heliozoans often share the same habitat; however, field studies have shown that they preferentially exist separately than together, suggesting the existence of a mechanism that does not allow them to co-exist. Therefore, to clarify the interactions between these heliozoans, co-culturing experiments, involving two organisms, an actinophryid and a centrohelid, were performed. For the experiments in the brackish water environment, Actinophrys sol (actinophryid) and Raphidocystis contractilis (centrohelid) were used, and for those in the freshwater environment, a combination of Actinosphaerium eichhornii (actinophryid) and one of three centrohelid species (Choanocystis pantopoda, Raphidocystis ambigua, or Raphidocystis marginata) were used. In all the experiments involving the co-culture environments, the centrohelids grew intensively within the first 3-5 days, after which their cell numbers remained constant. Conversely, the number of actinophryid heliozoans decreased significantly and their disappearance was recorded after 2 days and after 5-11 days for the experiments in the brackish water and freshwater environments, respectively. Further, in some experiments, several centrohelid cells fused together to form a giant multinucleated cell, which jointly, captured and consumed larger organisms, such as Actinophrys sol. Furthermore, Actinosphaerium eichhornii (actinophryid) exhibited an avoidance response against Choanocystis pantopoda (centrohelid) attack. Thus, our experimental results showed that in mixed co-culture environments, centrohelids inhibit the growth of actinophryids. This possibly explains the exclusive mode of existence of these two groups of heliozoans in the natural environment.

著者

Akinori Yabuki Masaru Kawato Yuriko Nagano Shinji Tsuchida Takao Yoshida Yoshihiro Fujiwara

出版者

Japan Society of Protistology

雑誌

Journal of Protistology (ISSN:2433412X)

巻号頁・発行日

vol.52, pp.1-5, 2020-07-27 (Released:2020-07-27)

参考文献数

19

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Diplonemea is one of the most abundant and species-rich protist groups in marine environments. However, many lineages are still undescribed. Particularly, little is understood about members of the ‘deep-sea and pelagic diplonemids (DSPD)’ clade. The environmental DNA (eDNA) studies conducted with universal eukaryotic primers have shown that DSPDs were also abundantly distributed in natural environments, but their cultures have not yet been established. For future studies such as mitochondrial genome sequencing, culture establishment is needed. For establishing cultures, it is important to select samples containing a high quantity of diplonemids. In this study, we designed new diplonemid primers for eDNA analysis using a next-generation sequencer, testing its efficiency using eDNA that was extracted from two deep-sea water samples. Out of a total of 58,154 assembled reads, 57,633 reads (i.e. 99.1%) were affiliated with diplonemids by BLAST and reconstructed into 160 representative sequences. Phylogenetic analyses showed that many of the representative sequences (137 sequences, 85.6%) were branched within the DSPD clade and family Hemistasiidae. These findings indicate that the new primers are useful in monitoring diplonemid diversity and acquiring information for the establishment of DSPD cultures.

著者

Masashi Yamaguchi Cedric O’Driscoll Worman

出版者

Japan Society of Protistology

雑誌

原生動物学雑誌 (ISSN:03883752)

巻号頁・発行日

vol.47, no.1-2, pp.29-48, 2014 (Released:2016-08-01)

参考文献数

47

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Living cells are deeply divided into two enormously divergent levels of complexity: prokaryotic and eukaryotic. Eukaryotes are thought to have developed from prokaryotic predecessors; however the large differences in their cellular structures results in equally large questions of how the process might have occurred. In 2012, in the deep-sea off the coast of Japan, we discovered a unique microorganism appearing to have cellular features intermediate between prokaryotes and eukaryotes. The organism, the Myojin parakaryote (tentatively named by Yamaguchi et al., 2012), was two orders of magnitude larger than a typical bacterium and had a large “nucleoid”, consisting of naked DNA fibers, surrounded by a single layered “nucleoid membrane”, and bacteria-like “endosymbionts”, but it lacked mitochondria. This organism exemplifies a potential evolutionary path between prokaryotes and eukaryotes, and strongly supports the endosymbiotic theory for the origin of mitochondria and the karyogenetic hypothesis for the origin of the nucleus. In this review, we describe how the Myojin parakaryote was discovered, the features of this organism, the significance of the discovery, and perspectives on future research.