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72 • "PROTIST—2016
Cryosol profiles by different processes of cryogenic mass-exchange. According to our results about half of protists communities in Cryosols have adaptive and protective mechanisms enabling long-term cryptobiosis in the inhospitable conditions of the arctic soils and permafrost. Fragments of the uppermost soil horizons that were cryoturbated, buried by solifluction and accumulated in the upper layer ofpermafrost appear to be the ecologycal niche in profiles of Turbic Cryosols that can significantly sustain viability of protists.
GENOME ANNOTATION OF ACRASIS KONA Sheikh Sanea, Fu Chengjie, Baldauf Sandra Department of Organismal Biology, Uppsala University, Sweden sanea.sheikh@ebc.uu.se
Acrasids are single-celled amoebae that can undergo aggregative multicellularity in response to adverse environmental conditions, similar to the well-studied dictyostelid social amoebas. However, acrasids are unrelated to dictyostelids (supergroup Amoebozoa), being instead the only multicellular lineage in the eukaryotic supergroup Excavata. This makes Acrasis an interesting model system to study parallel evolution of social behavior in microbes as well as to explore the diversity of eukaryotes in general. We have sequenced the genome and transcriptome of Acrasis kona and are currently preparing transcriptomes from the four main stages of its life cycle. In initial work, we assembled the complete A. kona mitochondrial genome (mtDNA) and find that it is missing 14 protein genes present in the mtDNA of its closest sequenced relative, Naegleria gruberii. We further identified 11 of these protein genes in A. kona nuclear DNA and find that they carry mitochondrial important signals (transit peptides, Fu et al. 2014). We are now using RNAseq data and the N. gruberii genome in an annotation pipeline to create a fully annotated A. kona nuclear assembly. The results will be used to investigate parallel evolution of simple multicellularity, early steps in the evolution of eukaryotes and to aid in resolution of the eukaryote tree of life by breaking up some of the longer deep branches.
CHEMOTAXIS RESPONSE OF PHYTOPLAN-
KTON TO CILIATES
Shen Z.12, Vidyarathna N.K.1, Liu H.B.1
1 - Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong
2 - Institute of Hydrobiology, Jinan University, Guangzhou 510631, China
liuhb@ust.hk
Marine environment at the micro scale level is
heterogeneous in terms of nutrient distribution and many microbial species can actively exploit these nutrient patches. Exudates of microbes act as nutrient hotspots and also provide chemical cues to their prey or predators. In the present study we examined the chemotactic response of starved and/ or non-starved Dunaliella salina to the exudates of ciliate grazers (Euplotes vannus, Euplotes sp., and Diophrys oligothrix) by using two approaches; 1. Co-culturing oftwo species under different illumination conditions to evaluate the growth, ingestion and behavioural response of the phytoplankton and/ or ciliates and 2. Using microfluidics and image analyses to evaluate the response of D. salina to the exudates of ciliates and related nutrient media. D. salina showed different active swimming and an 'attack-like' behaviour towards ciliates under different illumination conditions, despite the high ciliate grazing rates on them. When exposed to the patches of ciliate exudates, f/2 growth medium, yeast extraction and ammonium solution, both starved and non-starved D. salina showed chemotactic accumulation on/around the exudate and nutrient patches. In both cases positive chemotaxis indices were found towards ciliate exudates suggesting that D. salina could actively uptake nutrients released by its ciliate grazers. This specific behavioural response however, could be costly to D. salina. We suggest that this behaviour could also serve as a defence mechanism thereby increasing the benefits for D. salina.
PELAGIC PROTISTS FEEDING ON PICO-CYANOBACTERIA AND THEIR CHLOROPHYLL CATABOLISMS
Shihongi A.1, Kinoshita Y.2, Ishikawa A.3, Tamiaki H.2, Kashiyama Y.1,2
1 - Fukui University of Technology
2 - Ritsumeikan University
3 - Mie University chiro@fukui-ut.ac.jp
Pico-phytoplanktons dominate the primary production in pelagic oligotrophic oceans. Because these settings cover roughly half areas of the Earth surface, thus relatively dilute inhabitances of pico-phytoplanktons actually represent a considerable proportion of the photosynthetic primary production on the Earth. Nonetheless, ecological/bioenergetic networks extended from these microbial phototrophs have been poorly understood due to insufficient knowledge on the prey-predator relationship, where the minute cells should evade grazing by filter-feeding zooplanktons. We have thus investigated on pelagic protists that potentially prey on picophytoplanktons based on
