Grazing and growth of the heterotrophic flagellate Diphylleia rotans on the cyanobacterium Microcystis aeruginosa

Abstract

) by D. rotans were observed when they were fed the most toxic of the 5 Microcystis strains, M. aeruginosa NIER-10001. These results suggest that D. rotans has a high tolerance to M. aeruginosa and may undergo microcystin-mediated growth.KEY WORDS: Algivores · Heterotrophic flagellates · Diphylleia rotans · Microcystis spp. · Microcystin-mediated growth · Ingestion Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 45: [163][164][165][166][167][168][169][170] 2006 examined the ecophysiology of this flagellate on its prey using comparisons of grazing behavior on toxic and non-toxic Microcystis strains, along with other algal strains, which represent different food types and qualities. MATERIALS AND METHODSIsolation and culture of the heterotrophic flagellate. Furuike Pond (33°49' 21'' N, 132°48' 04'' E; altitude 40 m) is an impoundment located in Sancho, Matsuyama City, Ehime Prefecture, Japan. It has a surface area of 7400 m 2 and a maximum depth of 1.5 m. The pond is hypereutrophic due to anthropogenic loading from the watershed (Nakano et al. 2001b) and is heavily populated by cyanobacteria, such as Microcystis aeruginosa and M. wesenbergii, from early summer to fall each year (Manage et al. 1999).For isolation of a flagellate capable of grazing on Microcystis species, Microcystis aeruginosa NIES-298 was incubated in Cytophaga broth (CB) medium (MCC-NIES; www.nies.go.jp/biology/mcc/home_j.htm) and mixed with a pond water sample that had been filtered through a Nitex net (mesh size, 154 µm) for removal of larger zooplankton. This mixture was incubated at 25°C in the dark for 3 to 4 d. Flagellates were isolated using a Pasteur micropipette under a light microscope. We established a monoclonal flagellate culture using a repetitive serial isolation process consisting of enrichment, dilution and single cell isolation steps. The isolated flagellate was maintained using a commercial strain of Chlorella TM (Aquanet) as prey. Water was collected from the Pal'tang Reservoir, Korea, filtered through a Whatman GF/F filter and sterilized in an autoclave to yield filtered sterilized water (FSW). A quantity of Chlorella TM was suspended in the FSW, and the flagellate was inoculated into the Chlorella TM suspension. We maintained the flagellate strain by inoculating it weekly into new Chlorella TM suspensions. Incubations were performed at 25°C under a light intensity of 40 to 45 µE m -2 s -1 of cool white fluorescent light, with a 12:12 h light:dark photoperiod.To identify the flagellate, we used light and epifluorescence microscopy and 18S rDNA sequencing. Morphological observations, including the presence of 2 long apical and equal flagella inserting near the anterior end at the top of the ventral groove formed by the curving lateral margins of the cell, a cell dimension of 15 × 20 µm (subject to change during feeding), and feeding observations such as free movement or rotation during feeding via the ventral groove, identified the flagellate as Diphylleia rotans (Massart 1920...

Formation of large colonies: a defense mechanism of Microcystis aeruginosa under continuous grazing pressure by flagellate Ochromonas sp.

“…which have been reported in previous literature (Nishibe et al 2002;Kim et al 2006;Zhang et al 2008), Ochromonas sp. exhibited a strong grazing ability on unicellular M. aeruginosa and high growth rate after grazing activaty in our experiment.…”

Detection of Protozoan Hosts for Legionella pneumophila in Engineered Water Systems by Using a Biofilm Batch Test

“…vermiformis ratio suggest that testing of certain protozoa in coculture with L. pneumophila may lead to the identification of novel protozoan hosts for L. pneumophila ( Table 2). The involved organisms include (i) Diphylleia rotans (99.3% similarity), an algivorous heterotrophic flagellate that feeds on cyanobacteria (27); (ii) Echinamoeba thermarum (Ͼ96%), an extremely thermophilic protozoan (2) related to E. exundans, which is described as a host for L. pneumophila (15); and (iii) Neoparamoeba sp. (95.6% similarity) of the class Flabelinea with the genera Platyamoeba and Vannella, which are affiliated with Legionella spp.…”

Microcystins do not provide anti-herbivore defence against mixotrophic flagellates

“…In addition to mixotrophic flagellates such as Ochromonas, several heterotrophic flagellates have been reported to graze on Microcystis (Nishibe et al 2002, Park et al 2003, Kim et al 2006. Microcystins inhibit the eukaryotic protein phosphatases Types 1 and 2A (MacKintosh et al 1990) and are therefore toxic to most eukaryotes.…”

“…While most experiments investigating effects of toxic cyanobacteria on pelagic grazers have been done with metazoans, several protozoa are able to maintain high growth rates when feeding on cyanobacteria including Microcystis (Cole & Wynne 1974, Nishibe et al 2002, Kim et al 2006. Especially mixotrophic chrysophytes, such as Ochromonas spp.…”