Ingestion of bacterial cells by the marine photosynthetic ciliate Myrionecta rubra

The digestion of heat-killed/stained Escherichia coli, Pseudomonas aeruginosa, Mesorhizobium sp. and Staphylococcus aureus was monitored within one food vacuole passage time in the ciliate Tetrahymena pyriformis using the pulse chase technique. Prey digestion proceeded in 2 phases: a digestive phase which lasted ~25 min and a defecation competent phase that showed limited digestive activity and was variable in length. The number of prey cells per food vacuole was found to influence the effectiveness of prey digestion. Complete digestion of the vacuole content was more likely to occur when the number of prey per vacuole averaged ~6 or less. At higher levels, only partial digestion of the vacuole content was recorded and some undigested prey were egested from the ciliate cell. A strain of Synechococcus sp. was never digested by this ciliate. Results suggest that bacteria do not necessarily require elaborate mechanisms to evade digestion by protozoa, as possessed by some pathogenic bacteria, but that inefficiency in the protozoan digestive system is all that is required to allow the release of undigested, apparently unharmed prey from their cells. Thus, models on carbon cycling which employ data on protistan ingestion rates alone should consider accounting for digestion efficiency and the subsequent effect of prey concentration, because prey carbon might not always be transferred efficiently to higher trophic levels.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Digestion of bacteria by the freshwater ciliate Tetrahymena pyriformis

Thurman¹,

Drinkall²,

Parry³

2010

“…No cultures were axenic. However, the contribution of bacterivory to the growth of M. rubra MR-MAL01 in terms of cell carbon (ingestion of 53 bacteria h -1 by 1 ciliate; Myung et al 2006) was estimated to be not significant. Further, our vast preliminary data indicated that our cryptomonad strains did not take up fluorescentlylabeled (i.e.…”

Section: Methodsmentioning

confidence: 99%

Growth responses of the marine photosynthetic ciliate Myrionecta rubra to different cryptomonad strains

Park¹,

Myung²,

Kim³

et al. 2007

Self Cite

“…The solid line and dashed line represent the maximum attainable abundance (MAA) and mean realised abundance (MRA) for marine environments, following Gasol (1994). HNF abundances fall below the MAA and no differentiation between bottom-up or top-down control can be made among the 3 water types (marine, plume and diluted) being occasionally mixotrophic (Gustafson et al 2000, Yih et al 2004, Myung et al 2006). For easier interpretation of the figures we included chlorophyll containing ciliates (mixotrophs + M. rubra) in Fig.…”

Section: Ciliate Abundance and Biomassmentioning

confidence: 99%

Community structure and trophic role of ciliates and heterotrophic nanoflagellates in Rhone River diluted mesoscale structures (NW Mediterranean Sea)

Christaki¹,

Courties²,

Joux³

et al. 2009

Studies of the Rhone River plume, and in particular its diluted mesoscale structures, have shown over recent years that low salinity water (LSW) is characterised by both high primary and high secondary productivity. Here we compare the structure and grazing activity of the hetorotrophic community (nanoflagellates, ciliates) in the LSW and the surrounding marine water (MW) of the northwestern Mediterranean Sea. Furthermore, we report on the temporal variability of these characteristics all along a Lagrangian track in the LSW. In May 2006, salinity of the LSW ranged from 31.41 to 38.25 down to a depth of 35 m, and surface chlorophyll a concentration reached 15.5 µg l -1 . The ciliate community structure was similar in both the LSW and the MW, characterised by the dominance of the mixotrophic ciliates Laboea strobila and Myrionecta rubra. The ciliate biomass was approximately 6 times greater in the LSW, compared to the MW. This difference was due to the mixotrophic ciliates, which were about 4-to 5-fold more important in terms of abundance and biomass in the LSW, while heterotrophic ciliates only increased by a maximum of 2-fold. M. rubra was the most abundant species reaching 4600 cells l -1 , while L. strobila was dominant in terms of biomass, accounting for 47% of total biomass in the LSW. Ciliates, in particular mixotrophs, were very active in the LSW where they grazed on phytoplankton at rates near their maximum clearance capacities. Mixotrophic and heterotrophic ciliates in LSW consumed about 50 and 10% of the nanophytoplankton stock per day, respectively. The mixotrophic ciliate L. strobila was found to be an efficient grazer of nanophytoplankton. In contrast to the ciliates, the biomass of heterotrophic nanoflagellates was similar in both the LSW and the MW; thus, we suggest that the transfer of bacterial biomass in the LSW towards higher trophic levels was moderate.