The ecology of Paraphysomonas imperforata based on studies employing oligonucleotide probe identification in coastal water samples and enrichment cultures

The geographical distribution and seasonal abundance of the cosmopolitan heterotrophic flagellate Paraphysomonas imperforata in several coastal waters was examined using species-specific oligonucleotide hybridization probes which target small subunit ribosomal RNA. P. imperforata was found to occur in several coastal environments, but at very low abundances (typically ,50 cells ml 21 ). The seasonal abundance of P. imperforata examined at one sampling site remained consistently low and constituted no more than 1% of the total nanoplankton at any time during a 17-month sampling period. In contrast to the low abundances observed in natural water samples, P. imperforata frequently dominated heterotrophic enrichment cultures prepared from these same samples, comprising up to 98% of the total nanoplankton. Based on these findings, we conclude that P. imperforata is an opportunistic species capable of growing rapidly to high abundances when prey concentrations are high. Water and enrichment temperature as well as the temperature tolerance range of P. imperforata appear to have played a role in the seasonal differences observed in P. imperforata dominance. Experiments with enrichment cultures indicated that the absolute abundances of P. imperforata in the water samples and the activity of consumers of nanoplankton also influenced the degree to which P. imperforata dominated the heterotrophic nanoplankton assemblages of enrichment cultures. Seasonal changes in water temperature might also affect these latter factors, and, as a consequence, indirectly influence the ability of P. imperforata populations to dominate enrichments. Our results support the notion that enrichment cultivation of heterotrophic flagellates, and perhaps incubations in general, can select for species such as P. imperforata that may not be representative of nanoplanktonic protists that numerically dominate natural assemblages.

[1]  K. Schleifer,et al.  In situ identification of Legionellaceae using 16S rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy. , 1995, Microbiology.

[2]  N. Vørs.  Heterotrophic Amoebae, Flagellates and Heliozoa from the Tvärminne Area, Gulf of Finland, in 1988–1990 , 1992 .

[3]  J. C. Goldman,et al.  Nutrient cycling in a microflagellate food chain: I. Nitrogen dynamics. , 1985 .

[4]  E. Delong,et al.  Phylogenetic stains: ribosomal RNA-based probes for the identification of single cells. , 1989, Science.

[5]  E. Delong,et al.  Application of rRNA-based probes for observing marine nanoplanktonic protists , 1993, Applied and environmental microbiology.

[6]  I. Lucas,et al.  Two new marine species of Paraphysomonas , 1967, Journal of the Marine Biological Association of the United Kingdom.

[7]  G. B. Bouck.  The Biology of Free‐Living Heterotrophic Flagellates. , 1993 .

[8]  T. Fenchel.  The ecology of heterotrophic microflagellates , 1986 .

[9]  M. Landry,et al.  Discrimination between living and heat-killed prey by a marine zooflagellate, Paraphysomonas vestita (Stokes) , 1991 .

[10]  D. Caron.  Technique for Enumeration of Heterotrophic and Phototrophic Nanoplankton, Using Epifluorescence Microscopy, and Comparison with Other Procedures , 1983, Applied and environmental microbiology.

[11]  D. Caron,et al.  Nutrient cycling in a microflagellate food chain: III. Phosphorus dynamics , 1986 .

[12]  Francesc Peters,et al.  Effects of Temperature on Two Psychrophilic Ecotypes of a Heterotrophic Nanoflagellate, Paraphysomonas imperforata , 1992, Applied and environmental microbiology.

[13]  K. Schleifer,et al.  Phylogenetic identification and in situ detection of individual microbial cells without cultivation. , 1995, Microbiological reviews.

[14]  N. Vørs.  Marine heterotrophic amoebae, flagellates and heliozoa from Belize (Central America) and Tenerife (Canary Islands), with descriptions of new species, Luffisphaera bulbochaete N. Sp., L. longihastis N. Sp., L. turriformis N. Sp. and Paulinella intermedia N. Sp. , 1993 .

[15]  D Marie,et al.  Fluorescent in situ hybridization with rRNA-targeted oligonucleotide probes to identify small phytoplankton by flow cytometry , 1995, Applied and environmental microbiology.

[16]  D A Stahl,et al.  Fluorescent-oligonucleotide probing of whole cells for determinative, phylogenetic, and environmental studies in microbiology , 1990, Journal of bacteriology.

[17]  R. Amann,et al.  Combination of 16S rRNA-targeted oligonucleotide probes with flow cytometry for analyzing mixed microbial populations , 1990, Applied and environmental microbiology.

[18]  J. C. Goldman,et al.  Nutrient cycling in a microflagellate food chain : II. Population dynamics and carbon cycling. , 1985 .

[19]  T. Fenchel.  Ecology of heterotrophic microflagellates. I. Some important forms and their functional morphology , 1982 .

[20]  David J. Patterson,et al.  Some flagellates (Protista) from tropical marine sediments , 1990 .

[21]  J. G. Field,et al.  The Ecological Role of Water-Column Microbes in the Sea* , 1983 .

[22]  M. Sogin,et al.  Structural diversity of eukaryotic small subunit ribosomal RNAs. Evolutionary implications. , 1987, Annals of the New York Academy of Sciences.

[23]  D. Hibberd,et al.  Ultrastructure and taxonomy of Paraphysomonas (Chrysophyceae) and related genera 2 , 1983 .

[24]  E. Delong,et al.  Development and field application of a quantitative method for examining natural assemblages of protists with oligonucleotide probes , 1996, Applied and environmental microbiology.

[25]  Ee Lin Lim.  Molecular Identification of Nanoplanktonic Protists Based on Small Subunit Ribosomal RNA Gene Sequences for Ecological Studies 1 , 1996, The Journal of eukaryotic microbiology.

[26]  J. C. Goldman,et al.  Effect of Temperature on Growth, Respiration, and Nutrient Regeneration by an Omnivorous Microflagellate , 1986, Applied and environmental microbiology.

[27]  G J Olsen,et al.  Phylogenetic group-specific oligodeoxynucleotide probes for identification of single microbial cells , 1988, Journal of bacteriology.

[28]  J. Sieburth.  Protozoan Bacterivory in Pelagic Marine Waters , 1984 .

[29]  J. C. Goldman,et al.  Experimental studies on an omnivorous microflagellate: implications for grazing and nutrient regeneration in the marine microbial food chain , 1985 .