Nutrition and Growth of Protozoa

Hall, R. P.

doi:10.1016/b978-0-08-011846-8.50008-6

Cited by 14 publications

(3 citation statements)

References 457 publications

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“…[ 25 , 44 ]) highlighted that, in addition to phagotrophy, O. marina displayed a "plant-like" biochemistry including the ability to synthesise the full complement of amino-acids from ammonium or other simple nitrogen sources. While amino acid biosynthesis capability in heterotophic protists is exceptionally diverse, an absolute requirement for several amino acids is typical [ 45 ]. A broad range of transcripts indentified in this study were associated with amino acid metabolism and biosynthesis; based on the KEGG databases [ 36 ], 18 of the 22 amino acid biosynthesis pathways were represented by 100 454 contigs.…”

Section: Discussionmentioning

confidence: 99%

The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

et al. 2011

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BackgroundThe heterotrophic dinoflagellate Oxyrrhis marina is increasingly studied in experimental, ecological and evolutionary contexts. Its basal phylogenetic position within the dinoflagellates make O. marina useful for understanding the origin of numerous unusual features of the dinoflagellate lineage; its broad distribution has lent O. marina to the study of protist biogeography; and nutritive flexibility and eurytopy have made it a common lab rat for the investigation of physiological responses of marine heterotrophic flagellates. Nevertheless, genome-scale resources for O. marina are scarce. Here we present a 454-based transcriptome survey for this organism. In addition, we assess sequence read abundance, as a proxy for gene expression, in response to salinity, an environmental factor potentially important in determining O. marina spatial distributions.ResultsSequencing generated ~57 Mbp of data which assembled into 7, 398 contigs. Approximately 24% of contigs were nominally identified by BLAST. A further clustering of contigs (at ≥ 90% identity) revealed 164 transcript variant clusters, the largest of which (Phosphoribosylaminoimidazole-succinocarboxamide synthase) was composed of 28 variants displaying predominately synonymous variation. In a genomic context, a sample of 5 different genes were demonstrated to occur as tandem repeats, separated by short (~200-340 bp) inter-genic regions. For HSP90 several intergenic variants were detected suggesting a potentially complex genomic arrangement. In response to salinity, analysis of 454 read abundance highlighted 9 and 20 genes over or under expressed at 50 PSU, respectively. However, 454 read abundance and subsequent qPCR validation did not correlate well - suggesting that measures of gene expression via ad hoc analysis of sequence read abundance require careful interpretation.ConclusionHere we indicate that tandem gene arrangements and the occurrence of multiple transcribed gene variants are common and indicate potentially complex genomic arrangements in O. marina. Comparison of the reported data set with existing O. marina and other dinoflagellates ESTs indicates little sequence overlap likely as a result of the relatively limited extent of genome scale sequence data currently available for the dinoflagellates. This is one of the first 454-based transcriptome surveys of an ancestral dinoflagellate taxon and will undoubtedly prove useful for future comparative studies aimed at reconstructing the origin of novel features of the dinoflagellates.

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Section: Discussionmentioning

confidence: 99%

The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

et al. 2011

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“…Freshwater protozoan cytoplasmic osmolalities are 110 to 117 mOsm liter-1, whereas their environment is usually 0 to 6 mOsm liter-' (51). As a result, protozoans continually pump water out via contractile vacuoles to compensate for osmotic water gain (25); low pH increases protozoan cell membrane permeability (19,23,31) and, therefore, raises the energetic cost of iono-osmoregulation for protozoa in acidified systems. Given all of the data, we can hypothesize that under acid stress in disturbed lake sediments (pH c 5), higher maintenance costs probably cause reduced community growth rates (despite equal or greater grazing), resulting in the observed lower abundance at the most acid site.…”

Section: Resultsmentioning

confidence: 99%

Impact of Water Column Acidification on Protozoan Bacterivory at the Lake Sediment-Water Interface

Tremaine

Mills

1991

Appl Environ Microbiol

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Although the impact of acidification on planktonic grazer food webs has been extensively studied, little is known about microbial food webs either in the water column or in the sediments. Protozoon-bacterium interactions were investigated in a chronically acidified (acid mine drainage) portion of a lake in Virginia. We determined the distribution, abundance, apparent specific grazing rate, and growth rate of protozoa over a pH range of 3.6 to 6.5. Protozoan abundance was lower at the most acidified site, while abundance, in general, was high compared with other systems. Specific grazing rates were uncorrelated with pH and ranged between 0.02 and 0.23 h-1, values similar to those in unacidified systems. The protozoan community from an acidified station was not better adapted (P = 0.95) to low-pH conditions than a community from an unacidified site (multivariate analysis of variance on growth rates for each community incubated at pHs 4, 5, and 6). Both communities had significantly lower (P < 0.05) growth rates at pHs 4 and 5 than at pH 6. Reduced protozoan growth rates coupled with high grazing rates and relatively higher bacterial yields (ratio of bacterial-protozoan standing stock) at low pH indicate reduced net protozoan growth efficiency and a metabolic cost of acidification to the protozoan community. However, the presence of an abundant, neutrophilic protozoan community and high bacterial grazing rates indicates that acidification of Lake Anna has not inhibited the bacterium-protozoon link of the sediment microbial food web.

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“…The qualitative study of Amoebian endocytosis has been equally possible by following up either the intake of natural food, or of artificial dissolved material or suspended granules (Hall 1967). Intake of natural food, e.g.…”

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confidence: 99%

A new method for the quantitative determination of phagocytosis in Amoeba. Effect of histamine on the phagocytotic capacity of Amoeba proteus.

et al. 1984

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Nutrition and Growth of Protozoa

Cited by 14 publications

References 457 publications

The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

The transcriptome of the novel dinoflagellate Oxyrrhis marina (Alveolata: Dinophyceae): response to salinity examined by 454 sequencing

Impact of Water Column Acidification on Protozoan Bacterivory at the Lake Sediment-Water Interface

A new method for the quantitative determination of phagocytosis in Amoeba. Effect of histamine on the phagocytotic capacity of Amoeba proteus.

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