Oxygen toxicity, respiration and behavioural responses to oxygen in free-living anaerobic ciliates

Fenchel, Tom; Finlay, Bland J.

doi:10.1099/00221287-136-10-1953

Cited by 46 publications

(28 citation statements)

References 20 publications

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“…Table 1 also compares the physiological characteristics of the microaerophilic species studied with respect to oxidative and nitrosative stress. Fenchel & Finlay (1990); Biagini et al (1997b) ND, Not determined. *ROS, reactive oxygen species.…”

Section: Discussionmentioning

confidence: 99%

The plasma membrane of microaerophilic protists: oxidative and nitrosative stress

et al. 2004

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The trans-plasma-membrane electrochemical potential of microaerophilic protists was monitored by the use of voltage-sensitive charged lipophilic fluorophores; of the many available probes, the anionic oxonol dye bis(1,3-dibarbituric acid)-trimethine oxonol [DiBAC4(3)] is an example of one which has been successfully employed using fluorescence microscopy, confocal laser-scanning microscopy and flow cytometry. Several microaerophilic protists have been investigated with this dye; these were Giardia intestinalis, Trichomonas vaginalis, Tritrichomonas foetus, Hexamita inflata and Mastigamoeba punctachora. Under conditions where they exhibit normal vitality, these organisms exclude DiBAC4(3) by virtue of their maintenance of a plasma-membrane potential (negative inside). Uptake of the fluorophore is indicative of disturbance to this membrane (i.e. by inhibition of pump/leak balance, blockage of channels or generation of ionic leaks), and is indicative of metabolic perturbation or environmental stress. Here, it is shown that oxidative or nitrosative stress depolarizes the plasma membranes of the aforementioned O2-sensitive organisms and allows DiBAC4(3) influx. Oxonol uptake thereby provides a sensitive and early indication of plasma-membrane perturbation by agents that may lead to cytotoxicity and eventually to cell death by necrotic or apoptotic pathways.

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Section: Discussionmentioning

confidence: 99%

The plasma membrane of microaerophilic protists: oxidative and nitrosative stress

et al. 2004

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“…The credibility of this conjecture derives from numerous examples of modern symbiotic relationships with an oxygenscavenging function assigned to one of the partners (60,61,62). Roughly two billion years ago, the oxygen tension increased from less than 1.5% to greater than 15% of present levels (88).…”

Section: Ox-tox Modelmentioning

confidence: 99%

“…These activities might not have been so widespread two billion years ago. Indeed, even some modern cells are killed or debilitated by exposure to less than ambient atmospheric oxygen tensions (60,61,62).…”

Section: Ox-tox Modelmentioning

confidence: 99%

Origin and Evolution of the Mitochondrial Proteome

Kurland

Andersson

2000

Microbiol Mol Biol Rev

362

272

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SUMMARY The endosymbiotic theory for the origin of mitochondria requires substantial modification. The three identifiable ancestral sources to the proteome of mitochondria are proteins descended from the ancestral α-proteobacteria symbiont, proteins with no homology to bacterial orthologs, and diverse proteins with bacterial affinities not derived from α-proteobacteria. Random mutations in the form of deletions large and small seem to have eliminated nonessential genes from the endosymbiont-mitochondrial genome lineages. This process, together with the transfer of genes from the endosymbiont-mitochondrial genome to nuclei, has led to a marked reduction in the size of mitochondrial genomes. All proteins of bacterial descent that are encoded by nuclear genes were probably transferred by the same mechanism, involving the disintegration of mitochondria or bacteria by the intracellular membranous vacuoles of cells to release nucleic acid fragments that transform the nuclear genome. This ongoing process has intermittently introduced bacterial genes to nuclear genomes. The genomes of the last common ancestor of all organisms, in particular of mitochondria, encoded cytochrome oxidase homologues. There are no phylogenetic indications either in the mitochondrial proteome or in the nuclear genomes that the initial or subsequent function of the ancestor to the mitochondria was anaerobic. In contrast, there are indications that relatively advanced eukaryotes adapted to anaerobiosis by dismantling their mitochondria and refitting them as hydrogenosomes. Accordingly, a continuous history of aerobic respiration seems to have been the fate of most mitochondrial lineages. The initial phases of this history may have involved aerobic respiration by the symbiont functioning as a scavenger of toxic oxygen. The transition to mitochondria capable of active ATP export to the host cell seems to have required recruitment of eukaryotic ATP transport proteins from the nucleus. The identity of the ancestral host of the α-proteobacterial endosymbiont is unclear, but there is no indication that it was an autotroph. There are no indications of a specific α-proteobacterial origin to genes for glycolysis. In the absence of data to the contrary, it is assumed that the ancestral host cell was a heterotroph.

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“…give evidence that, like in oxic waters, ciliates as grazers of microbial food web organisms are active at the oxic/anoxic interface and probably below. Several spe-cies of the genus Metopus are able to live in anoxic environments (Fenchel & Finlay 1990).…”

mentioning

confidence: 99%

Phototrophic and heterotrophic pico- and nanoplankton in anoxic depths of the central Baltic Sea

Detmer¹,

Giesenhagen²,

Trenkel³

et al. 1993

Mar. Ecol. Prog. Ser.

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An unexpected increase of phototrophic and heterotrophic pico-and nanoplankton under anoxic conditions was encountered in the central Baltic Sea below 120 m depth in August 1991 and 135 m depth in July 1992, respectively. Cell abundances in anoxic layers were up to 10 times higher for chroococcoid cyanobacteria, 6 to 8 times for phototrophic nanoflagellates and 3 to 4 times for bacteria, as compared to the overlaying aphotic oxic layers. A characteristic ciliate community occurred at the oxic/anoxic interface. Phototrophic organisms of anoxic depths were capable of productivity when reoxygenated and returned into the light. Considerable grazing on bacteria (0.41 to 0.65 d ' ) and chroococcoid cyanobacteria (1.19 to 1.29d-') was revealed by serial dilution experiments. Cyanobacteria showed gross growth rates of 0.85 to 1.33 d-' under aphotic/anoxic conditions. The origin of deep-water phototrophic pico-and nanoplankton and the existence of a permanent anaerobic microbial food web are discussed.

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Oxygen toxicity, respiration and behavioural responses to oxygen in free-living anaerobic ciliates

Cited by 46 publications

References 20 publications

The plasma membrane of microaerophilic protists: oxidative and nitrosative stress

The plasma membrane of microaerophilic protists: oxidative and nitrosative stress

Origin and Evolution of the Mitochondrial Proteome

Phototrophic and heterotrophic pico- and nanoplankton in anoxic depths of the central Baltic Sea

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