Observations on the ultrastructure, mode of infectivity and host range of xenosomes

Soldo, A. T.; Brickson, S. A.

doi:10.1016/0040-8166(78)90049-6

Cited by 15 publications

(14 citation statements)

References 11 publications

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“…The symbionts, released from the host by gentle rupture, are capable of infecting homologous as well as heterologous strains of Parauronema spp. and at least one other ciliate of marine origin, Miamiensis auidus Ma (Soldo & Brickson, 1978). The particles are also capable of killing other ciliate strains, especially those of the genus Uronema (Soldo & Brickson, 1978).…”

Section: Introductionmentioning

confidence: 94%

“…Phase and electron microscopj. Aceto-orcein stained and unstained xenosome preparations were examined by phase microscopy as described previously (Soldo & Brickson, 1978). Contour lengths of D N A released from xenosomes were measured by the protein monolayer techniques of Kleinschmidt et al (1962).…”

Section: Methodsmentioning

confidence: 99%

“…and at least one other ciliate of marine origin, Miamiensis auidus Ma (Soldo & Brickson, 1978). The particles are also capable of killing other ciliate strains, especially those of the genus Uronema (Soldo & Brickson, 1978). Bacterium-like symbionts appear to be widespread in nature, particularly among the protozoa; it has been suggested that they may represent a new class of organisms that have adapted to an intracellular existence (Soldo, 1974).…”

Section: Introductionmentioning

confidence: 99%

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The Size and Structure of the DNA Genome of Symbiont Xenosome Particles in the Ciliate Parauronema acutum

1983

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Section: Introductionmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Size and Structure of the DNA Genome of Symbiont Xenosome Particles in the Ciliate Parauronema acutum

1983

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“…Xenosomes were then tested for killer activity against U. nigricans. The procedure for establishing infection in these organisms is detailed in Materials and Methods; assaying for the killer effect has been fully described (10). The results of a typical experiment are shown in Table 4.…”

Section: Resultsmentioning

confidence: 98%

Association of transformation of xenosomes from nonkiller to killer with extrachromosomal DNA

Soldo¹,

Brickson²,

Castiglione³

et al. 1986

J Bacteriol

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Extrachromosomal DNA in the form of covalently closed circular DNA molecules was isolated from killer and nonkiller xenosomes, bacterial endosymbionts of the marine protozoan Parauronema acutum. Restriction endonuclease digests of these molecules derived from 12 isolates revealed consistent, readily identifiable, differences in the pattern of fragments of the killer as compared with those present in the nonkiller. Transformation of the nonkiller to killer by infection is also accompanied by a change from the nonkiller to killer pattern. Based on analysis of fragments resulting from restriction endonuclease digests, two circular duplex DNA molecules, each 63 kilobase pairs (kbp) in length, were identified in the 263-20 nonkiller stock and mapped. The maps revealed that each possesses a single BamHI site and multiple Bgll, BstIIE, PstI, and Sall sites. A distinguishing feature of these maps is that the two molecules share a region about 17 kbp in length in which multiple restriction sites are in register with each other. Allowing for a 0.5-kbp insertion or deletion and the introduction or removal of only a few restriction sites, an additional stretch extending approximately 31 kbp beyond this sequence could also be considered to be homologous. The structure of the killer plasmid appears to be more complex, and we have been unable, as yet, to construct physical maps for this DNA. We postulate that the killer plasmid DNA is composed of three, perhaps four, circular 63-kbp duplexes, at least one which contains a single BamHI site and another which contains two BamHI sites. The remaining molecules may represent copies of either or both of the other two, modified to contain additional restriction sites. Transformation from the nonkiller to the killer is visualized as the insertion of restriction sites at various points along parent nonkiller plasmid DNA molecules. The mechanism by which these sites are introduced is unknown.Several stocks of the marine protozoan Paraiuronema acutum contain intracytoplasmic symbiotic bacteria which grow and divide in synchronism with the host (13). The symbionts, which we have termed xenosomes, sensu strictu, are obligate parasites and cannot be cultured outside the protozoan. Xenosomes released from the cytoplasm by mechanical rupture of the host cell are capable of infecting homologous and heterologous strains of P. acutuem as well as one other marine protozoan, Miamiensis aliidus Ma. Xenosomes from some stocks (killers) are capable of killing certain marine protozoa of the genus Uronema as evidenced by exposure of these organisms to breis of symbiont-bearing P. acutum. We show here that xenosomes from other stocks of P. acutum (nonkillers) do not have this capacity. Significantly, P. acutum is insensitive to the toxin produced by the killer xenosomes. In an effort to determine the mechanism responsible for the killer effect and to establish its molecular basis, we previously examined chromosomal DNA derived from killer and nonkiller xenosomes by DNA-DNA hybridization (9). Whereas a h...

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“…PARAURONEMA acutum is a marine ciliate that was isolated in pure culture from the waters off the coast of Florida by Soldo (Soldo and Merin 1972, 1977) and grown in media employing an artificial sea water base. Some strains of P. acutum contain intracellular symbiotic bacteria‐like particles called xenosomes while other strains do not (Soldo 1978). While several of these marine ciliates, particularly Uronema , have been studied by electron microscopy (Kaneshiro and Holz 1976) and some physiological studies have been carried out on Miamiensis avidus and Uronema (Kaneshiro, Dunham, and Holz 1969; Thomson and Kaneshiro 1968), most studies have utilized P. acutum.…”

mentioning

confidence: 99%

Neutral Lipids, their Fatty Acids, and the Sterols of the Marine Ciliated Protozoon, Parauronema acutum

Sul¹,

Kaneshiro²,

Jayasimhulu³

et al. 2000

J Eukaryotic Microbiology

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The neutral lipids and their fatty acids and the sterol fractions of the marine ciliated protozoon, Parauronema acutum, were characterized. The neutral lipids consisted of triglycerides (30%), sterols (29%), free fatty acids (24%), steryl esters (9%), and diglycerides (8%) and small amounts of fatty alcohols. The fatty acid profiles of these lipids were very similar although quantitative differences were detected. Saturated fatty acids, primarily 14:0, 16:0, and 18:0 constituted 20-30% of the total. Unsaturated fatty acids containing one to three double bonds, primarily 18:1(9), 18:2 (9,12), 18:3 (9, 12, 15) and 20:3 (11, 14, 17), constituted 35-50% of the total. Highly unsaturated fatty acids, 18:4 (6, 9, 12, 15), 20:5 (5, 8, 11, 14, 17) and 22:6 (4, 7, 10, 16, 19), constituted 16-25% of the total. The fatty alcohols consisted of 14:0 (2%), 16:0 (66%), 18:0 (3%), 20:0 (8%), and 22:0 (21%). The sterols of Parauronema acutum consisted of cholesterol (53%), campesterol (32%), desmosterol (7%), and beta-sitosterol (8%).

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Observations on the ultrastructure, mode of infectivity and host range of xenosomes

Cited by 15 publications

References 11 publications

The Size and Structure of the DNA Genome of Symbiont Xenosome Particles in the Ciliate Parauronema acutum

The Size and Structure of the DNA Genome of Symbiont Xenosome Particles in the Ciliate Parauronema acutum

Association of transformation of xenosomes from nonkiller to killer with extrachromosomal DNA

Neutral Lipids, their Fatty Acids, and the Sterols of the Marine Ciliated Protozoon, Parauronema acutum

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