Biomedical subjects

H D Görtz

Publications and source records attributed to H D Görtz.

12 recordsLinked to original sources

PubMed2001

Intracellular bacteria in ciliates.

Ciliates are frequently colonized by other micro-organisms. The large size of ciliate cells offers habitats for hundreds to thousands of bacteria in different compartments, such as cytoplasm, nuclei and even perinuclear spaces. Size, phagocytic feeding habit and other features appear to be favorable pre-adaptations of ciliates for symbiosis with bacteria. Certain intracellular bacteria are permanent symbionts that are not infectious, whereas others are highly infectious. Both types show specific adaptations. With their wide spectrum of phylogenetic positions, intracellular bacteria in ciliates show relationships to different taxa of free-living bacteria and even archaea. Certain symbionts may be deleterious for their host ciliates, whereas others may provide a selective advantage under appropriate conditions or even be essential for the host cells. Depending on the nature of a symbiont, its prevalence in a host population may be low or high. Symbionts that express a killer toxin affecting non-infected ciliates achieve high infection rates in a host population. whereas certain infectious bacteria may only show a low prevalence.

Adaptation, Physiological↗

PubMed1999

Intra- and intercellular communication systems in ciliates.

Intracellular signaling and cell-cell interactions are basic features of living organisms. Ciliated protozoa show complex mechanisms of intracellular signaling, as is demonstrated for the phagosomal pathway. Although unicellular, ciliates also communicate with other cells, for example, with invading or symbiotic micro-organisms, some of which are dwelling in the nuclei. In predator-prey interactions chemical signals (kairomones) released by certain predators induce defensive morphological or behavioral changes in the prey ciliates. In intercellular communication sensu strictu ciliate cells communicate with each other, for example, in sexual propagation. A variety of sexual signals have been found to function in preconjugant interaction. Many phenomena of cellular communication in ciliates appear to be similar to those found in multicellular organisms.

Amino Acid Sequence↗

PubMed1998

Intracellular bacteria in protozoa.

Intracellular bacteria in humans are typically detrimental, and such infections are regarded by the patients as accidental and abnormal. In protozoa it seems obvious that many bacteria have coevolved with their hosts and are well adapted to the intracellular way of life. Manifold interactions between hosts and intracellular bacteria are found, and examples of antibacterial resistance of unknown mechanisms are observed. The wide diversity of intracellular bacteria in protozoa has become particularly obvious since they have begun to be classified by molecular techniques. Some of the bacteria are closely related to pathogens; others are responsible for the production of toxins.

Animals↗

PubMed1993

Occurrence of fragmented 16S rRNA in an obligate bacterial endosymbiont of Paramecium caudatum.

The phylogenetic position of Caedibacter caryophila, a so far noncultured killer symbiont of Paramecium caudatum, was elucidated by comparative sequence analysis of in vitro amplified 16S rRNA genes (rDNA). C. caryophila is a member of the alpha subclass of the Proteobacteria phylum. Within this subclass C. caryophila is moderately related to Holospora obtusa, which is another obligate endosymbiont of Paramecium caudatum, and to Rickettsia. A 16S rRNA targeted specific hybridization probe was designed and used for in situ detection of C. caryophila within its host cell. Comparison of the 16S rDNA primary structure of C. caryophila with homologous sequences from other bacteria revealed an unusual insertion of 194 base pairs within the 5'-terminal part of the corresponding gene. The intervening sequence is not present in mature 16S rRNA of C. caryophila. It was demonstrated that C. caryophila contained fragmented 16S rRNA.

Animals↗

PubMed1991

Identification in situ and phylogeny of uncultured bacterial endosymbionts.

The use of Koch's technique to isolate bacteria in pure cultures has enabled thousands of bacterial species to be characterized. But for the many microorganisms that have never been cultivated, DNA amplification in vitro using the polymerase chain reaction is now making their genes accessible. Here we use this technique to study bacteria of the genus Holospora, which live in ciliates and whose phylogenetic relationship has remained unknown because they are impossible to cultivate. Species of Holospora are highly infectious and live in the nuclei of their specific host cells: H. elegans and H. undulata infect micronuclei of Paramecium caudatum, whereas H. obtusa infects the macronucleus in other strains of the same host species; Holospora species have a common developmental cycle. We have amplified, cloned and sequenced gene fragments encoding ribosomal RNA of H. obtusa. The phylogenetic position of H. obtusa in the alpha group of Proteobacteria was determined by 16S rRNA sequence analysis. The sequences were then used to design species- as well as genus-specific rRNA hybridization probes, which enabled us to detect and differentiate individual cells of the endosymbionts in situ. The large amount of rRNA in the cells indicates a high physiological activity of the endosymbionts in the host nuclei.

Animals↗

PubMed1991

Identification and localization of major stage-specific polypeptides of infectious Holospora obtusa with monoclonal antibodies.

With the help of monoclonal antibodies (MAbs) we investigated the occurrence of six polypeptides throughout parts of the life cycle of Holospora obtusa, a bacterium infecting the macronucleus of the ciliate Paramecium caudatum. The polypeptides of interest formed major bands in the protein pattern of the infectious form (IF) of H. obtusa. All MAbs used recognized individual polypeptide bands of the IF proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three polypeptides were also detected in the reproductive form in trace amounts. Two-dimensional electrophoresis revealed that the 33,000-, 28,000-, and 14,000-Mr polypeptides wre acidic and exhibited multiple isoelectric points under native conditions. Four polypeptides (Mrs of 50,000, 33,000, 28,000, and 20,000) were no longer detected or became drastically reduced within the first 30 min of invasion. Concomitantly, a loss of electron-dense periplasmic material occurred, which is typical for invading IFs (H.-D. Görtz and M. Wiemann, J. Protistol. 24:101-109, 1989). In an attempt to clarify the subcellular localization of the six polypeptides, we performed chloroform extraction studies and identified four of the released polypeptides with MAbs. A 14,000-Mr polypeptide was immunocytochemically localized in the periplasm of the IF. The results showed that the six major polypeptides of the IF were stage specific or stage specifically enriched and are likely to contribute to the electron-dense periplasmic material of the IF.

Animals↗

PubMed1990

Changes in fine structure and polypeptide pattern during development of Holospora obtusa, a bacterium infecting the macronucleus of Paramecium caudatum.

The development of the bacterium Holospora obtusa, which infects the macronucleus of Paramecium caudatum, was investigated in the course of a new infection from the infectious form into the reproductive form and vice versa. In parallel with a complete structural reorganization of the bacterium, the protein pattern changed gradually in this development. During the differentiation of the infectious form into the reproductive form, the voluminous periplasm was gradually reduced and the cytoplasm expanded, until the entire bacterium was filled by the cytoplasm. At this stage the long cell divided into five to seven short cells and thereby established the reproductive form, the main stage of the bacterium being maintained and multiplying in the host nucleus. In parallel with the reduction of the periplasm, some of the main proteins of the infectious form gradually disappeared in the electrophoresis pattern; some proteins disappeared earlier than others. Simultaneously, other proteins appeared and gradually became more prominent in the pattern of the developing reproductive form. In the reverse development, when the reproductive form differentiated into the infectious form, the bacterium grew longer, the cytoplasm was condensed, and electron-dense material was deposited in the extending periplasmic space. In parallel with this morphological development, the polypeptide pattern reverted to that of the infectious form.

Animals↗

PubMed1988

Characterization of Caedibacter endonucleobionts from the macronucleus of Paramecium caudatum and the identification of a mutant with blocked R-body synthesis.

Cytology, DNA and host-symbiont relationships of x-like endosymbionts from Paramecium caudatum are described. The symbionts (Caedibacter caryophila, sp. nov.) live in the macronuclei of their hosts. They confer the killer trait upon their hosts and appear well adapted to their endonucleobiotic way of life. R bodies (proteinaceous ribbons associated with killing) are produced, but differ significantly from any of the four R-body classes previously described. C. caryophila and their R bodies were isolated. DNA was extracted from purified symbionts and used to demonstrate that one P. caudatum line harbors a natural mutant which is deficient in R-body production. Melting studies indicate a GC content of 34.6%. No sequence homology between the C. caryophila DNA and the coding sequence for type 51 R-body production was observed. C. caryophila is parasitic, causing the death of its hosts in starving cultures.

Animals↗

PubMed1983

Infection of macronuclear anlagen of Paramecium caudatum with the macronucleus-specific symbiont Holospora obtusa.

The gram-negative bacterium Holospora obtusa is an endonuclear symbiont of Paramecium caudatum, which is incorporated into the host cells via the food vacuoles and infects their macronucleus exclusively, but never the micronucleus. Since these two kinds of nuclei originate from a fertilization nucleus, it is assumed that the macronucleus acquires a property necessary for it to be recognized by the bacterium at a certain time during the nuclear differentiation process. We found that this property is acquired by four of the eight postzygotic nuclei as soon as the four nuclei differentiate morphologically into the macronuclear anlagen.

Animals↗

PubMed1983

Acid phosphatase associated with discharging secretory vesicles (mucocysts) of Tetrahymena thermophila.

The localization of acid phosphatase in discharging mucocysts of Tetrahymena thermophila is reported. Electron dense, lead phosphate enzyme reaction product is found associated with the fibrillar meshwork of secreting mucocysts and in cytoplasmic vesicles (e.g. lysosomes). Resting mucocysts, containing highly condensed contents, exhibit no label. The specificity of the stain was controlled by reaction media without exogenous substrate and reaction media containing the inhibitor sodium fluoride. No lead phosphate deposits were found in these controls. Secreting organelle contents have no preferential affinity to lead phosphate as shown by tests with reaction medium lacking substrate and subsequent incubation in phosphate containing medium.

Acid Phosphatase↗

PubMed1983

Conjugation and meiosis of Paramecium caudatum infected with the micronucleus-specific bacterium Holospora elegans.

Cells of two complementary mating types of Paramecium caudatum, syngen 3, are infected with the micronucleus-specific bacterium Holospora elegans. Cells with bacteria in their micronuclei show the mating reaction with agglutination and pair formation. All the stages of meiosis in this species are observed and pronuclei are formed. During the pregamic divisions the bacteria are distributed to the division products, but many of the bacteria remain within the separation spindles, later being released into the medium. Therefore, the pronuclei contain only a few or no bacteria. In a test of the viability of exconjugant clones CNR-mutant (a behavioral mutant) and wild type cells, both infected with H. elegans, are crossed. The survival of exconjugants is very low (10.6% compared to 57.3% in the control). After conjugation only parental types are found indicating the occurrence of macronuclear regeneration after conjugation. The same result is obtained with cells which had contained bacteria but were cured by means of antibiotics. It is concluded that infected micronuclei have become genetically defective and did not give rise of new functional macronuclei. Therefore, H. elegans-bearing paramecia are genetically dead, which shows the parasitic nature of the bacterium H. elegans.

Animals↗

PubMed1982

Infections of Paramecium bursaria with bacteria and yeasts.

Infections of Paramecium bursaria with bacteria and yeasts are reported. Bacteria and yeasts multiply in the algae-free ciliate and are transmitted at various conditions as are symbiotic chlorellae. Like chlorellae, the bacteria and the yeast cells are situated in perisymbiont vacuoles. Both bacteria and yeasts maintain their capability for independent existence and can be grown on standard nutrient agar. Infection experiments show that aposymbiotic P. bursaria can be infected with Chlorella, bacteria and yeast. Chlorella-bearing P. bursaria cannot be infected with bacteria or yeast. Bacteria-bearing paramecia can be infected with Chlorella but not with yeast. Yeast-bearing paramecia can be infected with Chlorella but not with bacteria. Following infections with Chlorella the paramecia lose their bacteria or yeast symbionts. The bacteria found in P. bursaria probably belong to the genus Pseudomonas; the yeast has been identified as Rodutorula rubra.

Animals↗