Spiroplasma

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Spiroplasma
Spiroplasma kunkelii in cells of the phloem.

Spiroplasma kunkelii in cells of the phloem .

Systematics
Domain : Bacteria (bacteria)
Department : Tenerife
Class : Mollicutes
Order : Entomoplasmatales
Family : Spiroplasmataceae
Genre : Spiroplasma
Scientific name
Spiroplasm
Saglio et al. 1973

Spiroplasma ( Spiroplasma ) (derived from the two ancient Greek words σπεῖρα spéïra "spiral" and πλάσμα plásma "shaped") are a genus of small bacteria without a cell wall in the class of Mollicutes . All spiroplasms live parasitically in plants, arthropods or rodents or are saprophytic .

description

Species of the genus Spiroplasma have pleomorphic , rounded shapes and agile helical or branched, non-helical filaments. The diameter is approximately 120 nm and the length 2 to 4 μm or more. The genome size is 10 9 daltons . The GC content is between 25 and 26.4 mol%.

Pathogenicity

Of corn Dive diseased corn plant caused by Spiroplasma kunkelii

The transmission of phytopathogenic forms occurs through cicadas as vectors . The infection is limited to the phloem . The connection between spiroplasma and numerous plant diseases has been described. However, their pathogenicity in the sense of Koch's postulates has only been proven in a few cases .

In the vector, the spiroplasmas colonize numerous organs such as the digestive tract, the hemolymph , the salivary gland, the adipose tissue, the Malpighian vessels , the connective tissue, the nervous system and the ovaries . However, there are hardly any pathogenic influences. Reduced vitality, reduced survivability, hypertrophy of cells and cell nuclei and in some cases tissue lesions occur rarely .

In plants, however, the effect is often considerable. It occurred chlorosis on. The phloem changes degeneratively through severe disorganization. Affected cells change color and tend to hyperplasia . Necrotization and obliteration of phloem parts follow. In yellowed leaves, the palisade parenchyma recedes in favor of densely arranged sponge parenchyma, chloroplasts degenerate. Disturbances in the metabolism of the growth regulators lead to the lifting of growth inhibitions. For example, acropetal growth continues after flower formation or the induction of hibernation is prevented. Conversely, growth can also be inhibited, with consequences such as dwarfism, small leaves or small fruits.

When two types of Spiroplasma so-called was Male Killing observed. This means that the hosts no longer give birth to male offspring. This happens either through feminization of genetic males during sexual differentiation , through induction of parthenogenesis, or through death of the male offspring during embryogenesis . Male-killing has so far been associated almost exclusively with bacteria of the genus Wolbachia . Spiroplasma poulsonii , however, causes male killing in the fruit fly Drosophila willistoni and in two beetles, the two-point ladybird ( Adalia bipunctata ) and the Asian ladybird ( Harmonia axyridis ). Spiroplasma ixodetis has the same effect on ticks.

There is some controversial evidence of the role of spiroplasma in the etiology of transmissible spongiform encephalopathy (TSEs), particularly in the work of Frank Bastian. Other researchers have not been able to replicate these results , whereas the prion model for TSEs has now gained wide acceptance. A 2006 study also disproves the role of spiroplasma in hamster scrapie .

Internal system

The genus Spiroplasma has not yet been finally examined and the internal system is still subject to changes. A work from 2004 examines the 16S rDNA and tries to classify the genus. The following species seem to be reasonably certain:

literature

Unless otherwise stated, the information comes from this article:

  • Franz Nienhaus: Viruses, Mycoplasma and Rickettsia . Ulmer, Stuttgart 1985, ISBN 3-8001-2536-6 .

Individual evidence

  1. ^ SL O'Neill, AA Hoffmann, JH Werren: Influential Passengers . Oxford University Press, Oxford 1997 (English).
  2. ↑ J. Hinrich Graf von der Schulenburg, Tamsin MO Majerus, Chorduraa M. Dorzhu, Ilia A. Zakharov, Gregory DD Hurst, Michael EN Majerus: Evolution of male-killing Spiroplasma (Procaryotae: Mollicutes) inferred from ribosomal spacer sequences . In: Journal of General and Applied Microbiology . tape 46 , 2000, pp. 95-98 , PMID 12483596 (English).
  3. ^ RH Leach, WB Mathews, R. Will: Creutzfeldt-Jakob disease. "Failure to detect spiroplasmas by cultivation and serological tests" . In: Journal of Neurological Science . tape 59 , no. 3 , 1983, p. 349-353 , PMID 6348215 (English).
  4. ↑ I. Alexeeva, EJ Elliott, S. Rollins, GE Gasparich, J. Lazar, RG Rohwer: Absence of Spiro plasma or Other Bacterial 16S rRNA Genes in Brain Tissue of hamster with scrapie . In: Journal of Clinical Microbiology . tape 44 , no. 1 , 2006, p. 91-97 , doi : 10.1128 / JCM.44.1.91-97.2006 , PMID 16390954 (English).
  5. Jump up ↑ Gail E. Gasparich, Robert F. Whitcomb, Deborah Dodge, Frank E. French, John Glass, David L. Williamson: The genus Spiroplasma and its non-helical descendants: phylogenetic classification, correlation with phenotype and roots of the Mycoplasma mycoides clade . In: International Journal of Systematic and Evolutionary Microbiology . tape 54 , no. 3 , 2004, doi : 10.1099 / ijs.0.02688-0 (English).
  6. ↑ C. Saillard, JC Vignault, JM Bové, A. Raie, JG Tully, DL Williamson, RF Whitcomb: Spiroplasma phoeniceum sp. nov., a new plant-pathogenic species from Syria . In: International Journal of Systematic and Evolutionary Microbiology . tape 37 , no. 2 , 1987, pp. 106-115 , doi : 10.1099 / 00207713-37-2-106 .