Rhodococcus fascians

Rhodococcus fascians ( and 1984 designated as Corynebacterium fascians ) is a gram-positive bacterium that causes plant galls. Rhodococcus fascians is the only plant pathogenic bacterium of the genus Rhodococcus, its host range includes both single and Dicotyledons. It usually remains epiphytic, but can also form endophytic populations. The plant galls, causing it by distribution of cytokinins, form an ideal living environment for the bacteria.

Physiology and morphology

Rhodococcus fascians is an aerobic, immovable, belonging to the order Actinomycetales bacterium that does not form spores. Colonies on an agar plate appear orange in color and may have a smooth or rough surface. The cells can have different shapes and form both branched hyphae than be cocci or rod -shaped.

System

Due to its GC content, the structure of the cell wall, the 5S and 16S rRNA sequences and the presence of mycolic tuberculostearic and Rhodococcus fascians is counted among the mycolsäurehaltigen genera among the Actinomycetales.

Virulence

Rodococcus fascians infected both gymnosperms and angiosperms. Affected plants depending on the age and strain of bacteria typical symptoms such as leaf deformation, witches broom and leaf galls. The leaf deformations caused by a widening of the parenchyma and growth of the vascular bundles, whereby the leaf surface is curved. All the symptoms that are caused by Rodococcus fascians, not based on a transformation of the cells, but the bacteria usually remain outside the cells and release the substances, which then diffuse into the surrounding cells. It also bacteria were observed in the intercellular spaces and in the cell wall itself.

On the control of virulence genes involved

The virulence of Rhodococcus fascians is mediated by genes on a plasmid. Strains lacking this plasmid, are not infectious.

History of Research

1927 Brown described Fasziationen into the root necks of Lathyrus odoratus, the scent - pea, and they suggested that this is to crown gall tumors that are caused by a weak or special form of Agrobacterium tumefaciens. Ten years later, Tilford was able to show that not Agrobacterium tumefaciens, but another bacterium is responsible for the Phytomonoas fascians was called. 1942, the unclear taxonomy was partially cleared, classified the plant pathogen as belonging to the actinomycetes and renamed Corynebacterium fascians, a name which had until 1984 inventory. Only then he could be classified as Rhodococcus due to chemical, genetic and phenotypic characteristics, a different genus within the actinomycetes. Later, it was clarified that it is not in elicited structures to crown gall tumors, but leaf galls caused by increased growth of shoot meristems.

Synonyms

The bacterium was formerly Rhodococcus fascians next as Rhodococcus luteus (ex Söhngen 1913) Nesterenko et al. 1982) referred. Since 1994, the two types in Rhodococcus fascians are summarized.

Evidence

• K. Goethals, D. Vereecke, M. Jaziri, M. Van Montagu, M. Holsters: Leafy gall formation by Rhodococcus fascians Annual Review of Phytopathology, 2001, 39:27-52.