Helical Filaments Produced by a Mycoplasma-Like Organism Associated with Corn Stunt Disease

Abstract

Mycoplasma-like bodies with helical filaments were seen by phase contrast microscopy in juice expressed from tissues of plants infected with corn stunt agent. Each filament is bounded by a "unit membrane" and no cell wall, sheath, envelope, or second membrane has yet been discerned by electron microscopy. The association of these filaments with development of disease, their occurrence in phloem cells as seen by both freeze-etching and thin-section electron microscopy, the diagnosis of infection based on their presence in plants without symptoms, and their absence in noninfected corn are consistent with the hypothesis that these unusual filaments are formed by the mycoplasma-like organism presumed to be the corn stunt agent.

Cryptic plasmid pSKU146 from the wall-less plant pathogen Spiroplasma kunkelii encodes an adhesin and components of a type IV translocation-related conjugation system

“…In their descent from the Gram-positive, low G + C BacillusClostridium group of walled bacteria, spiroplasmas underwent massive evolutionary genome reduction, while acquiring capabilities for arthropod parasitism, and in some cases plant pathogenicity. First discovered in association with plant disease (Davis and Worley, 1973;Davis et al, 1972), spiroplasmas comprise broadly diverse species, most of which parasitize a variety of insects or ticks (Gasparich, 2002). As in other bacteria, plasmids presumably have played key roles in spiroplasma evolution, and contributed to the diversity of Spiroplasma species, through horizontal exchange of genes encoding virulence factors, niche adaptation factors, and factors conferring competitive advantages on the spiroplasma cell.…”

“…Spiroplasma kunkelii is the causative agent of corn stunt disease, a major factor limiting maize production in the Americas (Davis and Worley, 1973;Davis et al, 1972;Whitcomb and Williamson, 1975). This spiroplasma is transmitted between maize plants exclusively by phloem-feeding leafhopper insects, in which it multiplies.…”

The in vivo Three-dimensional Form of a Plant Mycoplasma-like Organism by the Analysis of Serial Ultrathin Sections

“…More recently, the use of similar or more sophisticated techniques has generally confirmed these early studies despite some controversy over the manner of reproduction and the significance of the numerous biological and physical factors which are known to affect form (Freundt, 1960(Freundt, , 1969Anderson, 1969 ;Boatman & Kenny, 197 1 ;Bernstein-Ziv, 197 1 ; Lemcke, 1972;Boatman, 1973a;Robertson et a/., 1975a). Since 1972 (Davis et al, 1972) helical prokaryote mollicutes have been recognized and this morphology is now regarded as one of the characteristics of the so far monotypic genus Spiroplasma (Saglio et al, 1973).…”

Spiroplasma – an emerging arthropod-borne pathogen?

“…1). Davis identified these unusual microbes as the cause of the studied disease [1,2] and his new term was widely accepted as the name of the new genus. Nowadays, spiroplasmas are classified within the class Mollicutes (comprising the Spiroplasma, Mycoplasma and Acholeplasma genera) which is related to Gram-positive bacteria, and have evolved by regressive evolution and genome reduction, from Clostridia to produce one of the smallest and simplest freeliving and self-replicating cells [3,4].…”