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Updated: Sep 30, 2026
Optimized PCR-based Detection of Mycoplasma
Published on: June 20, 2011
Abstract:
Plants can be infected by two types of wall-less procaryotes, spiroplasmas and mycoplasma-like organisms (MLO), both located intracellularly in the phloem tissues of affected plants. Spiroplasmas have been cultured, characterized and shown to be true members of the class Mollicutes. MLO have not yet been cultured or characterized; they are thought to be mycoplasma-like on the basis of their ultrastructure as seen in situ, their sensitivity to tetracycline and resistance to penicillin. Mycoplasmas can also be found on the surface of plants. These extracellularly located organisms are members of the following genera: Spiroplasma. Mycoplasma and Acholeplasma. The presence of such surface mycoplasmas must not be overlooked when attempts to culture MLO from affected plants are undertaken. Sensitive serological techniques such as the enzyme-linked immunosorbent assay (ELISA) can successfully be used to compare the MLO located in the phloem of affected plants with those eventually cultured from the same plants. In California and Morocco periwinkles naturally infected with both Spiroplasma citri and MLO have been reported. With such doubly infected plants, the symptom expression has been that characteristic of the MLO disease (phyllody or stolbur), not that given by S. citri. Only S. citri can be cultured from such plants, but this does not indicate that S. citri is the causal agent of the disease expressed by the plant. In California many nonrutaceous plants have been found to be infected with S. citri. Stubborn affected citrus trees represent an important reservoir of S. citri, and Circulifer tenellus is an active leafhopper vector of S. citri. Hence, it is not surprising that in California MLO-infected fruit trees could also become infected with S. citri but it would not mean that S. citri is the causal agent of the disease. Criteria are discussed that are helpful in distinguishing between MLO infections and S. citri infections.
Insights
Plant infections by wall-less bacteria, spiroplasmas and mycoplasma-like organisms (MLO), can be challenging to distinguish. Differentiating between these pathogens is crucial for accurate diagnosis and disease management in plants.
Area of Science:
- Plant Pathology
- Microbiology
- Molecular Biology
Background:
- Plants are susceptible to intracellular infections by wall-less prokaryotes, specifically spiroplasmas and mycoplasma-like organisms (MLO), which reside in phloem tissues.
- Spiroplasmas are culturable and classified within the class Mollicutes, while MLO remain uncultured but share ultrastructural similarities and sensitivities to antibiotics with mycoplasmas.
- Extracellular plant-associated mycoplasmas (genera Spiroplasma, Mycoplasma, Acholeplasma) can complicate MLO isolation attempts.
Purpose of the Study:
- To differentiate between infections caused by Spiroplasma citri and Mycoplasma-like organisms (MLO) in plants.
- To highlight the importance of distinguishing between these pathogens for accurate diagnosis and understanding disease etiology.
- To discuss criteria for distinguishing MLO and S. citri infections in plants.
Main Methods:
- Ultrastructural analysis of intracellular pathogens.
- Antibiotic sensitivity testing (tetracycline and penicillin).
- Serological techniques, including enzyme-linked immunosorbent assay (ELISA), for comparing MLO.
- Culturing and characterization of Spiroplasma species.
Main Results:
- Spiroplasma citri can co-infect plants with MLO, but disease symptoms are typically characteristic of MLO infections (e.g., phyllody, stolbur).
- Culturing S. citri from doubly infected plants does not confirm it as the causal agent of the observed MLO-like disease symptoms.
- Citrus trees with "stubborn" disease are reservoirs for S. citri, transmitted by the leafhopper vector Circulifer tenellus.
Conclusions:
- Accurate differentiation between MLO and S. citri infections is essential, as co-infections can obscure the true causal agent of plant disease.
- Serological methods like ELISA are valuable tools for comparing MLO and identifying pathogens in planta.
- Understanding pathogen reservoirs and vectors is critical for managing plant diseases caused by these wall-less bacteria.
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