Difference Between Mycoplasma and Phytoplasma

The main difference between mycoplasma and phytoplasma is that the mycoplasma refers to pleuropneumonia-like organisms (PPLOs), which can be parasitic in humans, animals, and plants whereas the phytoplasma refers to mycoplasma-like organisms (MLOs), which can be parasitic in plant phloem tissue and some insects.  

Mycoplasma and phytoplasma are obligate parasites, which lack a cell wall. They can be either pleomorphic or filamentous in shape. The size of both organisms is less than 1 µm. 

Key Areas Covered 

1. What is Mycoplasma
     – Definition, Facts, Diseases
2. What is Phytoplasma
     – Definition, Facts, Diseases
3. What are the Similarities Between Mycoplasma and Phytoplasma
     – Outline of Common Features
4. What is the Difference Between Mycoplasma and Phytoplasma
      – Comparison of Key Differences

Key Terms

Cell Wall, Diseases, Genome, Mycoplasma, Obligate Parasite, Phytoplasma 

What is Mycoplasma 

Mycoplasma is a small prokaryote found free in soil and sewage as saprophytes and as parasites in humans, animals, and plants. It was first called pleuropneumonia-like organisms (PPLOs) since it formed pneumonia in humans and cattle. Then, it was given the name mycoplasma due to the filamentous nature of the bacterium. Mycoplasma is either filamentous or pleomorphic due to the lack of a cell wall, which is the most characteristic feature among other bacteria. Mycoplasma is Gram-positive. Also, mycoplasma contains the smallest genome among all prokaryotes. The genome of mycoplasma contains 500-1000 genes.  

Figure 1: Mycoplsma Classification

Mycoplasma pneumoniae infects both upper and lower respiratory tract giving rise to symptoms such as cough, fever, and headache, which may persist for several weeks. Also, Ureaplasma urealyticum forms nongonococcal urethritis in men, resulting in dysuria and urethral discharge. Due to the lack of a cell wall, mycoplasma has to be grown in an isotonic medium. Also, it requires cholesterol for growth. Mycoplasma forms fried-egg-shaped colonies on agar. The growth of mycoplasma can be inhibited by the antibodies that bind to the surface antigens such as lipoproteins, lipoglycans, and glycolipids.  

What is Phytoplasma 

Phytoplasma is a small, plant pathogenic bacterium limited to the phloem. It is transmitted by insects. Phytoplasma belongs to the class Mollicutes. It was first called mycoplasma-like organisms (MLOs). Phytoplasma also lacks a rigid cell wall. Rounded or filamentous varieties of phytoplasma can be identified. Rounded phytoplasma is 200–1100 nm in diameter while filamentous ones are 50–400 nm in diameter and 200–3000 nm in length.

Figure 2: Phyllody on Coneflower with Aster Yellows

It has been identified that phytoplasma can be transmitted by 30 insect species into 200 diverse plant species. The most characteristic symptoms of phytoplasma infection in plants include clustering of branches (witches’ bloom), retrograde metamorphosis of the floral organs to the condition of leaves (phyllody), green coloration of non-green flower parts (virescence), reddening of leaves and stems, generalized yellowing, growth of elongated stalks (bolting), formation of bunchy fibrous secondary roots, decline and stunting of plants, and phloem necrosis. 

Similarities Between Mycoplasma and Phytoplasma 

• Mycoplasma and phytoplasma are small bacteria with a small genome. 
• They do not have a cell wall. Their shape can be either pleomorphic or filamentous. 
• Both can be obligate parasites. 

Difference Between Mycoplasma and Phytoplasma 

Definition 

Mycoplasma refers to any group of small typically parasitic bacteria that lack cell walls and sometimes cause diseases while phytoplasma refers to an obligate bacterial parasite of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. 

First Called 

Mycoplasma was also called pleuropneumonia-like organisms (PPLOs) while phytoplasma was first called mycoplasma-like organisms (MLOs).  

Parasitic in 

The mycoplasma is parasitic in humans, animals, plants whereas phytoplasma is parasitic in plant phloem tissue and in some insects.  

Culturing 

The mycoplasma can be grown in an isotonic medium while phytoplasma cannot be cultured. 

Examples 

Mycoplasma pneumoniae, Ureaplasma urealyticum, Mycoplasma hominis, and Mycoplasma genitalium are some mycoplasmas while the genus of phytoplasma is Candidatus Phytoplasma.  

Diseases 

Mycoplasma causes upper and lower respiratory tract infections and nongonococcal urethritis in men while phytoplasma causes diseases in plants. 

Conclusion 

The mycoplasma is a small bacterium, which causes diseases in humans, animals, and plants while phytoplasma causes diseases in plants. Both lack a cell wall and have small genomes. The main difference between mycoplasma and phytoplasma is the type of parasitism. 

Reference:

1. Razin, Shmuel. “Mycoplasmas.” Medical Microbiology., U.S. National Library of Medicine, 1 Jan. 1996, Available Here
2. Hogenhout, S A, et al. “Phytoplasmas: Bacteria That Manipulate Plants and Insects.” Molecular plant pathology., U.S. National Library of Medicine, July 2008, Available Here

Image Courtesy:

1. “Mycoplasma category tree” By Bfpage – Own work (CC BY-SA 4.0) via Commons Wikimedia      
2. “Phyllody on Coneflower with aster yellows” By Estreya – Own work (CC BY-SA 3.0) via Commons Wikimedia