Mycobacterium vs. Mycoplasma

What's the Difference?

Mycobacterium and Mycoplasma are both bacterial genera that belong to the phylum Actinobacteria. However, they differ in several aspects. Mycobacterium is characterized by its unique cell wall composition, which contains a high amount of mycolic acids, making it resistant to many antibiotics and disinfectants. This genus includes important pathogens such as Mycobacterium tuberculosis, the causative agent of tuberculosis. On the other hand, Mycoplasma lacks a cell wall and is known for its small size and minimal genome. This genus includes species like Mycoplasma pneumoniae, which is responsible for causing respiratory infections in humans. Additionally, Mycoplasma is known for its ability to colonize and infect a wide range of hosts, including humans, animals, and plants.


Cell WallContains mycolic acidsLacks a cell wall
SizeRelatively largerSmallest known free-living bacteria
ShapeRod-shaped (bacillus)Variable (pleomorphic)
GenomeContains a single circular chromosomeContains a single circular chromosome
RespirationAerobicFacultative anaerobic
PathogenicityCan cause tuberculosis and leprosyCan cause pneumonia and urinary tract infections
Growth RequirementsSlow-growing, requires specialized mediaFastidious, requires complex media

Further Detail


Mycobacterium and Mycoplasma are two distinct genera of bacteria that belong to the phylum Actinobacteria and Tenericutes, respectively. While both are prokaryotic microorganisms, they differ significantly in various aspects, including their cell wall composition, size, pathogenicity, and growth requirements. In this article, we will explore and compare the attributes of Mycobacterium and Mycoplasma, shedding light on their unique characteristics and highlighting the impact they have on human health and the environment.

Cell Wall Composition

Mycobacterium and Mycoplasma differ fundamentally in their cell wall composition. Mycobacterium possesses a unique cell wall structure that contains a high concentration of mycolic acids, which contribute to its acid-fast staining property. This feature allows Mycobacterium to resist decolorization during the acid-fast staining procedure, making it an essential diagnostic tool for diseases caused by Mycobacterium, such as tuberculosis and leprosy. On the other hand, Mycoplasma lacks a cell wall entirely, making it unique among bacteria. This absence of a cell wall contributes to its pleomorphic nature and renders it resistant to antibiotics that target cell wall synthesis.

Size and Morphology

When it comes to size and morphology, Mycobacterium and Mycoplasma exhibit distinct characteristics. Mycobacterium species are rod-shaped bacteria, typically measuring 1-10 micrometers in length. They possess a relatively rigid cell shape due to the presence of a peptidoglycan layer in their cell wall. In contrast, Mycoplasma species are much smaller, ranging from 0.2-0.8 micrometers in size. Their lack of a cell wall allows them to adopt various shapes, including spherical, filamentous, and irregular forms. This pleomorphism is a notable feature of Mycoplasma and contributes to its ability to evade the host immune system and colonize diverse niches within the human body.


Both Mycobacterium and Mycoplasma species can cause diseases in humans and animals, but their pathogenic mechanisms and clinical manifestations differ significantly. Mycobacterium species are known for their ability to establish chronic infections and induce granulomatous inflammation. Tuberculosis, caused by Mycobacterium tuberculosis, is a prime example of a mycobacterial disease that affects millions of people worldwide. Mycobacterium leprae, the causative agent of leprosy, is another significant pathogen within this genus. In contrast, Mycoplasma species are often associated with respiratory and urogenital infections. Mycoplasma pneumoniae, for instance, is a common cause of atypical pneumonia, while Mycoplasma genitalium is implicated in sexually transmitted infections. The pathogenicity of Mycoplasma is often attributed to its ability to adhere to host cells and evade the immune system through antigenic variation.

Growth Requirements

Mycobacterium and Mycoplasma also differ in their growth requirements, particularly in terms of nutrient and environmental conditions. Mycobacterium species are relatively slow-growing bacteria and have complex nutritional requirements. They are typically cultured on specialized media, such as Lowenstein-Jensen or Middlebrook agar, which provide the necessary nutrients and growth factors. Additionally, Mycobacterium species are aerobic organisms and require oxygen for growth. In contrast, Mycoplasma species have fastidious growth requirements and are often difficult to culture in the laboratory. They are typically grown in specialized broth or agar media supplemented with serum or other growth factors. Furthermore, Mycoplasma species are facultative anaerobes, capable of growing in both aerobic and anaerobic conditions.

Genomic Features

Genomic analysis has revealed intriguing differences between Mycobacterium and Mycoplasma species. Mycobacterium species have relatively large genomes, typically ranging from 4 to 7 million base pairs. They possess a high GC content and exhibit a complex genetic organization. The presence of numerous repetitive sequences and insertion elements contributes to the genomic plasticity of Mycobacterium, allowing for adaptation to diverse environments and the acquisition of antibiotic resistance. On the other hand, Mycoplasma species have significantly smaller genomes, ranging from 0.6 to 2.2 million base pairs. They possess a low GC content and exhibit a streamlined genetic organization. The reduction in genome size is thought to be a consequence of their parasitic lifestyle and reliance on the host for essential nutrients.


In conclusion, Mycobacterium and Mycoplasma are two distinct genera of bacteria that differ significantly in their cell wall composition, size, pathogenicity, growth requirements, and genomic features. Mycobacterium possesses a unique cell wall structure rich in mycolic acids, while Mycoplasma lacks a cell wall entirely. Mycobacterium species are typically rod-shaped and larger in size, while Mycoplasma species are pleomorphic and smaller. Mycobacterium is associated with chronic infections and granulomatous inflammation, while Mycoplasma often causes respiratory and urogenital infections. Mycobacterium has complex nutritional requirements and is aerobic, whereas Mycoplasma has fastidious growth requirements and is facultative anaerobic. Finally, Mycobacterium has larger genomes with high GC content, while Mycoplasma has smaller genomes with low GC content. Understanding the attributes of these bacteria is crucial for the diagnosis, treatment, and prevention of the diseases they cause, ultimately contributing to improved public health and well-being.

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