The difference between Mycoplasma and Mycobacterium lies primarily in the presence or absence of a cell wall. Mycoplasma completely lacks a cell wall, making them highly pleomorphic, while Mycobacterium has a thick, waxy, mycolic-acid-rich cell wall that provides rigidity and resistance to antibiotics. This single structural variation leads to differences in staining, pathogenicity, and antibiotic response.
Understanding the difference between Mycoplasma and Mycobacterium is essential in microbiology and clinical diagnosis because both genera contain species that cause significant human diseases. However, their cellular structures, staining properties, and treatment strategies vary dramatically.
This article explains both bacterial genera in detail, highlights their characteristics, provides examples, and summarizes all key differences in a clear comparison table.
What is Mycoplasma?
Mycoplasma is a unique genus of bacteria known for lacking a cell wall, which makes them the smallest free-living bacteria ever discovered. Because the bacterial cell wall typically determines shape, Mycoplasma species appear pleomorphic, meaning they can exhibit multiple shapes.
Key Features of Mycoplasma
- No cell wall → no fixed shape
- Gram-negative appearance (but not true Gram-negative)
- Highly flexible cell membrane with sterols
- Aerobic or facultative anaerobic
- Around 200 known species
Diseases Caused by Mycoplasma
- Mycoplasma pneumoniae – causes atypical pneumonia (“walking pneumonia”)
- Mycoplasma hominis – urinary and reproductive tract infections
- Mycoplasma genitalium – sexually transmitted infections
- Ureaplasma spp. – neonatal infections, infertility
Why Mycoplasma is Hard to Treat
Mycoplasma species are naturally resistant to β-lactam antibiotics (like penicillin) because these antibiotics target cell wall synthesis, and Mycoplasma has no cell wall.
Instead, antibiotics like macrolides, tetracyclines, or fluoroquinolones are used.
Mycoplasma in Laboratory Contamination
Mycoplasma contamination is a serious issue in cell culture laboratories because:
- They grow slowly
- They do not cause turbidity
- They alter cellular behavior undetected
What is Mycobacterium?
Mycobacterium is a genus of acid-fast, Gram-positive bacteria characterized by a thick, waxy cell wall rich in mycolic acids. This unique wall makes them resistant to harsh environments and many antibiotics.
Key Features of Mycobacterium
- Thick peptidoglycan layer
- High mycolic acid content → waxy texture
- Acid-fast positive (retain red stain in Ziehl–Neelsen method)
- Slow-growing, mold-like colonies
- Belongs to family Mycobacteriaceae
Common Pathogens (Examples)
- Mycobacterium tuberculosis – causes tuberculosis (TB)
- Mycobacterium leprae – causes leprosy
- Mycobacterium avium complex (MAC) – opportunistic infections
- Mycobacterium ulcerans – Buruli ulcer
Major Groups of Mycobacteria
- Mycobacterium tuberculosis complex (MTBC)
- M. tuberculosis
- M. bovis
- M. africanum, etc.
- Nontuberculous Mycobacteria (NTM)
- M. avium
- M. intracellulare
- Mycobacterium leprae
Why Mycobacterium is Hard to Treat
The thick cell wall prevents penetration of many antibiotics including penicillin. Treatments require multi-drug therapy, such as:
- Isoniazid
- Rifampin
- Ethambutol
- Pyrazinamide
Key Difference Between Mycoplasma and Mycobacterium (Table Form)
| Feature | Mycoplasma | Mycobacterium |
| Cell Wall | Absent | Present (thick, waxy, mycolic-acid-rich) |
| Shape | Pleomorphic, no fixed structure | Slightly curved or straight rods |
| Gram Reaction | Not stainable (no cell wall) | Gram-positive appearance |
| Acid Fastness | Not acid-fast | Strongly acid-fast (due to mycolic acids) |
| Family | Mycoplasmataceae | Mycobacteriaceae |
| Diseases Caused | Atypical pneumonia, urogenital infections | Tuberculosis, leprosy, ulcers |
| Antibiotic Sensitivity | Resistant to β-lactams | Resistant to many drugs; requires long-term therapy |
| Size | Very small (simplest free-living bacteria) | Larger, more complex |
| Reproduction | Rapid due to small genome | Slow-growing |
Conclusion – Difference Between Mycoplasma and Mycobacterium
In conclusion, the difference between Mycoplasma and Mycobacterium revolves around one essential feature—the cell wall. Mycoplasma lacks it, making them pleomorphic and naturally resistant to β-lactam antibiotics, whereas Mycobacterium possesses a dense, mycolic-acid-rich wall that makes them acid-fast and highly drug-resistant. Understanding this difference helps in diagnosis, treatment, and laboratory identification.
References:
1. “Mycobacterial Diseases Open Access.” Mycobacterial Diseases. N.p., n.d. Web.
2. “Mycobacteria.” Mycobacteria. N.p., n.d. Web.
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