Model Answer
0 min readIntroduction
Mycoplasmas are a group of bacteria lacking a cell wall, belonging to the class Mollicutes. Their name, derived from ‘myco’ (fungus) and ‘plasma’ (living substance), reflects their initial misclassification due to their filamentous growth resembling fungi. These are the smallest known self-replicating organisms. Their unique structural characteristics and pathogenic potential make them significant in various fields, including plant pathology, veterinary medicine, and increasingly, biotechnology. Understanding their structure is crucial to comprehending their survival strategies and disease-causing mechanisms.
Structure of Mycoplasma
Mycoplasmas deviate significantly from typical bacterial structure, primarily due to the absence of a rigid cell wall. This absence dictates many of their unique characteristics.
- Cell Wall Absence: Unlike most bacteria, mycoplasmas lack a cell wall, rendering them resistant to penicillin and other antibiotics targeting cell wall synthesis.
- Pleomorphism: The lack of a cell wall results in extreme pleomorphism – the ability to assume various shapes and sizes. They can appear as cocci, filaments, or branched structures.
- Cell Membrane: The cell membrane is the outermost boundary and contains sterols (cholesterol in animal mycoplasmas, phytosterols in plant-associated species) for stability, compensating for the lack of a cell wall.
- Cytoplasm: The cytoplasm contains ribosomes (70S type, typical of bacteria), DNA (double-stranded, circular), and various enzymes necessary for metabolism.
- Genome: Mycoplasma genomes are relatively small compared to other bacteria, reflecting their parasitic lifestyle and dependence on the host for essential nutrients.
- Ribosomes: 70S ribosomes are present, but they differ slightly from those of other bacteria, influencing their susceptibility to certain antibiotics.
Importance of Mycoplasma
Mycoplasmas hold considerable importance in diverse areas, ranging from causing diseases to offering biotechnological potential.
Plant Pathology
- ‘Witches’ Broom’ Disease: Phytoplasma (formerly mycoplasmas) are responsible for ‘witches’ broom’ disease in plants like sesame, cassava, and ber. This disease causes excessive shoot proliferation, leading to reduced yield.
- Sandle Spike Disease: Affects sandal trees, causing stunted growth and reduced oil production.
- Little Leaf Disease: Causes chlorosis and reduced leaf size in various plants.
Animal Health
- Contagious Bovine Pleuropneumonia (CBPP): Caused by Mycoplasma mycoides, a highly contagious respiratory disease affecting cattle.
- Chronic Respiratory Disease (CRD) in Poultry: Often involves Mycoplasma gallisepticum and Mycoplasma synoviae, leading to significant economic losses in the poultry industry.
- Urogenital Infections: Mycoplasma hominis and Mycoplasma genitalium are associated with pelvic inflammatory disease and other urogenital infections in humans.
Biotechnological Applications
- Aseptic Fermentation: Mycoplasmas’ lack of a cell wall makes them useful in aseptic fermentation processes where contamination by other bacteria is a concern.
- Gene Transfer: Their ability to readily incorporate foreign DNA has potential applications in gene transfer studies.
- Model Organisms: Due to their simple structure and rapid growth, they serve as model organisms for studying fundamental biological processes.
| Area | Mycoplasma Involvement | Impact |
|---|---|---|
| Plant Pathology | Phytoplasma causing Witches’ Broom, Sandle Spike | Reduced crop yield, economic losses |
| Animal Health | M. mycoides causing CBPP, M. gallisepticum causing CRD | Livestock losses, poultry industry impact |
| Biotechnology | Aseptic fermentation, gene transfer | Potential for novel industrial processes |
Conclusion
In conclusion, mycoplasmas are unique bacteria characterized by the absence of a cell wall, leading to pleomorphism and diverse pathogenic capabilities. Their importance spans across plant pathology, animal health, and emerging biotechnological applications. Further research into their metabolic pathways and host-pathogen interactions is crucial for developing effective control strategies for mycoplasma-related diseases and harnessing their potential in various biotechnological fields. Understanding their adaptability and survival mechanisms is key to mitigating their impact on agriculture and public health.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.