Pleomorphism

Detailed article on pleomorphism in biology and medicine

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Pleomorphism refers to the ability of some microorganisms, cells, or organisms to alter their shape or size in response to environmental conditions. This phenomenon is observed in various biological contexts, including microbiology, oncology, and cellular biology.

Overview

Pleomorphism is derived from the Greek words "pleo," meaning "more," and "morph," meaning "form." It describes the variability in the morphology of cells and organisms, which can be influenced by genetic, environmental, or pathological factors.

Microbiological Pleomorphism

In microbiology, pleomorphism is often associated with certain bacteria and fungi that can change their shape or size. For example, some bacteria, such as those in the genus Mycoplasma, lack a rigid cell wall, allowing them to exhibit a variety of shapes. This adaptability can be advantageous for survival in diverse environments.

Examples

• Mycoplasma species: These bacteria are known for their lack of a cell wall, which allows them to assume various shapes, from spherical to filamentous.
• Corynebacterium species: These bacteria can appear as rods, club-shaped, or even filamentous forms.

Oncological Pleomorphism

In oncology, pleomorphism refers to the variability in size and shape of cells and nuclei within a tumor. This is a hallmark of malignancy and is often used as a criterion in the histopathological grading of tumors.

Significance

Pleomorphic cells in a tumor indicate a high degree of anaplasia, which is associated with aggressive behavior and poor prognosis. The presence of pleomorphic cells is a key feature in the diagnosis of certain cancers, such as pleomorphic adenoma and pleomorphic sarcoma.

Cellular Pleomorphism

In cellular biology, pleomorphism can refer to the ability of cells to change shape in response to external stimuli. This is particularly evident in cells of the immune system, such as macrophages, which can alter their morphology to engulf pathogens or debris.

Historical Context

The concept of pleomorphism has evolved over time. In the 19th century, the pleomorphism theory proposed by Antoine Béchamp suggested that microorganisms could change form in response to their environment. This theory was largely overshadowed by the germ theory of disease proposed by Louis Pasteur, which emphasized the specificity of microbial forms.

Also see

• Monomorphism
• Cellular differentiation
• Anaplasia
• Histopathology

External links

• National Center for Biotechnology Information
• National Cancer Institute