Slime Moulds

1.0General Characteristics of Slime Mould

Slime moulds, fascinating members of the Protista kingdom, have unique features that distinguish them. They shift between amoeboid and fungus-like stages, thriving in damp areas where they decompose decaying matter. Their life cycle involves a multinucleate plasmodium and individual cell stages. Moving amoeboidly, they feed on bacteria and fungi through phagocytosis. Reproduction occurs via spores within sporangia or through cell aggregation into fruiting bodies.

Slime moulds come in two main types: Acellular and Cellular. Acellular slime moulds are also called Plasmodial slime moulds.

2.0Acellular Slime Moulds or Plasmodial Slime Moulds

Plasmodial slime moulds, under favourable conditions, appear as vibrant, streaming masses of protoplasm that move like amoebas on moist, decaying organic matter such as logs and leaves. These masses, known as plasmodia, lack cell walls and contain multiple nuclei. As they grow, the diploid nuclei undergo repeated division.

When conditions become less favourable or when the plasmodium matures, it migrates to a well-lit area and transforms into intricate fruiting bodies. 

These structures produce spores with cellulose walls, providing resistance to environmental challenges. The spores germinate in the presence of moisture, giving rise to either non-flagellated amoeboid myxamoebae or flagellated swarm cells. Initially haploid, these cells eventually fuse to create a diploid zygote. The zygote, nourished by feeding, undergoes synchronous mitotic division, forming a multinucleate plasmodium and restarting the life cycle.

3.0Cellular Slime Moulds

The vegetative stage of cellular slime moulds starts with individual amoeboid cells called myxamoebae. These cells feed on bacteria and yeasts through phagocytosis. During times of abundant food, they multiply by mitosis and cytokinesis, generating new myxamoebae. As the food supply diminishes, myxamoebae release cyclic adenosine monophosphate (cAMP). This chemical attracts other myxamoebae, leading to their aggregation into a slug-like pseudoplasmodium.

The pseudoplasmodium, initially mobile, leaves a slime trail but eventually becomes stationary. In the final stages of the asexual phase, pseudoplasmodial cells differentiate into prestalk and prespore cells. A fruiting body called a sorus or sporocarp develops, matures, and produces spores. These spores are eventually released. In favourable conditions, the spores germinate to release haploid amoebae, initiating the cycle anew.

4.0Ecological Role of Slime Moulds

Slime molds are a vital part of nutrient cycling. Through decomposition of organic matter, they ensure the return of nutrients to the soil, supporting diverse ranges of plants and other organisms. They regulate microbial populations by interacting with bacteria and fungi and contribute to soil health. These roles clarify their importance in maintaining ecological balance.