Fundamentals of Biochemical Engineering, Part 1 - Bailey, J., & Ollis, D. 1989

Introduction to Microbiology
Major Cell Types
Algae and Protozoa

These relatively large eukaryotes exhibit a complex and highly ordered Structure. Euglenids, for instance, are motile via flagella, lack a rigid Cell wall, but possess a light-sensitive spot known as an eyespot (stigma). This organelle responds to light, directing the Cells toward brighter areas—a critical survival mechanism for these Algae, which harness light energy just like most other algae. Many diatoms (another algal group) feature intricate, two-part external frustules (shells) composed primarily of silica. These frustules find widespread industrial application as filtering Materials.

Heightened interest in algae stems from their potential value as a food source or dietary Supplement. In Japan, for example, several industrial facilities currently cultivate microalgae precisely for these purposes. Furthermore, seaweeds are consumed as food on a fairly large scale throughout Asia. Unlike microorganisms, seaweeds are Multicellular Organisms composed of numerous uniform cells. Along with simpler cyanobacteria, eukaryotic algae play a vital role in global biogeochemical cycles (Ch. 14).

In a sense, algae can be regarded as primitive plants; similarly, Protozoa incapable of harnessing solar energy may be considered primitive animals. The natural habitats, Morphology, and activities of protozoa vary widely. Some trypanosomes, for instance, act as vectors for serious diseases, including African sleeping sickness, or trypanosomiasis. Conversely, protozoa such as Trichonympha inhabit the guts of termites, aiding them in wood Digestion. Amoebas lack a fixed shape and constantly change their outer contours, whereas heliozoans (sun animalcules) are characterized by an internal Skeleton and a defined form.

Although protozoa are not currently utilized on an industrial scale for producing cell biomass or synthesizing metabolic products, they play a major role—alongside microorganisms—in biological wastewater Treatment (Ch. 14). From a microbiologist's perspective, these processes, widely implemented worldwide in municipalities and large industrial plants, are remarkably complex. Domestic and industrial wastewaters represent an intricate mixture comprising various nutrients and a diverse array of microorganisms; consequently, their treatment requires A wide variety of protists as well. These organisms compete for nutrients, prey upon one another, and interact in numerous other ways characteristic of a micro-ecosystem. Species interactions will be explored and analyzed in greater detail in Ch. 13.