Inclusion bodies (storage granules)
Start with the big picture
Most bacterial inclusion bodies are non-membranous cytoplasmic aggregates that accumulate when nutrients are plentiful and can be used during scarcity. Their contents differ: volutin granules store inorganic polyphosphate and are associated with Corynebacterium diphtheriae; PHB and glycogen granules provide carbon-energy reserves; and sulfur granules can serve as electron donors. Specialized structures include magnetosomes for orientation along geomagnetic lines, carboxysomes for CO₂ fixation, and gas vacuoles that affect buoyancy. Phase-contrast microscopy and special stains such as Neisser and Sudan Black can help reveal inclusions. Recognizing their composition and appearance provides context for bacterial survival and may support diagnostic, taxonomic, and metabolic assessment.
What you'll learn
- Describe the general composition and role of bacterial inclusion bodies.
- Distinguish major storage granules by their contents and functions.
- Explain the specialized roles of magnetosomes, carboxysomes, and gas vacuoles.
- Identify microscopy and staining approaches used to detect inclusions.
- Relate inclusion-body findings to bacterial identification and metabolic profiling.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
