Name: prokaryotic cell storage inclusions
Uploaded: 2025-06-12T09:31:19.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.c

Cell Inclusions

&#160;Inclusions are intracellular structures that serve as storage sites for nutrients, metabolic byproducts, or other compounds.Excess carbon is often stored as poly-&#946;-hydroxybutyric acid granules, composed of lipid polymers, or glycogen granules. These storage forms serve as carbon reservoirs and rapid energy sources when needed.Metachromatic granules, or volutin, are polyphosphate granules commonly found in Corynebacterium. These granules store inorganic phosphate for nucleic acid and ATP synthesis.Sulfur globules, an energy reserve for sulfur-oxidizing bacteria such as Thiobacillus, store elemental sulfur.Some cyanobacteria produce carboxysomes, containing enzymes like RuBisCO, that facilitate carbon dioxide fixation.Gas vacuoles are air-filled hollow structures that enable aquatic bacteria and archaea to maintain buoyancy, optimizing access to light and nutrients.Magnetosomes, composed of magnetite or greigite, are found in bacteria such as Magnetospirillum magnetotactic. They align aquatic bacteria with the Earth&#8217;s magnetic field and guide them downwards towards anaerobic zones with low oxygen concentrations.

cell inclusions

Prokaryotic cells possess a variety of inclusions that play crucial roles in nutrient storage, metabolic processes, and environmental adaptation. These structures enable bacteria to thrive under fluctuating environmental conditions by storing essential resources and optimizing their metabolic efficiency.Carbon Storage: Poly-&#946;-Hydroxybutyric Acid and Glycogen GranulesBacteria frequently store excess carbon in specialized granules. Poly-&#946;-hydroxybutyric acid (PHB) granules are lipid polymers that act as a long-term carbon and energy reserve. These granules provide an energy source that bacteria can metabolize during nutrient scarcity. Additionally, glycogen granules, composed of highly branched glycogen polymers, offer a rapid energy source. The branched structure of glycogen allows for efficient enzymatic access, facilitating swift energy release when needed.Poly-&#946;-hydroxybutyric acid (PHB) granules have several industrial applications due to their role in producing biodegradable plastics. PHB is a polyhydroxyalkanoate (PHA) that is an alternative to petroleum-based plastics. It is valued for being biocompatible, non-toxic, and fully degradable in the environment.Metachromatic Granules: Polyphosphate ReservesMetachromatic granules, also known as volutin, are intracellular storage deposits of inorganic polyphosphate. The term "metachromatic" refers to their property of staining in a different (meta) color than the dye applied due to their high phosphate content. These granules are also called "volutin" because they were first observed in Spirillum volutans. Commonly observed in genera such as Corynebacterium, these granules serve as reservoirs for phosphate, a critical component for nucleic acid and ATP synthesis. This storage strategy supports bacterial growth and reproduction during periods of phosphate limitation.Sulfur Globules: Elemental Sulfur StorageSulfur globules are prominent in sulfur-oxidizing bacteria, such as Thiobacillus. These inclusions store elemental sulfur derived from the oxidation of reduced sulfur compounds, such as hydrogen sulfide or thiosulfate, functioning as a readily accessible energy reserve. This stored sulfur can be oxidized further to sulfate during periods of energy demand, contributing to the bacterial cell's metabolism. The process not only provides energy but also plays a role in sulfur cycling in the environment, illustrating the ecological significance of these inclusions.Carboxysomes: Carbon FixationCyanobacteria and some other autotrophic prokaryotes produce carboxysomes, proteinaceous microcompartments containing ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). These inclusions facilitate carbon dioxide fixation by concentrating CO&#8322; and enhancing RuBisCO efficiency, a critical adaptation for photosynthetic organisms in low-CO&#8322; environments.Gas Vacuoles: Buoyancy RegulationGas vacuoles, found in aquatic bacteria and archaea, are hollow, protein-lined structures that regulate buoyancy. By adjusting their position within the water column, these organisms optimize their access to light and nutrients. This adaptation is particularly vital for photosynthetic and aquatic bacteria in stratified water environments.Magnetosomes: Navigational AidsMagnetosomes are membrane-bound inclusions containing iron oxides (e.g., magnetite) or greigite. These structures are prevalent in bacteria such as Magnetospirillum magnetotactic. By aligning with the Earth's magnetic field, magnetosomes guide bacteria towards low-oxygen or anaerobic zones, which are more favorable for their metabolism. This magnetic navigation system exemplifies the specialized adaptations of prokaryotic cells to their ecological niches.In summary, prokaryotic inclusions are multifunctional structures that enable bacteria to efficiently store nutrients, regulate environmental interactions, and optimize metabolic processes. These adaptations illustrate the remarkable versatility and resilience of prokaryotic life forms.

Prokaryotic cells possess a variety of inclusions that play crucial roles in nutrient storage, metabolic processes, and environmental adaptation. These ...

Education

JoVE Core

Microbiology

Unit

Microbial Cell Structure and Function        

KEY TERMS AND CONCEPTS

prokaryotic cell storage inclusions

Prokaryotic cell storage inclusions help bacteria store nutrients, manage energy, and adapt to changing environments. These inclusions let cells survive when food, phosphate, sulfur, light, or oxygen levels change. They are important examples of how simple cells can still have highly specialized structures.

Some inclusions store carbon. Poly-β-hydroxybutyric acid, or PHB, forms granules that act as a long-term carbon and energy reserve. Glycogen granules also store carbon, but they provide a faster energy source because glycogen is highly branched and enzymes can access it quickly.

PHB has another important role outside the cell. It is a polyhydroxyalkanoate, or PHA, and is used to make biodegradable plastics. It is valued because it is biocompatible, non-toxic, and fully degradable in the environment.

Other inclusions store phosphate. Metachromatic granules, also called volutin, are deposits of inorganic polyphosphate. They were first observed in Spirillum volutans, and they are common in bacteria such as Corynebacterium. These granules stain a different color than the dye used because of their high phosphate content, and they provide phosphate for nucleic acids and ATP.

Sulfur globules store elemental sulfur in sulfur-oxidizing bacteria such as Thiobacillus. The sulfur comes from oxidized reduced sulfur compounds like hydrogen sulfide or thiosulfate. The stored sulfur can be oxidized further to sulfate when the cell needs energy, and this also helps sulfur move through the environment.

Some prokaryotes use inclusions for carbon fixation and movement. Cyanobacteria and other autotrophic prokaryotes make carboxysomes, which are protein-based microcompartments that contain RuBisCO. These structures concentrate CO2 and help RuBisCO work better, especially when CO2 is low. Gas vacuoles are hollow, protein-lined structures in aquatic bacteria and archaea that control buoyancy, so the cells can stay where light and nutrients are available.

Magnetosomes help bacteria navigate. These membrane-bound inclusions contain iron oxides such as magnetite or greigite. In bacteria like Magnetospirillum magnetotacticum, magnetosomes align with Earth’s magnetic field and guide cells toward low-oxygen or anaerobic zones that better fit their metabolism. Together, these inclusions show how prokaryotic cells store resources, sense their surroundings, and live successfully in many habitats.

Prokaryotic Cell Storage Inclusions

prokaryotic vs. eukaryotic cells

Cell Organization in Prokaryotes and Eukaryotes

Prokaryotic and eukaryotic cells show two major patterns of cell organization. These differences shape the structure, size, and function of living things across the domains of life. Prokaryotic cells, such as bacteria and archaea, are simple in structure. They do not have a nucleus or other membrane-bound organelles. Their DNA is usually a single circular molecule found in the nucleoid region, which is not surrounded by a nuclear membrane. Prokaryotes are usually very small, about 0.1 to 5.0...

microbial morphologies 

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Microbial shapes and cell forms help bacteria, archaea, and eukaryotic microbes survive in many environments. Cell shape affects how these organisms grow, take up nutrients, and handle waste. It also reflects the link between structure and function. Among bacteria, cocci and bacilli are the most common shapes. Cocci are spherical cells, and they may appear alone or in pairs called diplococci, chains called streptococci, clusters called staphylococci, or groups of four called tetrads. Bacilli...

bacterial cell wall 

Gram-Positive and Gram-Negative Walls

Bacterial cell walls give bacteria their shape and help protect them from osmotic stress. This rigid but flexible layer surrounds the plasma membrane and supports cellular integrity. Its main building block is peptidoglycan, a mesh-like polymer that adds strength while still allowing some flexibility. Peptidoglycan is made of alternating N-acetylglucosamine, or NAG, and N-acetylmuramic acid, or NAM. Short amino acid chains connect these sugar units and help form the strong network. The...

archaeal cell wall

Archaeal Cell Wall Types and Functions

Archaeal cell walls protect archaea and help them survive in extreme environments. Unlike bacterial cell walls, they do not have the peptidoglycan layer found in most bacteria. Instead, archaea use a range of materials, including proteins, polysaccharides, and pseudomurein, to build their outer layer. The most common archaeal cell wall is the S-layer, or surface layer. It is made of tightly packed protein or glycoprotein units that form a crystalline lattice. These repeating patterns can make...

peptidoglycan synthesis

Building the Bacterial Cell Wall

Peptidoglycan builds the bacterial cell wall and gives the cell its shape and strength. It is a mesh-like polymer around the bacterial plasma membrane. The polymer is made of repeating sugar units, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), linked by β-1,4 glycosidic bonds. Short peptide chains cross-link the sugar chains and make the wall more rigid. Peptidoglycan biosynthesis starts in the cytoplasm with soluble precursors. Uridine diphosphate, or UDP, binds to NAG and NAM to...

plasma membrane in bacteria and archaea

Bacterial vs Archaeal Membrane Lipids

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outer layers of the cell envelope

Capsules, Slime Layers, and S-Layers

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flagella and motility in bacteria

Bacterial Flagella as Tiny Rotary Motors

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fimbriae, pili, and axial filaments

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Prokaryotic cell storage inclusions help bacteria store nutrients, manage energy, and adapt to changing environments. These inclusions let cells survive when food, phosphate, sulfur, light, or oxygen levels change. They are important examples of how simple cells can still have highly specialized structures. Some inclusions store carbon. Poly-β-hydroxybutyric acid, or PHB, forms granules that act as a long-term carbon and energy reserve. Glycogen granules also store carbon, but they provide a...

endospores and sporulation

How Bacteria Survive with Endospores

Endospores help some bacteria survive harsh conditions. These dormant cells are made mainly by Gram-positive bacteria such as Bacillus and Clostridium. They are highly resistant to heat, ultraviolet and ionizing radiation, drying, and toxic chemicals. In rare cases, endospore-like structures have also been seen in some Gram-negative bacteria, including Coxiella burnetii and Sporosarcina ureae, as well as in other species exposed to extreme conditions. Sporulation begins when bacteria face...

nucleoid

How Prokaryotes Organize DNA

Prokaryotes organize their DNA in the nucleoid, a distinct region where genetic material and associated proteins are packed. Because prokaryotic cells do not have a membrane-bound nucleus, the nucleoid helps keep DNA organized and available for cell activities. In most bacteria and archaea, the DNA is a single, circular, double-stranded molecule that is tightly compacted by supercoiling and protein interactions. Nucleoid-associated proteins, or NAPs, help shape and maintain this DNA region.

surface appendages of archaea

Archaeal Pili and Archaella in Action

Archaeal pili and archaella help archaea survive, attach, and move in challenging environments. These surface appendages support adhesion, biofilm formation, and motility. They give archaeal cells key advantages in habitats that can be extreme. Pili are filament-like structures made from pilin protein subunits. Their main role is adhesion, which means helping cells stick to surfaces. They also support biofilm formation, where cells live in a shared, surface-attached community. Some pili are...

key terms and concepts

Learn how prokaryotic cell inclusions store carbon, phosphate, and sulfur, support carbon fixation, control buoyancy, and guide bacteria with magnetosomes.

Prokaryotic Cell Storage Inclusions | JoVE K12

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BIO.4.e

Prokaryotic Cell Storage Inclusions

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