Cell Inclusion Bodies in Bacteria

Flashcards covering prokaryotic cell inclusion bodies, carbon/energy storage polymers, polyphosphate/sulfur granules, magnetosomes, gas vesicles, metachromatic granules, and carboxysomes based on lecture notes.

What are cell inclusions in prokaryotic cells?

Reserve deposits within the cytoplasm that allow cells to store accumulated nutrients when they are plentiful and utilize them when the environment becomes deficient.

What is the generic term for carbon- and energy-storage polymers whose monomer carbon chain length ranges from $C_3$ to $C_{18}$?

Poly-$\beta$-hydroxyalkanoate (PHA)

What common carbon- and energy-storage inclusion body and chemical structure are illustrated in this image?

Poly-$\beta$-hydroxybutyrate (PHB), a common poly-$\beta$-hydroxyalkanoate (PHA) polymer.

How does glycogen differ from starch as a carbon and energy storage reserve?

Glycogen resembles plant starch, but differs slightly in the specific manner in which its glucose units are linked together.

What are the primary metabolic uses of polyphosphate granules stored in microorganisms?

They serve as phosphate sources for nucleic acid and phospholipid biosyntheses, and can be used by some organisms to generate ATP.

Where do elemental sulfur ($S^0$) globules reside within sulfur-oxidizing gram-negative prokaryotes?

They reside in the periplasm, which expands outward to accommodate the globules as $H_2S$ is oxidized to $S^0$ and contracts inward as $S^0$ is oxidized to $SO_4$.

Which organisms are depicted in this photomicrograph showing polyphosphate dark granules (a) and intracellular sulfur globules (b)?

(a) Heliobacterium modesticaldum containing polyphosphate granules and (b) the purple sulfur bacterium Isochromatium buderi containing sulfur globules.

What mineral particle composes magnetosomes, and what ability does it grant to magnetotactic bacteria?

Particles of magnetite ($Fe_3O_4$), which impart a magnetic dipole allowing the cell to orient and migrate along Earth's magnetic field lines (magnetotaxis).

What is the proposed biological function of magnetosomes in aquatic bacteria?

To guide primarily aquatic cells downward along Earth's magnetic field toward sediments where $O_2$ levels are lower.

What structures are shown in these micrographs of magnetotactic bacteria and isolated particles?

Magnetosomes (intracellular magnetite particles) bounded by nonunit membranes, formed in chains inside the cell.

What function do gas vesicles serve in planktonic prokaryotes?

They confer buoyancy on cells, allowing them to position themselves within a water column in response to environmental cues.

Are gas vesicles found in eukaryotic microorganisms?

No, gas vesicles have never been found in eukaryotic microorganisms.

What permeability properties characterize prokaryotic gas vesicles?

They are impermeable to water and solutes, but permeable to gases.

Which cyanobacterial genera are depicted showing gas vacuoles (a) and bundled gas vesicles (b)?

(a) Anabaena with phase-bright gas vacuoles and (b) Microcystis with gas vesicles arranged in bundles.

What are the roles of GvpA and GvpC in the structure of a gas vesicle?

GvpA is a small, hydrophobic, rigid $\beta$-sheet protein that forms the watertight shell ribs; GvpC is an $\alpha$-helix protein that cross-links and clamps the GvpA ribs at an angle to strengthen the shell.

What are metachromatic granules (volutin), and why do they have diagnostic significance?

They are large polyphosphate inclusion reserves that stain red with blue dyes like methylene blue; they serve diagnostic purposes because they are characteristic of Corynebacterium diphtheriae, the causative agent of diphtheria.

Which species of Arbuscular Mycorrhizal (AM) fungi does NOT form intraradical vesicles?

Gigaspora margarita

How are lipid inclusions in bacterial genera like Mycobacterium and Bacillus typically visualized under a microscope?

By staining cells with fat-soluble dyes, such as Sudan dyes.

Which enzyme is contained inside carboxysomes, and what is its role?

Ribulose 1,5-bisphosphate carboxylase, which is required by photosynthetic and autotrophic bacteria for carbon dioxide fixation.