Bacterial Cell Structures and Functions PDF

Hamus/hami Archaeal “grappling hooks” assist in surface attachment, forming biofilms. structurally resemble type IV pili except for barbed terminus, which attaches cells to surfaces or each other Cells of SM1 Archaea isolated hami Biofilm of SM1 Archaea  Cell Inclusi...

Hamus/hami Archaeal “grappling hooks” assist in surface attachment, forming biofilms. structurally resemble type IV pili except for barbed terminus, which attaches cells to surfaces or each other Cells of SM1 Archaea isolated hami Biofilm of SM1 Archaea  Cell Inclusions Inclusions function as energy reserves, carbon reservoirs, and/or have special functions. Enclosed by thin membrane Reduces osmotic stress  Carbon storage polymers Glycogen: Poly-β-hydroxyalkanoates (PHAs) polysaccharide of glucose + bodies glycogenin Containing poly-β-hydroxybutyric acid (PHB): lipid polymer  Polyphosphate granules: inorganic phosphate (Figure 2.22a) Sulfur globules: elemental sulfur found in periplasm (Figure 2.22b), oxidized to sulfate (SO42–) Figure 2.22  Carbonate minerals: biomineralization of barium, strontium, and magnesium (Figure 2.23) Electron micrograph of a cell of the cyanobacterium Gloeomargarita containing granules of the mineral benstonite [(Ba,Sr)6(Ca,Mn)6Mg(CO3)13]. A cell is about 2 μm wide. Magnetosomes: magnetic iron oxides (Figure 2.24); allow cell to undergo magnetotaxis: migration along magnetic field lines  Gas Vesicles Confer buoyancy in planktonic cells (Figure 2.25) Conical-shaped, gas-filled structures made of protein (Figure 2.26) Impermeable to water and solutes Molecular structure (Figure 2.26) Gas vesicles are composed of two proteins, GvpA and GvpC. (Figure 2.41) function by decreasing cell density, increasing buoyancy  Endospores Formed during endosporulation/sporulation Highly differentiated cells resistant to heat, harsh chemicals, and radiation (Figure 2.27) Survival structures to endure unfavorable growth conditions Phase-contrast photomicrographs showing different “Dormant” stage of intracellular locations of endospores in different species of bacteria bacterial life cycle Ideal for dispersal via wind, water, or animal gut Present only in some gram- positive bacteria, (e.g., Bacillus and Clostridium)  Clostridium sporulation cycle https://mmbr.asm.org/content/79/1/19 Similar to Bacillus subtilis in Figure 2.32 Flagella, Archaella, and Swimming Motility Flagella/archaella: structure that assists in swimming in Bacteria (Figure 2.33) and Archaea, respectively tiny rotating machines Flagellar and flagellation long, thin appendages (15–20 nm wide) different arrangements: polar, lophotrichous, amphitrichous, peritrichous increase or decrease rotational speed relative to strength of proton motive force lophotrichous polar peritrichous  Flagellar structure and activity helical in shape consists of several components (Figure 2.37) Filament composed of flagellin. reversible rotating machine  Archaella half the diameter of bacterial flagella (10–13 nm) (Figure 2.39a) move by rotation composed of several different filament proteins with little homology to bacterial flagellin speeds vary from 0.1–10x Escherichia coli structurally similar to type IV pili  Gliding Motility Bacteria only; no Archaea Slower and smoother than swimming Movement typically occurs away from colony. Requires surface contact Mechanisms excretion of polysaccharide slime type IV pili/twitching motility gliding-specific proteins (adhesion complexes or other specialized proteins)  Chemotaxis and Other Taxes Taxis: directed movement in response to chemical or physical gradients chemotaxis: response to chemicals phototaxis: response to light aerotaxis: response to oxygen osmotaxis: response to ionic strength hydrotaxis: response to water