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04.Bacterial Structure

The cell membrane fluid mosaic similar to eukaryotic

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The Cell Membrane • Fluid Mosaic similar to Eukaryotic (“Standard”) Cell Membrane - Usually lacks Sterols But many Bacteria have Sterol-like Hopanoids that stabilize the Cell Membrane. And Mycoplasmas and some Methanotropic Bacteria have Sterols in their Cell Membranes. • All-Singing, All-Dancing Structure in Bacteria - Site of Respiration, Photosynthesis, and Biosyntheses - Important during Cell Division • New Cell Membrane Synthesis substitutes for the Spindle Apparatus to separate Bacterial Chromosomes
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Structure of Bacteria Page 6 Internal Structures Cytoplasm (G = cell form) • 4/5th Water; 1/5th Stuff (Enzymes, Proteins, Lipids, Carbohydrates) Ribosomes (G = ribo nucleic acid + body) • Bacteria have 70S Ribosomes - 30S Small Subunit (S= Svedberg, a Sedimentation Coefficient) • 21 Proteins + 16S rRNA - 50S Large Subunit • 34 Proteins + 23S rRNA and 5S rRNA Nucleoid (Nuclear Region) • Chromosome (G = colored [“stained”] body) - Most Bacteria have a single circular, supercoiled, double-stranded DNA Chromosome in an irregularly shaped Area There are always Exceptions in Biology and in Cell Phone Contracts. Rhodobacter sp. (a Purple Bacterium) has two circular Chromosomes. Streptomyces sp. (an Actinomycete) has a Linear Chromosome. Rapidly growing Bacteria frequently contain more than one Copy of their Chromosome. The Chromosome in E. coli is a Circle measuring 1.58 mm. Think about the difficulty of putting a 1580 μ m Circle of DNA into a 1 x 2 μ m Cell. • Plasmids (L = small [feminine entity] in the cytoplasm) - Circular, double-stranded DNA Molecules in the Cytoplasm • Can exist and replicate Autonomously • Can integrate with the Bacterial Chromosome - Confer intriguing Advantages • F Factors encode for Conjugation, a Sexual Process • R Factors encode for Drug Resistance Bacterial Chromosomes are like Computer Hard-Drives. Plasmids are like USB Flash Drives. Gas Vesicles (L= little bladder) • Provide Buoyancy for (usually) Photosynthetic Bacteria Gas Vesicles are usually arranged in Bundles termed Gas Vacuoles (L= space). Gas Va cuoles can be seen with Pha se Contrast Microscopy. Gas Ve sicles can only be seen with E lectron Microscopy.
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Structure of Bacteria Page 7 Flagella (L = little whip) Thread-like Locomotion Appendage • Positioning is frequently Species-specific - Monotrichous Bacteria (G= one hair) have a Flagellum at one End of the Cell - Amphitrichous Bacteria (G= both hairs) have a Flagellum at both Ends of the Cell - Lophotrichous Bacteria (G= tufted hairs) have Clustered Flagella (usually clustered at one End, like Bunsen and Beaker) - Peritrichous Bacteria (G= surrounding hairs) have numerous Flagella covering the Cell Three Components • Filament • Hook • Basal Structure (Gram Positive Bacteria lack L and P Rings) - L Ring (Lipopolysaccharide) - P Ring (Peptidoglycan) - MS Ring (Membrane & Supramembrane [L = on top] ) - C Ring (Cytoplasm) - The MS and C Rings function together as a Reversible Turbine Rotor • Motor Proteins (Mot A and Mot B) form the Stator
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