Parsek Micro410 Lecture

Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Organization of the Prokaryotic Cell Prokaryotic Structures fimbriae Size Range of Prokaryotes bacillus See Table 4.1 (rigid) vibrio Nanobacteria 0.05‐0.2 µm (0.14‐0.2 µm) (flexible) Thiomargarita namibiensis Mycoplasma are 700‐750 µm (Fig. 4.2) pleomorphic green alga Nanochlorum eukaryotum Mycoplasma 0.1‐ ~1-2 µm in diameter 0.3 µm Fig. 4.1 Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Staining cells for Microscopic observation Cell Arrangements Motility- ~80% of prokaryotes are motile streptococcus Staining properties: Gram Stain staphylococcus Fig. 2.3 Gram Stain (1884) (Bacteria) Gram-negative mixed culture Gram-positive Fig. 2.3 and 2.4 Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Functions of the cytoplasmic membrane The phospholipid bi‐layer Fig. 4.9 Fig. 4.4 What is the structure of bacterial phospholipids? Other components of the cytoplasmic membrane Figs. 4.5‐4.6 Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Archaeal membranes can be a lipid monolayer Archaeal phospholipids have an ether linkage Fig. 4.7 Fig. 4.8 Importance of Cell Wall Schematic diagram cell wall • Provides rigidity to cell allowing cell to withstand the large osmotic/ionic Fig. 4.16 changes a bacterium may experience in its environment, and turgor pressure of cytoplasm (conc. of solutes in cytoplasm). Cell lysis • May have a role in shape determination. • Provides a barrier against certain toxic chemical and biological agents. • Site of action of some of the most commonly used antibiotics used to treat bacterial infections (penicillin family). • A component of cell wall of Bacteria is responsible for some of symptoms associated with an infection, e.g. fever response (lipopolysaccharide and lipoteichoic acid). Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Prokaryotes Lacking a Cell Wall Functions of Cell Wall Structure • The mollicutes group of Bacteria (5 genera, Mycoplasma) • Provides shape (?) and rigidity Properties of group: • Involved in cell wall biosynthesis - Sensitive to osmotic lysis • Involved in cell division (protoplast/sphereoplast) - Resistant to antibiotics directed at cell wall biosynthesis • Involved in motility (penicillins) • Influences permeability (teichoic acid, LPS, OCWM) - pleomorphic Methanotrophs - contain sterols in membrane similar to those found in • LPS may inhibit phagocytosis membranes of animal cells. • LPS and lipoteichoic acid elicit symptoms of Gram-negative ‐ some are parasites of plants and animals. and positive bacteria infection, respectively. • L-forms of Bacteria M. pneumoniae • Certain Archaea (Thermoplasma) Cell-walled Prokaryotes Gram-positive Gram-negative ~40-90% of wall is Outer cell wall membrane • Contain peptidoglycan peptidoglycan ~5-10% All cells in the domain Bacteria contain peptidoglycan with exception of Planctomyces and Chlamydia • Lack peptidoglycan All cell-walled Archaea Murein layer C. trachomatis- intracellular parasite; leading cause of blindness in world. Energy parasite Has genes for peptidoglycan synthesis and ATP synthase but does not express genes! Fig. 4.16 Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Gram-negative Gram-positive NAG NAM Peptidoglycan strand L-lysine DAP DAP L-lysine Fig. 4.29 Fig. 4.17 Cross-linking of Adjacent Peptidoglycan Strands Peptidoglycan Synthesis Murein sacculus Fig. 4.19 Fig. 6.7a Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Peptidoglycan Synthesis Cross-linking of Peptidoglycan Strands cytoplasm cell membrane cell wall autolysins Bactoprenol-P Pi UDP-NAM M G pentapeptide G M Bactoprenol Bactoprenol-P-P P M UMP G P NAM G M Transpeptidase (FtsI) pentapeptide M G UDP-NAG Bactoprenol G P NAM‐NAG P NAM-NAG UMP D-Ala pentapeptide Fig. 6.7b D-alanine carboxypeptidase tRNA-aa Interbridge peptide Peptidoglycan Synthesis Cross-linking of Peptidoglycan Strands cytoplasm cell membrane cell wall autolysins Bactoprenol-P Pi UDP-NAM Bacitracin M G pentapeptide G D-cycloserine Bactoprenol M (Oxamycin) Bactoprenol-P-P P M UMP G β-lactams P NAM G transpeptidase M penicillins and cephalosporins pentapeptide M G UDP-NAG lysozyme Bactoprenol G Vancomycin P NAM‐NAG P NAM-NAG pentapeptide UMP D-Ala pentapeptide Fig. 6.5 D-alanine carboxypeptidase tRNA-aa Interbridge peptide Microm 410 Fall 2009: Prokaryotic Structure/Function part 1 Dr. Matt Parsek Antibiotic Resistance • Inactivate antibiotic β-lactamase (penicillinase) Clavulanic acid Augmentin and Trimentin (combination of clavulanic acid and amoxicillin or ampicillin respectively) • Change chemistry of target site • Limit access of the antibiotic to target site.

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