Cell Structure Chapter 3 Nester 2nd. Ed. MICROBIOLOGY Cell Structure Chapter 3 Nester 2nd. Ed.

Microscopic Techniques Simple microscope - one lens Compound microscope - two lenses ocular and objective lenses White light microscopy bright field phase contrast interference dark field

Microscopic Techniques Ultra-violet light microscopy fluorescence microscopy fluorescent antibody technique - FA Electron microscopy transmission: regular and freeze-fracture scanning scanning tunneling Handout and Figure 3.3 p. 49 all types

Shapes (Morphologies)of Bacteria Figure 3.10 p. 53 cocci (coccus) bacilli (bacillus) spirilla (spirillus) coccobacilli (coccobacillus) Figure 3.11 p. 54 square prosthecae

Arrangements of Bacteria Two’s diplobacilli diplococci Chains streptobacilli streptococci

Arrangements of Bacteria Clusters (bunches) staphylobacilli staphylococci Four’s tetrads Cube sarcinae Figure 3.12 p. 55 how get arrangements

Prokaryotic Cell Structure Generic cell Start with the outer structures Then move inward Figure 3.13c p. 55 whole cell

Cell Envelope Capsule, slime layer, glycocalyx Cell wall Plasma membrane

Capsule, Slime Layer, Glycocalyx thick, regular Slime layer loose fitting, irregular Glycocalyx thin short hairs called fibrils

Capsule, Slime Layer, Glycocalyx Seen by negative staining Makes colonies moist, shiny, glistening Made of: exopolysaccharides (outside) peptides of D-amino acids

Capsule, Slime Layer, Glycocalyx Functions prevents phagocytosis of the bacterium therefore the organism escapes an immune defense attaches bacteria to surfaces glycocalyx of Streptococcus mutans forms plaque on teeth sucrose is converted to glucan which is glycocalyx

Cell Wall Composed of sub-units found no where else in nature Can produce symptoms of disease Is the site of action of some of the most effective antibiotics Determines Gram staining properties for the cell

Cell Wall Peptidoglycan Figure 3.19 p. 59 Gram (+) glycan portion is composed of 2 sugars peptido refers to the chains of amino acids only a few of the 20 amino acids are used can be D configuration diaminopimelic acid Figure 3.19 p. 59 Gram (+) Figure 3.21 p. 60 Gram (-)

Cell Wall Functions confers rigidity and shape to the bacterium holds the cell together in an hypotonic environment water enters the bacteria they would burst without a cell wall less important for halophiles (salt loving bacteria)

Cell Wall and Penicillin The mode of action of penicillin has selective toxicity. It prevents formation of the amino acid cross bridges in peptidoglycan. It works more better on Gram (+) organisms than Gram (-) organisms. Second mode of action is suspected Penicillin kills some bacteria without effecting the cross bridges.

Organisms with No Cell Wall Mycoplasma lack a cell wall have a stronger plasma membrane have sterols in their plasma membrane provides the extra stability

Plasma Membrane Surrounds the cytoplasm 60% protein 40% lipid No fatty acids No sterols Unit or bilayer membrane Fluid mosaic holds true

Plasma Membrane Functions contains enzymes for obtaining energy from nutrients is a semi-permeable barrier transports molecules passive transport simple diffusion facilitated diffusion active transport

Plasma Membrane Active transport Bacteria concentrate dilute nutrients from the environment. AT builds up high concentrations in the cell. Bacteria are oligotrophs. They are very efficient in active transport. AT necessary for survival in an environment where the nutrients are in low concentration.

Plasma Membrane Functions biosynthesis of DNA, cell wall parts, membrane lipids, etc. secretion of exoenzymes nucleases, proteases, lipases, etc. used to recycle large molecules by degrading them small pieces are taken up by the cell Figure 3.29 p. 66 Gram (+) Figure 3.30 p. 66 Gram (-)

Flagella Structure Figure 3.31 p. 67 parts Gram (-) organisms have all 4 rings, the L, P, S, M rings. Gram (+) organisms only have the S and M rings. major component is the protein flagellin

Flagella Arrangement of flagella Figure 3.32 p. 67 pictures monotrichous lophotrichous peritrichous amphitrichous

Flagella How they work Flagella require energy in the form of ATP from the proton pump. Flagella rotate one direction; the cell itself rotates in the opposite direction. Flagella rotate at over 1000 rpm. Figure 3.33 p. 68 rotation Flagella push bacteria through fluids. E. coli moves 20 body lengths per second.

Flagella Figure 3.34a p. 69 Bacteria in a uniform solution swim one second then tumble a fraction of a second swim one second again direction is random

Chemotaxis Positive - Figure 3.34b p. 69 swim toward nutrients swim longer before tumbling attracted by nutrients so swims longer to get there quicker tumbles less counter clockwise rotation

Chemotaxis Negative - Figure 3.34c p. 69 swims away from harm repelled strongly initially as it gets away it can afford to tumble swims less and tumbles more clockwise

Chemotaxis Bacteria sense nutrients or harmful substances. The primitive nervous system causes the flagella to rotate in the correct direction.

Chemotaxis Organisms with multiple flagella bundle flagella into one functional unit by rotating the flagella counterclockwise when they reverse the rotation to clockwise the flagella unwind so tumbling occurs

Other Types of Taxis phototaxis aerotaxis magnetotaxis benefits organisms that require light for photosynthesis aerotaxis benefits organisms that need lots of oxygen magnetotaxis benefits organisms that are microaerophiles

Cell Attachment Glycocalyx Pili (pilus) or fimbrae Figure 3.37 p. 70; Figure 3.38 p. 70 made of the protein pilin hollow covered with adhesins or at the ends various sizes used to establish infection

Genetic Information Nuclear area contains the DNA Chromosomes Figure 3.39 p. 71 Chromosomes 1-4 which are all identical circular, super coiled, double stranded molecules 1000X longer than the length of the bacterium histone-like proteins bind to the DNA Figure 3.40 p. 71 folding

Genetic Information Plasmids double stranded, circular, DNA molecules 0.1-10% the size of the chromosome Figure 3.41 p. 72 many copies per cell replicate independently of the cell chromosome not needed for the survival of the organism carry genes for drug resistance

Ribosomes Protein and RNA 70S 15,000 per cell on average anti-microbial agents effect 70S ribosomes not 80S ribosomes

Storage granules Nutrients stored in a form for later use High molecular weight polymers don’t disturb osmotic pressure of the cell Glycogen - stores carbon and energy Polymer of beta-hydroxybutyric acid Volutin - chains of phosphate metachromatic stain red with certain blue dyes

Endospores “Spore” Made by some Gram (+) bacilli Metabolically inactive Dehydrated Dormant for about 100 years Resistant to chemicals, heat, drying, freezing, radiation

Sporogenesis The making of the endospore It develops inside the vegetative cell. This occurs when amounts of carbon and nitrogen are low. A type of differentiation Figure 3.45 p. 75 process Figure 3.44 p. 74 spore inside cell

Germination The making of a new vegetative cell Initiates when water gets into the spore coat Re-hydration occurs Metabolism resumes

Endospore Structure Core Plasma membrane - surrounds core all the DNA protein synthesis apparatus energy generating system based on glycolysis dipicolinic acid - replaces water in the DNA helix Plasma membrane - surrounds core

Endospore Structure Spore wall - peptidoglycan Cortex - peptidoglycan with less cross bridges Coat - keratin like protein Exosporium - lipoprotein Figure 3.46 p. 76 released spore