2. Gram Staining The Gram stain depends on the ability of bacteria to retain a purple color (based on cellular envelope). Gram Negative More numerous Does not retain dye coloring purple dye alcohol red dye red purple
3.
4.
5.
6.
7. Cell Membrane = Inner Membrane GRAM POSITIVE Thick cell wall that protects the membrane from high internal turgor pressure Made of peptidoglycan called murein Mureindoes a lot! Protector, provides rigidityand shape Not the only determinant of bacteria cell shape Provides hydrophilic layer Murein is unique to bacteria making it a good target for antibiotics through preventing murein synthesis.
8. Osmotic Pressure Murein allows for the cell to survive under different osmoticpressures. When lysozymes hydrolyze part of the murein layer the cell acts more sensitively: Low osmotic pressure outside the cell: lyses High osmotic pressure outside the cell: the cell changes shape (rod to sphere) In gram negative this is called protoplasts In gram positive this is called spheroplasts
9. High osmotic pressure Low osmotic pressure Shape Change Low osmotic pressure outside the cell lyse High osmotic pressure outside the cell shape change
11. Cell Membrane + Outer Membrane GRAM NEGATIVE Thin murein layer connected to the outer membrane by a lipoptein Periplasm - space between the two membranes The outer membrane contains LPS LPS is unique to prokaryotes! lipid A Causes fever and shock Core O antigen Immunogenic/toxic, highly variable Hydrophilic polysaccharides on O antigen keep out hydrophobic compounds just like in gram positive
12. LPS Structure Core O Antigen Lipid A Portion that sticks out of cell Hydrophilic
15. Transportation GRAM NEGATIVE The outer membrane contains special channels called porins that allow hydrophilic compounds such as sugars, aa’s, and ions inside the cell (nonspecific). Large molecules – rely on active transport and energy usually coupled with inner membrane transport
16. Capsules and slime layers Found in both +/- Capsule: slime attached to cells Slime layer: looser layer Role: Enables bacteria to adhere to surfaces Bacterial defense against phagocytosis Prevents desiccation(dehydration)
17. Flagella Flagella – helical filaments that rotate and act as propellers Composed of three parts: filament connected via a hook to a basal body.
19. Filament - composed of a single protein, flagellin Hook – connects filament to the cell Basal Body – composed of 15 proteins that aggregate to form a rod
20. Flagella – (Regulated) Process Basal body assembled and inserted into cell envelope Hook is added Filament is assembled progressively by the addition of new flagellin subunits to its growing tip. Flagella grow from the tip outward with a hollow channel where the flagellin molecules are extruded A regulated process – inhibitor secreted once basal body is inserted
21.
22. Pili Common in gram-negative bacteria Functions include: Gene transfer Motility Adhere to mucosal surfaces Inhibit phagocytic ability of white blood cells
23. Motility Pili are straight rods – do not rotate! “Twitching Motility” – move by pulling themselves across a solid surface Growth Grow from the inside of the cell outward unlike flagella Pili vs. Flagella
25. The Nucleoid Contains DNA consisting of a large circular chromosome With exceptions No membrane With exceptions, an example is: Plantctomycetes
26. DNA Packaging Long DNA is tightly folded into nucleoid Condensing DNA requires high ion concentration and DNA binding proteins Supercoilingof DNA also aids in packaging
27. DNA Supercoiling Supercoiled circular DNA lowers the energy barrier for strand separation Balance of two enzymes: DNA gyrasewhich does the supercoiling Topoiseomerase I which does the uncoiling
28. Genome Comparison Prokaryotic Range 580,000 base pairs – 10 million base pairs Eukaryotic Range2.9 million base pairs – 4 billion base pairs
29. DNA Copies & Plasmids Often multiple chromosome copies are seen in the cell because of rapid growth Decreasing growth rate single nucleoid Plasmids carry extrachromosomal material “Disposable”
30. Cytoplasm Crowded inside the cell Viscous (gel-like) Chemical reactions within a bacterial cell take place in an environment totally different from what is common in test tube studies
31. Gas Vesicles Structures filled with gas similar to that of the environment Vesicles surrounded by protein shell Allow buoyancy for the cell so it can set level in water column (and get the right amount of light) Ultimate purpose: control buoyancy for photosynthetic bacteria
32. Other Internal Structures Other structures found in bacteria and archaea play roles in: Photosynthesis Chemoautotrophy Carbon fixation Gorwth on certain substrates Magnetosomes (bacteria contain tiny magnets and they can orient themselves by responding to the magnetic fields on earth)
