Loose Ends on Chapters 3,5,6 SummerMicrobiology

Spore survival Dipicolinic acid and Ca++ account for 15% of the total spore mass Dipicolinic acid theoretically may contribute to the stability of the nucleic acids which is a contributory to the spore’s survival- The Ca and the dipicolinic acid may enhance the activity of DNA binding proteins that are vital to the spore’s ability to resist radiation Calcium contributes to the ability of the spore to resist destruction by oxidizing agents and dry heat – also steam

Spore Structure

Seven Steps and More in Spore Formation Revisited Stress or unfavorable environmental conditions Replication of DNA Membrane begins to form to separate cells – Forespore septum begins to show the formation of the forespore Membrane continues to grow and engulfs the DNA into the forespore

Spore formation Continued The cortex is laid down and Calcium and dipicolinic acid are accumulated here Protein coats then form around the cortex The exosporium and then the spore coat are made to surround the spore At this point the spore structure is completed

Spore Release Lytic enzymes destroy the sporangium releasing the spore This process takes about 23 hours in B. subtilis

Flagellar Structure The M Ring is anchored in the cel membrane of the bacterium. A shaft that is attached to the hook and flagellum extends form the shaft. In Gram Positive cells the S ring is attached to the cell wall and does not rotate In Gram Negative cells, the P and L rings act as a bearing for the rotating flagellum

Flagellar Motor Proteins Mot A and Mot B These form a proton channel for the establishment of a proton gradient The Motor proteins also assist in the anchoring of the complex to cell wall peptidoglycans Fli G is the motor protein that generates flagellar rotation

Rotational symmetry of the C ring and a mechanism for the flagellar rotary motor Dennis R. Thomas, David Gene Morgan, and David J. DeRosier Proc Natl Acad Sci U S A August 31; 96(18): 10134– PMCID: 17855

Reference The cytoplasmic component of the bacterial flagellar motor. I H Khan, T S Reese, and S Khan Proc Natl Acad Sci U S A July 1; 89(13): 5956–5960

Chemoreceptors MCP – Methyl accepting chemotaxis proteins Localized in patches at the ends of the bacilli in E. coli React to stimuli through a series of steps utlizing proteins

Concepts Conformation change in protein structure Methylation of proteins Phosphorylation of proteins

Increase in nutrient binding Environmental stimulus – nutrient molecule Nutrient molecule in the gradient binds to the MCP protein( change in conformation) Che A is dephosphorylated – loses a phosphate Counterclockwise rotation occurs in the bacteria

No nutrient detected in the environment No nutrient binding Che A is phosphorylated( gains a phosphate group) Phosphate is then donated to Che Y Interacts with Fli switch to causes clockwise rotation or tumbling – random and undirected

Two Component Phosphorelay System Two Component Phosphorelay System is similar in response to oxygen, light, hear and osmotic gradients.

Active Transport Movement against the concentration gradient from low concentration outside of the cell to higher inside the cyotplasm Requires the input of energy to drive the reaction forward

Active Transport and ATP- Binding Cassette Transporters ABC Transporters Large group of transporters Two hydrophobic domains in the membrane and two nucleotide binding domains at the cytoplasmic surfaces The membrane spanning portions form a pore The nucleotide binding domains bind ATP for the hydrolysis of ATP to produce energy to drive molecules through the membrane

Salmonella ABC transporter

E. Coli and active transport The sugars arabinose, maltose galactose, and ribose are transported by this mechanism in bacteria Also amino acids may pass through the cell membrane in this manner

Porins Porins are channels located in the outer membrane of the Gram Negative bacteria

Omp F

Siderophore

Active transport Uniport – One ion or molecule moves against the concentration gradient Symport – A concentration gradient established by an ion, drives solute transport of another molecule against the concentration gradient Antiport – Sodium is pumped outward in response to an inward movement of protons

Importance of this mechanism The sodium pumped to the outside of the cell is also used in transport It binds to the outside of a different transport protein. When it binds it changes the shape of the protein The protein is then able to bind to molecules to move them into the cell

E. coli Has multiple transport systems for many nutrients The diversity of these transport system provides the ability to survive in diverse environments

Group Translocation A molecule is transported ito the cell while being chemically altered This is energy dependent

PTS Best characterized system is the PTS Phosphoenolpyruvate: sugar phosphotransferase system Transports sugars while phosphorylating them

Components Two enzymes( EI and EII) Low Molecular weight – heat stable protein( HPr)

Steps High energy Phosphate is transferred from phosphoenolpyruvate to EII with the help of EI and HPr The sugar molecule to be transported is phosphorylated as it goes across the membrane by EII EII is specific for the sugar that it transports

PTS