Pili
What is the primary purpose of many pili?
Attachment
What do the "O" and the "H" in E. coli O157:H7 refer to?
The "O" refers to the O-antigen of LPS (#157)
The "H" refers to the flagella protein (#7)
What is a capsule?
A thick mucous-y layer that surrounds bacterial cells and is used for protection.
Which of the following is the best protection for a bacterial cell against immune cells in the human body?
A. Pili
B. O-antigen
C. Capsule
D. Flagella
C. Capsule
What property is unique to the specialized type of pili called nanowires?
They conduct electrons.
What is chemotaxis?
Chemotaxis is swimming in response to stimuli (e.g. run and tumble).
What does the capsule protect the cell from? (Hint: 2 things)
Protects bacterial cells from immune cells.
Protects bacterial cells from environmental conditions (e.g. prevents drying out; slows diffusion of chemicals).
How fast can the flagella rotate?
Up to 300 turns/sec.
Describe static and dynamic pili.
Static pili are simply assembled and typically used for attachment.
Dynamic pili are assembled and disassembled, they can be extended and retracted. They are used for several different things, including movement.
What provides the energy to rotate the motor of a flagella?
Flow of protons (proton motive force).
What happens to most pathogens when they lose their ability to produce a capsule?
They are no longer able to invade a host and cause disease.
Twitching motility.
Describe how bacteria use pili for movement.
Pili have attachment proteins on the ends that allow them to attach to specific sites (adhesins). Once they're attached, the cell can retract its pili back into the cell, and move toward the attachment protein.
Once it has moved to its destination, it can send its pili back out and repeat the process.
Pelagibacter is a type of bacteria that is found in ocean water. However, this bacteria doesn't need flagella to move. Why is that?
Pelagibacter utilizes ocean currents for movement purposes.
What is the name of the DNA transfer experiment that explored capsule-free versions of Streptococcus pneumoniae (causes a pneumonia-like illness) as a potential vaccine?
The Griffith experiment.
What is a spirochete?
A type of bacteria whose flagella-like structure is located in the space between membranes (looks like a G- cell with 2 membrane layers). Instead of having a thin flagella extending out from the cell, the whole bacterial cell body rotates. This allows the cell to swim much better, especially through viscous fluids/tissues.
Describe the process of conjugation.
Conjugation is when one cell (the donor) transfers DNA to another cell (the recipient). The donor produces a pilus, attaches to the recipient cell, pulls the recipient cell close, opens up a pore between the two cells, and transfers DNA. These pili are dynamic because they both extended and contract to draw the recipient cell to them.
Your immune cells are less likely to recognize Borrelia (the Lyme Disease bacteria) because it has what unusual characteristic?
Flagella located between two membrane layers.
A mad scientist is trying to use biological warfare to take over the world. However, he fell asleep in his microbiology class while they were discussing capsules. He decides to use the bacteria that causes anthrax, Bacillus anthracis, as his weapon against humanity, but he wants to make it stronger than just your run of the mill anthrax. He decides to mutate the capsule synthesis genes, thinking it would make it harder for human immune cells to find... how does the mutated Bacillus anthracis behave?
A mutation in the capsule synthesis genes of Bacillus anthracis makes the bacteria completely harmless.
In what direction do the flagella rotate to move toward an attractant? In what direction do they rotate that causes the bacteria to "tumble"?
Counterclockwise rotation moves cell towards attractant.
Clockwise rotation stops forward motion, so cell tumbles and changes direction.