Lect13-14-KR - Bacterial chemotaxis PMB/MCB112 September...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Bacterial chemotaxis PMB/MCB112 September 29, 2010
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chemotaxis the movement of a cell toward or away from a chemical signal amino acids, sugars, oxygen, electron acceptors Insert capillary:
Background image of page 2
Soft agar + compound that 1) attracts bacteria and 2) can be metabolized Cells inoculated at center metabolize the compound and swim out in a circle, up the gradient that they have created . Assay only works if bacteria can metabolize the attractant! Takes 6-48 hours, includes growth Agarose plug containing attractant is placed in center of a liquid suspension of bacteria. Cells accumulate in a bright ring surrounding agarose plug. Does not require growth, response occurs in minutes.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
chemotaxis is a biased, 3-D random walk cells normally alternate between runs and tumbles, generated by CCW (run) and CW (tumble) flagellar rotation if a cell is swimming toward a greater concentration of attractant, its motion is biased toward runs by keeping the flagellum rotating CCW for longer times
Background image of page 4
Why study chemotaxis? 1) Mutants have clearly observable phenotypes, but chemotaxis and motility genes are not usually essential aka: We can make many different mutations that DO NOT KILL THE CELL 2) Chemotaxis signaling is incredibly sensitive-cells can respond effectively to very small changes (<1%) in attractant concentration 3) Chemotaxis signaling is also effective over a wide range of attractant concentrations aka: a change of +/- 1% of the ambient concentration can be detected at ambient concentrations of 10 -7 to 10 -3 M (2) and (3) enable bacteria to sense a slightly “better” environment over a very wide range of backgrounds
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chemotaxis system senses attractants or repellents and transmits this information to the flagellum Sensor proteins are m ethyl-accepting c hemotaxis p roteins (MCPs) – external (periplasmic) domain binds attractant – HAMP domain transmits information of ligand binding to rest of protein – methylation region functions in adaptation – signaling region binds CheW and CheA
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 20

Lect13-14-KR - Bacterial chemotaxis PMB/MCB112 September...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online