Difference between revisions of "Part:BBa K1639003"

Revision as of 07:49, 21 September 2015

TlpB

Helicobacter Pylori TlpB protein coding region. This part gives a negative chemotactic response to H+ ions. This makes bacteria capable of moving from acidic pH to more neutral pH levels.

Usage and Biology

Chemotaxis, movement toward or away from chemicals, is a universal attribute of motile cells and organisms. E. coli cells swim toward amino acids (serine and aspartic acid), sugars (maltose, ribose, galactose, glucose), dipeptides, pyrimidines and electron acceptors (oxygen, nitrate, fumarate).

E. coli's optimal foraging strategy

In isotropic chemical environments, E. coli swims in a random walk pattern produced by alternating episodes of counter-clockwise (CCW) and clockwise (CW) flagellar rotation (Fig. 3, left panel). In an attractant or repellent gradient, the cells monitor chemoeffector concentration changes as they move about and use that information to modulate the probability of the next tumbling event (Fig. 3, right panel. These locomotor responses extend runs that take the cells in favorable directions (toward attractants and away from repellents), resulting in net movement toward preferred environments. Brownian motion and spontaneous tumbling episodes frequently knock the cells off course, so they must constantly assess their direction of travel with respect to the chemical gradient.

Figure 1: Random and biased walks. Left: A random walk in isotropic environments. When the cell's motors rotate CCW, the flagellar filaments form a trailing bundle that pushes the cell forward. When one or more of the flagellar motors reverses to CW rotation, that filament undergoes a shape change (owing to the torque reversal) that disrupts the bundle. Until all motors once again turn in the CCW direction, the filaments act independently to push and pull the cell in a chaotic tumbling motion. Tumbling episodes enable the cell to try new, randomly-determined swimming directions. Right A biased walk In a chemoeffector gradient. Sensory information suppresses tumbling whenever the cell happens to head in a favorable direction. The cells cannot head directly up-gradient because they are frequently knocked off course by Brownian motion.

H. pylori is a Gram-negative bacterium that resides in thestomachs of over half the world’s population. Its gastric habitatcontains a marked pH gradient from the highly acidic lumen,which can reach pH 2, to the more neutral environment adjacentto the epithelial lining, which is typically pH 7. Based on genome sequence analysis, the H. pylori chemotaxismachinery resembles that of the well-studied model, E. coli,with a few notable variations including the absence of themethylation enzymes involved in receptor adaptation (Sweeneyand Guillemin, 2011). Sequence and Features