Team:Goettingen/week7-1


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#1 Selection / Swimming - 7th week

Swimming assay with trypton agar

Experiment:
A variety of agar conditions were tested: 1) 1% trypton, 0.3% agar, 0.5% NaCl; 2) 0.5% trypton, 0.3%, 0.5% NaCl; 3) like 1, but with additionally 0.5% glcose; 4) like 2), but with additionally 0.5% glucose. The swimming assay was performed as mentioned in methods.
Observations & Results:
All plates w/o glucose showed strong swimming over night. Therefore, glucose could be considered to be taxis-inhbiting.

Comined swimming assays

Experiment:
The strains from the previos experiments were combined on a single plate (several distinct drops on the same plate) to compare their swimming ability directly.

V06_13_1: Separation assay

Experiment:
Two strains with different promotor strengths were mixed 1:1 (OD600) and dropped onto a trypton plate. After several hours of swimming, the bacteria from the most outer edge of the swimming halo were picked and quantified to identify the ratio between the both starter-strains.
Observations & Results:
The plated did not show enough swimming, to ensure a positiv separation of the two strains. Further incubation times might be helpful.

V06_13_2: Comparing swimming assays

Experiment:
Two strains with different promotor strengths were mixed 1:1 (OD600) and dropped onto a trypton plate. After several hours of swimming, the bacteria from the most outer edge of the swimming halo were picked and quantified to identify the ratio between the both starter-strains.
Observations & Results:
On each quater of a 150 mm petri dish was one bacteria colony droped. Therefore, the swimming ability of all four strains could be compared directly.

V06_13_3: Chemotaxis assay with attractant

Experiment:
On minimal plates (only 0.3% agar and 0.5% NaCl) was one strain dropped. In a distance of about 2 cm was an attractant dropped, to induce directed chemotaxis.
Observations & Results:
No directed swimming or swimming at all was detectable. The aspartat attractant might not have reached the bacteria.

Directed swimming with gradient plates

Experiment:
To get a trypton gradient into the plates, they were poured in two steps. In the first step, the plate were shifted to a certain grad, to get more agar on one side to plate. In the second step, after hardening of the agar from step one, the plate is put back to normal and the other half is filled with agar. This all leads to plates, that have a linear gradient of chemoatractant in the agar. The strains from V06_11 are dropped on these plates to induce them to perform directed swimming.
Observations & Results:
No directed swimming was detectable

Preparation of diverse agar compositions

Experiment:
Four different agar compositions were produced: 1) 2x 400 mL: 1% trypton, 0.5% NaCl, 0.3% agar; 2) 2x 400 mL: 0.5% trypton, 0.5% NaCl, 0.3% agar; 3) 3x 400 mL: 0.5% NaCl, 0.3% agar; 4) 1x 400 mL: 0.5% NaCl, 0.3% agar, 0.25% aspartate.
Observations & Results:
No directed swimming was detectable