Team:LMU-Munich/Data/Knockout
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Revision as of 12:14, 26 September 2012
The LMU-Munich team is exuberantly happy about the great success at the World Championship Jamboree in Boston. Our project Beadzillus finished 4th and won the prize for the "Best Wiki" (with Slovenia) and "Best New Application Project".
[ more news ]
Knockouts of germination genes
We induced our germination-mutant strains to sporulate in Difco sporulation media. We quantified the cells and spores per milliliter of each culture using a Neubauer cell counting chamber. Then we plated known dilutions of culture, and measured the germination rate of mutant spores in a germination assay (see Protocols). The germination assays were carried out several times, and yielded similar results each time. For these results, see "Mutant Germination Rates" graph.
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The germination rates of B. subtilis germination mutants. All germination rates are relative to wild type 168 (WT168), our positive control. The mutant spo0A::tet is unable to form spores, and should therefore show no germination (our negative control). Mutants used were:
WT168: Wild-type 168
spo0A::tet: A sporulation-deficient strain
B29: cwlD::kan, sleB::mls
B30: gerD::cm, sleB::mls
B32: cwlJ::spec, cwlD::kan
B40: cwlD::kan, sleB::mls, cwlJ::spec
B41: cwlD::kan, sleB::mls, gerD::cm
B42: cwlD::kan, cwlJ::spec, gerD::cm
B43: gerD::cm, sleB::mls, cwlJ::spec
B46: cwlD::kan, cwlJ::spec, gerD::cm, sleB::mls
B47: gerD::cm, sleB::mls, cwlJ::spec, cwlD::kan
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The plate growth demonstrates the inability of our mutant spores to germinate. We can say that fewer than 1 out of 3x10^7 spores of strains B40, B41, B43, B46, and B47 germinated.
The plates below demonstrate the procedure of plating for the germination assay. Plates here include those containing heated and unheated cultures, and show both germinable spores (B42) and spores unable to germinate (B47). These plating experiments allowed us to quantify the number of ingerminable spores in each culture.
The purpose of plating both heated and unheated cultures was to demonstrate the viability of the unheated cells in each culture. This makes evident that the lack of colonies on heated plates is not due to the inability of the strain to grow, but from the inability of spores to germinate into vegetative cells capable of growing.
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Plates of germination mutants. Plates contained heated (to kill live cells and leave only spores to germinate) cultures and unheated (where colonies may come from germinated spores and the live cells) cultures. The mutant spo0A::tet is unable to form spores, and should therefore show no germination (our negative control). The mistake of photographing empty plates against a background of spots was realized after plates had been discarded. Presence of colonies is noted below, for clarity. Mutants used were:
WT168: Wild-type 168; Heated plate: colonies present; Unheated plate: colonies present
spo0A::tet: A sporulation-deficient strain; Heated plate: no colonies; Unheated plate: colonies present
B42: cwlD::kan, cwlJ::spec, gerD::cm; Heated plate: colonies present; Unheated plate: colonies present
B47: gerD::cm, sleB::mls, cwlJ::spec, cwlD::kan; Heated plate: no colonies; Unheated plate> colonies present
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Germinable spores per mutant. The table shows the maximum number of spores from heated cultures plated which yielded zero colonies. In the case of B30, the germination assay was performed only once, and as visible in the above graph "Mutant Germination Rates," contained viable, germinable spores. The numbers shown here are the highest number of spores plated, excluding B30. This means that we do not have data for higher concentrations of spores which would suggest any spore germinability. The mutant strain B42 contained germinable spores when 4x10^7 were plated, but contrarily, zero germinable spores were found when 9.83x10^7 spores were plated in another round of the germination assay.
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