Colonies of Bacillus Subtilis
Colonies of Bacillus subtilis on a Petri dish can grow under controlled conditions. By varying agar concentration (which permits the control of the hardness of the medium), and the nutrient concentration, the response of the colony to external stresses can be studied. The different morphologies appear in the following growth conditions:
- High nutrients level, hard medium
- Eden-like growth
- High nutrients level, semi-soft hardness of medium
- Periodical growth forming concentric rings
- High nutrients level, soft medium
- homogeneous, disk-like growth
- Low nutrients level, hard medium
- DLA growth
- Low nutrients level, soft medium
- DBM growth
A complete morphological diagram can then be drawn by varying growth conditions.
These different morphologies can be obtained from a reaction-diffusion model. This kind of model is useful to asses which mechanisms are relevant for the different morphologies. The complete morphological diagram can be obtained by using two fields, density of bacteries and nutrient concentration, and taking into account that bacteries can increase motility in response to adverse external conditions. That means that diffusion in the medium and the response of bacteria are the relevant factors in this particular case.
Read more about this topic: Bacterial Patterns
Famous quotes containing the word colonies:
“I have often inquired of myself, what great principle or idea it was that kept this Confederacy so long together. It was not the mere matter of the separation of the colonies from the mother land; but something in that Declaration giving liberty, not alone to the people of this country, but hope to the world for all future time. It was that which gave promise that in due time the weights should be lifted from the shoulders of all men, and that all should have an equal chance.”
—Abraham Lincoln (1809–1865)