So important questions for me, please help...

Question

Naturally, bacteria that can receive DNA from the outside and transform are called competitive cells. Competence is regulated in bacteria transforming in nature and specific proteins play a role in the uptake of DNA. Not all bacteria can transform. Although it is thought that their number is more in nature, about 80 bacteria that have been able to transform have been discovered so far. According to this;

1. Why only some bacteria in nature can develop competence and transform?

2. How do you know if a bacterium given to you is naturally competent?

3. Among Bacillus bacteria, which are capable of natural transformation, approximately 20% of the cells can be competitive and remain competitive for hours, whereas in Streptococcus, 100% of the cells can only become competitive for a short time. How would you explain this situation?

Answer 1

Basically you have to understand what exactly being competent entails in terms of a bacteria, when a bacteria is competent it means the cell wall is actually porus, and as you can imagine that porus cell wall is an active hindrance for bacterial survival, which is why more species of bacteria are not evolved to be naturally competent. Another limiting factor is presence of type iv pili this is the pili that binds to extra cellular DNA if the species does not have this pili it can not be competent naturally.

Now for the second question the first check is of course see if the type iv pili is present and if it is then the second check if the bacteria is spore forming or not. spore forming bacteria are more often than not naturally competent. Also for the final check you can cause stress in the microbial culture by nutrient deprivation and then introduce a plasmid of known size. Following this the culture to a new media and then extract the DNA from them and run them on gel electrophoresis, if the cells are competent you will see clear bands for the presence of plasmid.

The third answer is actually very tricky, it requires on one of hypothesis of having the competence. It is believed naturally competent bacteria use naked DNA to help repair chromosomes, so the necessity of competence is linked with two factors first the stress and then the next how much the repair mechanism takes time. It is possible that in bacilus this more costly than time consuming that in strep.

citation:Johnston, C., Martin, B., Fichant, G. et al. Bacterial transformation: distribution, shared mechanisms and divergent control. Nat Rev Microbiol 12, 181–196 (2014). https://doi.org/10.1038/nrmicro3199