Question

1) As a bacterial cell transmitted a new host is likely to encounter a range of non-optimal conditions. For example, it may be exposed to damaging or toxic physical and chemical conditions. It will need to adapt if it is to survive. Outline what these physical and chemical properties could be and how bacteria will adapt to survive in these conditions.

2)Describe an example of the mechanisms by which Escherichia coli senses and detoxifies hydrogen peroxide?

Answer 1

1.- The main difficult conditions bacteria find while in process of transmitting into a new host are low moisture, sunlight radiation and pH and osmotic changes. Most of the bacteria use small specific mechanism to counter each one of these threats but their action is not that strong so it will only work for minor changes, for example, they produce temperature shock proteins that protect them from temperature changes, they secrete osmotic solutes to avoid losing too much water in case of osmotic shock, they enhance their DNA repair mechanism to avoid dying when exposed to UV radiation.

Now, there is a more strong response that bacteria undergo that can actually protect them from strong environmental changes and not only weak changes like the previous mechanisms, and that is forming endospores. They enclose themselves, isolating themselves from the environment and reducing their metabolic actiity to the minimum, but this can only be done by certain species

2.- E. coli peroxide sensing depends on a specific protein called OxyR, this is a DNA binding protein that prevents katG from being expressed. In the presence of oxidative agents like peroxyde the OxyR cystein residues get oxidized, this changes the conformation and allows for katG to be transcribed. This is the gene for catalase peroxidase, which is an enzyme that will transform peroxyde into water