Previously we have given nutritional stress to mycobacterium smegmatis by growing them under low glucose concentration. Followingly, We have checked the level of synthesis of ppGpp and its responsible gene to nutritional stress. Please check our infection immunity and current science papers for more details.

Hello Dr. Tarik Nassar, I agree with your points that High level of expression actually causes metabolic limitations. Also recombinant protein expression (RPE) like processes actually create a condition which cell feels in terms of different kind of stress like heat shock, oxidative stress etc. Along with this it is also a universal truth that different E.coli strains have different strengths to produce total recombinant proteins. I am quite aware of these facts and have experienced them during my work.

My concern is to go one step ahead and find out why cell sees the recombinant protein expression, in the form of stress. Basically its the regulatory network of E.coli which becomes aware of protein production as something unusual thing happening inside the cell and sends signals through expression of different genes. Thus giving cell a feel that actually something wrong is going on inside the cell.

So different research groups have done different genome engineering or targeted gene manipulations which have actually lead to increase in RPE.

Here I am trying collect those ideas/Experiences/references which people have tried to solve the problem of RPE to some extent at least.

Hello Dr Tapan Mukherjee, it is a well known fact and was actually proven decades ago that nutritional stress in different microorganisms lead to development of stringent response which is signaled by the alarmone (p)ppGpp. And this actually controls the expression behavior of a very large number of genes.

While in my question I am more interested to know about those modifications which have been done to reduce the stringent response. Some scientific groups have done very specific manipulations in genome which actually breaks the connection between stringent response and ppGpp, like there are studies on ppGpp deletion mutant strains. Like this there are various other modifications which have been done in the past research, which helps in relieving the stress levels inside microorganisms during RPE. I am trying to collect those informations, any of your suggestion in this direction will be quite helpful.

Thanks

In E. coli infact this is a challenge for RPE gene. Note normally heat stress or osmotic stress do not give satisfactory results. You will get good results if you use oxidative stress.