It's not entirely clear what you mean by inactivating them, but if you just want them to stop growing the simplest thing is to just put them on ice. You could also harvest the cells by centrifugation and resuspend in some salt solution without nutrients and they will very quickly cease growth as well until you add the nutrients back.

You could also use a bacteriostatic antibiotic to stop growth and then wash it out to restore growth.

Dear Dr. Michael J. Benedik,

Thank you for helping me with this matter. I want to use this bacteria for calcite precipitating, so I want it to be inactive until the precipitation is required. Also, the bacteria have to preserve alive for future activities.

I appreciate your time and consideration.

The best method for preserving the microorganisms is to keep them at low temperature especially at -80°C or in liquid nitrogen as the case of the method of preservation of bacteria strains. This method depends on the use of a mixture of glycerol and bacterial medium (glycerol ratio ranges generally from 15 to 50%). Another method is freeze-drying, you can preserve bacteria for many years.

Dear Dr. Duried Alwazeer

Thank you for answering this question. I want to keep this bacteria inactive inside the concrete which its temperature is a function of the environment temperature and most of the time is over zero degrees of celsius. So do you have any suggestion about this condition?

As an alternative method, in the freeze-drying method, could bacteria remain inactive in the above-mentioned condition?

I appreciate if you suggest any references for the freeze-drying method?

Dear Ali Shoari,

I don't know exactly what are the assay conditions of your experiment but I think the freeze-dried form of bacteria is the most appropriate. It's interesting to test it.

Please read the following review.

Best wishes

https://www.sciencedirect.com/science/article/pii/S0167701206000583.

Dear Dr. Duried Alwazeer

Thank you for your help in this matter and the suggested reference which will be a great help. I will test it and share the results as soon as possible.