Question

What is the purpose of the 200 bp internal positive control in the BAX system?

How could a PCR-based method be modified so that nucleic acid is only amplified from viable cells?

Answer 1

1) BAX system is used nowadays in food and beverage industry. It is a powerful, molecular- level pathogen detecting system. During PCR, specific primers are used that targets only the sequences of the target organisms and at the same time 200bp internal positive control is used to reduce any errors during the whole process. This will eliminate any possibilities of false negative and positive results.

2) PCR- based method can be modified so that nucleic acid is only amplied from viable cells by using " activity labile nucleic acid- modifying compounds" that is ALC approach. It has two compounds: one is a DNA- intercalating moiety and the other one is a cross- linkable moiety. These two compounds are connected through a linker which is cleaved by viable cells' biological activity. Thus the azide group is removed from the DNA- intercalating moiety and the cross-linkable moiety will be unable to cross link with DNA. This will prevent modifications in DNA in viable cells and increase the ability of amplification. Modification of DNA occurs in inactive cells due to the non- removal of the cross- linkable moiety from DNA. This will eliminate the chance of non - viable cells to get amplified.