Could anyone please explain how plasmid incompatibility mechanism work in transformation in molecular cloning?
There are several key sequences in a plasmid, and one of them is the origin of replication (ori). The ori carries information about how many copies of the plasmid will be in a cell, some plasmids are low-copy (5-20 per cell) or high-copy (700 per cell). To do this, the ori's function is to recruit the necessary proteins that will allow the plasmid to replicate inside of the cell. If you transform a cell with two different plasmids that have the same ori (or two oris from the same incompatibility group) they will be competing for the same proteins within the cell, and you can get unpredictable results. If they are high-copy number origin maybe you can get a double transformant, but maybe you don't get transformants at all, depending on your experiment and the plasmid in question. However, if they are from different incompatibility groups, meaning that each plasmid will recruit a different set of proteins, they should co-exist in the same cell.