how many plasmids a bacteria can have ?

Question

how many plasmids a bacteria can have ?

Answer 1

It doesn't depend only on the species. Plasmids replicate autonomously (compared to the chromosome). In order to achieve that it has a replicon (an origin of replication plus some genes that take part in the replication). Some replicons (usually the term used is just "origins") give a high copy number, meaning that the plasmid that carries them can be present as even 500 identical copies in a cell.

If you want different types of plasmids, then their mechanism of replication and selection marker must be different. Otherwise they will start competing with each other for replication and depending on the growth conditions you could have one being lost or have a mixed population with some cells carrying one type of plasmid and some carrying the other.

In theory, provided that you have plasmids with origins that are not in the same group and have different selection markers, you could have as many as you want. In practice you can easily have 2 different types of plasmids but if you want more then you have problems finding compatible plasmids, but you also put a quite heavy burden on the cells (having to deal with many antibiotics).
Also there is plasmid variation within the cells, so if you say for instance that the copy number is 60, it is actually an average value which fluctuates in the best case between 50-70.
So if you want a system of genes on different plasmids there could be an issue of stability/noise due to the fluctuation in copy number.

Thus in practice you usually go up to 2 different types of plasmids, though it is feasible to go up to 3.

Answer 2

The end codon of the protein replaced into in all probability no longer cloned into the plasmid. So, whilst the bacterium produces the protein it does not end on the tip of the cloned series, yet keeps translating. If the genes is recloned onto the vector WITH the tip codon, the priority would be solved.

Answer 3

any number
depends on the species