Do plasmids work in bacteria? - (Nov/22/2010 )

If plasmids inside a bacteria are just non-essential rings of DNA, does that mean that the DNA on the plasmids do not do any effect to the bateria? In other words, the DNA on the plasmids of a bacteria is not read/transcribed/translated?

If this is so, why would a recombinant plasmid with antibiotic resistance work in a bacteria against an environment with antibiotic?

Of course they are transcribed and translated. The plasmids confer a selective advantage to the cells that carry it in a selective environment. If you leave a bacterial suspension carrying a plasmid to grow into stationary phase in a medium without antibiotic the bacteria will loose the plasmid, meaning the bacteria without plasmid will outgrow the bacteria with plasmid. Nothing in a bacterial cell is completely non-essential.