[Microbiology] "cryptic plasmid?!"

[Tânia Caetano]

Hello

Anyone knows if it is possible a bacterial cell with a plasmid  
survive without it? In other words, there is any case of a plasmid  
essential to the bacterial growth (environmental sampling)? And if it  
is the case we can apply the term cryptic ? Because I thought cryptic  
was just a plasmid with unknown function.

thanks
biotc