The plasmid extraction from G- bacteria was not different , You can use promege kit for extraction of plasmid from any  bacteria 

Thank you sir........I already tried many methods....But Vibrios have very low copy number and hence I am getting very faint bands

@ Reshma,

Now I understand the problem is due to low copy number. It likes Agrobacterium which we use for plant genetic transformation. It generates low copy number of plasmids (binary vector). Miniprep shows faint band too. Some people have to do Megaprep to obtain good amount of it. Some people transfer the isolated plasmid into E. Coli to obtain high-copy number of the plasmid. I am not sure, but can the plasmid (small amount) isolated from Vibrios be transfer into E. Coli to produce high amount of it?