Which format is better when providing DNA sequencing samples?

We recommend customers to provide the bacteria and we extract the plasmid to ensure the DNA sample is stable. It's also accpetable if DNA samples are provided by the customers. However, we need to check the purity and quantity of samples. If the amount of customer supplied DNA is insufficient, we need to amplify the plasmid. A conversion fee may be required. The quality of DNA varies from different extraction methods. DNA purity and quantity should be checked when sequencing samples are PCR products. PCR products must be re-extraction by gel cutting, otherwise they will not be able to gurantee the sequencing results.