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  • JVGen
    Member
    • Jul 2016
    • 42

    #1

    Questions Regarding 10 kb Amplicon Sequencing & Paired-Read Assembly

    Hello Everyone.

    I am sequencing viral genomes by PCR-amplifying them, and then sequencing them on the Illumina platform with 150 x 2 coverage. I generally get about 50,000 reads for each sample using this method.

    My amplicon varies in size: this is a retrovirus and is highly mutated, often containing large deletions. The maximum amplicon size is 8.9 kb (unless an insertion has occurred, which could increase the size). I have a ballpark idea of the expected amplicon size, as I screen by gel electrophoresis prior to sequencing. Regardless, the goal is to generate a workflow that accurately assembles the reads into the correct contig size.

    For these reasons, I am trying to assemble them using a de novo method. I have tried creating a workflow with Geneious, but keep running into problems. I can't get the get the expected amplicon to assemble into a single contig file. Sometimes it is broken into many different contig files, sometimes pieces are just missing.

    I'm working on a desktop mac with 32GB of processing power, so these assemblies take a lot of time, making troubleshooting and playing with parameters a grueling process.

    Is anyone familiar with Geneious, or used another program for a similar application. We don't have a bioinformatician in my lab, and I have very limited experience in coding, so user-friendly programs would be ideal. Any help would be greatly appreciated.

    Thanks!
  • nucacidhunter
    Jafar Jabbari
    • Jan 2013
    • 1250

    #2
    Geneious has excellent support team and I would suggest you to contact them.

    Comment

    • JVGen
      Member
      • Jul 2016
      • 42

      #3
      Originally posted by nucacidhunter View Post
      Geneious has excellent support team and I would suggest you to contact them.
      Been speaking with them for months. They are helpful but slow to respond - takes about a week to hear back, and I've usually moved on to new issue.

      Comment

      • pmiguel
        Senior Member
        • Aug 2008
        • 2328

        #4
        50,000 reads (read-pairs?) would be on the order of 7.5-15 million bases of sequence or 750-1500X coverage. With most assembly engines I've worked with, you see worse results if you push beyond the 200x-500x coverage level.
        We use SPADES for this sort of assembly, but discard reads that would take us above 500x coverage.
        --
        Phillip

        Comment

        • JVGen
          Member
          • Jul 2016
          • 42

          #5
          Originally posted by pmiguel View Post
          50,000 reads (read-pairs?) would be on the order of 7.5-15 million bases of sequence or 750-1500X coverage. With most assembly engines I've worked with, you see worse results if you push beyond the 200x-500x coverage level.
          We use SPADES for this sort of assembly, but discard reads that would take us above 500x coverage.
          --
          Phillip
          Hey Phillip, thanks for the response. The core that I use has SPADES and gives me de novo assembled contigs, but I'm leery to use them because they won't share their assembly parameters with me. They want to publish on it first.

          So instead, I'm using the reads and running the assembly myself. I started using B.B.'s DeDupe and Normlization yesterday after reading your response, but I haven't figured out what coverage the program reduces reads to...

          Maybe I should spend some time figuring out Spades. I just have no coding experience, so there's going to be a big learning curve.

          Comment

          • nucacidhunter
            Jafar Jabbari
            • Jan 2013
            • 1250

            #6
            Originally posted by JVGen View Post
            Been speaking with them for months. They are helpful but slow to respond - takes about a week to hear back, and I've usually moved on to new issue.
            I used to get response in 24 hours.

            Comment

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