I decided to let them simmer a little and here is the reminder (note the poor copy/paste job with Knut’s name in a different font size than the rest of the message).

From: ella <ella@bitconferences.com>

Subject: Re: Re: 099-Call for Speaker at 2nd Annual Symposia of Bacteriology andInfection (SBI-2012)

Date: November 14, 2011 12:31:37 AM PST

To:

Dear Knut Buttnase,

It is long time without hearing from you, how is everything going?

Have you finished your abstract and biograhy? If yes, could you send them to us? Attached please find the template. Thank you for your support.

Your early reply will be highly appreciated.

Best regards,

Ella