I would ask the reader what they really know about bacteria and its forms, and try to lay in a few facts here and there. You want to try and include a general "summary" of facts that your will be presenting throughout your article. See how you can relate bottled water to bacteria and really build off of that topic trying to pull in or hook the reader with interesting fact and things that can be applied in a life situation that will provide a benefit for the audience that you are targeting. I really hope this helps, and I am sorry I couldn't tell you exactly what to say but I hope that you take my answer into consideration! :)