Effects of Pseudomonas aeruginosa PAO1 mutants on the growth of Listeria biofilms

Abstract

Listeria monocytogenes is a Gram-negative, rod-shaped pathogen with the ability to form resistant biofilms in food-processing environments. Substances secreted by Pseudomonas aeruginosa PAO1 have been found to naturally inhibit growth of L. monocytogenes biofilms. Transposon mutants were created to determine genes encoding for these substances. In this study, thirteen transposon mutants of P. aeruginosa PAO1 were evaluated to determine whether their ability to inhibit Listeria biofilms was changed. P. aeruginosa PAO1 wild-type and the thirteen mutants were grown in sterile Tryptic Soy Broth (TSB) for 48 hours at 37 ˚C. Cells were then separated by centrifugation and supernatants were sterilized by filtration through a 0.22 μm filter. These supernatants (PCM) were subsequently used to treat Listeria biofilms, which were grown for 24 hours at 30 ˚C in polystyrene microtitre plates. PCM prepared from Pseudomonas wild type and mutants was added to the biofilms followed by incubation for a further 24 hours at 30 ˚C. Controls included biofilms treated with TSB alone. Finally, biofilms were stained with crystal violet, and quantified in a FLUOStar OPTIMA microtitre plate absorbency reader. Treatment in all controls yielded dense biofilm formation, while the P. aeruginosa wild type PCM effectively reduced the biofilms grown in the polystyrene microtitre plates. Two of the original thirteen mutants exhibited impaired biofilm removal, with four other mutants showing a potential loss of biofilm removal characteristics. This indicates that these mutants posses the transposon inserted in a gene of P. aeruginosa that plays a role in Listeria biofilm removal. Inverse PCR will be used to identify the genomic location of the transposon in these two mutants.

32nd Annual Undergraduate Conference

A few weeks ago I found out about the 32nd Annual Undergraduate Research Conference being held at the University of Wisconsin in La Crosse. I jumped at the chance to participate, but when more people than spots applied to go, I spent a good three days working up an abstract, or summary, of my research. And guess what?! I get to go! Wheeeeee! What's really strange though is that my friends Joe and Dylan aren't going… D: I never thought in a million years that I would get chosen before them. I mean, in my mind I was thinking, "Okay, so 4 spots, and Joe's going to be going, so w00t 3 spots left." Their averages are amazing compared to my kind of crappy B-ish marks, and they‘ve been doing research for so much longer than me. I really did want to go though… so I harassed the Dean of the our department twice… and now I get to go. No wonder House is always a pain in the ass; he gets what he wants that way.

It's going to be help mid-April, and I'll be presenting a poster presentation. I kind of wanted to do an oral, but he specifically said he wanted to send poster presentations, so whatever. Doesn't matter, I'm going! I've never been to a conference before... so I'm not too sure what to expect besides other presentations. And, it's not just science-related topics either! There will be dramatic performances as plays or dances, and art students are displaying paintings. I'm so excited to go... just to see what other types of research are going on within other universities, and among other students my age. I know Dr. Schraft is excited to go too :) My school will be covering the costs, which is freaking awesome because tickets to go to the event are $200, plus all of the other travel-related expenses. What's even stranger is that I'm not feeling nervous about presenting my work... I know I'll get nervous as it gets closer, but still just floored at the idea that I'm really going. Truth is, I've been feeling really cooped up lately. I love my friends and family, and my peers at school and everything, but my city is so small, and there is so much I want to see. I only have a year and a half left before I graduate, and this summer I do my applications, so I'm seriously thinking about applying to a lot of different places not just within Canada. I'll of course be applying to Harvard even though my chances are something like -5%, so I'm also still thinking about applying in California, and to a couple schools in the UK. Not just for med school either, but for a master's program too. I'm still comparatively young, and I’m not expecting to get into med school after my first time applying (or second, really). But we’ll see. I’m still a die-hard believer in things happening for a reason, so I’ll go where I’m meant to, and I’ll see what happens. Things are just really, really exciting for me right now, and I’m loving every minute of it.

The Beginnings of a Blog

Well, hi. I'm Ashley. I've had a livejournal for the past few years now, but today I'm bored, so I'm testing out the difference between this and LJ. Besides, it might be a good time to make a new blog since my LJ is stuffed with my old, and probably melodramatic, high school rants about guys, grades, and other random things. I'll play around with the layout and see if I like it enough to stick around.