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Howdy all! Why yes, I did post again…

Today’s topic spawns off of a discussion I had with a friend a while back about agar plates, as they had never really heard the basics of what a petri plate is and why it is so crucial to a modern microbiologist’s work (despite being “low tech”).  As such, lets take a brief run through of agar plates.

Of course, when I was in grade-school, this is what I thought of when I heard Petri plate.

Example of agar agar in food stuffs.

So, first lets hit the history of agar plates in true Alton Brown style.  Agar, or if you’re being picky “agar-agar”, is a substance isolated from red algae, aka: seaweed.  This polysaccharide (a polymer of galactose, I believe) provides stability to the algae’s cellular walls and just happens to make a very firm structure.  As such, we humans found the texture and structure of this gelatinous seaweed appealing and most asian cultures have adapted it to suit their fancy.  (Americans, on the other hand, are a bit more slow on the uptake.  Weird textures freak us out it seems!).  Agar-agar is also used in jellies, jams, soups and other various food-stuffs that need to be thickened or solidified, as it produces a smooth texture and has a melting point that is easy to reach in the kitchen without burning. (85C is the common temp we lab rats give).

Sciency-food-fact! Often, myself and my peers refer to agar plates as “similar to Jell-O”. (In fact, in lieu of a proper plate, I demonstrated an experiment once using Jell-O as a growth substrate!).  Unfortunately, this is a bit of a misnomer…Jell-O also contains a giggly food thickener, like agar-agar, called gelatin. However, it is a collagen polymer derived from animal tissue, not a sugar polymer from plants.  The collagen is a much more loose mesh, molecularly, and does not give as firm of a structure as the plant cell polymer does.  (Play with your upper ear for a good example of collagen).  A plant polymer, like agar-agar, affords more stability and more rigidity to the cells. (Try bending a leaf, it doesn’t work quite so well as your ear…) Therefore, if you were to compare a treat solidified by agar-agar to one solidified by gelatin, the agar-agar product would be more solid and have a thicker, smoother texture than that of the gelatin product.  And now you know!

Anyway, back to science.

A lab tech in Robert Koch’s lab, clearly enjoying her jelly tea, realizes that this agar-agar stuff would be a great solidification substance to grow bacteria on.  Thus, agar plates were born.

MacConkey agar. The growth in pink indicates lactose utilization, while the yellow does not.

We use agar-agar to solidify damn near all sorts of media into small, compact little circles that allow us to more easily quantify and isolate the microscopic lifeforms we work with.  From LB and minimal medias to MacConkey and blood agar, we use this white powder for damn near everything.  Its relatively simple, toss an amount into the liquid media (i.e. 15g for 1L of LB in most labs), autoclave it up, let it cool and pour. Simple as that.

Agar has numerous practical uses.  We can identify enviromental isolates (or at least start to) using several selective medias in agar.  For example, MacConkey agar grows only Gram negative bacteria and will change color depending on the isolate’s ability to ferment lactose.  Blood agar plates demonstrate whether a species can lyse bloodcells (either beta or alpha) and often help to differentiate between Strep and Staph isolates.  Hektoen enteric agar is used to identify organisms from, as the name states, the Enterobacteriaceae family.  I’ve used HEA before to identify a Shigella species in particular, but it is often used for any fecal MO’s (like Salmonella).

A fine example of a quadrant streak that shows the isolation of several distinct colonies, as indicated by color.

We also modify agar in order to isolate a pure culture: a colony in which the cells came from ONE lone parent organism via the quadrant or enviromental streak.  We can also identify microorganisms by their resistance to an antibiotic impregnated into the media.  For example, alot of plasmids that we use commercially have an antibiotic resistance cassette placed within the DNA.  This provides us researchers an easy form of identification of clones who had the correct plasmid shoved into their membranes as they will grow on, say, LB with Amp.

Of course, this technique and the other plates I’ve mentioned will have to wait for another day.  This post is getting long and my intentions were only to give a brief explanation of agar and why we use it!  Clearly I got carried away!  So stay tuned for my next post and perhaps the next in my series of HTWADYB!




Hello world!

This little addition to my home doesn't help either...

Apollo, my new Shiba Inu pup.

As it turns out, applying to graduate school and attempting to survive your last year of college takes alot more out of a student than I expected.  Who knew?  Well, I made it!  Graduate school at UMBC is on the horizon and I will be packing up to move to Baltimore within the next few weeks.  In the interim between now and when my course work starts, it is my utmost goal to get a few blog posts out per week on an assortment of information biological or scientific that I find interesting.

So, what shall we do for today?  Well, for starters, lets talk about graduate school admissions.  The decision to go to graduate school is not one that should be taken lightly in today’s economy.  Below are the tips I received or learned on my own about the graduate admissions fiasco process.  Take my advice as you see fit.  Note: I am NOT part of any graduate admissions board–this is just the process I went through and my thoughts on the matter.  Anything I say does not reflect my school or any other school’s opinion on the matter.

The Good:

Formalities aside, applying to graduate school is a very big step forward in your career as a scientist.  For most college juniors and seniors, there are three major choices that they can make towards their future.  They can go to medical school, to graduate school or they can attempt to work for a few years to fill in their resume.  Having a higher education in this field is incredibly important in moving up on (not only the pay-scale) but in the research community.

This being said, make friends with the graduate admissions secretary at each school you are applying to.  Typically, I received an email within a week of submitting my online application from the secretary stating that everything (or not) was in her office and she was avaliable for questions.  I followed up almost instantaneously, making sure that transcripts, letters of reference and my own cover statement made it to the school in a timely fashion.  They were usually super helpful, provided you were chipper and polite, and were prompt in letting me know if something was askew.

The Bad:

I felt like this 90% of the time...

Does this need a caption?

As thankful as you may be for your professor/boss/co-worker to write your LoR for you, recommendations do get lost in the mail/translation/minds of the recommender, so you must keep on your three people to ensure that everything was put in on their end.  Each school wants something different from your recommender and it is up to you, not them, to keep it straight.  Give them a list that includes: each school’s name, address, form or format wanted as well as the dates in which your application is due.  Hand it to them with lots of praise (and treats, like cookies, always help!) and then ride their ass until you get confirmation from them and the admissions office that the recommendation has been accepted.

(As it turns out, I had to chase down one of my people for over a week to get him to submit the recommendation. As it turns out, he forgot. -_-;)

The other 10% I felt like this.

Again, is a caption really needed here?!?

Another glorious /sarcasm aspect to the admissions process, while we’re on the topic, is the vast differences each school wants out of you, the applicant.  Some schools want everything online, some want it in paper, some want half and half.  Its truly a PITA process and again, it is up to you to keep it straight.  I kept a running list of my usernames, passwords and current application status going on my desktop, as well as on my bathroom mirror.  And I still struggled to keep it straight.

The absolute worst part about the graduate admissions process, unfortunately, is the waiting game.  I submitted all of my applications by December 15th and waited for close to three months before I got my first letter.  Oh! And speaking of letters…Rejection letters are the worst, most horrible feeling an applicant can ever get.  Quite honestly, its like taking a bit of your soul, crumpling it into little bits and then feeding it to rabid hyenas (which is exactly what you did during the application process) and then finding out that you gave the hyenas E. coli and they don’t want to see you again.

All I can tell you is chin up.  It may be the absolute worst feeling in the world, but it does, indeed get better…

The Epic:

The feeling you get when you finally get a “We LOVE you, come to our school.”  There’s no other thing I need to say but that.

Seriously.  That’s it.  I expect all of my readers to be intelligent enough to know how to handle an interview/wine-and-dine date with your school.  If you don’t GTFO ask me!

That, ladies and gentlemen, was my experience with graduate school admissions as a helpless undergrad.  I sincerely hope that it will help you find a bit of clarity, or at least a smile, as you read it.  Especially to those of you out there who will be applying this upcoming fall.  Start early, stay positive and good luck!

I should have another update to you all within the week.  This time, hopefully about something much more sciencey and gooey. Well, maybe not gooey…


The Alchemist Kitten

Past Experiments