Today was pretty interesting, this mornings Microbiology lecture was on cell structure (I can see a theme for this week after Histology and Physiology yesterday also being on a similar topic. Going have to brush on my cell biology as if its getting this much attention then its gotta be pretty important! One of the things I consider most imporant within this is the difference between Gram positive and Gram negative bacteria. Most bacteria cells have a wall around them which controls the transfer of stuff in and out of the cell. This affects what types of antibiotics can be used in treatment, as to the diagnostic techniques used in the identification of it.
Anyways after this lecture it is time for a quick break and then onto the practical session, I was kinda excited to see how well I had done innoculating my plates in last weeks practical. Today we walked into a set up of loads of different coloured plates like this…
Sometimes I really do have to just stop and admire just how beautiful nature really is. Considering that all the bacteria on these plates can do harm to us its amazing how they manage to look so pretty.
Anyways enough of that, todays practical introduction was on the different mediums available to culture (grow) bacteria, how they are prepared and why they change the colours they do. Through my undergrad it had been a case of it just was, now I am learning the why and I am so much happier actually understanding this.
Culture media is important as when trying to determine a bacteria you basically test different properties to determine which it is. Within the selection we had today we had selective media (which restricts the type of bacteria that will grow on it), differentiative media (which tests a common property between negative and positive), and media specifically for the detection of pigment production by bacteria.
Basically agar is just a plain power that is mixed with water and then sets almost like Jelly. For selective media chemicals such as crystal violet and bile salts which restrict the growth of Gram positive bacteria (hence making it selective). For differentiative bacteria indicators are added to detect the presence of things such as pH or lactose which causes a change in color. And for special media chemicals are added to react with specific properties such as thiosulfate which is metabalised by Salmonella and forms colonies of bacteria with black centers.
Today we had prepared plates to examine the difference appearence of different bacteria on different culture media which was pretty cool. When you start to look at the differences you really do start to appreciate that a cell is alive, it eats, it puts out waste and its amazing how this happens with something so small.
We then looked at the different types of growths, shapes of colonies, and then using liquid medium as well for growth in a test tube. The growth and culture of anaerobic (without oxygen) bacteria using oxidation-reduction and an anoxic jar.