The standard way to streak a plate involves creating a resevoir of the sample you are studying, then using a sterile tool to streak through that at a steep angle. Then you streak through the first streak with another sterile tool, and so on and so forth.
As you streak through lines, the amount of bacteria pulled along is reduced until you are able to isolate individual colonies.
Pretty much. It’s like a little wire loop - sterilize it with a bunsen burner, let it cool, then take a swab from your source specimen and drag it into your agar for that section 1. Sterilize it again with the burner, cool, then drag through the last couple lines of 1 to get region 2. Repeat for 3 and again for 4. The sample size of individual microbes gets exponentially fewer each time - done correctly and region 4 is dotted with individual cells, which you leave alone for a while to incubate, then come back and start making your observations like how it’s interacting with the agar, what color, texture etc; smear it onto a microscope slide, see how it responds to different stains, it’s shape, it’s arrangement… then start checking all those findings against known properties of different microbes until you find a match.
I made that mistake several times, but iirc it was always a recoverable error. When I stuck that hot loop into the agar it would sizzle, which would tell me I just murdered every bacterium that loop touched; so resterilize actually allow it to cool this time, and repeat the botched step in a slightly different location to pass through a section of bacteria that I hadn’t just dropped a nuke on.
…which is probably shitty technique, but it got me good enough results to get good enough data for class.
The standard way to streak a plate involves creating a resevoir of the sample you are studying, then using a sterile tool to streak through that at a steep angle. Then you streak through the first streak with another sterile tool, and so on and so forth.
As you streak through lines, the amount of bacteria pulled along is reduced until you are able to isolate individual colonies.
Til! Thanks!
Visual breakdown for anyone interested:
Nice username
1 through to the end are all made with new, sterile… sticks?
Look ma, I’m a biochemist now!
Pretty much. It’s like a little wire loop - sterilize it with a bunsen burner, let it cool, then take a swab from your source specimen and drag it into your agar for that section 1. Sterilize it again with the burner, cool, then drag through the last couple lines of 1 to get region 2. Repeat for 3 and again for 4. The sample size of individual microbes gets exponentially fewer each time - done correctly and region 4 is dotted with individual cells, which you leave alone for a while to incubate, then come back and start making your observations like how it’s interacting with the agar, what color, texture etc; smear it onto a microscope slide, see how it responds to different stains, it’s shape, it’s arrangement… then start checking all those findings against known properties of different microbes until you find a match.
raise your hand if you ever wrecked a plate by forgetting to cool the loop
✋
I made that mistake several times, but iirc it was always a recoverable error. When I stuck that hot loop into the agar it would sizzle, which would tell me I just murdered every bacterium that loop touched; so resterilize actually allow it to cool this time, and repeat the botched step in a slightly different location to pass through a section of bacteria that I hadn’t just dropped a nuke on.
…which is probably shitty technique, but it got me good enough results to get good enough data for class.
This would have been a handy technique if in addition to forgetting to cool the loop I also noticed that I had forgot to cool the loop lol
Another way is one use throwable plastic hoop. Which is completely stupid, but well…