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Bacterial DNA & Genetics: Crash Course Biology #38
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Duration: | 10:25 |
Uploaded: | 2024-04-09 |
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MLA Full: | "Bacterial DNA & Genetics: Crash Course Biology #38." YouTube, uploaded by CrashCourse, 9 April 2024, www.youtube.com/watch?v=Y1LKHx_GrsY. |
MLA Inline: | (CrashCourse, 2024) |
APA Full: | CrashCourse. (2024, April 9). Bacterial DNA & Genetics: Crash Course Biology #38 [Video]. YouTube. https://youtube.com/watch?v=Y1LKHx_GrsY |
APA Inline: | (CrashCourse, 2024) |
Chicago Full: |
CrashCourse, "Bacterial DNA & Genetics: Crash Course Biology #38.", April 9, 2024, YouTube, 10:25, https://youtube.com/watch?v=Y1LKHx_GrsY. |
Bacteria often get a bad rap, but they’re some of our best partners in science and medicine! In this episode, we’ll explore what bacteria are doing with their DNA — including how they can trade it around. We’ll learn about chromosomes and plasmids, gene expression and recombinant DNA, and how E. coli are used to make insulin.
Introduction: The Microbiome 00:00
Prokaryotes & DNA 1:33
Plasmids & Horizontal Gene Transfer 2:44
Insulin 4:49
Gene Expression 6:30
Dr. Rebecca Lancefield 7:54
Review & Credits 9:05
This series was produced in collaboration with HHMI BioInteractive, committed to empowering educators and inspiring students with engaging, accessible, and quality classroom resources. Visit https://BioInteractive.org/CrashCourse for more information.
Are you an educator looking for what NGSS Standards are covered in this episode? Check out our Educator Standards Database for Biology here: https://www.thecrashcourse.com/biologystandards
Check out our Biology playlist here: https://www.youtube.com/playlist?list=PL8dPuuaLjXtPW_ofbxdHNciuLoTRLPMgB
Watch this series in Spanish on our Crash Course en Español channel here: https://www.youtube.com/playlist?list=PLkcbA0DkuFjWQZzjwF6w_gUrE_5_d3vd3
Sources: https://docs.google.com/document/d/1GLDtAXE6ekg4Chk2qN3TYbNt0pJbyaHqTqRd6QY8pd4/edit?usp=sharing
***
Crash Course is on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse
Thanks to the following patrons for their generous monthly contributions that help keep Crash Course free for everyone forever:
Leah H., David Fanska, Andrew Woods, DL Singfield, Ken Davidian, Stephen Akuffo, Toni Miles, Steve Segreto, Kyle & Katherine Callahan, Laurel Stevens, Burt Humburg, Perry Joyce, Scott Harrison, Mark & Susan Billian, Alan Bridgeman, Breanna Bosso, Matt Curls, Jennifer Killen, Jon Allen, Sarah & Nathan Catchings, team dorsey, Bernardo Garza, Trevin Beattie, Eric Koslow, Indija-ka Siriwardena, Jason Rostoker, Siobhán, Ken Penttinen, Nathan Taylor, Barrett & Laura Nuzum, Les Aker, William McGraw, Vaso, ClareG, Rizwan Kassim, Constance Urist, Alex Hackman, Pineapples of Solidarity, Katie Dean, Stephen McCandless, Wai Jack Sin, Ian Dundore, Caleb Weeks
__
Want to find Crash Course elsewhere on the internet?
Instagram - https://www.instagram.com/thecrashcourse/
Facebook - http://www.facebook.com/YouTubeCrashCourse
Twitter - http://www.twitter.com/TheCrashCourse
CC Kids: http://www.youtube.com/crashcoursekids
Introduction: The Microbiome 00:00
Prokaryotes & DNA 1:33
Plasmids & Horizontal Gene Transfer 2:44
Insulin 4:49
Gene Expression 6:30
Dr. Rebecca Lancefield 7:54
Review & Credits 9:05
This series was produced in collaboration with HHMI BioInteractive, committed to empowering educators and inspiring students with engaging, accessible, and quality classroom resources. Visit https://BioInteractive.org/CrashCourse for more information.
Are you an educator looking for what NGSS Standards are covered in this episode? Check out our Educator Standards Database for Biology here: https://www.thecrashcourse.com/biologystandards
Check out our Biology playlist here: https://www.youtube.com/playlist?list=PL8dPuuaLjXtPW_ofbxdHNciuLoTRLPMgB
Watch this series in Spanish on our Crash Course en Español channel here: https://www.youtube.com/playlist?list=PLkcbA0DkuFjWQZzjwF6w_gUrE_5_d3vd3
Sources: https://docs.google.com/document/d/1GLDtAXE6ekg4Chk2qN3TYbNt0pJbyaHqTqRd6QY8pd4/edit?usp=sharing
***
Crash Course is on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse
Thanks to the following patrons for their generous monthly contributions that help keep Crash Course free for everyone forever:
Leah H., David Fanska, Andrew Woods, DL Singfield, Ken Davidian, Stephen Akuffo, Toni Miles, Steve Segreto, Kyle & Katherine Callahan, Laurel Stevens, Burt Humburg, Perry Joyce, Scott Harrison, Mark & Susan Billian, Alan Bridgeman, Breanna Bosso, Matt Curls, Jennifer Killen, Jon Allen, Sarah & Nathan Catchings, team dorsey, Bernardo Garza, Trevin Beattie, Eric Koslow, Indija-ka Siriwardena, Jason Rostoker, Siobhán, Ken Penttinen, Nathan Taylor, Barrett & Laura Nuzum, Les Aker, William McGraw, Vaso, ClareG, Rizwan Kassim, Constance Urist, Alex Hackman, Pineapples of Solidarity, Katie Dean, Stephen McCandless, Wai Jack Sin, Ian Dundore, Caleb Weeks
__
Want to find Crash Course elsewhere on the internet?
Instagram - https://www.instagram.com/thecrashcourse/
Facebook - http://www.facebook.com/YouTubeCrashCourse
Twitter - http://www.twitter.com/TheCrashCourse
CC Kids: http://www.youtube.com/crashcoursekids
Hi!
I’m Dr. Sammy, your friendly neighborhood entomologist, and this is…me!
I’m a human, made up of around 37 trillion cells like these. They form my skin, my spleen, and all of what makes me, me. But that’s not all. My body also plays host to several trillion of these: bacteria. On average, humans have roughly as many bacteria as they have cells, often more!
You truly do contain multitudes! So many bacteria that it can be described as a biome, the microbiome. There are bacteria in my gut helping me digest food, in my mouth working to prevent tooth decay, and on my skin helping me maintain this healthy glow. And while there are definitely harmful bacteria out there that you don’t want, most of the ones hanging out inside us are doing some good, or at least, they’re not hurting anything.
Bacteria are actually their own form of life. Like us, they have DNA, though they organize and regulate it differently. And in fact, bacteria are some of our best partners in science and medicine.
The study of bacterial DNA and genetics has led to some major breakthroughs in how we treat a whole host of diseases. So now that you’ve gotten to know me and my bacteria, welcome to Crash Course Biology! Now, let’s hear that sweet, sweet theme music from—wait, no? We’ve got the budget for the bacteria-street boys?! [THEME MUSIC] Along with their distant cousins, archaea, bacteria are part of a group called prokaryotes. Their motto? “No nucleus, no problem.” They’d probably get it on a T-shirt, if we could make them x-tra, x-tra, x-tra small..and if they had arms. Prokaryotes don’t have a defined cellular nucleus to neatly store their DNA, the way that eukaryotes like plants, animals, and fungi do. So they have to handle their genetic information a little differently.
If we took a look inside an animal cell, we’d see that the DNA in the nucleus is wound up tight into chromosomes. Animals can have a pretty wide range of chromosome pairs per cell. Like, fruit flies have four pairs, while the Atlas blue butterfly has 225. On the other hand, if we peeked inside a bacterial cell, things would look a lot different. Most bacteria only ever have one chromosome, and it’s sort of circular.
Which would be more obvious if it weren’t so twisted up with coils and supercoils, stabilized by proteins. The chromosomes reside in an area of the cell called the nucleoid. While it’s similar to a nucleus — the name even means ‘nucleus-like’— it lacks the structured packaging of a nucleus. It’s less like an enclosed clubhouse and more like an open field where genetic materials run wild. In addition to that one chromosome, bacteria can have a collection of smaller circles of DNA called plasmids.
Plasmids duplicate separately from the main chromosome, and their DNA isn’t always 100 percent necessary for the bacteria’s everyday survival. They can come in handy though. For example, the genes carried in bacterial plasmids can help make the bacteria resistant to antibiotics. That may sound like a bad thing to us humans, but it’s all about perspective.
Bacteria gotta live, too. One of the really wild things about plasmids is that they’re transferable. Just because a bacterium starts with a certain set of plasmids doesn’t mean it’s stuck with them. Unlike plants and animals, which only get genes that they inherit from their parents, bacteria can transfer plasmids, exchange them, and even collect new ones from the environment in what’s called horizontal gene transfer. It’s actually a pretty popular mechanism to give people superpowers in comics that might sound familiar. Like, radioactive animal “x” bites nerdy person “y” and transfers its abilities. That’s right, Spider-Man is a product of horizontal gene transfer.
Sometimes, getting a new plasmid doesn’t do much for a bacterium, but in other cases, it can be like being bitten by a radioactive spider and getting the power to climb walls, and sense danger, and crack wise while hanging upside down from a silken thread. The bacterium ends up stronger, with new abilities or resistances that it didn’t have before, like the ability to survive in high levels of a heavy metal, like mercury. Horizontal gene transfer also adds genetic diversity to the bacterial gene pool in a similar way that sexual reproduction in eukaryotes does. Which is important because, while eukaryotes often reproduce using the DNA of two individuals, bacteria basically just clone themselves. So, without horizontal gene transfer, you’d have a lot of pretty similar organisms. That would make them super susceptible to being all wiped out by the same thing in one fell swoop.
But because horizontal gene transfer increases the genetic diversity of the population, it becomes more resilient overall, as individuals have different vulnerabilities and strengths. Dang, science, that’s deep. In any case, our growing understanding of plasmids is leading to major leaps in the world of medicine. Take insulin for example, one of the most important molecules in the human body. It’s responsible for regulating how sugar gets used, and without enough of it, there’s often too much sugar in your bloodstream and not enough in your cells.
So, for decades, doctors and researchers have been working on ways to make insulin for people with diabetes that can’t produce enough of it on their own. For a long time, this was done by purifying insulin from cows and pigs for human use. And although animal insulin is still used today, it can cause allergic reactions in some people. Enter plasmid research. By the early 1980s, a new type of insulin had hit the market, made from an unexpected place: a plasmid in E. coli bacteria.
In this method, scientists take the gene that we humans use to make insulin, and they insert it into an E. coli plasmid. This hybrid is called a recombinant DNA molecule: It’s a combo of both human and bacterial DNA. The plasmid is then put back into the E. coli, and the bacterium carries on as normal! As it reproduces, it makes more and more copies of that plasmid — along with more and more copies of the insulin gene in a process called gene cloning. As time goes on, these bacteria read that gene and start turning it into proteins — specifically, into human insulin.
The molecule can then be harvested and purified so it’s ready to be used in people. This new strategy for producing insulin has helped save millions of lives, all with the help of our bacterial buds. Besides insulin, gene cloning has also been used to make cancer drugs and human growth hormones, which are used to treat diseases such as HIV.
And studying bacterial DNA has led to other medical advances as well. For example, some researchers focus on how bacterial genes are expressed. Gene expression describes the way that cells can turn their genes off and on, depending on their needs, producing different proteins as a result. This helps prokaryotes and eukaryotes alike adjust to the conditions around them.
Like, if the water that bacteria live in suddenly gets too hot or salty, they can make different proteins that help them adapt. As it turns out, gene expression in bacterial cells doesn’t look that different than in our own. A protein called an activator can bind to DNA to get transcription to start, like a little green “go” flag. When that happens, a section of DNA is copied into an mRNA molecule, which is then carried off and used as the instructions to build a protein.
On the flip side, proteins called repressors can stop transcription from happening, raising a “stop” sign to halt protein-making in its tracks. And understanding how gene expression works in potentially harmful microbes turns out to be… pretty useful for researchers, such as Dr. Rebecca Lancefield. Let’s take our seats and listen to her story over in the Theater of Life… Meet Streptococcus.
A diverse type of bacterium. Some are harmless to humans, and others can give us some pretty nasty diseases like rheumatic fever or strep throat. But for a long time, we could only guess why some were so much more harmful than others. Enter American microbiologist Dr.
Rebecca Lancefield. She took up the mantle of strep research in the pre-antibiotic era, when there were few vaccines available to prevent diseases. And soldiers in World War I were frequently getting sick from strep-induced infections. Using samples collected from those soldiers, Lancefield and her team began classifying bacteria based on specific molecules displayed on their surface, like little bacterial name tags. These are called antigens — and which nametag a particular bacterium wears is controlled by its gene expression.
Learning to read those name tags turned out to be an indicator of which bacteria were dangerous, which weren’t, and to whom. Like, for Streptococcus, Lancefield realized there were two different kinds of antigens that could be expressed: one made of carbohydrate molecules, and another made of proteins. She discovered that the carbohydrates determine which species a strain of bacteria can infect, while the proteins determine how dangerous the strain is for that particular species.
Over six decades Lancefield’s antigen research helped inform everything from how to prescribe antibiotics, to how soldiers were housed in military barracks during World War II. Lancefield’s work showed us that sometimes studying the smallest thing can have the biggest impact! While we ourselves may be full of bacteria, we have to remember that as much as they’re a part of us – they’re also very much their own thing. And while there are definitely some that we want to avoid, bacteria as a group aren’t as malicious as they’re sometimes perceived. In fact, Earth is a microbial planet: life started with them and life as we know it could not survive without them.
And while we’ve only looked at a couple of branches on the bacterial family tree today, there are millions of others out there, and probably millions more waiting to be researched. In our next episode, we’re moving on from bacteria and into the rebellious world of viruses. They play by their own rules. I’ll see ya then!
PEACE! This series was produced in collaboration with HHMI BioInteractive. If you’re an educator, visit BioInteractive.org/CrashCourse for classroom resources and professional development related to the topics covered in this course. Thanks for watching this episode of Crash Course Biology, which was filmed at our studio in Indianapolis, Indiana, and was made with the help of all these nice people. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.
I’m Dr. Sammy, your friendly neighborhood entomologist, and this is…me!
I’m a human, made up of around 37 trillion cells like these. They form my skin, my spleen, and all of what makes me, me. But that’s not all. My body also plays host to several trillion of these: bacteria. On average, humans have roughly as many bacteria as they have cells, often more!
You truly do contain multitudes! So many bacteria that it can be described as a biome, the microbiome. There are bacteria in my gut helping me digest food, in my mouth working to prevent tooth decay, and on my skin helping me maintain this healthy glow. And while there are definitely harmful bacteria out there that you don’t want, most of the ones hanging out inside us are doing some good, or at least, they’re not hurting anything.
Bacteria are actually their own form of life. Like us, they have DNA, though they organize and regulate it differently. And in fact, bacteria are some of our best partners in science and medicine.
The study of bacterial DNA and genetics has led to some major breakthroughs in how we treat a whole host of diseases. So now that you’ve gotten to know me and my bacteria, welcome to Crash Course Biology! Now, let’s hear that sweet, sweet theme music from—wait, no? We’ve got the budget for the bacteria-street boys?! [THEME MUSIC] Along with their distant cousins, archaea, bacteria are part of a group called prokaryotes. Their motto? “No nucleus, no problem.” They’d probably get it on a T-shirt, if we could make them x-tra, x-tra, x-tra small..and if they had arms. Prokaryotes don’t have a defined cellular nucleus to neatly store their DNA, the way that eukaryotes like plants, animals, and fungi do. So they have to handle their genetic information a little differently.
If we took a look inside an animal cell, we’d see that the DNA in the nucleus is wound up tight into chromosomes. Animals can have a pretty wide range of chromosome pairs per cell. Like, fruit flies have four pairs, while the Atlas blue butterfly has 225. On the other hand, if we peeked inside a bacterial cell, things would look a lot different. Most bacteria only ever have one chromosome, and it’s sort of circular.
Which would be more obvious if it weren’t so twisted up with coils and supercoils, stabilized by proteins. The chromosomes reside in an area of the cell called the nucleoid. While it’s similar to a nucleus — the name even means ‘nucleus-like’— it lacks the structured packaging of a nucleus. It’s less like an enclosed clubhouse and more like an open field where genetic materials run wild. In addition to that one chromosome, bacteria can have a collection of smaller circles of DNA called plasmids.
Plasmids duplicate separately from the main chromosome, and their DNA isn’t always 100 percent necessary for the bacteria’s everyday survival. They can come in handy though. For example, the genes carried in bacterial plasmids can help make the bacteria resistant to antibiotics. That may sound like a bad thing to us humans, but it’s all about perspective.
Bacteria gotta live, too. One of the really wild things about plasmids is that they’re transferable. Just because a bacterium starts with a certain set of plasmids doesn’t mean it’s stuck with them. Unlike plants and animals, which only get genes that they inherit from their parents, bacteria can transfer plasmids, exchange them, and even collect new ones from the environment in what’s called horizontal gene transfer. It’s actually a pretty popular mechanism to give people superpowers in comics that might sound familiar. Like, radioactive animal “x” bites nerdy person “y” and transfers its abilities. That’s right, Spider-Man is a product of horizontal gene transfer.
Sometimes, getting a new plasmid doesn’t do much for a bacterium, but in other cases, it can be like being bitten by a radioactive spider and getting the power to climb walls, and sense danger, and crack wise while hanging upside down from a silken thread. The bacterium ends up stronger, with new abilities or resistances that it didn’t have before, like the ability to survive in high levels of a heavy metal, like mercury. Horizontal gene transfer also adds genetic diversity to the bacterial gene pool in a similar way that sexual reproduction in eukaryotes does. Which is important because, while eukaryotes often reproduce using the DNA of two individuals, bacteria basically just clone themselves. So, without horizontal gene transfer, you’d have a lot of pretty similar organisms. That would make them super susceptible to being all wiped out by the same thing in one fell swoop.
But because horizontal gene transfer increases the genetic diversity of the population, it becomes more resilient overall, as individuals have different vulnerabilities and strengths. Dang, science, that’s deep. In any case, our growing understanding of plasmids is leading to major leaps in the world of medicine. Take insulin for example, one of the most important molecules in the human body. It’s responsible for regulating how sugar gets used, and without enough of it, there’s often too much sugar in your bloodstream and not enough in your cells.
So, for decades, doctors and researchers have been working on ways to make insulin for people with diabetes that can’t produce enough of it on their own. For a long time, this was done by purifying insulin from cows and pigs for human use. And although animal insulin is still used today, it can cause allergic reactions in some people. Enter plasmid research. By the early 1980s, a new type of insulin had hit the market, made from an unexpected place: a plasmid in E. coli bacteria.
In this method, scientists take the gene that we humans use to make insulin, and they insert it into an E. coli plasmid. This hybrid is called a recombinant DNA molecule: It’s a combo of both human and bacterial DNA. The plasmid is then put back into the E. coli, and the bacterium carries on as normal! As it reproduces, it makes more and more copies of that plasmid — along with more and more copies of the insulin gene in a process called gene cloning. As time goes on, these bacteria read that gene and start turning it into proteins — specifically, into human insulin.
The molecule can then be harvested and purified so it’s ready to be used in people. This new strategy for producing insulin has helped save millions of lives, all with the help of our bacterial buds. Besides insulin, gene cloning has also been used to make cancer drugs and human growth hormones, which are used to treat diseases such as HIV.
And studying bacterial DNA has led to other medical advances as well. For example, some researchers focus on how bacterial genes are expressed. Gene expression describes the way that cells can turn their genes off and on, depending on their needs, producing different proteins as a result. This helps prokaryotes and eukaryotes alike adjust to the conditions around them.
Like, if the water that bacteria live in suddenly gets too hot or salty, they can make different proteins that help them adapt. As it turns out, gene expression in bacterial cells doesn’t look that different than in our own. A protein called an activator can bind to DNA to get transcription to start, like a little green “go” flag. When that happens, a section of DNA is copied into an mRNA molecule, which is then carried off and used as the instructions to build a protein.
On the flip side, proteins called repressors can stop transcription from happening, raising a “stop” sign to halt protein-making in its tracks. And understanding how gene expression works in potentially harmful microbes turns out to be… pretty useful for researchers, such as Dr. Rebecca Lancefield. Let’s take our seats and listen to her story over in the Theater of Life… Meet Streptococcus.
A diverse type of bacterium. Some are harmless to humans, and others can give us some pretty nasty diseases like rheumatic fever or strep throat. But for a long time, we could only guess why some were so much more harmful than others. Enter American microbiologist Dr.
Rebecca Lancefield. She took up the mantle of strep research in the pre-antibiotic era, when there were few vaccines available to prevent diseases. And soldiers in World War I were frequently getting sick from strep-induced infections. Using samples collected from those soldiers, Lancefield and her team began classifying bacteria based on specific molecules displayed on their surface, like little bacterial name tags. These are called antigens — and which nametag a particular bacterium wears is controlled by its gene expression.
Learning to read those name tags turned out to be an indicator of which bacteria were dangerous, which weren’t, and to whom. Like, for Streptococcus, Lancefield realized there were two different kinds of antigens that could be expressed: one made of carbohydrate molecules, and another made of proteins. She discovered that the carbohydrates determine which species a strain of bacteria can infect, while the proteins determine how dangerous the strain is for that particular species.
Over six decades Lancefield’s antigen research helped inform everything from how to prescribe antibiotics, to how soldiers were housed in military barracks during World War II. Lancefield’s work showed us that sometimes studying the smallest thing can have the biggest impact! While we ourselves may be full of bacteria, we have to remember that as much as they’re a part of us – they’re also very much their own thing. And while there are definitely some that we want to avoid, bacteria as a group aren’t as malicious as they’re sometimes perceived. In fact, Earth is a microbial planet: life started with them and life as we know it could not survive without them.
And while we’ve only looked at a couple of branches on the bacterial family tree today, there are millions of others out there, and probably millions more waiting to be researched. In our next episode, we’re moving on from bacteria and into the rebellious world of viruses. They play by their own rules. I’ll see ya then!
PEACE! This series was produced in collaboration with HHMI BioInteractive. If you’re an educator, visit BioInteractive.org/CrashCourse for classroom resources and professional development related to the topics covered in this course. Thanks for watching this episode of Crash Course Biology, which was filmed at our studio in Indianapolis, Indiana, and was made with the help of all these nice people. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon.