Transcription
Captions are enabled! Click CC on the bottom right to turn them off. When I was younger, my parents would let me take my favorite dinosaurs into the bath. Probably to convince me to get into the bath. I remember my dinosaurs really well! To be honest, I knew pretty much all of my dinosaurs. I had epic dinosaur fights. Sometimes my little sister would play with them too, but just... a little differently. Anyway, I remember one day my favorite stegosaurus lost its head. It just broke off! I was determined to get my parents to fix him, but we discovered that there were things growing in the toy... Now I realize that the things that were big enough to see were probably mold, but my mom told me that Sergeant Stegosaurus would have to retire from the bathtub, and that I would have to buy a new one, because the bacteria had taken over. This led me to develop 2 misconceptions about bacteria: (1) that bacteria were only found on or in things that had become contaminated in some way, and (2) that bacteria were always bad and therefore Sergeant Stegosaurus had to be replaced... But that's not true on either account. For starters, besides mold, there were probably bacteria in the dinosaur too. But that's not so crazy, because bacteria are everywhere. Bacteria can be found in our homes - yes, even very clean homes - and they can be found outside. Bacteria colonize our skin and our digestive system. That solves the first misconception that you only find bacteria on contaminated or "dirty" surfaces. And as for the second misconception, well, bacteria get a bad rap. Now, I do agree that the dinosaur had to be thrown away. That was a good decision. There was probably mold in that dinosaur, but there were probably also plenty of bacteria growing. A growing population of mold and bacteria... not ideal for bath toys. But we do want to mention that bacteria are often all considered to be bad, which shouldn't happen, because not all bacteria are bad! In fact, many types of bacteria are beneficial to organisms and ecosystems. We'll give you a few examples. Some bacteria that colonize your skin are good for you - they even prevent harmful bacteria and other pathogens from growing there. Bacteria in your digestive system even help you digest your food, and some produce certain vitamins. Some types of bacteria are used in the production of some of the foods that we eat. In ecosystems, bacteria play a very important role as decomposers of organic matter. Bacteria also play an important role in the nitrogen cycle: they fix the nitrogen that plants need. These are just a few examples of beneficial bacteria. That's not to say that bacteria can never be pathogens. Bacteria cause strep throat, tetanus, tooth decay, some types of pneumonia, diphtheria, salmonella, cholera... I could go on! Antibiotics are used to fight some bacteria. And while antibiotics are very important for fighting bacterial infections, we also need to mention that some broad-spectrum antibiotics can also affect the good bacteria. We also need to mention that antibiotics do not work on viruses. Viruses are pathogens that are not made of cells; you can check out our other video on viruses! Furthermore, there are vaccines that can prevent all sorts of bacterial and viral infections. Okay, so what exactly are bacteria? Bacteria are one of the three 'domains' of life. As you can see here, they come in different shapes. Some of them are heterotrophs - which means they feed on organic material. But some are autotrophs - they can make their own food. Plants are not the only ones that can be autotrophic. Let's take a look at a bacterium. A bacterium is a prokaryotic cell, which is usually much smaller than a eukaryotic cell like our cells. If you remember from our video on prokaryotic versus eukaryotic cells, that means that bacteria do not have a nucleus or other membrane-bound organelles. But they do have ribosomes, cytoplasm, and a cell membrane, and almost all bacteria have a cell wall. Like all living organisms, bacteria have DNA. Bacterial DNA also consists of two strands, but is arranged in a circular shape. Depending on the species, some bacteria also have a flagellum to help with movement, some have a capsule for extra protection or adhesion, or 'pili' which help them adhere better to surfaces or to each other. Oh, and many bacterial species have a plasmid, which is basically a type of... extra DNA. More on that later. Bacteria have a number of intriguing skills that are different from those of our human cells. Our own body cells divide themselves through mitosis and cytokinesis, but bacteria multiply much faster: that's called binary fission. This is a type of asexual reproduction where bacteria divide and make a copy of themselves. Because it's asexual reproduction, you would expect the daughter cells to be identical to the parent cells, unless a mutation has occurred. Some species of bacteria have the ability to share genetic material with each other. Remember how we said that bacteria can have a plasmid - an extra copy of DNA with usually only a few genes on it? Bacteria can share these plasmids with each other in a process known as conjugation. The pili are used to share this genetic information with each other. If the plasmid happens to have a gene that gives some resistance to an antibiotic, then the bacterium that receives this plasmid may survive exposure to this antibiotic. Which can be quite a big problem. Watch our video on natural selection to learn more about how antibiotic resistance can develop over time. Bacteria can also pick up plasmids from their environment. This often happens during periods that are stressful for the bacteria. In a process known as bacterial transformation, scientists use a type of stimulus, like a heat shock - to stimulate bacteria in a lab to take up genetic material. There are all sorts of ways we can use these genetically engineered bacteria. Some species of bacteria can form endospores. With endospores, bacteria can survive in all sorts of hostile environments: when there are few nutrients, at freezing temperatures, drought... just to name a few examples. This is one reason why hospitals need to be very good at sterilization processes. We're not talking about the process of endosporulation - how bacteria reactivate after forming endospores - but this is certainly something very interesting to explore. Finally, some species of bacteria (along with other types of prokaryotes called Archaea), are extremophiles. Unlike our own cells, extremophiles can live in extreme environments with, for example, excessive heat, chemicals that our cells would find toxic, or with radioactive radiation. We share this planet with so many species of bacteria that scientists are still learning more about every day. And if this topic interests you, you might want to delve further into microbiology. So many careers - from agriculture to medical work to environmental - rely heavily on the study of microbiology. That was the Amoeba Sisters, and we remind you to stay curious!