Bacteria: A Detailed Look

When I was a little kid, my parents would let me take my favorite set of dinosaurs into the tub...probably to persuade me into taking a bath. I remember my dinosaurs well! In fact, I used to know all of my dinosaurs. I had epic dinosaur battles. Sometimes my sister would play with them, too...j...

When I was a little kid, my parents would let me take my favorite set of dinosaurs into the tub...probably to persuade me into taking a bath. I remember my dinosaurs well! In fact, I used to know all of my dinosaurs. I had epic dinosaur battles. Sometimes my sister would play with them, too...just...a little differently. Anyway, I remember that one day, unfortunately, my favorite stegosaurus lost his head. I mean, literally, it just popped off. And while I was determined to get my parents to fix it, we discovered that there was stuff growing in the toy. Now, I realize what was actually large enough to be visible was likely mold, but at the time, my mother told me that Sergeant Stegosaurus would have to retire from the bathtub, and I'd have to get a new one because bacteria had taken over. It led to two misconceptions I developed about bacteria: (1) that bacteria were only found Misconceptions about bacteria on or in things that had gotten contaminated somehow and (2) that bacteria are always bad and that is why Sergeant Stegosaurus required replacing. Those are both not correct. First of all, there probably were bacteria in the dinosaur along with the mold. But that shouldn't be surprising, because bacteria are everywhere. Bacteria are found in our houses- yes, even very clean houses- and they are found outside. Bacteria colonize our skin and our digestive system. That addresses the first misconception that you only find bacteria on contaminated or "dirty" surfaces. And as for the second misconception, well, bacteria sure do get a bad reputation. Now I'm not disagreeing that the toy should have been thrown out. That was a good decision. There was probably mold that was in that toy dinosaur- a fungus - but there was likely plenty of bacteria growing there with it. A growing community of mold and bacteria...not ideal for a bath toy. But we do want to mention that many times, all bacteria are lumped together as a bad Many bacteria are helpful thing- which shouldn't happen, because not all bacteria are bad. In fact, many types of bacteria are helpful for organisms and ecosystems. We'll give you some examples. Some of the bacteria that colonize your skin are beneficial and actually help keep harmful strains and other types of pathogens from growing. Bacteria in your digestive system actually help break down food and some can produce certain vitamins. Some types of bacteria are used in producing some foods that we eat. In ecosystems, bacteria have a very important role as decomposers. Bacteria also have major roles in the nitrogen cycle to fix nitrogen that plants need. These are just a few examples of helpful, beneficial bacteria. Now that's not to say bacteria can't be pathogens. Harmful bacteria Bacteria are the cause of strep throat, tetanus, tooth decay, some forms of pneumonia, diphtheria, salmonella, cholera...I could go on. Antibiotics Antibiotics can be used to combat some of these. And while antibiotics are very important for destroying bacterial infections, we shouldn't leave out saying that some broad spectrum antibiotics can harm some of the "good" bacteria as well. Also, we should mention that antibiotics do not work on viruses. Viruses are pathogens that are not made of cells at all; you can check out our video on them. Additionally, there are vaccines which can prevent many types of both bacterial and viral infections. Ok, so what are bacteria exactly? In the three domains of life, bacteria encompass one of them. Characteristics of bacteria They come in different types of shapes as you can see here. Some of them are heterotrophs\-\--meaning they consume or feed on some organic matter. But some are autotrophs---they can make their own food. Plants aren't the only one that can be autotrophs. Let's take a look at a bacterium here\-\--bacterium is just singular word while bacteria is plural. A bacterium is a prokaryotic cell, which are generally much smaller than eukaryotic cells like ours. If you recall from our prokaryotic vs. eukaryotic cells video, that means bacteria do not have a nucleus or other membrane-bound organelles. But you will find ribosomes, cytoplasm, a cell membrane, and nearly all bacteria have a cell wall. Like all living organisms, bacteria have DNA. Bacterial DNA, while still double stranded, is arranged in a circular shape. Depending on the species, bacteria can also have a flagellum to help with movement, a capsule which can help give them extra protection or attachment abilities, or pili which can help with attaching to surfaces...including each other. Oh, and many bacterial species have a plasmid. Which is basically like...extra DNA. More about that later. Bacteria have some intriguing abilities that are different from our human cells that we'd like to mention. Bacterial reproduction Unlike our own body cells which perform mitosis and cytokinesis to divide, bacteria generally multiply even faster in a process called binary fission. This is a type of asexual reproduction when the bacteria can easily divide to make a copy of themselves. Since it is asexual reproduction, the daughter cells would be expected to be identical to the parent cells unless there is a mutation. Conjugation and Antibiotic Resistance Some types of bacteria do have the ability to share genetic material with each other. Remember how we mentioned that bacteria can have a plasmid\-\--an extra copy of DNA with usually just a few genes on it? Bacteria can share these plasmids with each other in a process known as conjugation. The pili can be used to share this genetic information with each other. If the plasmid happens to have a gene that gives some degree of resistance to an antibiotic, this may allow the bacterium that received the plasmid to survive exposure to that antibiotic. Which could be very problematic. You can learn more about how antibiotic resistance can develop over time in bacteria in our natural selection video. Bacteria can also pick up plasmids from their environment. Bacterial Transformation Often when this happens it is during a time of stress for the bacteria. In a process known as bacterial transformation, scientists can use a type of stimulus---such as a heat shock\-\--to induce bacteria in a lab setting to pick up genetic material. There are all kinds of these uses for these genetically engineered bacteria that you can explore. Some types of bacteria can form endospores. Endospores Endospores allow bacteria to be survivors in all kinds of hostile environments: lack of nutrients, freezing temperatures, drought\...just some examples. This is a reason why hospitals have to be very good at sterilization processes. We won't go through the process of endosporulation\-\--or how bacteria reactivate after forming endospores\-\--but this is definitely something interesting to explore Finally, some types of bacteria (along with other types of prokaryotes called Archaea), Extremophiles can be extremophiles. Unlike our own cells, extremophiles can live in extreme environments where there may be excessive heat, chemicals that our cells would find toxic, or even radiation. Overall, we share this planet with so many kinds of bacteria that scientists continue to learn more about them every day. And if this kind of topic interests you, you may want to look into the study of microbiology. So many careers- from agriculture to the medical field to environmental work- rest heavily on the study of microbiology. Well, that's it for the Amoeba Sisters, and we remind you to stay curious.