microbiology
Are viruses living?
Are viruses living? Well, let's take a look at the 8 characteristics of life:
1. All life reproduces
2. All life is made of one or more cells
3. All life must eat
4. All life responds to its environment
5. All life adapts/evolves to survive in its environment
6. All life grows
7. All life maintains internal and external homeostasis
8. All life must eventually die
They could be called 'quasi-living' because while they do display some characteristics of life, they do not display them all. Viruses can adapt/evolve to survive. They are, as we've read in "Survival of the Sickest" by Sharon Moalem, "masters of mutation". They do not, however, display the characteristic that all life is made of one or more cells. Even though viruses have DNA or RNA, they are not cells because they do not possess organelles.
"But Hannah!", you say. "Viruses can reproduce!"
That is entirely true.
However, while they do reproduce, they are unable to perform this function by themselves. They require a host cell and a host cell's organelles to help them produce more viruses. They sort-of-kind-of display this characteristic.
Also, as Miller found when he was experimenting with the juice from diseased tobacco leaves, viruses can be completely dehydrated, then re-hydrated, and still function properly. No life that is known to us can survive without water. Therefore, I must conclude that viruses are not living.
1. All life reproduces
2. All life is made of one or more cells
3. All life must eat
4. All life responds to its environment
5. All life adapts/evolves to survive in its environment
6. All life grows
7. All life maintains internal and external homeostasis
8. All life must eventually die
They could be called 'quasi-living' because while they do display some characteristics of life, they do not display them all. Viruses can adapt/evolve to survive. They are, as we've read in "Survival of the Sickest" by Sharon Moalem, "masters of mutation". They do not, however, display the characteristic that all life is made of one or more cells. Even though viruses have DNA or RNA, they are not cells because they do not possess organelles.
"But Hannah!", you say. "Viruses can reproduce!"
That is entirely true.
However, while they do reproduce, they are unable to perform this function by themselves. They require a host cell and a host cell's organelles to help them produce more viruses. They sort-of-kind-of display this characteristic.
Also, as Miller found when he was experimenting with the juice from diseased tobacco leaves, viruses can be completely dehydrated, then re-hydrated, and still function properly. No life that is known to us can survive without water. Therefore, I must conclude that viruses are not living.
Bacteria: form and arrangement
Sounds fun, right?
That's probably because it is. It is very fun.
The 'form' of bacteria is basically the general shape of a bacterium. The 'arrangement' is how the bacteria are arranged spacially, relative to each other. Let us first start off with a description of the general structure of bacteria.
That's probably because it is. It is very fun.
The 'form' of bacteria is basically the general shape of a bacterium. The 'arrangement' is how the bacteria are arranged spacially, relative to each other. Let us first start off with a description of the general structure of bacteria.
Bacteria are microscopic organisms. They are prokaryotes, meaning they do not have membrane-bound organelles. All bacteria have the following structures:
1. A cell/plasma membrane 2. A cell wall with peptidoglycan - Cell walls of bacteria (of the domain bacteria) have peptidoglycan while plants (of the domain eukarya) have cellulose. 3. Cytoplasm 4. Ribosomes 5. Free floating chromosome of DNA or RNA - It will be a circular-ish shape, unlike ours which is more like a beautiful blobby mess. There are also some structures that some bacteria have but others do not: 1. Pili - They protrude from the cell membrane and help bacteria to attach themselves to each other and other surfaces. They can also be used to transfer plasmids from one bacterium to another. 2. Capsule - A thick, liposaccharide layer that goes around the cell wall. It protects the bacterium. 3. Plasmid - Little rings of DNA that contain extra genes that are beneficial to the bacterium. 4. Flagella/flagellum - An organelle used to move the cell from place to place. A bacterium can have more than one flagella. |
Now that we have that down, let's look at form and arrangement.
There are three basic forms of bacteria: coccus, bacillus, and spirillum. 1. Coccus This means that the cell form is spherical. There are a few different kinds of arrangement for these: solo (singular bacterium), diplo (two stuck together), strepto (in a chain), staphylo (a cluster or group), tetrad (four in a square), and sarcina (group of eight arranged kind of in a cube, looks like a double tetrad). 2. Bacillus Also called rods. This means the cell form is longer than it is wide. These are generally seen solo, diplo, and strepto. 3. Spirillum This means the cell form is longer than it is wide with a curvature. These tend to be pathogenic and in a singular arrangement. |
The purpose of gram staining
Gram staining is used to differentiate bacteria based on the two ways the chemical make up of their cell walls can differ. It is also used to determine the chemical make up of the cell wall of a type of bacteria. After the bacteria sample you want to stain is on a slide, the procedure is as follows:
The amount of peptidoglycan in the cell walls of bacteria determines how susceptible or resistant they are to antibiotics. Bacteria with cell walls that have a thin layer of peptidoglycan are more resistant to antibiotics than bacteria with cell walls that have a thick layer of peptidoglycan.
- Apply Crystal Violet stain for 1-2 mins then rinse with dH2O
- Apply Gram's Iodine for 1-2 mins then rinse with dH2O
- Wash with 95% ethanol until the purple stops washing away (~5s), then rinse with dH2O immediately
- Apply Safranin for 1-2 mins then rinse with dH2O and blot dry
The amount of peptidoglycan in the cell walls of bacteria determines how susceptible or resistant they are to antibiotics. Bacteria with cell walls that have a thin layer of peptidoglycan are more resistant to antibiotics than bacteria with cell walls that have a thick layer of peptidoglycan.
Results of bacteria collections lab
Hannah's Results - Pre-Staining
1. Bacteria from my clarinet reed. There's white bacteria and yellowish white bacteria.
2. Bacteria from the bell of my clarinet (the bottom curved piece). There's mostly yellow bacteria but some orange and some pink/red.
3. Bacteria from the band microphone. There's one spot of white bacteria that looks a lot like what is on my reed.
4. The control section. No bacteria was placed here.
1. Bacteria from my clarinet reed. There's white bacteria and yellowish white bacteria.
2. Bacteria from the bell of my clarinet (the bottom curved piece). There's mostly yellow bacteria but some orange and some pink/red.
3. Bacteria from the band microphone. There's one spot of white bacteria that looks a lot like what is on my reed.
4. The control section. No bacteria was placed here.
Emily's Results
1. The control section. No bacteria was placed here, but bacteria from Emily's saxophone grew into it.
2. Bacteria from the microwave. None grew (bacteria probably doesn't have a good chance of growing in the interior of a microwave due to the heat)
3. Bacteria from Emily's saxophone. It's white and cloudy.
4. Bacteria from our friend, Renee's trombone. It is a vibrant golden yellow.
1. The control section. No bacteria was placed here, but bacteria from Emily's saxophone grew into it.
2. Bacteria from the microwave. None grew (bacteria probably doesn't have a good chance of growing in the interior of a microwave due to the heat)
3. Bacteria from Emily's saxophone. It's white and cloudy.
4. Bacteria from our friend, Renee's trombone. It is a vibrant golden yellow.
Hannah's Results - Gram Stained
The first is bacteria from my reed. It is staphylococcus and gram positive. Viewed on 10 x 40 magnification.
The second is bacteria from the band mic. It is staphylococcus and gram negative. Viewed on 10 x 40 magnification.
The third is bacteria from the bell of my clarinet. It is streptococcus and gram negative. Viewed on 10 x 40 magnification.
The first is bacteria from my reed. It is staphylococcus and gram positive. Viewed on 10 x 40 magnification.
The second is bacteria from the band mic. It is staphylococcus and gram negative. Viewed on 10 x 40 magnification.
The third is bacteria from the bell of my clarinet. It is streptococcus and gram negative. Viewed on 10 x 40 magnification.
Emily's Results - Gram Stained
The first is bacteria from Emily's saxophone. It is true bacillus (longer rods) and arranged in a solo pattern. It is gram positive. Viewed on 10 x 10 magnification.
The second is bacteria from Renee's trombone. It is strepto bacillus and gram positive. Viewed on 10 x 40 magnification.
The first is bacteria from Emily's saxophone. It is true bacillus (longer rods) and arranged in a solo pattern. It is gram positive. Viewed on 10 x 10 magnification.
The second is bacteria from Renee's trombone. It is strepto bacillus and gram positive. Viewed on 10 x 40 magnification.
nutrition: how bacteria obtain carbon and energy
There are four basic ways bacteria can obtain carbon and energy.
Photoautotrophs: These bacteria obtain energy from light (photo) and make their own carbon, which means it is an inorganic carbon source (autotrophic). They use light and inorganic carbon (like CO2) to make organic compounds. Chemoautotrophs: These bacteria obtain energy from inorganic compounds (chemo) and make their own carbon (autotrophic). Photoheterotrophs: These bacteria require energy from light (photo) to make ATP and also require an organic carbon food source (heterotrophic) which will probably be glucose (C6H12O6). Most bacteria do not do this because it is inefficient. Chemoheterotrophs: These bacteria consume organic carbon as their energy and carbon source. Again, it will probably be glucose. Most bacteria do this because it is efficient. |
Bacterial reproduction, antibiotics, and evolution
These are all related. In fact, bacterial resistance to antibiotics is a common, modern-day example of evolution happening right now. But how does it work? Let's start with bacterial reproduction.
Bacteria reproduce asexually, through binary-fission. This means they make clones of themselves. Every single piece of DNA/RNA that a bacterium has will be passed on to its offspring to make it identical to its parent. However, if bacteria were all the same, they would be really easy to kill and we wouldn't be facing the issue of antibiotic resistance. Bacteria have ways to create new combinations of genes that they carry. Bacteria carry genes in two different ways: in little circular, free-floating pieces called plasmids, and in the bigger, central piece of DNA/RNA that was passed on from their parent. Which plasmid is present in which bacteria varies, but they are all beneficial to the bacteria that carry them. Bacteria can gain new plasmids through three processes: transformation, conjugation, and transduction. Transformation is when bacteria take up plasmids from their environment, which generally happens through a process called heat shock. Conjugation is the transfer of plasmids from a bacterium to a bacterium through the pili. Transduction is the transfer of plasmids from virus to bacterium. The plasmids are not used unless they are needed.
Furthermore, antibiotics are aimed to kill bacteria. They aren't very picky about what kind of bacteria they kill, so they just wipe out whatever bacteria is susceptible to them, both the good and the bad. The key word in that sentence is "susceptible". Not all antibiotics are effective at killing all types of bacteria. Some antibiotics, such as penicillin, inhibit linkages in peptidoglycan molecules. Penicillin is effective for bacteria that have and need a lot of peptidoglycan, but not for bacteria that do not have or need a lot of peptidoglycan.
How does this connect to evolution? Well, let's say that a plasmid that a bacterium is carrying gives it resistance to an antibiotic. If that antibiotic is used, all of the bacteria that carry that plasmid will likely survive and end up reproducing, passing that plasmid on to their offspring. Also, if given time, the bacteria will be able to pass their useful plasmid on to their neighbours, ensuring their survival. Antibiotics change the bacteria's environment, thus placing evolutionary pressure on the bacteria. Through the process of natural selection, the bacteria that have the plasmid that gives them antibiotic resistance (and are therefore the fittest) are "selected" for survival and are then able to pass on their genes to the future generation. Seeing as bacteria reproduce quickly, widespread resistance can occur quickly. Possessing a gene that gives antibiotic resistance isn't the only way bacteria can survive antibiotics. As I stated in the above paragraph, some antibiotics are not effective against certain bacteria. Using an antibiotic that is only effective against bacteria with a thick layer of peptidoglycan causes directional selection, and the bacteria that have a thin layer of peptidoglycan protected by a liposaccharide layer are the ones that are able to survive and reproduce. Directional selection and natural selection are both types of evolution. Therefore, antibiotic resistance is an example of evolution.
Bacteria reproduce asexually, through binary-fission. This means they make clones of themselves. Every single piece of DNA/RNA that a bacterium has will be passed on to its offspring to make it identical to its parent. However, if bacteria were all the same, they would be really easy to kill and we wouldn't be facing the issue of antibiotic resistance. Bacteria have ways to create new combinations of genes that they carry. Bacteria carry genes in two different ways: in little circular, free-floating pieces called plasmids, and in the bigger, central piece of DNA/RNA that was passed on from their parent. Which plasmid is present in which bacteria varies, but they are all beneficial to the bacteria that carry them. Bacteria can gain new plasmids through three processes: transformation, conjugation, and transduction. Transformation is when bacteria take up plasmids from their environment, which generally happens through a process called heat shock. Conjugation is the transfer of plasmids from a bacterium to a bacterium through the pili. Transduction is the transfer of plasmids from virus to bacterium. The plasmids are not used unless they are needed.
Furthermore, antibiotics are aimed to kill bacteria. They aren't very picky about what kind of bacteria they kill, so they just wipe out whatever bacteria is susceptible to them, both the good and the bad. The key word in that sentence is "susceptible". Not all antibiotics are effective at killing all types of bacteria. Some antibiotics, such as penicillin, inhibit linkages in peptidoglycan molecules. Penicillin is effective for bacteria that have and need a lot of peptidoglycan, but not for bacteria that do not have or need a lot of peptidoglycan.
How does this connect to evolution? Well, let's say that a plasmid that a bacterium is carrying gives it resistance to an antibiotic. If that antibiotic is used, all of the bacteria that carry that plasmid will likely survive and end up reproducing, passing that plasmid on to their offspring. Also, if given time, the bacteria will be able to pass their useful plasmid on to their neighbours, ensuring their survival. Antibiotics change the bacteria's environment, thus placing evolutionary pressure on the bacteria. Through the process of natural selection, the bacteria that have the plasmid that gives them antibiotic resistance (and are therefore the fittest) are "selected" for survival and are then able to pass on their genes to the future generation. Seeing as bacteria reproduce quickly, widespread resistance can occur quickly. Possessing a gene that gives antibiotic resistance isn't the only way bacteria can survive antibiotics. As I stated in the above paragraph, some antibiotics are not effective against certain bacteria. Using an antibiotic that is only effective against bacteria with a thick layer of peptidoglycan causes directional selection, and the bacteria that have a thin layer of peptidoglycan protected by a liposaccharide layer are the ones that are able to survive and reproduce. Directional selection and natural selection are both types of evolution. Therefore, antibiotic resistance is an example of evolution.