Are you studying for a biology exam? Forced to stay in bed with the flu and curious to know what type of microorganism is causing you to get sick? While bacteria and viruses can cause you to get sick in similar ways, they are actually very different organisms with very different properties. Learning the difference between the two can help you stay up-to-date with your current medical treatment and give you a better understanding of the complex biological systems that run inside your body all the time. You can learn how to tell the difference between bacteria and viruses not only by going through the basics about them, but also by examining them under a microscope and discovering more about their composition and function.
Step
Part 1 of 2: Learning the Difference
Step 1. Learn the basic differences
There are major differences between bacteria and viruses in terms of size, origin and impact on the body.
- Viruses are the smallest and simplest form of life; Viruses are 10 to 100 times smaller than bacteria.
- Bacteria are single cell organisms that can live both inside and outside other cells. Bacteria can live without a host cell. In contrast, viruses are just intracellular organisms, which means they can infiltrate the host cell and then live inside the cell. Viruses work by changing the genetic material of the host cell from its normal function to producing the virus itself.
- Antibiotics cannot kill viruses, but they can kill most bacteria, except for bacteria that have become resistant to antibiotics. Misuse and overuse of antibiotics can lead to bacterial resistance to antibiotics. Antibiotics will be less effective against bacteria that may be harmful. Gram-negative bacteria are highly resistant to treatment using antibiotics, but can be killed by some antibiotics.
Step 2. Recognize the differences in terms of reproduction
Viruses need to have a living host in order to reproduce, such as plants or animals. Meanwhile, most bacteria can grow on inanimate surfaces.
- Bacteria have all the "equipment" (cell organelles) needed to grow and reproduce, and usually reproduce asexually.
- In contrast, viruses basically carry information-for example, DNA or RNA, wrapped in a protein coat and/or membrane. Viruses require host cell equipment in order to reproduce. The "legs" of the virus will stick to the cell surface and the genetic material contained in the virus is transferred into the cell. In other words, viruses are not really "living" things, but are basically information (DNA or RNA) that floats around until it finds a suitable host.
Step 3. Determine whether the organism has a beneficial effect on the body
As hard as it sounds to believe, there are so many tiny organisms that live inside (but apart from) our bodies. In fact, in terms of pure cell count, the vast majority of people comprise approximately 90% of microbial life and only 10% of human cells. Many bacteria live quietly in our bodies; some even perform very important functions, such as producing vitamins, breaking down waste, and producing oxygen.
- For example, much of the digestive process is carried out by a type of bacteria called "intestinal flora." These bacteria also help maintain the pH balance in the body.
- While many people are familiar with "good bacteria" (such as gut flora), there are also "good" viruses, such as bacteriophages, which "hijack" the bacterial cell mechanism and kill cells. Researchers from Yale University have created a virus that could help kill brain tumors. However, most viruses have not been shown to be capable of performing functions that are beneficial to humans. Usually viruses are only harmful.
Step 4. Verify whether the organism meets the criteria for life
Although there is no accurate official definition of what is called life, scientists agree that without a doubt, bacteria are living things. Meanwhile, viruses are more like zombies: not dead, but definitely not alive. For example, viruses share some of the characteristics of life, such as the presence of genetic material, evolve over time through natural selection, and can reproduce by replicating themselves. However, viruses do not have their own cellular structure or metabolism; Viruses need a host cell in order to reproduce. In other words, viruses are essentially non-living. Consider the following:
- When the virus has not invaded the cells of other organisms, basically the virus is completely inactive. There are no biological processes that occur in the body of the virus. Viruses cannot metabolize nutrients, produce and excrete waste, or move on their own. In other words, viruses are very similar to inanimate objects. Viruses can remain in a "dead" state for a long time.
- When the virus comes into contact with an invading cell, the virus attaches itself and a protein enzyme dissolves the cell wall so that the virus can channel its genetic material into the cell. At this stage, when the virus hijacks the cell to reproduce, it begins to exhibit one important characteristic of life: the ability to transfer its genetic material to the next generation, thereby producing more organisms that are exactly like the virus itself.
Step 5. Identify common disease causes from bacteria and viruses
If you have a disease and know what it is, finding out if you have a bacteria or a virus can be as easy as looking up information about the disease itself. Common diseases with bacterial and viral causes include:
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Bacteria:
Pneumonia, food poisoning (usually caused by E. coli), meningitis, strep throat, ear infections, wound infections, gonorrhea.
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Virus:
influenza, chickenpox, common cold, Hepatitis B, rubella, SARS, measles, Ebola, HPV, herpes, rabies, and HIV (the virus that causes AIDS).
- Note that some illnesses, such as diarrhea and the flu, can be caused by any type of organism.
- If you don't know your exact disease, it will be more difficult to tell the difference between bacteria and viruses, because the symptoms of each organism can be difficult to distinguish. Both bacteria and viruses can cause nausea, vomiting, increased body temperature, fatigue, and feeling unwell. The best (and sometimes the only) way to determine whether you have a bacterial or viral infection is to see a doctor. The doctor will perform laboratory tests to determine what type of infection you have.
- One way to determine whether you have a virus or bacteria is to assess the effectiveness of your current antibiotic treatment. Antibiotics such as penicillin can only help if you have a bacterial infection, not a viral infection. This is why you can only take antibiotics if prescribed by your doctor.
- Most viral infections and illnesses, including the common cold, have no cure, but there are antiviral medications that can often help manage or limit the symptoms and severity of illness.
Step 6. Use this simple table to examine the basic differences between bacteria and viruses
While there are more differences than listed here, below are the most important ones
| Organism | Size | Structure | Reproduction Method | Handling | Life? |
|---|---|---|---|---|---|
| Bacteria | Larger (about 1000 nanometers) | Single cell: peptidoglycan/polysaccharide cell wall; cell membrane; ribosomes; Free floating DNA/RNA | Asexual. Imitate DNA and reproduce by fission (splitting). | Antibiotics; antibacterial cleaner for external sterilization | Yes |
| Virus | Smaller (20-400 nanometers) | Cellless: simple protein structure; no cell walls or membranes; no ribosomes, DNA/RNA wrapped by a protein coat | Hijacks host cells, making them duplicate viral DNA/RNA; the new virus is removed from the host cell. | There is no known cure. Vaccines can prevent disease; symptoms can be treated. | Not known; does not meet the general standard of living. |
Part 2 of 2: Analyzing Microscopic Features
Step 1. Look for the presence of the cell
Regarding structure, bacteria are more complex than viruses. Bacteria are organisms known as unicellular. This means that each bacterium consists of only one cell. On the other hand, the human body contains trillions of cells.
- Meanwhile, viruses do not have cells at all. Viruses are made up of a protein structure called a capsid. Although this capsid contains the genetic material of the virus, it lacks true cell features, such as a cell wall, carrier proteins, cytoplasm, organelles, and so on.
- In other words, if you look at a cell using a microscope, you are looking at bacteria, not viruses.
Step 2. Check the size of the organism
One of the quickest ways to tell the difference between bacteria and viruses is to see if you can see them with a regular microscope. If you can see it, it's not a virus. Viruses are generally about 10 to 100 times smaller than normal bacteria. Viruses are so small that you can't see them with a normal microscope other than their impact on a cell. You need an electron microscope or other very high power microscope to see viruses.
- Bacteria are almost always much larger than viruses. In fact, the largest viruses are only as big as the smallest bacteria.
- Bacteria tend to have dimensions of one to several micrometers (1000+ nanometers). In contrast, most viruses are less than 200 nanometers in size, which means they cannot be seen with most existing microscopes.
Step 3. Examine the ribosomes (and the absence of other organelles)
Although bacteria have a number of cells, they are not complex cells. Bacteria do not have a nucleus and any organelles other than ribosomes.
- You can find ribosomes by looking for small simple organelles. In a picture of a cell, ribosomes are usually depicted with dots and circles.
- In contrast, viruses do not have any organelles, including ribosomes. In fact, apart from an outer protein capsid, a few simple protein enzymes, and genetic material in the form of DNA/RNA, there is not much else in the structure of most viruses.
Step 4. Observe the reproductive cycle of the organism
Bacteria and viruses are not like most animals. Both do not have sex or exchange genetic information with other organisms of the same type to reproduce. However, this does not mean that bacteria and viruses have the same way of reproducing.
- Bacteria reproduce asexually. To reproduce, bacteria replicate their own DNA, elongate, and divide into two daughter cells. Each daughter cell gets a copy of the DNA, making it a clone (a perfect copy). Usually you can see this process happening with a microscope. Each daughter cell will grow and eventually divide again into two cells. Depending on the species of bacteria and the external conditions, bacteria can multiply very quickly in this way. You can see this process using a microscope and distinguish bacteria from ordinary cells.
- On the other hand, viruses cannot reproduce on their own. Instead, the virus attacks other cells and uses the system in the body to make new viruses. Eventually, so many viruses are formed that the attacked cell bursts and dies, releasing new viruses.
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