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difference between bacteria, virus and fungi

Microbes like fungi, bacteria, and virus are tiny organisms present in almost all ecosystems, playing an important role in the ecology. So they can be found just about anywhere around us. Moreover, they are capable of associating with other living creatures, including plants, animals, and humans, meaning they can also be inside us.

When finding their way into the human body, these small organisms can participate in different biological processes. That doesn't mean you should regard them as harmless visitors in your body. Fungi, bacteria, and especially viruses can interfere with a number of body functions and cause different types of diseases in humans.

We are not here to tell you how to treat or prevent diseases caused by aforementioned organisms. Instead, we are going to talk about the main differences between them. Without further ado, let’s dig into it.

Fungi

Bacteria

Viruses

Threads (Mushrooms) or single cells (Yeast)

Need a microscope to be viewed

Smaller than bacteria

Need moisture, warmth nutrients

Need moisture, warmth nutrients

Depend on living hosts

Anaerobes and Aerobes

Anaerobes and Aerobes

‘Non’ living

Saprophytes and Parasites

Saprophytes and Parasites

Parasites

Can be useful or harmful

Can be useful or harmful

Always harmful

Harmful: May be poisonous, cause diseases, decay food  

Harmful: Food poisoning, cause diseases like Cholera, TB, tetanus, pneumonia, sore throat, etc.

Cause diseases like Mumps, Measles, Aids, Poli, Cold sores, Flu, etc.

Uses: Antibiotics, food, bread and beer making

Uses: Rot things, antibiotics


Bacteria vs Fungi


Let's get started with the difference between fungus and bacteria.

All living creatures on the Planet Earth can be divided into eukaryotes and prokaryotes depending on where the deoxyribonucleic acid (DNA) exists. While the nucleus in a eukaryotic cell is surrounded by a nuclear membrane, prokaryotes don't have any nuclear membrane around the nucleus. According to this classification, fungi are eukaryotic organisms whereas bacteria are prokaryotic organisms.

Bacteria are unicellular organisms, while fungi are usually multicellular like Penicillium. However, they can also be discovered as single-celled organisms such as Saccharomyces (yeast). The cellular makeup of these microscopic organisms is completely different. While both bacteria and fungi have cell walls, the inner components are dissimilar. The nuclei of fungi cells contain different organelles like vacuoles, chromosomes, ribosomes, Golgi bodies, endoplasmic reticulum, and mitochondria. Bacteria, on the other hand, don't have nuclei and organelles, so they are not able to reproduce sexually.

To break it down for you, here are the fundamental differences between fungi and bacteria:

  • Fungi are eukaryotes; bacteria are prokaryotes.

  • Fungi only appear as heterotrophs whereas bacteria can either be heterotrophs or photoautotrophs.

  • Bacteria are unicellular microorganisms invisible to the naked eye, while fungi are larger and more complex organisms that typically consists of numerous cells.

  • Fungi have a nuclear membrane in contrast to bacteria.

  • Different compositions within cell walls.

  • Fungi have a wide range of shapes while bacteria only have three distinct shapes.

  • Bacteria can occur in extremely harsh environments like volcanoes, alkaline, acid, and deep-sea water, while fungi can't occur or survive in such harsh places.


Fungi


Fungi have various forms and shapes — from microscopic fungi (mold and yeast) to shelf fungi and mushrooms. These eukaryotic multicellular organisms contain a well-defined nucleus. They've been separately classified for plants and animals. In fact, fungi have a unique structure of the body that clearly differs from other animal and plant kingdoms.

Fungi are composed of a large number of hyphae, branching filaments that look like long hollow tubes or threads. Intertwined with each other, they form a dense network called mycelium. In other words, mycelium (also known as mold) is made up of all hyphae within a fungus. 

There is a rigid wall around each hypha which is made of chitin — the same compound that creates the insect exoskeleton. Also, there are specific elongations at the tips of hyphae that allow them to branch and grow all over the place. This is how mycelium forms. As this complex network of hyphae grows, a fungus generates large fruiting bodies along with other structures. This growing process is common to all fungi except yeasts, which develop through budding.

Both multicellular and unicellular fungi have an inelastic cell wall that consists of chitin, a fibrous nitrogen substance which contains polysaccharide. As mentioned earlier, there are a variety of organelles inside fungi cells. They are surrounded by either one or two membranes. Plus, there are lots of histone proteins carrying genetic material (DNA). Additionally, bacteria contain a wide variety of environments, including water, soil, air, and dust. 

It is also important to mention spores, cells produced by fungi that are capable of developing into new fungi. Those small one-celled units may carry both asexual and sexual reproductions. Sexual reproduction occurs when lots of gametes start uniting to make a unique spore. Reproductive spores are placed in fruiting bodies of fungi. When it comes to asexual reproduction, spores are created on the hyphal tips.

In regard to nutrition, fungi feed on the decayed organic substances, so they are saprophytes. That's why fungi commonly inhabit soil that contains organic waste. In order to feed, fungi release numerous digestive enzymes which are capable of breaking down organic matter. The dissolved food is then absorbed through cell walls. Unlike autotrophic bacteria that manufacture their own food from chemical energy or light, fungi are heterotrophs since they can't produce their own food.

Based on the kind of reproduction, fungi can be classified into four phyla:

  • Zygomycota (zygote fungi)

  • Basidiomycota

  • Ascomycota, and

  • Deuteromycota (Fungi Imperfecti)


Also read Fungi Life Cycle and types of fungi.


Bacteria


Bacteria are considered to be the oldies group of living beings. They feature a very simple cell structure and most of them are one-celled. However, they may form specialized structures such as clusters or chains.

These prokaryotic microorganisms are from 0.1- 10µm long, meaning they can be only seen under an electron microscope. The DNA of bacteria has a circular shape and isn't enclosed with histones. Even though some organelles can exist in a bacterial cell, they aren't enveloped by membranes.

One bacteria comprises approximately 10,000 prokaryotic ribosomes which are situated in the cytoplasm. Those cellular components make up about 30 percent of the cell weight. There are 3 large RNA molecules and more than 50 proteins within a bacterial ribosome.

It should be noted that ribosomes of bacteria are different from eukaryotic ribosomes in terms of protein production and function. That difference enables antibiotics to inhibit the activity and destroy bacterial ribosomes while keeping the human ribosomes unaffected.

Concerning the cell wall, it's made up of Peptidoglycan (also known as murein), which consists of amino acids and polysaccharide. The bacterial cell contains a cell membrane that's made of cytoplasm. According to the structure of the cell wall, we can categorize bacteria into 2 different groups: Gram-positive and Gram-negative bacteria. The cell wall has an influence on the bacterium shape. Bacteria can occur in 3 different shapes:

  • Bacillus is a rod-shaped bacterium

  • Coccus is a rounded, oval bacterium

  • Spirillum is bacterium featuring a spiral shape

Please note that there are some bacteria without definite shape, as they lack cell walls. They are termed as mycoplasma.

There is another classification of bacteria based on how they get energy. Photoautotrophs (photoautotrophic bacteria) carry out photon capture so as to acquire chemical energy. They actually produce their own energy using carbon dioxide and light. As you may already know, that process is called photosynthesis. Heterotrophs can't make food this way, meaning they have to absorb or eat it. This is the reason why these organisms are also referred to as consumers.

Lastly, let's mention that there are two types of reproduction in bacteria:

  • Asexual reproduction - When bacteria multiply by binary fission; it’s kind of like duplication whereby parent bacteria divide into 2 daughter cells that have identical sizes.

  • Sexual reproduction - When bacteria replicate by genetic recombination; this process may involve bacterial transduction, transformation, or conjugation.


Viruses vs Bacteria


Viruses and bacteria are both minute organisms that are the cause of many diseases in humans. Despite the fact that these microbes have quite a few similar characteristics, they're very different as well.

As far as the size is concerned, viruses are around 1,000 times smaller than bacteria.  While you will need an ordinary light microscope to see bacteria, viruses are only visible under advanced optical instruments such as electron microscopes. Their size can be anywhere from 20 nm to 400 nm in diameter. The pandoraviruses are the biggest viruses known; they are about micrometer (1000 nanometers) in size.

The amount of proteins and nucleic acid in viruses mostly determine their shape and size. Typically, viruses have polyhedral (spherical), helical-shaped, or rod-shaped capsids. However, there are some exceptions like bacteriophages, which feature very complex shapes.

Bacteria are considered prokaryotic cells, as they display all characteristics typical of living organisms. Viruses, by contrast, cannot be regarded as cells. They are actually particles or integral parts of nucleic acid (RNA or DNA) enclosed within protein shells. So, they exist somewhere between non-living and living organisms.

While viruses have a certain genetic material, they do not have organelles and a cell wall. Therefore, viruses solely rely on their hosts for replication and energy production. In fact, viruses make use of the organelles of the host cell's to replicate. They multiply by injecting their genetic material into a host cell. That's how they create viral components. Once the new viruses form and mature, they start moving on in order to infect other cells.


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