Eubacteria are a very important topic in microbiology so it’s important to know as much as possible as there is about it. However, a lot of microbiologists often turn up empty handed after searching for an in-depth guide about eubacteria – but no more!
If you are looking for a comprehensive guide that contains everything you need to know about eubacteria, then check out the guide below!
Here, we are going to go through all of the characteristics of eubacteria as well as checking out some examples and comparing this domain to archaebacteria.
So, let’s dive in!
Overview Of Eubacteria
Eubacteria is a genus that contains a lot of the most common groups of bacteria.
This is why some microbiologists refer to eubacteria as ‘true bacteria’ as it is made up of a lot of common species of bacteria that we come into contact with and are familiar with.
There is only one type of bacteria that fails to fall under this title and that type is archaebacteria.
Found under the Bacteria domain, eubacteria are single cell microorganisms that lack a nucleus yet contain DNA within their single circular chromosome.
The domain is also made chiefly of prokaryotes (this means that they have the ability to form spores) although the species are generally highly diverse when it comes to defining factors including metabolism, habitats, and morphologies.
Because of this, a lot of eubacteria are parasites, pathogenic, or responsible for disease in both plant and animal species, and others are free living with beneficial potential for humans.
Eubacteria reproduce through a process known as binary fission or budding, which involves growing an offspring ‘bud’ that separates from the parent once it has grown enough to become independent.
They then form large colonies with an extracellular structure that provides a unique form of protection to the colony.
Characteristics Of Eubacteria
Because Eubacteria covers so many different types of bacteria, there are a lot of defining characteristics that make a bacteria a ‘eubacteria’.
So, let’s take a look at a few of these characteristics. Then, you may be able to guess a few examples of bacteria that are also eubacteria as they feature some of the same characteristics of common eubacteria.
One of the most defining characteristics of eubacteria is the structure of its cell, but especially its cell wall.
Because eubacteria are prokaryotes, they do not feature any form of membrane-bound organelles.
Instead, the cell wall of a eubacteria is made of peptidoglycans (a polymer made of sugars and amino acids that forms a rigid layer that surrounds cytoplasmic membrane of bacteria) in a cross linked chain pattern connected through peptide bonds.
This macromolecular layer helps the eubacteria to stay the same shape and size even if they change environments and conditions.
Small sized molecules can still diffuse through this cell wall but larger molecules and even ions require carrier proteins or channel proteins in order to be able to enter the cell of a eubacteria.
We touched earlier on how diverse eubacteria are when it comes to habitats and a result of this is that eubacteria are shown to have a lot of different metabolic pathways.
This is true especially when compared to eukaryotes, as eubacteria show high diversity when it comes to energetic sources.
Some eubacteria can draw energy from organic matter while others do so through the oxidation of mineral compounds such as nitrates or methane.
This is why eubacteria are so important in our worlds’ ecosystem – they are important when it comes to converting materials into compounds plants and animals use.
For example, eubacteria can produce nitrates that plants then use to make proteins, amino acids, and other compounds that are vital for their growth and survival.
A few examples of the different nutritional modes found in eubacteria include autotrophic bacteria which produce their food through photosynthesis.
Heterotrophic bacteria which draw nutrients from their surrounding environment, both strictly or facultatively.
Aerobic bacteria which can either survive purely on oxygen or and switch to anaerobic respiration whenever there is an absence of oxygen to survive.
Also, strictly or facultatively anaerobic bacteria are also considered to be eubacteria (these are bacteria that survive in the absence of oxygen or can switch to aerobic respiration when oxygen is present).
This just shows how diverse eubacteria is when it comes to modes of metabolism.
This is due to the fact that chemical compounds come in such a wide variety that they can produce the right amount of energy in lots of different environments.
So, eubacterias can survive in lots of different environmental conditions due to their diverse metabolisms and ability to make the most of what sources of energy they have near.
Eubacteria have two main modes of reproduction but both are a form of asexual reproduction.
However, it is worth mentioning that some species have been seen exchanging genetic material via cell contact but most microbiologists agree that eubacteria reproduce through some form of asexual reproduction.
One such mode of asexual reproduction is binary fission. This is the most commonly seen form of reproduction witnessed with eubacteria.
It involves the genetic material of the bacteria replicating itself, producing two strands of the same DNA, and then dividing without mitosis.
Some other forms of asexual reproduction that various species of bacteria use to reproduce includes fragmentation, budding, and conidia formation.
However, binary fission remains to be the most common mode of reproduction seen in eubacteria.
When in unfavorable conditions, some eubacteria will undergo endospore formation.
This formation is mostly performed by gram-positive bacteria and cyanobacteria, which means that a lot of eubacteria are capable of undertaking this process.
Endospore formation occurs when the organism (in this case, the eubacteria) is stuck in an environment that threatens its survival.
As a result, dehydrates its cytoplasm and chromosomes then forms a thick wall around its cell.
This protects the organism from its environment and allows it to remain resistant for long periods of time. Some eubacteria remain in endospore formation for decades at a time.
When the environmental conditions are once again favorable, then the protoplast absorbs water and allows the protoplast to swell up and dipicolinic acid to leak.
The protoplast will then break the spore cover of the eubacteria, allowing the cell to remerge and continue thriving.
Examples Of Eubacteria
Here, we are going to take a look at some examples of eubacteria. This will help you gain a better understanding of how diverse eubacteria can be even though they all share similar characteristics in some way.
So, let’s take a closer look at some of the most common examples of eubacteria!
One of the largest and most diverse groups of eubacteria is proteobacteria.
Proteobacteria is a prokaryote type of bacteria that includes many other types of parasitic bacteria including salmonella, escherichia, and helicobacter.
There are also free-living forms of bacteria in this group too, but all are gram-negative bacteria.
Gram-negative bacteria are bacteria that feature cell walls made of thin peptidoglycan that does not retain its primary stain, which means that the crystal violet of its cell will wash out when exposed to ethanol.
There are several members of this group found under the umbrella of proteobacteria and as such, eubacteria.
These members include Alpha, Beta, Delta, Epsilon, Gamma, and Zeta proteobactiera (named based on their rRNA sequences)
Proteobacteria are also further divided into subgroups through their metabolism. We touched on earlier how diverse the metabolisms of different eubacterias are and this can clearly be seen in proteobacteria.
There are purple bacteria (that contain chlorophylls), chemoautotrophic proteobacteria (the free-living members) and chemoheterotrophic proteobacteria (sometimes also known as enteric bacteria).
Spirochetes are eubacteria that are defined by their spiral morphology, which means that they are very flexible due to their peptidoglycan cell wall that is covered with axial fibrils.
This architecture allows them to move around and appear like very wavy lines when viewed under a microscope.
Spirochetes are very interesting in the field of microbiology because they tend to break the mold when it comes to certain characteristics.
For example, they stain terribly despite being a gram-negative eubacteria and thus this characteristic makes them difficult to view under a microscope.
It is also capable of moving independently due to its flexibility, meaning that it can spin and flex all thanks to its internal flagellar filament.
This group also contains both pathogenic and free-living organisms, and is known for being the cause of diseases like borrelia burgdorferi in both humans and animals alike.
This group of bacteria will definitely be familiar to you because chlamydias bacteria are a common cause of a lot of different issues and diseases among animals and humans.
For example, chlamydia trachomatis is the world’s most common cause of blindness and one of the most common causes of non-gonococcal urethritis in the US!
Chlamydia bacteria are a part of the Chlamydiaceae family and are grouped as a gram-negative type of bacteria.
They are also defined by their other characteristics including their dimorphic nature.
Cyanobacteria gets its name from the blue-color of the algae it inhibits. It is a type of eubacteria that is made of photosynthetic prokaryotes that are able to thrive in lots of different environments.
This means that cyanobacteria can be found anywhere from lakes and ponds to within desert soil.
It is a free living species of bacteria that sometimes forms symbiotic relationships with other organisms like fungi to form lichens, a complex organism that is born from fungi and algae.
Not only that, but cyanobacteria also has a range of other characteristics that defines it from its fellow eubacteria.
It has a very thick, gelatinous cell wall which helps it thrive as a diverse morphological species. It also has the potential to live as a single cell or in colonies or as part of a multicellular organism.
Overall, cyanobacteria is definitely an interesting type of eubacteria that most microbiologists look forward to studying.
Not all eubacteria are gram-negative. Most are actually gram-positive and yet they can differ from one another due to factors like their metabolism and their mode of gathering energy from their sources.
For example, some gram-positive eubacteria photosynthesise to feed themselves while others draw their nutrients from the matter that surrounds them.
Due to their gram-positive characteristic, these bacterias are violet in color when they appear underneath a microscope because they retain their crystal dye even after being exposed to ethanol.
This is because unlike gram-negative bacteria, gram-positive bacteria feature thick peptidoglycan cell walls that help retain their dye.
As for morphology, gram-positive bacteria also vary from cocci to spherical to rod-like.
They can also be found in a range of environments both in the water and on land, and some can still produce endospores (a defining characteristic of eubacteria).
Eubacteria Vs Archaebacteria
When you first start to study microbiology, a common issue is that many people mix up eubacteria and archaebacteria.
This is because both are two different domains of the same kingdom (Monera) which means that both share a few similarities.
Such similarities between the two include that they are both eubacteria and archaebacteria are both single celled organisms called prokaryotes.
But there are also so many differences between these two domains that makes it important for you to know the difference.
In this section, we are going to be looking at archaebacteria and how it differs from eubacteria so you can understand the key differences between the two domains.
What Is Archaebacteria?
Archaebacteria are single celled microorganisms that are capable of living in very extreme environments.
Like eubacteria, it is one of the domains of the monera kingdom and is considered to be one of the first forms of life that evolved on Earth.
This makes them an ancient bacteria that can be found in a range of different environments including soils and oceans. They can also be found on other organisms including on human skin.
This type of ancient bacteria is vital as it plays a huge part in both the carbon and nitrogen cycle, but are not pathogenic or parasitic.
They can draw their nutrients from a range of different sources, making them very diverse when it comes to metabolism.
Also like eubacteria, they reproduce asexually through a range of methods including fragmentation, budding, and binary fission.
There are three main types of archaebacteria. These types include methanogens, halophiles, and thermophiles.
Methanogens live in oxygen free environments which means that it calls a range of places home. These habitats include digestive tracts of different animals (where they produce methane gas), lake sediments and in marshes.
Halophiles survive in salt water areas, specifically in areas with higher concentrations of salt. Thermophiles live in water areas with high temperatures, such as in acid sulfur springs. This is why they have the name ‘thermo’-philes.
Some example archaebacteria include ferroplasma, pyrobaculum, lokiarchaeum, halobacterium, and thermoproteus.
So, now you know more about archaebacteria, let’s take a look at some of the key differences between this type of bacteria against eubacteria.
While this may seem like an obvious choice, the alternative names of both these types of bacteria reveal a lot more about their differences.
Archaebacteria is known as ‘ancient’ bacteria because it is believed to be older than eubacteria. On the other hand, eubacteria is also known as ‘true’ bacteria because it is the more common of the two types.
So, just from their alternative names alone, we can see that archaebacteria is older than eubacteria while eubacteria is more common than archaebacteria.
Shape And Size
An individual archaebacterium is smaller than an individual eubacterium, as it measures 0.1 to 0.15 μm in diameter compared to 0.5 μm.
Not only that, but the morphology of both groups are different. Archaebacteria are more commonly found in spheres, rods, spiral, flat, squares and plate shapes.
Eubacteria, on the other hand, are found in cocci, rods, filaments, spirochetes, and vibrio shapes.
So, while there is some overlap when it comes to shapes, they are generally very different in appearance.
As we mentioned earlier, eubacteria are the more common of the two. This is because eubacteria is so diverse in its metabolism that it is capable of living pretty much anywhere on Earth thus it has a lot more habitats available to it.
Archaebacteria are not as common because they can only survive in certain extreme habitats.
They can be found in the same extreme environments as eubacteria, but nowhere else. So, archaebacteria and eubacteria also have different common habitats.
Complexity And Structure
Perhaps because they are older, archaebacteria are known for their simple organization while eubacteria are agreed to be the more complex between the two.
There are also important differences in their structure as their cell walls are made of different materials.
Archaebacteria have cell walls made from pseudo peptidoglycans, while eubacteria have cell walls made of peptidoglycans along with muramic acid. This is another factor as to why eubacteria can survive in so many different environments.
The membrane lipids of archaebacteria are also different from eubacteria when it comes to their structure.
Archaebacteria’s membrane lipids are either branched, ether linked, or in aliphatic chains. Eubacteria membrane lipids are ester linked, or in straight chains of fatty acids.
When it comes to subtypes, archaebacteria has three while eubacteria only has two.
The three subtypes of archaebacteria are covered above (methanogens, halophiles, and thermophiles) while the two subtypes of eubacteria are gram-positive and gram-negative.
And that is everything you need to know about eubacteria!
We hope that this guide has been helpful to you when it comes to understanding eubacteria including what their characteristics are and how they differ from the other domain of the monera kingdom, archaebacteria.
Check out the information above if you ever need to refresh your mind about all the important defining qualities of eubacteria and what makes them so different from archaebacteria.
If you are curious about learning more about different types of eubacteria, then check out the examples we have given above.
This will help you understand the characteristics of eubacterias even more along with how each species differs from each other. Good luck with your studies!
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