Eubacteria: Definition, Characteristics, Structure, Classification & Examples

sinaumedia Literasi – Did you know that after Carl Woose did a molecular analysis, the Archaebacteria which were originally grouped as Eubacteria in Kingdom Monera are now a separate group. Kingdom Monera is no longer used and instead appears the kingdom Archaebacteria and Eubacteria. Both are distinguished by genetic differences. Meanwhile, the similarity between Archaebacteria and Eubacteria is that both do not have a cell nucleus membrane, so they are also known as prokaryotic organisms. Check out a more complete explanation of Eubacteria below, Sinaumed’s!


In general, the notion of eubacteria (bacteria) is a unicellular (one-celled) organism that does not have a cell nucleus membrane (prokaryotic) generally does not have chlorophyll in its cell wall. The term eubacteria comes from the Greek word eu, which means true. Eubacteria include most of the prokaryotic organisms that live anywhere (cosmolipin). Eubacteria is also known as Bacteria or bacteria.

The term bacteria comes from bacterion which means small rod. Bacteria were first discovered in 1674, by a Dutch scientist, namely Antony van Leuuwenhoek who was also the inventor of the single lens microscope. The term bacteria was introduced by Ehrenberg in 1828. The science that studies bacteria is called a bacteriologist.

Eubacteria are microscopic single-celled organisms. Eubacteria are sometimes referred to as “true bacteria,”. Most of the organisms that we think of as “bacteria” are eubacteria. Eubacteria are at the heart of serious debate in scientific classification which is reshaping the traditional hierarchy of “Kingdom, Phylum, Class, Order, Family, Genus, and Species.”

Originally, Eubacteria were considered part of the kingdom Prokaryota, sometimes called “Monera,” along with their relatives the Archaebacteria. Prokaryotic organisms such as bacteria are primarily defined by the absence of a cell nucleus. This makes them distinct from the evolution of other living organisms, and has led to a number of innovative adaptations. Many prokaryotes are single-celled, although this is not always a requirement for membership in this kingdom. Apart from the kingdom Prokaryota, biologists have also classified organisms into Animalia, Fungi, Plantae, and Protista.

To find out more about various other types of bacteria as well as viruses and fungi, you can read the book Biology Encyclopedia Volume 2: Bacteria, Viruses & Protists, Fungi.


The kingdom Eubacteria are the true bacteria. They have countless roles, including the decomposition and recycling of nutrients, digestion and disease. The general characteristics of eubacteria are as follows:

  • Generally not chlorophyll
  • The shape varies
  • Do not have a nuclear membrane or prokaryotes
  • Size between 1 s / d 5 microns
  • Living as a parasite or free (cosmolipit) or pathogen
  • Unicellular (single-celled)
  • Eubacteria are prokaryotic unicellular organisms.
  • Eubacteria with cell walls composed of peptidoglycan (sugar and protein).
  • Eubacteria body size is around 1-5 microns.
  • Eubacteria reproduce by dividing, conjugation, transformation and transduction (transfer of some of the genetic material through an intermediary virus).
  • Eubacteria can secrete mucus onto the surface of the cell wall to form a capsule.
  • There are eubacteria that have flagella and there are eubacteria that do not have flagella.
  • Eubacteria cosmopolitan life means that it can live in all places, for example on land, air, water, even the human body.
  • When in an unfavorable environment Eubacteria will form endospores.
  • There are eubacteria that have chlorophyll and some eubacteria that do not have chlorophyll. Eubacteria often engage in symbiotic relationships with other organisms. This is a close interaction between two different species.
  • Are organisms that are single-celled or unicellular. The nucleus of a bacterial cell does not have a nuclear membrane or in prokaryotes. Third, the size of the bacterial cell ranges from 1 – 5 µm, where every 1 µm is equal to 1/1000 mm.
  • Move by flagella or pili.
  • Plays an important role in the decomposition process of organic substances

An example of this symbiotic relationship is between the bacteria that live in our intestines and help us to get the nutrients we need and the bacteria that fix nitrogen from the atmosphere so plants can use it.

There are also various kinds of enteric bacteria and mucous membranes that we can encounter in everyday life which you can learn about in Bacteriology book 2 Textbook of Health Analysts.


Bacteria or eubacteria have structures. The structure of this bacterium consists of the outer structure of the cell, the inner structure of the cell, flagella, and pili or fimbriae, here is a more complete explanation:

  • Structure of the outside of the cell. The outer structure of the bacterial cell consists of a cell wall, capsule and plasma membrane.
  • The cytoplasmic membrane consists of a layer of lipoproteins or phospholipids and proteins that are permeable. The cytoplasmic membrane plays a role in regulating the entry and exit of substances in the bacterial cell. The cell wall, has a function to protect and give shape to the bacterial cell. This cell wall is composed of hemicellulose and peptidoglycan compounds. This compound consists of proteins and amino acids.
  • The capsule is the outermost part. This capsule is a layer of mucus. The capsule has a function to protect cells. In addition, it can be used for food reserves.
  • The inner structure of the cell. The internal structure of a bacterial cell consists of DNA, mesosomes, plasmids, ribosomes and endospores. Mesosomes are a part of the cytoplasmic membrane that undergoes folding. Mesosomes play a role in the synthesis of the cell wall and in the division of the nucleus or cell nucleus. DNA is part of the core genetic material. This DNA is a carrier of properties in living things, especially bacteria. Endospore is a spore or structure that has a thick wall. This thick wall is formed when environmental conditions are unfavorable for bacteria. Unfavorable environmental conditions, such as hot, cold, and dry.
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Endospores will return to become bacterial cells when environmental conditions begin to improve. This plasmid is shaped like a ring. Plasmids are found inside the cytoplasm. Plasmids function as a means of cell defense against extreme environmental conditions. Ribosomes are a part of cell organelles that have a major role in the process of protein synthesis in cells. Flagella is a means of movement of bacteria. These flagella have a hair-like shape and are composed of a protein compound called flagellin. The number and location of flagella is one of the basics in the classification of bacteria.

Pili or fimbriae. Pili are shaped like filaments. Pili are only possessed by gram negative bacteria. Pili are smaller, shorter and more numerous than flagella. Pili do not have a function as a means of locomotion. However, pili have a function as a gateway for the entry of genetic material during the conjugation process. After understanding about the structure of bacteria. Where bacteria have four structures with their respective functions. Next will be explained about the classification of bacteria.


Eubacteria Group Based on How to Obtain Food

Based on how to obtain food, eubacteria are divided into:

  • Heterotrophic bacteria (unable to prepare their own food), consisting of (1) Parasites: take nutrients from living organisms. For example Escherichia coli; (2) Saprophytes who take nutrients from dead organisms. For example Mycobacterium tuberculosis.
  • Autotrophic bacteria (can prepare their own food), which consists of (1) photoautotrophs, namely using the energy source of sunlight, for example green bacteria (bacteriochlorophyll) and purple bacteria (bacteriopurpurin); (2) chemoautotrophs, namely using chemical energy sources, for example Nitrobacter, Nitrosomonas, and Nitrosococcus.

Eubacteria Group Based on Oxygen Needs

Based on the need for oxygen, eubacteria are divided into:

  • Aerob bacteria are bacteria that require free O2, for example Nitrosomonas and Mycobacterium tuberculosis.
  • Anaerobic bacteria are bacteria that do not require free O2, for example Clostridium tetani and denitrifying bacteria.

Eubacteria Group Based on Flagella Location

Based on the location of the flagella, eubacteria can be divided into:

  • Atria are bacteria that do not have flagella.
  • Monotric are bacteria that have one flagellum and are attached to one end of the cell.
  • Lofotric are bacteria that have many flagella and are attached to one end of the cell.
  • Amphitrichous are bacteria that have one flagellum and each is attached to both ends of the cell.
  • Peritrichous are bacteria that have flagella scattered all over the surface of the cell.

Classification of Eubacteria Based on Shape

Based on the shape, eubacteria can be divided into:

  • Bacilli (Stems)
    Rod-shaped bacteria can be divided into: monobacilli, diplobacilli, and streptobacilli. Monobacillus (single rod) For example, Escherichia coli and Lactobacillus casei. Diplobacilli (stalks in groups of two) For example, Salmonella typhosa. Streptobacilli (rod chain) For example, Azotobacter and Bacillus anthracis.
  • Cocci (Spheres)
    Ball-shaped bacteria are distinguished into monococci, diplococci, streptococci and staphylococci. Monococcus (single) For example, Micrococcus luteus, Diplococcus (balls in groups of two) For example, Diplococcus pneumoniae (causes pneumonia), Streptococcus (chains form) For example, Streptococcus thermophilus (for making yogurt). Staphylococci (cluster like grapes) For example, Staphylococcus aureus. Sarkina (cube shape) For example, Sarcina lutea.
  • Spirilum
    (Spiral or Like the Letter S) Spiral-shaped bacteria are distinguished into commas and spirokaeta For example, Vibrio cholerae (the cause of cholera). Spirochaeta (spiral and tail) for example: Spirochaeta pallida or Treponema pallidum (the cause of lion king disease or syphilis


Bacteria can reproduce vegetatively (asexually) or generatively (sexually), here’s the explanation, Sinaumed’s!


Bacteria can reproduce asexually by dividing (binary fission) in the right or suitable environment. Bacterial reproduction can take place very quickly. Under optimal conditions, some types of bacteria can divide every 20 minutes. You can calculate the number of reproductive bacteria in 1 hour or 1 day, with the formula 2n (n number of divisions).

Under unfavorable conditions, bacterial cells can defend themselves by forming spores (endospores). Endospore means a spore that forms inside a bacterium. However, there are also types of bacteria that will die due to changes in environmental factors. These environmental factors are constant sunlight, rising temperatures, drought, and the presence of inhibitory and bacteria-killing substances, such as antibiotics and disinfectants.

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Bacteria do not carry out true sexual reproduction, as occurs in eukaryotic living things, because bacteria do not undergo the fusion of sex cells. However, in bacteria there is an exchange of genetic material with partner cells. Therefore, the reproduction of bacteria that occurs in this way is called parasexual reproduction. Bacterial parasexual reproduction can occur in three ways, namely transformation, conjugation, and transduction.

  • Transformation Transformation
    is the transfer of pieces of genetic material or DNA from outside to the recipient bacterial cell. In this process, there is no direct contact between the bacteria giving the DNA and the recipient. Example: Streptococcus pneumoniae, Bacillus, Haemopphilus, Neisseria and Pseudomonas.
  • Conjugation Conjugation
    is the exchange of genetic material by forming a building or bridge or sheath to distribute the genetic material, or the reproduction of bacteria whose sex is unknown.
  • Transduction Transduction
    is the transfer of DNA from the donor cell to the recipient cell by means of a virus. In this case, the viral protein that functions as a shell is used to wrap and carry the donor bacterial DNA to the recipient cell.


As with other organisms, the bacteria itself has a role in human life. Each role of bacteria can be beneficial, but some can be detrimental. Each role of the bacteria will be explained below. These beneficial bacteria are divided into nitrogen-fixing bacteria in plants, nitrifying bacteria, antibiotic-producing bacteria, and bacteria in the food industry. Further explanation of the positive impact of this eubacteria as follows:

  • First, nitrogen-fixing bacteria in plants. Several bacteria have a role in fixing nitrogen from the free air, namely Azetobacter vinelandii, Clostridium pasteurianum, and Rhizobium leguminosarum which carry out symbiosis with leguminous plants.
  • Second, nitrifying bacteria. Nitrosomonas and Nitrosococcus bacteria can carry out the nitrification process by converting ammonia or NH3 to nitrite or NO2. Meanwhile, Nitrobacter bacteria can convert nitrite or NO2 to nitrate or NO3.
  • Third, antibiotic-producing bacteria. These bacteria consist of:
    • Streptomyces griseus bacteria, the types of antibiotics produced are Streptomycin,
    • Streptomyces rimosus bacteria, the type of antibiotic produced is Teracycline,
    • The bacteria Streptomyces venezuelae produces a type of antibiotic, namely Chloramphenicol.
    • Streptomyces aureofaciens bacteria, the type of antibiotic produced is Aureomycin.
    • The type of antibiotic Bacillus polymixa that is produced is Polymyxin.
  • Fourth, bacteria in the food industry. These bacteria consist of :
    • Lactobacillus bulgaricus bacteria, the resulting food product is Yoghurt.
    • Acetobbacter xylinum bacteria, the resulting food product is Nata de coco.
    • Lactobacillus casei bacteria, the resulting food product is Yakult.
    • Streptococcus lactis bacteria, the resulting food product is Butter.
    • Acetobbacter sp. bacteria, the resulting food product is acetic acid.


However, there are also archaebacteria that are detrimental to humans, namely Archaebacteria, which can damage food preserved in salt and cause rapid decomposition of marine fish. In addition, harmful bacteria can also cause disease. You can see this in the book Bacteriology: Microorganisms that Cause Infection below.

Besides having benefits, bacteria also have a negative impact. The bacteria that can harm living things consist of bacteria that cause disease in humans, bacteria that cause disease in livestock, and finally those that can cause disease in plants. For a complete explanation, see below.

  • First, bacteria that can cause disease in humans, which are as follows:
    • Clostridium tetani bacteria which can cause tetanus
    • Salmonella tphosa bacteria that can cause typhoid.
    • Mycobacterium tuberculosis bacteria which can cause TB disease.
    • Diplococcus pneumoniae bacteria which can cause pneumonia.
    • Shigella dysentriae bacteria which can cause dysentery or digestive disease.
  • Second, bacteria that can cause disease in livestock, which are as follows:
    • Bacillus anthracis bacteria which can cause anthrax disease in cattle.
    • Cytophaga columnaris bacteria which can cause disease in fish
    • Streptococcus agalactia bacteria which can cause inflammatory disease of bovine breasts.
    • Actinomyces bovis bacteria which can cause swollen jaw disease in cattle.
  • Third, bacteria that can cause disease in plants, namely as follows:
    • Xanthomonas oryzae bacteria that can cause disease attack rice shoots.
    • Xanthomonas campestris bacteria that can cause disease attack cabbage plants.
    • Pseudomonas solenacearum bacteria which can cause leaf wilt disease in eggplants.
    • Erwinia amylovora bacteria that can cause rotten disease in fruits.
    • Xanthomonas citri bacteria which can cause necrosis disease in citrus plants.

Not all of the bacteria in the world can be harmful to humans or animals. But there are also bacteria that can help human survival. The book Everything About Bacteria and Viruses that is below will explain the various types of bacteria that exist in the environment.

Thus, an explanation of the definition, characteristics, body structure, classification, reproductive system, positive and negative impacts of eubacteria. We hope this article will help you understand eubacteria. Enjoy studying Sinaumed’s!