Bacteria: types, characteristics, where they live, dangers and more (2023)

Bacteria are single-celled microscopic organisms that exist in their millions in all environments, both inside and outside of other organisms.

Some bacteria are harmful, but most serve a useful purpose. They support many life forms, both plant and animal, and are used in industrial and medical processes.

Bacteria are believed to befirst organismsappeared on Earth about 4 billion years ago. The oldest known fossils come from bacteria-like organisms.

Bacteria can use most organic and some inorganic compounds as food, and some can survive in extreme conditions.

The growing interest in the role of the gut microbiome sheds new light on the role bacteria play in human health.

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Bacteria are single-celled organisms that are neither plants nor animals.

They are typically only a few microns long and exist together in communities of millions.

A gram of soil normally contains about 40 million bacterial cells. One milliliter of fresh water normally contains around one million bacterial cells.

It is estimated that the earth contains at least 5 trillion bacteria and it is believed that much of the earth's biomass is made up of bacteria.

There are many different types of bacteria. One way to classify them is by their shape. There are three basic options.

  • Spherical: Spherical bacteria are called cocci, and a single bacterium is a cocci. Examples are the Streptococcus group, responsible for "streptococci.“
  • Rod-shaped: They are known as bacilli (singular Bacillus). Some rod-shaped bacteria are curved. These are called vibrio. Examples of rod-shaped bacteria includeBacillus Anthracis(B. Anthrax), ÖMilzbrand.
  • Spirals: They are known as spirillae (singular spirillus). When their whorl is very tight, they are called spirochetes.Leptospirosis,Lyme-Borreliose, jSyphilisthey are caused in this way by bacteria.

Within each shape group there are many variations.

Bacterial cells differ from plant and animal cells. Bacteria are prokaryotes, which means they have itkernlos.

A bacterial cell includes:

  • Capsule: A layer found on the outside of the cell wall of some bacteria.
  • Cell Wall: A layer made of a polymer called peptidoglycan. The cell wall gives the bacterium its shape. It is outside of the plasma membrane. The cell wall is thicker in some bacteria called gram-positive bacteria.
  • Plasma membrane: Located within the cell wall, it generates energy and transports chemicals. The membrane is permeable, which means substances can pass through it.
  • Cytoplasm: jelly-like substance within the plasma membrane that contains genetic material and ribosomes.
  • DNA: Contains all of the genetic instructions used in the development and function of the bacterium. It is located in the cytoplasm.
  • Ribosomes: This is where proteins are made or synthesized. Ribosomes are complex particles composed of RNA-rich granules.
  • Flagellum: This is used for movement to power some types of bacteria. There are some bacteria that can have more than one.
  • Pili: These hair-like appendages on the outside of the cell allow it to attach to surfaces and transfer genetic material to other cells. This can contribute to the spread of disease in humans.
(Video) Bacterial Structure and Functions

Bacteria feed in different ways.

Heterotrophic bacteria or heterotrophs obtain their energy by consuming organic carbon. Most absorb dead organic matter, such as B. rotting meat. Some of these parasitic bacteria kill their host while others help them.

Autotrophic (or simply autotrophic) bacteria make their own food, either by:

  • Photosynthesis using sunlight, water and carbon dioxide or
  • Chemosynthesis using carbon dioxide, water and chemicals like ammonia, nitrogen, sulfur and others

Bacteria that carry out photosynthesis are called photoautotrophs. Some species, such as cyanobacteria, produce oxygen. These probably played a crucial role in the formation of oxygen in the Earth's atmosphere. Others, like heliobacteria, do not produce oxygen.

Those that use chemosynthesis are called chemoautotrophs. These bacteria are commonly found in sea vents and on the roots of legumes such as alfalfa, clover, peas, beans, lentils and peanuts.

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Bacteria can be found in soil, water, plants, animals, radioactive waste, deep in the earth's crust, ice and arctic glaciers and hot springs. There are bacteria in the stratosphere, between 6 and 30 miles in the atmosphere, and in the deep ocean, down to 32,800 feet or 10,000 meters.

Aerobic or aerobic bacteria can only grow where oxygen is present. Some species can cause problems to the human environment, such as B. Corrosion, deposits, water clarity problems and odours.

Anaerobes or anaerobic bacteria can only grow where there is no oxygen. In humans, this occurs primarily in the gastrointestinal tract. They can also cause gasGangrän,Tetanus,botulismand most dental infections.

(Video) Taxonomy of Bacteria: Identification and Classification

Facultative anaerobes, or facultatively anaerobic bacteria, can live with or without oxygen, but prefer environments where oxygen is present. They are mainly found in soil, water, vegetation and the normal flora of humans and animals. include examplessalmonella.

Mesophilic or mesophilic bacteria are the bacteria responsible for most human infections. They thrive in moderate temperatures around 37°C. This is the human body temperature.

include examplesListeria monocytogenes,Pesudomonas maltophilia,Thiobacillus novellus,Staphylococcus aureus,Streptococcus pirogenes,Steotococcus-Pneumonia,Escherichia coli, jClostridium kluyveri.

The human gut flora, or gut microbiome, contains beneficial mesophilic bacteria such asLactobacillus acidophilus.

Extremophilic or extremophilic bacteria can withstand conditions considered too extreme for most life forms.

Thermophiles can survive at high temperatures of up to 75-80°C and hyperthermophiles can survive at temperatures of up to 113°C.

Deep in the ocean, bacteria live in total darkness next to hot springs where both temperature and pressure are high. They make their own food by oxidizing sulfur that comes from deep within the earth.

Other extremophiles are:

  • Halophiles only found in saline environment
  • Acidophiles, some of which live in environments as acidic as pH 0
  • Alkaliphiles, living in alkaline environments down to pH 10.5
  • Psychrophiles, which occur in cold temperatures, for example in glaciers

Extremophiles can survive where no other organism can survive.

Bacteria can multiply and change using the following methods:

  • Binary Fission: An asexual form of reproduction in which one cell continues to grow until a new cell wall grows through the center, forming two cells. These separate and form two cells with the same genetic material.
  • Transfer of Genetic Material: Cells acquire new genetic material through processes known as conjugation, transformation, or transduction. These processes can make bacteria stronger and better able to resist threats such asAntibioticMedicine.
  • Spores: When some types of bacteria are short of resources, they can form spores. The spores contain the DNA material of the organism and contain the enzymes necessary for germination. They are very resistant to environmental stress. The spores can remain dormant for centuries until the right conditions are met. They can then reactivate and become bacteria.
  • Spores can survive through ambient periodsemphasize, including ultraviolet (UV) and gamma radiation, dehydration, starvation, chemical stress, and extreme temperatures.

Some bacteria produce endospores, or internal spores, while others produce exospores, which are shed to the outside. These are known ascysts.

Clostridiumis an example of an endospore-forming bacterium. There are about 100 types ofClostridium, includedClostridium botulinim(C. botulinum) or botulism, responsible for a potentially fatal type ofpoisoned food, jClostridium difficile(It is difficult) that causes colitis and other intestinal problems.

Bacteria are often seen as bad, but many are helpful. Without them we wouldn't exist. The oxygen we breathe is probably created by the activity of bacteria.

(Video) Bacteria (Updated)

human survival

Many of the bacteria in the body play an important role in human survival. Bacteria in the digestive system break down nutrients, such as complex sugars, into forms that the body can use.

Harmless bacteria also help prevent disease by occupying places where disease-causing or pathogenic bacteria want to attach themselves. Some bacteria protect us from disease by attacking pathogens.

fixation of nitrogen

The bacteria take up nitrogen and release it for use by plants when they die. Plants need nitrogen in the soil to live, but they cannot do it on their own. To ensure this, many plant seeds have a small bacterial container that is used when the plant sprout.

food technology

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Lactic acid bacteria such aslactobacillijThe Lacto CookAlong with yeast and mold, they are used to prepare foods such as cheese, soy sauce, natto (fermented soybeans), vinegar, yogurt, and pickles.

Not only is fermentation useful for preserving foods, some of those foods may also provide health benefits.

For example, some fermented foods contain types of bacteria similar to those associated with gastrointestinal health. Some fermentation processes result in new compounds, such as lactic acid, which appear to have anti-inflammatory effects.

This requires further researchconfirm health benefitsof fermented foods.

Bacteria in industry and research

Bacteria can break down organic compounds. This is useful for activities like waste processing and cleaning up oil spills and toxic waste.

The pharmaceutical and chemical industries use bacteria to manufacture certain chemicals.

Bacteria are used in molecular biology, biochemistry, and genetic research because they can grow quickly and are relatively easy to manipulate. Scientists use bacteria to study how genes and enzymes work.

Bacteria are necessary to produce antibiotics.

thuringiensis-Bazillus(Bt) is a bacterium that can be used in agriculture instead of pesticides. It does not have the undesirable environmental consequences associated with the use of pesticides.

Some types of bacteria can cause diseases in humans, such asZorn, diphtheria,Ruhr, bubonic plague,lung infection,Tuberculosis(TUBERCULOSIS),typhus, and many more.

When the human body is exposed to bacteria that the body does not recognize as helpful, the immune system attacks them. This reaction can lead to the symptoms of swelling as wellinflammationwhich we see, for example, in an infected wound.

In 1900 pneumonia, tuberculosis andDiarrheaThey were the top three killers in the United States. Sterilization techniques and antibiotics have led to a significant reduction in deaths from bacterial diseases.

However, overuse of antibiotics makes the bacterial infection more difficult to treat. When bacteria mutate, they become more resistant to existing antibiotics, making infections more difficult to treat. Bacteria mutate naturally, but overuse of antibiotics speeds up the process.

Even as new drugs are developed, without behavioral change, antibiotic resistance will continue to be a major threat."

World Health Organization (WHO)

For this reason, scientists and public health officials are urging doctors to only prescribe antibiotics when necessary and urging people to practice other forms of disease prevention, such as good food hygiene, hand washing, vaccination and using condoms.


Recent research has led to a new and growing awareness of how the human body interacts with bacteria, specifically the communities of bacteria that live in the gut, known as the gut microbiome or gut flora.

In 2009 researchers publishedrecommendationssuggesting that women withobesityrather had a certain type of bacteria,Selenomonas noxia(is harmful),in his mouth.

In2015, scientists from the University of North Carolina discovered that the intestines of people withAnorexiacontain “very different” bacteria or microbial communities compared to people without the condition. They suspect that this could have psychological effects.

More than 2,000 years ago, a Roman author, Marcus Terentius Varro, suggested that diseases could be caused by small animals hovering in the air. He advised people to avoid swampy places during construction as they could contain insects too small for the eye to see and enter the body through the mouth and nose and cause disease.

In the 17th century, a Dutch scientist, Antonie van Leeuwenhoek, created a single-lens microscope that allowed him to see what he called little animals, later known as bacteria. He is considered the first microbiologist.

In the 19th century, chemists Louis Pasteur and Robert Koch said that diseases are caused by germs. This became known as the germ theory.

(Video) Bacteria | Structure and Function

In 1910, scientist Paul Ehrlich announced the development of thefirst antibiotic, Salvarsan. He used it to cure syphilis. He was also the first scientist to detect bacteria using dyes.

In 2001, Joshua Lederburg coined the term “gut microbiome,” and scientists around the world currently aretries to describeand to better understand the structures, types and uses of the "gut flora" or bacteria in the human body.

Hopefully over time this will workshed new lighta wide range of health problems.


What are the 4 types of bacteria? ›

Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes).

What are 5 characteristics of bacteria? ›

Five characteristics of bacteria include being unicellular, prokaryotic, microscopic, lacking a nucleus, and having a plasma membrane. These traits are shared by all bacteria.

What are the living characteristics of bacteria? ›

Bacteria, on the other hand, are living organisms that consist of single cell that can generate energy, make its own food, move, and reproduce (typically by binary fission).

What are some harmful bacteria? ›

The bacteria and viruses that cause the most illnesses, hospitalizations, or deaths in the United States are described below and include:
  • Campylobacter.
  • Clostridium perfringens.
  • E. coli.
  • Listeria.
  • Norovirus.
  • Salmonella.
Mar 22, 2021

What are 5 harmful effects of bacteria? ›

They are responsible for many infectious diseases like pneumonia, tuberculosis, diphtheria, syphilis, and tooth decay. Some bacteria cause cellulose degradation thereby destroying textiles, wooden articles, and canvas.

What are the 7 characteristics of bacteria? ›

Characteristics Of Bacteria
  • Capsule.
  • Cell wall.
  • Flagellum.
  • Pili.
  • Cytoplasm.
  • Ribosomes.
  • Chromosomes.

Are all bacteria harmful? ›

Bacteria can be harmful, but some species of bacteria are needed to keep us healthy. The bacteria on our skin, in our airways, and in our digestive system are the first line of defense against foreign “invaders” (pathogens) that can cause infection and other problems.

What 4 characteristics are used to identify bacteria? ›

Identifying Bacteria Through Look, Growth, Stain and Strain.

What are 7 characteristics of living? ›

The seven characteristics what makes an organism living are: Environmental responses, cells, change and growth, reproduction, having complex chemistry, and homeostasis and energy processing.

What are the 4 common characteristics used to describe bacterial colonies? ›

Observing colony morphology is an important skill used in the microbiology laboratory to identify microorganisms. Colonies need to be well isolated from other colonies to observe the characteristic shape, size, color, surface appearance, and texture.

What are 4 common bacterial infections? ›

Common bacterial diseases include UTIs, food poisoning, STIs and some skin, sinus and ear infections. They're often treated with antibiotics.

What are the 4 functional groups of bacteria? ›

The cell walls of bacteria consist of several polymers and macromolecules, which possess carboxyl, hydroxyl, phosphate, and amide functional groups.

What are the 3 main bacteria? ›

The three basic shapes of bacteria are bacillus (rod-shaped), coccus (spherical-shaped), and spirillum (spiral-shaped).


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