Spirilla Bacteria – Definition, Examples, Shape, Diseases

What is spirilla bacteria? How does it affect our health? And how do you identify and locate this particular type of bacteria?

Spirilla Bacteria - Definition, Examples, Shape, Diseases

Whether you are a keen biologist, trying to learn more about health, or are just curious about the tiny systems and organisms that make up our world, read on for all you need to know about Spirilla bacteria, including what it is , what it does, and what it looks like.

What Are Bacteria?

In order to understand spirilla bacteria more specifically, it is important for us to have a more general understanding of bacteria, including what they are, what their structure looks like, and why they are significant.

In the simplest terms, bacteria are single-celled organisms that feed off of organic matter.

They are usually classified into three groups based on their shape: rod-shaped, spiral-shaped, and cocci-shaped.

  • Rod Shaped Bacteria

These bacteria are commonly found in soil and water. They are typically straight, cylindrical cells.

Rods are often used to describe bacteria that are approximately 0.5 micrometers wide.

  • Spiral Shaped Bacteria

Spiral-shaped bacteria are most common in the human body. They have a helical structure that resembles a corkscrew. These bacteria are typically 1.0 micrometers wide.

Spirals are often used to describe bacterial cells that are approximately 3.0 micrometers long.

  • Coccus Shaped Bacteria

Coccuses are spherical bacteria that range from 0.2 to 0.4 micrometers in diameter. They are typically found in liquid environments such as urine and blood.

Why Do We Need To Know About Different Types Of Bacteria?

Understanding bacteria in a more generalized way can offer a number of advantages, and these include:

  • Understanding Causes of Infection

Knowing what type of bacteria we are dealing with helps us identify the cause of an infection.

Most infections caused by bacteria are contagious, and this means that if you get infected, you can pass the disease along to others.

While for less serious and severe diseases this can be a mere inconvenience, more serious infections can be life-threatening, and so being able to identify the bacteria responsible for the illness as soon as possible is essential.

Some bacteria are harmful to humans. For example, some strains of E. coli are responsible for food poisoning.

Others may cause pneumonia, meningitis, urinary tract infections, and more, and many of these can be life-threatening.

Knowing which type of bacteria is causing your infection allows doctors to prescribe the proper treatment as quickly as possible.

What Is A Bacterial Infection?

A bacterial infection occurs when bacteria enter the body through a break in the skin.

Once inside the body, these bacteria multiply rapidly and start producing toxins. Examples of illnesses that can be caused by bacteria include:

  • Pneumonia
  • Meningitis
  • Staphylococcal Food Poisoning

There are a number of types of bacterial infections, and these include: 

  • Bacterial Skin Infections

Most bacterial skin infections are caused by gram-positive strains of bacteria known as Staphylococcus and Streptococcus, and these can cause issues such as cellulitis causes, folliculitis, impetigo causes, and boils.

  • Foodborne Bacterial Infections

Bacterial food poisoning is caused by the ingestion of contaminated foods. Common culprits include Salmonella, Listeria, Campylobacter, and E. coli.

  • Sexually Transmitted Bacterial Infections

Many sexually transmitted bacterial infections are caused by Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, and Trichomonas vaginalis.

  • Other Bacterial Infections

Infectious diseases caused by other bacteria include Lyme disease, tuberculosis, syphilis, cholera, typhoid fever, anthrax, scarlet fever, and diphtheria.

How Are Bacteria Identified?

The first step in identifying bacteria is to culture them. In this process, a sample of the suspected bacteria is placed onto a nutrient agar plate.

After incubation at 37° C (98.6° F), the colonies will grow within 24 hours.

Colonies that look similar are then identified using a microscope, and this allows them to be analyzed and studied.

Structure Of Bacteria

Bacteria have a single cell membrane that surrounds them. This membrane contains proteins embedded in its structure and allows the cells to move around and divide.

Inside the cell, there is a cytoplasm containing the food source for the bacterium. There are many different types of bacteria. Each type has its own special characteristics.

For example, Gram-positive bacteria contain an outer layer consisting of peptidoglycan, while Gram-negative bacteria do not have this outer covering.

  • Gram-Positive Bacteria

Gram-positive bacteria are characterized by having thick walls and a large number of ribosomes inside each cell.

Ribosomes are structures within the cell that help synthesize proteins. They also provide protection against toxins released by the bacteria.

  • Gram-Negative Bacteria

Gram-negative bacteria are characterized by having a thinner wall than gram-positive bacteria. Their outer membrane does not contain any ribosomes.

Instead, they have a unique structure called the outer membrane complex (OMC).

The OMC is made up of porin channels that allow small molecules to pass through the bacterial membrane.

These channels are very important because they allow the bacteria to take in nutrients and expel waste products.

Gram-negative bacteria are also known as “true” bacteria because their cell walls contain only one component, LPS.

In contrast, gram-positive bacteria have multiple layers of cell wall components including teichoic acid, peptidoglycan, and lipoteichoic acid.

What Is Spirilla Bacteria?

What Is Spirilla Bacteria?

Spirilla bacteria are corkscrew-shaped, Gram-negative bacteria that live primarily in water and aquatic environments – as a result, they are good swimmers.

They are also found in human intestines, and are most often characterized by flagella – these are small, motile structures.

Some species of spirilla bacteria cause disease in humans and animals.

The genus of Spirilla has long been divided into three main genera, and these are: 


Spirillum are the smallest of the three groups, with only one known species, S.lutetiensis.

This bacterium lives in soil and freshwater environments – it can be found in lakes, rivers, ponds, and other bodies of fresh water.

It is not considered pathogenic, but its presence may indicate contamination from sewage or industrial waste. All members of this group are gram-negative.

The term “spirillum” is most commonly used to describe the wider group.

Currently, only three species are included in the genus Spirillum. These include Spirillum volutans, Spirillum winogradskyi, and Spirillum minus.

They are also mostly microaerophilic and thus require a low concentration of oxygen to survive.

However, based on cultural techniques, studies have shown they can be grown aerobically in some liquid media (media with specific supplements).

Spirillum Shape

Compared to the other Spirilla species, members of the genus Spirochaeta are relatively larger, ranging from between 1.4 and 1.7um in size.

Some members can grow up to 60 microns long.

Spirillum bacteria also exhibit a spiral shape with one to about five complete helical turns, though there have also been instances that have seen these bacteria come with an incomplete helical turn.

These bacteria are able to move thanks to crescent-shaped flagella.

The structure of Spirilla bacteria is similar to that of other gram-negative bacteria.

It has a thin outer membrane, a periplasmic space between the inner and outer membranes, and an inner membrane.

The outer membrane consists of lipopolysaccharide molecules, phospholipids, and proteins.

Lipopolysaccharide is composed of long chains of sugars, while phospholipids consist of fatty acids attached to phosphate groups. Proteins are made up of amino acids.

The periplasmic space is filled with water and enzymes. Enzymes are needed to break down nutrients into smaller units so that the bacteria can use them.

The inner membrane is where the energy needed to live is produced. The inner membrane contains electron transport complexes that allow electrons to flow across it.

Electrons are then transferred to oxygen to produce energy.

Cell Wall

Similar to other types of bacteria, Spirillum bacteria also have a cell wall covering their cell bodies.

Cell walls, along with their components, play an important role in the structure and rigidity of these cells.

The earliest sections of the cell wall were identified in the 1960s by fixing cells and then staining them.

Researchers noticed a thin but dense membrane covering the surface of the cell’s cytoplasm and that this was made up of three layers of lipopolysaccharide as well as a mucopeptide layer that is clearer during cell division – this may contribute to the shape of the cell.


As the moniker suggests, Ocenospirillum are most frequently sourced in marine environments, and some examples of Oceanospirillum bacteria include; O. japonicum. O. Linum, O. minutulum, and 0. beijerinckii.

Like the other Spirillum species, the members of the family vary in size from between 0.4 µm and 1.4 µm wide, and between 1µm to 75 µm long.

As the name indicates, Oceanospirillum bacteria are commonly sourced in water-based environments.

These organisms areaerobic chemoheterotrophs and therefore possess a respiratory metabolic type – this means that there is no fermentation of carbohydrates as part of their respiratory process.

Their marine-based nature means that oceanospirillum rely heavily on seawater, and they need this in order to grow and thrive; if placed in freshwater, for example, they will be unable to survive.

Shape Of Oceanospirillum

As with other members of the Spirilla bacteria family, most of the members of this group are spiral in shape, though a few may vary from a helix shape with several complete turns, down to a fibroid shape, with just a single complete turn.

Some may also be rod-like in shape – this is particularly commonly associated with prolonged culture.

As an example, a prolonged culture of O. japonicum saw a change in the general structure and form of the cell, changing from having complete turns, to becoming slightly S-shaped.

Oceanospirillum species also include a plasma membrane, as well as a polar membrane – this is located in the flagella, and connects to the inner section of the plasma membrane, connected by links that are bar-like in shape.

The species also uses a polymer consisting of intracellular poly-b hydroxybutyrate (PHB) as an energy store.

Coccoid Bodies

Oceanospirillum have also been proven to create coccoid bodies with thin walls, and these usually form in older cultures that are referred to as “microcysts”.

When added to a body of distilled water, these bodies are usually able to resist lyses and are usually formed by the entwinement of two cells, which fuse together.

As they fuse, the cells grow shorter and thicker, resulting in a coccoid body.

These can then germinate if they are added to fresh media, and this process is typically characterized by either bipolar or unipolar growth, which forms a helical cell with one or several complete turns.

Once in the correct media, you should expect to see new colonies within two or three days, and these can be whitish in color, with a diameter of around 1.5mm.

Over the next few days, the color may change to a yellow-green or pale yellow color.


Another species found within the wider spirillum family is the Aqua spirillum, and some of the main examples of species that belong to this group include A. fasciculus, A. Bengal., A. peregrinum, A. polymorphum, A. Serpens, A. itersonii, A. dispar, and A. magnetotacticum.

Aquaspirillum are found largely in freshwater, as opposed to salt, and tend to be sourced in canal water and ditches, stagnant bodies of water such as sewage, in addition to ponds and streams.

Their nature means that they cannot grow in salty or saline conditions, and will require cultures with under 3% sodium chloride to survive.

They do, however, share a respiratory metabolism, as they are also aerobic organisms, and do not ferment carbohydrates.

They tend to be between 0.2 and 1.4mm in diameter and are helical or helically curved and rigid in shape and structure.

Most members of the group are aerobic organisms that use oxygen for respiration, but some species have demonstrated the ability to grow anaerobically using nitrates.

Nitrogen-fixing bacteria use nitrogenase to convert atmospheric nitrogen into ammonia, which is then converted into nitrates by the bacteria, but this only takes place under micro-aerobic conditions.

Shape Of Aquaspirillum

Like the Oceanospirillum genus, Aquaspirillum species are helical in shape, with a have a spiral or helical shape.

In addition, some researchers have identified several species that either has a vibrioid or curved shape, while fasciculus are comparable to straight rods in shape.

The type of fla­gellum also varies between different species.

Unlike Oceanospirillum, most Aquaspirillum don’t form coccoid bodies when they’re growing in old cultures.

Most species have a spiral shape, but repeated culture and serial transfers have been shown to cause some to gradually develop a straight rod shape.

With regards to cell structures, some of the other features of Aquaspirillum include:

  • A polar membrane, this is typically attached to the cytoplasmic membrane that is located at the polar ends of cells.
  • Intracellular poly -β-hydroxybutyrate – there are just two species that lack this
  • Have a cell wall with a variety of protein macromolecules
  • Produce a yellowish-green pigment when they are cultured on PSS agar
  • Have a counterclockwise helix
  • Are chemoorganotrophs – this means that they obtain energy from organic compounds 

What Are Gram-Negative Bacteria?

What Are Gram-Negative Bacteria?

Gram-negative bacteria do not have a thick peptidoglycan layer on their outer membrane. Instead, they have a thin layer of phospholipids.

This allows certain types of antibiotics to pass through the outer membrane easily.

Is Spirilla Bacteria Gram-Negative?

Spirilla bacteria is gram-negative, and this means that the cell wall is more chemically complex than gram-positive bacteria.

This makes it harder for antibiotics to penetrate the cell wall and reach the cytoplasm.

In addition, gram-negative bacteria produce lipopolysaccharide which helps them resist attack by white blood cells.

Gram-Positive Vs Gram-Negative Bacteria

A Gram-positive bacterium has a thicker peptidoglycan layer around its outside.

This makes it less likely for antibiotics to pass through the cell wall. Gram-positive bacteria tend to be found in skin infections and food poisoning.

Why Do We Need Gram Staining?

Gram staining is very important because it allows types of bacteria to be identified and studied – this can play a key role in helping to ensure that patients and illnesses are diagnosed and treated most effectively and efficiently.

How Does Gram Staining Work?

You can test for gram-negative bacteria using the Gram stain method, which has been used for a number of years to help identify and locate types of bacteria, as well as their Gram status.

Performing Gram staining requires you to follow specific steps to ensure accuracy, and these are:

  • First, you must prepare a slide by spreading a small amount of bacteria onto a glass slide.
  • Next, you must spread another slide over the top of the bacteria.
  • Finally, you must cover both slides with a coverslip.
  • After placing the coverslip, you should examine the slide under a microscope. If you see any purple coloration, you will know that there are gram-positive bacteria present. On the other hand, if you see pink or red, you will know that gram-negative bacteria are present.

Types Of Gram Stain

There are two main types of Gram stains: the Romanowsky stain and the Giménez stain. Both stains work similarly but differ slightly in how they are performed.

Romanowsky Stain

The Romanowsky stain uses methylene blue dye to highlight the presence of bacteria. It is also known as methenamine silver or azure A.

The Romanowsky stain requires a longer incubation time (about 30 minutes) compared to the Gimenez stain (10 minutes), and so may not be suitable for situations that require fast results.

The Romanowsky stain was first developed in 1884 by Dr. Karl von Frisch. He named his stain after the city of Vienna where he lived at the time.

Gimenez Stain

The Gimenez stain is one of the oldest stains available. It was originally designed in 1891 by Dr. Eduard Giménez.

The Gimenez stain uses crystal violet dye to highlight the presence of bacteria. It is also called crystal violet or CV.

The Gimenez stain does not require a long incubation period like the Romanowsky stain, and this can be ideal for situations that require fast, accurate results.

It does, however, take about 10 minutes to perform, though the faster results often make up for this.

Spirillum Diseases

One of the most common diseases that can be caused by Spirilla bacteria is rat-bite fever, also known as epidemic arthritic erythema or spirillary fever.

As with other Spirilla bacteria, the Spirillum minus that can cause rat-bite fever has a spiral shape, but this tends to be shorter and thicker than other species, with a total of almost six complete helical turns.

What Is A Rat Bite Fever?

 Rat-bite fever is a bacterial disease that affects humans who have contact with rats. The bacteria responsible for this disease are called spirochetes.

They are small, rod-shaped bacteria that live in the digestive tract of rats. When people touch a rat’s mouth, nose, or eyes, they become infected with these bacteria.

People usually get sick within two weeks after being exposed to a rat. Symptoms of rat-bite fever include:

  • Fever
  • Headache
  • Muscle aches
  • Swollen lymph glands
  • Rash
  • Joint pain
  • Fatigue
  • Nausea
  • Vomiting
  • Diarrhea

If left untreated, rat-bite fever can be very serious and, in some cases, fatal.

Rats are the only known host for Spirillum minus (also called S. minus).

Because they act as carriers for the bacteria but don’t show any symptoms, they’re considered asymptomatic carriers.

Infections in other animals, such as mice, guinea pigs, and rabbits, have been linked to various diseases.

Studies have shown that rats become infected when they are injected with infected blood or when they eat infected tissue.

These animals (rodents in particu­lar) carry bacteria in their blood, the conjunctivae, or nasal passages.

Normally, transmission from rats to humans occurs when humans are clawed or bitten by a rat, though cases have also been transmitted through other rodents.

During the first two to three weeks following exposure, the affected individual may suffer from fever and chills, weight loss, headaches, hair loss, and signs of infection at the wound site, including inflammation and pain.

If the patient remains untreated, further symptoms may develop and these can include rashes, fever, pneumonia myocarditis, and, in some cases meningitis.

Can Rat Bite Fever Be Treated?

The treatment of rat-bite fever depends upon fast action, and you should make sure that the patient is treated with penicillin as quickly as possible.

Penicillin and ampicillin are the most commonly used drugs for treating rat-bite fever.

Other antibiotics that can treat this condition include cephalosporins, tetracyclines, quinolones, and sulfonamides.

Final Thoughts

Spirilla is an important bacteria and one that has the potential to cause a great deal of damage to humans.

Rat-bite fever is a condition that can be extremely serious if left untreated, and so it is crucial that you are able to recognize the signs and symptoms as soon as possible, and that the correct treatment – usually penicillin – is administered as soon as possible.

By understanding the basics of spirilla, and bacteria, in particular, you will have the knowledge and information you need.

Jennifer Dawkins