Colouring Clothing with Bacteria

Do you love to wear clothing that is bright and colourful? Or are dark or muted colours more your style? People can make clothing in just about any colour they can imagine. Have you ever wondered where those colours come from?

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Shown is a colour photograph filled with dozens of colourful scarves. The scarves are arranged in three rows, as if they are hanging on racks. The scarves on the top row have brightly coloured patterns of stars, diamonds, stripes etc. The middle has solid colours, some with ruffled edges, and some with fringes. The bottom row has flower patterns in many different sizes and styles.

What gives clothing its colour?

Most clothing today is coloured using synthetic dyes. A dye is something that colours materials like paper, plastic, leather and fabric. Dyes react chemically with the materials they are applied to. This keeps the colour from being washed away.

In the past, people dyed yarn, fabric and clothing using what they had on hand. This included plants, animals and minerals. People used many parts of plants, including roots, berries, leaves, bark and wood to make dyes. Dyes made from natural materials are often called natural dyes.

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Shown is a colour photograph of ten containers of plant parts with dyed yarn hanging behind. The bowls and baskets are spread out on a cement floor. One contains orange flowers, another looks like leaves, and a third is bark. There are also twigs, sticks and grass. In the foreground are two small logs, one of which has a bright red streak down its centre. Besides the plants, there are two stone slabs with stone rolling pins on top. One is stained bright red, and the other deep blue. There are also two clay vases that look wet inside. On each side of the photograph are rugs, in bright red, and a blue and white pattern. In the background, skeins of yarn, dyed in different colours, hang along a plaster wall.

Making natural dyes is very time consuming. Sometimes, it can also be expensive. It can also require a lot of water and land.

Synthetic Dyes

In the mid-1800s, an 18-year old English chemist named William Henry Perkin was experimenting with coal tar in hopes of finding a cure for malaria. Coal tar is a thick, sticky liquid that is left over when coal is heated. He did not find a cure for malaria, but he did create an oily liquid that stained cloth purple. Scientists think this was the world’s first synthetic dye. A synthetic dye is a dye that is produced chemically.

Did you know?

The colour of Perkin’s dye was known as mauve in England, after the French name for the mallow flower. Chemists later called it mauveine.

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Shown is a square filled with solid, deep purple.

Perkin’s dye proved to be very popular. Soon chemists began experimenting to find new colours. By the 1860s, synthetic dyes were big business and a whole rainbow of colours were available.

Today, almost all dyes used to colour clothing are synthetic. Synthetic dyes are used because:

• They can produce bright colours
• They do not fade easily in light
• They are inexpensive to make
• They will not wash out
• They can colour synthetic fabrics like polyester and nylon, unlike natural dyes 

Did you know?

It is estimated that up to 200 000 tons of synthetic dyes are produced for the textile industry each year. 

Problems with Synthetic Dyes 

As popular as they are, synthetic dyes pose some serious health risks for people and the environment. Runoff from textile dyeing factories can pollute water systems and harm ecosystems.

Synthetic dyes can also impact human health. Dyes, such as azo dyes, are very toxic and can damage cells. This damage can lead to problems with people’s immune systems. It can even lead to cancer. Some dyes also contain heavy metals. These can lead to learning disorders and kidney disease.

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Shown is a colour photograph of two people with their hands in a vat of blue liquid. Dye fills the lower half of the photograph. It is a dark blue liquid with clumps of deep blue froth across the surface. Two people are standing behind the edge of the vat with their hands in the dye. Their long black hair is tied back. They both wear aprons and long green rubber gloves. The person on the right is pulling wet, shiny blue material out of the vat. The background looks like a factory or warehouse. It is a large, bright space painted white.

Because of these concerns, natural dyes are making a comeback. But they haven’t just been using the old tried and true plants and animals. A new and unusual source of dyes is bacteria. 

Why Bacteria?

Most living things have cells that can produce pigments. For example, humans produce melanin. This is what gives our skin, eyes and hair their colours. Pigments don’t just give us colour, they can also give us protection. The melanin in our skin and eyes helps protect us from damaging UV radiation.

Did you know?

Eumelanin is the pigment associated with darker colours, like brown and black, in our skin and hair. Pheomelanin is associated with other colours, like red, pink and yellow.

Like people, bacteria produce pigments to help them survive. The pigments bacteria produce help them live in environments with extreme temperatures, pH and radiation levels. Pigments also help some bacteria undergo photosynthesis.

Did you know?

Cyanobacteria and purple and green sulphur bacteria are two types of bacteria that undergo photosynthesis. Their pigments absorb energy from sunlight, which they convert into a form of energy they can use.

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Shown is a colour photograph of layers of teal, blue and green. Thick stripes of colour follow the shape of a gravel shoreline at the bottom of the photograph. The first stripe is bright teal. The second is bright blue. The third is bright green. The rest of the water appears to be coated in slightly darker green sludge.

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Shown is a colour photograph filled with speckled shades of pink, purple and green. The texture of the material looks like algae or moss. It is mottled in dark purple, brown, gold, green, pink and purple. Thin streaks of white powder sit on top of the main image, like marks on glass.

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Shown is a colour photograph of bright yellow and green pigments in water. In the centre of the photograph is a deep, narrow, underwater hole. The sides of the hole bright green with a texture like thick clouds. Around the top of the hole is a thick ring of deep yellow that darkens to gold at the edges. This gold seeps into narrow rivulets on the surface around. This is white, with ice or algae. Low hills, evergreen trees, and a strip of blue sky can be seen in the background.

Here are some examples of bacteria and the pigments they produce. The columns on the right describe their habitats and the roles the pigments play.

Did you know?

Scientists have even used some bacteria to break down synthetic dyes in the environment.

How can bacteria be used to dye clothes? 

A number of pigments produced by bacteria can be used as dyes. When scientists first began using bacterial dyes, they grew bacteria right on the fabric.

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Shown is a colour infographic illustrating the five steps of bacteria dyeing.

The title, “How it Works: Bacteria Dyeing” is in block letters across the top. Below, on a black background, each step is in gold block letters. More details are in smaller white letters below. Each step has a white circle with a small illustration.

“Grow Bacteria: Grow the strain of bacteria that makes the specific pigment.” This is accompanied by an illustration of an Erlenmeyer flask filled with pink liquid.
“Sterilize Fabric: Put the fabric in a hot oven to kill any microorganisms that might be living on it.” This is accompanied by an illustration of what looks like a microwave, that looks pink inside.
“Add Bacteria: Add bacteria and their food to the sterile fabric.” This is accompanied by an illustration of a petri dish with pink circles growing in it.
“Grow more bacteria on fabric: Put the bacteria in a warm place where they can quickly reproduce and make lots of pigment.” This is accompanied by an illustration of a microwave that looks purple inside. 
“Sterilize Fabric: Put the fabric in a hot oven to kill the bacteria.” This is accompanied by a microwave that looks pink inside.

Below, another paragraph reads, “The pigment gets left behind, colouring the fabric.” This is accompanied by an illustration of a white rectangle marked with pink ovals.

Samples of fabric after bacterial dyeing (Source: Laura Luchtman & Ilfa Siebenhaar, Living Colour. Used with permission).

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Shown is a colour photograph of four petri dishes, each with a dyed sample of fabric. The dishes in the foreground are labelled A and B and the dishes in the background are labelled C and D. Each of the pieces of fabric has irregular patches of lighter and darker blue tones.

With this “live dyeing” method, each batch of fabric is unique. Their patterns reflect how the bacterial colonies grow. The advantage of live dyeing is that the fabric does not need any harmful chemicals or pre-treating. It also uses very little water and energy.

But so far, this method has only been used in laboratories. This is because some of the bacteria can be harmful to people. Live dyeing also needs to be done in a way that does not accidentally introduce other types of microorganisms onto the fabric. It would be challenging to use this method on a large scale.

The Future of Bacterial Dyeing

A number of companies are getting involved in genetically engineering bacteria to produce pigments. For example, Ginkgo Bioworks is engineering strains of bacteria to produce the pigment violacein.

Colorifix is now growing and using bacteria on a larger scale. Here is how they do it.

1. Find a colour in nature that they want to create as a pigment.
2. Identify the DNA code producing that specific colour.
3. Engineer the microbes to produce the pigment they would in nature.
4. Ship about 5 ml of the bacteria to a dyehouse or mill.
5. Grow the bacteria at the dyehouse or mill using a fermentor. A fermentor is a big tank where the bacteria can grow and divide very quickly. The bacterial cells produce the pigment. It only takes 18 to 24 hours to make a large quantity of the pigment mixture.
6. Dye the fabric using the pigment mixture in a standard dyeing machine.

Image - Text Version

Shown is a colour photograph of petri dishes and an Erlenmeyer flask filled with bright coloured materials.

The bottom of a glass Erlenmeyer flask is in the centre, filled with dark green liquid. Arranged around it, on a white table, are six round petri dishes. Two are filled with white material marked with black lines and dots of growing bacteria. Another is deep amber with black marks. The fourth is pale gold and printed with numbers and other patterns. The fifth is pale green and the sixth is red. 

What are the benefits of using bacteria?

• Unlike synthetic dyes, the pigments produced by bacteria are nontoxic and biodegradable.
• Because of the way they’re grown, pigments from bacteria attach to fabric without the use of harsh fixatives. Fixatives are chemicals that help dyes and pigments attach to fabric, so they don’t wash out.
• Unlike other natural pigments, bacteria are cheap to produce, grow quickly and do not require any land to produce.
• As an added bonus, many bacteria pigments can kill microorganisms and even help to treat cancer!

As the world becomes more concerned about sustainability, the future of dyes and pigments may come from the tiny but mighty bacteria.