To grow and produce crops under almost any condition, plants need to make good use of all nutrients available to them. While they are masters at absorbing some nutrients from the air and soil, they are struggling with others.

One such problematic element is nitrogen. Even though nitrogen makes up about 80% of the atmosphere, it is mainly present as dinitrogen gas N₂.

This means two nitrogen atoms are tightly bound to one another via three strong and energy-rich bonds. In this form, plants can neither take up the nitrogen nor use any of the nitrogen atoms to make other molecules from them.

Yet, they need nitrogen since it is part of every DNA molecule, protein, the energy provider ATP and many vitamins. Hence, plants need a way to acquire that element in a simple way that does not cost them too much energy.

Enter bacteria.

Diazotrophic bacteria fix nitrogen

The so-called diazotrophs have developed a highly efficient enzyme complex to capture, or fix, dinitrogen from the atmosphere and break up its energy-rich bonds. This complex is the nitrogenase, and all diazotrophs use one of three types of nitrogenase.

The most efficient nitrogenase contains a molybdenum ion at its core, while other nitrogenases use vanadium or iron. These metals are extremely rare in the environment. Hence, depending on which one is available, bacteria regulate which of the three nitrogenases to produce.

After capturing a dinitrogen molecule, the nitrogenase enzyme transfers energy in the form of protons and electrons to it. This eventually breaks up the bond between the two nitrogen atoms and produces two ammonium ions NH₃⁺.

Bacteria then use the ammonium ions for their own growth and share the surplus with their friends and partners. In Nature, several symbiotic relationships exist between bacteria and other organisms which are based around the nitrogen-fixating superpower of bacteria.

Soil bacteria share fixed nitrogen with plants

The best known nitrogen-fixing organisms are soil bacteria from the families Bradyrhizobium, Frankia, Bacillus, Clostridium, Burkholderia and Pseudomonas. These either live freely in the soil or form symbiotic relationships with plants.

Especially important are symbiotic rhizobia like Bradyrhizobium and Frankia. Plants attract these soil bacteria to their roots by sending out special molecules, which the bacteria respond to via their quorum sensing receptors. Within the root network of legume plants, the bacteria then build little nodules in which they live protected from the surrounding.

Within the nodules, bacteria fix and convert nitrogen with their enzyme complexes, which requires a lot of energy. Gladly, the host plant provides this energy in the form of sugars and organic acids that it produces with photosynthesis. The plant then transports these molecules into the root nodules, where the bacteria break them up, extract their electrons and thus gain the necessary energy.

After breaking up the nitrogen using these very electrons, the bacteria transport the produced ammonium from the nodules into the plant. With the ammonium, the plant makes DNA, proteins and vitamins; everything that it needs to grow and produce crops and fruiting bodies. Hence, rhizobia bacteria are highly important for the health of plants as well as crop production and yield.

Marine bacteria can fix nitrogen

Soil bacteria are not the only nitrogen-fixing organisms; marine bacteria are also important for global nutrient cycles. For example, cyanobacteria form long filamentous multicellular organisms, with some cells specialised in nitrogen fixation.

Often, cyanobacteria are closely associated with other marine bacteria with which they share nitrogen. So far, scientists do not fully understand these types of interactions but are sure that nitrogen-fixing organisms are crucial for the marine food web and the survival of many species under water.

When temperatures are high enough and nitrogen concentrations are optimal, you can pretty much see the nitrogen-fixation process. A green blanket on the water surface is a sign for cyanobacteria that power both photosynthesis and nitrogen fixation with the carbon dioxide and nitrogen from the air. This so-called algae bloom is mainly due to cyanobacteria like Aphanizomenon, Dolichospermum, Anabaena and Synechococcus bacteria.

Soil bacteria as biofertilisers for sustainable food production

Since some soil bacteria are so efficient in fixing nitrogen and providing it to the plant, they have also become valuable in agriculture. Some so-called biofertilisers consist of bacteria that are added to soil or plants to build symbiotic relationships with them, helping them grow better and produce bigger crops.

Hence, biofertilisers containing bacteria are an efficient and sustainable way to produce more food and in higher quality. With this, farmers will rely less on synthetic fertilisers while maintaining high crop yields. Additionally, using nitrogen-fixing bacteria as biofertilisers helps protect the health of the soil and the environment.

The post How bacteria help feed the world by fixing nitrogen appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

But as we know all this plastic is seriously hurting our planet, the animals on it, the plants and also ourselves. Not only plastic is incredibly stable and its breakdown products can be found almost everywhere, but producing plastics takes a massive toll.

Producing plastics hurts our planet

Making plastic materials is an energy-rich process that requires extracting and burning fossil fuels and petroleum. Chemicals from petroleum are extracted and combined into long chains called polymers.

However, petroleum and fossil fuels are resources that are limited. Plus, burning fossil fuels releases a lot of carbon dioxide, which leads to climate change and air pollution.

Currently, it is still easier and cheaper to make new plastics than recycling and reusing the already plastic items. Plastics are very durable, so it takes a lot of energy to break them down and melt them into a reusable form.

The idea is to find a greener and more sustainable way to make plastics.

Gladly, there is—bacterial-generated plastics!

Bio-plastics from bacteria

Many bacteria produce products that we use in our daily lives, from fermented foods like yoghurt, kombucha and beer to biofertilizers and ethanol that we use for biofuels. For example, the bacterium Escherichia coli, commonly known as E. coli, produces many medicines, like antibiotics and insulin used for diabetic treatment.

So, asking bacteria to make plastic isn’t that hard to believe.

How do bacteria make bio-plastics? 

Plastics are long chains of smaller units called plastic monomers. These monomers can look different, which finally make the different kinds of plastics.

When bacteria have too much energy inside their cells, they produce a lot of these monomers. They then link these monomers into polymers to store energy.

Interestingly, different bacteria can produce different kinds of monomers. And different combinations of these monomers make different plastic polymers.

When living organisms like bacteria or fungi produce plastics, these plastics are called bio-plastics.

For example, several microorganisms, such as Burkholderia xenovorans and Pseudomonas strains produce the polymer polyhydroxyalkanoate (PHA). In these cases, PHA serves to store carbon and energy during times of hunger.

You can understand PHA as fat in our bodies; the bacteria store energy and carbon for when they need the extra energy. But instead of viewing PHAs as fat, researchers are learning ways to use these polymers to create sustainable, biodegradable bio-plastics!

Engineering bacteria to produce bio-plastics

By learning how to use building blocks already made in nature, we can create plastics that are a lot healthier for the planet. But first, scientists need to make sure bacteria can produce enough bioplastic polymers to meet the worldwide demand.

To achieve this, even bacteria need some engineering help from scientists to produce more of the bio-plastics. Maybe engineering bacteria sounds scary, but it just means adding genetic material to a bacterial cell so that the cell knows how to produce the wanted product.

Genetic engineering is how E. coli makes insulin. And that same E. coli can also be engineered to make bio-based polymers.

One group even engineered E. coli to produce common plastic building blocks from the simple sugar glucose. Glucose is an abundant and renewable starting material, making bacterially produced plastics more sustainable than processes that rely on fossil fuels. Plus, this one-step process using E. coli is much simpler than the current way to make plastics.

But it is not just E. coli that scientists are trying to use to make bio-plastics. Researchers engineered both the bacteria Novosphingobium aromaticivorans and Ralstonia eutropha to produce biopolymer building blocks. However, we still need more research to optimize the process.

Benefits of bacterial bio-plastics

The plastics made by bacteria require less burning of fossil fuels, while many precursors used by bacteria are also sustainable. Both reducing non-renewable resources and instead using renewable resources makes bio-plastics a healthier and ‘greener’ option for the planet.

Additionally, some of the bio-plastics are more biodegradable than conventional plastics. Because these polymers are already natural products, other microorganisms and natural processes already know how to break them down and release natural products back into the environment.

Synthetic polymers found in traditional plastics are meant to last forever and can take decades to break down! This means that all the plastic trash fills up our landfills and oceans.

One study found that a bio-plastic item had a lower environmental impact as compared to a traditional plastic item over the item’s lifetime. That’s because the production of bio-plastics emits fewer greenhouse gases, uses fewer fossil fuels, and produces fewer toxins as compared to traditional plastic production.

In all these ways, bacterial bio-plastics are making the Earth greener.

A greener future with bacterial bio-plastics

Plastic pollution is a threat to our planet. These items overflow our landfills and oceans, where they sicken us and wildlife. In 2010 alone, it was estimated that up to 12.7 million metric tons of plastic ended up in the oceans! All this plastic hurts aquatic life and our planet’s marine ecosystems.

Luckily, scientists and engineers are exploring ways for bacteria to reduce our plastic pollution, both by creating bioplastics and degrading already produced plastics.

Using bacteria and bacterial enzymes, we can soon produce biodegradable plastics with less energy. From food to medicine to plastics, microbes are important for producing items we need to live.

However, even with microbes’ help, we can all play a part by reducing our plastic consumption, buying reusable over disposable products and recycling our plastics appropriately.

Along with microbes, we can save the planet!

Takeaway messages from this week’s article

• Plastic production is a major burden on the planet
• Bacteria can produce the building blocks for bio-plastics
• Bio-plastics start with sustainable precursors and are more environmentally friendly as compared to fossil fuel-derived plastics

The post Bacteria produce green bio-plastics appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world