No need for chemicals, bacteria can fertilize plants too— UP research reveals

Ramsa Salajin

When there is plant growth, there are invisible, skilled workers living in the soil right beneath a farmer’s boot. Pulling a plant out of the ground exposing the roots brings out bacteria’s hidden roles that UP scientists have discovered in the laboratory. 

In a study conducted by researchers from the University of the Philippines (UP) Microbiological Research and Services Laboratory, and Natural Sciences Research Institute, bacteria living in the plant roots of corn and bamboo were found to be natural plant helpers assisting them to grow, stay healthy, and resist diseases. 

The study titled “Multiple Plant Growth–Promoting Activities Exhibited by Root Associated Bacteria Isolated From Bamboo and Corn” uncovered 27 different kinds of bacteria and identified them by looking into their DNA. 

The bacteria came from 12 groups, with most belonging to Leclercia, Pantoea, Klebsiella, and Exiguobacterium. When tested in the lab, every single type of bacteria showed at least two traits that could help plants grow better.

Treasures on the Surface

Nitrogen makes up about 78% of the Earth’s atmosphere, but most organisms like plants cannot directly utilize it because of the strong chemical bond of this gas. 

Out of all the bacteria studied, mostly from the Klebsiella group, four were found to carry the nitrogen-fixation gene which is an essential enzyme that turns nitrogen gas into ammonia which can be used by plants.

The study also shows about 11 bacteria from the Pantoea group that are known to be pathogens or beneficial bacteria were able to make phosphorus present in the soil easier for plants to absorb. Phosphorus is necessary for Adenosine Triphosphate (ATP) production, which is vital for photosynthesis. Without enough phosphorus, plant leaves turn yellow or pale and remain smaller than normal. 

Interestingly, 100% of the bacteria tested could produce indole-3-acetic acid (IAA), a natural plant hormone called auxin which helps roots grow stronger and healthier, and 89% of the bacteria could make tiny compounds that capture iron from the soil and deliver it to plants.

Among all the rhizobacteria, Enterobacter roggenkampii B1-01 and Klebsiella oxytoca B1-04 stood out the most as they had all the plant-boosting abilities tested which confirmed that certain bacteria can be very effective at promoting plant growth.

The study specifically looked at bacteria from Cagayan Province, a top corn-producing area, which shows that the bacteria acting as biofertilizers are already adapted to local soil and climate, making them more effective for Filipino farmers.

According to the study, plants like wild lily, sugarcane, nipa palm, rice and cacao have already been explored to see what kinds of helpful bacteria live in their roots and soil. Corn, in this case, which is the country’s second most important staple crop after rice, has not been much explored. 

Another plant in the same family as corn is bamboo which is an important crop in the Philippines, with 62 species and 21 of them can only be found here in the country. Unlike corn, which is planted and harvested yearly, bamboo lives and grows for many years serving as a potential host to a larger and more diverse community of microbes compared to annual crops like corn. 

Reciprocity in Action

At the thin layer of soil right next to a plant’s roots, just a few millimeters thick is where the real action takes place. Roots do not simply sit there drinking water and nutrients. They actively interact with the soil community along with different bacteria living in it. 

By releasing sugars, amino acids, and other substances, roots attract microbes like bacteria and fungi as if plants are offering them a meal. In return,  these microorganisms provide nutrients, strengthen the plant’s defenses, and improve soil conditions.  

Since the surface where bacteria grow depends on stable soil around roots, erosion can wash away essential organic matter, minerals, and beneficial microbes that plants rely on. 

In corn fields or any crops, erosion can weather soil leaving the roots exposed and reducing the activity of nitrogen-fixing bacteria. This may result in weaker plants, lower yields, and a greater need for chemical fertilizers to make up for the lost natural fertility.

While chemical fertilizers help, we cannot disregard that it also exacerbates pollution in land, water, and air which can harm living organisms in the long run. 

The research findings revealed how isolated bacteria that lived in the soil around plant roots can help corn and bamboo plants grow faster and stronger but also make them healthier by protecting them from harmful organisms. The next step is to see if they work just as well in other kinds of plants. 

With climate change and growing populations, these bacteria may become a key not just through helping plants grow and photosynthesize but also in feeding the world in an eco-friendly way.