Why is There Slime in This Corn? The Salty Experiment

Featured Image Caption: According to the USDA, corn accounts for 95 percent of total feed grain production and use. Credit: “Corn field” by Ales Kladnik is licensed under CC BY 2.0, from Wikimedia Commons

Primary Source Article: Çam, S., Küçük, Ç., & Almaca, A. (2023). Bacillus strains exhibit various plant growth promoting traits and their biofilm-forming capability correlates to their salt stress alleviation effect on maize seedlings. Journal of Biotechnology, 369, 35–42. https://doi.org/10.1016/j.jbiotec.2023.05.004

Secondary Source Article: Paul, D., Lade, H. Plant-growth-promoting rhizobacteria to improve crop growth in saline soils: a review. Agron. Sustain. Dev. 34, 737–752 (2014). https://doi.org/10.1007/s13593-014-0233-6

The Good, The Bad, And The Biofilms

Biofilms can grow anywhere there is a surface: medical implants, aquatic ecosystems, and industrial pipes are but a few examples. Credit: “Thick bacterial biofilm lining part at the bottom of a creek left tributary of the Gorges du Ciron (France)” by Lamiot is licensed under CC BY-SA 4.0, from Wikimedia Commons

Biofilms are slimy shields made up of sugars and proteins. Either a single microorganism type or a community of a variety of microorganisms can collectively make this shield. Biofilms are often made by microbes such as bacteria and fungi to overcome extreme environments, competition from other microorganisms, or to colonize an environment. Biofilms have a bad reputation. Oftentimes, when we hear about a biofilm, we hear about a bacterium producing biofilm that has infiltrated a medical implant and is wreaking havoc on the human body. However, this is not always the case. Although it is true that biofilms can be harmful, they also have beneficial potential. Scientists have discovered that biofilms can protect crops and promote their growth in harsh soil conditions without having to resort to chemicals that are harsh to the environment.[

Don’t Be Salty, Get A Bacillus Boost Instead!

When a plant is exposed to high salt, the plant takes in salt and chloride ions. The result is disrupted hormones, stress on the plant cells, and negative effects on the root habitat, or rhizosphere. Rhizospheres are groups of microorganisms found in plant roots that help enhance plant activities such as fixing nitrogen in the soil. Overall, a salty environment prevents plants from doing what they do best: feeding us, giving us oxygen, and making a useful product. About 20% of agricultural land and 50% of cropland is salt stressed worldwide. Figuring out how to grow high yields of crops under climate change and harsh conditions is of great importance. Dr. Cam and his team have demonstrated that biofilms can be beneficial thanks to the help of a little friend called the Bacillus.

Bacillus subtilis is a bacterium capable of producing biofilms.  It has many applications in the science and biotechnology industry. “Bacillus subtilis bacteria, Gram stain” by Dr. Graham Beards, is licensed under CC BY-SA 4.0 from Wikimedia Commons

Bacillus is a type of rod shaped, cylindrical bacteria found in the environment. Bacillus is of interest to the agricultural field because it has plant growth promoting (PGP) properties. Some PGP examples include helping with plant metabolism or protection from fungi.

Scientists in Turkey wanted to do 4 things: isolate and identify Bacillus species from maize rhizosphere, figure out whether the species isolated had PGP potential, test what a salty environment would do to biofilms produced by strains, and finally, figure out what effect the biofilm forming isolates would have on maize growth under salty conditions

Once soil samples containing bacterial colonies were isolated and identified, they tested different strains for how well they could break down proteins, produce enzymes, and other activities. Some of the tests included how well different bacillus strains could grow in the presence of hydrogen cyanide, produce biofilm, dissolve phosphorus, and fight fungal pathogens. Whichever strains performed the best in these tests were selected to be used as a comparison for maize seedlings that grew in salty soil without bacillus assistance.

The results are promising. Dr. Cam and his colleagues from Turkey found that all the strains tested against the soil borne fungal pathogens showed antifungal activity. Maize that was inoculated with certain biofilm producing Bacillus strains under salt stress had higher chlorophyll content, longer roots, and shoots compared to regular maize plants without bacillus help. This marvelous feat demonstrates how biofilms might be used to improve crop yield and could help devise solutions that are less chemically harsh to the environment. Who would’ve thought slime in corn could be a good thing?

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Christina Andrea Alvear

Christina Andrea Alvear

I am a coordinator for a nonprofit organization in San Antonio, Texas. I earned a MS in Biology at the University of Texas at San Antonio. My goal is to make primary research fun and accessible to everyone while connecting with other science writing enthusiasts. I've explored a variety of careers from research, education, and nonprofit mental health, substance abuse, and healthcare programs. When I am not writing or working, I like to lounge around at a coffee shop on a weekend or enjoy a board game with friends.

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