Not all biofilms are bad

A paper published in May 2025 in “Microbiology Spectrum” examined the practice of applying beneficial biofilms to calf hutches. To the authors’ knowledge, it was the first study to evaluate the use of beneficial biofilms in individual pre-weaned calf housing. One of the authors, Sarah Morrison, a research scientist at the William H. Miner Agricultural Research Institute in Chazy, NY, shared results from the project during an Iowa State University Extension presentation. A biofilm is a community of microorganisms such as bacteria, fungi or algae in which cells stick to each other and often to surfaces. The microorganisms are embedded in a slimy, glue-like matrix that provides protection against the environment. Often, biofilms have bad connotations – like tooth plaque or the film that can build up inside a bulk tank or livestock watering or cooling systems. Biofilms are extremely common in the dairy industry, particularly in milk processing and storage equipment. But there’s a flip side: Biofilms can also be beneficial. Following an oil spill, an oil-eating organism can be released which swarms around individual droplets, forming biofilms that reshape the droplets and accelerate the oil’s degradation. A beneficial bacteria found in soil – Bacillus subtilis – attaches to plant roots and forms biofilms. B. subtilis and the host plant work together to keep the plant healthy. In the chicken and swine industries, it’s been shown that positive biofilms offer some control on surface-associated microbial communities that can have a negative health impact on livestock. Specifically, they’ve been shown to reduce enteric pathogens on surfaces of bedding and reduce mortality in piglets and broilers. “There’s been examples in swine and poultry that beneficial biofilms can be used to complement cleaning and disinfection procedures,” said Morrison. Regardless of the livestock species, the basic idea is to apply beneficial bacteria to livestock housing surfaces following cleaning and disinfection. Those beneficial bacteria can develop into a positive biofilm inside the structures, leaving less room for the development of negative biofilms. The experiment at the Miner Institute involved spraying calf hutches with a microbial inoculant (LALFILM PRO, produced by Lallemand) containing six biofilm-forming strains of Bacillus spp . and two strains of Pediococcus spp . The inoculant came from Europe where this practice is more common, but Morrison was unsure if it is commercially available in the U.S. LALFILM PRO is a water-dispersible powder for dilution and is applied using a low-pressure spraying device. Cari Reynolds, Morrison’s graduate student on the project, said, “The strains selected are non-pathogenic, durable biofilm-formers and produce volatile and antimicrobial compounds that inhibit growth of competing bacteria. Bacillus spp . in particular are spore-formers, which are notably adherent to surfaces.” First the calf hutches were cleaned like normal. Then one of three treatments was applied to a group of hutches: no application, an application of distilled water and the application of the inoculant. The researchers were interested in two main questions: Would the inoculant adhere to the polyethylene calf hutch surfaces? And how would it alter the microbial composition growing on the hutches? The study found that the beneficial bacterial cocktail of Bacillus spp . and Pediococcus spp . was able to successfully colonize on polyethylene, and its application to individual polyethylene calf housing influenced microbial diversity and reduced the presence of undesirable bacteria on high-contact interior surfaces. Visual evidence from petri dish cultures showed a clear difference between treated hutches, which had less varied microbial growth, and control hutches, which Morrison said showed a wider variety of “yucky colonies.” One limitation of the study was that the inoculant was sprayed during the warmth of summer. Spraying during winter, especially in colder regions, would likely impact the growth and effectiveness of the applied film. Further studies are needed to understand the role of the positive biofilm in the health and development of pre-weaned calves; that was not the intent of this study. Morrison is also excited about other uses of positive biofilms in the dairy industry. Inoculating bedding, she hypothesized, needs to be studied further for its potential to control pathogens responsible for mastitis. Morrison said, “Not all biofilms are bad. We can actually use many of them to our benefit. We definitely need to follow-up on the work that we did, but I think any way that we can maintain that environmental cleanliness would be a benefit to our animals. If we can use these to our benefit, they will be a great tool in our toolbox to move forward.” by Sonja Heyck-Merlin Featured photo: Graduate student Cari Reynolds sampling for biofilms on the hutch surface. Photo courtesy of Sarah Morrison