Native Biofilms On Mung Bean Sprouts

Native Biofilms on Mung Bean Sprouts

William F. Fett, Peter Cook

CAN. J. MICROBIOL. 49: 45-50 (2003)

Interpretive Summary: In the natural environment as well as industrial and medical settings bacteria are often present in biofilms. Biofilms are composed of groups of microbes attached to a surface and to each other by a matrix composed of excreted materials of microbial origin. Little is known about biofilms on plant surfaces. In this study we used a scanning electron microscope to study naturally occurring biofilms on the surface of mung bean sprouts. Results indicated that biofilms were abundant on the sprout surface and were comprised of both bacteria and yeasts. Some biofilms were several layers thick. Bacteria pathogenic towards humans or plants can become part of such biofilms and be much more resistant to removal by rinsing with water or to killing with chemicals. New antimicrobial interventions with the ability to eliminate bacteria in biofilms on sprouts are needed.

Technical Abstract: Native biofilms present on the adaxial surface of cotyledons of mung bean sprouts were studied by use of scanning electron microscopy. Biofilms were abundant on the plant surfaces and were comprised of rod-shaped bacteria, cocci-shaped bacteria or yeasts, often with one type of microbe predominant. In contrast to our earlier study of biofilms on green sprouts (alfalfa, clover, broccoli and sunflower), yeast and cocci were abundant on mung bean. Filamentous fungi were not observed. Sheet-like or fibrillar material (presumably composed of secreted microbial polysaccharides, proteins, lipids and nucleic acids) fully or partially covered the biofilms. Biofilms up to 5 mm in length were observed and some biofilms were comprised of more than a monolayer of microbial cells. Native biofilms on sprout surfaces undoubtedly play an important role in the ecology of plant epiphytic microbes and may also afford protected sites for plant and human bacterial pathogens.