Plant disease control using iron-enriched sheaths naturally produced by bacteria

Bacteria have some extraordinary natural ways of protecting themselves against fungi and attacking microbes. For example, the iron-oxidizing bacteria, Leptothrix spp., produces microtubular hollow sheaths in aquatic environments where there is an up-welling of groundwater. The sheath is primarily composed of iron oxides (Fe/Si/P = 75/20/5 in the atomic ratio). Interestingly, a colloidal suspension of these Fe-enriched sheaths in powder form has been found to effectively suppress fungal pathogenesis.

Kazuhiro Toyoda and Jun Takada at the Okayama University, Japan, and co-workers investigated one such naturally-produced sheath (an Fe-enriched sheath) to determine its antifungal activities in vitro against several phytopathogenic fungi. The fungi tested included Botrytis cinerea, Colletotrichum higginsianum, and Mycosphaerella pinodes.

The fungi were inoculated on ethanol-killed onion epidermis. The researchers found that the germ tube (gt) and apprisorium (app) were particularly effective at causing penetration failure from appressoria when the powdered suspension was mixed with the spore.

These results indicate that the Fe-enriched sheath from Leptothrix spp. could provide a new protectant for plant diseases.

Kazuhiro Toyoda, Ph.D.¹, Tomonori Shiraishi, Ph.D.¹,
Hitoshi Kunoh, Ph.D.², Jun Takada, Ph.D.^2
1Graduate School of Environmental & Life Science,
²Graduate School of Natural Science & Technology

【Contact information】
Mototaka Senda, Ph.D.,
Director, Okayama University Silicon Valley Office,
2450 Peralta Blvd. #222 Fremont, CA 94536 USA
E-mail: takasenda@okayama-u.ac.jp