A select group of bacteria plays a key role in the phenomenon of ice nucleation; their actions having an impact on the frost sensitivity of plants, the winter survival of certain insects, and even on weather systems. This is one of few topics to integrate the ice nucleation research of plant physiologists, crop scientists, microbiologists, biochemists, bacteriologists, entomologists, and food scientists worldwide. The National Institute of Sericultural and Entomological Science announced that the results of research aimed at biologically controlling overwintering insect pests using ice-nucleating active (INA) bacteria, which can colonize insect guts. Recently, the potential use of INA microorganisms to control hibernating insect pests has attracted attention and several American research groups reported that the tolerance to cold of several pests fed INA Pseudomonas syringae decreases. However, the biological control effectiveness of INA bacteria was lost after a short time because Pseudomonas syringae cannot colonize insect guts. Researchers at the National Institute of Sericultural and Entomological Science isolated Erwinia (Pantoea) ananas from several insects and found that some strains of Erwinia ananas have INA capacity. The mean supercooling point (SCP) of mulberry pyralid larvae ingesting INA Erwinia ananas, which can grow well in the gut, was measured at -4.7 C three days after treatment, or 6.6 C higher than in control treatments. In contrast, the mean SCP of larvae ingesting INA Pseudomonas syringae, which cannot grow in the gut, was -9.0 C three days after treatment. Researchers also found that more than 80% of the mulberry pyralid larvae ingesting INA Erwinia ananas froze and eventually died when exposed to a temperature of -6.0 C for 18 hours, while most untreated larvae survived, indicating that gut colonization by INA Erwinia ananas significantly reduced the cold-resistance of the insects. Researchers next transformed the ice nucleation gene of Erwinia ananas into Enterobacter cloacae, a well-known insect-resident bacteria. The mean SCP of mulberry pyralid larvae ingesting the transgenic Enterobacter cloacae was -3.3 C, or 8.0 C higher than that of untreated larvae. Furthermore, most of the larvae ingesting the transgenic strain froze and died when exposed to a temperature of -5.0 C for 18 hours three to seven days after ingestion. These findings suggest that the INA strains of Erwinia ananas and transgenic Enterobacter cloacae are potentially effective as an agent for the biological control of insect pests.
INA is a very complicated study of microorganisms used to affect the freeze susceptibility of insects. These nucleators are also found in leaves, in clouds, oceans and animals. Dr. Marcia R. Lee , Associate Professor of Microbiology at Miami University has done a great deal of research on this topic. Her interest includes both projects in which we focus on the basic molecular biology and applied use as means for biological control of insect pests. Her research focuses in on controlling the Colorado potato beetle, using INA bacteria and fungi as the control agent.
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This site was designed by Julie Vidic, Dan Shields and Bryan Pennix for MBI 699.W in August of 2000.