Geographical distribution of milky disease bacteria in the eastern United States based on phylogeny

A phylogenetic grouping of 48 different isolates of milky disease bacteria isolated in the United States was determined using genomic RFLP analysis and 16S rDNA sequence comparison. A clear distinction between Paenibacillus popilliae isolates and Paenibacillus lentimorbus isolates was evident from the results of each procedure. The P. popilliae isolates segregated into two phylogenetic groups and the P. lentimorbus isolates segregated into three phylogenetic groups. In the United States, P. popilliae group 1 was generally isolated from insects collected west of the Appalachian Mountains. P. popilliae group 2 was only isolated from insects collected east of the Appalachian Mountains. P. lentimorbus groups 1 and 2 were obtained from insects collected west and south of the Appalachians. P. lentimorbus group 3 was identified in insects collected east of the mountains. From five different locations in Connecticut, 12 milky disease bacterial isolates were classified as P. popilliae and three were classified as P. lentimorbus. Except for one isolate, all P. popilliae isolates were of phylogenetic group 2. The three P. lentimorbus strains were isolated from diseased insects that had been collected from a localized area in the state. These three strains formed a separate phylogenetic grouping (i.e., group 3) of P. lentimorbus and, based on 16S rDNA sequence comparisons, were most similar to the newly identified P. lentimorbus Semadara strain recently isolated in Japan. All milky disease bacteria that had been isolated from commercially available insecticide preparations were identified as P. popilliae group 1.