Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/1999
Publication Date: N/A
Interpretive Summary: Soybean cyst nematode (SCN), heterodera glycines, is a serious pest of soybean throughout soybean production areas in the United States. The nematode causes an annual production loss of $407 million. Crop rotation coupled with planting of resistant soybean is the nematode management practice utilized by most soybean producers who have identified infestations on their farms. However, optimal use of resistance is limited because there is a large number of SCN races and resistance in soybean to SCN is race specific. Biological control has potential as part of an integrated pest management program. In 1994 the bacterium Pasteuria sp. was identified in North America. In 1996 field studies determined its potential as a biological control organism. The research reported in the present manuscript documents studies that used DNA to define the phylogenetic position of the Pasteuria that attacks SCN. Some controversy exists in the literature as to whether Pasteuria should be classified as a bacterium or as an Actinomycete. This study proves that Pasteuria is a bacterium that is neither related to the Actinomyctes or to the true endospore forming bacteria, but is closely related to the genus Alicyclobacillus. The research reported herein will provide the foundation for taxonomic studies on several Pasteuria that parasitize nematodes but whose taxonomic position (species identification) is in question.
Technical Abstract: The 16S rDNA sequence of an undescribed species of Pasteuria that parasitizes the soybean cyst nematode, heterodera glycines, was compared to an homologous sequence of P. ramosa, a parasite of cladoceran water fleas of the family Daphnidae, and to those of thirty other bacterial species to determine its phylogenetic position among the gram-positive eubacteria. Phylogenetic analyses using maximum likelihood, maximum parsimony, and neighbor-joining methods showed that the herterodera glycines-infecting Pasteuria and its relative, P. ramosa, form a distinct line of descent within the Alicyclobacillus group of the Bacillaceae. These results are consistent with the view that the genus Pasteuria is a deeply rooted member of the Clostridium-Bacillus-Streptococcus branch of the gram-positive eubacteria, neither related to the actinomycetes nor closely related to true endospore-forming bacteria.