1887

Abstract

Summary: Phylogenetic relationships among 18 isolates in the genus representing 13 species of diverse econutritional groups (pathogens of insects, plants, mushrooms, nematodes and spiders, and sparobes), were examined by using sequences from the internal transcribed spacer (ITS) and small nuclear (NS) rRNA regions. The isolates were also assessed for their abilities to infect insect larvae () and to cause necrosis in alfalfa (), and for their proteolytic, chitinolytic and pectinolytic activities. The phylogenetic data suggested that is polyphyletic in origin and is therefore a form genus. However, the phylogenetic tree supported the plant pathogens () as a clade. The alfalfa isolate of (isolate 595) was an interesting outlier to the main body of plant pathogens as it clustered with the insect pathogen . Strains of and were able to infect insects and are present in divergent groups in the consensus tree, suggesting that the ability to infect insects may have evolved independently many times. Similarly, the nematophagous species appear to have evolved independently along several different routes and one isolate, was able to infect insects. and all produced high levels of enzymes capable of degrading pectin, a major component of plant cell walls. The ability to excrete pectinase was a broad indicator of the ability to produce lesions on alfalfa. In the plant pathogens, the functions of a broad-spectrum protease were assumed by trypsins which degrade Bz-AA-AA-Arg-NA substrates (Bz, benzoyl; AA, various amino acids; NA, -nitroanilide). The insect pathogens and mushroom pathogen () were characterized by production of high levels of subtilisin-like proteases active against a chymotrypsin substrate (succinyl-Ala-Pro-Phe-NA) and the inability to clear pectin. The insect and mushroom pathogens, and several nematode pathogens, were distinguishable from the plant pathogens in their ability to produce chitinases.

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/content/journal/micro/10.1099/13500872-145-4-955
1999-04-01
2019-10-19
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/13500872-145-4-955
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