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Appl. Environ. Microbiol., Jun 1995, 2218-2223, Vol 61, No. 6
S Grkovic, TR Glare, TA Jackson and GE Corbett
The bacteria Serratia entomophila and S. proteamaculans cause amber disease
in the grass grub, Costelytra zealandica (Coleoptera: Scarabaeidae), an
important pasture pest in New Zealand. Disease symptoms include rapid
cessation of feeding and amber coloration of larvae. A 105-kb plasmid
(designated pADAP) has consistently been found only in pathogenic isolates
of both species. Investigations into the involvement of pADAP in amber
disease have been hindered by the lack of both a selectable marker on the
plasmid and a reliable transposon delivery system. Kanamycin-resistant
transposon insertions into three cloned HindIII fragments (9.5, 9.6, and
10.6 kb) were isolated and introduced into pADAP by shuttle mutagenesis.
Inserts into the 9.5-and 9.6-kb HindIII fragments on pADAP did not alter
disease-causing ability. When plasmids with inserts into the 9.6-kb region
were conjugated into plasmid-minus, nonpathogenic isolates of S.
entomophila and S. proteamaculans, all of them became pathogenic.
Transposon insertions into two regions of the 10.6-kb HindIII fragment
continued to cause cessation of feeding but failed to produce amber
coloration. Further analysis of a mutant from each amber-minus region
(pADK-10 and pADK-13) demonstrated that the antifeeding effect was produced
only at dosages higher than that of the wild-type strain. Complementation
with the wild-type HindIII fragment restored full-blown disease properties
for pADK-13, but not for pADK-10.
Copyright © 1995, American Society for Microbiology
Genes Essential for Amber Disease in Grass Grubs Are Located on the Large Plasmid Found in Serratia entomophila and Serratia proteamaculans
Environmental Pest Management, AgResearch, Lincoln, New Zealand
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