Identification and sequence of an unstable DNA element in the entomopathogenic bacteria Photorhabdus temperata strain K122.

Aims: A search was conducted for a difference in genome composition between phenotypic variants of the insect pathogenic bacteria, Photorhabdus temperata.

Methods: An unstable 300 bp fragment of DNA was identified by amplified fragment length polymorphism (AFLP) analysis, which was not, however, associated with phenotypic variation.

Results: During prolonged culturing of the bacteria, one copy of the repeated fragment was deleted and a restriction site linked to one of the copies was lost or gained.

The ner gene of Photorhabdus: effects on primary-form-specific phenotypes and outer membrane protein composition.

The nematode-bacterium complex of Heterorhabditis-Photorhabdus is pathogenic to insect larvae. The bacteria undergo a form of phenotypic switching whereby the primary form, at the stationary phase of the growth cycle, makes a range of products and has the capacity to support nematode growth, whereas the secondary form does not express these phenotypes. The work described here investigated the mechanism regulating phenotypic variation by transforming the primary cells with secondary-form DNA on a low-copy-number vector and screening for colonies which did not produce the yellow pigment characteristic of primaries.