Steven A Forst

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Xenorhabdus and Photorhabdus spp. are gram negative gamma proteobacteria that form entomopathogenic symbioses with soil nematodes. They undergo a complex life cycle that involves a symbiotic stage, in which the bacteria are carried in the gut of the nematodes, and a pathogenic stage, in which susceptible insect prey are killed by the combined action of the(More)
INTRODUCTION .........................................................................................................................................................21 PHYLOGENY AND TAXONOMY .............................................................................................................................23 Phylogeny(More)
Xenorhabdus nematophila is an emerging model for both mutualism and pathogenicity in different invertebrate hosts. Here we conduct a mutant study of the EnvZ-OmpR two-component system and the flagella sigma factor, FliA (sigma28). Both ompR and envZ strains displayed precocious swarming behaviour, elevated flhD and fliA mRNA levels and early production of(More)
Two-component signal transduction systems, consisting of histidine kinase (HK) sensors and DNA-binding response regulators, allow bacteria and archaea to respond to diverse environmental stimuli. HKs possess a conserved domain (H-box region) which contains the site of phosphorylation and an ATP-binding kinase domain. In this study, a genomic approach was(More)
Xenorhabdus nematophilus is a symbiotic bacterium that inhabits the intestine of entomopathogenic nematodes. The bacterium-nematode symbiotic pair is pathogenic for larval-stage insects. The phase I cell type is the form of the bacterium normally associated with the nematode. A variant cell type, referred to as phase II, can form spontaneously under(More)
Members of the genus Xenorhabdus are entomopathogenic bacteria that associate with nematodes. The nematode-bacteria pair infects and kills insects, with both partners contributing to insect pathogenesis and the bacteria providing nutrition to the nematode from available insect-derived nutrients. The nematode provides the bacteria with protection from(More)
The tobacco hornworm, Manduca sexta, is a model lepidopteran insect used to study the pathogenic and mutualistic phases of entomopathogenic nematodes (EPNs) and their bacterial symbionts. While intestinal microbial communities could potentially compete with the EPN and its bacterial partner for nutrient resources of the insect, the microbial gut community(More)
OmpR is a DNA-binding protein that regulates transcription of ompF and ompC. The activity of OmpR is controlled by the inner membrane osmosensor, EnvZ. In order to study the signaling process between EnvZ and OmpR, we analyzed two different envZ strains: the envZ473 strain, in which OmpC is constitutively produced and OmpF is fully repressed, and the envZ3(More)
Xenorhabdus nematophila, a Gram-negative bacterium belonging to the Proteus clade of the family Enterobacteriaceae, forms a mutualistic association with the soil nematode Steinernema carpocapsae. The nematode invades insects and releases Xenorhabdus into the haemolymph, where it participates in insect killing. To begin to understand the role of fimbriae in(More)
Xenorhabdus nematophilus is an insect pathogen that lives in a symbiotic association with a specific entomopathogenic nematode. During prolonged culturing, variant cells arise that are deficient in numerous properties. To understand the genetic mechanism underlying variant cell formation, a transposon mutagenesis approach was taken. Three phenotypically(More)