TABLE CONTENTS

molecular information available on this parasite. Over 15,000 ESTs have been produced as a
resource for studies on biology of B. xylophilus. The function of selected pathogenicity genes
has been analysed by several studies and accumulated data has revealed that horizontal gene
transfer (HGT) from both fungi and bacteria has played an important role in ability of
nematode to feed on both fungi and plants. A series of pathogenicity genes including those
encoding several cell wall degrading enzymes such as cellulase, pectate lyase and beta-1,3-
glucanase have been characterised, and this work is continuing with studies on an expansin.
Attempts to apply RNAi to this nematode are also underway in order to investigate gene
function in more detail. The EST work and other relevant studies could be a precursor to a
larger genomics project.
Completion of a Pasteuria Genome Sequence: A Heuristic Approach to its
Common Thread
Davies, K.G. (1), J.E. Schaff (2), B.R Kerry (1) & C.H Opperman (3)
(1) Plant Pathology and Microbiology Department, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ,
UK; (2) Genome Science Laboratory, North Carolina State University, Raleigh, NC 27695 USA; (3) The Centre
for the Biology of Nematode Parasitism, North Carolina State University, Raleigh, NC27965, USA
Recent attempts to sequence the Pasteuria penetrans genome using traditional Sanger
approaches proved unsuccessful because it was difficult to produce good libraries from
miniscule amounts of DNA isolated from endospores. The majority of sequences obtained
were from DOP amplified libraries which were biased. Instead, we have used a non-biased
limited amplification step that eliminated the cloning step and using 454 sequencing
technology, and have successfully sequenced the genome of P. penetrans. Annotation of the
genome is currently being undertaken which will provide a step-change in research on this
bacterium. The use of comparative genomics will assist in discovering new knowledge
regarding the interaction of this obligate bacterial parasite with its nematode host. What sort
of insights might we therefore expect?
The mapping of Pasteuria sequences from our previous genome survey onto completed
genomes of Bacillus spp., and using software such as ARTEMIS, has provided insights into
both attachment and culturing. For example collagen-like sequences only present in animal
parasitic Bacillus spp. are responsible for the production of hair-like collagen filaments
present on the surface of the exposporium, and the number of G-x-y repeats relates to the
length of the hair-like fibril. TEM studies of endospores have revealed two types of similar
hair-like fibrils. Genes in Pasteuria have been identified that encode for collagen-like fibrils
which we believe are involved in attachment.
Similarly, comparative genomics can be applied to other genes of interest and, combined with
biochemical knowledge have provided insights into in vitro culturing. Thus, the sporulation
pathway in Bacillus is well researched and the switch between vegetative growth and
sporulation is governed by a phosphorelay pathway. Cation concentration is important for
this pathway to function and the presence of copper appears to inhibit sporulation. The
removal of copper from vegetatively growing Pasteuria cultures aided the cultures to
sporulate.
5 th International Congress of Nematology, 2008 63