Clark, Laura et al. (2015) International Worm Meeting "Return to the death star: Coryneform bacteria as pathogens of C. elegans."

Burkovski, Andreas, Mattos-Guaraldi, Ana Luiza, Azevedo Antunes, Camila, Hodgkin, Jonathan, Clark, Laura

[International Worm Meeting, 2015]

Two novel nematopathogenic Leucobacter were isolated from nature and display remarkable modes of pathogenicity1, some of which can be recapitulated using members of the human-pathogenic genus Corynebacterium.A bacterium, CBX151, was isolated from nematodes living on a rotting banana trunk in the Cabo Verde islands and identified as a novel subspecies of Leucobacter celer. When introduced to Caenorhabditis elegans N2, CBX151 adhered to the nematode cuticle in a thick "fur coat" and impaired worm movement on solid medium, but did not affect lifespan. However, when infected worms were added to aqueous medium they immediately aggregated by their tails into a rosette-like formation, or "worm-star", from which it was almost impossible to escape. Worms trapped in stars died within 24 hours and CBX151 proliferated using the worm carcases as a nutrient source. This novel phenomenon relies on exceedingly robust adhesion between the bacteria and the worm cuticle.A second bacterium, CBX152, was isolated as a co-infection with CBX151 but identified as a distinct novel species of Leucobacter. CBX152 does not adhere to the worm cuticle but causes a distinctive rectal swelling and is usually lethal within 24 hours of infection. Infection with CBX152 induces a strong immune response in the worms. Surprisingly, C. elegans mutations which confer resistance to CBX152 frequently induce hypersusceptibility to CBX151.Recent work using the human pathogens Corynebacterium diphtheriae, Corynebacterium ulcerans and Corynebacterium pseudotuberculosis, and the non-pathogen Corynebacterium glutamicum shows that these bacterial species can also induce star formation slowly in wild-type worms, as well as severe tail swelling. Characterisation of the tail-swelling response using immunocompromised worms reveals the involvement of daf-16 and the ERK map kinase pathway.The fascinating worm-trapping strategy exhibited by CBX151 and pathogenic Corynebacteria opens new avenues of inquiry into the mechanisms by which pathogens exploit host resources. Moreover, interactions between coryneform bacteria and soil nematodes are likely to be ecologically important and diverse, in view of the abundance of these bacteria in soil.1. Hodgkin et al 2013. Curr Biol 23, 2157-2161.

Miao-Chih Tsai et al. (2003) International Worm Meeting "chp-1, a CHORD domain containing protein required for early embryonic polarity"

Peder Zipperlen, Miao-Chih Tsai, Julie Ahringer

[International Worm Meeting, 2003]

Asymmetric cell divisions are of substantial importance during the development of most organisms but how asymmetries elaborately arise within a single cell to set up the main body axes is still not clear in C. elegans. To identify new genes required for this process, we analysed most embryonic lethal genes, which were found from our genome wide RNAi screen (1), using time-lapse video-microscopy. PAR genes are the most important players in early embryonic polarity and we are interested in how they are regulated and signal to downstream effectors. We identified chp-1 as a new gene resulting in a par-like mutant phenotype. chp-1 (RNAi) embryos show a symmetric first cleavage, complete or partial rotation of the AB spindle, and near-synchronous division of AB and P1. Like in par-3 or par-6 mutants, PAR-2 is found nearly all around the cortex of 1 and 2 cell chp-1 (RNAi) embryos, with PAR-6 reduced to a small patch. CHP-1 also functions in germline development as chp-1 (RNAi) animals develop a strong sterility phenotype. CHP-1 contains two zinc-binding domains called CHORD I and CHORD II (cysteine and histidine rich domain). All non-plant members inthis highly conserved protein family have a C-terminal region that shares homology with yeast SGT1, a suppressor of a G2 allele of yeast SKP1, which is a component of the SCF ubiquitin ligase complex. The CHP-1 homolog in plants, RAR1, is in a complex with the COP9 signalosome, which is thought to regulate the SCF. CHP-1 is a uniformly distributed cytoplasmic protein. We found that CHP-1 interacts with SGT-1 using a yeast two hybrid assay, as in plants (2). We are searching for other CHP-1 interacting proteins to try to understand its mechanism of action. The link between RAR1, the plant CHP-1 homologue, and the SCF ubiquitin ligase complex (2) suggests that protein degradation by the SCF might be involved in polarity establishment, and we are investigating this possibility. 1. Kamath et al. (2003). Nature 421, 231-7; Fraser et al (2000) Nature 408, 325-330 2. Azevedo et al (2002). Science 295, 2073-6