Hodgkin JA et al. (2000) Curr Biol "A novel bacterial pathogen, Microbacterium nematophilum, induces morphological change in the nematode C. elegans."

Hodgkin JA, Kuwabara PE, Corneliussen B

[Curr Biol, 2000]

The Dar (deformed anal region) phenotype, characterized by a distinctive swollen tail, was first detected in a variant strain of Caenorhabditis elegans which appeared spontaneously in 1986 during routine genetic crosses [1,2]. Dar isolates were initially analysed as morphological mutants, but we report here that two independent isolates carry an unusual bacterial infection different from those previously described [3], which is the cause of the Dar phenotype. The infectious agent is a new species of coryneform bacterium, named Microbacterium nematophilum n. sp., which fortuitously contaminated cultures of C. elegans. The bacteria adhere to the rectal and post-anal cuticle of susceptible nematodes, and induce substantial local swelling of the underlying hypodermal tissue. The swelling leads to constipation and slowed growth in the infected worms, but the infection is otherwise non-lethal. Certain mutants of C. elegans with altered surface antigenicity are resistant to infection. The induced deformation appears to be part of a survival strategy for the bacteria, as C. elegans are potentially their predators.

Azevedo Antunes C et al. (2015) Microbiology "Caenorhabditis elegans star formation and negative chemotaxis induced by infection with corynebacteria."

Hirata R, Simpson-Louredo L, Burkovski A, Hodgkin J, Azevedo Antunes C, Wanuske MT, Mattos-Guaraldi AL, Clark L, Ott L, das Gracas de Luna M, Hacker E

[Microbiology, 2015]

Caenorhabditis elegans is one of the major model systems in biology based on advantageous properties such as short life span, transparency, genetic tractability and ease of culture using an Escherichia coli diet. In its natural habitat, compost and rotting plant material, this nematode lives on bacteria. However, C. elegans is not only a predator of bacteria, but can also be infected by nematopathogenic coryneform bacteria such Microbacterium and Leucobacter species, which display intriguing and diverse modes of pathogenicity. Depending on the nematode pathogen, aggregates of worms, termed worm-stars, can be formed, or severe rectal swelling, so-called Dar formation, can be induced. Using the human and animal pathogens Corynebacterium diphtheriae and Corynebacterium ulcerans as well as the non-pathogenic species Corynebacterium glutamicum, we show that these coryneform bacteria can also induce star formation slowly in wild-type worms, as well as a severe tail-swelling phenotype. While C. glutamicum had a significant, but minor influence on survival of C. elegans, nematodes were killed after infection with C. diphtheriae and C. ulcerans. The two pathogenic species were avoided by the nematodes and induced aversive learning in C. elegans.

Salikin NH et al. (2021) Biomedicines "Novel Nematode-Killing Protein-1 (Nkp-1) from a Marine Epiphytic Bacterium Pseudoalteromonas tunicata."

Lebhar H, Marquis C, Egan S, Salikin NH, Nappi J, Dubois M

[Biomedicines, 2021]

Drug resistance among parasitic nematodes has resulted in an urgent need for the development of new therapies. However, the high re-discovery rate of anti-nematode compounds from terrestrial environments necessitates a new repository for future drug research. Marine epiphytes are hypothesised to produce nematicidal compounds as a defence against bacterivorous predators, thus representing a promising yet underexplored source for anti-nematode drug discovery. The marine epiphytic bacterium <i>Pseudoalteromonas tunicata</i> is known to produce several bioactive compounds. Screening heterologously expressed genomic libraries of <i>P. tunicata</i> against the nematode <i>Caenorhabditis elegans</i>, identified as an <i>E. coli</i> clone (HG8), shows fast-killing activity. Here we show that clone HG8 produces a novel nematode-killing protein-1 (Nkp-1) harbouring a predicted carbohydrate-binding domain with weak homology to known bacterial pore-forming toxins. We found bacteria expressing Nkp-1 were able to colonise the <i>C. elegans</i> intestine, with exposure to both live bacteria and protein extracts resulting in physical damage and necrosis, leading to nematode death within 24 h of exposure. Furthermore, this study revealed <i>C. elegans</i> dar (deformed anal region) and internal hatching may act as a nematode defence strategy against Nkp-1 toxicity. The characterisation of this novel protein and putative mode of action not only contributes to the development of novel anti-nematode applications in the future but reaffirms the potential of marine epiphytic bacteria as a new source of novel biomolecules.

Souza C et al. (2019) Antonie Van Leeuwenhoek "Virulence potential of Corynebacterium striatum towards Caenorhabditis elegans."

Simpson-Louredo L, Santos CDS, Souza C, Mota HF, Moreira LO, Faria YV, Mattos-Guaraldi AL, Colodette SDS, Cucinelli ADES, Luna MDG, Cabral FO, Canellas MEFC

[Antonie Van Leeuwenhoek, 2019]

Corynebacterium striatum strains have been increasingly reported as etiological agents of nosocomial infections and outbreaks in industrialized and developing countries. However, there are few studies focused on the virulence potential of C. striatum. A growing body of research supports the use of Caenorhabditis elegans as a model host for investigating the virulence potential of pathogenic bacteria, including corynebacteria. In the present study, chemotaxis behaviour, mortality, and morphological changes were investigated in nematodes infected by four C. striatum strains isolated from different clinical sites, and with different MDR profiles and PFGE types. The results showed chemotaxis of nematodes towards C. striatum. Nematode death (&gt;60%) was detected from the first day post-infection with all strains tested, but at different levels, independent of biofilm formation on catheter surfaces and differences in growth temperature between nematodes (20C) and mammals (37C). C. striatum 2369/II multidrug-resistant (MDR; from tracheal aspirate of a patient undergoing endotracheal intubation) and 1961/III multidrug-sensitive (MDS; urine) strains led to 100% mortality in worms. Survival of nematodes was observed until 4 days post-infection with the C. striatum 1954/IV MDS strain isolated from a surgical wound (13%) and 1987/I MDR strain isolated from a patient with a lower respiratory tract infection (39%). The Dar phenotype was observed post-infection with all MDS and MDR strains except 1954/IV. All strains showed the capacity for bagging formation. Star formation was observed only with strains that led to 100% nematode mortality. In conclusion, C. striatum was found to exert virulence for C. elegans. Variations in nematode morphological changes and levels of mortality indicate differences in the virulence potential of C. striatum independent of clinical isolation site, capacity for biofilm formation, and MDR and PFGE profiles.