Characterisation of Antimicrobial proteins

This project involved the isolation and sequencing of proteins found in the mucus of the brown garden snail, Cornu apsersum, seeking potential antimicrobial properties, elements which are working to stop the growth of bacteria.

Research into naturally occurring antimicrobial substances has yielded effective treatments. One area of interest is peptides and proteins produced by invertebrates as part of their defence system, including the contents of mollusc mucous.

Mucous produced by the African giant land snail, Achatina fulica has been reported to contain two proteins with broad spectrum anti-bacterial activity. Mucous from the brown garden snail, Helix aspersa appears to have skin regeneration properties.

This study sought to investigate the antimicrobial properties of H.aspersa mucous. Mucous was collected from H.aspersa snails, diluted in PBS and centrifuged, with the supernatant tested against a wide range of organisms in a disc diffusion antimicrobial assay.

This was followed up with comparative experiments involving A.fulica , including bacteriophage assays. Mucous from both species of snail was passed through a series of protein size separation columns in order to determine the approximate size of the antimicrobial substance. Electrophoresis was also carried out on the H.aspersa mucous.

Three proteins were identified and partially sequenced.

Results indicated that H.aspersa mucous had a strong antibacterial effect against several strains of Pseudomonas aeruginosa and a weak effect against Staphylococcus aureus. Mucous from A.fulica also inhibited the growth of S.aureus, but the broad spectrum of activity reported by other workers was not observed.

Antimicrobial activity was not caused by bacteriophage. Size separation experiments indicated that the antimicrobial substance(s) in H.aspersa were between 30 and 100 kDa. Electrophoresis revealed two proteins in this region – 30-40 kDa and 50-60kDa. These do not correspond with antimicrobial proteins previously reported in A.fulica. This study found one or more novel antimicrobial agents in H.aspersa mucous, with a strong effect against P.aeruginosa.

The project funded an MRes student, who successfully defended their theses and was awarded the degree.

The work contributed to a peer reviewed publication, Pitt, S., Graham, M. A., Dedi, C., Taylor-Harris, P. M., & Gunn, A. (2015). Antimicrobial properties of mucus from the brown garden snail Helix aspersa. British Journal of Biomedical Science, 72(4), 174-181. https://doi.org/10.1080/09674845.2015.11665749