Biomedical applications for bacteriocins in infection and oncology

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dc.contributor.advisor Hill, Colin en
dc.contributor.advisor Ross, R. Paul en Ellis, Jenna-Claire 2019-06-21T11:38:23Z 2018 2018
dc.identifier.citation Ellis, J-C. 2018. Biomedical applications for bacteriocins in infection and oncology. PhD Thesis, University College Cork. en
dc.identifier.endpage 207 en
dc.description.abstract Lantibiotics are a subclass of a group of bacterially produced antimicrobial peptides called bacteriocins. They are characterized by post-translation modifications resulting in the presence of unusual amino acid residues such as dehydroalanine (Dha), dehydrobutyrine (Dhb) and lanthionine/ methyllanthionine. Interest in using bacteriocins as alternative therapeutics in multiple settings has grown in recent years. Nisin in particular has been the subject of many studies due to it being well characterised, approved by the FDA, widely used as a food preservative (EU number E234) and having GRAS (generally regarded as safe) status. Nisin has bioengineered to generate multiple variants with advantageous properties, including enhanced antimicrobial activity. Nisin is also capable of inducing its own production (auto-induction) through the LisRK sensor kinase system. In Chapter 2 we examine the self-induction properties of a previously created nisin variant “nisinAAA” by substituting positions K12 and H31 independently, revealing that ten variants retained the ability to induce the PnisA promotor (K12K/H31H, K12V, K12Q, K12W, K12T, K12A, K12C, H31N, H31K and H31R). Amino acid substitutions at positions K12 and H31 were also made simultaneously generating the variant K12V-AAA-H31V, a variant previously shown to be trypsin and chymotrypsin resistant, but which lost its capacity for self-induction. Our results confirm that amino acid substitutions R, N and K at H31 are the only substitutions capable of maintaining autoinduction. Given that all three are cut sites for trypsin or chymotrypsin we conclude that any substitution at position H31 of the nisin-AAA variant will lead to either loss of auto-induction or a peptide which is sensitive to digestion by chymotrypsin. The number of clinically significant bacteria becoming antibiotic resistant is increasing, along with concerns of pandrug-resistance (resistance to all current drugs), emphasizing the need to introduce new therapeutics into the clinic. In Chapter 3, following an initial screening involving nisin, lacticin 3147 and several other bacteriocins, it was observed that bacteriocins could enhance the antimicrobial activity of classical antibiotics against selected clinically significant bacteria. Levels of antibiotics often associated with adverse effects and antibiotic resistance could be reduced in the presence of either lacticin 317 of nisin Z. Enhanced antimicrobial activity was seen between lacticin 3147 and penicillin G as well as vancomycin. In addition, methicillin (which is no longer used very much in clinical settings) showed partial synergistic activity in combination with nisin Z, suggesting the possibility of reviving old therapeutics with the aid of new antimicrobials. Given that the anti-cancer effects of bacteriocins have been largely unexplored, in Chapter 4 we investigate the potential use of nisn Z as an alternative treatment for colorectal and oesophageal cancers, which have with high incidence and poor prognosis. It was observed by morphological examination that nisin Z elicited apoptotic cell death in 4 colorectal cancer cell lines and potentially autophagy mediated cell death in 2 oesophageal cancer cell lines. Confocal microscopy analysis along with flow cytometry profiles further supported autophagic cell death in oesophageal cell lines, whereas apoptotic cell death was supported in colorectal cell lines by flow cytometry. Upon further analysis it was observed that one colorectal cancer cell line, HCT116, initiated apoptotic cell death through the intrinsic pathway, as inferred by the upregulation of the protein caspase-9. As a consequence of the studies presented in this thesis, it is possible that strategies will emerge to facilitate the use of bacteriocins such as nisin Z and lacticin 3147 in clinical settings for the treatment of multiple conditions. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2019, Jenna-Claire Ellis. en
dc.rights.uri en
dc.subject Oncology en
dc.subject Bacteriocins en
dc.subject Nisin en
dc.subject Biomedical applications of nisin en
dc.subject Bioengineering of nisin en
dc.subject Bacteriocins as anti-cancer agents en
dc.subject Bacteriocins and skin pathogens en
dc.subject Lacticin 3147 en
dc.subject Bacteriocins and antibiotics en
dc.title Biomedical applications for bacteriocins in infection and oncology en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD en
dc.internal.availability Full text available en
dc.description.version Accepted Version
dc.description.status Not peer reviewed en Microbiology en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.internal.conferring Summer 2019 en
dc.internal.ricu APC Microbiome Institute en

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