Bacteria produce approximately 70% of microbial natural products with the bacterial class Actinobacteria being the major producer. They can contain over 30 Biosynthetic Gene Clusters (BGCs) encoding specialised metabolites. However, only a portion (up to 10%) of these BGCs are transcribed under normal laboratory conditions. Interspecies interactions play a role in the elicitation of specialised metabolites. Metabolites are often produced as a defence mechanism to kill or communicate with other strains. Therefore, co-culture techniques represent a potential method to elicit specialised metabolites that are not produced under mono-culture. In order to understand the chemical exchange between strains, the impact of bacterial interactions was assessed on the strains' ability to produce specialised metabolites resulting in altered phenotypes. The study comprised a total of 51 strains (48 Actinobacteria, two Pseudomonas and one Bacillus) across 72 tri-cultures (three strains) and 63 one-to-one cultures (two strains). Four co-culture techniques were used; tri-cultures, one-to-one cultures, pre-conditioned media and mixed fermentations. A total of 21 tri-cultures and 40 one-to-one cultures resulted in altered phenotypes as a result of bacterial interactions. Pre-conditioned media revealed that specialised metabolites were responsible for these alterations. The antibacterial screening showed that seven bioactive strains displayed larger inhibition zones under co-culture. The LC/MS-based metabolomics of five strains' mono-culture, six one-to-one cultures and two tri-cultures extracts revealed the production of interaction-specific metabolites. One interaction was subjected to Imaging Mass Spectrometry (IMS) in collaboration with CMAC and the National Physical Laboratory (NPL). The results demonstrated that bacterial interactions increase chemical diversity and that mass spectrometry-based comparative metabolomics represent an exciting strategy to prioritise novel chemistry.
|Date of Award||21 Oct 2021|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Katherine Duncan (Supervisor) & Nicholas Tucker (Supervisor)|