Bacterial propagation host changes the host range of a Staphylococcus aureus specific bacteriophage vB_SauP_EBHT without altering the phage genome

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Kemian tekniikan korkeakoulu | Master's thesis
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Date

2021-06-15

Department

Major/Subject

Biotechnology

Mcode

CHEM3022

Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering

Language

en

Pages

62 + 5

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Abstract

As an answer for the emergence of antibiotic resistance within pathogenic bacteria, the research and use of bacteriophages in treatment of infections has become a promising solution. This treatment is called phage therapy and it employs the capacity of phage to infect and kill its host. Bacteriophages recognise their host bacteria by their tail fibre proteins that determine their host range. In order to provide successful phage therapy, it is important to understand the interactions between the phage and its host. Bacteria have multiple ways to create resistance mechanisms against phages, which is one of the challenges concerning phage therapy. A yet unpublished research revealed that changing the production host caused a change in the host range of vB_SauP_EBHT, a Staphylococcus aureus specific lytic phage, without altering the phage genome. Here, the phage produced in the original host #6662 is referred to as ɸEBHT and the host range mutant phage, produced in strain #6433 is referred to as mEBHT. The aim of this work was to perform a comparative proteomics analysis for purified phage particles produced in the two different bacteria hosts. The samples were prepared for proteomics analysis with ion exchange chromatography, for which the run conditions were first optimized. The comparison of proteomics data between purified ɸEBHT and mEBHT phage particles was used to find proteins originating from the propagation hosts that are present in purified phage samples and have the potential to change the vB_SauP_EBHT host range. The host range difference was observed initially with two strains. Therefore, a collection of 77 S. aureus strains from human and pig origin, as well as 20 coagulase negative Staphylococcus strains were tested to discover how extensive the host range difference is between the phages. In the proteomics analysis 17 proteins originating from the host, with different abundancies between the two purified phage particles, were identified. Except for two enzymes, the identified proteins were part of regular upkeeping metabolism of the host and originated from the used host strain. The two enzymes, which were not part of regular bacterial metabolism, belonged to the class of M42 metallopeptidases. BlastP tool revealed a 98 % identity between these two peptidases, found from both samples, and they seemed the most prominent to cause altered host range. Based on the host range screening results, the phages differed by broadness of the host ranges and the infection efficiencies. The screening results revealed that ɸEBHT infected 40 % of the tested strains when mEBHT was able to infect 28 % of the strains. In conclusion, the chosen host strain for phage propagation can lead to an altered host range of the phage. To determine whether the M42 class metallopeptidases are involved in changing host range of phage vB_SauP_EBHT, further studies would be required.

Description

Supervisor

Scheller, Silvan

Thesis advisor

Kiljunen, Saija

Keywords

bacteriophage, Staphylococcus aureus, MRSA, phage-host interactions, phage host range, proteomics

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https://urn.fi/URN:NBN:fi:aalto-202106207530

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[dipl] Kemian tekniikan korkeakoulu / CHEM