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Schamp CN, Dhowlaghar N, Hudson LK, Bryan DW, Zhong Q, Fozo EM, Gaballa A, Wiedmann M, Denes TG. Selection of mutant Listeria phages under food-relevant conditions can enhance application potential. Appl Environ Microbiol 2023; 89:e0100723. [PMID: 37800961 PMCID: PMC10617581 DOI: 10.1128/aem.01007-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 08/04/2023] [Indexed: 10/07/2023] Open
Abstract
Bacteriophages are viruses that infect and kill bacteria. Currently, phage products are available for the control of the pathogen Listeria monocytogenes in food products in the United States. In this study, we explore whether experimental evolution can be used to generate phages with improved abilities to function under specific food-relevant conditions. Ultra-pasteurized oat and whole milk were chosen as test matrices as they represent different food groups, yet have similar physical traits and macronutrient composition. We showed that (i) wild-type phage LP-125 infection kinetics are different in the two matrices and (ii) LP-125 has a significantly higher burst size in oat milk. From this, we attempted to evolve LP-125 to have improved infection kinetics in whole milk. Ancestral LP-125 was passaged through 10 rounds of amplification in milk conditions. Plaque-purified DNA samples from milk-selected phages were isolated and sequenced, and mutations present in the isolated phages were identified. We found two nonsynonymous substitutions in LP125_108 and LP125_112 genes, which encode putative baseplate-associated glycerophosphoryl diester phosphodiesterase and baseplate protein, respectively. Protein structural modeling showed that the substituted amino acids in the mutant phages are predicted to localize to surface-exposed helices on the corresponding structures, which might affect the surface charge of proteins and their interaction with the bacterial cell. The phage containing the LP125_112 mutation adsorbed significantly faster than the ancestral phage in both oat and whole milk. Follow-up experiments suggest that fat content may be a key factor for the expression of the phenotype of this mutation. IMPORTANCE Bacteriophages are one of the tools available to control the foodborne pathogen, Listeria monocytogenes. Phage products must work under a broad range of food conditions to be an effective control for L. monocytogenes. Here, we show that the experimental evolution of phages can be used to generate new phages with phenotypes useful under specific conditions. We used this approach to select for a mutant phage that more efficiently binds to L. monocytogenes that is grown in whole milk and oat milk. We show that the fat content of these milks is necessary for the expression of this phenotype. Our findings show that experimental evolution can be used to select for improved phages with better performance under specific conditions. This approach has the potential to support the development of condition-specific phage-based biocontrols in the food industry.
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Affiliation(s)
- Claire N. Schamp
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
| | - Nitin Dhowlaghar
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
| | - Lauren K. Hudson
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
| | - Daniel W. Bryan
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
| | - Qixin Zhong
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
| | - Elizabeth M. Fozo
- Department of Microbiology, The University of Tennessee, Knoxville, Tennessee, USA
| | - Ahmed Gaballa
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Thomas G. Denes
- Department of Food Science, The University of Tennessee, Knoxville, Tennessee, USA
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Ledormand P, Desmasures N, Bernay B, Goux D, Rué O, Midoux C, Monnet C, Dalmasso M. Molecular approaches to uncover phage-lactic acid bacteria interactions in a model community simulating fermented beverages. Food Microbiol 2022; 107:104069. [DOI: 10.1016/j.fm.2022.104069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 04/12/2022] [Accepted: 06/06/2022] [Indexed: 11/24/2022]
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