Darvishali MH, Fadaie M, Khanahmad H. The enhancement of M13 phage titration by optimizing the origin of replication.
Res Pharm Sci 2024;
19:338-346. [PMID:
39035815 PMCID:
PMC11257199 DOI:
10.4103/rps.rps_14_24]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/07/2024] [Accepted: 04/14/2024] [Indexed: 07/23/2024] Open
Abstract
Background and purpose
M13KO7, a modified M13 phage variant, carries the p15A replication origin and Tn903 kanamycin resistance gene. This study aimed to optimize M13KO7's replication by substituting the p15A origin with the higher-copy pMB1 origin (500-700 copy numbers).
Experimental approach
A 6431-nucleotide fragment from the M13KO7 plasmid lacking the p15A replication origin and kanamycin resistance gene was amplified using a long polymerase chain reaction (PCR). The modified M13AMB1 plasmid was created by adding adenine to the 3' ends of this fragment and ligating it to the pMB1-containing fragment using T/A cloning. Afterward, to prepare the phage, pM13AMB1 was transformed into E. coli TG1 bacteria, and then, using the PEG-NaCl precipitation, the modified phage was propagated. The modified phage titer was determined utilizing the serial dilution and the qPCR methods, compared with the M13KO7 phage.
Findings/Results
The results showed that in the serial dilution method, the titers of modified phage and M13KO7 phage were 4.8 × 1014 and 7 × 1012 pfu/mL, respectively. Besides, the phage titer calculated by the qPCR method for the modified phage was equal to 1.3 × 109 pfu/mL, whereas it was 4.08 × 108 pfu/mL for the M13KO7 phage.
Conclusion and implications
This study provides evidence that replication origin replacement led to a significant increase in phage titers. It highlights the importance of replication optimization for molecular biology applications.
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