Lack of induced mutagenesis in E. coli or human lymphoblast cell line upon long-term sub-culturing in medium from irradiated meat

Purpose: Current study was aimed to enhance the confidence of consumers as well as entrepreneurs towards food irradiation program.

Materials and methods: In this work, safety of high dose (25?kGy) irradiated meat samples (HDIMS) was ascertained by scoring mutation frequency through a long-term sub-culturing study in Escherichia coli MG1655 cells (ATCC 700926) up to 1500 generations (at 1%), 250 generations (at 5% and 10%) and human lymphoblast thymidine kinase heterozygote (TK6) cell line (ATCC CRL-8015) [at two gene loci, tk^?/+ (thymidine kinase) and hprt⁺ (Hypoxanthine Phosphoribosyltransferase)] up to 156 generations using goat meat sample. Also these samples were assayed at further radiation doses of 10, 45 and 70?kGy at 2% concentration (in cell line), and 1% (in E. coli). Study was also performed with other meat samples such as chicken, fishes (pomfret and rohu) and shrimps by carrying out limited long-term sub-culturing trials in human lymphoblast cell line. Mutation analysis was also carried out using a novel DPAR (Differential loss of Plasmid Antibiotic Resistance) assay followed by sequencing of tc^R (tetracycline resistance) gene of pBR322 plasmid isolated from E. coli cells grown for 1500 generations on HDIMS medium and RAPD (Random Amplified Polymorphic DNA) analysis of the genome.

Results and conclusion: None of the assays exhibited any induced mutation when analyzed at regular time intervals. RAPD analysis also did not indicate any change in its nucleotide sequence, ruling out the occurrence of any silent mutation. Thus, the present findings report absence of mutagenic effect of high dose irradiated meat samples.