Challenging food microbiology from a molecular perspective

This lecture addresses molecular approaches to two key challenges in food microbiology: bacterial detection and control. The author reviews contributions of bacterial bioluminescence, particularly the lux operon from Photobacterium fischeri cloned in 1983, as a dual-function reporter system. Bioluminescent bacteria engineered to express lux genes enable rapid, real-time detection of cellular viability and antimicrobial effects, as light production depends on functional intracellular biochemistry (FMNH2 levels). The technique allows visualization of bacterial injury and recovery from stresses like heat and freezing with sensitivity comparable to 18-24 hour viable plate counts. Beyond constitutive bioluminescence, lux-engineered bacteriophages offer pathogen-specific detection, particularly for enteric bacteria and Listeria. Novel approaches include phage amplification assays exploiting rapid phage replication, bacteriophage endolysins for genus-specific bacterial lysis to enhance ATP assays, and universal PCR primers targeting conserved cold shock genes (cspA homologues) to detect any bacterial contaminant and discriminate psychrotrophic Bacillus species. These molecular tools address the fundamental limitation of classical plate counts—their time requirement—enabling rapid HACCP monitoring and safer food production.

Key findings

• Bioluminescent bacteria with cloned lux genes provide real-time detection of bacterial viability and antimicrobial agent efficacy, with results comparable to viable plate counts in minutes rather than 18-24 hours
• Lux-engineered bacteriophages enable rapid, pathogen-specific bacterial detection within 1 hour without enrichment, particularly for enteric indicator organisms and Listeria species
• Bacteriophage endolysins with genus-specific activity can selectively lyse target bacteria within minutes to improve ATP-based detection assays
• Universal PCR primers targeting cold shock gene homologues (cspA) can detect any bacterial contaminant and differentiate psychrotrophic from mesophilic Bacillus species