Woods and Thomson studied generalized transduction in Achromobacter using four related bacteriophages (α phages) on a halotolerant, collagenolytic strain. Six auxotrophic markers were successfully transduced, and abortive transduction was also observed. Unusually, the transductants were unstable and segregated auxotrophic markers at rates of approximately 3.6 × 10⁻⁶ per cell per generation, characteristic of transduction by lysogeny rather than typical integration. The recipient Achromobacter strain proved to be a cryptic lysogen for phage α3. Purified transductant clones exhibited diverse phage characteristics: some remained sensitive or resistant to the original phage, while others spontaneously released phage with altered host ranges differing from the α phage used in transduction. Some initially resistant transductants became semi-sensitive after repeated cloning. The researchers propose that generalized transducing particles contain both bacterial and varying amounts of phage DNA, and complementation between the resident cryptic prophage and genes in the transducing DNA explains the observed phage diversity and recombinant phage release.

Key findings

• Achromobacter transductants produced by four α phages were unstable, segregating at approximately 3.6 × 10⁻⁶ per cell per generation, characteristic of lysogenic rather than integrative transduction
• Purified transductant clones spontaneously released phage variants with host ranges different from the original α phage, with some phage released from α-resistant strains
• The recipient strain is a cryptic lysogen for phage α3 with defective immunity and excision systems, enabling complementation between the cryptic prophage and transducing DNA
• Transductants showed eight distinct phage characteristic types, including strains that became semi-sensitive to the original phage after multiple clonings
• This represents the first demonstration of generalized transduction by lysogenization for multiple different markers rather than specific gene sets