Agrobacterium vitis strains, their tumor-inducing (pTi) and tartrate utilization (pTr) plasmid transconjugants and grapevine tumors were analyzed for the presence of N-acyl-homoserine lactones (AHLs). All wild-type A. vitis strains produced long-chain signals. PCR analysis of the A. vitis long-chain AHL synthase gene, avsI, showed the predicted amplicon. Agrobacterium tumefaciens UBAPF2 harboring various A. vitis pTi plasmids produced N-(3-oxo-octanoyl)-l-homoserine lactone encoded also by pTis of A. tumefaciens. UBAPF2 transconjugants carrying pTrs except for pTrTm4 and pTrAB3, also produced an AHL. UBAPF2 transconjugants carrying pTrAT6, pTrAB4 and pTrRr4 or pTiNi1 produced two additional AHLs not observed in the corresponding wild-type strains. We also provide evidence for in situ production of AHLs in grapevine crown gall tumors of greenhouse and field origin.

Hen egg yolk contains significant antibacterial activity. We show that this activity is associated with the release of free fatty acids. Chloroform-methanol extraction on egg yolk demonstrated the activity to be lipoprotein-bound before enzymatic digestion and associated with the lipid-soluble chloroform phase afterward. Acetone extraction yielded a fraction of egg yolk, which was 97% triglyceride and highly antibacterial to Streptococcus mutans when treated with pancreatin. The fatty acid profile of the extract reflected the proportions known to exist in egg yolk. Both oleic and linoleic acid were found to inhibit growth of S. mutans. These findings highlight a previously unreported potential of hen egg yolk in future healthcare applications.