Quorum Sensing and Spoilage Potential of Psychrotrophic Enterobacteriaceae Isolated from Milk

Abstract

The 16S rDNA of six psychrotrophic Enterobacteriaceae isolated from cold raw milk were sequenced and the isolate 039 was identified asPantoeasp., isolates 059, 068, and 071 were identified asHafnia alvei, 067 was identified asEnterobactersp., and 099 was identified asAeromonas hydrophila. They presented different spoilage potentials in milk withA. hydrophila099 being the most deteriorative. OnlyPantoeasp. 039 was not able to induce the quorum sensing monitor strains of acyl homoserine lactones (AHLs). ThehalIgene, which encodes the AHL synthase inH. alvei, was identified in the isolates 059, 067, 068, and 071. After initial sequencing characterization and cloning, this gene showed its function by the heterologous synthesis of N-hexanoyl-DL-homoserine lactone and N-3-oxohexanoyl-L-homoserine lactone inEscherichia coli. In addition to producing AHLs,A. hydrophila099 produced AI-2 in higher level than the assay’s positive controlVibrio harveyiBB120. Therefore, Enterobacteriaceae strains isolated from cooled raw milk produce a rich array of signaling molecules that may influence bacterial traits in the milk environment.