Journal article
Involvement of bacterial quorum-sensing signals in spoilage of bean sprouts
National Institute of Aquatic Resources, Technical University of Denmark1
Division of Microbiology and Risk Assessment, National Food Institute, Technical University of Denmark2
National Food Institute, Technical University of Denmark3
Center for Microbial Biotechnology, Department of Systems Biology, Technical University of Denmark4
Department of Systems Biology, Technical University of Denmark5
Section for Aquatic Microbiology and Seafood Hygiene, National Institute of Aquatic Resources, Technical University of Denmark6
Bacterial communication signals, acylated homoserine lactones (AHLs), were extracted from samples of commercial bean sprouts undergoing soft-rot spoilage. Bean sprouts produced in the laboratory did not undergo soft-rot spoilage and did not contain AHLs or AHL-producing bacteria, although the bacterial population reached levels similar to those in the commercial sprouts, 10(8) to 10(9) CFU/g.
AHL-producing bacteria (Enterobacteriaceae and pseudomonads) were isolated from commercial sprouts, and strains that were both proteolytic and pectinolytic were capable of causing soft-rot spoilage in bean sprouts. Thin-layer chromatography and liquid chromatography-high-resolution mass spectrometry revealed the presence of N-3-oxo-hexanoyl-l-homoserine lactone in spoiled bean sprouts and in extracts from pure cultures of bacteria.
During normal spoilage, the pH of the sprouts increased due to proteolytic activity, and the higher pH probably facilitated the activity of pectate lyase. The AHL synthetase gene (I gene) from a spoilage Pectobacterium was cloned, sequenced, and inactivated in the parent strain. The predicted amino acid sequence showed 97% homology to HslI and CarI in Erwinia carotovora.
Spoilage of laboratory bean sprouts inoculated with the AHL-negative mutant was delayed compared to sprouts inoculated with the wild type, and the AHL-negative mutant did not cause the pH to rise. Compared to the wild-type strain, the AHL-negative mutant had significantly reduced protease and pectinase activities and was negative in an iron chelation (siderophore) assay.
This is the first study demonstrating AHL regulation of iron chelation in Enterobacteriaceae. The present study clearly demonstrates that the bacterial spoilage of some food products is influenced by quorum-sensing-regulated phenotypes, and understanding these processes may be useful in the development of novel food preservation additives that specifically block the quorum-sensing systems.
Language: | English |
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Publisher: | American Society for Microbiology |
Year: | 2005 |
Pages: | 3321-3330 |
ISSN: | 10985336 and 00992240 |
Types: | Journal article |
DOI: | 10.1128/AEM.71.6.3321-3330.2005 |
ORCIDs: | 0000-0003-4238-4658 , Nielsen, Kristian Fog and Gram, Lone |
4-Butyrolactone Bacterial Proteins Colony Count, Microbial DNA, Bacterial Enterobacteriaceae Fabaceae Gene Expression Regulation, Bacterial Gram-Negative Bacteria Molecular Sequence Data Mutation Phenotype Pseudomonas RNA, Ribosomal, 16S Sequence Analysis, DNA Signal Transduction Vibrionaceae homoserine lactone