Biofilm formation and cell-to-cell signalling in Gram-negative bacteria isolated from a food processing environment.
OBJECTIVE
To investigate the biofilm-forming capacity and the production of quorum signals in Gram-negative bacteria isolated from a food production environment, and the possible correlation between both phenotypes.


RESULTS
Sixty-eight Gram-negative bacteria were isolated from equipment and working surfaces in a raw vegetable processing line, and tested for biofilm-forming capacity using an in vitro microplate assay. All isolates showed significantly higher biofilm-forming capacity than Escherichia coli laboratory strain DH5alpha, which was included as a negative control, and differed up to 56-fold in relative biofilm-forming capacity. Various assays based on reporter bacteria were used to detect quorum signals produced by the isolates. Twenty-six isolates produced autoinducer-2, five isolates produced N-acyl-homoserine lactones (AHLs), and none produced the Pseudomonas quinolone signal.


CONCLUSIONS
No correlation was found between in vitro biofilm-forming capacity and production of quorum signalling molecules among the 68 strains isolated from the raw vegetable processing line.


CONCLUSIONS
Several recent studies have shown a role of AHL-based quorum sensing in biofilm formation of specific Gram-negative bacterial strains. The current work shows that production of AHL and other quorum signals is not widespread in Gram-negative isolates from a raw vegetable processing line, and is not a general requirement for biofilm formation, at least in vitro.
Van Houdt
R
R
Laboratory of Food Microbiology, Katholieke Universiteit Leuven, Leuven, Belgium.
Aertsen
A
A
Jansen
A
A
Quintana
A L
AL
Michiels
C W
CW
D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000096:biosynthesis; D018441:Biofilms / Q000254:growth & development*; D004866:Equipment Contamination; D005511:Food Handling; D005516:Food Microbiology; D006090:Gram-Negative Bacteria / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D006714:Homoserine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D006801:Humans; D007783:Lactones; D015398:Signal Transduction; D014675:Vegetables / Q000382:microbiology
D007783:Lactones; C091088:N-octanoylhomoserine lactone; C088386:homoserine lactone; D006714:Homoserine; D015107:4-Butyrolactone