Degradation of N -Acyl- l -Homoserine Lactones by Bacillus cereus in Culture Media and Pork Extract

Abstract

Degradation of the quorum-sensing signal molecule N-acyl-L-homoserine lactone (AHL) in cocultures was verified with Bacillus cereus and Yersinia enterocolitica in culture medium and in pork extract. Results showed evidence of microbial interaction when the AHL-degrading bacterium and AHL-producing bacterium were cocultured in a food-simulating condition.The term "quorum sensing" has been proposed to describe the ability of bacteria to monitor their own population density and modulate gene expression accordingly (17). This communication system uses chemical signal molecules called autoinducers, which are produced and released by the bacterial cell. Intracellular response occurs when the concentration of autoinducers rises above the minimum concentration threshold. Some gram-negative food-associated bacteria can produce Nacyl-L-homoserine lactones (AHLs) as signal molecules. Examples include Aeromonas hydrophila, Pseudomonas aeruginosa, and Yersinia enterocolitica (11,12,20,24,26). In these bacteria, a relationship between AHL production and expression of some mechanisms such as biofilm formation, motility, and exoprotease production has been described previously (2,15,17,25).The signal molecule AHL is the key factor in this bacterial communication process. Degradation of the molecule prevents its sufficient accumulation in the immediate vicinity of the bacterial cell and will consequently lead to a disruption of the communication system. In several fields, blocking of quorum sensing by degradation of AHL molecules has been proposed as a promising alternative to diminish bacterial virulence (4,5,6,9,18). In food systems quorum sensing may have a role in food spoilage, the growth and/or toxin production of pathogens present in food, biofilm formation, bacteriocin production, virulence responses, etc. A possible role of some bacteria in biological degradation of AHLs has been suggested (5,6,7,10,13,14,19,22). Most of the reports on quorum-sensing degradation have been focused on plant pathogens (5, 6, 18). Although it is well known that the lactonase gene is widely spread among certain strains of food-borne Bacillus spp., no actual data are available on the interaction of mixed populations of AHL-producing and AHL-degrading bacteria in food-simulating conditions.The aim of the present study was to screen for the AHLdegrading capacity of Bacillus cereus and some other current and former Bacillus spp. and to establish whether degradation capacity is noted in the coculture environment. The AHLdegrading capacity of Bacillus sp. strains was evaluated with both synthetic AHL molecules and AHL produced by Y. enterocolitica. The AHL degradation ability was further assessed in one B. cereus strain inoculated in coculture with a Y. enterocolitica strain in culture medium and pork extract. Screening of synthetic-AHL degradation at 30°C. Twenty B. cereus and 29 other current and former Bacillus isolates were screened for their AHL degradation capacities. N-Hexanoyl-L-homoserine lactone (C 6 -HSL) (Biochemika Sigma-Aldrich) and ...

The Paradox of Mixed‐Species Biofilms in the Context of Food Safety

“…In mixed‐species biofilms, bacteria communicate with each other and inhibit one another by producing antibacterial, antiadhesive compounds, jamming of QS, and induction of biofilms dispersal (Rendueles and Ghigo ). The AHL degrader Bacillus cereus showed degradation of Yersinia enterocolitica on pork meat (Medina‐Martínez and others ). Recently, acylated homoserine lactones‐containing cultures from chicken breast muscle broth were found to inhibit the biofilms formation of P. aeruginosa , indicating potential jamming of QS and reduction of biofilms, which could, in turn, contribute to food safety (Zhang and others ).…”

Improvement of bioelectrochemical property and energy recovery by acylhomoserine lactones (AHLs) in microbial electrolysis cells (MECs)

“…Besides the freely diffusion of shorter chain through the cell membrane, the possible reason is P. aeruginosa and Pseudomonas like species were able to degrade long chain AHLs but not short chain AHLs as the sole carbon source [20], though it was still not clear the correspondence between molar growth yields and AHL acyl side chain lengths. Degradation of the molecule prevents its sufficient accumulation in the anodic biofilm communities and will consequently lead to a disruption of the stimulated communication system [30]. It seem that AHLs addition likely reduced the start-up time of the electron transport (Fig.…”

Multifaceted Interfaces of Bacterial Competition

“…Secreted enzymes that confer antibiotic resistance have a clear competitive benefit (40,42). Additionally, bacteria benefit by interfering with the development of their competitors, e.g., using enzymes to degrade signaling mol- ecules, like acyl homoserine lactones (48)(49)(50)(51). However, surprisingly little is known about how bacteria use secreted enzymes to kill or inhibit their competitors.…”