Abstract
In the natural environments microorganisms coexist in communities as biofilms. Since foodborne pathogens have varying abilities to form biofilms, investigation of bacterial interactions in biofilm formation may enhance our understanding of the persistence of these foodborne pathogens in the environment. Thus the objective of this study was to investigate the interactions between Listeria monocytogenes and Ralstonia insidiosa in dual species biofilms. Biofilm development after 24 h was measured using crystal violet in 96-well microtiter plate. Scanning electron microscopy and cell enumeration were employed after growth on stainless steel coupons. When compared with their single species counterparts, the dual species biofilms exhibited a significant increase in biofilm biomass. The number of L. monocytogenes in co-culture biofilms on stainless steel also increased significantly. However, there was no effect on the biofilm formation of L. monocytogenes when cultured with R. insidiosa separated by a semi-permeable membrane-linked compartment or cultured in R. insidiosa cell-free supernatant, indicating that direct cell-cell contact is critical for this interaction.
Highlights
Biofilms are living microbial communities attached to a solid surface or flowing in aqueous systems
There was no effect on the biofilm formation of L. monocytogenes when cultured with R. insidiosa separated by a semi-permeable membrane-linked compartment or cultured in R. insidiosa cell-free supernatant, indicating that direct cell-cell contact is critical for this interaction
This was consistent with observations in our previous study [18] which showed that all L. monocytogenes strains tested were weak in biofilm formation in monocultures
Summary
Biofilms are living microbial communities attached to a solid surface or flowing in aqueous systems. Multispecies biofilms are the predominant forms of presence for microorganisms in the natural environments, and play important roles in the survival and persistence of microorganisms, including foodborne pathogens [3]. In such microbial communities, microorganisms interact in various ways that can be described as competition, antagonism, or synergism [4]. Listeria monocytogenes is a Gram-positive foodborne pathogen that is responsible for serious infections in immunocompromised individuals and pregnant women [5] It is frequently found in various food processing environments and has been isolated from a range of food products including meat, milk, cheese, and vegetables [6,7,8,9]. The biofilm is still considered in early stage, the interspecies interactions can be readily discerned
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