Differential effects of magnesium, calcium, and sodium on Listeria monocytogenes biofilm formation

Abstract

Listeria monocytogenes is a gram-positive foodborne pathogen that causes outbreaks of listeriosis associated with a diverse range of foods. L. monocytogenes forms biofilms as a strategy to enhance its survival in the environment. These biofilms then provide a source of contamination in processing plant environments. Cations like magnesium, calcium, and sodium are commonly found in the environment and are important to bacteria to maintain their homeostasis. It is, therefore, valuable to understand the relationship between these cations and biofilm formation. In this study, four isolates of L. monocytogenes from seafood processing environments were used to investigate the influence of magnesium, calcium, and sodium (1, 10, and 50 mM) on biofilms. The isolates selected were defined as being either a low biofilm former, a high biofilm former, an outbreak isolate, and a persistent isolate from the seafood industry. The study showed that the divalent cations magnesium and calcium increased biofilm formation compared with the monovalent cation, sodium. Fifty mM concentrations of the divalent cations significantly enhanced biofilm formation. The cations did not have a significant effect on the initial stages of biofilm formation but appeared to influence the later stages of biofilm development.

Keywords:

• Listeria monocytogenes
• biofilm
• magnesium
• calcium
• sodium

Acknowledgements

We thank Lindy Guo for help in statistical analysis. We would like to thank The New Zealand Institute for Plant and Food Research and the School of Food and Advanced Technology (Massey University), the School of Fundamental Sciences (Massey University) for their support. This research was funded through the Cawthron Safe New Zealand Seafood SSIF programme, contract CAWX1801, with the New Zealand Ministry of Business, Innovation and Employment.

Disclosure statement

The authors declare that there are no conflicts of interest and that the research does not involve human participants and/or animals.

Funding

This work was funded by the New Zealand Ministry of Business, Innovation and Employment under the Seafood Safety programme of the Cawthron Institute (CAWX0301).