Persistence of Enterococcus faecalis in aquatic environments via surface interactions with copepods

Area of Science:

• Environmental microbiology
• Bacterial survival strategies
• Water quality assessment

Background:

• Human pathogens and fecal indicators can survive in natural environments using strategies like adhesion and entering the viable but nonculturable (VBNC) state.
• Previous studies detected Enterococcus faecalis bound to plankton and in the VBNC state in lake and seawater.

Purpose of the Study:

• To investigate the role of copepods in the survival and adhesion of Enterococcus faecalis.
• To determine if adhesion to copepods influences the transition to the VBNC state.
• To identify bacterial components involved in copepod adhesion.

Main Methods:

• In vitro adhesion assays of E. faecalis to copepods.
• Monitoring the entry into the VBNC state under different conditions.
• Assessing adhesion of VBNC cells to copepods and chitin.
• Sugar competition experiments (GlcNAc, D-mannose) to study adhesion mechanisms.
• Identifying bacterial cell wall proteins and lipoteichoic acid involved in chitin binding.

Main Results:

• Adhesion to copepods accelerated the entry of E. faecalis into the VBNC state compared to planktonic bacteria.
• VBNC E. faecalis cells retained reduced adhesive properties to copepods and chitin.
• GlcNAc interfered with adhesion to both copepods and chitin, while D-mannose only affected copepod adhesion.
• Specific enterococcal cell wall proteins and lipoteichoic acid were found to bind chitin.

Conclusions:

• Copepods can act as an environmental reservoir for enterococci, including those in the VBNC state.
• The findings suggest current microbial detection protocols for environmental water quality may need revision to account for copepod-associated bacteria.