Interactions of some common pathogenic bacteria with Acanthamoeba polyphaga

Area of Science:

• Microbiology
• Ecology
• Cell Biology

Background:

• Protozoan grazing is a key pathway for bacterial biomass recycling in food webs.
• Increasing numbers of bacteria are known to evade protozoan digestion, leading to environmental proliferation.

Purpose of the Study:

• To investigate the interactions between specific pathogenic bacteria and the amoeba Acanthamoeba polyphaga.
• To determine bacterial survival and replication strategies within amoebal hosts.

Main Methods:

• Co-culture of six bacterial species (Bacillus cereus, Enterococcus faecalis, EPEC, Listeria monocytogenes, Salmonella Typhimurium, MSSA) with Acanthamoeba polyphaga.
• Quantification of extracellular bacterial numbers.
• Intracellular growth kinetics analysis.
• Fluorescent confocal microscopy.

Main Results:

• Acanthamoeba polyphaga preyed upon most tested bacteria, except Listeria monocytogenes and Staphylococcus aureus.
• Extracellular populations of L. monocytogenes and S. aureus increased when cultured with amoebae.
• S. aureus demonstrated intracellular survival and potential multiplication within A. polyphaga.
• L. monocytogenes did not replicate intracellularly but was sustained by amoebal metabolic waste.

Conclusions:

• Certain bacteria, notably Staphylococcus aureus, can evade protozoan predation and utilize amoebas as a survival niche.
• Listeria monocytogenes employs alternative strategies, such as utilizing host metabolic byproducts, to persist in amoebal co-cultures.
• These findings highlight bacterial adaptation mechanisms to protozoan grazing, impacting microbial ecology and environmental persistence.