Encystment of Vermamoeba (Hartmannella) vermiformis: Effects of environmental conditions and cell concentration.
Vermamoeba vermiformis is a free-living amoeba (FLA) which is widely distributed in the environment. It is known to colonize water systems and to be a reservoir of pathogenic bacteria, such as Legionella pneumophila. For these reasons the control of V. vermiformis represents an important health issue. However, FLA may be resistant to disinfection treatments due to the process of encystment. Thereby, it is important to better understand factors influencing this process. In this aim, we investigated the effect of temperature, pH, osmotic pressure and cell concentration on the encystment of two V. vermiformis strains. Encystment was quite fast, with a 100% encystment rate being observed after 9h of incubation. For the two strains, an optimal encystment was obtained at 25 and 37°C. Concerning pH and osmotic pressure, there were different effects on the encystment according to the tested strains. For the reference strain (ATCC 50237), the patterns of encystment were similar for pH comprised between 5 and 9 and for KCl concentrations ranging from 0.05 to 0.2 mol L(-1). For the environmental strain (172A) an optimal encystment was obtained for basic pH (8 and 9) and for a concentration in KCl of 0.1 mol L(-1). The results also clearly demonstrated that the encystment rate increased with cell concentration, suggesting that there is an inter-amoebal communication. The present study establish for the first time environmental conditions favoring encystment and would lay the foundations to better control the encystment of V. vermiformis.
Université de Poitiers, UMR CNRS 7267, Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, 1 rue G. Bonnet, 86073 Poitiers Cedex, France; Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France.
Emilie
E
Fouque
Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France.
Marie-Cécile
MC
Trouilhé
Enterome, 94-96 Avenue Ledru Rollin, 75011 Paris, France.
Vincent
V
Thomas
Scientific and Technical Center for Building, AQUASIM, 11 rue Henri Picherit, BP 82341, 44323 Nantes Cedex 3, France.
Philippe
P
Humeau
Université de Poitiers, UMR CNRS 7267, Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, 1 rue G. Bonnet, 86073 Poitiers Cedex, France. Electronic address: yann.hechard@univ-poitiers.fr.
Yann
Y
Héchard
D002452:Cell Count; D006249:Hartmannella / Q000166:cytology / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D033661:Oocysts / Q000502:physiology; D009997:Osmotic Pressure / Q000502:physiology; D013696:Temperature; D053058:Trophozoites / Q000166:cytology / Q000502:physiology; D014867:Water / Q000469:parasitology
D014867:Water
Amoeba; Cyst; Encystment; Hartmannella; Vermamoeba; Water