Growth, encystment and survival of Acanthamoeba castellanii grazing on different bacteria

Abstract

Free-living amoebae of the genus Acanthamoeba are widely distributed in soil and water collections, where trophozoites (vegetative, multiplicative stages) feed mainly by phagocytosis and thus control bacterial populations in the environment. Here, we examined the growth, encystment and survival of Acanthamoeba castellanii receiving different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterobacter cloacae, Bacillus subtilis, Bacillus megaterium, Micrococcus luteus, and Staphylococcus aureus) in nonnutrient saline. All bacteria assayed induced a dose-dependent proliferative response, in most cases maximized with a bacterial dose of 1 x 10(9) mL(-1); except for M. luteus, trophozoites grew better with viable than with heat-killed bacteria. In addition, Acanthamoeba growth was improved by adding bacteria on alternate days. Single-dose experiments indicated a temporal association between the growth of trophozoite and bacterial consumption, and higher consumption of M. luteus, E. coli and P. aeruginosa, bacterial species that allowed the highest trophozoite yields. Long-term Acanthamoeba-bacteria incubation revealed that encystment was significantly delayed by almost all the bacteria assayed (including S. aureus, which elicited a poor growth response) and that the presence of bacteria markedly increased cyst yield; final cyst recovery clearly depended on both the dose and the type of the bacterium given, being much higher with E. coli, M. luteus and P. aeruginosa.

Allovahlkampfia spelaea is a Potential Environmental Host for Pathogenic Bacteria

“…The predation/survival/intracellular replication data for our bacteria differed in some instances from some work on bacteria and FLA interactions already published [6,51] that revealed a dose-dependent proliferative response of FLA when co-incubated with bacteria like E. coli, Staph. aureus, C cloacae, and Ps.…”

“…Most FLA genera are characterized by a biphasic life cycle consisting of a vegetative trophozoite stage and a physiologically static cyst stage [2]. Cysts are highly resistant and remain viable (and infective) for several years which facilitates spreading and colonization of new ecological niches [6]. On the other hand, bacteria have developed several antipredator strategies including cell size reduction, modified cell morphology, modification of cell wall characteristics, high-speed motility, biofilm or microcolony formation, and production of exopolymers or toxins [7].…”

Determinants that govern the recognition and uptake ofEscherichia coliO157 : H7 byAcanthamoeba castellanii

“…Acanthamoeba castellanii is a free‐living amoeba that plays an important role in controlling bacterial populations in a variety of terrestrial environments, and it serves as a prototype for the study of protozoa–bacteria predator–prey interactions (de Moraes and Alfieri, , Johnke et al ., ). In its natural habitat, A. castellanii depends entirely on bacterial phagocytosis to satisfy its nutritional requirements (Anscombe and Singh, ).…”

“…Previous studies provided preliminary evidence that bacterial phagocytosis is inhibited by exogenously added mannose (Alsam et al ., ), a finding which suggests that A. castellanii mannose‐binding protein (aMBP) may play a role in bacterial recognition and/or phagocytosis. Bacterial uptake by A. castellanii is influenced by serotype (de Moraes and Alfieri, , Huws et al ., ). This observation suggests that LPS, a component of the cell surface of Gram‐negative bacteria, plays a role in the recognition of bacteria by amoebae.…”

Cellular, Biochemical, and Molecular Changes during Encystment of Free-Living Amoebae

“…Also, the presence of intracellular bacteria could interfere with encystment (14). Francisella tularensis type A strains cause the rapid encystment of Acanthamoeba castellanii (21).…”