Do Protozoa Control the Elimination of Vibrio choleraein Brackish Water?

Abstract

Do Protozoa Control the Elimination of Vibrio choleraein Brackish Water?key words: Cyclidium glaucoma, ciliate feeding selectivity, toxin producing bacteria AbstractElimination of inoculated Vibrio cholerae (≥10 7 cells ml -1) within a brackish water bacteria assemblage (Mecoacán Lagoon, State of Tabasco, Mexico) was studied in laboratory microcosms with filtrationfractionated water. Feeding of a ciliate, Cyclidium glaucoma was evaluated using fluorescently labelled V. cholerae O1. Even though V. cholerae was not exploited as the major food source, ciliates were able to eliminate it efficiently. An addition of chitin directly supported the growth of bacteria, although not so much of V. cholerae, and indirectly the growth of the protistan assemblage. Generally, the changes in a bacterial assemblage structure were the most important in V. cholerae elimination. IntroductionThe ecological position of human-pathogenic bacteria such as Vibrio cholerae O1 within the aquatic microbial food web has not been studied frequently, however, such studies led to the Viable But Nonculturable Bacteria (VBNC) concept (reviewed in COLWELL, 2000). This theoretical concept is being now changed (compare, BOGOSIAN et al., 2000), but one must accept that it has given us more realistic data on the pathogen distribution in the environment by comparing the use of direct counting methods, e.g. immunofluorescence microscopy, with cultivation methods (XU et al., 1984;BRAYTON et al., 1987;HUQ et al., 1990;TAMPLIN et al., 1990;CORTÉS et al., 2000). It was proven that vibrios could participate directly in the annual plankton -benthic cycle (KANEKO and COLWELL, 1975;TAMPLIN et al., 1990;GUTHRIE and COFIE, 1991;VANOY et al., 1992), entering the microbial loop within a plankton food web (sensu AZAM et al., 1983) along with other bacteria and bacterivorous microorganisms such as protozoa (BERK et al., 1976;MACEK et al., 1997).From the point of view of interactions between bacteria and protozoa, mechanical predation selectivity and/or surface properties of the prey have been suggested as the major mechanism controlling ciliate -bacteria interactions (FENCHEL, 1986;SANDERS, 1988; GON-ZÁLEZ et al, 1990). The ability of ciliates to discriminate between particles is limited to shape, volume and cell wall properties. Frequently, protozoa select larger prey, such as dividing cells, even on the edible size threshold which is of great importance in the control of bacterial assemblages (SHERR et al., 1992;ŠIMEK et al., 1994). Conversely, ingestion of a non-suitable prey affects ciliate growth rate and generally, population development.Internat. Rev. Hydrobiol.

Environmental reservoirs and mechanisms of persistence of Vibrio cholerae

“…The long-term persistence and seasonal accumulation of V. cholerae is dependent on how it responds to this stress. Microcosm studies of natural bacterioplankton communities from the Gulf of Mexico showed that ciliates and heterotrophic nanoflagellates (HNFs) efficiently eliminate V. cholerae from environmental water samples ( Martínez Pérez et al, 2004 ). In addition, ciliates as well as flagellates can feed on V. cholerae , with grazing rates of up to 600–2,000 bacteria cell -1 h -1 ( Macek et al, 1997 ).…”

Pyomelanin produced by Vibrio cholerae confers resistance to predation by Acanthamoeba castellanii

“…( 2016 ) showed that V. cholerae can grow inside A. castellanii. A study using laboratory microcosms of natural bacterioplankton communities from the Gulf of Mexico showed elimination of V. cholerae by ciliates and heterotrophic nanoflagellates (Martínez Pérez, Macek and Castro Galván 2004 ). In contrast, when V. cholerae biofilms were exposed to predation by flagellates, there was little effect on biofilm biomass, indicating that biofilms are protected from predation (Matz et al.…”

The role of wetland microinvertebrates in spreading human diseases

“…Among the microinvertebrate communities an increase in protozoan ciliates and heterotrophic nanoflagellates (HNFs) may regulate pathogenic microbial populations. Microcosm studies have shown the capacity of these microinvertebrates to eliminate V. cholerae through their grazing activities (Martı ´nez Pe ´rez et al 2004). Various ciliated protozoa can limit many bacterial populations by their predatory activities, e.g., Paramecium caudatum can rapidly ingest the Cryptosporidium oocysts (Stott et al 2001).…”