Gene transfer between bacteria within digestive vacuoles of protozoa

Abstract

The occurrence of horizontal gene transfer between bacteria within digestive vacuoles and faecal pellets of the protozoan Tetrahymena pyriformis was investigated. More than 90% of the egested faecal pellets of T. pyriformis, added as predator to a suspension of Escherichia coli, contained viable bacteria. In a mixed population, containing donor (plasmid RP4) and recipient E. coli cells, the presence of T. pyriformis increased conjugational gene transfer by three orders of magnitude. Since the protozoa formed an average of 12–13 digestive vacuoles per cell, each protozoan had statistically egested one or more transconjugants. Thus, we show for the first time that digestive vacuoles of free‐living protozoa appear to be an important ecological micro‐niche, where gene transfer by conjugation (or retromobilisation) will be favoured. So far, digestive vacuoles have been ignored in genetic and ecological studies. This micro‐biotope provides a selective pressure which might enhance the acquisition of virulence genes in cases of mutual interactions between genetically modified micro‐organisms and wild‐type pathogens. This finding is important for biosafety considerations.

Microbial horizontal gene transfer and the DNA release from transgenic crop plants

“…In the future more environmental compartments where gene transfer occurs will be identified. It is conceivable that Bräutigam et al, 1997;Davison, 1999;Day, 1998;Kay et al, 2002;Li et al, 2001;Lorenz and Wackernagel, 1994;Mercer et al, 2001;Schlimme et al, 1997;Stotzky et al, 1990. with improved experimental techniques gene transfer will be confirmed in very specific habitats where detection efforts have so far failed. For instance, it may be possible to identify natural transformation in the gastrointestinal tract, a habitat known to be rich in DNA degrading activity and probably not optimal for the development of DNA uptake competence of bacteria, but where high concentrations of bacteria are exposed to a variety of DNA molecules ingested with the food (Jonas et al, 2001).…”

The role of free-living protozoa in protecting foodborne pathogens

“…In addition to gene transfers in genomes, the spread of antibiotic resistance is of particular interest. Plasmids encoding for kanamycin resistance and extended-spectrum β -lactamases were exchanged between two E. coli strains in food vacuoles and fecal pellets of T. pyriformis (Oguri et al ., 2011, Schlimme et al ., 1997. Exchange of plasmids encoding ceftriaxone resistance from Klebsiella to Salmonella was mediated in rumen protozoa of calves, sheep and goats (McCuddin et al ., 2006 ).…”

Model-based characterization of endogenous maintenance, cell death and predation processes of activated sludge in sequencing batch reactors

“…It is unreasonable in real cases and should be modified. In this work, the active microorganisms form the prey for protozoa and metazoa, which excrete faecal pellets containing (f I ) inert COD (Schlimme et al, 1997;Moussa et al, 2005). Predators grow aerobically on the degradable fraction (1 Àf I ) of the heterotrophs (Moussa et al, 2005).…”

“…Furthermore, in the laboratory-scale SBR of this work, different types of higher organisms (protozoa and metazoa) were microscopically observed, suggesting the existence of predation in this sludge system. The bacteria form the prey for protozoa and metazoa, which excrete faecal pellets that contain inert COD (Schlimme et al, 1997).…”