Interactions between Salmonella typhimurium and Acanthamoeba polyphaga , and Observation of a New Mode of Intracellular Growth within Contractile Vacuoles

Abstract

Acanthamoeba polyphaga feeding on Salmonella typhimurium in a simple model biofilm were observed by light microscopy and a detailed record of interactions kept by digital image capture and image analysis. A strain of S. typhimurium SL1344 carrying a fis: gfp reporter construct (pPDT105) was used to assess intracellular growth in A. polyphaga on non-nutrient agar (NNA) plates. Invasion of the contractile vacuole (CV) was observed at a frequency of 1:100-1000 acanthamoebae at 35 degrees C. The salmonellae contained in CVs illustrated significant up-regulation of fis relative to extracellular bacteria, indicating that they were in the early stages of logarithmic growth, and reached numbers of 100-200 cells per vacuole after 4 days. This is the first report of this mode of intracellular growth. Up-regulation of fis was also observed in a proportion of S. typhimurium cells contained within food vacuoles. Filamentation of S. typhimurium and E. coli cells was frequently observed in coculture with A. polyphaga on NNA plates, with bacterial cells reaching lengths of up to 500 microm after 10 days' incubation at 35 degrees C. A. polyphaga was also seen to mediate bacterial translocation over the agar surface; egested salmonellae subsequently formed microcolonies along amoebal tracks. This illustrated intracellular survival of a fraction of the S. typhimurium population. These phenomena suggest that protozoa such as A. polyhaga may play an important role in the ecology of S. typhimurium in soil and aquatic environments.

Co-occurrence of free-living protozoa and foodborne pathogens on dishcloths: Implications for food safety

“…These include various foodborne pathogens such as Campylobacter jejuni (Axelsson-Olsson et al, 2005;Baré et al, 2010), Escherichia coli O157:H7 (Barker et al, 1999), Listeria monocytogenes (Zhou et al, 2007), Salmonella spp. (Gaze et al, 2003;Tezcan-Merdol et al, 2004), Staphylococcus aureus (Huws et al, 2008), Arcobacter butzleri (Medina et al, 2014) and Yersinia enterocolitica (Lambrecht et al, 2013). However intraprotozoan survival and/or replication depend on various factors such as bacterial strain and environmental conditions (Schuppler, 2014;Vaerewijck et al, 2014).…”

Salmonella transcriptional signature in Tetrahymena phagosomes and role of acid tolerance in passage through the protist

“…S. enterica does not have any detectable cytotoxic effect in Tetrahymena (Brandl et al, 2005;Gourabathini et al, 2008), in contrast to Acanthamoeba spp., which are killed by S. enterica and other pathogenic species (Abu Kwaik et al, 1998;Gaze et al, 2003;Tezcan-Merdol et al, 2004;Matz et al, 2008;Feng et al, 2009). Hence, the role of SPI-2 and other virulence determinants in its resistance to digestion by Tetrahymena is less clear than their potential pathogenic function during interaction with Acanthamoeba rhysodes, in which SPI genes are also Figure 5 Frequency distribution of the number of S. Typhimurium cells in individual fecal pellets released by Tetrahymena during co-culture of the two microorganisms, as assessed with the Live/Dead BacLight stain.…”

“…Grazing resistance may occur through pre-ingestional adaptations involving development of oversized cells, surface masking or microcolony formation, and through post-ingestional adaptations that include development of toxin release, digestional resistance and/or intracellular growth (Matz and Kjelleberg, 2005). Indeed, the intracellular pathogens Mycobacterium avium, Chlamydia pneumoniae, Listeria monocytogenes and Legionella pneumophila replicate in the digestive vacuoles (phagosomes) of Acanthamoeba castellanii (Ly and Muller, 1990;Cirillo et al, 1997;Essig et al, 1997;Abu Kwaik et al, 1998) whereas Salmonella enterica serovars Dublin and Typhimurium multiply in Acanthamoeba rhysodes and Acanthamoeba polyphaga (Gaze et al, 2003;Tezcan-Merdol et al, 2004).…”

“…In addition, S. Typhimurium does not decrease the viability of Tetrahymena during its intravacuolar passage (Gourabathini et al, 2008). Therefore, its interaction appears to be different than with Acanthamoeba spp., which causes death of the protist (Gaze et al, 2003;Tezcan-Merdol et al, 2004;Feng et al, 2009). S. Typhimurium is an intracellular pathogen that has evolved specific mechanisms for its persistence and replication in eukaryotic cells.…”

Interaction between Food-borne Pathogens (Campylobacter jejuni, Salmonella Typhimurium and Listeria monocytogenes) and a Common Soil Flagellate (Cercomonas sp.)

“…Of these groups, flagellates and amoebae are thought to be the most abundant and are able to enter soil pore necks as small as 3 µm (Ekelund & Rønn, 1994;Gaze, Burroughs, Gallagher & Wellington, 2003). Flagellates as well as amoebae are important bacterial grazers, and flagellates have been shown to change the composition of the bacterial community in a different manner than the soil amoebae Acanthamoebae spp.…”