monocytogenes, the changes in T. AZD1480 manufacturer pyriformis concentration were examined in the presence of the LLO deficient L. monocytogenes EGDeΔhly strain with the hly gene removed by deletion. In contrast to the parental EGDe strain, EGDeΔhly did not produce any decrease among alive trophozoites

(Figure 4B) as well as no degraded cells Omipalisib supplier (data not shown) were observed by day 7. Replenishment of the hly gene by introduction of a LLO-expressing pHly plasmid restored the cytotoxic phenotype of the EGDeΔhly strain. However, by day 14 the concentration of trophozoites in co-culture with both L. monocytogenes strains could not be detected regardless on LLO production while trophozoites were present in the control axenic culture. L. monocytogenes LLO deficiency decreased protozoan encystment pace in the bacterial presence. In fact, there was no significant difference in cyst concentration between T. pyriformis grown alone or in association with the Δhly bacteria (Figure 4B). The functional hly gene located on the plasmid being introduced into the EGDeΔhly strain restored bacterial ability to accelerate encystment. Therefore, toxic effects

of wild type L. monocytogenes seemed to be due to LLO. Still, disappearance of trophozoites from the co-culture with the EGDeΔhly find more bacteria suggested that other factors besides LLO might input into L. monocytogenes toxicity. L. monocytogenes phospholipases PlcA and PlcB, specific for phosphatidyl-inositol DOK2 and phosphatidyl-choline [2], respectively, might be responsible for this effect. LLO-expressing L. innocua induces T. pyriformis mortality and encystment To confirm the role of LLO in L. monocytogenes toxicity, we checked an effect of LLO expression in non-haemolytic L. innocua on bacterial-protozoan interactions. L. innocua is a non-pathogenic species, which is closely related to L. monocytogenes [24]. Introduction of the pHly plasmid into the L. innocua strain NCTC 2188 did not result in detectable LLO production (data not shown). To improve LLO expression in L. innocua, we introduced the prfA* gene into the pHly plasmid. The prfA* gene encodes

the PrfA* protein, which is a positive regulator of hly expression in L. monocytogenes [19]. L. innocua NCTC 2188 was transformed with the obtained plasmid designated as pHly/PrfA*. LLO production by the recombinant L. innocua strain carrying the pHly/PrfA* plasmid was evidenced by Western blotting (Figure 5A). Figure 5 Changes in the T. pyriformis population in co-culture with recombinant LLO-prodicing L. innocua. A. Detection of LLO in the culture supernatant of L. innocua and L. monocytogenes. On the left, secreted proteins are separated in the 10 % SDS-PAGE gel; on the right, Western blot analysis of secreted proteins with LLO-specific antiserum; 1 – wild type L. innocua NCTC11288 strain; 2 – L. monocytogenes NCTC 5105 strain; 3 – LLO-expressing L. innocua NCTC11288 (pHly/PrfA*) strain.