| Summary: | <i>Helicobacter pylori</i>, a Gram-negative bacterium, has as a natural niche the human gastric epithelium. This pathogen has been reported to enter into <i>Candida</i> yeast cells; however, factors triggering this endosymbiotic relationship remain unknown. The aim of this work was to evaluate in vitro if variations in nutrient concentration in the cultured medium trigger the internalization of <i>H. pylori</i> within <i>Candida</i> cells. We used <i>H. pylori</i>–<i>Candida</i> co-cultures in Brucella broth supplemented with 1%, 5% or 20% fetal bovine serum or in saline solution. Intra-yeast bacteria-like bodies (BLBs) were observed using optical microscopy, while intra-yeast BLBs were identified as <i>H. pylori</i> using FISH and PCR techniques. Intra-yeast <i>H. pylori</i> (BLBs) viability was confirmed using the LIVE/DEAD BacLight Bacterial Viability kit. Intra-yeast <i>H. pylori</i> was present in all combinations of bacteria–yeast strains co-cultured. However, the percentages of yeast cells harboring bacteria (Y-BLBs) varied according to nutrient concentrations and also were strain-dependent. In conclusion, reduced nutrients stresses <i>H. pylori</i>, promoting its entry into <i>Candida</i> cells. The starvation of both <i>H. pylori</i> and <i>Candida</i> strains reduced the percentages of Y-BLBs, suggesting that starving yeast cells may be less capable of harboring stressed <i>H. pylori</i> cells. Moreover, the endosymbiotic relationship between <i>H. pylori</i> and <i>Candida</i> is dependent on the strains co-cultured.
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