# Nutrient Deficiency Promotes the Entry of _Helicobacter pylori_ Cells into _Candida_ Yeast Cells
## 4 Discussion
pylori_, yeasts have specialized machinery to regulate iron uptake when this element is in high or low extracellular concentration [50]. The first Y-BLBs were identified during the first hour of co-culturing both microorganisms. The maximum percentage of Y-BLBs was observed at 24 h and 48 h in all co-cultures, but the mean of Y-BLBs obtained in the co-culture containing BB-1%FBS was significantly higher than that obtained in the other culture conditions. When analyzing the percentages of Y-BLBs, the figures were more than 50% in BB-1%FBS, between 22% and 26% in BB-5%FBS, 7% to 12% in BB-20%FBS, and 9% in co-cultures carried out in SS. Therefore, the percentages of Y-BLBs increased as the concentration of FBS decreased. This may be due to the stressing conditions sensed by _H. pylori_ that threaten its viability. On the contrary, these culture conditions offered _Candida_ all the nutrients necessary for its growth, providing protection for _H. pylori_ cells capable of harboring within yeast cells. Interestingly, we identified extracellular bacteria that adhered to the pseudohyphae of yeasts, which may be due to the adhesins present on the surface of this fungal structure. Regarding this last observation, the adherence of _H. pylori_ cells to several species of the _Candida_ genus was first reported by [PERSON] and [PERSON] [51]. The adherence of several bacteria to the surface of fungi has been reported and, in the particular case of _Candida_, it has been reported for _Staphylococcus aureus_, Group B _Streptococcus_, _Staphylococcus epidermidis_ and _Streptococcus gordonii_, among others, perhaps promoting the dissemination of bacteria throughout the host [52; 53; 54; 55]. Regarding the internalization of _H. pylori_ in a human cell model, it has been reported that it occurs most often in ulcer-related samples [56]. It is worth noting that the _H. pylori_ strain showing the best capacity to harbor within _Candida_ was the J99 strain, whose genotype is related to the development of duodenal ulcers. Another work reported the presence of a link between the coexistence of _H. pylori_ and _Candida_ and gastric ulcers, suggesting the synergism of these microorganisms in the pathogenicity of this disease [57]. Considering that both BB-1%FBS and SS are poor in nutrients, it was possible to anticipate that co-cultures in SS might show a percentage of Y-BLBs similar to that of BB-1%FBS, but this was not the case. In fact, the percentage of Y-BLBs in SS was not significantly different to that observed in the co-culture in BB-20%FBS. The absence of nutrients in SS might negatively affect the mobility of _H. pylori_ and favor the development of its coccoid stage (immobile) [58]. Although yeast cells were also in the absence of nutrients, they can survive under inanition and modulate their highly dynamic cell wall according to the conditions to which they are subjected [59]. In yeasts such as _C. glabrata_ and _C. albicans_, starvation promotes the migration of cytolytic proteins, and they can alter the expression of cell wall proteins. This leads to cell impermeability, adhesion, and the formation of biofilms to survive under stress conditions [49]. In addition, during starvation and other stress conditions that affect _C. albicans_, the chlamdsopventilation process is triggered, promoting the generation of chlamdsopores, which are cells with a much thicker cell wall, which would make the entry of _H. pylori_ difficult [60]. In addition, the loss of mobility and of bacterial viability can explain the low percentage of Y-BLBs found in SS co-cultures. On the contrary, in the abundance of FBS, both microorganisms were not under stress and,therefore, _H. pylori_ was not induced to seek refuge within yeast cells, but a baseline entry occurred anyways. The identification of BLBs as _H. pylori_ was performed using both FISH and PCR techniques. Furthermore, the LIVE/DEAD BaeLight Bacterial Viability kit allowed us to confirm the viability of _H. pylori_ within fungal cells. These results are similar to our previous works subjecting _H.