Ultrastructural damage in Streptococcus mutans incubated with saliva and histatin 5.

Publication date: Available online 8 January 2018
Source:Archives of Oral Biology
Author(s): A.M. Fernández-Presas, Y. Márquez Torres, R. García González, A. Reyes Torres, I. Becker Fauser, H. Rodríguez Barrera, B. Ruíz García, R. Toloza Medina, J. Delgado Domínguez, J.L. Molinarí Soriano
ObjectiveTo study the ultrastructural alterations induced in Streptococcus mutans (ATCC 25175) incubated with saliva, saliva plus histatin 5 and histatin 5.MethodsS. mutans incubated with saliva histatin 5 or a combination of both were morphologically analyzed and counted. The results were expressed as (CFU)ml⁻¹. Ultrastructural damage was evaluated by transmission electron microscopy. Ultrastructural localization of histatin 5 was examined using immunogold labeling. Apoptotic cell death was determined by flow cytometry (TUNEL).ResultsA decrease in the bacteria numbers was observed after incubation with saliva, saliva with histatin 5 or histatin 5 compared to the control group (p<0.0001). Ultrastructural damage in S. mutans incubated with saliva was found in the cell wall. Saliva plus histatin 5 induced a cytoplasmic granular pattern and decreased the distance between the plasma membrane bilayers, also found after incubation with histatin 5, together with pyknotic nucleoids. Histatin 5 was localized on the bacterial cell walls, plasma membranes, cytoplasm and nucleoids. Apoptosis was found in the bacteria incubated with saliva (63.9%), saliva plus histatin 5 (71.4%) and histatin 5 (29.3%). Apoptosis in the control bacteria was 0.2%.ConclusionsAntibacterial activity against S. mutans and the morphological description of damage induced by saliva and histatin 5 was demonstrated. Pyknotic nucleoids observed in S. mutans exposed to saliva, saliva plus histatin 5 and histatin 5 could be an apoptosis-like death mechanism. The knowledge of the damage generated by histatin 5 and its intracellular localization could favor the design of an ideal peptide as a therapeutic agent.



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