Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl

<i>Staphylococcus aureus</i>, an opportunistic bacterium found in the oral cavity, has been reported as a causative agent of infective endocarditis and pneumonia. Salt is an essential mineral for cell maintenance in the human body. This study was conducted to clarify how salt affects the...

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Main Authors: Yusuke Iwabuchi, Hiroko Yoshida, Shuichiro Kamei, Toshiki Uematsu, Masanori Saito, Hidenobu Senpuku
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Microorganisms
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Online Access:https://www.mdpi.com/2076-2607/13/5/1118
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author Yusuke Iwabuchi
Hiroko Yoshida
Shuichiro Kamei
Toshiki Uematsu
Masanori Saito
Hidenobu Senpuku
author_facet Yusuke Iwabuchi
Hiroko Yoshida
Shuichiro Kamei
Toshiki Uematsu
Masanori Saito
Hidenobu Senpuku
author_sort Yusuke Iwabuchi
collection DOAJ
description <i>Staphylococcus aureus</i>, an opportunistic bacterium found in the oral cavity, has been reported as a causative agent of infective endocarditis and pneumonia. Salt is an essential mineral for cell maintenance in the human body. This study was conducted to clarify how salt affects the formation of biofilms by <i>S. aureus</i> and <i>Streptococcus mutans</i>, pathogens implicated in dental caries. Bacteria were cultivated with various concentrations of NaCl on a 96-well microtiter plate in tryptic soy broth with 0.25% sucrose or 0.25% glucose (TSBs and TSBg, respectively) for 16 h. The effects of glucosyltransferase in <i>S. mutans</i> membrane vesicles (MVs) and extracellular DNA during biofilm formation were also analyzed. <i>S. aureus</i> biofilms were induced by 0.004–0.25 M NaCl but not by NaCl at concentrations greater than 0.25 M in TSBs. The mixed <i>S. aureus</i> and <i>S. mutans</i> biofilms gradually grew and were constructed by dead cells in a NaCl concentration-dependent manner in both TSBs and TSBg. Moreover, biofilms were slightly induced by glucan generation mediated by the glucosyltransferases in MVs under high-salinity conditions. The formation of mixed-species <i>S. aureus</i> and <i>S. mutans</i> biofilms increased in the presence of both extracellular DNA and MVs. Therefore, extracellular DNA, MVs, and dead cells are factors that promote <i>S. aureus</i> biofilm formation under harsh conditions containing NaCl. The sugar (sucrose and glucose) ingestion-induced <i>S. mutans</i> biofilm may be a risk factor for infection by opportunistic pathogens such as <i>S. aureus</i> in individuals who consume food and drinks containing high concentrations of salt.
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publishDate 2025-05-01
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spelling doaj-art-112cfe258242445e975ff5e1dff2d2d52025-08-20T03:47:54ZengMDPI AGMicroorganisms2076-26072025-05-01135111810.3390/microorganisms13051118Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaClYusuke Iwabuchi0Hiroko Yoshida1Shuichiro Kamei2Toshiki Uematsu3Masanori Saito4Hidenobu Senpuku5Department of Pediatric Dentistry/Special Needs Dentistry, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, Tokyo 113-8549, JapanDepartment of Orthodontics, Nihon University Dental School at Matsudo, Chiba 271-8587, JapanDepartment of Microbiology and Immunology, Nihon University Dental School at Matsudo, Chiba 271-8587, JapanDepartment of Microbiology and Immunology, Nihon University Dental School at Matsudo, Chiba 271-8587, JapanDepartment of Microbiology and Immunology, Nihon University Dental School at Matsudo, Chiba 271-8587, JapanDepartment of Microbiology and Immunology, Nihon University Dental School at Matsudo, Chiba 271-8587, Japan<i>Staphylococcus aureus</i>, an opportunistic bacterium found in the oral cavity, has been reported as a causative agent of infective endocarditis and pneumonia. Salt is an essential mineral for cell maintenance in the human body. This study was conducted to clarify how salt affects the formation of biofilms by <i>S. aureus</i> and <i>Streptococcus mutans</i>, pathogens implicated in dental caries. Bacteria were cultivated with various concentrations of NaCl on a 96-well microtiter plate in tryptic soy broth with 0.25% sucrose or 0.25% glucose (TSBs and TSBg, respectively) for 16 h. The effects of glucosyltransferase in <i>S. mutans</i> membrane vesicles (MVs) and extracellular DNA during biofilm formation were also analyzed. <i>S. aureus</i> biofilms were induced by 0.004–0.25 M NaCl but not by NaCl at concentrations greater than 0.25 M in TSBs. The mixed <i>S. aureus</i> and <i>S. mutans</i> biofilms gradually grew and were constructed by dead cells in a NaCl concentration-dependent manner in both TSBs and TSBg. Moreover, biofilms were slightly induced by glucan generation mediated by the glucosyltransferases in MVs under high-salinity conditions. The formation of mixed-species <i>S. aureus</i> and <i>S. mutans</i> biofilms increased in the presence of both extracellular DNA and MVs. Therefore, extracellular DNA, MVs, and dead cells are factors that promote <i>S. aureus</i> biofilm formation under harsh conditions containing NaCl. The sugar (sucrose and glucose) ingestion-induced <i>S. mutans</i> biofilm may be a risk factor for infection by opportunistic pathogens such as <i>S. aureus</i> in individuals who consume food and drinks containing high concentrations of salt.https://www.mdpi.com/2076-2607/13/5/1118biofilmmembrane vesicle<i>S. mutans</i>NaCl<i>S. aureus</i>
spellingShingle Yusuke Iwabuchi
Hiroko Yoshida
Shuichiro Kamei
Toshiki Uematsu
Masanori Saito
Hidenobu Senpuku
Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
Microorganisms
biofilm
membrane vesicle
<i>S. mutans</i>
NaCl
<i>S. aureus</i>
title Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
title_full Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
title_fullStr Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
title_full_unstemmed Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
title_short Formation of Mono-Organismal and Mixed <i>Staphylococcus aureus</i> and <i>Streptococcus mutans</i> Biofilms in the Presence of NaCl
title_sort formation of mono organismal and mixed i staphylococcus aureus i and i streptococcus mutans i biofilms in the presence of nacl
topic biofilm
membrane vesicle
<i>S. mutans</i>
NaCl
<i>S. aureus</i>
url https://www.mdpi.com/2076-2607/13/5/1118
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