Drinking Coffee in Space: The Impact of Microgravity on Streptococcus mutans on Susceptibility to Coffee (SmCoffee) - 01.10.19

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ISS Science for Everyone

Science Objectives for Everyone
Drinking Coffee in Space: The Impact of Microgravity on Streptococcus mutans on Susceptibility to Coffee (SmCoffee) investigates how coffee affects the oral hygiene of crew members during spaceflight. On Earth, coffee is known to kill or diminish the growth of S. mutans, a bacteria commonly found in the human mouth, and so may support better dental hygiene. This student-developed investigation grows S. mutans aboard the space station and exposes it to coffee to determine the effect on the bacteria in microgravity.
Science Results for Everyone
Information Pending

The following content was provided by Olivia Rothenberg, Sophie Muncy, and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Olivia Rothenberg, iLEAD Schools, Castaic, CA, United States
Sophie Muncy, iLEAD Schools, Castaic, CA, United States

Renate Lux, Ph.D., UCLA School of Dentistry, Los Angeles, CA, United States
Jacob Cohen, Ph.D., NASA Ames Research Center, Moffett Field, CA, United States

Santa Clarita Valley International Public Charter School, Castaic, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
National Laboratory (NL)

Research Benefits
Information Pending

ISS Expedition Duration
October 2018 - March 2019

Expeditions Assigned

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • Drinking Coffee in Space: The Impact of Microgravity on Streptococcus mutans on Susceptibility to Coffee (SmCoffee) is a student investigation that studies the effect of cavity-causing bacteria on teeth in a space environment.
  • Crew members drink coffee and care for their dental hygiene regularly aboard the International Space Station (ISS). Drinking coffee in lower gravity environments may support dental hygiene.
  • S. mutans is a cavity-causing bacterium that lives in the human mouth, and coffee is known to kill or diminish the growth of S. mutans in normal (1g) gravity.
  • This investigation allows students to study the effects of coffee on S. mutans in microgravity.
  • Counts of the surviving, if any, bacterial cells after application of coffee are recorded.
  • Comparisons between S. mutans grown in normal gravity and microgravity are drawn. The investigation relies on prior bacterial growth data under normal gravity conditions.
  • This investigation is primarily an educational opportunity for study in middle and high school classrooms.


The main objective of Drinking Coffee in Space: The Impact of Microgravity on Streptococcus mutans on Susceptibility to Coffee (SmCoffee) is to support a middle school student-derived research idea and use the proposed experiment as an extended learning opportunity in the classroom. The research question asked by the students is, “Does microgravity alter killing of the cariogenic oral bacterium Streptococcus mutans by coffee at a concentration that is typical for human consumption?”
This research question is relevant for modern space exploration because crew members spend long periods of time in microgravity. Several studies show that microgravity impacts several parameters that are associated with the development of caries such as reduced saliva flow, decreased lysozyme production and increased dental calculus formation. Furthermore, a separate study of a random sample of 1000 study participants demonstrated that coffee, when consumed without additives, reduces the incidence of caries. Another study found that simulated microgravity has a significant effect on S. mutans physiology including a substantial increase in cellular aggregation as well as susceptibility to killing by hydrogen peroxide (H2O2). Since crew members consume coffee in space, investigating the effect of coffee and its potential to kill the major cariogenic species S. mutans in microgravity may provide important insight into the utility of coffee in supporting oral health during spaceflight.
The students who originated the project collaborated with a research laboratory at the University of California, Los Angeles (UCLA) School of Dentistry to generate preliminary data for the experimental conditions. This includes determining the minimum inhibitory concentration of coffee for S. mutans, which was found to be at ¼ of the recommended strength of the commercially available instant coffee powder that is used in the investigation. Furthermore, the viability of S. mutans cells, which were dried onto sterile paper points in the presence and absence of trehalose or sucrose as dehydration protectants, was tested for their ability to withstand extended storage at 4ºC and 25ºC. The investigations performed to obtain these results are replicated in the classroom as part of a continuing collaboration with the UCLA School of Dentistry. This investigation provides a combination of theoretical and hands-on experience for International Leadership, Entrepreneurial Development, Arts, and Design Thinking (iLEAD) students, especially for those interested in science, technology, engineering, and mathematics (STEM)-related fields.

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Space Applications

Crew members regularly drink coffee and care for their dental hygiene aboard the space station. Drinking coffee may help prevent cavities caused by S. mutans, contributing to better health for crew members on future missions.

Earth Applications

This investigation provides students with hands-on experience conducting science in space, inspiring them to pursue careers in science, technology, engineering and math. In addition, better understanding of coffee’s effects on S. mutans may contribute to improved dental hygiene on Earth.

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Operational Requirements and Protocols

One MixStix containing a paper point with 109 cells of dried Streptococcus in 1% trehalose in Volume 1, 6 mL of sterile brain heart infusion (BHI) broth in Volume 2, and 0.04 g of freeze-dried coffee powder in Volume 3 is used in this investigation. The MixStix are kept at 4ºC until D-3 days prior to departure. On Day-3, Clamp A, which separates Volumes 1 and 2, is opened to allow mixing between the two volumes. The MixStix is gently inverted several times to allow the paper point to be fully immersed in BHI. The MixStix are kept at 25ºC until D-1 days. On day D-1, Clamp B, which separates Volumes 2 and 3, is opened to allow combining of all volumes. The MixStix is shaken vigorously by inverting it upside down several times to allow the freeze-dried coffee to dissolve in the bacteria containing BHI. The MixStix is kept at 25ºC for one additional day. The MixStix then return to 4ºC until investigation is returned to the school.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites
iLEAD Aerospace

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