Gravitational Effects on Biofilm Formation During Space Flight (Micro-2) - 07.29.14
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The Gravitational Effects on Biofilm Formation During Space Flight (Micro-2) experiment studies how gravity alters biofilm (aggregation of microorganisms) formation with the goal of developing new strategies to reduce their impact on crew health and to minimize the harmful effects of biofilms on materials in space and on Earth.
Science Results for Everyone
Space flight can lead to increased growth and virulence of bacteria, but just how remains unclear. Aggregations of microorganisms, or biofilms, formed in space from cultured Pseudomonas aeruginosa (a common bacterium affecting already ill people) showed increased number of viable cells, biomass, and thickness. Researchers also observed formation of column-and-canopy shaped biofilms, with flagella-driven motility playing a key role (flagella are whip-like structures that enable cells to “swim” in liquids). These findings indicate increased biofouling and microbial-induced corrosion could have profound detrimental effects on long spaceflights. A critical next step is exploring the effects of such changes on human health.
University of Colorado at Boulder, BioServe Space Technologies, Boulder, CO, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2010 - September 2010
Previous ISS Missions
This will be the first flight for the Micro-2 experiment.
- The Gravitational Effects on Biofilm Formation During Space Flight (Micro-2) investigation aims to understand the different responses and physical effects of reduced gravitational force on biofilm formation (aggregation of microorganisms). Cells grown in microgravity will be compared to cells grown in normal gravity. The amount of biomass formed is measured and confocal microscopy is used to identify changes in the three-dimensional structures of the biofilms. This study will also test a number of newly developed antimicrobial surfaces for their potential to reduce biofilm formation.
- Understanding the different responses and physical effects of microgravity on biofilm formation may provide new insights into combating biofilm formation in space. Further, this work may also lead to better management and treatment of infections in space and on Earth.
The goal of the Gravitational Effects on Biofilm Formation During Space Flight (Micro-2) experiment is to understand the effects of microgravity on the growth, cellular physiology, and cell-cell interactions in microbial biofilms (aggregation of microorganisms). It will focus on two model microorganisms that form biofilms both inside and outside of the human body, Pseudomonas aeruginosa and Staphylococcus aureus. These microbes can switch between benign and pathogenic interactions with humans and may be relevant to crew health during extended missions. This experiment will also test the ability of novel antimicrobial surfaces to reduce biofilm formation.
When cells form biofilms they have a number of potentially harmful properties, including increased potential for infection and increased resistance to antimicrobial compounds. Biofilms have the potential to cause significant damage to both spacecraft and their crew; numerous problems caused by biofilms were documented on Mir. A greater understanding of the effects of spaceflight on biofilms is critical.
The Micro-2 experiment will make use of Group Activation Packs (GAPs) stored in a Commercial Generic Bioprocessing Apparatus (CGBA). The CGBA is a flight certified incubator capable of controlling the temperature between 8ºC and 37ºC and can hold up to 16 GAPs. Each GAP holds eight Fluid Processing Apparatus (FPA) inserts. The FPA is composed of a glass barrel divided into three chambers that are separated from one another by rubber septa. Each FPA will contain growth medium with membranes in the first chamber, a microbial culture suspended in stasis medium in the second chamber, and a termination reagent in the last chamber.
Understanding the different effects of microgravity on biofilm formation may provide new insights into combating biofilm formation in space and may lead to better management and treatment of infections if they occur. Also, novel antimicrobial surfaces will be tested for their potential to reduce the impact of biofilms in future spacecraft design.
According to the Center for Disease Control (CDC), hospital-acquired infections are the fourth leading cause of death in the United States behind stroke, cancer and heart disease. Furthermore, it is estimated that >65% of all bacterial infections are associated with biofilms. A greater understanding of biofilms is essential if we are to find effective methods to combat their formation. Furthermore, the low-shear conditions microbes experience in microgravity are similar to those found in the human body that are difficult to study. This work may provide new insights into the role of shear and other physical effects, such as convection, on biofilm formation.
The Micro-2 experiment consists of 128 samples housed in 16 GAPs. The temperature profile of the CGBA and the two temperature loggers (HOBOs) are required for the post-flight analysis of the data.
The samples will be stowed in the CGBA at 8ºC until as late in the mission as possible then CGBA temperature will be set to 37ºC. After 14-21 hours, to allow the temperature of the samples in the FPAs to have reached and stabilized at 37ºC, all 16 GAPs will be activated. To activate the samples, a crewmember must remove the CGBA from its middeck stowage location, take out each GAP and install the hand crank. The hand crank is then turned until the cell suspension in the second chamber is introduced to the growth media in the first chamber. Following the 72-hour growth period, a crewmember will again install the hand crank and terminate the GAPs by adding the termination reagent in the last chamber to the cells. Only GAPs 1-10 will need to be terminated. All GAPs will be returned to the CGBA and the CGBA will be set to 8ºC where it will remain until recovery.
While planktonic cultures (grown under constant mixing) of microbes have indicated that space flight can lead to increases in growth and virulence, the effects of space flight on biofilm development and physiology remain unclear. To address this issue, Pseudomonas aeruginosa was cultured during two Atlantis space shuttle missions: STS-132 and STS-135, and the biofilms formed during space flight were characterized. Micro-2 reveals the first evidence of space flight affecting the biofilm formation of P. aeruginosa. An increased number of viable cells, increased biomass, and increased thickness were observed in space flight biofilms when compared to ground controls regardless of phosphate concentration or carbon source. Results also show P. aeruginosa forming column-and-canopy shaped biofilms during space flight and flagella-driven motility plays a key role in the formation of this unique structure, where flagella are structures that enable cells to move in liquids by "swimming". The findings indicate that altered biofilm production during space flight may have detrimental impacts on long-term space flight missions, where increases in biofouling and microbial-induced corrosion could have profound impacts on mission success. Furthermore, it will be important to explore the effects of such changes on human health through pathogenic and beneficial interactions between humans and microbes during space flight (Kim 2013).
Kim W, Tengra FK, Shong J, Marchand N, Chan HK, Young Z, Pangule RC, Parra MP, Dordick JS, Plawsky JL, Collins CH. Effect of spaceflight on Pseudomonas aeruginosa final cell density is modulated by nutrient and oxygen availability. BMC Microbiology. 2013 November 6; 13(1): 241.
Kim W, Tengra FK, Young Z, Shong J, Marchand N, Chan HK, Pangule RC, Parra MP, Dordick JS, Plawsky JL, Collins CH. Spaceflight Promotes Biofilm Formation by Pseudomonas aeruginosa. PLOS ONE. 2013 April 29; 8(4): e62437. DOI: 10.1371/journal.pone.0062437.
Ground Based Results Publications
McLean RJ, Cassanto JM, Barnes MB, Koo JH. Bacterial biofilm formation under microgravity conditions. Federation of European Microbiological Societies - Microbiology Letters. 2001; 195: 115-119.
Flight Systems Implementation: Payloads
The GAP-FPA is essentially a microgravity test tube that allows controlled, sequential mixing of 2 or 3 fluids in a weightless environment. Image courtesy of BioServe Space Technologies, University of Colorado - Boulder, Boulder, CO.
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