Determination of the survivability of spaceflight relevant microorganisms on different copper-containing surfaces - a precursor study for ESA space experiment „no biofilm“

Abstract

People have been fascinating for space for a long time. We are now able to send space stations, probes and telescopes into space by means of the latest technology in order to provide answers to various questions – such as “where does life come from?” and “is there life on other planets?” (Kirschvink J. 2001). The foundations were laid by the set-up, power and prestige competition of rocket technology. The first milestones were the introduction of Sputnik 1 into an orbit (1957), the orbiting of Earth by Yuri A. Gagarin (1961) (see web link (1)) (Walter, 2017) and the first manned moon-landing 1996 (Walter, 2017). But manned flights into space also lead to complications. Apart from a planetary contamination to be prevented (Rummel 1989), not only the supply of the crew and cohabitation in a confined space is a problem. In 1967 a space contract was set up. It is true that neither terrestrial organisms reach and contaminate extraterrestrial objects such as planets and moons, nor that extraterrestrial forms of life reach the Earth (Ward 2005). Therefore special clean rooms were developed, nevertheless extremophiles, such as Acinetobacter radioresistens, were detected (McCoy, Derecho et al. 2012). It is further important to ensure the health of the astronauts as best as possible. No easy task in living together in a confined space, recycling of waste products, human excretions and the use or repeated handling of surfaces of equipment or training devices for muscle building (Ritsher 2005). In hospitals too, it is essential to ensure maximum health by sometimes observing hygiene regulations in order to prevent possible infections caused by potentially pathogenic microorganisms (Pierson 2007). It is also known that, resistances, especially as a response of the bacterium to antimicrobial agents, can develop over time (Schmieder and Edwards 2012). In outer space there are also external environmental influences which are very low present or complete absent on Earth. These include ionospheric plasma species, solar UV, X-ray, galactic and solar cosmic radiation as well as microgravity (Koontz 2003). In order to keep space stations as sterile as possible, these environmental influences have to be simulated as best as possible in laboratories on Earth, and on this basis, best-adapted methods for minimizing bacteria must be developed (Horneck, Klaus et al. 2010). There are different points of attack. Since a human being has about 2 kg of bacteria (or rather 90 % of the cells of non-animal origin) (Savage 1977) on and in a human body, and these are thereby in any case as “roommates” of an astronaut into the enclosed living space in the space (Checinska 2015), no intervention or reduction of the bacteria is possible at this point. Sterilization procedures with chemicals, plasma or blue light require an active introduction by the human hand (Yin, Dai et al. 2013). What would happen if, instead of or in addition, antimicrobial surfaces were „working“, instead of an active introduction of sterilization procedures, which intervened much earlier? Which material is particularly suitable and how do different microorganisms react to these materials? For these questions the ESA “no biofilm” project was developed. Aim of this project is to characterize biofilms in the ISS environment and evaluate the antimicrobial and anti-biofilm formation activity of well-known tailor-made copper and copper alloy surfaces of spaceflight-relevant and human-associated bacterial strains. Biofilm formation in particular should be prevented. It is clear from studies that biofilms, which grow on space stations like the Mir, behave differently, look differently and the virulence is often increased, compared to controls on Earth (Kim, Tengra et al. 2013).