Microbial Responses to Microgravity and Other Low-Shear Environments

Abstract

Microbial adaptation to environmental stimuli is essential for survival. While several of these stimuli have been studied in detail, recent studies have demonstrated an important role for a novel environmental parameter in which microgravity and the low fluid shear dynamics associated with microgravity globally regulate microbial gene expression, physiology, and pathogenesis. In addition to analyzing fundamental questions about microbial responses to spaceflight, these studies have demonstrated important applications for microbial responses to a ground-based, low-shear stress environment similar to that encountered during spaceflight. Moreover, the low-shear growth environment sensed by microbes during microgravity of spaceflight and during ground-based microgravity analogue culture is relevant to those encountered during their natural life cycles on Earth. While no mechanism has been clearly defined to explain how the mechanical force of fluid shear transmits intracellular signals to microbial cells at the molecular level, the fact that cross talk exists between microbial signal transduction systems holds intriguing possibilities that future studies might reveal common mechanotransduction themes between these systems and those used to sense and respond to low-shear stress and changes in gravitation forces. The study of microbial mechanotransduction may identify common conserved mechanisms used by cells to perceive changes in mechanical and/or physical forces, and it has the potential to provide valuable insight for understanding mechanosensing mechanisms in higher organisms. This review summarizes recent and future research trends aimed at understanding the dynamic effects of changes in the mechanical forces that occur in microgravity and other low-shear environments on a wide variety of important microbial parameters

Experimental design and environmental parameters affect Rhodospirillum rubrum S1H response to space flight

“…As environmental changes induce and select for physiological, metabolic and/or genetic variations in microorganisms (Foster, 2007), it is envisioned that such adaptations will also likely occur under space flight conditions. Indeed, numerous in-flight studies have confirmed that space flight can have a pronounced effect on a variety of microbial parameters including changes in microbial proliferation rate, cell morphology, cell physiology, cell metabolism, genetic transfer among cells and viral reactivation within the cells (reviewed in Leys et al, 2004;Nickerson et al, 2004;Nicholson et al, 2005;Klaus and Howard, 2006). However, previous studies have also shown that the results from space flight and space flight analog experiments can radically differ when using different bacteria or when using the same bacterium but different culture media Leff, 2004, 2006;Benoit and Klaus, 2007;Wilson et al, 2008;Leys et al, in press).…”

BioRock: new experiments and hardware to investigate microbe–mineral interactions in space

“…B. subtilis has also been found to weather granite (Song et al 2007) in order to extract essential minerals to live. Understanding its behaviour in micro-gravity is of high importance as it has been found previously as a common contaminant on the ISS (Nickerson et al 2004). C. metallidurans CH34 is a Gram-negative, motile, nonspore forming bacterium and a model organism to study metal resistance and tolerance.…”

“…Microbial biofilms are important for biomining as one of the most commonly used industrial methods for terrestrial biomining, heap leaching reactors, require the mining microorganisms to grow in biofilms (Rawlings & Johnson 2007). Microbial biofilms have been found to behave quite differently in low gravity and other low-shear environments than is usually expected from them on Earth (see Nickerson et al 2004 for a review). Differences in biofilm formation in space have been observed in organisms that have been studied from the medical perspective.…”

Biological system development for GraviSat: A new platform for studying photosynthesis and microalgae in space

“…Microorganisms, however, have been generally regarded as too small and intracellularly homogeneous for gravity to have an impact on their physiology (Pollard, 1965). In recent years, evidence to the contrary has been steadily mounting (Nickerson et al, 2004). Escherichia coli (Thévenet et al, 1996;Klaus et al, 1997), Bacillus subtilis (Mennigmann and Lange, 1986) and Salmonella typhimurium (Mattoni, 1968) cultures have all displayed altered growth characteristics during space flight.…”