Spaceflight and modeled microgravity effects on microbial growth and virulence

Abstract

For unsuspecting bacteria, the difference between life and death depends upon efficient and specific responses to various stressors. Facing a much larger world, microbes are invariably challenged with ever-changing environments where temperature, pH, chemicals, and nutrients are in a constant state of flux. Only those that are able to rapidly reprogram themselves and express subsets of genes needed to overcome the stress will survive and outcompete neighboring microbes. Recently, low shear stress, emulating microgravity (MG) experienced in space, has been characterized in a number of microorganisms including fungi and prokaryotes ranging from harmless surrogate organisms to bona fide pathogens. Interestingly, MG appears to induce a plethora of effects ranging from enhanced pathogenicity in several Gram-negative enterics to enhanced biofilm formation. Furthermore, MG-exposed bacteria appeared better able to handle subsequent stressors including: osmolarity, pH, temperature, and antimicrobial challenge while yeast exhibited aberrant budding post-MG-exposure. This review will focus on MG-induced alterations of virulence in various microbes with the emphasis placed on bacteria.

Fig. 1

Operating orientations of the RWV and the effect of RWV rotation on particle (microbe) suspension. a Above is a picture of a Rotatory Cell Culture System HARV RCCS-4D. This BIO HARV reactor consists of a four station rotator base, power supply with tachometer, operation manual, and four disposable culture vessels. b Depicted are disposable HARVs (photos courtesy of Synethcon Inc.). c The operating orientations of the RWV are depicted. In the LSMMG orientation, the axis of rotation of the RWV is perpendicular to the direction of the gravity force vector. In the normal-gravity (NG) orientation, the axis of rotation is parallel to the gravity force