Microarray analysis identifies Salmonella genes belonging to the low-shear modeled microgravity regulon

ABSTRACT Only limited information is available concerning the effects of low-shear modeled microgravity (LSMMG) on cell function and morphology. We examined the behavior of Saccharomyces cerevisiae grown in a high-aspect-ratio vessel, which simulates the low-shear and microgravity conditions encountered in spaceflight. With the exception of a shortened lag phase (90 min less than controls; P < 0.05), yeast cells grown under LSMMG conditions did not differ in growth rate, size, shape, or viability from the controls but did differ in the establishment of polarity as exhibited by aberrant (random) budding compared to the usual bipolar pattern of controls. The aberrant budding was accompanied by an increased tendency of cells to clump, as indicated by aggregates containing five or more cells. We also found significant changes (greater than or equal to twofold) in the expression of genes associated with the establishment of polarity (BUD5), bipolar budding (RAX1, RAX2, and BUD25), and cell separation (DSE1, DSE2, and EGT2). Thus, low-shear environments may significantly alter yeast gene expression and phenotype as well as evolutionary conserved cellular functions such as polarization. The results provide a paradigm for understanding polarity-dependent cell responses to microgravity ranging from pathogenesis in fungi to the immune response in mammals.

Download Full-text

Low-shear modeled microgravity impacts the acid stress response and post-thermal stress behavior of acid-resistant, adaptable, and sensitive Escherichia coli O157:H7 strains

Food Control ◽

10.1016/j.foodcont.2020.107603 ◽

2021 ◽

Vol 121 ◽

pp. 107603

Author(s):

H.W. Kim ◽

M.S. Rhee

Keyword(s):

Escherichia Coli ◽

Thermal Stress ◽

Stress Response ◽

Acid Stress ◽

Escherichia Coli O157 ◽

Modeled Microgravity ◽

Stress Behavior ◽

Acid Stress Response ◽

Low Shear

Download Full-text

Influence of Low-Shear Modeled Microgravity on Heat Resistance, Membrane Fatty Acid Composition, and Heat Stress-Related Gene Expression in Escherichia coli O157:H7 ATCC 35150, ATCC 43889, ATCC 43890, and ATCC 43895

Applied and Environmental Microbiology ◽

10.1128/aem.00050-16 ◽

2016 ◽

Vol 82 (10) ◽

pp. 2893-2901 ◽

Cited By ~ 19

Author(s):

H. W. Kim ◽

M. S. Rhee

Keyword(s):

Fatty Acids ◽

Heat Stress ◽

Space Environment ◽

Content Type ◽

Modeled Microgravity ◽

E Coli ◽

Microgravity Conditions ◽

D Values ◽

Cells Cultured ◽

Low Shear

ABSTRACTWe previously showed that modeled microgravity conditions alter the physiological characteristics ofEscherichia coliO157:H7. To examine how microgravity conditions affect bacterial heat stress responses, D values, membrane fatty acid composition, and heat stress-related gene expression (clpB,dnaK,grpE,groES,htpG,htpX,ibpB, andrpoH),E. coliO157:H7 ATCC 35150, ATCC 43889, ATCC 43890, and ATCC 43895 were cultured under two different conditions: low-shear modeled microgravity (LSMMG, an analog of spaceflight conditions) and normal gravity (NG, Earth-like conditions). When 24-h cultures were heated to 55°C, cells cultured under LSMMG conditions showed reduced survival compared with cells cultured under NG conditions at all time points (P< 0.05). D values of all tested strains were lower after LSMMG culture than after NG culture. Fourteen of 37 fatty acids examined were present in the bacterial membrane: nine saturated fatty acids (SFA) and five unsaturated fatty acids (USFA). The USFA/SFA ratio, a measure of membrane fluidity, was higher under LSMMG conditions than under NG conditions. Compared with control cells grown under NG conditions, cells cultured under LSMMG conditions showed downregulation of eight heat stress-related genes (average, −1.9- to −3.7-fold). The results of this study indicate that in a simulated space environment, heat resistance ofE. coliO157:H7 decreased, and this might be due to the synergistic effects of the increases in membrane fluidity and downregulated relevant heat stress genes.IMPORTANCEMicrogravity is a major factor that represents the environmental conditions in space. Since infectious diseases are difficult to deal with in a space environment, comprehensive studies on the behavior of pathogenic bacteria under microgravity conditions are warranted. This study reports the changes in heat stress resistance ofE. coliO157:H7, the severe foodborne pathogen, under conditions that mimic microgravity. The results provide scientific clues for further understanding of the bacterial response under the simulated microgravity conditions. It will contribute not only to the improvement of scientific knowledge in the academic fields but also ultimately to the development of a prevention strategy for bacterial disease in the space environment.

Download Full-text

Escherichia coli Biofilms Formed under Low-Shear Modeled Microgravity in a Ground-Based System

Applied and Environmental Microbiology ◽

10.1128/aem.01294-06 ◽

2006 ◽

Vol 72 (12) ◽

pp. 7701-7710 ◽

Cited By ~ 80

Author(s):

S. V. Lynch ◽

K. Mukundakrishnan ◽

M. R. Benoit ◽

P. S. Ayyaswamy ◽

A. Matin

Keyword(s):

Escherichia Coli ◽

Biofilm Formation ◽

Normal Gravity ◽

Planktonic Cells ◽

Experimental Conditions ◽

Modeled Microgravity ◽

E Coli ◽

Microcarrier Beads ◽

Predicted Model ◽

Low Shear

ABSTRACT Bacterial biofilms cause chronic diseases that are difficult to control. Since biofilm formation in space is well documented and planktonic cells become more resistant and virulent under modeled microgravity, it is important to determine the effect of this gravity condition on biofilms. Inclusion of glass microcarrier beads of appropriate dimensions and density with medium and inoculum, in vessels specially designed to permit ground-based investigations into aspects of low-shear modeled microgravity (LSMMG), facilitated these studies. Mathematical modeling of microcarrier behavior based on experimental conditions demonstrated that they satisfied the criteria for LSMMG conditions. Experimental observations confirmed that the microcarrier trajectory in the LSMMG vessel concurred with the predicted model. At 24 h, the LSMMG Escherichia coli biofilms were thicker than their normal-gravity counterparts and exhibited increased resistance to the general stressors salt and ethanol and to two antibiotics (penicillin and chloramphenicol). Biofilms of a mutant of E. coli, deficient in σs, were impaired in developing LSMMG-conferred resistance to the general stressors but not to the antibiotics, indicating two separate pathways of LSMMG-conferred resistance.

Download Full-text

Low-Shear Modeled Microgravity Alters the Salmonella enterica Serovar Typhimurium Stress Response in an RpoS-Independent Manner

Applied and Environmental Microbiology ◽

10.1128/aem.68.11.5408-5416.2002 ◽

2002 ◽

Vol 68 (11) ◽

pp. 5408-5416 ◽

Cited By ~ 92

Author(s):

James W. Wilson ◽

C. Mark Ott ◽

Rajee Ramamurthy ◽

Steffen Porwollik ◽

Michael McClelland ◽

...

Keyword(s):

Stress Response ◽

Salmonella Enterica ◽

Environmental Stresses ◽

Cross Resistance ◽

Wild Type ◽

Independent Manner ◽

Modeled Microgravity ◽

Mutant Strains ◽

Serovar Typhimurium ◽

Low Shear

ABSTRACT We have previously demonstrated that low-shear modeled microgravity (low-shear MMG) serves to enhance the virulence of a bacterial pathogen, Salmonella enterica serovar Typhimurium. The Salmonella response to low-shear MMG involves a signaling pathway that we have termed the low-shear MMG stimulon, though the identities of the low-shear MMG stimulon genes and regulatory factors are not known. RpoS is the primary sigma factor required for the expression of genes that are induced upon exposure to different environmental-stress signals and is essential for virulence in mice. Since low-shear MMG induces a Salmonella acid stress response and enhances Salmonella virulence, we reasoned that RpoS would be a likely regulator of the Salmonella low-shear MMG response. Our results demonstrate that low-shear MMG provides cross-resistance to several environmental stresses in both wild-type and isogenic rpoS mutant strains. Growth under low-shear MMG decreased the generation time of both strains in minimal medium and increased the ability of both strains to survive in J774 macrophages. Using DNA microarray analysis, we found no evidence of induction of the RpoS regulon by low-shear MMG but did find that other genes were altered in expression under these conditions in both the wild-type and rpoS mutant strains. Our results indicate that, under the conditions of these studies, RpoS is not required for transmission of the signal that induces the low-shear MMG stimulon. Moreover, our studies also indicate that low-shear MMG can be added to a short list of growth conditions that can serve to preadapt an rpoS mutant for resistance to multiple environmental stresses.

Download Full-text