Microarray analysis identifies Salmonella genes belonging to the low-shear modeled microgravity regulon.
The low-shear environment of optimized rotation suspension culture allows both eukaryotic and prokaryotic cells to assume physiologically relevant phenotypes that have led to significant advances in fundamental investigations of medical and biological importance. This culture environment has also been used to model microgravity for ground-based studies regarding the impact of space flight on eukaryotic and prokaryotic physiology. We have previously demonstrated that low-shear modeled microgravity (LSMMG) under optimized rotation suspension culture is a novel environmental signal that regulates the virulence, stress resistance, and protein expression levels of Salmonella enterica serovar Typhimurium. However, the mechanisms used by the cells of any species, including Salmonella, to sense and respond to LSMMG and identities of the genes involved are unknown. In this study, we used DNA microarrays to elucidate the global transcriptional response of Salmonella to LSMMG. When compared with identical growth conditions under normal gravity (1 x g), LSMMG differentially regulated the expression of 163 genes distributed throughout the chromosome, representing functionally diverse groups including transcriptional regulators, virulence factors, lipopolysaccharide biosynthetic enzymes, iron-utilization enzymes, and proteins of unknown function. Many of the LSMMG-regulated genes were organized in clusters or operons. The microarray results were further validated by RT-PCR and phenotypic analyses, and they indicate that the ferric uptake regulator is involved in the LSMMG response. The results provide important insight about the Salmonella LSMMG response and could provide clues for the functioning of known Salmonella virulence systems or the identification of uncharacterized bacterial virulence strategies.
Wilson
James W
JW
Program in Molecular Pathogenesis and Immunity, Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
Ramamurthy
Rajee
R
Porwollik
Steffen
S
McClelland
Michael
M
Hammond
Timothy
T
Allen
Pat
P
Ott
C Mark
CM
Pierson
Duane L
DL
Nickerson
Cheryl A
CA
D001696:Biomechanical Phenomena; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D018085:Regulon; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000235:genetics* / Q000502:physiology; D014774:Virulence / Q000235:genetics; D018474:Weightlessness Simulation
D008070:Lipopolysaccharides