title: Effects of space flight, clinorotation, and centrifugation on the substrate utilization efficiency of E. coli.
abstract: Cultures of Escherichia coli grown in space reached a 25% higher average final cell population than those in comparably matched ground controls (p<0.05). However, both groups consumed the same quantity of glucose, which suggests that space flight not only stimulated bacterial growth as has been previously reported, but also resulted in a 25% more efficient utilization of the available nutrients. Supporting experiments performed in "simulated weightlessness" under clinorotation produced similar trends of increased growth and efficiency, but to a lesser extent in absolute values. These experiments resulted in increases of 12% and 9% in average final cell population (p<0.05), while the efficiency of substrate utilization improved by 6% and 9% relative to static controls (p=0.12 and p<0.05, respectively). In contrast, hypergravity, produced by centrifugation, predictably resulted in the opposite effect--a decrease of 33% to 40% in final cell numbers with corresponding 29% to 40% lower net growth efficiencies (p<0.01). Collectively, these findings support the hypothesis that the increased bacterial growth observed in weightlessness is a result of reduced extracellular mass transport that occurs in the absence of sedimentation and buoyancy-driven convection, which consequently also improves substrate utilization efficiency in suspended cultures.
authors.affiliation: robmarlabrown@earthlink.net
authors.forename: Robert B
authors.initials: RB
authors.lastname: Brown
authors.forename: D
authors.initials: D
authors.lastname: Klaus
authors.forename: P
authors.initials: P
authors.lastname: Todd
mesh_terms: D001692:Biological Transport / Q000502:physiology; D002498:Centrifugation; D015169:Colony Count, Microbial; D018481:Convection; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D018471:Hypergravity; D012399:Rotation; D013026:Space Flight; D013997:Time Factors; D014893:Weightlessness; D018474:Weightlessness Simulation
chemical_list: D005947:Glucose