title: Effect of simulated microgravity and shear stress on microcin B17 production by Escherichia coli and on its excretion into the medium.
abstract: Production of the antibacterial polypeptide microcin B17 (MccB17) by Escherichia coli ZK650 was inhibited by simulated microgravity. The site of MccB17 accumulation was found to be different, depending on whether the organism was grown in shaking flasks or in rotating bioreactors designed to establish a simulated microgravity environment. In flasks, the accumulation was cellular, but in the reactors, virtually all the microcin was found in the medium. The change from a cellular site to an extracellular one was apparently not a function of gravity, since extracellular production occurred in these bioreactors, irrespective of whether they were operated in the simulated microgravity or normal gravity mode. More probably, excretion is due to the much lower degree of shear stress in the bioreactors. Addition of even a single glass bead to the 50-ml medium volume in the bioreactor created enough shear to change the site of MccB17 accumulation from the medium to the cells.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
authors.forename: A
authors.initials: A
authors.lastname: Fang
authors.forename: D L
authors.initials: DL
authors.lastname: Pierson
authors.forename: D W
authors.initials: DW
authors.lastname: Koenig
authors.forename: S K
authors.initials: SK
authors.lastname: Mishra
authors.forename: A L
authors.initials: AL
authors.lastname: Demain
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001430:Bacteriocins / Q000096:biosynthesis*; D019149:Bioreactors; D003470:Culture Media; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D013314:Stress, Mechanical; D018474:Weightlessness Simulation
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D003470:Culture Media; C020411:microcin