1 Flight Backup Culture; 3 Irradiated Flight Backup Cultures (different levels);
1 Postflight Vibration Control (nonirradiated)
This study was to test the hypothesis that weightlessness both with or without
gamma irradiation would not affect bacterial cell growth or induction of bacterial
prophage P-22. The experiment was designed to test the effects of: 1) space
flight; 2) three chronic gamma-irradiation dose levels; and 3) temperature.
The bacteria were used to study the induction of lysogeny, a biological
process extremely sensitive to a variety of environmental factors such as vibration
and radiation. Free phage and bacterial density were also studied. Nine sets
of cultures, each consisting of replicate chambers of 1.4 ± 0.3 ml capacity,
were prepared. Each
chamber was inoculated with aliquots of a suspension of
bacteria adjusted to give mean viable density of about 100 cell/ml. Parameters
estimated postflight included: 1) total bacterial density by Coulter principle
counting; 2) viable bacterial density by colony count on nutrient agar plates;
3) free P-22 bacteriophage titer by plaque count (PFU) using aliquots of substrate
as received; and 4) induced P-22 titer by quantifying PFU following dilution
and incubation of recovered viable cells.
Space flight resulted in greater bacterial densities. The factor most likely
to be responsible for the higher densities is reduced gravity. S. typhimurium
also yielded relatively greater densities under gamma irradiation than without
radiation. The greater densities after space flight are probably a function
of random cell distri- bution in the liquid medium in reduced gravity. Such
distributions would increase the efficiency of the nutrient transfer into and
waste transport from the cell. Phage yield decreased with increasing radiation
in the space flight cultures. The ratio of phage to bacteria density is consistently
lower in flight populations. If the relative number of phage produced per bacterium
is constant, then this data indicates that induction is less frequent during
space flight.
Mattoni, R.H.T.: Effects of Spaceflight and Radiation on Growth and Induction
of Lysogenic Bacteria. Radiation Research, vol. 35, 1968, p. 499.
Mattoni, R.H.T. et al.: Induction of Lysogenic Bacteria in the Space Environment.
BIOSPEX: Biological Space Experiments, NASA TM-58217, 1979, p. 165.
Mattoni, R.H.T. et al.: Induction of Lysogenic Bacteria in the Space Environment.
The Experiments of Biosatellite II, NASA SP-204, 1971, pp. 309-324. Reference
BIO2-7 Title of Study Mattoni, R.H.T.: Space-Flight Effects and Gamma Radiation
Interaction on Growth and Induction of Lysogenic Bacteria, A Preliminary Report.
Bioscience, vol. 18, no. 6, 1968, pp. 602-608.
¥ = publication of related ground-based study