Accumulation of Mn(II) in Deinococcus radiodurans facilitates gamma-radiation resistance.

Deinococcus radiodurans is extremely resistant to ionizing radiation. How this bacterium can grow under chronic gamma radiation [50 grays (Gy) per hour] or recover from acute doses greater than 10 kGy is unknown. We show that D. radiodurans accumulates very high intracellular manganese and low iron levels compared with radiation-sensitive bacteria and that resistance exhibits a concentration-dependent response to manganous chloride [Mn(II)]. Among the most radiation-resistant bacterial groups reported, Deinococcus, Enterococcus, Lactobacillus, and cyanobacteria accumulate Mn(II). In contrast, Shewanella oneidensis and Pseudomonas putida have high iron but low intracellular manganese concentrations and are very sensitive. We propose that Mn(II) accumulation facilitates recovery from radiation injury.

Effects of prenatal hypoxia on the formation of immune deficiency in newborn mice.

Fetal hypoxia in the II trimester of pregnancy caused immunodeficiency in newborn mice: inhibition of antibody production to sheep erythrocytes and disturbances in migration of early hemopoietic precursors from the bone marrow to the spleen.