Response of respiratory components in x-irradiated Micrococcus radiodurans

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1982

OSTI ID:6703241

Dooley, D A

Iron-containing cytochromes provide energy to repair radiation damage. The cytochromes of Micrococcus radiodurans are atypical in that they strongly resist reduction by sodium hydrosulfite or oxidation by potassium ferricyanide, but are typically highly sensitive to potassium cyanide inhibition of respiration. Respiration in this organism is highly resistant to radiation damage, being reduced to 60% of the control level 2 hours after an exposure of 600 kR, whereas other bacteria, such as E. coli, are reduced to near zero. This reduction in respiration may be due either to a defect produced in existing cytochromes or to a decrease in synthesis of new cytochromes. Growth in low iron medium yields reductions in growth rate, oxygen consumption per cell and radioresistance, the shoulder of the survival curve being obliterated. Analysis of /sup 59/Fe-labeled cell contents on Sephadex G-200 immediately following exposure shows little change in elution patterns of the cytochromes. Only about 7% of /sup 59/Fe label is lost from cells after 3 hours of incubation in YHC following 600 kR. No immediate loss of label is detected up to total exposures of 750 kR. The uptake of iron following x-ray exposure shows a depression of 40% of control at 600 kR. Incubation of labeled cells in Triton X-100 (0.25%, v/v) releases 20% of the total activity in 5 minutes. Spectral analysis of this material reveals the presence of both pigmentation and cytochrome. These observations suggest that very high doses of radiation do not produce gross structural changes in existing cytochromes, but their respiratory function is depressed. The delay exhibited in the depression of respiratory function may be the result of initial protein damage followed by some type of proteolytic degradation since there is an immediate decrease in iron uptake post-irradiation with no subsequent recovery even at sublethal exposures.

• Research Organization: State Univ. of New York, Buffalo (USA)
• OSTI ID: 6703241
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
59 BASIC BIOLOGICAL SCIENCES
CYTOCHROMES
BIOLOGICAL RADIATION EFFECTS
MICROCOCCUS RADIODURANS
IRON 59
IRON COMPOUNDS
LIQUID COLUMN CHROMATOGRAPHY
PROTEINS
RADIATION DOSES
RADIOSENSITIVITY
RESPIRATION
TRACER TECHNIQUES
UPTAKE
X RADIATION
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
CHROMATOGRAPHY
DAYS LIVING RADIOISOTOPES
DOSES
ELECTROMAGNETIC RADIATION
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IONIZING RADIATIONS
IRON ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MICROCOCCUS
MICROORGANISMS
NUCLEI
ORGANIC COMPOUNDS
PIGMENTS
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
560130* - Radiation Effects on Microorganisms
550701 - Microbiology- Tracer Techniques