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Campbell, J. E.

Publications and source records attributed to Campbell, J. E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The experiments conducted to determine the heat resistance of Bacillus megaterium ATCC 6458 at 90 and 100 C were completed. Estimates from replicate experiments at eight percent relative humidities (less than 0.001 to 100% RH) for each temperature were computed. A Bacillus cereus strain with high heat resistance was cultured and the resistance determined in phosphate buffer (D sub 121.1 = 2.16 min and z = 8.7 C). The profile of the dry heat resistance of B. megaterium is summarized and the most resistant condition to the three spores (Bacillus subtilis var. niger, ATCC 29669, and Bacillus stearothermophilus, strain 1518) is compared.

Reyes, A. L.↗
NASA NTRS1976

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The heat resistance of Bacillus subtilis var. niger was measured from 85 to 125 C using moisture levels of % RH or = 0.001 to 100. Curves are presented which characterize thermal destruction using thermal death times defined as F values at a given combination of three moisture and temperature conditions. The times required at 100 C for reductions of 99.99% of the initial population were estimated for the three moisture conditions. The linear model (from which estimates of D are obtained) was satisfactory for estimating thermal death times (% RH or = 0.07) in the plate count range. Estimates based on observed thermal death times and D values for % RH = 100 diverged so that D values generally gave a more conservative estimate over the temperature range 90 to 125 C. Estimates of Z sub F and Z sub L ranged from 32.1 to 58.3 C for % RH of or = 0.07 and 100. A Z sub D = 30.0 was obtained for data observed at % RH or = 0.07.

Reyes, A. L.↗
NASA NTRS1975

Ecology and Thermal Inactivation of Microbes in and on Interplanetary Space Vehicle Components

Spores of Bacillus subtilis var. niger were heat treated in aqueous suspension at 90 C, and observed for morphological changes and loss of viability. The 5 logs reduction that occurred in broth at 90 min required 210 min in buffered water. Five characteristic changes observed after spores were exposed 120 min at 90 C in buffered water were: (1) 90% loss of spore viability, (2) 5% stainability, (3) 76% increase in spore size (as observed by scanning electron microscopy), (4) 21% of spore areas remaining refractile, and (5) an increase of 77% in packed cell volume (PCV). Stainability and PCV changes were recognized only after secondary exposure in broth. Extended heat exposure (3 h at 90 C) resulted in 99% loss of spore viability and 99% loss of stainability. After 4 hours of heat exposure, 90% of the cells disintegrated. These results suggest that early germinal changes occurr concurrently with the early changes in the heat susceptibility of dormant spores.

Reyes, A. L.↗
NASA NTRS1975

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Dry heat treatment is specified as the preferred means for the terminal sterilization of spacecraft and for decontamination of spacecraft components. The presence of organisms highly resistant to dry heat in soil and fallout around assembly and industrial manufacturing areas is shown. The dry heat survival characteristics of the Cape Kennedy isolate 4-6 B. brevis spores is demonstrated. The presence of hardy organisms from soil samples obtained from geographical areas of the United States is shown. A resistant fraction appears to occur in low numbers in a soil sample. The heat resistance characteristics of 4-6 B. brevis and B. subtilis var. niger spores are compared. Their morphological characteristics are compared by scanning electron microscopy.

Reyes, A. L.↗
NASA NTRS1974

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Dry heat sterilization of spacecraft was investigated by studying the production of spore crops, and thermal inactivation of the spores, and bacillus subtillus. Spore assays were made by conventional plate count methods, and survival curves for the spores are presented. The results indicate that the inherent resistance of spores from a parent cell can be maintained.

Campbell, J. E.↗
NASA NTRS1974

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The uses of scanning electron microscopy in assessing changes that occur in spores exposed to wet and dry heat cycles at elevated temperatures were examined. Several species of Bacillus and other nonspore-forming species of organisms were used for the experiment. Surface morphology of viable and nonviable organisms was clearly detectable by this method, making it a potentially useful technique for investigating microbial inactivation on space vehicle surfaces and components. Micrographs of the spores and bacterial cells are provided.

Campbell, J. E.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The mechanism for thermal inactivation of bacterial spores under moist or dry heat was studied. Experimental conditions were established relating to spore loss of heat resistance and loss of optical density as a measure of the rate and extent of germination in spore suspensions. Events occurring during germination were correlated with phase darkening (refractility and non-refractility of spores), stainability characteristics of heat and non-heat treated spores, morphological characteristics, and studies on swelling of spores by an increase in packed cell volume.

Campbell, J. E.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Studies were made of atypical organisms found in Bacillus subtilis var. niger spore colonies. Efforts were aimed at: (1) determining the heat sensitivity of these atypical white spores treated under dry heat conditions and their influence on the nature of the survival curve, (2) preparing a new spore crop obtained from spore isolates by purification procedures, and (3) comparing spore crops obtained from Cape Kennedy (SSM-10) and Minnesota (Minn. sp. AAEF) with the old Cincinnati and new purified Cincinnati spore crop under dry heat conditions.

Campbell, J. E.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The thermal inactivation curve for Bacillus subtilis var. niger spores on the Viking lander is examined. Tests were conducted at 113 C and 25% RH, and over a wide range of temperatures using .001% RH and additions of P2O5 to dry the environment. Results show the 25% RH environment did not significantly reduce the survival curve, while the survival curves for spores treated under the drier .001% RH environment was reduced by a factor of 3.

Campbell, J. E.↗
NASA NTRS1972

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The sterilization parameters for the Viking lander of D sub 125 C = 30 minutes and z = 21 C for the exposed bioburden were derived from the experimental findings of several laboratories conducting thermal inactivation studies on Bacillus subtilis var. niger by dry heat. The moisture constraint, that the sterilizing gas shall be less than 25 percent relative humidity at standard conditions of 0 C and 760 mm Hg pressure, was added in recognition of the profound influence of water vapor on the time and temperature required for thermal inactivation of these spores. Data is presented demonstrating that the application of the moisture parameter does not significantly change the D sub 125 C and z values of 30 minutes and 21 C, respectively. Data are presented also to show the maximum influence that could be expected by decreasing the humidity to near zero percent relative humidity at 105, 113, and 125 C.

Campbell, J. E.↗
NASA NTRS1971

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Data showing that 90 C was a more effective temperature than 125 C for the destruction of Bacillus subtilis var. niger when the head-space moisture was fixed at 474 micrograms H2O/ml have been confirmed and are summarized. The influence of head-space moisture at 90 C was investigated and it was observed that as the head-space moisture was increased 474 micrograms H2O/ml, there was a corresponding increase in lethality of the system. This moisture level corresponded to 100% relative humidity at 90 C, and additional water in the cans should have had no effect. A profound descrease was observed in the destruction of the organisms when additional water was added. The discontinuity observed in these data is troublesome and must be resolved as the first step in an orderly exploration of low temperature inactivation of B. subtilis var. niger.

Campbell, J. E.↗