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Biomedical subjects

J D Walker

Publications and source records attributed to J D Walker.

At least 127 records · Page 7Linked to original sources
PubMed1976

Enumeration of petroleum-degrading microorganisms.

A variety of factors, including concentration of oil, antibiotics, dyes, and inoculum washes, were examined to determine their effect on the total counts of microorganisms on oil-containing media. The media found to be best for enumerating petroleum-degrading microorganisms contained 0.5% (vol/vol) oil and 0.003% phenol red, with Fungizone added for isolating bacteria and streptomycin and tetracycline added for isolating yeasts and fungi. Washing the inoculum did not improve recovery of petroleum degraders. Specifically, silica gel-oil medium and a yeast medium are recommended for enumeration of petroleum-degrading bacteria and yeasts and fungi, respectively. It is suggested that counts of petroleum degraders be expressed as percentage of the total population rather than total numbers of petroleum degraders per se. Incubation temperature and presence of oil was found to influence the numbers of petroleum-degrading microorganisms at a given sampling site.

Amphotericin B↗
PubMed1976

Biodegradation of petroleum by Chesapeake Bay sediment bacteria.

Chesapeake Bay sediment bacteria from oil-contaminated and oil-free environments were compared for their ability to utilize a South Louisiana crude oil. Preferential solubility, column chromatography, gas-liquid chromatography, and computerized mass spectrometry were used to provide new and useful information regarding biodegradation of fractions and components of the crude oil. Vibrio, Pseudomonas, and Acinetobacter spp. were isolated from the culture inoculated with oil-contaminated sediment, whereas coryneforms and Pseudomonas spp. were isolated from the culture inoculated with oil-free sediment. Microorganisms from the oil-free sediment produced greater quantities of polar n-pentane-insoluble components (asphaltenes) after degradation, whereas microorganisms from the oil-contaminated sediments provided greater degradation of saturated and aromatic hydrocarbons.

Acinetobacter↗
PubMed1976

Comparison of biodegradability of crude and fuel oils.

Crude and fuel oils were compared for ability to support growth of a mixed population of estuarine bacteria. A total of four oils, two crude and two fuel oils, were examined. It was found that each of the oils supported a unique population of bacteria and yeasts, with respect to generic composition. Low-sulfur, high-saturate, South Louisiana crude oil was found to be highly susceptible to degradation. In contrast, the dense, high-sulfur, high-aromatic, Bunker C fuel oil was strongly refractory to microbial degradation.

Alkanes↗
PubMed1976

Long-chain n-alkanes occurring during microbial degradation of petroleum.

Five axenic cultures and a mixed culture were examined for ability to degrade South Louisiana, Brass River Nigerian, Anaco Venezuelan, and Altamont crude oils. A wax was observed during microbial degradation of Altamont crude oil, but not during weathering of the oil. The high-boiling n-alkanes in the wax were associated with microbial degradation of the oil and appeared to be similar to components of tarballs found in the open ocean.

Acinetobacter↗
PubMed1976

Biodegradation rates of components of petroleum.

Rates of microbial biodegradation of components of South Louisiana crude oil were determined by computer analysis of data obtained from computerized mass spectrometry. Total residue of the oil decreased exponentially with time, with maximum decrease noted at logarithmic phase, whereas asphaltenes and resins increased at the logarithmic phase of growth. Saturates decreased continuously during growth. Microbial degradation of components of crude oil was concluded to be a dynamic process.

Alkanes↗
PubMed1975

Degradation of petroleum by an alga, Prototheca zopfii.

Prototheca zopfii is an achlorophyllous alga which degrades oil. It has been found to degrade 10 and 40% of a motor oil and crude oil, respectively, when tested under appropriate conditions. Degradation of the crude oil observed in this study compares well with the amount of degradation accomplished by bacteria. P. zopfii was found to degrade a greater percentage of the aromatic hydrocarbons in motor oil than of the saturated hydrocarbons and a greater percentage of saturated hydrocarbons in crude oil than of aromatic hydrocarbons. Resins and asphaltens were produced during degradation of motor oil, whereas these fractions in crude oil were degraded. P. zopfii did not demonstrate preferential utilization of lower homologues of cycloalkanes and aromatics as has been observed with bacteria.

Alkanes↗
PubMed1975

Evaluation of petroleum-degrading potential of bacteria from water and sediment.

Bacteria from water and sediment of an oil-polluted harbor were examined for ability to degrade petroleum. Water samples contained a greater variety of bacterial species capable of degrading petroleum than sediment. Cultures from both water and sediment contained Pseudomonas and Acinetobacter spp. Bacteria present in the water samples produced significantly greater degradation of 2-,3-,4-, and 5-ring cycloalkanes and mono-, di-, tri-, tetra-, and pentaaromatics compared with bacteria in sediment samples.

Acinetobacter↗
PubMed1975

Some effects of petroleum on estuarine and marine microorganisms.

Degradation of mixed hydrocarbon substrate in a system comprising water from an environment relatively free of oil and a sediment inoculum from an oil-contaminated site was significantly greater than when sediment from the non-oil-contaminated environment served as inoculum. Mixed hydrocarbon substrate, however, was observed to have a limiting effect on the growth of autochthonous bacteria from the non-oil-contaminated estuarine source. Growth and cell yield were similarly reduced when marine sediment bacteria were cultured in seawater supplemented with mixed hydrocarbon substrate. The addition of a South Louisiana crude oil or a No. 2 fuel oil to water and sediment collected from a marsh area of Chesapeake Bay showed no limiting effects on growth of the total heterotrophic microbial flora when examined over a 28-day period. However, results of these studies indicate that the effects of petroleum on microoganisms should be examined carefully under conditions closely approximating those in situ.

Aerobiosis↗
PubMed1975

Deep-sea bacteria: growth and utilization of n-hexadecane at in situ temperature and pressure.

A mixed culture of bacteria was obtained from the sediment-water inferface of a core sample taken off the coast of Florida at a depth of 4940m. The mixed culture wasfound capable of utilizing n-hexadecane as a sole carbon source for growth at the insitu temperature (4C) and pressure (500atm). The rate of utilization under deep-ocean conditions was found to be much slower than the rate observed at ambient pressure(1 atm) and low temperature (4C).

Alkanes↗
PubMed1975

Microbial petroleum degradation: application of computerized mass spectrometry.

An analytical procedure is presented for obtaining detailed characterization of petroleum hydrocarbons which undergo microbial degradation. The procedure includes column chromatographic separation and characterization of the resulting fractions by mass spectrometry and gas chromatography. The use of computerized low-resolution mass spectrometry is offered as a method for assessing microbial degradation of petroleum. This method provides information which cannot, at the present time, be obtained by other available analytical methods. Use of this method to evaluate degradation of a South Louisiana crude oil by a mixed culture of estuarine bacteria revealed that asphaltenes and resins increased by 28% after degradation, while saturates and aromatics decreased by 83.4% and 70.5%, respectively. Most of the normal and branched-chain alkanes were degraded (96.4%), but an increase in long-chain alkanes (C28-C32) after degradation was observed by gas-liquid chromatography. Susceptibility of cycloalkanes to degradation was less as the structure varied, i.e., 6-ring greater than 1-ring greater than 2-ring greater than 3-ring greater than 5-ring greater than 4-ring. Susceptibility of aromatic components to degradation decreased with increase in the number of rings, viz., monoaromatics greater than diaromatics greater than triaromatics greater than tetraaromatics greater than pentaaromatics. Aromatic nuclei containing sulfur were twice as refractory as non-sulfur analogs.

Alkanes↗
PubMed1974

Mercury-resistant bacteria and petroleum degradation.

The concentration of mercury in water and sediment and in the oil extracted from water and sediment was determined for samples collected in Colgate Creek, located in Baltimore Harbor of the Chesapeake Bay. The concentration of mercury in the oil was 4,000 times higher than in sediment and 300,000 times higher than in water samples. The mercury-resistant bacterial populations of the samples studied have been shown to degrade oil, suggesting these bacteria to be a significant factor in the degradation of oil in Colgate Creek.

Bacteria↗
PubMed1974

Microbial petroleum degradation: use of mixed hydrocarbon substrates.

Methods of examining hydrocarbons to estimate the microbial degradation of petroleum are compared. Gas-liquid chromatography with a mixed hydrocarbon substrate has been shown to be useful in evaluating microbial potential for degradation of a number of hydrocarbons.

Journal Article↗