Biomedical subjects

J K Fredrickson

Publications and source records attributed to J K Fredrickson.

43 records · Page 3Linked to original sources

PubMed1991

Physiological diversity and distributions of heterotrophic bacteria in deep cretaceous sediments of the atlantic coastal plain.

A series of 23 intact core segments was obtained from two distinct deep subsurface geological formations, the Middendorf and the Cape Fear formations, underlying the southeastern coastal plain of South Carolina. The Middendorf formation in this region consists of permeable, saturated, sandy sediments; the Cape Fear formation consists mainly of less permeable sediments. The core segments were separated by vertical distances ranging from several centimeters to 48 m. Aerobic chemoheterotrophic bacteria were enumerated on a dilute medium, and populations ranged from 3.1 to 6.4 log CFU g of sediment in the Middendorf cores and from below detection to 4.3 log CFU g in the Cape Fear cores. A total of 198 morphologically distinct colony types were isolated, purified, and subjected to 108 different physiological measurements. The isolates from the two formations were distinct (i.e., they produced substantially different response patterns to the various physiological measurements), as were those in different core samples from the same formation. Cluster analysis revealed 21 different biotypes based on similarities of 75% or higher in response patterns to 21 physiological assays. One biotype contained 57 (29%) of the subsurface isolates, 10 biotypes contained 5 or more isolates, and the remainder had 4 or fewer. The organic compounds that were most commonly metabolized by the subsurface bacteria included Tween 40 (85%) and beta-hydroxybutyric acid (60%). Organic acids, in general, were also commonly metabolized by the subsurface bacteria. Isolates from the Cape Fear core segments were capable of metabolizing a higher percentage of the substrates than were bacteria isolated from the Middendorf formation. Although the heterogeneous distributions of bacteria in deep subsurface sediments may make it difficult to use aquifer microcosms to predict in situ biotransformation rates, the diversity of the physiological properties of these organisms offers promise for in situ remediation of contaminants.

Journal Article↗

PubMed1991

Isolation and characterization of a subsurface bacterium capable of growth on toluene, naphthalene, and other aromatic compounds.

A bacterium, designated F199, utilized toluene, naphthalene, dibenzothiophene, salicylate, benzoate, p-cresol, and all isomers of xylene as a sole carbon and energy source. This bacterium was isolated from Middendorf sediments, a Cretaceous age formation that underlies the Southeast Coastal Plain in South Carolina, at a depth of approximately 410 m. F199 is a gram-positive, irregular-shaped bacterium that has a varied cell morphology that is dependent on culture medium type and growth stage. F199 required microaerobic conditions (40 to 80 muM O(2)) for growth on hydrocarbons, glucose, acetate, and lactate in mineral salts medium but not for growth on rich media. [C]naphthalene mineralization by F199 was induced by either naphthalene or toulene; however, [C]toluene mineralization by this strain was induced by toluene but not naphthalene. F199 was also found to harbor two plasmids larger than 100 kb. Restricted F199 plasmid and genomic DNA did not hybridize with toluene (pWW0) or naphthalene (NAH7) catabolic plasmid DNA probes. The presence in the Middendorf formation of bacteria with the capacity for degrading a variety of aromatic compounds suggests that indigenous microorganisms may have potential for in situ degradation of organic contaminants.

Journal Article↗

PubMed1989

Intact soil-core microcosms for evaluating the fate and ecological impact of the release of genetically engineered microorganisms.

Intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. Soil-core microcosms were planted with wheat and maize seeds and inoculated with Azospirillum lipoferum SpBr17 and SpRG20a Tn5 mutants, respectively. Microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for A. lipoferum Tn5 mutant populations. A. lipoferum Tn5 populations, determined by most-probable-number technique-DNA hybridization, varied from below detection to 10 g of dry root in the rhizosphere, with smaller populations detected in the endorhizosphere. Intact soil-core microcosms were found to maintain some of the complexities of the natural ecosystem and should be particularly useful for initial evaluations of the fate of plant-associated genetically engineered bacteria.

Journal Article↗

PubMed1989

Isolation and characterization of quinoline-degrading bacteria from subsurface sediments.

Two gram-negative, motile bacteria isolated from deep subsurface sediments mineralized the nitrogen-containing polyaromatic hydrocarbon quinoline under aerobic conditions and transformed quinoline to soluble intermediates under anaerobic conditions. Many aromatic compounds were also able to serve as the sole source of carbon and energy under aerobic conditions. Rapid aerobic mineralization of quinoline at concentrations as low as 0.002 microgram ml-1 indicates that these organisms possess a high-affinity uptake and utilization system, which may reflect the oligotrophic nature of deep subsurface environments. Both bacteria harbored four plasmids of identical size, ranging from 50 to 440 kilobases.

Aerobiosis↗

PubMed1989

Vertical and horizontal variations in the physiological diversity of the aerobic chemoheterotrophic bacterial microflora in deep southeast coastal plain subsurface sediments.

Aerobic chemoheterotrophic bacteria were isolated from surface soils and coastal plain subsurface (including deep aquifer) sediments (depths to 265 m) at a study site near Aiken, S.C., by plating on concentrated and dilute media. Morphologically distinct colonies were purified, and their responses to 21 selected physiological tests were determined. These isolates were quite diverse; 626 physiologically distinct types (i.e., types with a unique pattern of responses to the 21 tests) were detected among the 1,112 isolates obtained. Physiologically distinct types were isolated on concentrated and dilute media (only 11% overlap between the groups); isolates from surface soils and subsurface sediments were also quite different (only 3% overlap). The surface soil isolates more readily utilized all but 1 of 12 carbon sources offered, and a significantly larger proportion of them hydrolyzed esculin and gelatin. Only 4% of the subsurface isolates fermented glucose, even though 82% of them could use it aerobically. l-Malate and d-gluconate were utilized by at least 75% of the subsurface isolates, and seven other carbon sources were used by at least 40% of them. Subsurface isolates from different geological formations (depths) and, to a lesser extent, from the same geological formation at different boreholes differed distinctly in their group responses to certain physiological tests. Moreover, sediments from different depths and boreholes contained physiologically distinct types of bacteria. Thus, considerable bacterial diversity was observed in coastal plain subsurface sediments, even within defined geological formations.

Journal Article↗

PubMed1988

Plasmid incidence in bacteria from deep subsurface sediments.

Bacteria were isolated from deep terrestrial subsurface sediments underlying the coastal plain of South Carolina. A total of 163 isolates from deep sediments, surface soil, and return drill muds were examined for plasmid DNA content and resistance to the antibiotics penicillin, ampicillin, carbenicillin, streptomycin, kanamycin, and tetracycline. MICs of Cu, Cr, and Hg for each isolate were also determined. The overall frequency of plasmid occurrence in the subsurface bacteria was 33%. Resistance was most frequent to penicillin (70% of all isolates), ampicillin (49%), and carbenicillin (32%) and was concluded to be related to the concentrations of the individual antibiotics in the disks used for assaying resistance and to the production of low levels of beta-lactamase. The frequencies of resistance to penicillin and ampicillin were significantly greater for isolates bearing plasmids than for plasmidless isolates; however, resistance was not transferable to penicillin-sensitive Escherichia coli. Hybridization of subsurface bacterial plasmids and chromosomal DNA with a whole-TOL-plasmid (pWWO) probe revealed some homology of subsurface bacterial plasmid and chromosomal DNAs, indicating a potential for those bacteria to harbor catabolic genes on plasmids or chromosomes. The incidences of antibiotic resistance and MICs of metals for subsurface bacteria were significantly different from those for drill mud bacteria, ruling out the possibility that bacteria from sediments were derived from drill muds.

Journal Article↗

PubMed1988

Enumeration of Tn5 mutant bacteria in soil by using a most- probable-number-DNA hybridization procedure and antibiotic resistance.

Investigations were made into the utility of DNA hybridization in conjunction with a microdilution most-probable-number procedure for the enumeration of Rhizobium spp. and Pseudomonas putida in soil. Isolates of Rhizobium spp. and P. putida carrying the transposon Tn5 were added to sterile and nonsterile Burbank sandy loam soil and enumerated over time. Soil populations of rhizobia were enumerated by colony hybridization, most-probable-number-DNA hybridization procedure, plate counts, plant infectivity most probable number, and fluorescent antibody counts. Population values compared well for all methods at 5 and 30 days after the addition of cells, although the fluorescent antibody method tended to overestimate the viable population. In nonsterile soil, most-probable-number-DNA hybridization procedure enumerated as few as 10 P. putida Tn5 cells g of soil-1 and 100 R. leguminosarum bv. phaseoli Tn5 cells g of soil-1 and should have utility for following the fate of genetically engineered microorganisms released to the environment. Among the Kmr isolates containing Tn5, approximately 5% gave a dark, more intense autoradiograph when probed with 32P-labeled pGS9 DNA, which facilitated their detection in soil. Hybridization with a pCU101 probe (pGS9 without Tn5) indicated that donor plasmid sequences were being maintained in the bacterial chromosome. Transposon-associated antibiotic resistance was also utilized as a phenotypic marker. Tn5 vector-integrate mutants were successfully enumerated at low populations (10 to 100 cells g of soil-1) in soil by both phenotypic (Kmr) and genotypic (DNA probe) analysis. However, determination of the stability of Tn5 or Tn5 and vector sequences in the bacteria is necessary.

Bacteriological Techniques↗