Search PubMed⌕ Search

Biomedical subjects

M A Schneegurt

Publications and source records attributed to M A Schneegurt.

18 recordsLinked to original sources
PubMed2004

Halotolerant aerobic heterotrophic bacteria from the Great Salt Plains of Oklahoma.

The Salt Plains National Wildlife Refuge (SPNWR) near Cherokee, Oklahoma, contains a barren salt flat where Permian brine rises to the surface and evaporates under dry conditions to leave a crust of white salt. Rainfall events dissolve the salt crust and create ephemeral streams and ponds. The rapidly changing salinity and high surface temperatures, salinity, and UV exposure make this an extreme environment. The Salt Plains Microbial Observatory (SPMO) examined the soil microbial community of this habitat using classic enrichment and isolation techniques and phylogenetic rDNA studies. Rich growth media have been emphasized that differ in total salt concentration and composition. Aerobic heterotrophic enrichments were performed under a variety of conditions. Heterotrophic enrichments and dilution plates have generated 105 bacterial isolates, representing 46 phylotypes. The bacterial isolates have been characterized phenotypically and subjected to rDNA sequencing and phylogenetic analyses. Fast-growing isolates obtained from enrichments with 10% salt are predominantly from the gamma subgroup of the Proteobacteria and from the low GC Gram-positive cluster. Several different areas on the salt flats have yielded a variety of isolates from the Gram-negative genera Halomonas, Idiomarina, Salinivibrio, and Bacteroidetes. Gram-positive bacteria are well represented in the culture collection including members of the Bacillus, Salibacillus, Oceanobacillus, and Halobacillus.

Bacteria, Aerobic↗
PubMed2004

DNA-repair potential of Halomonas spp. from the Salt Plains Microbial Observatory of Oklahoma.

The Great Salt Plains (GSP), an unvegetated, barren salt flat that is part of the Salt Plains National Wildlife Refuge near Cherokee, Oklahoma, is the site of the Salt Plains Microbial Observatory. At the GSP the briny remains of an ancient sea rise to the surface, evaporate under dry conditions, and leave crusts of white salt. Adaptation to this environment requires development of coping mechanisms providing tolerance to desiccating conditions due to the high salinity, extreme temperatures, alkaline pH, unrelenting exposure to solar UV radiation, and prevailing winds. Several lines of evidence suggest that the same DNA repair mechanisms that are usually associated with UV light or chemically induced DNA damage are also important in protecting microbes from desiccation. Because little is known about the DNA repair capacity of microorganisms from hypersaline terrestrial environments, we explored the DNA repair capacity of microbial isolates from the GSP. We used survival following exposure to UV light as a convenient tool to assess DNA repair capacity. Two species of Halomonas (H. salina and H. venusta) that have been isolated repeatedly from the GSP were chosen for analysis. The survival profiles were compared to those of Escherichia coli, Pseudomonas aeruginosa, and Halomonas spp. from aquatic saline environments. Survival of GSP organisms exceeded that of the freshwater organism P. aeruginosa, although they survived no better than E. coli. The GSP isolates were much more resistance to killing by UV than were the aquatic species of Halomonas reported in the literature [Martin et al. (2000) Can J Microbiol 46:180-187]. Unlike E. coli, the GSP isolates did not appear to have an inducible, error-prone repair mechanism. However, they demonstrated high levels of spontaneous mutation.

Adaptation, Physiological↗
PubMed2001

Implications of platinum-group element accumulation along U.S. roads from catalytic-converter attrition.

Automobile catalytic converters are dispersing platinum-group elements (PGEs) Rh, Pt, and Pd into the environment (1-3). This paper represents the first detailed study to assess the PGE content of soils and grasses from U.S. roadsides. These soils were analyzed using cation exchange pretreatment and ultrasonic nebulizer-ICP-MS (4). Highway and several urban sites showed Pt abundances of 64-73 ng/g immediately adjacent to the roadside, with corresponding Pd and Rh abundances of 18-31 ng/g and 3-7 ng/g, respectively. All Pt and most Pd and Rh abundances are statistically above local background soil values. Platinum, Rd, and Rh show positive correlations with traffic-related elements (Ni, Cu, Zn, and Pb) but no correlations with nontraffic-related elements (Y, Ga). Iridium and Ru show no correlations with any of these trace elements. These PGE abundances are comparable to European studies (5-7) and are approaching concentrations that would be economically viable to recover. This study also demonstrates transport of Pt statistically above background more than 50 m from the roadside. Further study is necessary to see how mobile the PGEs are in roadside environments, but these initial data indicate only Pt is taken up by plants.

Air Pollutants↗
PubMed2001

Biomass byproducts for the remediation of wastewaters contaminated with toxic metals.

Pollution of the environment with toxic metals is widespread and often involves large volumes of wastewater. Remediation strategies must be designed to support high throughput while keeping costs to a minimum. Biosorption is presented as an alternative to traditional physicochemical means for removing toxic metals from wastewater. We have investigated the metal binding qualities of two biomass byproducts that are commercially available in quantity and at low cost, namely "spillage", a dried yeast and plant mixture from the production of ethanol from corn, and ground corn cobs used in animal feeds. The biomass materials effectively removed toxic metals, such as Cu, Cs, Mo, Ni, Pb, and Zn, even in the presence of competing metals likely to be found in sulfide mine tailing ponds. The effectiveness of these biosorbents was demonstrated using samples from the Berkeley Pit in Montana. Investigations included column chromatography and slurry systems, and linear distribution coefficients are presented. X-ray spectroscopy was used to identify the binding sites for metals adsorbed to the spillage material. The results of our experiments demonstrate that the biosorption of metals from wastewaters using biomass byproducts is a viable and cost-effective technology that should be included in process evaluations.

Adsorption↗
PubMed1997

CELSS-3D: a broad computer model simulating a controlled ecological life support system.

CELSS-3D is a dynamic, deterministic, and discrete computer simulation of a controlled ecological life support system (CELSS) focusing on biological issues. A series of linear difference equations within a graphic-based modeling environment, the IThink program, was used to describe a modular CELSS system. The overall model included submodels for crop growth chambers, food storage reservoirs, the human crew, a cyanobacterial growth chamber, a waste processor, fixed nitrogen reservoirs, and the atmospheric gases, CO, O2, and N2. The primary process variable was carbon, although oxygen and nitrogen flows were also modeled. Most of the input data used in CELSS-3D were from published sources. A separate linear optimization program, What'sBest!, was used to compare options for the crew's vegetarian diet. CELSS-3D simulations were run for the equivalent of 3 years with a 1-h time interval. Output from simulations run under nominal conditions was used to illustrate dynamic changes in the concentrations of atmospheric gases. The modular design of CELSS-3D will allow other configurations and various failure scenarios to be tested and compared.

Atmosphere↗
PubMed1996

Evaluation of Cyanothece sp. ATCC 51142 as a candidate for inclusion in a CELSS.

Controlled ecological life support systems (CELSS) have been proposed to make long-duration manned space flights more cost-effective. Higher plants will presumably provide food and a breathable atmosphere for the crew. It has been suggested that imbalances between the CO2/O2 gas exchange ratios of the heterotrophic and autotrophic components of the system will inevitably lead to an unstable system, and the loss of O2 from the atmosphere. Ratio imbalances may be corrected by including a second autotroph with an appropriate CO2/O2 gas exchange ratio. Cyanothece sp. ATCC 51142 is a large unicellular N2-fixing cyanobacterium, exhibiting high growth rates under diverse physiological conditions. A rat-feeding study showed the biomass to be edible. Furthermore, it may have a CO2/O2 gas exchange ratio that theoretically can compensate for ratio imbalances. It is suggested that Cyanothece spp. could fulfill several roles in a CELSS: supplementing atmosphere recycling, generating fixed N from the air, providing a balanced protein supplement, and protecting a CELSS in case of catastrophic crop failure.

Air Conditioning↗
PubMed1996

Potential contribution of the diazotrophic cyanobacterium, Cyanothece sp. strain 51142, to a bioregenerative life support system.

Long-duration manned space missions will likely require the development of bioregenerative means of life support. Such a Controlled Ecological Life Support System (CELSS) would use higher plants to provide food and a breathable atmosphere for the crew and employ a waste processing system to recover elements for recycling. The current study identifies ways in which a cyanobacterial component may enhance the sustainability of a space-deployed CELSS, including balancing CO2/O2 gas exchange, production of bioavailable N, dietary supplementation, and contingency against catastrophic failure of the higher plant crops. Relevant quantitative data have been collected about the cyanobacterium, Cyanothece sp. strain ATCC 51142, a large, aerobic, unicellular diazotroph. This organism grew rapidly (466 g dry wt. m-3 d-1) and under diverse environmental conditions, was amenable to large-scale culture, could be grown with relative energy efficiency (3.8% conversion), could actively fix atmospheric N2 (35.0 g m-3 d-1), could survive extreme environmental insults, and exhibited gas exchange properties (assimilatory quotient of 0.49) that may be useful for correcting the gas exchange ratio imbalances observed between humans and higher plants. It is suggested that a diazotrophic cyanobacterium, like Cyanothece sp. strain ATCC 51142, may be a safe, effective, and renewable complement or alternative to physicochemical backup systems in a CELSS.

Air Conditioning↗
PubMed1996

A role for the diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142, in nitrogen cycling for CELSS applications.

Simple calculations show that fixed nitrogen regeneration in a CELSS may not be as efficient as stowage and resupply of fixed nitrogen compounds. However, fixed nitrogen regeneration may be important for the sustainability and safety of a deployed CELSS. Cyanothece sp. strain ATCC 51142, a unicellular, aerobic, diazotrophic cyanobacterium, with high growth rates and a robust metabolism, is a reasonable candidate organism for a biological, fixed nitrogen regeneration system. In addition, Cyanothece sp. cultures may be used to balance gas exchange ratio imparities between plants and humans. The regeneration of fixed nitrogen compounds by cyanobacterial cultures was examined in the context of a broad computer model/simulation (called CELSS-3D). When cyanothece sp. cultures were used to balance gas exchange imparities, the biomass harvested could supply as much as half of the total fixed nitrogen needed for plant biomass production.

Biomass↗
PubMed1995

Compositional and toxicological evaluation of the diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142.

Compositional analyses of Cyanothece sp. strain ATCC 51142 showed high protein (50-60%) and low fat (0.4-1%) content, and the ability to synthesize vitamin B12. The amino acid profile indicated that Cyanothece sp. was a balanced protein source. Fatty acids of the 18:3n-3 type were also present. Mineral analyses indicated that the cellular biomass may be a good source of Fe, Zn and Na. Caloric content was 4.5 to 5.1 kcal g dry weight-1 and the carbon content was approximately 40% on a dry weight basis. Nitrogen content was 8 to 9% on a dry weight basis and total nucleic acids were 1.3% on a dry weight basis. Short-term feeding studies in rats followed by histopathology found no toxicity or dietary incompatibility problems. The level of uric acid and allantoin in urine and tissues was low, suggesting no excess of nucleic acids, as sometimes reported in the past for a cyanobacteria-containing diet. The current work discusses the potential implications of these results for human nutrition applications.

Amino Acids↗
PubMed1995

Creating webservers on the Internet to advance CELSS research.

Effective integration of CELSS design concepts depends on the transfer of research results from studies performed in several disciplines and at many locations to all members of the CELSS community. Some of these appear in sources outside the mainstream scientific journals and are often difficult to acquire. The Internet offers a way to make these research results more accessible. The NSCORT in Bioregenerative Life Support at Purdue University has created a webserver on the Internet that provides information about the Purdue NSCORT, the NSCORT program, and CELSS design and development. Other CELSS-related webservers are needed, and a tutorial on webserver development is presented here. The Purdue NSCORT webserver is discussed in relation to other CELSS-related Internet projects. Future applications of the Internet in promoting CELSS research also are discussed.

Computer Communication Networks↗
PubMed1994

Oscillating behavior of carbohydrate granule formation and dinitrogen fixation in the cyanobacterium Cyanothece sp. strain ATCC 51142.

It has been shown that some aerobic, unicellular, diazotrophic cyanobacteria temporally separate photosynthetic O2 evolution and oxygen-sensitive N2 fixation. Cyanothece sp. ATCC strain 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that fixes N2 during discrete periods of its cell cycle. When the bacteria are maintained under diurnal light-dark cycles, N2 fixation occurs in the dark. Similar cycling is observed in continuous light, implicating a circadian rhythm. Under N2-fixing conditions, large inclusion granules form between the thylakoid membranes. Maximum granulation, as observed by electron microscopy, occurs before the onset of N2 fixation, and the granules decrease in number during the period of N2 fixation. The granules can be purified from cell homogenates by differential centrifugation. Biochemical analyses of the granules indicate that these structures are primarily carbohydrate, with some protein. Further analyses of the carbohydrate have shown that it is a glucose polymer with some characteristics of glycogen. It is proposed that N2 fixation is driven by energy and reducing power stored in these inclusion granules. Cyanothece sp. strain ATCC 51142 represents an excellent experimental organism for the study of the protective mechanisms of nitrogenase, metabolic events in cyanobacteria under normal and stress conditions, the partitioning of resources between growth and storage, and biological rhythms.

Carbohydrate Metabolism↗
PubMed1992

Origin of the chlorophyll b formyl oxygen in Chlorella vulgaris.

Chlorophyll (Chl) b is an accessory light-harvesting pigment of plants and chlorophyte algae. Chl b differs from Chl a in that the 3-methyl group on ring B of chl a is replaced by a 3-formyl group on Chl b. The present study determined the biosynthetic origin of the Chl b formyl oxygen in in vivo labeling experiments. A mutant strain of the unicellular chlorophyte Chlorella vulgaris, which can not synthesize Chls when cultured in the dark but rapidly greens when transferred to the light, was grown in the dark for several generations to deplete Chls, and then the cells were transferred to the light and allowed to form Chls in a controlled atmosphere containing 18O2. Chl a and Chl b were purified from the cells and analyzed by high-resolution mass spectroscopy. Analysis of the mass spectra indicated that over 76% of the Chl a molecules had incorporated an atom of 18O. For Chl b, 58% of the molecules had incorporated an atom of 18O at one position and 34% of the molecules had incorporated an atom of 18O at a second position. These results demonstrate that the isocyclic ring keto oxygen of both Chl a and Chl b, as well as the formyl oxygen of Chl b, is derived from O2.

Chlorella↗
PubMed1988

Characterization of the RNA Required for Biosynthesis of delta-Aminolevulinic Acid from Glutamate : Purification by Anticodon-Based Affinity Chromatography and Determination That the UUC Glutamate Anticodon Is a General Requirement for Function in ALA Biosynthesis.

The heme and chlorophyll precursor delta-aminolevulinic acid acid (ALA) is formed in plants and algae from glutamate in a process that requires at least three enzyme components plus a low molecular weight RNA which co-purifies with the tRNA fraction during DEAE-cellulose column chromatography. RNA that is effective in the in vitro ALA biosynthetic system was extracted from several plant and algal species that form ALA via this route. In all cases, the effective RNA contained the UUC glutamate anticodon, as determined by its specific retention on an affinity resin containing an affine ligand directed against this anticodon. Construction of the affinity resin was based on the fact that the UUC glutamate anticodon is complementary to the GAA phenylalanine anticodon. By covalently linking the 3' terminus of yeast tRNA(Phe(GAA)) to hydrazine-activated polyacrylamide gel beads, a resin carrying an affine ligand specific for the anticodon of tRNA(Glu(UUC)) was obtained. Column chromatography of plant and algal RNA extracts over this resin yielded a fraction that was highly enriched in the ability to stimulate ALA formation from glutamate when added to enzyme extracts of the unicellular green alga Chlorella vulgaris. Enhancement of ALA formation per A(260) unit added was as much as 50 times greater with the affinity-purified RNA than with the RNA before affinity purification. The affinity column selectively retained RNA which supported ALA formation upon chromatography of RNA extracts from species of the diverse algal groups Chlorophyta (Chlorella Vulgaris), Euglenophyta (Euglena gracilis), Rhodophyta (Cyanidium caldarium), and Cyanophyta (Synechocystis sp. PCC 6803), and a higher plant (spinach). Other glutamate-accepting tRNAs that were not retained by the affinity column were ineffective in supporting ALA formation. These results indicate that possession of the UUC glutamate anticodon is a general requirement for RNA to participate in the conversion of glutamate to ALA in plants and algae.

Journal Article↗
PubMed1988

The tRNA Required for in Vitro delta-Aminolevulinic Acid Formation from Glutamate in Synechocystis Extracts : Determination of Activity in a Synechocystis in Vitro Protein Synthesizing System.

RNA is an essential component for the enzymic conversion of glutamate to delta-aminolevulinic acid (ALA), the universal heme and chlorophyll precursor, as carried out in plants, algae, and some bacteria. The RNA required in this process was reported to bear a close structural resemblance to tRNA(Glu(UUC)), and it can be isolated by affinity chromatography directed against the UUC anticodon. Affinity-purified tRNA(Glu(UUC)) from the cyanobacterium Synechocystis sp. PCC 6803 was resolved into two major subfractions by reverse-phase HPLC. Only one of these was effectively charged with glutamate in enzyme extract from Synechocystis, but both were charged in Chlorella vulgaris enzyme extract. When charged with glutamate, the two glutamyl-tRNA(Glu(UUC)) species produced were equally effective in supporting both ALA formation and protein synthesis in vitro, as measured by label transfer from [(3)H]glutamyl-tRNA to ALA and protein. These results indicate that one of the two tRNA(Glu(UUC)) species is used by Synechocystis for both protein biosynthesis and ALA formation. Both of the tRNA(Glu(UUC)) subfractions from Synechocystis supported ALA formation in Chlorella enzyme extract. Escherichia coli tRNA(Glu(UUC)) was charged with glutamate, but did not support ALA formation in Synechocystis enzyme extract. Unfractionated tRNA from Chlorella, pea, and E. coli, having been charged with [(3)H] glutamate by Chlorella enzyme extract and then re-isolated, were all able to transfer label to proteins in the Synechocystis enzyme extract.

Journal Article↗
PubMed1986

Amino Acid Transport in Suspension-Cultured Plant Cells : VI. Influence of pH Buffers, Calcium, and Preincubation Media on l-Leucine Uptake.

The rate at which l-leucine was transported into suspension-cultured Nicotiana tabacum cv Wisconsin 38 cells increased more than 2-fold over a period of hours when the cells were preincubated in a 1% sucrose solution. This increase in uptake rate was eliminated if certain tris buffers were included in the preincubation solution while other buffers had little effect. Calcium could reverse the effect of the inhibitory buffers only if the buffer and calcium were present together from the beginning of the preincubation period. It was the amine group of the inhibitory buffers which was responsible for the inhibition. Preincubation in a complete culture medium (EM Linsmaier, F Skoog 1965 Physiol Plant 18: 100-127) led to minimal changes in l-leucine uptake rate over a 10 hour preincubation period indicating that the uptake rate was stabilized by this medium. The complete medium stabilized the l-leucine uptake rate as a result of its ionic composition and not because of its osmolarity. Most of the increased uptake rate observed after preincubation in a 1% sucrose solution could be inhibited by 2,4-dinitrophenol or carbonyl cyanide m-chlorophenyl hydrazone, or high concentrations of l-phenyl-alanine or l-leucine. Therefore much of the increase could be accounted for by an increase in active transport of l-leucine.

Journal Article↗
PubMed1986

Biosynthesis of protoheme and heme a from glutamate in maize.

The heme and chlorophyll precursor delta-aminolevulinic acid (ALA) can be formed by two biosynthetic routes: from the intact carbon skeleton of glutamate via a five-carbon pathway, which occurs in chloroplasts and bluegreen algae, and by ALA synthase-catalyzed condensation of succinyl-CoA and glycine, which occurs in bacteria and animal mitochondria. The biosynthetic route of plant mitochondrial heme a was determined by incubating terminal epicotyl sections of 8-day-old etiolated Zea mays seedlings in the dark with l-1-[(14)C]glutamate (which can be incorporated into ALA only via the five-carbon route) or 2-[(14)C]glycine (which would be incorporated via ALA synthase). Label incorporation was measured in highly purified protoheme and heme a. In 12-hour incubations, label uptake was greater than 70%. Total cellular protoheme was labeled 29.7 times more effectively by glutamate than glycine. Heme a was labeled 4.1 times more effectively by glutamate than by glycine. To assess the relative ability of the two amino acids to contribute label to the farnesyl moiety of heme a, label incorporation into total cellular nonsaponifiable lipids was measured. Glycine labeled this fraction 11.3 times more effectively than glutamate. Thus, a contribution by glycine to the farnesyl moiety may account for the small amount of label appearing in heme a. Our results indicate that in etiolated maize, noncovalently bound hemes, including mitochondrial heme a, are made mostly, and possibly entirely, from ALA synthesized via the five-carbon pathway. There is little or no contribution from ALA formed via ALA synthase, and no evidence was found for the operation of this enzyme in maize.

Journal Article↗
PubMedDate not supplied

Composition of the carbohydrate granules of the cyanobacterium, Cyanothece sp. strain ATCC 51142.

Cyanothece sp. strain ATCC 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that temporally separates O2-sensitive N2 fixation from oxygenic photosynthesis. The energy and reducing power needed for N2 fixation appears to be generated by an active respiratory apparatus that utilizes the contents of large interthylakoidal carbohydrate granules. We report here on the carbohydrate and protein composition of the granules of Cyanothece sp. strain ATCC 51142. The carbohydrate component is a glucose homopolymer with branches every nine residues and is chemically identical to glycogen. Granule-associated protein fractions showed temporal changes in the number of proteins and their abundance during the metabolic oscillations observed under diazotrophic conditions. There also were temporal changes in the protein pattern of the granule-depleted supernatant fractions from diazotrophic cultures. None of the granule-associated proteins crossreacted with antisera directed against several glycogen-metabolizing enzymes or nitrogenase, although these proteins were tentatively identified in supernatant fractions. It is suggested that the granule-associated proteins are structural proteins required to maintain a complex granule architecture.

1,4-alpha-Glucan Branching Enzyme↗