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R S Hanson

Publications and source records attributed to R S Hanson.

At least 19 recordsLinked to original sources
PubMed1997

Diabetes insipidus in pregnancy: a treatable cause of oligohydramnios.

BACKGROUND: Diabetes insipidus, which presents with polyuria, polydipsia, and profound electrolyte abnormalities, occurs rarely in pregnancy. We report a patient with severe oligohydramnios that resolved after treatment of diabetes insipidus. CASE: A 14-year-old girl was admitted at 33 weeks' gestation with cramping and vaginal spotting. A sonogram indicated oligohydramnios and an amniotic fluid index (AFI) of 2.6, with normal fetal kidneys and bladder. On hospital day 2, the AFI was 0.0. Recorded fluid was 8 L in and 13.6 L out. Serum sodium was 153 mEq/L. Diabetes insipidus was diagnosed and treated with intranasal desmopressin acetate. The oligohydramnios resolved rapidly, and the patient delivered a healthy 2700-g male infant at 38 weeks. CONCLUSION: Although rare, diabetes insipidus may present initially in pregnancy and should be considered in patients with oligohydramnios. Simple diagnosis with determination of 24-hour urine volume and serum electrolytes can identify this potentially reversible cause of oligohydramnios and poor obstetric outcome.

Adolescent↗
PubMed1997

Genetic manipulation of Bacillus methanolicus, a gram-positive, thermotolerant methylotroph.

We report the fist genetic transformation system, shuttle vectors, and integrative vectors for the thermotolerant, methylotrophic bacterium Bacillus methanolicus. By using a polyethylene glycol-mediated transformation procedure, we have successfully transformed B. methanolicus with both integrative and multicopy plasmids. For plasmids with a single BmeTI recognition site, dam methylation of plasmid DNA (in vivo or in vitro) was found to enhance transformation efficiency from 7- to 11-fold. Two low-copy-number Escherichia coli-B, methanolicus shuttle plasmids, pDQ507 and pDQ508, are described. pDQ508 caries the replication origin cloned from a 17-kb endogenous B. methanolicus plasmid, pBM1. pDQ507 carries a cloned B. methanolicus DNA fragment, pmr-1, possibly of chromosomal origin, that supports maintenance of pDQ507 as a circular, extrachromosomal DNA molecule. Deletion analysis of pDQ507 indicated two regions required for replication, i.e., a 90-bp AT-rich segment containing a 46-bp imperfect, inverted repeat sequence and a second region 65% homologous to the B. subtilis dpp operon. We also evaluated two E. coli-B. subtilis vectors, pEN1 and pHP13, for use as E. coli-B. methanolicus shuttle vectors. The plasmids pHP13, pDQ507, and pDQ508 were segregationally and structurally stable in B. methanolicus for greater than 60 generations of growth under nonselective conditions; pEN1 was segregationally unstable. Single-stranded plasmid DNA was detected in B. methanolicus transformants carrying either pEN1, pHP13, or pDQ508, suggesting that pDQ508, like the B. subtilis plasmids, is replicated by a rolling-circle mechanism. These studies provide the basic tools for the genetic manipulation of B. methanolicus.

Amino Acid Sequence↗
PubMed1996

Methanotrophic bacteria.

Methane-utilizing bacteria (methanotrophs) are a diverse group of gram-negative bacteria that are related to other members of the Proteobacteria. These bacteria are classified into three groups based on the pathways used for assimilation of formaldehyde, the major source of cell carbon, and other physiological and morphological features. The type I and type X methanotrophs are found within the gamma subdivision of the Proteobacteria and employ the ribulose monophosphate pathway for formaldehyde assimilation, whereas type II methanotrophs, which employ the serine pathway for formaldehyde assimilation, form a coherent cluster within the beta subdivision of the Proteobacteria. Methanotrophic bacteria are ubiquitous. The growth of type II bacteria appears to be favored in environments that contain relatively high levels of methane, low levels of dissolved oxygen, and limiting concentrations of combined nitrogen and/or copper. Type I methanotrophs appear to be dominant in environments in which methane is limiting and combined nitrogen and copper levels are relatively high. These bacteria serve as biofilters for the oxidation of methane produced in anaerobic environments, and when oxygen is present in soils, atmospheric methane is oxidized. Their activities in nature are greatly influenced by agricultural practices and other human activities. Recent evidence indicates that naturally occurring, uncultured methanotrophs represent new genera. Methanotrophs that are capable of oxidizing methane at atmospheric levels exhibit methane oxidation kinetics different from those of methanotrophs available in pure cultures. A limited number of methanotrophs have the genetic capacity to synthesize a soluble methane monooxygenase which catalyzes the rapid oxidation of environmental pollutants including trichloroethylene.

Base Sequence↗
PubMed1995

Nucleotide sequence of the mxcQ and mxcE genes, required for methanol dehydrogenase synthesis in Methylobacterium organophilum XX: a two-component regulatory system.

Nucleotide sequence analysis of the mxcQ and mxcE loci, required for the synthesis of methanol dehydrogenase in Methylobacterium organophilum XX, has revealed two open reading frames that show significant similarity to sequences of prokaryotic two-component systems, especially MxaY and MxaX proteins of another methylotrophic bacterium, Paracoccus denitrificans. Cell-free extracts and DNA-column-fractionated proteins from wild-type M. organophilum XX cells grown on methanol or succinate contained protein(s) that were able to bind specifically to the upstream region of methanol dehydrogenase large subunit gene (mxaF). In contrast, cell-free extracts from mxcQ and mxcE mutant strains of M. organophilum XX had zero or reduced binding activity towards the promoter fragments of the mxaF gene. This is consistent with the involvement of the mxcQ and mxcE genes in transcriptional regulation of methanol dehydrogenase synthesis. Analyses of sequential deletions of the mxaF upstream region have defined the functional boundary of the promoter/operator region of this gene and identified one nucleotide segment as essential to the activation of mxaF.

Alcohol Oxidoreductases↗
PubMed1994

New unified nomenclature for genes involved in the oxidation of methanol in gram-negative bacteria.

The system involving the oxidation of methanol to formaldehyde in Gram-negative methylotrophic bacteria is complex. A total of 32 genes have been reported, termed mox, for methanol oxidation, and it is possible that more will be identified. Some mox genes carrying out completely different functions have been given the same designations by different laboratories and others have been given separate designations that were later discovered to be the same. It is now important to change the mox nomenclature to remedy this confusing situation. This communication proposes a new nomenclature for genes involved in methanol oxidation based on currently known linkage groups.

Genes, Bacterial↗
PubMed1994

Double-stranded cleavage of pBR322 by a diiron complex via a "hydrolytic" mechanism.

Treatment of plasmid pBR322 with Fe2-(HPTB)(OH)(NO3)4(HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopr opane) and H2O2 or O2 and a reductant (dithiothreitol or ascorbate) results in double-stranded cleavage of the plasmid. The linearization of supercoiled pBR322 by this complex is not inhibited by hydroxyl radical scavengers. On the other hand, the linearized pBR322 is efficiently religated by T4 DNA ligase, and the presence of 3'-OH and 5'-OPO3 ends is corroborated by 3'- and 5'-end-labeling studies. These observations indicate that cleavage results from hydrolysis of the DNA-phosphate backbone, which is proposed to occur by nucleophilic attack of the bound peroxide on the phosphodiester. Double-stranded cleavage by the Fe2(HPTB)(OH)(NO3)4/H2O2 adduct preferentially occurs between bp 3489 and 3485 of pBR322.

Base Sequence↗
PubMed1994

Phylogenetic analysis and development of probes for differentiating methylotrophic bacteria.

Fifteen small-subunit rRNAs from methylotrophic bacteria have been sequenced. Comparisons of these sequences with 22 previously published sequences further defined the phylogenetic relationships among these bacteria and illustrated the agreement between phylogeny and physiological characteristics of the bacteria. Phylogenetic trees were constructed with 16S rRNA sequences from methylotrophic bacteria and representative organisms from subdivisions within the class Proteobacteria on the basis of sequence similarities by using a weighted least-mean-square difference method. The methylotrophs have been separated into coherent clusters in which bacteria shared physiological characteristics. The clusters distinguished bacteria which used either the ribulose monophosphate or serine pathway for carbon assimilation. In addition, methanotrophs and methylotrophs which do not utilize methane were found to form distinct clusters within these groups. Five new deoxyoligonucleotide probes were designed, synthesized, labelled with digoxigenin-11-ddUTP, and tested for the ability to hybridize to RNA extracted from the bacteria represented in the unique clusters and for the ability to detect RNAs purified from soils enriched for methanotrophs by exposure to a methane-air atmosphere for one month. The 16S rRNA purified from soil hybridized to the probe which was complementary to sequences present in 16S rRNA from serine pathway methanotrophs and hybridized to a lesser extent with a probe complementary to sequences in 16S rRNAs of ribulose monophosphate pathway methanotrophs. The nonradioactive detection system used performed reliably at amounts of RNA from pure cultures as small as 10 ng.

Base Sequence↗
PubMed1993

Identification of methanol-regulated promoter sequences from the facultative methylotrophic bacterium Methylobacterium organophilum XX.

A promoter-probe vector (pHX200) was constructed using the broad-host-range cosmid pLA2917 and a promoterless xylE gene of Pseudomonas as the reporter gene. Insertion of the cloned promoter fragment of the methanol dehydrogenase large subunit gene moxF (methanol oxidation) in front of the xylE gene in pHX200V-47 resulted in high-level expression of the xylE gene product--catechol 2,3-dioxygenase--in Methylobacterium organophilum XX. The specific activity of the enzyme was four times higher in methanol-grown M. organophilum XX culture than in succinate-grown culture. Interestingly, the insertion of the same fragment in the opposite orientation in front of the xylE gene (pHX200V-74) also led to elevated catechol 2,3-dioxygenase activity. This promoter activity was also methanol regulated. A total of 21 methanol-regulated promoter clones were identified that originate from three gene clusters (groups V, VI and VII) on the M. organophilum XX chromosome involved in methanol oxidation. Vector pHX200 and its derivatives were successfully mobilized into cells of three phylogenetically diverse methylotrophic bacteria: Methylophilus methylotrophus AS1, Methylobacterium extorquens AM1 and Methylobacterium sp. DM4. The reporter gene (xylE) was functionally expressed in all three bacteria with the aid of a proper promoter. Transcriptional fusions of methanol-regulated promoters with the xylE gene were mobilized into Mox- mutants of M. organophilum XX and M. extorquens AM1 to study the roles of methanol oxidation genes, especially regulatory genes. It appeared that vector pHX200 is an efficient promoter probe with wide host-range and an excellent tool for studies of structure and function of promoters/regulators.

Base Sequence↗
PubMed1993

Isolation and characterization of an N-methylcarbamate insecticide-degrading methylotrophic bacterium.

A gram-negative bacterium which hydrolyzed aryl N-methylcarbamate insecticides was isolated from an agricultural soil which quickly degraded these pesticides. This organism, designated strain ER2, grew on carbofuran as a sole source of carbon and nitrogen with a doubling time of 3 h in a mineral salts medium. The aromatic nucleus of the molecule was not metabolized, and carbofuran 7-phenol accumulated as the end product of metabolism. The insecticides carbaryl, bendiocarb, and propoxur were similarly hydrolyzed, with each yielding the corresponding phenol. Strain ER2 contained two plasmids (120 and 130 kb). A probe cloned from the pDL11 plasmid of Achromobacter sp. strain WM111, which encodes the carbofuran hydrolase (mcd) gene (P. H. Tomasek and J. S. Karns, J. Bacteriol. 171:4038-4044, 1989), hybridized to the 120-kb plasmid. Restriction fragment profiles of pDL11 and strain ER2 plasmid DNAs suggested that the 120-kb plasmid of strain ER2 is very similar to pDL11. On the basis of the results of biochemical tests, 16S rRNA sequence analysis, and membrane lipid analyses, strain ER2 was found to be a phylogenetically unique type II methylotroph. The constitutive carbofuran hydrolase activity in glucose-grown cells increased sevenfold when strain ER2 was grown in the presence of 100 mg of carbofuran per liter as the sole source of carbon and nitrogen or as the sole nitrogen source in the presence of glucose. Growth on carbofuran resulted in the induction of enzymes required for methylamine-dependent respiration and the serine pathway of formaldehyde assimilation. These results indicate that the carbofuran hydrolase mcd gene is conserved on a plasmid found in organisms from different geographic areas and that the specific activity of carbofuran degradation may increase in response to carbofuran treatment.

Alcaligenes↗
PubMed1992

Use of 16S rRNA analysis to investigate phylogeny of methylotrophic bacteria.

Small-subunit rRNAS from 24 gran-negative methylotropic bacteria have been sequenced. A phylogenetic tree was constructed on the basis of sequence similarities by using a weighted least-mean-square difference method. The methylotrophs were separated into coherent clusters in which bacteria in each group shared physiological characteristics.

Bacterial Typing Techniques↗
PubMed1992

Cloning and nucleotide sequence of the gene coding for citrate synthase from a thermotolerant Bacillus sp.

The structural gene coding for citrate synthase from the gram-positive soil isolate Bacillus sp. strain C4 (ATCC 55182) capable of secreting acetic acid at pH 5.0 to 7.0 in the presence of dolime has been cloned from a genomic library by complementation of an Escherichia coli auxotrophic mutant lacking citrate synthase. The nucleotide sequence of the entire 3.1-kb HindIII fragment has been determined, and one major open reading frame was found coding for citrate synthase (ctsA). Citrate synthase from Bacillus sp. strain C4 was found to be a dimer (Mr, 84,500) with a subunit with an Mr of 42,000. The N-terminal sequence was found to be identical with that predicted from the gene sequence. The kinetics were best fit to a bisubstrate enzyme with an ordered mechanism. Bacillus sp. strain C4 citrate synthase was not activated by potassium chloride and was not inhibited by NADH, ATP, ADP, or AMP at levels up to 1 mM. The predicted amino acid sequence was compared with that of the E. coli, Acinetobacter anitratum, Pseudomonas aeruginosa, Rickettsia prowazekii, porcine heart, and Saccharomyces cerevisiae cytoplasmic and mitochondrial enzymes.

Amino Acid Sequence↗
PubMed1992

Soluble methane monooxygenase component B gene probe for identification of methanotrophs that rapidly degrade trichloroethylene.

Restriction fragment length polymorphisms, Western blot (immunoblot) analysis, and fluorescence-labelled signature probes were used for the characterization of methanotrophic bacteria as well as for the identification of methanotrophs which contained the soluble methane monooxygenase (MMO) gene and were able to degrade trichloroethylene (TCE). The gene encoding a soluble MMO component B protein from Methylosinus trichosporium OB3b was cloned. It contained a 2.2-kb EcoRI fragment. With this cloned component B gene as probe, methanotroph types I, II, and X and environmental and bioreactor samples were screened for the presence of the gene encoding soluble MMO. Fragments produced by digestion of DNA with rare cutting restriction endonucleases were separated by pulsed-field gel electrophoresis and transferred to Zeta-Probe membrane (Bio-Rad) for Southern blot analysis. Samples were also analyzed for the presence of soluble MMO by Western blot analysis and the ability to degrade TCE. The physiological groups of methanotrophs in each sample were determined by hybridizing cells with fluorescence-labelled signature probes. Among twelve pure or mixed cultures, DNA fragments of seven methanotrophs hybridized with the soluble MMO B gene probe. When grown in media with limited copper, all of these bacteria degraded TCE. All of them are type II methanotrophs. The soluble MMO component B gene of the type X methanotroph, Methylococcus capsulatus Bath, did not hybridize to the M. trichosporium OB3b soluble MMO component B gene probe, although M. capsulatus Bath also produces a soluble MMO.

Base Sequence↗
PubMed1992

Characterization of a methane-utilizing bacterium from a bacterial consortium that rapidly degrades trichloroethylene and chloroform.

A mixed culture of bacteria grown in a bioreactor with methane as a carbon and energy source rapidly oxidized trichloroethylene and chloroform. The most abundant organism was a crescent-shaped bacterium that bound the fluorescent oligonucleotide signature probes that specifically hybridize to serine pathway methylotrophs. The 5S rRNA from this bacterium was found to be 93.5% homologous to the Methylosinus trichosporium OB3b 5S RNA sequence. A type II methanotrophic bacterium, isolated in pure culture from the bioreactor, synthesized soluble methane monooxygenase during growth in a copper-limited medium and was also capable of rapid trichloroethylene oxidation. The bacterium contained the gene that encodes the soluble methane monooxygenase B component on an AseI restriction fragment identical in size to a restriction fragment present in AseI digests of DNA from bacteria in the mixed culture. The sequence of the 16S rRNA from the pure culture was found to be 92 and 94% homologous to the 16S rRNAs of M. trichosporium OB3b and M. sporium, respectively. Both the pure and mixed cultures oxidized naphthalene to naphthol, indicating the presence of soluble methane monooxygenase. The mixed culture also synthesized soluble methane monooxygenase, as evidenced by the presence of proteins that cross-reacted with antibodies prepared against purified soluble methane monooxygenase components from M. trichosporium OB3b on Western blots (immunoblots). It was concluded that a type II methanotrophic bacterium phylogenetically related to Methylosinus species synthesizes soluble methane monooxygenase and is responsible for trichloroethylene oxidation in the bioreactor.

Base Sequence↗
PubMed1991

Membrane fatty acids as phenotypic markers in the polyphasic taxonomy of methylotrophs within the Proteobacteria.

A polyphasic approach to bacterial taxonomy attempts to integrate phylogenetic relationships with phenotypic marker analysis. This study describes the application of membrane fatty acids as a phenotypic marker for methylotrophs. Detailed phospholipid, ester-linked fatty acid (PLFA) profiles are reported for 17 methylotrophic eubacterial strains. These profiles included verification of double bond positions and geometries, both critical features for this analysis. Multivariate cluster analysis was used to indicate groupings of these strains along with literature values of both methylotrophs and non-methylotrophs based on the PLFA phenotype. Like many phenotypic characteristics, PLFA profiles were influenced by environmental conditions. The instabilities displayed, however, were predictable from physiological studies including increased trans/cis and cyclopropyl/cis ratios. Cluster analysis of PLFA profiles generated by separate investigators with different culture conditions indicated reproducibility by strain and species. The PLFA phenotype relationships compare favourably with phylogenetic associations based on 16S rRNA data for methylotrophs and will continue to be a valuable phenotypic marker for Proteobacteria taxonomy.

Cell Membrane↗
PubMed1990

Optimization of trichloroethylene oxidation by methanotrophs and the use of a colorimetric assay to detect soluble methane monooxygenase activity.

Methylosinus trichosporium OB3b biosynthesizes a broad specificity soluble methane monooxygenase that rapidly oxidizes trichloroethylene (TCE). The selective expression of the soluble methane monooxygenase was followed in vivo by a rapid colorimetric assay. Naphthalene was oxidized by purified soluble methane monooxygenase or by cells grown in copper-deficient media to a mixture of 1-naphthol and 2-naphthol. The naphthols were detected by reaction with tetrazotized o-dianisidine to form purple diazo dyes with large molar absorptivities. The rate of color formation with the rapid assay correlated with the velocity of TCE oxidation that was determined by gas chromatography. Both assays were used to optimize conditions for TCE oxidation by M. trichosporium OB3b and to test several methanotrophic bacteria for the ability to oxidize TCE and naphthalene.

Biodegradation, Environmental↗
PubMed1990

16S ribosomal RNA sequence analysis for determination of phylogenetic relationship among methylotrophs.

16S ribosomal RNAs (rRNA) of 12 methylotrophic bacteria have been almost completely sequenced to establish their phylogenetic relationships. Methylotrophs that are physiologically related are phylogenetically diverse and are scattered among the purple eubacteria (class Proteobacteria). Group I methylotrophs can be classified in the beta- and the gamma-subdivisions and group II methylotrophs in the alpha-subdivision of the purple eubacteria, respectively. Pink-pigmented facultative and non-pigmented obligate group II methylotrophs form two distinctly separate branches within the alpha-subdivision. The secondary structures of the 16S rRNA sequences of 'Methylocystis parvus' strain OBBP, 'Methylosinus trichosporium' strain OB3b, 'Methylosporovibrio methanica' strain 81Z and Hyphomicrobium sp. strain DM2 are similar, and these non-pigmented obligate group II methylotrophs form one tight cluster in the alpha-subdivision. The pink-pigmented facultative methylotrophs, Methylobacterium extorquens strain AM1, Methylobacterium sp. strain DM4 and Methylobacterium organophilum strain XX form another cluster within the alpha-subdivision. Although similar in phenotypic characteristics, Methylobacterium organophilum strain XX and Methylobacterium extorquens strain AM1 are clearly distinguishable by their 16S rRNA sequences. The group I methylotrophs, Methylophilus methylotrophus strain AS1 and methylotrophic species DM11, which do not utilize methane, are similar in 16S rRNA sequence to bacteria in the beta-subdivision. The methane-utilizing, obligate group I methanotrophs, Methylococcus capsulatus strain BATH and Methylomonas methanica, are placed in the gamma-subdivision. The results demonstrate that it is possible to distinguish and classify the methylotrophic bacteria using 16S rRNA sequence analysis.

Base Sequence↗