bluuebunny/crossref_metadata_2025 huggingface dataset:
Unaltered Nodulation Competitiveness of a Strain of
Bradyrhizobium
sp. (
Lotus
) after a Decade in Soil
Authors: Lochner Hester H. , Strijdom Barend W. , Law Ian J.
Published: January 2020

A
Bradyrhizobium
sp. (
Lotus
) strain that formed a soil population that was highly competitive for nodulation of
Lotus pedunculatus
11 years after its introduction into a field soil and a culture of the same strain stored lyophilized were compared with an antibiotic-resistant mutant in respect of their nodulation competitiveness. The mutant was less competitive than the wild-type strain it was isolated from and had to be present at a cell ratio of 5.76:1 in mixed inoculum in sand culture to form 50% of the nodules on
L. pedunculatus
(50% nodulation value, 5.76). The 50% nodulation values for a soil population of the mutant mixed with soil populations of the lyophilized and field soil strain were, respectively, 6.83 and 5.77, indicating that the field soil strain was not significantly different from the lyophilized strain in nodulation competitiveness. A 50% nodulation value of 11.18 obtained when soil containing a recently established mutant population was mixed with the field soil containing the population established 11 years before, indicating that the plant infection technique underestimated cell numbers of the field soil population by 100%. Nodulation competitiveness was unaffected by the size of the strain populations in the range of 100 to 1,000 cells per g of soil; at 10 cells per g a significant correlation between strain ratios in nodules and in soil was still evident. The results indicated that apparently superior nodulation competitiveness of a well-established soil population relative to that of a subsequently introduced strain may not necessarily reflect the intrinsic competitive abilites of the strain(s) involved. The soil strain did not differ from laboratory-maintained cultures in antigenic properties, effectiveness, or whole cell protein electrophoresis profiles.
High Efficiency of Plating of the Thermophilic Sulfur-Dependent Archaebacterium
Sulfolobus acidocaldarius
Authors: Lindström E. Börje , Sehlin H. Mikael
Published: January 2020

A procedure for plating
Sulfolobus acidocaldarius
using Gelrite as the gelling agent is presented. The technique uses a supporting gel of 0.8% (wt/vol) Gelrite and an overlay soft gel of 0.4% (wt/vol) Gelrite, in which the colonies are grown. The plating efficiency was essentially 100%.
Detection in soil of a deletion in an engineered DNA sequence by using DNA probes
Authors: Jansson J K , Holben W E , Tiedje J M
Published: January 2020

Two Pseudomonas strains were engineered to contain the nptII gene and plasmid vector sequences in their chromosomes. After incubation of these strains in nonsterile soil, total bacterial DNA was isolated and analyzed by Southern blot hybridization with the nptII gene and the plasmid vector as probes. In addition to the expected bands of hybridization, a new band corresponding to the loss of vector sequences from the chromosome while retaining the nptII gene was observed for one of the strains. The more stressful conditions encountered in soil appeared to increase the frequency of loss of the vector sequences from this strain.
O dealkylation and aliphatic and aromatic hydroxylation of 3-methoxy-17 beta-estradiol by Aspergillus alliaceus
Authors: Williamson J S , Van Orden D E , Rosazza J P
Published: January 2020

Aspergillus alliaceus UI 315 was examined for its ability to metabolize 3-methoxy-17 beta-estradiol. Preparative-scale incubations with this substrate afforded good yields of 6 beta-hydroxy-17 beta-estradiol, 4-hydroxy-17 beta-estradiol, and 4,6 beta-dihydroxy-17 beta-estradiol, which were identified by high-pressure liquid chromatography, 1H and 13C nuclear magnetic resonance, and high-resolution mass spectrometry.
Characterization of a plasmid from the ruminal bacterium Selenomonas ruminantium
Authors: Martin S A , Dean R G
Published: January 2020

A 4.8-kilobase-pair plasmid was isolated from the ruminal bacterium selenomonas ruminantium HD4 by using a sodium carbonate-EDTA washing buffer to improve cell lysis (R.G. Dean, S.A. Martin, and C. Carver, Lett. Appl. Microbiol. 8:45-48, 1989). This plasmid, designated pSR1, appears to be quite stable. No evidence of plasmid DNA was detected in S. ruminantium D or GA192. All three strains were tested for antibiotic resistance, and all were kanamycin resistant (MIC, 25 to 50 micrograms/ml). Only strain D was tetracycline resistant (MIC, 25 micrograms/ml), and all strains were sensitive to ampicillin (MIC, 1 microgram/ml). pSR1 was cloned into pBR322, and a map of pSR1 was constructed by using HindIII, ClAI, BamHI, and PvuII. Although ClaI, BamHI, ScaI, and EcoRV digested recombined plasmid isolated from Escherichia coli, these restriction endonucleases were not effective in digesting plasmid isolated directly from S. ruminantium HD4.
Factors affecting adhesion of Fibrobacter succinogenes subsp. succinogenes S85 and adherence-defective mutants to cellulose
Authors: Gong J , Forsberg C W
Published: January 2020

Fibrobacter succinogenes subsp. succinogenes S85, formerly Bacteroides succinogenes, adheres to crystalline cellulose present in the culture medium. When the cells are suspended in buffer, adhesion is enhanced by increasing the ionic strength. Heat, glutaraldehyde, trypsin, and pronase treatments markedly reduce the extent of adhesion. Treatment with dextrinase, modification of amino and carboxyl groups with Formalin or other chemical agents, and inclusion of either albumin (1%) or Tween 80 (0.5%) do not decrease the degree of adhesion. Adherence-defective mutants isolated by their inability to bind to cellulose exhibited different growth characteristics. Class 1 mutants grew on glucose, cellobiose, amorphous cellulose, and crystalline cellulose. Class 3 mutants grew on glucose and cellobiose but not on amorphous or crystalline cellulose. No substantial changes were detected in the endoglucanase, cellobiosidase, and cellobiase activities of the wild type and the mutants. These data suggest that adhesion to crystalline cellulose is specific and that it involves surface proteins.
Efficacy of copper and silver ions and reduced levels of free chlorine in inactivation of Legionella pneumophila
Authors: Landeen L K , Yahya M T , Gerba C P
Published: January 2020

Water disinfection systems utilizing electrolytically generated copper and silver ions (200 and 20, 400 and 40, or 800 and 80 micrograms/liter) and low levels of free chlorine (0.1 to 0.4 mg/liter) were evaluated at room (21 to 23 degrees C) and elevated (39 to 40 degrees C) temperatures in filtered well water (pH 7.3) for their efficacy in inactivating Legionella pneumophila (ATCC 33155). At room temperature, a contact time of at least 24 h was necessary for copper and silver (400 and 40 micrograms/liter) to achieve a 3-log10 reduction in bacterial numbers. As the copper and silver concentration increased to 800 and 80 micrograms/liter, the inactivation rate significantly (P less than or equal to 0.05) increased from K = 2.87 x 10(-3) to K = 7.50 x 10(-3) (log10 reduction per minute). In water systems with and without copper and silver (400 and 40 micrograms/liter), the inactivation rates significantly increased as the free chlorine concentration increased from 0.1 mg/liter (K = 0.397 log10 reduction per min) to 0.4 mg/liter (K = 1.047 log10 reduction per min). Compared to room temperature, no significant differences were observed when 0.2 mg of free chlorine per liter with and without 400 and 40 micrograms of copper and silver per liter was tested at 39 to 40 degrees C. All disinfection systems, regardless of temperature or free chlorine concentration, showed increase inactivation rates when 400 and 40 micrograms of copper and silver per liter was added; however, this trend was significant only at 0.4 mg of free chlorine per liter.
Survival of Vibrio vulnificus in shellstock and shucked oysters (Crassostrea gigas and Crassostrea virginica) and effects of isolation medium on recovery
Authors: Kaysner C A , Tamplin M L , Wekell M M , Stott R F , Colburn K G
Published: January 2020

When two species of shellstock oysters were artificially contaminated with Vibrio vulnificus, the bacterium survived when the oysters were stored at 10 degrees C and below. Large numbers of endogenous V. vulnificus cells were found after 7 days at both 0.5 and 10 degrees C in uninoculated control oysters (Crassostrea virginica). Oysters allowed to take up V. vulnificus from seawater retained the bacterium for 14 days at 2 degrees C. The presence of V. vulnificus in the drip exuded from the shellstock presented a possibility of contamination of other shellstock in storage. V. vulnificus injected into shucked Pacific (Crassostrea gigas) and Eastern (C. virginica) oysters survived at 4 degrees C for at least 6 days. An 18-h most-probable-number enrichment step in alkaline peptone water gave higher recovery levels of V. vulnificus than did direct plating to selective agars. The survival of this pathogen in both shellstock and shucked oysters suggests a potential for human illness, even though the product is refrigerated.
Induction and Purification of Endo-β-
N
-Acetylglucosaminidase from
Arthrobacter protophormiae
Grown in Ovalbumin
Authors: Takegawa Kaoru , Nakoshi Masanao , Iwahara Shojiro , Yamamoto Kenji , Tochikura Tatsurokuro
Published: January 2020

Arthrobacter protophormiae
produced a high level of extracellular endo-β-
N
-acetylglucosaminidase when cells were grown in a medium containing ovalbumin. The enzyme was induced by the glycopeptide fraction of ovalbumin prepared by pronase digestion. Production of the enzyme was also induced by glycoproteins such as yeast invertase and bovine ribonuclease B but not by monosaccharides such as mannose,
N
-acetylglucosamine, and galactose. The enzyme was purified to homogeneity as demonstrated by polyacrylamide gel electrophoresis and has an apparent molecular weight of about 80,000. The enzyme showed a broad optimum pH in the range of pH 5.0 to 11.0. The enzyme hydrolyzed all heterogeneous ovalbumin glycopeptides, although the hydrolysis rates for hybrid type glycopeptides were very low. The substrate specificity of
A. protophormiae
endo-β-
N
-acetylglucosaminidase was very similar to that of Endo-C
II
from
Clostridium perfringens.
Therefore, the enzyme induction by
A. protophormiae
seems to have a close relation to the substrate specificity of the enzyme.
Organization of Genes Required for the Oxidation of Methanol to Formaldehyde in Three Type II Methylotrophs
Authors: Bastien C. , Machlin S. , Zhang Y. , Donaldson K. , Hanson R. S.
Published: January 2020

Restriction maps of genes required for the synthesis of active methanol dehydrogenase in
Methylobacterium organophilum
XX and
Methylobacterium
sp. strain AM1 have been completed and compared. In these two species of pink-pigmented, type II methylotrophs, 15 genes were identified that were required for the expression of methanol dehydrogenase activity. None of these genes were required for the synthesis of the prosthetic group of methanol dehydrogenase, pyrroloquinoline quinone. The structural gene required for the synthesis of cytochrome
c

L

, an electron acceptor uniquely required for methanol dehydrogenase, and the genes encoding small basic peptides that copurified with methanol dehydrogenases were closely linked to the methanol dehydrogenase structural genes. A cloned 22-kilobase DNA insert from
Methylsporovibrio methanica
81Z, an obligate type II methanotroph, complemented mutants that contained lesions in four genes closely linked to the methanol dehydrogenase structural genes. The methanol dehydrogenase and cytochrome
c

L

structural genes were found to be transcribed independently in
M. organophilum
XX. Only two of the genes required for methanol dehydrogenase synthesis in this bacterium were found to be cotranscribed.
Biodegradation of trichloroethylene by Methylosinus trichosporium OB3b
Authors: Tsien H C , Brusseau G A , Hanson R S , Waclett L P
Published: January 2020

The methanotroph Methylosinus trichosporium OB3b, a type II methanotroph, degraded trichloroethylene at rates exceeding 1.2 mmol/h per g (dry weight) following the appearance of soluble methane monooxygenase in continuous and batch cultures. Cells capable oxidizing trichloroethylene contained components of soluble methane monooxygenase as demonstrated by Western blot (immunoblot) analysis with antibodies prepared against the purified enzyme. Growth of cultures in a medium containing 0.25 microM or less copper sulfate caused derepression of the synthesis of soluble methane monooxygenase. In these cultures, the specific rates of methane and methanol oxidation did not change during growth, while trichloroethylene oxidation increased with the appearance of soluble methane monooxygenase. M. trichosporium OB3b cells that contained soluble methane monooxygenase also degraded vinyl chloride, 1,1-dichloroethylene, cis-1,2-dichloroethylene, and trans-1,2-dichloroethylene.
Cloning and characterization of two genes from Bacillus polymyxa expressing beta-glucosidase activity in Escherichia coli
Authors: González-Candelas L , Aristoy M C , Polaina J , Flors A
Published: January 2020

DNA fragments from Bacillus polymyxa which encode beta-glucosidase activity were cloned in Escherichia coli by selection of yellow transformants able to hydrolyze the artificial chromogenic substrate p-nitrophenyl-beta-D-glucopyranoside. Restriction endonuclease maps and Southern analysis of the cloned fragments showed the existence of two different genes. Expression of either one of these genes allowed growth of E. coli in minimal medium with cellobiose as the only carbon source. One of the two enzymes was found in the periplasm of E. coli, hydrolyzed arylglucosides more actively than cellobiose, and rendered glucose as the only product upon cellobiose hydrolysis. The other enzyme was located in the cytoplasm, was more active toward cellobiose, and hydrolyzed this disaccharide, yielding glucose and another, unidentified compound, probably a phosphorylated sugar.
Evaluation of immunofluorescence techniques for detection of Cryptosporidium oocysts and Giardia cysts from environmental samples
Authors: Rose J B , Landeen L K , Riley K R , Gerba C P
Published: January 2020

Cryptosporidium and Giardia species are enteric protozoa which cause waterborne disease. The detection of these organisms in water relies on the detection of the oocyst and cyst forms or stages. Monoclonal and polyclonal antibodies were compared for their abilities to react with Giardia cysts and Cryptosporidium oocysts after storage in water, 3.7% formaldehyde, and 2.5% potassium dichromate, upon exposure to bleach, and in environmental samples. Three monoclonal antibodies to Cryptosporidium parvum were evaluated. Each test resulted in an equivalent detection of the oocysts after storage, after exposure to bleach, and in environmental samples. Oocyst levels declined slightly after 20 to 22 weeks of storage in water, and oocyst fluorescence and morphology were dull and atypical. Oocyst counts decreased after exposure to 2,500 mg of sodium hypochlorite per liter, and fluorescence and phase-contrast counts were similar. Sediment due to algae and clays found in environmental samples interfered with the detection of oocysts on membrane filters. Two monoclonal antibodies and a polyclonal antibody directed against Giardia lamblia cysts were evaluated. From the same seeded preparations, significantly greater counts were obtained with the polyclonal antibody. Of the two monoclonal antibodies, one resulted in significantly lower cyst counts. In preliminary studies, the differences between antibodies were not apparent when used on the environmental wastewater samples. After 20 to 22 weeks in water, cyst levels declined significantly by 67%. Cysts were not detected with monoclonal antibodies after exposure to approximately 5,000 mg of sodium hypochlorite per liter.
Toxicity of Microcystis species isolated from natural blooms and purification of the toxin
Authors: Ohtake A , Shirai M , Aida T , Mori N , Harada K , Matsuura K , Suzuki M , Nakano M
Published: January 2020

Microcystis strains (2 toxic and 18 nontoxic to mice) were isolated from toxic waterblooms that had been collected from Lake Kasumigaura, Ibaraki Prefecture, Japan, in August 1985. Thirteen of the strains (2 toxic and 11 nontoxic) were Microcystis aeruginosa, 2 (nontoxic) were Microcystis wesenbergii, and the other 5 were difficult to identify. Six (1 toxic and 4 nontoxic M. aeruginosa and 1 M. wesenbergii) of these 20 strains were established as axenic cultures. A toxic and axenic strain of M. aeruginosa, K-139, was used to study the relationship between growth conditions and toxicity. Cells in early-to-mid-log phase showed the highest toxicity (50% lethal dose, 7.5 mg of cells per kg of mouse), and maximum toxicity was not affected by growth temperatures between 22 and 30 degrees C. Purification and characterization of the toxins from K-139 cells were also conducted, and at least two toxins were detected. One of the toxins (molecular mass, 980 daltons) has not been reported previously. The main target of the toxin in mice was the liver. Marked congestion and necrosis in the parenchymal cells around the central veins of the liver were observed microscopically in specimens that had been prepared from the mice with acute toxicity after injection with the toxin.
Host Restriction and Transduction in
Rhizobium meliloti
Authors: Williams Myron N. V. , Klein Shoshana , Signer Ethan R.
Published: January 2020

A host restriction difference exists between
Rhizobium meliloti
Rm41 and SU47 exists as indicated by the reduce plating efficiency of transducing phage ΦM12h1. Restriction can be attenuated by incubating cells at 42°C for 3 h; this procedure overcomes a block to transduction from SU47 to Rm41.
Requirement for a Microbial Consortium To Completely Oxidize Glucose in Fe(III)-Reducing Sediments
Authors: Lovley Derek R. , Phillips Elizabeth J. P.
Published: January 2020

In various sediments in which Fe(III) reduction was the terminal electron-accepting process, [
14
C]glucose was fermented to
14
C-fatty acids in a manner similar to that observed in methanogenic sediments. These results are consistent with the hypothesis that, in Fe(III)-reducing sediments, fermentable substrates are oxidized to carbon dioxide by the combined activity of fermentative bacteria and fatty acid-oxidizing, Fe(III)-reducing bacteria.
Development of enterobacterium-specific oligonucleotide probes based on the surface-exposed regions of outer membrane proteins
Authors: Spierings G , Hofstra H , Huis in'T Veld J , Hoekstra W , Tommassen J
Published: January 2020

Outer membrane proteins of members of the family Enterobacteriaceae consist of conserved membrane-spanning segments and hypervariable, surface-exposed regions. We demonstrate that the hypervariable DNA segments corresponding to the surface-exposed regions of these proteins can be used to develop specific DNA probes for the identification of members of the family Enterobacteriaceae.
Pyrroloquinoline Quinone-Dependent Cytochrome Reduction in Polyvinyl Alcohol-Degrading
Pseudomonas
sp. Strain VM15C
Authors: Shimao Masayuki , Onishi Syuji , Kato Nobuo , Sakazawa Chikahiro
Published: January 2020

A polyvinyl alcohol (PVA) oxidase-deficient mutant of
Pseudomonas
sp. strain VM15C, strain ND1, was shown to possess PVA dehydrogenase, in which pyrroloquinoline quinone (PQQ) functions as a coenzyme. The mutant grew on PVA and required PQQ for utilization of PVA as an essential growth factor. Incubation of the membrane fraction of the mutant with PVA caused cytochrome reduction of the fraction. Furthermore, it was found that in spite of the presence of PVA oxidase, the membrane fraction of strain VM15C grown on glucose without PQQ required PQQ for cytochrome reduction during incubation with PVA. The results provide evidence that PVA dehydrogenase couples with the electron transport chain of PVA-degrading bacteria but that PVA oxidase does not.
Colonization of the porcine gastrointestinal tract by lactobacilli
Authors: Pedersen K , Tannock G W
Published: January 2020

Eight strains of lactobacillus isolated from the porcine gastrointestinal tract were tested for their ability to adhere in vitro to cells collected from stratified squamous epithelium in the digestive tracts of newborn piglets. Piglets were inoculated with individual strains, and their digestive tracts were sampled at intervals to determine the colonizing ability of the lactobacilli. The results of the in vitro test did not predict whether a lactobacillus strain would associate with stratified squamous epithelium in the piglet digestive tract, but epithelial association in vivo appeared to be an important factor in the maintenance of lactobacillus populations in the tract. None of the lactobacillus strains used as inocula was numerically dominant in the tract 7 days after inoculation of the piglets with a single dose of the bacteria.
Possible Involvement of Toluene-2,3-Dioxygenase in Defluorination of 3-Fluoro-Substituted Benzenes by Toluene-Degrading
Pseudomonas
sp. Strain T-12
Authors: Renganathan V.
Published: January 2020

Pseudomonas
sp. strain T-12 cells in which the toluene-degradative pathway enzymes have been induced can transform many 3-fluoro-substituted benzenes to the corresponding 2,3-catechols with simultaneous elimination of the fluorine substituent as inorganic fluoride. Substrates for this transformation included 3-fluorotoluene, 3-fluorotrifluorotoluene, 3-fluorohalobenzenes, 3-fluoroanisole, and 3-fluorobenzonitrile. While 3-fluorotoluene and 3-fluoroanisole produced only defluorinated catechols, other substrates generated catechol products with and without the fluorine substituent. The steric size of the C-1 substituent affected the ratio of defluorinated to fluorinated catechols formed from a substrate. A mechanism for the defluorination reaction involving toluene-2,3-dioxygenase is proposed.
Proportion of beta-D-glucuronidase-negative Escherichia coli in human fecal samples
Authors: Chang G W , Brill J , Lum R
Published: January 2020

Convenient assays and reports that almost all clinical isolates of Escherichia coli produce beta-D-glucuronidase (GUR) have led to great interest in the use of the enzyme for the rapid detection of the bacterium in water, food, and environmental samples. In these materials, E. coli serves as an indicator of possible fecal contamination. Therefore, it was crucial to examine the proportion of GUR-negative E. coli in human fecal samples. The bacterium was isolated from 35 samples, and a mean of 34% and a median of 15% were found to be GUR negative in lauryl sulfate tryptose broth with 4-methylumbelliferyl-beta-D-glucuronide. E. coli from three samples were temperature dependent for GUR production: very weakly positive at 37 degrees C but strongly positive at 44.5 degrees C. These results remind us of differences between fecal and clinical E. coli populations, of diversity in GUR regulation and expression in natural populations of E. coli, and of the need for caution in using GUR for the detection of fecal E. coli.
Occurrence of two different forms of protocatechuate 3,4-dioxygenase in a Moraxella sp
Authors: Sterjiades R , Pelmont J
Published: January 2020

Two alternative forms of protocatechuate 3,4-dioxygenase (PCase) have been purified from Moraxella sp. strain GU2, a bacterium that is able to grow on guaiacol or various other phenolic compounds as the sole source of carbon and energy. One of these forms (PCase-P) was induced by protocatechuate and had an apparent molecular weight of 220,000. The second form (PCase-G) was induced by guaiacol or other phenolic compounds, such as 2-ethoxyphenol or 4-hydroxybenzoate. It appeared to be smaller (Mr 158,000), and its turnover number was about double that of the former enzyme. Both dioxygenases had similar properties and were built from the association of equal amounts of nonidentical subunits, alpha and beta, which were estimated to have molecular weights of 29,500 and 25,500, respectively. The (alpha beta)3 and (alpha beta)4 structures were suggested for PCases G and P, respectively. On the basis of two-dimensional gel electrophoresis, the alpha and beta polypeptides of PCase-G differed from those of PCase-P. Amino acid analysis supported this conclusion. Both PCases, however, had several other properties in common. It is proposed that both isoenzymes were generated from different sets of alpha and beta subunits, and the significance of these data is discussed.
Estimation of nitrogenase activity in the presence of ethylene biosynthesis by use of deuterated acetylene as a substrate
Authors: Lin-Vien D , Fateley W G , Davis L C
Published: January 2020

Nitrogenase reduces deuterated acetylene primarily to cis dideuterated ethylene. This can be distinguished from undeuterated ethylene by the use of Fourier transform infrared spectroscopy. Characteristic bands in the region from 800 to 3,500 cm-1 can be used to identify and quantitate levels of these products. This technique is applicable to field studies of nitrogen fixation where ethylene biosynthesis by plants or bacteria is occurring. We have verified the reaction stoichiometry by using Klebsiella pneumoniae and Bradyrhizobium japonicum in soybeans. The most useful bands for quantitation of substrate purity and product distribution are as follows: acetylene-d0, 3,374 cm-1; acetylene-d1, 2,584 cm-1; acetylene-d2, 2,439 cm-1; cis-ethylene-d2, 843 cm-1; trans-ethylene-d2, 988 cm-1; ethylene-d1, 943 cm-1; ethylene-d0, 949 cm-1. (The various deuterated ethylenes and acetylenes are designated by a lowercase d and subscript to indicate the number, but not the position, of deuterium atoms in the molecule.) Mass spectrometry coupled to a gas chromatograph system has been used to assist in quantitation of the substrate and product distributions. Significant amounts of trans-ethylene-d2 were produced by both wild-type and nifV mutant K. pneumoniae. Less of this product was observed with the soybean system.
Inactivation of aflatoxin B1 by using the synergistic effect of hydrogen peroxide and gamma radiation
Authors: Patel U D , Govindarajan P , Dave P J
Published: January 2020

Inactivation of aflatoxin B1 was studied by using gamma radiation and hydrogen peroxide. A 100-krad dose of gamma radiation was sufficient to inactivate 50 micrograms of aflatoxin B1 in the presence of 5% hydrogen peroxide, and 400 krad was required for total degradation of 100 micrograms of aflatoxin in the same system. Degradation of aflatoxin B1 was confirmed by high-pressure liquid chromatographic and thin-layer chromatographic analysis. Ames microsomal mutagenicity test showed loss of aflatoxin activity. This method of detoxification also reduces the toxin levels effectively in artificially contaminated groundnuts.
Coupling of Solar Energy to Hydrogen Peroxide Production in the Cyanobacterium
Anacystis nidulans
Authors: Roncel Mercedes , Navarro José A. , De la Rosa Miguel A.
Published: January 2020

Hydrogen peroxide production by blue-green algae (cyanobacteria) under photoautotrophic conditions is of great interest as a model system for the bioconversion of solar energy. Our experimental system was based on the photosynthetic reduction of molecular oxygen with electrons from water by
Anacystis nidulans
1402-1 as the biophotocatalyst and methyl viologen as a redox intermediate. It has been demonstrated that the metabolic conditions of the algae in their different growth stages strongly influence the capacity for hydrogen peroxide photoproduction, and so the initial formation rate and net peroxide yield became maximum in the mid-log phase of growth. The overall process can be optimized in the presence of certain metabolic inhibitors such as iodoacetamide and
p
-hydroxymercuribenzoate, as well as by permeabilization of the cellular membrane after drastic temperature changes and by immobilization of the cells in inert supports such as agar and alginate.
In situ survival of Vibrio cholerae and Escherichia coli in a tropical rain forest watershed
Authors: Pérez-Rosas N , Hazen T C
Published: January 2020

For 12 months, Vibrio cholerae and fecal coliform densities were monitored along with nine other water quality parameters at 12 sites in a rain forest watershed in Puerto Rico. Densities of V. cholerae and fecal coliforms were not significantly correlated, even though the highest densities of both bacteria were found at a sewage outfall. High densities of V. cholerae were also found at pristine sites at the highest point in the watershed. The density of Escherichia coli and V. cholerae in membrane diffusion chambers did not change significantly during the course of two such studies. Physiological activity, as measured by electron transport system activity and relative nucleic acid composition, indicated that both E. coli and V. cholerae remained active. This study suggests that V. cholerae is indigenous to tropical fresh waters and that assays other than those that detect fecal coliforms or E. coli must be used for assessing public health risk in tropical waters.
Threshold Acetate Concentrations for Acetate Catabolism by Aceticlastic Methanogenic Bacteria
Authors: Westermann Peter , Ahring Birgitte K. , Mah Robert A.
Published: January 2020

Marked differences were found for minimum threshold concentrations of acetate catabolism by
Methanosarcina barkeri
227 (1.180 mM),
Methanosarcina mazei
S-6 (0.396 mM), and a
Methanothrix
sp. (0.069 mM). This indicates that the aceticlastic methanogens responsible for the conversion of acetate to methane in various ecosystems might be different, depending on the prevailing in situ acetate concentrations.
Comparison of a new inorganic membrane filter (Anopore) with a track-etched polycarbonate membrane filter (Nuclepore) for direct counting of bacteria
Authors: Jones S E , Ditner S A , Freeman C , Whitaker C J , Lock M A
Published: January 2020

Bacterial counts obtained by using a new Anopore inorganic membrane filter were 21 to 33% higher than those obtained by using a Nuclepore polycarbonate membrane filter. In addition, the inorganic filter had higher flow rates, permitting lower vacuum pressures to be used, while the intrinsically flat, rigid surface resulted in easier focusing and sharp definition of bacteria across the whole field of view.
Enhanced Conversion of Lactose to Glycerol by
Kluyveromyces fragilis
Utilizing Whey Permeate as a Substrate
Authors: Jenq Wheamei , Speckman Ray A. , Crang Richard E. , Steinberg Marvin P.
Published: January 2020

Kluyveromyces fragilis
(CBS 397) is a nonhalophilic yeast which is capable of lactose utilization from whey permeate and high glycerol production under anaerobic growth conditions. However, the optimum yields of glycerol (11.6 mg/ml of whey permeate medium) obtained in this study occurred only in the presence of 1% Na
2
SO
3
as a steering agent. The use of other concentrations of Na
2
SO
3
, as well as 5% NaCl and 1% ascorbic acid, had no or detrimental effects on cell growth, lactose utilization, and glycerol production. Glycerol yields were greater in cultures grown from a light inoculum of
K. fragilis
than in cultures in which a resuspended mass of cells was introduced into the medium. The results of this study suggest that this strain of
K. fragilis
may be useful commercially in the utilization of cheese whey lactose and the concomitant production of glycerol.
Comparison of lithium chloride-phenylethanol-moxalactam and modified Vogel Johnson agars for detection of Listeria spp. in retail-level meats, poultry, and seafood
Authors: Buchanan R L , Stahl H G , Bencivengo M M , Del Corral F
Published: January 2020

The effectiveness of Modified Vogel Johnson agar and lithium chloride-phenylethanol-moxalactam agar for detection of Listeria spp. in foods was compared by using the media to analyze retail-level meat, poultry, and seafood both by direct plating and in conjunction with a three-tube most-probable-number enrichment. The most-probable-number protocol detected Listeria species, including Listeria monocytogenes, in a substantial portion of the fresh meat and seafood samples. In most instances the Listeria levels were less than 2 CFU/g, which precluded detection by direct plating. Modified Vogel Johnson agar performed as well as did lithium chloride-phenylethanol-moxalactam agar and was considerably easier to use because of its ability to differentiate Listeria spp. from other microorganisms.
Bradyrhizobium japonicum
Survival in and Soybean Inoculation with Fluid Gels
Authors: Jawson Michael D. , Franzluebbers Alan J. , Berg Robert K.
Published: January 2020

The utilization of gels, which are used for fluid drilling of seeds, as carriers of
Bradyrhizobium japonicum
for soybean (
Glycine max
(L.) Merr.) inoculation was studied. Gels of various chemical composition (magnesium silicate, potassium acrylate-acrylamide, grafted starch, and hydroxyethyl cellulose) were used, although the hydroxyethyl cellulose gels were more extensively investigated. Gel inocula were prepared by mixing gel powder with liquid cultures of
B. japonicum
(2% [wt/vol]). The population of
B. japonicum
USDA 110 did not change in each gel type during 8 days of incubation at 28°C. These fluid gels were prepared with late-exponential-growth-phase cells that were washed and suspended in physiological saline. Mid-exponential-growth-phase
B. japonicum
USDA 110, 123, and 138 grew in cellulose gels prepared with yeast extract-mannitol broth as well as or better than in yeast extract-mannitol broth alone for the first 10 days at 28°C. Populations in these cellulose gels after 35 days were as large as when the gels had originally been prepared, and survival occurred for at least 70 days. Soybeans grown in sand in the greenhouse had greater nodule numbers, nodule weights, and top weights with gel inoculants compared with a peat inoculant. In soil containing 10
3
indigenous
B. japonicum
per g of soil, inoculation resulted in increased soybean nodule numbers, nodule weights, and top weights, but only nodule numbers were greater with gel than with peat inoculation. The gel-treated seeds carried 10
2
to 10
3
more bacteria per seed (10
7
to 10
8
) than did the peat-treated seeds.
Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations
Authors: Madigan M T , Takigiku R , Lee R G , Gest H , Hayes J M
Published: January 2020

Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.
Sorption and Metabolism of Metolachlor by a Bacterial Community
Authors: Liu S.-Y. , Zheng Z. , Zhang R. , Bollag J.-M.
Published: January 2020

A stable bacterial community absorbed and transformed the herbicide metolachlor [2-chloro-
N
-(2-ethyl- 6-methylphenyl)-
N
-(2-methoxy-1-methylethyl)-acetamide] from a liquid medium. About 80% of the added ring-[U-
14
C]metolachlor (50 μg/ml) disappeared from the medium and accumulated inside the cells. The ratio of cellular
14
C to
14
C in 1 mg of supernatant reached a value of 1.1 × 10
4
in a 10-day-old culture.
14
C remaining in the medium consisted primarily of two dechlorinated products of metolachlor with
m/z
233 and 263 as determined by mass spectrometry. The
14
C-labeled material absorbed by the cells was strongly bound; only 2% of the
14
C was released into deionized water after shaking for 3 h. Approximately 96% of the
14
C associated with the biomass was extracted with acetone, and high-performance liquid chromatographic analysis of this fraction showed six peaks containing radioactivity. Since no metolachlor was detected by chromatographic analysis, it was concluded that the radioactivity recovered from the cells represented transformed products of metolachlor. Pure cultures isolated from the bacterial mixed culture were less effective in transforming and accumulating metolachlor. These results suggest that it may be advantageous to seed an aquatic environment with a mixture of microorganisms, rather than individual microbial species, as a method for removal or detoxification of metolachlor.
Detection of Vesicular-Arbuscular Mycorrhizal Fungus Colonization of Roots by Using a Dot-Immunoblot Assay
Authors: Wright Sara F. , Morton Joseph B.
Published: January 2020

An immunoblotting procedure was developed to overcome the difficulty in identifying root colonization by a vesicular-arbuscular mycorrhizal fungus. The procedure utilized a murine monoclonal antibody that reacts with a protein in spores and hyphae of
Glomus occultum
, a fungus characterized by abundant production of hyaline spores and nonstaining intraradical infection. Minimally disturbed whole roots were squashed on nitrocellulose membranes. After inactivation of endogenous peroxidase, an indirect enzyme-linked immunosorbent assay was performed on the nitrocellulose with peroxidase-conjugated anti-mouse antibody as the second antibody. Antigen from
G. occultum
, revealed by a precipitating stain, was seen as purple dots on the nitrocellulose, which also retained the impression of the root.
Effect of polyethylene glycol-electrolyte lavage solution on intestinal microflora
Authors: Morotomi M , Guillem J G , Pocsidio J , LoGerfo P , Treat M , Forde K A , Weinstein I B , Watanabe I , Mutai M
Published: January 2020

The bacterial flora of colonic aspirates taken after oral administration of a polyethylene glycol-electrolyte lavage solution to patients undergoing colonoscopy was analyzed by standard bacteriological methods and DNA hybridization techniques. The data were compared with those for normal feces collected from the same patients the day before treatment. The results indicate that the bacterial composition of feces differs from individual to individual but is not altered by the oral intake of a polyethylene glycol-electrolyte lavage solution. This pilot study demonstrates that routine colonoscopy aspirates taken after standard colonoscopy preparation accurately reflect the microflora of feces and therefore may be used in large-scale epidemiological studies.
Identification of Pseudomonas alcaligenes chromosomal DNA in the plasmid DNA of the chlorobenzene-degrading recombinant Pseudomonas putida strain CB1-9
Authors: Carney B F , Kröckel L , Leary J V , Focht D D
Published: January 2020

The recombinant Pseudomonas putida strain CB1-9, which acquired the ability to grow on chlorobenzenes, contains a 33-kilobase (kb) plasmid (pKFL3) which lacked homology to an indigenous 15-kb plasmid (pKFL1) in Pseudomonas alcaligenes C-0 parent but was homologous to a 55-kb plasmid (pKFL2) from the P. putida R5-3 parent. Chromosomal DNA of P. alcaligenes C-0 hybridized to probes prepared from pKFL3 but not to probes prepared from pKFL2. A single clone from a genomic library of P. alcaligenes C-0 hybridized to EcoRI-digested pKFL3. Southern blot hybridization with the insert DNA from that clone identified homology with specific restriction enzyme fragments in pKFL3. The ability of the recombinant to utilize 3-chlorobenzoate, chlorobenzene, and 1,4-dichlorobenzene as well as its loss of utilization of xylenes and methylbenzoates appears to be associated with the transfer and integration of chromosomal DNA from P. alcaligenes into a Tol-like plasmid of P. putida R5-3.
Cell surface charge characteristics and their relationship to bacterial attachment to meat surfaces
Authors: Dickson J S , Koohmaraie M
Published: January 2020

Cell surface charge and hydrophobicity of Bacillus subtilis, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis were determined by hydrocarbon adherence, hydrophobic interaction, and electrostatic interaction chromatography. Surface charge and hydrophobicity were compared with the initial attachment values and rates of attachment of the bacteria to meat surfaces. There was a linear correlation between the relative negative charge on the bacterial cell surface and initial attachment to lean beef muscle (r2 = 0.885) and fat tissue (r2 = 0.777). Hydrophobicity correlated well with attachment to fat tissue only. The relative hydrophobicity of each bacterium was dependent on the specific method of determination, with wide variations noted between methods.
Biotransformation of 1,1,1-trichloroethane, trichloromethane, and tetrachloromethane by a Clostridium sp
Authors: Gälli R , McCarty P L
Published: January 2020

A gram-positive, strictly anaerobic, motile, endospore-forming rod, tentatively identified as a proteolytic Clostridium sp., was isolated from the effluent of an anaerobic suspended-growth bioreactor. The organism was able to biotransform 1,1,1-trichloroethane, trichloromethane, and tetrachloromethane. 1,1,1-Trichloroethane was completely transformed (greater than or equal to 99.5%) by reductive dehalogenation to 1,1-dichloroethane (30 to 40%) and, presumably by other mechanisms, to acetic acid (7%) and unidentified products. The reductive dehalogenation of tetrachloromethane led to the intermediate trichloromethane, which was further transformed to dichloromethane (8%) and unidentified products. The biotransformation occurred during the exponential growth phase, as well as during the stationary phase. Tetrachlorethene, trichloroethene, 1,1-dichloroethene, chloroethane, 1,1-dichloroethane, and dichloromethane were not biotransformed significantly by the organism.
Intra- and Extracellular Localization of Lignin Peroxidase during the Degradation of Solid Wood and Wood Fragments by
Phanerochaete chrysosporium
by Using Transmission Electron Microscopy and Immuno-Gold Labeling
Authors: Daniel Geoffrey , Nilsson Thomas , Pettersson Bert
Published: January 2020

The distribution of lignin peroxidase during degradation of both wood and woody fragments by the white rot fungus
Phanerochaete chrysosporium
was investigated by using anti-lignin peroxidase in conjunction with postembedding transmission electron microscopy and immuno-gold labeling techniques. The enzyme was localized in the peripheral regions of the fungal cell cytoplasm in association with the cell membrane, fungal cell wall, and extracellular slime materials. In solid wood, lignin peroxidase was detected in low concentrations associated with both superficial and degradation zones within secondary cell walls undergoing fungal attack. A similar but much greater level of extracellular peroxidase activity was associated with wood fragments degraded by the fungus grown under liquid culture conditions optimal for production of the enzyme. Efforts to infiltrate degraded wood pieces with high levels of lignin peroxidase showed the enzyme to be restricted to superficial regions of wood decay and to penetrate wood cell walls only where the wall structure had been modified. In this respect the enzyme was able to penetrate characteristic zones of degradation within the secondary walls of fibers to sites of lignin attack. This suggests a possibility for a close substrate-enzyme association during wood cell wall degradation.
Microscale Vertical Profiles of N
2
Fixation, Photosynthesis, O
2
, Chlorophyll
a
, and Light in a Cyanobacterial Assemblage
Authors: Dodds Walter K.
Published: January 2020

Profiles of
15
N
2
fixation, O
2
production (gross photosynthesis), O
2
concentration, chlorophyll
a
concentration, and photon fluence rates were measured with 50-μm resolution in colonies of the heterocyst-forming cyanobacterium
Nostoc parmelioides
. Microelectrode measurements were made after 20 h of incubation under
15
N
2
gas. Colonies were frozen, and 50-μm sections were prepared by using a freezing microtome and analyzed for
15
N enrichment and chlorophyll
a
concentration. Colonies exhibited steep spatial gradients in rates of gross photosynthesis, O
2
concentration, and irradiance, with the highest values generally occurring at the surface. O
2
concentration, photosynthesis, and irradiance all showed positive correlations, but chlorophyll
a
concentrations varied independently of photosynthesis and irradiance. Forty-four percent of the variation in
15
N incorporation was explained by gross photosynthesis (a positive correlation) when incorporation of
15
N was expressed per unit of biomass (chlorophyll
a
).
Lipid growth requirement and influence of lipid supplement on fatty acid and aldehyde composition of Syntrophococcus sucromutans
Authors: Doré J , Bryant M P
Published: January 2020

Results concerning the ruminal fluid growth requirement of the ruminal acetogen, Syntrophococcus sucromutans, indicate that octadecenoic acid isomers satisfy this essential requirement. Complex lipids, such as triglycerides and phospholipids, can also support growth. The cellular fatty acid and aldehyde composition closely reflects that of the lipid supplement provided to the cells. Up to 98% of the fatty acids and 80% of the fatty aldehydes are identical in chain length and degree of unsaturation to the octadecenoic acid supplement provided in the medium. S. sucromutans shows a tendency to have a greater proportion of the aldehyde form among its 18 carbon chains than it does with the shorter-chain simple lipids, which may be interpreted as a strategy to maintain membrane fluidity. 14C labeling showed that most of the oleic acid taken up from the medium was incorporated into the membrane fraction of the cells.
Effect of Sugar Transport Inactivation in
Saccharomyces cerevisiae
on Sluggish and Stuck Enological Fermentations
Authors: Salmon J. M.
Published: January 2020

Sluggish and stuck (i.e., very delayed or incomplete) fermentations have been often observed in wine making. Some of them appeared to be associated with insufficient levels of yeast nutrients such as assimilable nitrogen. In these conditions, sugar transport catabolite inactivation, which is triggered by the protein synthesis arrest, may account in part for the inhibition of fermentation. Moreover, this mechanism of inhibition may explain the failure of added ammoniacal nitrogen to nitrogen-limited musts to restore or elevate rate of fermentation after the early yeast growth phase.