bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of
Thermus ruber
Strains Isolated from Icelandic Hot Springs and DNA:DNA Homology of
Thermus ruber
and
Thermus aquaticus
Authors: Sharp Richard J. , Williams Ralph A. D.
Published: January 2020

Seventeen pink-pigmented strains of the genus
Thermus
were isolated from samples collected from thermal areas of Iceland. The strains were examined by using phenotypic characterization and DNA:DNA homology and were compared with recognized strains. Visually, the strains could be divided into three groups based on their pigmentation; however, spectroscopic studies of the pigments indicated little difference among them. Most strains required a vitamin supplement for growth and used fructose, maltose, mannose, or sucrose as the sole carbon source. In the presence of nitrate, two strains were able to grow under anaerobic conditions. The optimum growth temperature was 60°C; growth did not occur at 30 or 70°C.
Kinetics of Mixed Microbial Assemblages Enhance Removal of Highly Dilute Organic Substrates
Authors: Lewis David L. , Hodson Robert E. , Hwang Huey-Min
Published: January 2020

Our experiments with selected organic substrates reveal that the rate-limiting process governing microbial degradation rates changes with substrate concentration,
S
, in such a manner that substrate removal is enhanced at lower values of
S
. This enhancement is the result of the dominance of very efficient systems for substrate removal at low substrate concentrations. The variability of dominant kinetic parameters over a range of
S
causes the kinetics of complex assemblages to be profoundly dissimilar to those of systems possessing a single set of kinetic parameters; these findings necessitate taking a new approach to predicting substrate removal rates over wide ranges of
S
.
Identification and Characteristics of Actinomycetes Useful for Semicontinuous Treatment of Domestic Animal Feces
Authors: Hayashida Shinsaku , Nanri Nobuya , Teramoto Yuji , Nishimoto Toshiaki , Ohta Kazuyoshi , Miyaguchi Masao
Published: January 2020

Selected strains of actinomycetes useful for practicing semicontinuous treatment of swine and poultry feces were identified as
Streptomyces antibioticus
S-4,
S. puniceus
N-50-2,
S. nigrifaciens
N-9-3,
Thermoactinomyces vulgaris
HIR-60, and
Thermomonospora viridis
HIR-50. These five obligately aerobic strains grew preferably on nonsterilized fresh swine feces in 24 h without any additives. They assimilated offensive volatile fatty acids in the swine and poultry feces. Cultures of these five strains were mixed and used as seed for the practical treatments of 1 ton of swine feces over the wide temperature range of 15 to 60°C. Strain HIR-50 grew most predominantly on both fresh swine and poultry feces at 50 to 55°C and decomposed uric acid. For the efficient penetration of mycelia into the feces, manures were mixed once a day so as not to break the solid mass, and the dehydration rate of feces had to be controlled in proportion to the mycelial growth rate. The actinomycete biofertilizer thus manufactured in 10 days was odorless and promotive of plant growth.
Isolation and characterization of Aspergillus parasiticus mutants with impaired aflatoxin production by a novel tip culture method
Authors: Yabe K , Nakamura H , Ando Y , Terakado N , Nakajima H , Hamasaki T
Published: January 2020

A convenient procedure consisting of UV photography (K. Yabe, Y. Ando, M. Ito, and N. Terakado, Appl. Environ. Microbiol. 53:230-234, 1987) and a tip culture method has been devised for the isolation and characterization of Aspergillus parasiticus mutants relating to aflatoxin production. With the latter procedure, the production of aflatoxins excreted into the culture medium and precursors in the mycelium were easily measured quantitatively or semiquantitatively. A total of 38 mutants in which the aflatoxigenicity was decreased or lost were obtained by UV radiation; 3 were found to be blocked mutants, which accumulated the aflatoxin precursors versicolorin A or averantin.
Isolation and identification of intestinal steroid-desulfating bacteria from rats and humans
Authors: Van Eldere J , Robben J , De Pauw G , Merckx R , Eyssen H
Published: January 2020

We isolated 12 strictly anaerobic steroid-3-sulfate-desulfating strains from the intestinal floras of rats and humans. Two strains (S1 and S2) of the same atypical Clostridium species and an atypical Lactobacillus strain (termed R9) were obtained from rats. The human isolates were identified as Eubacterium cylindroides (two strains, H1 and H2), Peptococcus niger (two strains, H4 and H89), and Clostridium clostridiiforme. We also isolated, from different human fecal samples, four strains of phenotypically similar asaccharolytic Bacteroides strains, H6.2a, H6.2b, H65, and H175. Aryl steroid sulfatase activity for estrogen sulfates was present in all isolates. Alkyl steroid sulfatase activity for both 3 alpha- and 3 beta-sulfates was found only in P. niger H4. The same P. niger strain and Clostridium strains S1 and S2 also possessed bile acid sulfatase activity.
Rapid detection of total and fecal coliforms in water by enzymatic hydrolysis of 4-methylumbelliferone-beta-D-galactoside
Authors: Berg J D , Fiksdal L
Published: January 2020

Three fluorogenic methylumbelliferone (MU) substrates were evaluated for rapid detection of total and fecal coliform bacteria (TC and FC) in drinking water. 4-MU-beta-D-galactoside, MU-heptanoate, and MU-glucuronide were used to determine enzyme activity as a surrogate measure of coliform concentration. Coliforms occurring in river water and in potable water artificially contaminated with raw sewage were tested. The initial rate of hydrolysis (delta F) of MU-beta-D-galactoside showed promise as an indicator of TC and FC within 15 min. delta F of MU-glucuronide was insufficient in the 15-min assay, and combinations of the MU substrates did not enhance delta F. A direct membrane filter method incorporating MU-beta-D-galactoside into an agar medium allowed the detection of as few as 1 FC per 100 ml within 6 h.
DNA amplification to enhance detection of genetically engineered bacteria in environmental samples
Authors: Steffan R J , Atlas R M
Published: January 2020

The polymerase chain reaction (PCR) was performed to amplify a 1.0-kilobase (kb) probe-specific region of DNA from the herbicide-degrading bacterium Pseudomonas cepacia AC1100 in order to increase the sensitivity of detecting the organism by dot-blot analysis. The 1.0-kb region was an integral portion of a larger 1.3-kb repeat sequence which is present as 15 to 20 copies on the P. cepacia AC1100 genome. PCR was performed by melting the target DNA, annealing 24-base oligonucleotide primers to unique sequences flanking the 1.0-kb region, and performing extension reactions with DNA polymerase. After extension, the DNA was again melted, and the procedure was repeated for a total of 25 to 30 cycles. After amplification the reaction mixture was transferred to nylon filters and hybridized against radiolabeled 1.0-kb fragment probe DNA. Amplified target DNA was detectable in samples initially containing as little as 0.3 pg of target. The addition of 20 micrograms of nonspecific DNA isolated from sediment samples did not hinder amplification or detection of the target DNA. The detection of 0.3 pg of target DNA was at least a 10(3)-fold increase in the sensitivity of detecting gene sequences compared with dot-blot analysis of nonamplified samples. PCR performed after bacterial DNA was isolated from sediment samples permitted the detection of as few as 100 cells of P. cepacia AC1100 per 100 g of sediment sample against a background of 10(11) diverse nontarget organisms; that is, P. cepacia AC1100 was positively detected at a concentration of 1 cell per g of sediment. This represented a 10(3)-fold increase in sensitivity compared with nonamplified samples.
Biodegradation of Nitriles in Shale Oil
Authors: Aislabie Jackie , Atlas Ronald M.
Published: January 2020

Enrichment cultures were obtained, after prolonged incubation on a shale oil as the sole source of nitrogen, that selectively degraded nitriles. Capillary gas chromatographic analyses showed that the mixed microbial populations in the enrichments degraded the homologous series of aliphatic nitriles but not the aliphatic hydrocarbons, aromatic hydrocarbons, or heterocyclic-nitrogen compounds found in this oil. Time course studies showed that lighter nitriles were removed more rapidly than higher-molecular-weight nitriles. A
Pseudomonas fluorescens
strain isolated from an enrichment, which was able to completely utilize the individual nitriles undecyl cyanide and undecanenitrile as sole sources of carbon and nitrogen, was unable to attack stearonitrile when provided alone as the growth substrate. A
P. aeruginosa
strain, also isolated from one of the enrichments, used nitriles but not aliphatic or aromatic hydrocarbons when the oil was used as a sole nitrogen source. However, when the shale oil was used as the sole source of carbon, aliphatic hydrocarbons in addition to nitriles were degraded but aromatic hydrocarbons were still not attacked by this
P. aeruginosa
strain.
Degradation of bromacil by a Pseudomonas sp
Authors: Chaudhry G R , Cortez L
Published: January 2020

A gram-negative rod, identified as a Pseudomonas sp., was isolated from soil by using bromacil as the sole source of carbon and energy. During growth on bromacil or 5-bromouracil, almost stoichiometric amounts of bromide were released. The bacterium was shown to harbor two plasmids approximately 60 and 100 kilobases in size. They appeared to be associated with the ability to utilize bromacil as a sole source of carbon and also with resistance to ampicillin. This microorganism also showed the potential to decontaminate soil samples fortified with bromacil under laboratory conditions.
Heat Production by the Denitrifying Bacterium
Pseudomonas fluorescens
and the Dissimilatory Ammonium-Producing Bacterium
Pseudomonas putrefaciens
during Anaerobic Growth with Nitrate as the Electron Acceptor
Authors: Samuelsson M.-O. , Cadez P. , Gustafsson L.
Published: January 2020

The heat production rate and the simultaneous nitrate consumption and production and consumption of nitrite and nitrous oxide were monitored during the anaerobic growth of two types of dissimilatory nitrate reducers.
Pseudomonas fluorescens
, a denitrifier, consumed nitrate and accumulated small amounts of nitrite or nitrous oxide. The heat production rate increased steadily during the course of nitrate consumption and decreased rapidly concomitant with the depletion of the electron acceptors. A mean experimental enthalpy change value of −800 kJ/mol of nitrate and a mean growth yield value of 33 g (dry weight)/mol of nitrate consumed were obtained for different concentrations of nitrate. For
Pseudomonas putrefaciens
, a dissimilatory ammonium producer, the nitrate consumption resulted in an accumulation of nitrite and nitrous oxide. Nitrite consumption commenced after depletion of the nitrate; consequently, two phases were noted in the heat production rate curve during growth. A mean experimental enthalpy change value of −810 kJ/mol of nitrate was obtained for different concentrations of nitrate.
T-2 toxin and diacetoxyscirpenol metabolism by Baccharis spp
Authors: Mirocha C J , Abbas H K , Treeful L , Bean G
Published: January 2020

Hybrids resulting from crosses between Baccharis sarothroides and B. pilularis (FS1), B. sarothroides (FS2) and B. megapotamica (FS3) were tested for their tolerance to trichothecenes as well as their ability to metabolize the toxins. B. sarothroides (desert broom) was placed in an aqueous solution containing 500 ppm of T-2 toxin and showed visible signs of toxicity on the twigs at 21 h after exposure but not at 6 h, indicating some resistance. Samples of the twigs harvested 6 and 21 h after treatment contained, respectively, T-2 (0.03 and 2.2 micrograms/g), HT-2 (0.09 and 7.6 micrograms/g), and T-2-tetraol (2.1 and 2.6 micrograms/g). The hybrid FS1 showed no signs of toxicity 6 h after treatment, and its twigs contained T-2 (0.8 micrograms/g), HT-2 (10.2 micrograms/g), and T-2-tetraol (10.8 micrograms/g). The leaves at 6 h contained 0.5 micrograms of T-2, 1.7 micrograms of HT-2, 0.01 microgram of 3'-hydroxy-HT-2, and 41 micrograms of T-2-tetraol per g. At 21 h, toxic signs were apparent and the twigs contained T-2 (39 micrograms/g), HT-2 (62 micrograms/g), 3'-hydroxy-HT-2 (0.8 microgram/g), and T-2-tetraol (22 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)
Electroporation-induced transformation of intact cells of Clostridium perfringens
Authors: Allen S P , Blaschek H P
Published: January 2020

Electroporation-induced transformation of intact cells of Clostridium perfringens 3624A with plasmids pAMB1 and pHR106 resulted in 3.8 X 10(-5) and 4.2 X 10(-4) transformants per viable cell, respectively. With respect to shuttle plasmid pHR106, these values represent a greater than 100-fold increase in transformation frequency when compared with the values reported with polyethylene glycol-induced L-phase variants.
Microbial colonization of injured cactus tissue (Stenocereus gummosus) and its relationship to the ecology of cactophilic Drosophila mojavensis
Authors: Fogleman J C , Foster J L
Published: January 2020

Necrotic tissue of agria cactus (Stenocereus gummosus) serves as a feeding and breeding substrate for Drosophila mojavensis. This fly species is one of the four endemic Drosophila species in the Sonoran Desert. Freeze injuries were created in arms of agria cactus in Mexico to study the events of microbial colonization. Facultative anaerobic bacteria were the first microbes to be detected, and the exclusion of large arthropods by covering the injuries with netting did not affect bacterial colonization. Yeast growth lagged behind bacterial growth by 2 days, and excluding arthropods delayed the detection of yeasts by an additional 2 days. Thus, insects (such as Drosophila species) and other arthropods do play a role in the colonization of agria rots by yeasts. All injuries were attractive to D. mojavensis within 5 days, and these flies were shown to be carrying significant densities of both bacteria and yeasts. Analysis of the volatile compounds present in the developing rots over time indicated that the volatile pattern is dynamic. Ethanol and acetic acid were the two volatile substances most likely responsible for the initial attraction of the injuries for Drosophila species.
Development of a differential medium for bile salt hydrolase-active Lactobacillus spp
Authors: Dashkevicz M P , Feighner S D
Published: January 2020

An agar plate assay was developed to detect bile salt hydrolase activity in lactobacilli. On Lactobacillus-selective MRS or Rogosa SL medium supplemented with taurodeoxycholic, taurocholic, or taurochenodeoxycholic acids, bile salt hydrolysis was manifested at two intensities: (i) the formation of precipitate halos around colonies or (ii) the formation of opaque granular white colonies. Sixty-six lactobacilli were tested for bile salt hydrolase activity by both the plate assay and a sensitive radiochemical assay. No false-positive or false-negative results were detected by the plate assay. Based on results of experiments with Eubacterium lentum and Bacteroides species, the plate assay was dependent on two factors: (i) the presence of bile salt hydrolytic activity and (ii) the ability of the organism to sufficiently acidify the medium to protonate free bile acids. The availability of a differential medium for determination of bile salt hydrolase activity will provide a rapid method for determining shifts in a specific functional activity of intestinal Lactobacillus species and provide a rapid screening capability for identifying bile salt hydrolase-deficient mutants. The latter application should allow bile salt hydrolase activity to be used as a marker enzyme in genetic experiments.
Characteristics of Hormogonia Formation by Symbiotic
Nostoc
spp. in Response to the Presence of
Anthoceros punctatus
or Its Extracellular Products
Authors: Campbell Elsie Lin , Meeks John C.
Published: January 2020

Nostocacean cyanobacteria typically produce gliding filaments termed hormogonia at a low frequency as part of their life cycle. We report here that all
Nostoc
spp. competent in establishing a symbiotic association with the hornwort
Anthoceros punctatus
formed hormogonial filaments at a high frequency in the presence of
A. punctatus
. The hormogonia-inducing activity was produced by
A. punctatus
under nitrogen-limited culture conditions. The hormogonia of the symbiotically competent
Nostoc
spp. were characterized as motile (gliding) filaments lacking heterocysts and with distinctly smaller cells than those of vegetative filaments; the small cells resulted from a continuation of cell division uncoupled from biomass increase. An essentially complete conversion of vegetative filaments to hormogonia occurred within 12 h of exposure of
Nostoc
sp. strain 7801 to
A. punctatus
growth-conditioned medium. Hormogonia formation was accompanied by loss of nitrogen fixation (acetylene reduction) and by decreases in photosynthetic CO
2
fixation and in vivo NH
4
+
assimilation of 30% and approximately 40%, respectively. The rates of acetylene reduction and CO
2
fixation returned to approximately the control rates within 72 to 96 h after hormogonia induction, as the cultures of
Nostoc
sp. strain 7801 differentiated heterocysts and reverted to the vegetative growth state. The relationship between hormogonia formation and symbiotic competence is discussed.
Continuous and Batch Production of Chloroperoxidase by Mycelial Pellets of
Caldariomyces fumago
in an Airlift Fermentor
Authors: Carmichael Robert D. , Pickard Michael A.
Published: January 2020

Batch and continuous production of the extracellular heme glycoprotein chloroperoxidase (CPO) was studied with an airlift fermentor. We induced
Caldariomyces fumago
CMI 89362 to form pellets by transferring a small inoculum volume in preculture prior to growth in a 1-liter fermentor. Continuous replacement of the fructose-salts medium (dilution rate, 0.008 h
−1
) supported continuous CPO formation at an average concentration of 128 ± 10 mg of CPO liter
−1
for 8 days. Optimum CPO production rates averaged 1.2 ± 0.1 mg of CPO h
−1
at dilution rates below 0.033 h
−1
. Varying the carbohydrate content of the feed solution or the time of starting the feed did not significantly alter the amount of CPO produced. Batch fermentation in the airlift fermentor resulted in maximum CPO concentrations of 280 ± 80 mg of CPO liter
−1
, although on two separate occasions CPO concentrations reached 400 to 450 mg liter
−1
, which was double the amount obtained by free hyphae in shake flask culture.
Cellulose Fermentation by an Asporogenous Mutant and an Ethanol-Tolerant Mutant of
Clostridium thermocellum
Authors: Tailliez P. , Girard H. , Longin R. , Beguin P. , Millet J.
Published: January 2020

Two mutants of
Clostridium thermocellum
were isolated after UV light mutagenesis. Mutant A1, selected as asporogenous, exhibited a fermentation pattern similar to that of the wild type. However, at pH 6.5, the mutant degraded 12% more cellulose than did the wild type, leading to enhanced ethanol production. Mutant 647, selected as ethanol tolerant, was able to grow in medium containing 4% ethanol. During the early stage of the exponential growth phase, ethanol was produced as the main product, up to a concentration of about 9 g/liter. After 3 days of culture, 48.3 g (89% of the initial amount) of degraded cellulose per liter was fermented into 12.7 g of ethanol per liter.
Inhibition of Yeast Growth by Octanoic and Decanoic Acids Produced during Ethanolic Fermentation
Authors: Viegas Cristina A. , Rosa M. Fernanda , Sá-Correia Isabel , Novais Júlio M.
Published: January 2020

The inhibition of growth by octanoic or decanoic acids, two subproducts of ethanolic fermentation, was evaluated in
Saccharomyces cerevisiae
and
Kluyveromyces marxianus
in association with ethanol, the main product of fermentation. In both strains, octanoic and decanoic acids, at concentrations up to 16 and 8 mg/liter, respectively, decreased the maximum specific growth rate and the biomass yield at 30°C as an exponential function of the fatty acid concentration and increased the duration of growth latency. These toxic effects increased with a decrease in pH in the range of 5.4 to 3.0, indicating that the undissociated form is the toxic molecule. Decanoic acid was more toxic than octanoic acid. The concentrations of octanoic and decanoic acids were determined during the ethanolic fermentation (30°C) of two laboratory media (mineral and complex) by
S. cerevisiae
and of Jerusalem artichoke juice by
K. marxianus
. Based on the concentrations detected (0.7 to 23 mg/liter) and the kinetics of growth inhibition, the presence of octanoic and decanoic acids cannot be ignored in the evaluation of the overall inhibition of ethanolic fermentation.
Enzyme-capture assay for rapid detection of Escherichia coli in oysters
Authors: Holt S M , Hartman P A , Kaspar C W
Published: January 2020

Enzyme-capture assays (ECAs) for Escherichia coli beta-D-glucuronidase (GUD) were performed directly from 24-h gas-positive lauryl tryptose broth (LTB) fermentation tubes that had been inoculated with oyster homogenate seeded with E. coli. The LTB-ECA method yielded results in 1 day that were equivalent to those obtained in 2 days by an LTB and EC-4-methylumbelliferyl-beta-D-glucuronide (EC-MUG) method. Overall, 62 of 64 (97%) positive EC-MUG broths from which E. coli was isolated were correctly identified by ECA. Of 61 LTB tubes identified as GUD negative by ECA, 59 were confirmed to be free of E. coli by using EC-MUG; thus, the false-negative rate was approximately 3%. Polyclonal antibodies prepared against E. coli GUD reacted only with GUDs of E. coli, Escherichia vulneris, and Shigella sonnei. The antibodies did not react with GUDs from Flavobacterium spp., Staphylococcus spp., Yersinia enterocolitica, shellfish, or bovine liver. The GUD ECA test, when used in conjunction with the most-probable-number technique, was a rapid method for E. coli enumeration in oysters.
19F nuclear magnetic resonance analysis of 5-fluorouracil metabolism in wild-type and 5-fluorouracil-resistant Nectria haematococca
Authors: Parisot D , Malet-Martino M C , Crasnier P , Martino R
Published: January 2020

A mutant (furA3) was isolated from the S1 wild-type strain of Nectria haematococca on the basis of its resistance to 5-fluorouracil (5FU). This mutant has greatly reduced activity of uracil phosphoribosyltransferase, a pyrimidine salvage enzyme catalyzing the synthesis of UMP from uracil. The metabolism of 5FU was examined in both strains by using 19F nuclear magnetic resonance spectroscopy. In the S1 strain, 5FU appears to be metabolized by two pathways operating simultaneously: (i) conversion to fluoronucleotides and (ii) degradation into alpha-fluoro-beta-alanine. The furA3 mutant shows metabolic changes consistent with a uracil phosphoribosyltransferase lesion, since it takes up 5FU and forms a small amount of alpha-fluoro-beta-alanine but does not synthesize fluoronucleotides. Since pigment synthesis is strongly enhanced by 5FU in the S1 wild-type strain but not in the furA3 mutant, these results support the hypothesis that 5FU stimulation of secondary metabolism in N. haematococca is not mediated by the drug itself but involves a phosphorylated anabolite.
Direct phenotypic and genotypic detection of a recombinant pseudomonad population released into lake water
Authors: Morgan J A , Winstanley C , Pickup R W , Jones J G , Saunders J R
Published: January 2020

As a system for studying the fate of genetically engineered microorganisms in the environment, we have previously constructed recombinant plasmids encoding a xylE marker gene (C. Winstanley, J. A. W. Morgan, R. W. Pickup, J. G. Jones, and J. R. Saunders, Appl. Environ. Microbiol. 55:771-777, 1989). A series of direct membrane filter methods have been developed which facilitate the detection of bacterial cells harboring the xylE gene, its product, catechol 2,3-dioxygenase, and catechol 2,3-dioxygenase enzyme activity directly from water samples. These methods enable detection of recombinant populations at concentrations as low as 10(3) to 10(4) cells ml of lake water-1. Direct detection facilitates ecological studies of a range of bacterial strains containing the marker system in aquatic environments. The fate of a recombinant pseudomonad population in lake water was assessed by a combination of colony-forming ability, direct counts, and direct detection of the xylE gene and phenotypic expression of its product.
Selection of amidases with novel substrate specificities from penicillin amidase of Escherichia coli
Authors: Forney L J , Wong D C , Ferber D M
Published: January 2020

To obtain amidases with novel substrate specificity, the cloned gene for penicillin amidase of Escherichia coli ATCC 11105 was mutagenized and mutants were selected for the ability to hydrolyze glutaryl-(L)-leucine and provide leucine to Leu- host cells. Cells with the wild-type enzyme did not grow in minimal medium containing glutaryl-(L)-leucine as a sole source of leucine. The growth rates of Leu- cells that expressed these mutant amidases increased as the glutaryl-(L)-leucine concentration increased or as the medium pH decreased. Growth of the mutant strains was restricted by modulation of medium pH and glutaryl-(L)-leucine concentration, and successive generations of mutants that more efficiently hydrolyzed glutaryl-(L)-leucine were isolated. The kinetics of glutaryl-(L)-leucine hydrolysis by purified amidases from two mutants and the respective parental strains were determined. Glutaryl-(L)-leucine hydrolysis by the purified mutant amidases occurred most rapidly between pH 5 and 6, whereas hydrolysis by wild-type penicillin amidase at this pH was negligible. The second-order rate constants for glutaryl-(L)-leucine hydrolysis by two "second-generation" mutant amidases, 48 and 77 M-1 s-1, were higher than the rates of hydrolysis by the respective parental amidases. The increased rates of glutaryl-(L)-leucine hydrolysis resulted from both increases in the molecular rate constants and decreases in apparent Km values. The results show that it is possible to deliberately modify the substrate specificity of penicillin amidase and successively select mutants with amidases that are progressively more efficient at hydrolyzing glutaryl-(L)-leucine.
Competitiveness of different polysaccharide utilization mutants of Bacteroides thetaiotaomicron in the intestinal tracts of germfree mice
Authors: Salyers A A , Pajeau M
Published: January 2020

Bacteroides thetaiotaomicron, an obligate anaerobe found in high numbers in human colons, can utilize a variety of polysaccharides. To determine which type of polysaccharide contributes most to the nutrition of B. thetaiotaomicron in vivo, we isolated and characterized transposon-generated mutants deficient in the ability to use different polysaccharides. Some mutants were deficient in polysaccharide utilization because of the inability to utilize a component monosaccharide. These mutants included a mutant that was unable to utilize L-fucose (a component of goblet cell mucin), a mutant that was unable to utilize D-galactose (a component of raffinose, stachyose, arabinogalactan, and goblet cell mucin), and a mutant that was unable to utilize either glucuronic acid (a component of mucopolysaccharides) or galacturonic acid (a component of polygalacturonic acid or pectin). Other mutants were unable to use the polysaccharide but could use the component sugars. These included four mutants that were unable to utilize starch and one mutant that was unable to utilize polygalacturonic acid. The mutants were tested for the ability to compete with the wild type for colonization of the intestinal tracts of germfree mice. The only mutants against which the wild type competed successfully in the intestinal tracts of germfree mice were a galactose-negative mutant and a uronic acid-negative mutant. These mutations differed from the others tested in that they affected utilization of more than one type of polysaccharide.(ABSTRACT TRUNCATED AT 250 WORDS)
Synergistic Competitive Inhibition of Ferrous Iron Oxidation by
Thiobacillus ferrooxidans
by Increasing Concentrations of Ferric Iron and Cells
Authors: Lizama Hector M. , Suzuki Isamu
Published: January 2020

Oxidation of ferrous iron by
Thiobacillus ferrooxidans
SM-4 was inhibited competitively by increasing concentrations of ferric iron or cells. A kinetic analysis showed that binding of one inhibitor did not exclude binding of the other and led to synergistic inhibition by the two inhibitors. Binding of one inhibitor, however, was affected by the other inhibitor, and the apparent inhibition constant increased with increasing concentrations of the other inhibitor.
Corky Root of Lettuce Caused by Strains of a Gram-Negative Bacterium from Muck Soils of Florida, New York, and Wisconsin
Authors: van Bruggen Ariena H. C. , Brown Philip R. , Jochimsen Kenneth N.
Published: January 2020

Slow-growing bacteria similar to the bacterium causing lettuce corky root (CR) in California (strain CA1) were isolated from muck soils of Florida, New York, and Wisconsin, using lettuce seedlings as bait. All strains were tested for reaction with polyclonal antibodies produced against strain CA1 and for pathogenicity on CR-susceptible (Salinas) and CR-resistant (Green Lake) lettuce cultivars in a greenhouse. Five strains from Florida, three from New York, and three from Wisconsin induced severe CR symptoms on Salinas and mild symptoms on Green Lake. All strains were gram-negative, aerobic, oxidase positive, and catalase positive and reduced nitrate to ammonia. Whole-cell fatty acid compositions were similar for all strains and resembled that of
Pseudomonas paucimobilis
. Since this fatty acid pattern is unique, it is suggested that CR of lettuce is caused by strains of the same bacterium in Florida, New York, Wisconsin, and California.
Non-proton-motive-force-dependent sodium efflux from the ruminal bacterium Streptococcus bovis: bound versus free pools
Authors: Strobel H J , Russell J B
Published: January 2020

Growing cells of Streptococcus bovis JB1 had a sodium content of 1,125 nmol/mg of protein and, based on a ratio of cell volume to protein of 4.3 microliters/mg, the apparent intracellular sodium concentration was more than 240 mM. Much of this sodium could not be removed by water washing even if cells were boiled or treated with the pore-forming ionophore, gramicidin, but it could be exchanged for potassium. Stationary cultures had a 2.6-microliters volume per milligram of protein and a total sodium content of 410 mM. When stationary cultures were energized with glucose at pH 6 to 8, sodium (more than 200 mM) was expelled within 2 min, and it appeared that growing cells had a very small pool of free intracellular sodium. Sodium-proton antiport activity could not be demonstrated with a sodium pulse, and the protonophore SF6847, valinomycin, and the H+-ATPase inhibitor dicyclohexylcarbodiimide (DCCD) had little effect on sodium efflux, even though these inhibitors greatly reduced the proton-motive force. SF6847, valinomycin, and DCCD had little effect on intracellular ATP, but iodoacetate, an inhibitor of glycolysis, decreased ATP as well as sodium efflux. Stationary cells from sodium-deficient medium expelled little sodium after glucose addition and had 35% more ATP than stationary cells which were grown in sodium medium and expelled sodium. An artificial electrochemical gradient of sodium was able to drive ATP synthesis in stationary cells, and this ATP formation was not sensitive to DCCD. These results indicated that bacteria could have a significant pool of bound sodium and that sodium expulsion from S. bovis was directly coupled to ATP hydrolysis.
Localization of Separate Genetic Loci for Reduced Sensitivity towards Small Isometric-Headed Bacteriophage sk1 and Prolate-Headed Bacteriophage c2 on pGBK17 from
Lactococcus lactis
subsp.
lactis
KR2
Authors: McKay Larry L. , Bohanon Michael J. , Polzin Kayla M. , Rule Patricia L. , Baldwin Kathleen A.
Published: January 2020

The mechanism of reduced sensitivity to the small isometric-headed bacteriophage sk1 encoded on a 19-kilobase (kb)
Hpa
II fragment subcloned from pKR223 of
Lactococcus lactis
subsp.
lactis
KR2 was examined. The reduced sensitivity to phage sk1 was due to a modest restriction/modification (R/M) system that was not active against prolate-headed phage c2. The genetic loci for the R/M system against sk1 and the abortive phage infection (Abi) mechanism effective against phage c2 were then localized by restriction mapping, subcloning, and deletion analysis. The restriction gene was localized to a region of a 2.7-kb
Eco
RV fragment and included an
Eco
RI site within that fragment. The modification gene was found to be physically separable from the restriction gene and was present on a 1.75-kb
Bst
EII-
Xba
I fragment. The genetic locus for the Abi phenotype against phage c2 was localized to a region containing a 1.3-kb
Eco
RI fragment. Attempts to clone the c2 Abi mechanism independent of the sk1 R/M system were unsuccessful, suggesting that expression of the
abi
genes required sequences upstream of the modification gene. Some pGBK17 (vector pGB301 plus a 19-kb
Hpa
II insert fragment) transformants exhibited the R/M system against phage sk1 but lost the Abi mechanism against phage c2. These transformants contained a 1.2- to 1.3-kb insertion in the Abi region. The data identified genetic loci on a cloned 19-kb
Hpa
II fragment responsible for restriction activity and for modification activity against a small isometric-headed phage and for Abi activity against prolate-headed phage c2. A putative insertion element was also found to inactivate the
abi
gene(s).
Toxicity of Trichloroethylene to
Pseudomonas putida
F1 Is Mediated by Toluene Dioxygenase
Authors: Wackett Lawrence P. , Householder Steven R.
Published: January 2020

Trichloroethylene was metabolically activated by toluene dioxygenase to produce toxic effects in
Pseudomonas putida
F1. Cytotoxicity was indicated by growth inhibition and by the covalent modification of cellular molecules in
P. putida
F1 exposed to [
14
C]trichloroethylene. With a toluene dioxygenase mutant, neither growth inhibition nor alkylation of intracellular molecules was observed.
Extraction from prawn shells of substances cryoprotective for Vibrio cholerae
Authors: Shimodori S , Moriya T , Kohashi O , Faming D , Amako K
Published: January 2020

Substances cryoprotective for Vibrio cholerae were detected from prawn shells immersed in phosphate-buffered saline. This cryoprotective activity was heat resistant and sensitive to treatment with trypsin. For the exhibition of its full activity, the presence of Mg ion was indispensable. The cryoprotective activity of this substance was more active than that of other known cryoprotectants, like glycerol or serum.
Anaerobic dechlorination of 2,4-dichlorophenol in freshwater sediments in the presence of sulfate
Authors: Kohring G W , Zhang X M , Wiegel J
Published: January 2020

In the presence of added sulfate, 2,4-dichlorophenol and 4-chlorophenol were transformed stoichiometrically to 4-chlorophenol and phenol, respectively, in anaerobic freshwater lake sediments between 18 and 40 degrees C. The concomitantly occurring sulfate reduction reduced the initial sulfate concentration from 25 mM to about 6 to 8 mM and depressed methane formation.
Binding and aggregation of the 25-kilodalton toxin of Bacillus thuringiensis subsp. israelensis to cell membranes and alteration by monoclonal antibodies and amino acid modifiers
Authors: Chow E , Singh G J , Gill S S
Published: January 2020

The 25-kilodalton toxin of Bacillus thuringiensis subsp. israelensis binds irreversibly to Aedes albopictus cells, Choristoneura fumiferana cells, and erythrocytes. The binding to cells increased with both toxin concentration and time and when the cells were first preincubated with unlabeled toxin. Binding data indicated a two- to threefold increase in the rate of binding after the amount of the membrane-bound toxin reached approximately 3.5 fmol/3 x 10(5) A. albopictus cells or 3.3. fmol/2 x 10(5) C. fumiferana cells. When this level of bound toxin was reached, the toxins also began forming aggregates at the cell membrane. The toxin aggregates were extracted with 10% Triton X-100 and separated from the monomers with a 5 to 20% sucrose density gradient. The toxin aggregates isolated from A. albopictus and C. fumiferana cell membranes were ca. 400 kilodaltons, while those isolated from human erythrocytes were significantly smaller. The proportion of the toxin found in aggregate form increased rapidly with the amount of toxin bound; however, the molecular size of the aggregates remained constant. Eleven monoclonal antibodies raised against the native form of the toxin blocked 80 to 97% of the toxin binding to cells. The epitope of one of these monoclonal antibodies was mapped to a domain which included the cysteine, suggesting the importance of the domain around this amino acid to binding. Toxin binding and cell lysis were also inhibited by treating the toxin with HgCl2, further indicating the importance of the C-terminal hydrophobic cysteine-containing domain in cytolytic activity of the 25-kilodalton protein.
Physicochemical surface properties of nonencapsulated and encapsulated coagulase-negative staphylococci
Authors: van der Mei H C , Brokke P , Dankert J , Jan F J , Rouxhet P G , Busscher H J
Published: January 2020

Cell surfaces of three nonencapsulated and three encapsulated coagulase-negative staphylococci were characterized by their surface free energies, zeta potentials, and elemental and molecular compositions. Surface free energies were calculated from contact angle measurements with various liquids. All six strains showed a high surface free energy (103 to 126 mJ.m-2), estimated from the concept of polar and dispersion components. However, the hydrogen-donating surface free energy parameter was zero for all nonencapsulated strains. The zeta potential profile measured as a function of pH in phosphate-buffered saline for the nonencapsulated strains was completely different from that of the encapsulated strains. X-ray photoelectron spectroscopy was used to determine the elements (O, C, N, P, and K) in the outer 2 to 5 nm of the freeze-dried cell surface and showed that the hydrophilic character of the staphylococci was related to oxygen (O/C ratio, approximately 0.52)- and phosphorus (P/C ratio, approximately 0.03)-containing groups. Both the elemental and molecular characterizations (done by infrared spectroscopy) pointed to the presence of polysaccharides and polypeptides on the cell surface of the nonencapsulated and encapsulated strains.
Sequential Photochemical and Microbial Degradation of Organic Molecules Bound to Humic Acid
Authors: Amador José A. , Alexander Martin , Zika Rod G.
Published: January 2020

We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-
14
C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of
14
C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of
A
330
. Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid.
Physiological Properties of a Mutant of
Pachysolen tannophilus
Deficient in NADPH-Dependent
d
-Xylose Reductase
Authors: Schneider Henry , Lee Hung , Barbosa Maria de F. S. , Kubicek C. P. , James Allen P.
Published: January 2020

A
d
-xylose reductase mutant of
Pachysolen tannophilus
was isolated on the basis of its poor growth on
d
-xylose but normal growth on xylitol and
d
-glucose. Fractionation of cell extracts indicated that the mutant was deficient in
d
-xylose reductase activity that used NADPH exclusively as a cofactor, but not in activity that used both NADH and NADPH. Mutant cultures grown on
d
-xylose as the sole carbon source exhibited some properties that would be desired in improved strains. Growth rate, growth yield, and
d
-xylose consumption rate of the mutant were less sensitive than those of the wild type to changes in aeration rate.
d
-Xylose was utilized more efficiently in that less of a by-product, xylitol, was produced. In addition, under low aeration conditions, more ethanol was produced. A disadvantage was a relatively slow rate of
d
-xylose utilization.
Dissimilatory nitrate reduction by Propionibacterium acnes
Authors: Allison C , Macfarlane G T
Published: January 2020

Propionibacterium acnes P13 was isolated from human feces. The bacterium produced a particulate nitrate reductase and a soluble nitrite reductase when grown with nitrate or nitrite. Reduced viologen dyes were the preferred electron donors for both enzymes. Nitrous oxide reductase was never detected. Specific growth rates were increased by nitrate during growth in batch culture. Culture pH strongly influenced the products of dissimilatory nitrate reduction. Nitrate was principally converted to nitrite at alkaline pH, whereas nitrous oxide was the major product of nitrate reduction when the bacteria were grown at pH 6.0. Growth yields were increased by nitrate in electron acceptor-limited chemostats, where nitrate was reduced to nitrite, showing that dissimilatory nitrate reduction was an energetically favorable process in P. acnes. Nitrate had little effect on the amounts of fermentation products formed, but molar ratios of acetate to propionate were higher in the nitrate chemostats. Low concentrations of nitrite (ca. 0.2 mM) inhibited growth of P. acnes in batch culture. The nitrite was slowly reduced to nitrous oxide, enabling growth to occur, suggesting that denitrification functions as a detoxification mechanism.
Immunological identification and distribution of dissimilatory heme cd1 and nonheme copper nitrite reductases in denitrifying bacteria
Authors: Coyne M S , Arunakumari A , Averill B A , Tiedje J M
Published: January 2020

Polyclonal antibodies were used to identify heme or copper nitrite reductases in the following groups: 23 taxonomically diverse denitrifiers from culture collections, 100 numerically dominant denitrifiers from geographically diverse environments, and 51 denitrifiers from a culture collection not selected for denitrification. Antisera were raised against heme nitrite reductases from Pseudomonas aeruginosa and Pseudomonas stutzeri and against copper nitrite reductase from Achromobacter cycloclastes. Nitrite reductases were identified by Western immunoblot. Diethyldithiocarbamate, which specifically inhibits copper nitrite reductases, was used to confirm the immunological characterization and determine which type was present in strains nonreactive with any antiserum. For groups in which the type of nitrite reductase has not been previously described, we found that Alcaligenes eutrophus, Bacillus azotoformans, Bradyrhizobium japonicum, Corynebacterium nephridii, and Rhizobium spp. contained copper nitrite reductase, while Aquaspirillum itersonii, Flavobacterium spp., and Pseudomonas fluorescens contained heme nitrite reductase. Heme nitrite reductases dominated, regardless of soil type or geographic origin. They occurred in 64 and 92%, respectively, of denitrifiers in the numerically dominant and nonselected collections. The two nitrite reductase types were mutually exclusive in individual bacteria, but both appeared in different strains from the Alcaligenes and Pseudomonas genera. The heme type predominated in Pseudomonas strains. The heme-type nitrite reductase appeared more conserved if judged by similarities in molecular weights and immunological reactions. The Cu type was found in more taxonomically unrelated strains and varied in molecular weight and antiserum recognition.
Influence of Water Potential on γ-Decalactone Production by the Yeast
Sporidiobolus salmonicolor
Authors: Gervais P. , Battut G.
Published: January 2020

The influence of water potential on γ-decalactone production by the yeast
Sporidiobolus salmonicolor
cultivated in a liquid medium was evaluated by gas-chromatographic analysis. Modifications in water potential led to a number of variations in the aroma production. Maximum extracellular production occurred at water activity (a
w
) with a value of 0.99. Further analyses revealed an important phenomenon of cellular accumulation of aroma for a
w
values between 0.97 and 0.99.
Immunochemical Localization of Nitrogenase in Marine
Trichodesmium
Aggregates: Relationship to N
2
Fixation Potential
Authors: Paerl Hans W. , Priscu John C. , Brawner Diane L.
Published: January 2020

Colonial aggregation among nonheterocystous filaments of the planktonic marine cyanobacterium
Trichodesmium
is known to enhance N
2
fixation, mediated by the O
2
-sensitive enzyme complex nitrogenase. Expression of nitrogenase appears linked to the formation of O
2
-depleted microzones within aggregated bacterium-associated colonies. While this implies a mechanism by which nonheterocystous N
2
fixation can take place in an oxygenated water column, both the location and regulation of the N
2
-fixing apparatus remain unknown. We used an antinitrogenase polyclonal antibody together with postsection immunocolloidal gold staining and transmission electron microscopy to show that (i) virtually all
Trichodesmium
cells within a colony possessed nitrogenase, (ii) nitrogenase showed no clear intracellular localization, and (iii) certain associated bacteria contained nitrogenase. Our findings emphasize the critical role coloniality plays in regulating nitrogenase expression in nature. We interpret the potential for a large share of
Trichodesmium
cells to fix N
2
as an opportunistic response to the dynamic nature of the sea state; during quiescent conditions, aggregation and consequent expression of nitrogenase can proceed rapidly.
Response of Plant-Colonizing Pseudomonads to Hydrogen Peroxide
Authors: Katsuwon J. , Anderson A. J.
Published: January 2020

Colonization of plant root surfaces by
Pseudomonas putida
may require mechanisms that protect this bacterium against superoxide anion and hydrogen peroxide produced by the root. Catalase and superoxide dismutase may be important in this bacterial defense system. Stationary-phase cells of
P. putida
were not killed by hydrogen peroxide (H
2
O
2
) at concentrations up to 10 mM, and extracts from these cells possessed three isozymic bands (A, B, and C) of catalase activity in native polyacrylamide gel electrophoresis. Logarithmic-phase cells exposed directly to hydrogen peroxide concentrations above 1 mM were killed. Extracts of logarithmic-phase cells displayed only band A catalase activity. Protection against 5 mM H
2
O
2
was apparent after previous exposure of the logarithmic-phase cells to nonlethal concentrations (30 to 300 μM) of H
2
O
2
. Extracts of these protected cells possessed enhanced catalase activity of band A and small amounts of bands B and C. A single form of superoxide dismutase and isoforms of catalase were apparent in extracts from a foliar intercellular pathogen,
Pseudomonas syringae
pv.
phaseolicola.
The mobilities of these
P. syringae
enzymes were distinct from those of enzymes in
P. putida
extracts.