bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Hyperbaric Pressure on a Deep-Sea Archaebacterium in Stainless Steel and Glass-Lined Vessels
Authors: Nelson Chad M. , Schuppenhauer Michael R. , Clark Douglas S.
Published: January 2020

The effects of hyperbaric helium pressures on the growth and metabolism of the deep-sea isolate ES4 were investigated. In a stainless steel reactor, cell growth was completely inhibited but metabolic gas production was observed. From 85 to 100°C, CO
2
production proceeded two to three times faster at 500 atm (1 atm = 101.29 kPa) than at 8 atm. At 105°C, no CO
2
was produced until the pressure was increased to 500 atm. Hydrogen and H
2
S were also produced biotically but were not quantifiable at pressures above 8 atm because of the high concentration of helium. In a glass-lined vessel, growth occurred but the growth rate was not accelerated by pressure. In most cases at temperatures below 100°C, the growth rate was lower at elevated pressures; at 100°C, the growth rates at 8, 250, and 500 atm were nearly identical. Unlike in the stainless steel vessel, CO
2
production was exponential during growth and continued for only a short time after growth. In addition, relatively little H
2
was produced in the glass-lined vessel, and there was no growth or gas production at 105°C at any pressure. The behavior of ES4 as a function of temperature and pressure was thus very sensitive to the experimental conditions.
Purification and characterization of an endopeptidase from Lactococcus lactis subsp. cremoris Wg2
Authors: Tan P S , Pos K M , Konings W N
Published: January 2020

An endopeptidase has been purified to homogeneity from a crude cell extract of Lactococcus lactis subsp. cremoris Wg2 by a procedure that includes diethyl-aminoethane-Sephacel chromatography, phenyl-Sepharose chromatography, hydroxylapatite chromatography, and fast protein liquid chromatography over an anion-exchange column and a hydrophobic-interaction column. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a molecular mass of the purified enzyme of 70,000 Da. The endopeptidase can degrade several oligopeptides into various tetra-, tri-, and dipeptides. The endopeptidase has no aminopeptidase, carboxypeptidase, dipeptidase, or tripeptidase activity. It is optimally active at pH 6.0 to 6.5 and in the temperature range of 30 to 38 degrees C. The enzyme is inactivated by the chemical agents 1,10-phenanthroline, ethylenedinitrilotetraacetate, beta-mercaptoethanol, and phenylmethylsulfonyl fluoride and is inhibited by Cu2+ and Zn2+. The ethylenedinitrilotetraacetate- or 1,10-phenanthroline-treated enzyme can be reactivated by Co2+. Immunoblotting with specific antibodies raised against the purified endopeptidase indicated that the enzyme is also present in other Lactococcus spp., as well as in Lactobacillus spp. and Streptococcus salivarius subsp. thermophilus.
Nitrification at Low pH by Aggregated Chemolithotrophic Bacteria
Authors: De Boer W. , Gunnewiek P. J. A. Klein , Veenhuis M. , Bock E. , Laanbroek H. J.
Published: January 2020

A study was performed to gain insight into the mechanism of acid-tolerant, chemolithotrophic nitrification. Microorganisms that nitrified at pH 4 were enriched from two Dutch acid soils. Nitrate production in the enrichment cultures was indicated to be of a chemolithoautotrophic nature as it was (i) completely inhibited by acetylene at a concentration as low as 1 μmol/liter and (ii) strongly retarded under conditions of carbon dioxide limitation. Electron microscopy of the enrichment cultures showed the presence of bacteria that were morphologically similar to strains of known chemolithotrophic nitrifying genera. Many of the enriched bacteria, in particular those that were identified as ammonium oxidizers, were aggregated. Filtration experiments indicated that aggregated cells were able to nitrify at low pH, whereas single cells were not. It is hypothesized that cells inside the aggregates are protected against the toxicity of nitrous acid. Nitrification by aggregated chemolithoautotrophic bacteria may be the dominating process of nitrate formation in many acid soils as it does not appear to depend on the existence of microsites of high pH (acid-sensitive autotrophic nitrification) or on the availability of organic carbon (heterotrophic nitrification).
Nisin treatment for inactivation of Salmonella species and other gram-negative bacteria
Authors: Stevens K A , Sheldon B W , Klapes N A , Klaenhammer T R
Published: January 2020

Nisin, produced by Lactococcus lactis subsp. lactis, has a broad spectrum of activity against gram-positive bacteria and is generally recognized as safe in the United States for use in selected pasteurized cheese spreads to control the outgrowth and toxin production of Clostridium botulinum. This study evaluated the inhibitory activity of nisin in combination with a chelating agent, disodium EDTA, against several Salmonella species and other selected gram-negative bacteria. After a 1-h exposure to 50 micrograms of nisin per ml and 20 mM disodium EDTA at 37 degrees C, a 3.2- to 6.9-log-cycle reduction in population was observed with the species tested. Treatment with disodium EDTA or nisin alone produced no significant inhibition (less than 1-log-cycle reduction) of the Salmonella and other gram-negative species tested. These results demonstrated that nisin is bactericidal to Salmonella species and that the observed inactivation can be demonstrated in other gram-negative bacteria. Applications involving the simultaneous treatment with nisin and chelating agents that alter the outer membrane may be of value in controlling food-borne salmonellae and other gram-negative bacteria.
Low- and high-affinity transport systems for citric acid in the yeast Candida utilis
Authors: Cássio F , Leáo C
Published: January 2020

Citric acid-grown cells of the yeast Candida utilis induced two transport systems for citric acid, presumably a proton symport and a facilitated diffusion system for the charged and the undissociated forms of the acid, respectively. Both systems could be observed simultaneously when the transport was measured at 25 degrees C with labelled citric acid at pH 3.5 with the following kinetic parameters: for the low-affinity system, Vmax, 1.14 nmol of undissociated citric acid s-1 mg (dry weight) of cells-1, and Km, 0.59 mM undissociated acid; for the high-affinity system, Vmax, 0.38 nmol of citrate s-1 mg (dry weight) of cells-1, and Km, 0.056 mM citrate. At high pH values (above 5.0), the low-affinity system was absent or not measurable. The two transport systems exhibited different substrate specificities. Isocitric acid was a competitive inhibitor of citric acid for the high-affinity system, suggesting that these tricarboxylic acids used the same transport system, while aconitic, tricarballylic, trimesic, and hemimellitic acids were not competitive inhibitors. With respect to the low-affinity system, isocitric acid, L-lactic acid, and L-malic acid were competitive inhibitors, suggesting that all of these mono-, di-, and tricarboxylic acids used the same low-affinity transport system. The two transport systems were repressed by glucose, and as a consequence diauxic growth was observed. Both systems were inducible, and not only citric acid but also lactic acid and malic acid may induce those transport systems. The induction of both systems was not dependent on the relative concentration of the anionic form(s) and of undissociated citric acid in the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)
Limited bacterial mineralization of fungal degradation intermediates from synthetic lignin
Authors: Rüttimann C , Vicuña R , Mozuch M D , Kirk T K
Published: January 2020

The ability of selected bacterial strains and consortia to mineralize degradation intermediates produced by Phanerochaete chrysosporium from 14C-labeled synthetic lignins was studied. Three different molecular weight fractions of the intermediates were subjected to the action of the bacteria, which had been grown on a lignin-related dimeric compound. Two consortia isolated from wood being decayed naturally by a Ganoderma species of white rot fungus (the palo podrido system) mineralized 10 to 11% of the fraction with a molecular weight of approximately 500 but less than 4% of the higher- and lower-molecular-weight fractions. The consortia mineralized 5 to 9% of the original lignins. The ability of two pseudomonads isolated earlier from lignin-rich environments to mineralize the original lignins or fungus degradation products was much lower.
New Culture Medium Containing Ionic Concentrations of Nutrients Similar to Concentrations Found in the Soil Solution
Authors: Angle J. Scott , McGrath Stephen P. , Chaney Rufus L.
Published: January 2020

A new growth medium which closely approximates the composition of the soil solution is presented. This soil solution equivalent (SSE) medium contains the following components (millimolar): NO
3
, 2.5; NH
4
, 2.5; HPO
4
, 0.005; Na, 2.5; Ca, 4.0; Mg, 2.0; K, 0.503; Cl, 4.0; SO
4
, 5.0; ethylenediamine-di(
o
-hydroxyphenylacetic acid), 0.02; and MES [2-(
N
-morpholino)ethanesulfonic acid] (to maintain the pH at 6.0), 10, plus 0.1% arabinose. The advantages of the SSE medium are discussed.
Purification and characterization of the N-methylcarbamate hydrolase from Pseudomonas strain CRL-OK
Authors: Mulbry W W , Eaton R W
Published: January 2020

A unique cytosolic enzyme that hydrolyzes the carbamate linkage of the insecticide carbaryl (1-naphthyl N-methylcarbamate) was purified from extracts of Pseudomonas sp. strain CRL-OK. Substrates of the hydrolase include the N-methylcarbamate pesticides carbofuran and aldicarb but not the phenylcarbamate isopropyl m-chlorocarbanilate, the thiocarbamate S-ethyl N,N-dipropylthiocarbamate, or the dimethylcarbamate o-nitrophenyldimethylcarbamate.
Survival and catabolic activity of natural and genetically engineered bacteria in a laboratory-scale activated-sludge unit
Authors: McClure N C , Fry J C , Weightman A J
Published: January 2020

The survival of selected naturally occurring and genetically engineered bacteria in a fully functional laboratory-scale activated-sludge unit (ASU) was investigated. The effect of the presence of 3-chlorobenzoate (3CB) on the survival of Pseudomonas putida UWC1, with or without a chimeric plasmid, pD10, which encodes 3CB catabolism, was determined. P. putida UWC1(pD10) did not enhance 3CB breakdown in the ASU, even following inoculation at a high concentration (3 x 10(8) CFU/ml). The emergence of a natural, 3CB-degrading population appeared to have a detrimental effect on the survival of strain UWC1 in the ASU. The fate of two 3CB-utilizing bacteria, derived from activated-sludge microflora, was studied in experiments in which these strains were inoculated into the ASU. Both strains, AS2, an unmanipulated natural isolate which flocculated readily in liquid media, and P. putida ASR2.8, a transconjugant containing the recombinant plasmid pD10, survived for long periods in the ASU and enhanced 3CB breakdown at 15 degrees C. The results reported in this paper illustrate the importance of choosing strains which are well adapted to environmental conditions if the use of microbial inoculants for the breakdown of target pollutants is to be successful.
Involvement of an Extracellular Glucan Sheath during Degradation of
Populus
Wood by
Phanerochaete chrysosporium
Authors: Ruel Katia , Joseleau Jean-Paul
Published: January 2020

Observations by transmission electron microscopy of wood samples of
Populus tremula
inoculated with the white rot fungus
Phanerochaete chrysosporium
showed that, at certain stages of their growth cycle, hyphae were encapsulated by a sheath which seems to play an active role in the wood cell wall degradation. Chemical and immunochemical techniques and
13
C nuclear magnetic resonance spectroscopy were applied to demonstrate the β-1,3-1,6-
d
-glucan nature of the sheath. Double-staining methods revealed the interaction between the extracellular peroxidases involved in lignin degradation and the glucan mucilage. The glucan was also shown to establish a material junction between the fungus and the wood cell wall. It was concluded that, by means of these interactions, the sheath provides a transient junction between the hyphae and the wood, thus establishing a point of attachment to the site of the degradation. The association of peroxidases to the glucan matrix is in favor of the role of the sheath as a supporting structure. Furthermore, that the sheath was hydrolyzed during the attack demonstrated its active role both in providing the H
2
O
2
necessary to the action of peroxidases and in providing a mode of transport of the fungal enzymes to their substrates at the surface of the wood cell wall.
Comparative study of a DNA hybridization method and two isolation procedures for detection of Yersinia enterocolitica O:3 in naturally contaminated pork products
Authors: Nesbakken T , Kapperud G , Dommarsnes K , Skurnik M , Hornes E
Published: January 2020

We compared a DNA-DNA hybridization assay, using a synthetically produced oligonucleotide probe, and two conventional isolation procedures (methods A and B) with regard to their relative efficiency in detecting Yersinia enterocolitica O:3 in naturally contaminated pork products. Method A was as described by Wauters et al. (Appl. Environ. Microbiol. 54:851-854, 1988). Method B has been recommended by the Nordic Committee on Food Analysis (method no. 117, 1987). The genetic probe was used in a colony hybridization assay to detect virulent yersiniae at each of the isolation steps with composed methods A and B. A total of 50 samples of raw pork products obtained from 13 meat-processing factories in Norway were examined. Y. enterocolitica serogroup O:3, biovar 4, was isolated from altogether 9 (18.0%) of the samples by using the two isolation procedures. In contrast, colony hybridization using the genetic probe indicated that 30 (60.0%) of the samples contained virulent yersiniae. All samples which were positive on cultivation were also positive by hybridization. The results indicate that the occurrence of pathogenic Y. enterocolitica in Norwegian pork products is substantially higher than previously demonstrated and, therefore, reinforce our suggestion that pork products represent an important potential source of human infection in Norway. The results also indicate that the use of conventional isolation procedures may lead to considerable underestimation of pathogenic Y. enterocolitica in pork products.
Physiological Diversity and Distributions of Heterotrophic Bacteria in Deep Cretaceous Sediments of the Atlantic Coastal Plain
Authors: Fredrickson James K. , Balkwill David L. , Zachara John M. , Li Shu-Mei W. , Brockman Fred J. , Simmons Mary A.
Published: January 2020

A series of 23 intact core segments was obtained from two distinct deep subsurface geological formations, the Middendorf and the Cape Fear formations, underlying the southeastern coastal plain of South Carolina. The Middendorf formation in this region consists of permeable, saturated, sandy sediments; the Cape Fear formation consists mainly of less permeable sediments. The core segments were separated by vertical distances ranging from several centimeters to 48 m. Aerobic chemoheterotrophic bacteria were enumerated on a dilute medium, and populations ranged from 3.1 to 6.4 log CFU g of sediment
-1
in the Middendorf cores and from below detection to 4.3 log CFU g
-1
in the Cape Fear cores. A total of 198 morphologically distinct colony types were isolated, purified, and subjected to 108 different physiological measurements. The isolates from the two formations were distinct (i.e., they produced substantially different response patterns to the various physiological measurements), as were those in different core samples from the same formation. Cluster analysis revealed 21 different biotypes based on similarities of 75% or higher in response patterns to 21 physiological assays. One biotype contained 57 (29%) of the subsurface isolates, 10 biotypes contained 5 or more isolates, and the remainder had 4 or fewer. The organic compounds that were most commonly metabolized by the subsurface bacteria included Tween 40 (85%) and β-hydroxybutyric acid (60%). Organic acids, in general, were also commonly metabolized by the subsurface bacteria. Isolates from the Cape Fear core segments were capable of metabolizing a higher percentage of the substrates than were bacteria isolated from the Middendorf formation. Although the heterogeneous distributions of bacteria in deep subsurface sediments may make it difficult to use aquifer microcosms to predict in situ biotransformation rates, the diversity of the physiological properties of these organisms offers promise for in situ remediation of contaminants.
Homologous Streptomycin Resistance Gene Present among Diverse Gram-Negative Bacteria in New York State Apple Orchards
Authors: Norelli John L. , Burr Thomas J. , Lo Cicero Adriana M. , Gilbert Mathew T. , Katz Barbara H.
Published: January 2020

The streptomycin resistance gene of
Pseudomonas syringae
pv. papulans Psp36 was cloned into
Escherichia coli
and used to develop a 500-bp DNA probe that is specific for streptomycin resistance in
P. syringae
pv. papulans. The probe is a portion of a 1-kb region shared by three different DNA clones of the resistance gene. In Southern hybridizations, the probe hybridized only with DNA isolated from streptomycin-resistant strains of
P. syringae
pv. papulans and not with the DNA of streptomycin-sensitive strains. Transposon insertions within the region of DNA shared by the three clones resulted in loss of resistance to streptomycin. Colony hybridization of bacteria isolated from apple leaves and orchard soil indicated that 39% of 398 streptomycin-resistant bacteria contained DNA that hybridized to the probe. These included all strains of
P. syringae
pv. papulans and some other fluorescent pseudomonads and nonfluorescent gram-negative bacteria, but none of the gram-positive bacteria. The same-size restriction fragments hybridized to the probe in
P. syringae
pv. papulans. Restriction fragment length polymorphism of this region was occasionally observed in strains of other taxonomic groups of bacteria. In bacteria other than
P. syringae
pv. papulans, the streptomycin resistance probe hybridized to different-sized plasmids and no relationship between plasmid size and taxonomic group or between plasmid size and orchard type, soil association, or leaf association could be detected.
Pseudomonas stutzeri
YPL-1 Genetic Transformation and Antifungal Mechanism against
Fusarium solani
, an Agent of Plant Root Rot
Authors: Lim Ho-Seong , Kim Yong-Su , Kim Sang-Dal
Published: January 2020

An actively antagonistic bacterium that could be used as a biocontrol agent against
Fusarium solani
, which causes root rots with considerable losses in many important crops, was isolated from a ginseng rhizosphere and identified as a strain of
Pseudomonas stutzeri
. In several biochemical tests with culture filtrates of
P. stutzeri
YPL-1 and in mutational analyses of antifungal activities of reinforced or defective mutants, we found that the anti-
F. solani
mechanism of the bacterium may involve a lytic enzyme rather than a toxic substance or antibiotic.
P. stutzeri
YPL-1 produced extracellular chitinase and laminarinase when grown on different polymers such as chitin, laminarin, or
F. solani
mycelium. These lytic extracellular enzymes markedly inhibited mycelial growth rather than spore germination and also caused lysis of
F. solani
mycelia and germ tubes. Scanning electron microscopy revealed degradation of the
F. solani
mycelium. Abnormal hyphal swelling and retreating were caused by the lysing agents from
P. stutzeri
YPL-1, and a penetration hole was formed on the hyphae in the region of interaction with the bacterium; the walls of this region were rapidly lysed, causing leakage of protoplasm. Genetically bred
P. stutzeri
YPL-1 was obtained by transformation of the bacterium with a broad-host-range vector, pKT230. Also, the best conditions for the transformation were investigated.
Rapid In Situ Assay for Indoleacetic Acid Production by Bacteria Immobilized on a Nitrocellulose Membrane
Authors: Bric John M. , Bostock Richard M. , Silverstone Sara E.
Published: January 2020

We have developed a new assay that differentiates between indoleacetic acid (IAA)-producing and -nonproducing bacteria on a colony plate lift. Medium supplemented with 5 mM L-tryptophan is inoculated with isolates of interest, overlaid with a nitrocellulose membrane, and then incubated until bacterial colonies reach 1 to 2 mm in diameter. The membrane is removed to a filter paper saturated with Salkowski reagent and incubated until distinct red haloes form around the colonies. The colorimetric reaction to IAA is limited to a region immediately surrounding each colony, is specific to isolates producing IAA, occurs within 1 h after the membrane is placed in the reagent, and is sensitive to as little as 50 pmol of IAA in a 2-mm
2
spot. We have used this assay for quantifying epiphytic and endophytic populations of IAA-producing isolates of
Pseudomonas syringae
subsp.
savastanoi
and for detecting IAA-producing colonies of other pseudomonads and
Erwinia herbicola
. The assay provides a rapid and convenient method to screen large numbers of bacteria.
Use of Polymerase Chain Reaction To Detect the Take-All Fungus,
Gaeumannomyces graminis
, in Infected Wheat Plants
Authors: Schesser Kurt , Luder Andreas , Henson Joan M.
Published: January 2020

Gaeumannomyces graminis
, the causative agent of take-all disease of wheat, barley, and oats, was detected in infected wheat seedlings by using the polymerase chain reaction to amplify
Gaeumannomyces
-specific DNA fragments. Nested primers and two rounds of amplification were used to amplify two fragments, approximately 287 and 188 bp in size, from
G. graminis
-infected wheat seedlings. The use of nested primers greatly decreased the number of nonspecific amplification products. Polymerase chain reaction products were not obtained with DNA from seedlings infected with several other phytopathogenic fungi or with DNA from uninfected seedlings. Amplified products were visualized on agarose gels, and their identities were confirmed by DNA hybridization. This method did not require culturing the fungus and has potential for detecting
G. graminis
in infested wheat, barley, or oat fields.
Interactions between Pseudomonas aeruginosa and iodophor germicides in milking parlor udder wash water systems
Authors: Hicks C R , Eberhart R J , Erskine R J , Spencer S B
Published: January 2020

In a field study of 29 dairy farms, Pseudomonas aeruginosa was isolated more frequently (P = 0.05) from milking parlor udder wash water systems containing iodophor germicides than from those with no germicide. Most available iodine (AI2) concentrations were below the recommended level of 25 ppm (25 microgram/ml). Rubber and polyvinyl chloride hoses caused rapid decreases in the AI2 concentrations of 25 ppm iodophor solutions. AI2 dropped from 25 ppm to 6 ppm or less in 240 min for solutions contained in either polyvinyl chloride or rubber, compared with solutions in glass, which were unchanged in 240 min. Addition of inactivated iodophor solution to aqueous cultures resulted in significantly higher (P less than 0.05) numbers of P. aeruginosa at 10 and 24 h postinoculation. P. aeruginosa was grown in polyvinyl chloride tubing and exposed twice daily to 0, 10, or 25 ppm of AI2. None of the exposure concentrations eliminated the bacteria from the hoses, and bacterial numbers were not significantly different in hoses exposed to 0 and 10 ppm by the eighth treatment day. Bacteria taken from the water in these hoses were exposed to different concentrations of iodophor solution. Iodophor concentrations which will kill 50% of P. aeruginosa cultures previously exposed to 0, 10, and 25 ppm of AI2 were predicted to be 3.0, 11.8, and 20.8 ppm, respectively.
Controlling Wine Malolactic Fermentation with Nisin and Nisin-Resistant Strains of
Leuconostoc oenos
Authors: Daeschel Mark A. , Jung Dong-Sun , Watson Barney T.
Published: January 2020

The polypeptide nisin (100 U/ml) prevented malolactic fermentation in wines by indigenous or intentionally added lactic acid bacteria. Nisin (100 U/ml)-resistant mutants of
Leuconostoc oenos
were obtained and used with nisin in wine to carry out a pure-culture malolactic fermentation in the presence or absence of other lactic acid bacteria. Nisin degradation by mutants was not observed, and residual nisin was detectable in wines 4 months after it was added. Results indicated that nisin or nisin with resistant bacterial starter cultures can be used to control malolactic fermentation in wines.
Temperature-Dependent Regulation by Molybdenum and Vanadium of Expression of the Structural Genes Encoding Three Nitrogenases in
Azotobacter vinelandii
Authors: Walmsley Jean , Kennedy Christina
Published: January 2020

Temperature affects the expression of the three different nitrogenases in
Azotobacter vinelandii.
Molybdenum repressed the
vnfH
and
anfH
operons relatively more at 30°C than at 20°C; at 14°C molybdenum did not repress these genes at all. Similarly, V repressed the
anf
operon at 30°C but not at 20 or 14°C. Mo was poorly transported into cells grown at the lower temperatures.
A. vinelandii
thus has the potential to synthesize any of the three nitrogenases at 14 to 20°C regardless of the presence of Mo or V.
Population Dynamics of
Rhizobium leguminosarum
Tn
5
Mutants with Altered Cell Surface Properties Introduced into Sterile and Nonsterile Soils
Authors: Postma J. , Hok-A-Hin C. H. , Schotman J. M. T. , Wijffelman C. A. , van Veen J. A.
Published: January 2020

The influence of cell surface properties on attachment to soil particles and on population dynamics of introduced bacteria was studied in sterilized and nonsterilized loamy sand and silt loam.
Rhizobium leguminosarum
RBL5523 and three Tn
5
mutants (RBL5762, RBL5810, and RBL5811) with altered cell surface properties were used. Cellulose fibrils were not produced by RBL5762. Both RBL5810 and RBL5811 produced 80 to 90% less soluble exopolysaccharides and RBL5811 had, in addition, an altered lipopolysaccharide composition. In sterilized soil the total number of cells as well as the number of particle-associated cells of RBL5523 and RBL5810 were, in general, higher as compared with cell numbers of RBL5762 and RBL5811. Differences between strains in percentage of particle-associated cells in sterilized soil were only found at high inoculum densities, when populations increased little. In the nonsterilized silt loam, final population sizes, as well as numbers of particle-associated cells, of the parental strain (RBL5523) were higher than those of strains with altered cell surface properties after 56 and 112 days of incubation. But in general, differences in survival among the strains were not very marked. The importance of association with soil particles or aggregates for the survival of introduced cells was affirmed by the pronounced increase of the percentage of particle-associated cells during incubation in nonsterilized as well as sterilized soil. However, no clear relation among altered cell surface properties, particle association, and survival was found.
Fermentation and aerobic metabolism of cellodextrins by yeasts
Authors: Freer S N
Published: January 2020

The fermentation and aerobic metabolism of cellodextrins by 14 yeast species or strains was monitored. When grown aerobically, Candida wickerhamii, C. guilliermondii, and C. molischiana metabolized cellodextrins of degree of polymerization 3 to 6. C. wickerhamii and C. molischiana also fermented these substrates, while C. guilliermondii fermented only cellodextrins of degree of polymerization less than or equal to 3. Debaryomyces polymorphus, Pichia guilliermondii, Clavispora lusitaniae, and one of two strains of Kluyveromyces lactis metabolized glucose, cellobiose, and cellotriose when grown aerobically. These yeasts also fermented these substrates, except for K. lactis, which fermented only glucose and cellobiose. The remaining species/strains tested, K. lactis, Brettano-myces claussenii, B. anomalus, K. dobzhanskii, Rhodotorula minuta, and Dekkera intermedia, both fermented and aerobically metabolized glucose and cellobiose. Crude enzyme preparations from all 14 yeast species or strains were tested for ability to hydrolyze cellotriose and cellotretose. Most of the yeasts produced an enzyme(s) capable of hydrolyzing cellotriose. However, with two exceptions, R. minuta and P. guilliermondii, only the yeasts that metabolized cellodextrins of degree of polymerization greater than 3 produced an enzyme(s) that hydrolyzed cellotretose.
Hydrolysis of carbaryl by a Pseudomonas sp. and construction of a microbial consortium that completely metabolizes carbaryl
Authors: Chapalamadugu S , Chaudhry G R
Published: January 2020

Two Pseudomonas spp. (isolates 50552 and 50581) isolated from soil degraded 1-naphthol and carbaryl, an N-methylcarbamate pesticide, respectively. They utilized these compounds as a sole source of carbon. 1-Naphthol was completely metabolized to CO2 by the isolate 50552, while the carbaryl was first hydrolyzed to 1-naphthol and then converted into a brown-colored compound by the isolate 50581. The colored metabolite was not degraded, but 1-naphthol produced by the isolate 50581 during the exponential phase of growth was metabolized by the isolate 50552. The two isolates were used to construct a bacterial consortium which completely catabolized carbaryl to CO2. No metabolite was detected in the cell cultures of the consortium. The isolate 50581 harbored a 50-kb plasmid pCD1, while no plasmid was detected in the isolate 50552. The isolated bacteria individually or as a consortium may be used for detoxification of certain industrial and agricultural wastes.
Leaching with
Penicillium simplicissimum
: Influence of Metals and Buffers on Proton Extrusion and Citric Acid Production
Authors: Franz Andreas , Burgstaller Wolfgang , Schinner Franz
Published: January 2020

In the presence of insoluble metal oxides (industrial filter dust, zinc oxide, synthetic mixture of metal oxides),
Penicillium simplicissimum
developed the ability to excrete considerable amounts of citric acid (>100 mM). Parallel with the increase of citric acid concentration in the culture broth, zinc was solubilized from zinc oxide. The adsorption of filter dust onto the mycelium (the pellets formed were less than 1 mm in diameter) was required for not only the citric acid excretion but also the leaching of zinc. When the filter dust was replaced with a synthetic mixture of metal oxides or with zinc oxide in combination with trace elements, levels of adsorption and citric acid production were observed to be similar to those in experiments where industrial filter dust was used. The two most important properties of the filter dust were its heavy-metal content and its buffering capacity. These properties were simulated by adding heavy metals in soluble form (as chlorides, sulfates, or nitrates) or soluble buffers to the medium. Both heavy metals and buffers were not able to induce a citric acid efflux. As with citric acid production by
Aspergillus niger
, the addition of manganese lowered citric acid excretion (by 40% with metal oxide-induced citric acid efflux and by 100% with urea-induced citric acid efflux). Copper antagonized the effect of manganese. The mechanism for the bulk of citric acid excretion by
P. simplicissimum
, however, seemed to be different from that described for citric acid accumulation by
A. niger
. Because of the inefficiency of metals in solubilized form and of soluble buffers to induce a strong citric acid efflux, adsorption of an insoluble metal compound (zinc oxide) turned out to be essential. Surface phenomena possibly involving the plasma membrane H
+
-ATPase are thought to participate in the induction of citric acid excretion by
P. simplicissimum
in the presence of industrial filter dust.
Molecular characterization of the nisin resistance region of Lactococcus lactis subsp. lactis biovar diacetylactis DRC3
Authors: Froseth B R , McKay L L
Published: January 2020

The nisin resistance determinant of Lactococcus lactis subsp. lactis biovar diacetylactis DRC3 was localized onto a 1.3-kb EcoRI-NdeI fragment by subcloning and interrupting the NdeI site by cloning random NdeI fragments into it; the nisin resistance determinant was then sequenced. The nucleotide sequence revealed a large open reading frame containing 318 codons. Putative transcription and translation signal sequences were located directly upstream from the initiation codon. Immediately downstream of the termination codon was a palindromic region resembling a rho-independent termination sequence. This 957-nucleotide open reading frame and its associated transcription and translation signal sequences were cloned into plasmid-free L. lactis subsp. lactis LM0230 and conferred an MIC of 160 IU of nisin per ml. This level of nisin resistance is equivalent to that of the initial nisin-resistant subclone, pFM011, used for further subcloning in this study. The inferred amino acid sequence would result in a protein with a molecular mass of 35,035 Da. This value was in agreement with the molecular mass of a protein detected after in vitro transcription and translation of DNA encoding the nisin resistance gene, nsr. This protein contained a hydrophobic region at the N terminus that was predicted to be membrane associated but did not contain a typical signal sequence cleavage site. No significant homology was detected when the DNA sequence of the nsr gene and the amino acid sequence of its putative product were compared with other available sequences. When subjected to Southern hybridization, a 1.2-kb DraI fragment encoding the nsr gene did not hybridize with the genomic DNA of the nisin-producing strain L. lactis subsp. lactis 11454.
Rapid and sensitive sandwich enzyme-linked immunosorbent assay for detection of staphylococcal enterotoxin B in cheese
Authors: Morissette C , Goulet J , Lamoureux G
Published: January 2020

A rapid and sensitive screening sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of staphylococcal enterotoxin B (SEB) in cheese by using a highly avid anti-SEB antibody (Ab) as the capture Ab (CAb) and as the biotinylated Ab conjugate. The glutaraldehyde fixation method for the immobilization of CAb on polystyrene dipsticks was superior to the adsorption fixation and the adsorption-glutaraldehyde fixation methods. The glutaraldehyde fixation method resulted in a higher surface-saturating CAb concentration as evaluated by the peroxidase saturation technique and by the ability of the CAb-coated dipstick to discriminate between positive and negative controls (index of discrimination). Of nine blocking agents used alone or in pairs, lysine-human serum albumin, bovine serum albumin, human serum albumin, and gelatin effectively saturated available sites on the CAb-coated dipsticks without causing interference with the antigen-Ab reactions. The addition of 1% polyethylene glycol to the diluent of the biotinylated anti-SEB Ab conjugate improved the detection of SEB. A concentration of 4% polyethylene glycol allowed a 5-min reaction time for the streptavidin-biotin-horseradish peroxidase conjugate. Cheddar cheese homogenate reduced the sensitivity of the SEB assay; however, the sensitivity was restored when 1.6% (wt/vol) of either a nonionic detergent (Mega-9) or two zwitterionic detergents (Zwittergent 3-10 and 3-12 detergent) was added to the diluent. By using the rapid sandwich ELISA, a minimum of 0.5 to 1.0 ng of SEB per ml was detected within 45 min. The whole procedure for the analysis of the cheddar cheese samples was completed within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Electron Transport in the Dissimilatory Iron Reducer, GS-15
Authors: Gorby Yuri A. , Lovley Derek R.
Published: January 2020

Mechanisms for electron transport to Fe(III) were investigated in GS-15, a novel anaerobic microorganism which can obtain energy for growth by coupling the complete oxidation of organic acids or aromatic compounds to the reduction of Fe(III) to Fe(II). The results indicate that Fe(III) reduction proceeds through a type
b
cytochrome and a membrane-bound Fe(III) reductase which is distinct from the nitrate reductase.
Aerial Nodules in
Casuarina cunninghamiana
Authors: Prin Y. , Duhoux E. , Diem H. G. , Roederer Y. , Dommergues Y. R.
Published: January 2020

A complete survey of La Réunion Island showed that, in 40- to 50-year-old
Casuarina cunninghamiana
plantations located in the northeast at an altitude above 400 m, some trees bore aerial nodules as high as 6 to 7 m up the trunk. The nodules exhibited a significant specific acetylene reduction by the ARA method (0.77 μmol of C
2
H
4
per h/g [dry weight] of nodule) at the time of sampling (June 1990). Aerial nodules were also found on a
Casuarina glauca
trunk. Preliminary observations show that anatomically aerial and underground nodules do not differ significantly. In addition to host plant genetic determinants, aerial nodule formation is assumed to require sufficient rainfall, an abundance of
Frankia
spp. in the soil and air, and rhytidome on the tree trunk.
Viable but nonculturable bacteria in drinking water
Authors: Byrd J J , Xu H S , Colwell R R
Published: January 2020

Klebsiella pneumoniae, Enterobacter aerogenes, Agrobacterium tumefaciens, Streptococcus faecalis, Micrococcus flavus, Bacillus subtilis, and Pseudomonas strains L2 and 719 were tested for the ability to grow and maintain viability in drinking water. Microcosms were employed in the study to monitor growth and survival by plate counts, acridine orange direct counts (AODC), and direct viable counts (DVC). Plate counts dropped below the detection limit within 7 days for all strains except those of Bacillus and Pseudomonas. In all cases, the AODC did not change. The DVC also did not change except that the DVC, on average, were ca. 10-fold lower than the AODC.
Improved procedure for bacteriophage typing of Listeria strains and evaluation of new phages
Authors: Loessner M J
Published: January 2020

A modified technique in listerial phage typing, termed reversed phage typing procedure, was developed. Ready-to-use typing plates were prepared by preapplication of phage suspensions on tryptose agar plates. The new procedure offers a number of substantial advantages as compared with the conventional method, being much more reliable, efficient, and convenient to use. More than 1,000 strains of Listeria have thus far been typed with the reversed phage typing procedure, employing an extended set of 21 genus-specific bacteriophages. The overall typability of strains was 89.5%.
Toxic shock syndrome toxin 1 (TSST-1) production by staphylococci isolated from goats and presence of specific antibodies to TSST-1 in serum and milk
Authors: Valle J , Vadillo S , Piriz S , Gomez-Lucia E
Published: January 2020

The ability of staphylococcal strains isolated from different anatomical sites in 133 healthy goats to produce toxic shock syndrome toxin 1 (TSST-1) and the presence of antibodies to this toxin in serum and milk were studied. The enzyme-linked immunosorbent assay method was used to detect both the toxin and the presence of antibodies. Of a total of 342 staphylococcal strains studied, 86 (25.2%) were found to produce TSST-1. Specific antibodies to TSST-1 were found in the serum of 57 (42.9%) of the animals studied and the milk of 63 (47.4%) of the animals. These results suggest that goats are frequently in contact with staphylococci that produce TSST-1, a toxin usually associated with Staphylococcus aureus strains isolated from cases of toxic shock syndrome in humans.
Trophic relationships between Saccharomyces cerevisiae and Lactobacillus plantarum and their metabolism of glucose and citrate
Authors: Kennes C , Veiga M C , Dubourguier H C , Touzel J P , Albagnac G , Naveau H , Nyns E J
Published: January 2020

Glucose and citrate are two major carbon sources in fruits or fruit juices such as orange juice. Their metabolism and the microorganisms involved in their degradation were studied by inoculating with an aliquot of fermented orange juice a synthetic model medium containing glucose and citrate. At pH 3.6, their degradation led, first, to the formation of ethanol due to the activity of yeasts fermenting glucose and, eventually, to the formation of acetate resulting from the activity of lactobacilli. The yeast population always outcompeted the lactobacilli even when the fermented orange juice used as inoculum was mixed with fermented beet leaves containing a wider variety of lactic acid bacteria. The evolution of the medium remained similar between pH 3.3 and 5.0. At pH 3.0 or below, the fermentation of citrate was totally inhibited. Saccharomyces cerevisiae and Lactobacillus plantarum were identified as the only dominant microorganisms. The evolution of the model medium with the complex microbial community was successfully reconstituted with a defined coculture of S. cerevisiae and L. plantarum. The study of the fermentation of the defined model medium with a reconstituted microbial community allows us to better understand the behavior not only of fermented orange juice but also of many other fruit fermentations utilized for the production of alcoholic beverages.
Kinetics of Iron Oxidation by
Thiobacillus ferrooxidans
Authors: Okereke Amechi , Stevens S. Edward
Published: January 2020

A statistical relationship between the rate of ferric ion production by a strain of
Thiobacillus ferrooxidans
and various levels of cell concentration, Fe
2+
concentration, Na
+
concentration, and temperature was studied by a direct colorimetric method at 304 nm. The relationship was linear (90 to 93%), cross-product (3 to 4%), and quadratic (1 to 2%). The levels of cell concentration and Fe
2+
concentration and their respective interactions with one another and the other factors had the most significant effects on the regression models. The solution of the quadratic response surface for optimum oxidation was a saddle point, and the predicted critical levels of temperature, cell concentration, Fe
2+
concentration, and Na
+
concentration ranged between −6 and 2°C, 0.43 and 0.62 mg/ml, 72 and 233 mM, and 29.6 mM, respectively.
Adsorption of plasmid DNA to mineral surfaces and protection against DNase I
Authors: Romanowski G , Lorenz M G , Wackernagel W
Published: January 2020

The adsorption of [3H]thymidine-labeled plasmid DNA (pHC314; 2.4 kb) of different conformations to chemically pure sand was studied in a flowthrough microenvironment. The extent of adsorption was affected by the concentration and valency of cations, indicating a charge-dependent process. Bivalent cations (Mg2+, Ca2+) were 100-fold more effective than monovalent cations (Na+, K+, NH4+). Quantitative adsorption of up to 1 microgram of negatively supercoiled or linearized plasmid DNA to 0.7 g of sand was observed in the presence of 5 mM MgCl2 at pH 7. Under these conditions, more than 85% of DNA adsorbed within 60 s. Maximum adsorption was 4 micrograms of DNA to 0.7 g of sand. Supercoil molecules adsorbed slightly less than linearized or open circular plasmids. An increase of the pH from 5 to 9 decreased adsorption at 0.5 mM MgCl2 about eightfold. It is concluded that adsorption of plasmid DNA to sand depends on the neutralization of negative charges on the DNA molecules and the mineral surfaces by cations. The results are discussed on the grounds of the polyelectrolyte adsorption model. Sand-adsorbed DNA was 100 times more resistant against DNase I than was DNA free in solution. The data support the idea that plasmid DNA can enter the extracellular bacterial gene pool which is located at mineral surfaces in natural bacterial habitats.
Survey of fumonisin production by Fusarium species
Authors: Thiel P G , Marasas W F , Sydenham E W , Shephard G S , Gelderblom W C , Nieuwenhuis J J
Published: January 2020

Fumonisins B1 (FB1) and B2 (FB2), two structurally related mycotoxins with cancer-promoting activity, were recently isolated from corn cultures of Fusarium moniliforme MRC 826. These toxins have been reported to be produced also by isolates of F. proliferatum. Contamination of foods and feeds by F. moniliforme has been associated with human esophageal cancer risk, and FB1 has been shown to be the causative agent of the neurotoxic disease leukoencephalomalacia in horses. Because of the toxicological importance of the fumonisins, the potential to produce FB1 and FB2 was determined in a study of 40 toxic Fusarium isolates representing 27 taxa in 9 of the 12 sections of Fusarium, as well as two recently described species not yet classified into sections. With the exception of one isolate of F. nygamai, fumonisin production was restricted to isolates of F. moniliforme and F. proliferatum, in the section Liseola. The F. nygamai isolate produced 605 micrograms of FB1 g-1 and 530 micrograms of FB2 g-1, and the identity of the toxins was confirmed by capillary gas chromatography-mass spectrometry. This is the first report of the production of the fumonisins by F. nygamai.
Distribution of actinomycetes in near-shore tropical marine sediments
Authors: Jensen P R , Dwight R , Fenical W
Published: January 2020

Actinomycetes were isolated from near-shore marine sediments collected at 15 island locations throughout the Bahamas. A total of 289 actinomycete colonies were observed, and all but 6 could be assigned to the suprageneric groups actinoplanetes and streptomycetes. A bimodal distribution in the actinomycete population in relation to depth was recorded, with the maximum numbers occurring in the shallow and deep sampling sites. This distribution can be accounted for by a rapid decrease in streptomycetes and an increase in actinoplanetes with increasing depth and does not conform to the theory that actinomycetes isolated from marine sources are of terrestrial origin. Sixty-three of the isolated actinomycetes were tested for the effects of seawater on growth. Streptomycete growth in nonsaline media was reduced by 39% compared with that in seawater. The actinoplanetes had a near obligate requirement of seawater for growth, and this is presented as evidence that actinomycetes can be physiologically active in the marine environment. Problems encountered with the enumeration of actinomycetes in marine sediments are also discussed.
Effect of organic N-halamines on selected membrane functions in intact Staphylococcus aureus cells
Authors: Williams D E , Swango L J , Wilt G R , Worley S D
Published: January 2020

Two N-halamine compounds, 3-chloro-4,4-dimethyl-2-oxazolidinone and 1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone, were compared with free chlorine as to their effects on selected membrane functions of intact Staphylococcus aureus cells. Free chlorine was found to cause a loss of permeability control, as measured by the efflux of potassium from the cells and a dramatic increase in hydrogen ion permeability, and to affect cell respiration in a nonreversible fashion, as measured by oxygen uptake. The two N-halamines were found to have very little effect on permeability to either potassium or hydrogen ions but were both found to dramatically inhibit respiration in a reversible manner. It is proposed that the first step in the disinfection process by these N-halamines is an inhibition of respiratory enzymes that, if not reversed, ultimately leads to a loss of cell viability.