bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular cloning and mapping of phenol degradation genes from Bacillus stearothermophilus FDTP-3 and their expression in Escherichia coli
Authors: Dong F M , Wang L L , Wang C M , Cheng J P , He Z Q , Sheng Z J , Shen R Q
Published: January 2020

Two genes of the meta pathway of phenol degradation were cloned from a phenol-utilizing strain of Bacillus stearothermophilus and were mapped by subcloning and by use of a Tn5 insertion mutation. They code for phenol hydroxylase and catechol 2,3-dioxygenase, respectively. The gene encoding catechol 2,3-dioxygenase, which is more thermostable than catechol 2,3-dioxygenase encoded by the other gene, shares rather limited homology with that from Pseudomonas putida.
Novel mutations in the pheA gene of Escherichia coli K-12 which result in highly feedback inhibition-resistant variants of chorismate mutase/prephenate dehydratase
Authors: Nelms J , Edwards R M , Warwick J , Fotheringham I
Published: January 2020

The bifunctional enzyme chorismate mutase/prephenate dehydratase (EC 5.4.99.5/4.2.1.51), which is encoded by the pheA gene of Escherichia coli K-12, is subject to strong feedback inhibition by L-phenylalanine. Inhibition of the prephenate dehydratase activity is almost complete at concentrations of L-phenylalanine greater than 1 mM. The pheA gene was cloned, and the promoter region was modified to enable constitutive expression of the gene on plasmid pJN302. As a preliminary to sequence analysis, a small DNA insertion at codon 338 of the pheA gene unexpectedly resulted in a partial loss of prephenate dehydratase feedback inhibition. Four other mutations in the pheA gene were identified following nitrous acid treatment of pJN302 and selection of E. coli transformants that were resistant to the toxic phenylalanine analog beta-2-thienylalanine. Each of the four mutations was located within codons 304 to 310 of the pheA gene and generated either a substitution or an in-frame deletion. The mutations led to activation of both enzymatic activities at low phenylalanine concentrations, and three of the resulting enzyme variants displayed almost complete resistance to feedback inhibition of prephenate dehydratase by phenylalanine concentrations up to 200 mM. In all four cases the mutations mapped in a region of the enzyme that has not been implicated previously in feedback inhibition sensitivity of the enzyme.
The homologous and heterologous regions within the iap gene allow genus- and species-specific identification of Listeria spp. by polymerase chain reaction
Authors: Bubert A , Köhler S , Goebel W
Published: January 2020

The iap gene of Listeria species encodes protein p60. The comparison of iap-related genes from different Listeria species indicated common and variable regions within these genes which appeared to be specific for each Listeria species. On the basis of the iap gene sequences, pairs of polymerase chain reaction (PCR) primers which allowed the unambiguous identification of all members of the genus Listeria, of groups of related Listeria species, and of L. monocytogenes, exclusively, were selected. The PCR primers specific for L. monocytogenes yielded PCR products which represented essentially the repeat region of the iap gene. The size of these PCR products allowed an estimate of the number of the TN repeat units within the repeat region of the p60 protein of an L. monocytogenes strain. The data indicated that the number of repeat units differed among L. monocytogenes isolates.
Cloning, nucleotide sequences, and overexpression in Escherichia coli of tandem copies of a tryptophanase gene in an obligately symbiotic thermophile, Symbiobacterium thermophilum
Authors: Hirahara T , Suzuki S , Horinouchi S , Beppu T
Published: January 2020

Symbiobacterium thermophilum, a thermophilic bacterium, is a thermostable tryptophanase producer that can grow only in coculture with a specific Bacillus strain. Two thermostable tryptophanase genes, tna-1 and tna-2, that are located close to each other were cloned into Escherichia coli from S. thermophilum by the DNA-probing method. The nucleotide and deduced amino acid sequences indicate that Tna1 and Tna2 share 92% identical amino acids in a total of 453 amino acids. By means of DNA manipulation with E. coli host-vector systems, Tna1 and Tna2 were produced in very large amounts in enzymatically active forms. Comparison of the NH2-terminal amino acid sequences and the enzymatic properties of the tryptophanases purified from the original S. thermophilum strain and these two tryptophanases from recombinant E. coli cells suggest that in S. thermophilum, only Tna2 is produced and tna-1 is silent. Notwithstanding the great similarity in amino acid sequence between Tna1 and Tna2, the two enzymes differ markedly in activation energy for catalysis and thermostability.
Oxidation of nitrotoluenes by toluene dioxygenase: evidence for a monooxygenase reaction
Authors: Robertson J B , Spain J C , Haddock J D , Gibson D T
Published: January 2020

Pseudomonas putida F1 and Pseudomonas sp. strain JS150 initiate toluene degradation by incorporating molecular oxygen into the aromatic nucleus to form cis-1,2-dihydroxy-3-methylcyclohexa-3,5-diene. When toluene-grown cells were incubated with 2- and 3-nitrotoluene, the major products identified were 2- and 3-nitrobenzyl alcohol, respectively. The same cells oxidized 4-nitrotoluene to 2-methyl-5-nitrophenol and 3-methyl-6-nitrocatechol. Escherichia coli JM109(pDTG601), which contains the toluene dioxygenase genes from P. putida F1 under the control of the tac promoter, oxidized the isomeric nitrotoluenes to the same metabolites as those formed by P. putida F1 and Pseudomonas sp. strain JS150. These results extend the range of substrates known to be oxidized by this versatile enzyme and demonstrate for the first time that toluene dioxygenase can oxidize an aromatic methyl substituent.
Complete mineralization of benzene by aquifer microorganisms under strictly anaerobic conditions
Authors: Edwards E A , Grbić-Galić D
Published: January 2020

Benzene was mineralized to CO2 by aquifer-derived microorganisms under strictly anaerobic conditions. The degradation occurred in microcosms containing gasoline-contaminated subsurface sediment from Seal Beach, California, and anaerobic, sulfide-reduced defined mineral medium supplemented with 20 mM sulfate. Benzene, at initial concentrations ranging from 40 to 200 microM, was depleted in all microcosms and more than 90% of 14C-labeled benzene was mineralized to 14CO2.
Development of the immunomagnetic enrichment method selective for Vibrio parahaemolyticus serotype K and its application to food poisoning study
Authors: Tomoyasu T
Published: January 2020

A method using immunomagnetic separation was developed to isolate the specified K serotype of Vibrio parahaemolyticus from a mixture of a large number of bacteria with other K serotypes. This method was applied to food poisoning studies and could recover the V. parahaemolyticus serotype found in the patient from the incriminated foods.
Plasmid Heterogeneity in Spanish Isolates of
Agrobacterium tumefaciens
from Thirteen Different Hosts
Authors: Albiach Maria R. , Lopez Maria M.
Published: January 2020

Plasmid DNA was isolated from 80 Spanish isolates of
Agrobacterium tumefaciens
from 13 hosts of several geographical and temporal origins. One to five plasmids occurred in all of the isolates studied. Plasmid sizes varied between 5 and greater than 1,000 MDa. Generally, there was no correlation between plasmid number or size and geographical origin, host, biovar, sensitivity to agrocin 84, or opine-catabolizing ability of the different isolates.
Topical Application of Ice-Nucleating-Active Bacteria Decreases Insect Cold Tolerance
Authors: Strong-Gunderson Janet M. , Lee Richard E. , Lee Marcia R.
Published: January 2020

The majority of overwintering insects avoid lethal freezing by lowering the temperature at which ice spontaneously nucleates within their body fluids. We examined the effect of ice-nucleating-active bacteria on the cold-hardiness of the lady beetle,
Hippodamia convergens
, a freeze-intolerant species that overwinters by supercooling to ca. −16°C. Topical application of the ice-nucleating-active bacteria
Pseudomonas syringae
increased the supercooling point to temperatures as high as −3°C. This decrease in cold tolerance was maintained for at least 3 days after treatment. Various treatment doses (10
8
, 10
6
, and 10
4
bacteria per ml) and modes of action (bacterial ingestion and topical application) were also compared. At the highest concentration of topically applied
P. syringae
, 50% of the beetles froze between −2 and −4°C. After topical application at the lowest concentration, 50% of the individuals froze by −11°C. In contrast, beetles fed bacteria at this concentration did not begin to freeze until −10°C, and 50% were frozen only at temperatures of −13°C or less. In addition to reducing the supercooling capacity in
H. convergens
, ice-nucleating-active bacteria also significantly reduced the cold-hardiness of four additional insects. These data demonstrate that ice-nucleating-active bacteria can be used to elevate the supercooling point and thereby decrease insect cold tolerance. The results of this study support the proposition that ice-nucleating-active bacteria may be used as a biological insecticide for the control of insect pests during the winter.
Metabolism of toxic pyrrolizidine alkaloids from tansy ragwort (Senecio jacobaea) in ovine ruminal fluid under anaerobic conditions
Authors: Craig A M , Latham C J , Blythe L L , Schmotzer W B , O'Connor O A
Published: January 2020

The ability of ovine ruminal fluid to metabolize pyrrolizidine alkaloid (PA) from Senecio jacobaea under anaerobic conditions was evaluated. Four fistulated sheep fed PA served as individual sources of ruminal fluid, which was incubated in a defined minimal salts medium under two different anaerobic conditions, denitrifying and methanogenic. Anaerobic cultures amended with ovine ruminal fluids (20%), PA (100 micrograms/ml), and a defined minimal salts medium were monitored for a period of several days. These cultures revealed that while PA was not depleted in sterile, autoclaved controls or under denitrifying conditions, it was metabolized during periods of active methanogenesis under methanogenic conditions. In addition, samples of ruminal fluid were separated by differential centrifugation under anaerobic conditions, and the resultant supernatants were tested for their ability to metabolize PA as compared with those of the respective uncentrifuged control fluids. Uncentrifuged controls exhibited a PA depletion rate of -4.04 +/- 0.17 micrograms of PA per ml per h. Supernatants 1 (centrifuged at 41 x g for 2 min), 2 (centrifuged at 166 x g for 5 min), and 3 (centrifuged at 1,500 x g for 10 min) exhibited significantly slower depletion rates, with slopes of data representing -1.64 +/- 0.16, -1.44 +/- 0.16, and -1.48 +/- 0.16 micrograms of PA metabolized per ml per h, respectively, demonstrating no statistically significant difference among the supernatant cultures. Microscopic evaluations revealed that protozoa were present in the control whole ruminal fluid and to a lesser extent in supernatant 1, while supernatants 2 and 3 contained only bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)
Examination of Bacterial Characteristics of Anaerobic Membrane Bioreactors in Three Pilot-Scale Plants for Treating Low-Strength Wastewater by Application of the Colony-Forming-Curve Analysis Method
Authors: Kataoka Naoaki , Tokiwa Yutaka , Tanaka Yasuo , Fujiki Kiichi , Taroda Hiroyuki , Takeda Kiyoshi
Published: January 2020

Characteristic sludge ecosystems arising in anaerobic membrane bioreactors of three pilot-scale plants treating low-strength (less than 1 g of biological oxygen demand per liter) sewage or soybean-processing wastewater were examined by analysis of the colony-forming-curves (CFC) obtained by counting colonies at suitable intervals. The wastewaters, containing high amounts of suspended solids (SS) (SS/chemical oxygen demand ratio, 0.51 to 0.80), were treated by using two types of bioreactors: (i) a hydrolyzation reactor for solubilization and acidification of SS in wastewater and (ii) a methane fermentation reactor for producing methane. The colony counts for the two sewage treatment plants continued to increase even after 3 weeks of incubation, whereas those for soybean-processing wastewater reached an approximately constant level within 3 weeks of incubation. The CFCs were analyzed by correlating the rate of colony appearance on roll tubes with the physiological types of bacteria present in the bioreactors. It was found that there were large numbers of slow-colony-forming anaerobic bacteria within the bioreactors and that the viable populations consisted of a few groups with different growth rates. It is considered that the slow-growing colonies appearing after 10 days of incubation were the dominant microflora in the sewage treated by hydrolyzation reactors. In particular, highly concentrated sludge (30.0 g of mixed-liquor volatile SS per liter) retained by the membrane separation module contained a large number of such bacteria. Slow-growing colonies of these bacteria could be counted by using a sludge extract medium prepared from only the supernatant of autoclaved sludge. In addition, the highest colony counts were almost always obtained with the sludge extract medium, meaning that most of the anaerobic bacteria in these sludges have complex nutrient requirements for growth. This report also indicates the usefulness of application of the CFC analysis method to the study of bacterial populations of anaerobic treatment systems.
Effects of Temperature on Methane Consumption in a Forest Soil and in Pure Cultures of the Methanotroph
Methylomonas rubra
Authors: King G. M. , Adamsen A. P. S.
Published: January 2020

Methane oxidation in soil cores from a mixed hardwood-coniferous forest varied relatively little as a function of incubation temperatures from −1 to 30°C. The increase in oxidation rate was proportional to
T
2.4
(in kelvins). This relationship was consistent with limitation of methane transport through a soil gas phase to a subsurface zone of consumption by diffusion. The Q
10
for CO
2
production, 3.4, was substantially higher than that for methane oxidation, 1.1, and indicated that the response of soil respiration to temperature was limited by enzymatic processes and not diffusion of either organic substrates or molecular oxygen. When grown under conditions of phase-transfer limitation, cultures of
Methylomonas rubra
showed a minimal response to temperature changes between 19 and 38°C, as indicated by methane oxidation rates; in the absence of phase-transfer limitations,
M. rubra
oxidized methane at rates strongly dependent on temperature.
Effects of temperature abuse on survival of Vibrio vulnificus in oysters
Authors: Murphy S K , Oliver J D
Published: January 2020

Opaque and translucent morphotypes of a TnphoA-containing strain of Vibrio vulnificus were fed to oysters, which were subsequently stored at temperatures ranging from 0.5 to 22 degrees C for 10 days. Samples of oysters were homogenized and plated at intervals to determine the cell density of V. vulnificus and total aerobic population of bacteria present. At all temperatures, the numbers of V. vulnificus (both morphotypes) declined over the 10-day study period. The same observation was made with a lower inoculum of V. vulnificus. Identical experiments with shucked oysters showed a more rapid decrease in V. vulnificus. Identical experiments with shucked oysters showed a more rapid decrease in V. vulnificus to levels below limits of detection. Little change in the total bacterial counts was observed in shellstock oysters at any of the test temperatures, whereas incubation at the higher temperatures (17 and 22 degrees C) resulted in large increases in total counts in shucked oysters. These data suggest that temperature abuse of oysters may not be a factor in increasing the public health risk of V. vulnificus through raw oyster consumption. However, the data also suggest that even with proper storage, indigenous levels of V. vulnificus may remain sufficiently higher in shellstock oysters to produce infection in compromised hosts.
16S rRNA-based probes and polymerase chain reaction method to detect Listeria monocytogenes cells added to foods
Authors: Wang R F , Cao W W , Johnson M G
Published: January 2020

A rapid polymerase chain reaction (PCR) method was developed for detection of Listeria monocytogenes in foods. This method used a pair of primers based on a unique region in the 16S rRNA sequence of L. monocytogenes, which were previously reported by us to yield a specific nucleic acid probe. Our method included use of a shorter denaturing time, a shorter annealing time, a rapid transition, and an increase in the number of cycles, resulting in good sensitivity. Just 3 h for PCR plus 1 h for electrophoresis was required. Additional time for DNA isolation and DNA hybridization was not needed. This method detected as few as 2 to 20 CFU of L. monocytogenes in pure cultures and as few as 4 to 40 CFU of L. monocytogenes in inoculated (10(8) CFU), diluted food samples. Seven of eight foods, including four poultry products, gave positive results. Only one food sample, soft cheese, gave interference. An internal probe hybridization test was used to confirm that the PCR products were from L. monocytogenes. A specificity test indicated that this PCR method was positive for all 13 strains of L. monocytogenes tested but negative for the other 6 species of Listeria, including 6 strains of L. innocua, and negative for 17 other gram-positive and gram-negative bacteria tested.
Genetic relatedness of Bradyrhizobium japonicum field isolates as revealed by repeated sequences and various other characteristics
Authors: Minamisawa K , Seki T , Onodera S , Kubota M , Asami T
Published: January 2020

Forty-nine isolates of Bradyrhizobium japonicum indigenous to a field where soybeans were grown for 45 years without inoculation were characterized by using four DNA hybridization probes from B. japonicum. nifDK-specific hybridization clearly divided the isolates into two divergent groups. Diversity in repeated-sequence (RS)-specific hybridization was observed; 44 isolates derived from 41 nodules were divided into 33 different RS fingerprint groups. Cluster analysis showed that the RS fingerprints were correlated with the nif and hup genotypes. We found multiple bands of RS-specific hybridization for two isolates that differed from the patterns of the other isolates. These results suggest that RS fingerprinting is a valuable tool for evaluating the genetic structure of indigenous B. japonicum populations.
Formation of unilamellar liposomes from total polar lipid extracts of methanogens
Authors: Choquet C G , Patel G B , Beveridge T J , Sprott G D
Published: January 2020

Unilamellar liposomes were formed by controlled detergent dialysis of mixed micelles consisting of acetone-insoluble total polar lipids extracted from various methanogens and the detergent n-octyl-beta-D-glucopyranoside. The final liposome populations were studied by dynamic light scattering and electron microscopy. Unilamellar liposomes with mean diameters smaller than 100 nm were obtained with lipid extracts of Methanococcus voltae, Methanosarcina mazei, Methanosaeta concilii, and Methanococcus jannaschii (grown at 50 degrees C), whereas larger (greater than 100-nm) unilamellar liposomes were obtained with lipid extracts of M. jannaschii grown at 65 degrees C. These liposomes were shown to be closed intact vesicles capable of retaining entrapped [14C]sucrose for extended periods of time. With the exception of Methanospirillum hungatei liposomes, all size distributions of the different liposome populations were fairly homogeneous.
Dynamic mathematical model to predict microbial growth and inactivation during food processing
Authors: Van Impe J F , Nicolaï B M , Martens T , De Baerdemaeker J , Vandewalle J
Published: January 2020

Many sigmoidal functions to describe a bacterial growth curve as an explicit function of time have been reported in the literature. Furthermore, several expressions have been proposed to model the influence of temperature on the main characteristics of this growth curve: maximum specific growth rate, lag time, and asymptotic level. However, as the predictive value of such explicit models is most often guaranteed only at a constant temperature within the temperature range of microbial growth, they are less appropriate in optimization studies of a whole production and distribution chain. In this paper a dynamic mathematical model--a first-order differential equation--has been derived, describing the bacterial population as a function of both time and temperature. Furthermore, the inactivation of the population at temperatures above the maximum temperature for growth has been incorporated. In the special case of a constant temperature, the solution coincides exactly with the corresponding Gompertz model, which has been validated in several recent reports. However, the main advantage of this dynamic model is its ability to deal with time-varying temperatures, over the whole temperature range of growth and inactivation. As such, it is an essential building block in (time-saving) simulation studies to design, e.g., optimal temperature-time profiles with respect to microbial safety of a production and distribution chain of chilled foods.
Physiological studies of chloramine resistance developed by Klebsiella pneumoniae under low-nutrient growth conditions
Authors: Stewart M H , Olson B H
Published: January 2020

This study investigated the physiological mechanisms of resistance to chloramines developed by Klebsiella pneumoniae grown in a nutrient-limited environment. Growth under these conditions resulted in cells that were smaller than cells grown under high-nutrient conditions and extensively aggregated. Cellular aggregates ranged from 10 to more than 10,000 cells per aggregate, with a mean population aggregate size of 90 cells. This aggregation may have been facilitated by the presence of extracellular polymer material. By using glucose as a reference of capsule content, it was determined that growth under low-nutrient conditions produced cells with 8 x 10(-14) to 41 x 10(-14) g of carbohydrate per cell, with a mean +/- standard deviation of 27 x 10(-14) +/- 16 x 10(-14) g of carbohydrate per cell. In comparison, growth under high-nutrient conditions resulted in 2.7 x 10(-14) to 5.9 x 10(-14) g of carbohydrate per cell, with a mean and standard deviation of 4.3 x 10(-14) +/- 1.2 x 10(-14) g of carbohydrate per cell. Cell wall and cell membrane lipids also varied with growth conditions. The ratio of saturated to unsaturated fatty acids in cells grown under low-nutrient conditions was approximately five times greater than that in cells grown under high-nutrient conditions, suggesting possible differences in membrane permeability. An analysis of sulfhydryl (-SH) groups revealed no quantitative difference with respect to growth conditions. However, upon exposure to chloramines, only 33% of the -SH groups of cells grown under low-nutrient conditions were oxidized, compared with 80% oxidization of -SH groups in cells grown under high-nutrient conditions. The reduced effectiveness of chloramine oxidization of -SH groups in cells grown under low-nutrient conditions may be due to restricted penetration of chloramines into the cells, conformational changes of enzymes, or a combination of both factors. The results of this study suggest that chloramine resistance developed under low-nutrient growth conditions may be a function of multiple physiological factors, including cellular aggregation and protection of sulfhydryl groups within the cell.
Biochemical Composition of Dissolved Organic Carbon Derived from Phytoplankton and Used by Heterotrophic Bacteria
Authors: Sundh Ingvar
Published: January 2020

The molecular size distribution and biochemical composition of the dissolved organic carbon released from natural communities of lake phytoplankton (photosynthetically produced dissolved organic carbon [PDOC]) and subsequently used by heterotrophic bacteria were determined in three lakes differing in trophic status and concentration of humic substances. After incubation of epilimnetic lake water samples with H
14
CO
3
-
over one diel cycle, the phytoplankton were removed by size-selective filtration. The filtrates, still containing most of the heterotrophic bacteria, were reincubated in darkness (heterotrophic incubation). Differences in the amount and composition of PDO
14
C between samples collected before the heterotrophic incubation and samples collected afterwards were considered to be a result of bacterial utilization. The PDO
14
C collected at the start of the heterotrophic incubations always contained both high (>10,000)- and low (<1,000)-molecular-weight (MW) components and sometimes contained intermediate-MW components as well. In general, bacterial turnover rates of the low-MW components were fairly rapid, whereas the high-MW components were utilized slowly or not at all. In the humic lake, the intermediate-MW components accounted for a large proportion of the net PDO
14
C and were subject to rapid bacterial utilization. This fraction probably consisted almost entirely of polysaccharides of ca. 6,000 MW. Amino acids and peptides, other organic acids, and carbohydrates could all be quantitatively important parts of the low-MW PDO
14
C that was utilized by the heterotrophic bacteria, but the relative contributions of these fractions differed widely. It was concluded that, generally, low-MW components of PDOC are quantitatively much more important to the bacteria than are high-MW components, that PDOC released from phytoplankton does not contain substances of quantitative importance as bacterial substrates in all situations, and that high-MW components of PDOC probably contribute to the buildup of refractory, high-MW dissolved organic carbon in pelagic environments.
Ice Nucleation Activity in
Fusarium acuminatum
and
Fusarium avenaceum
Authors: Pouleur Stéphan , Richard Claude , Martin Jean-Guy , Antoun Hani
Published: January 2020

Twenty fungal genera, including 14
Fusarium
species, were examined for ice nucleation activity at −5.0°C, and this activity was found only in
Fusarium acuminatum
and
Fusarium avenaceum
. This characteristic is unique to these two species. Ice nucleation activity of
F. avenaceum
was compared with ice nucleation activity of a
Pseudomonas
sp. strain. Cumulative nucleus spectra are similar for both microorganisms, while the maximum temperatures of ice nucleation were −2.5°C for
F. avenaceum
and −1.0°C for the bacteria. Ice nucleation activity of
F. avenaceum
was stable at pH levels from 1 to 13 and tolerated temperature treatments up to 60°C, suggesting that these ice nuclei are more similar to lichen ice nuclei than to bacterial ones. Ice nuclei of
F. avenaceum
, unlike bacterial ice nuclei, pass through a 0.22-μm-pore-size filter. Fusarial nuclei share some characteristics with the so-called leaf-derived nuclei with which they might be identified: they are cell free and stable up to 60°C, and they are found in the same kinds of environment. Highly stable ice nuclei produced by fast-growing microorganisms have potential applications in biotechnology. This is the first report of ice nucleation activity in free-living fungi.
Effect of pseudobactin 358 production by Pseudomonas putida WCS358 on suppression of fusarium wilt of carnations by nonpathogenic Fusarium oxysporum Fo47
Authors: Lemanceau P , Bakker P A , De Kogel W J , Alabouvette C , Schippers B
Published: January 2020

Nonpathogenic Fusarium oxysporum Fo47b10 combined with Pseudomonas putida WCS358 efficiently suppressed fusarium wilt of carnations grown in soilless culture. This suppression was significantly higher than that obtained by inoculation of either antagonistic microorganism alone. The increased suppression obtained by Fo47b10 combined with WCS358 only occurred when Fo47b10 was introduced at a density high enough (at least 10 times higher than that of the pathogen) to be efficient on its own. P. putida WCS358 had no effect on disease severity when inoculated on its own but significantly improved the control achieved with nonpathogenic F. oxysporum Fo47b10. In contrast, a siderophore-negative mutant of WCS358 had no effect on disease severity even in the presence of Fo47b10. Since the densities of both bacterial strains at the root level were similar, the difference between the wild-type WCS358 and the siderophore-negative mutant with regard to the control of fusarium wilt was related to the production of pseudobactin 358. The production of pseudobactin 358 appeared to be responsible for the increased suppression by Fo47b10 combined with WCS358 relative to that with Fo47b10 alone.
Evaluation of Methyl Fluoride and Dimethyl Ether as Inhibitors of Aerobic Methane Oxidation
Authors: Oremland Ronald S. , Culbertson Charles W.
Published: January 2020

Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH
4
as well as the oxidation of
14
CH
4
to
14
CO
2
, but neither MF nor DME affected the oxidation of [
14
C]methanol or [
14
C]formate to
14
CO
2
. Cooxidation of ethane and propane by methane-oxidizing soils was also inhibited by MF. Nitrification (ammonia oxidation) in soils was inhibited by both MF and DME. Production of N
2
O via nitrification was inhibited by MF; however, MF did not affect N
2
O production associated with denitrification. Methanogenesis was partially inhibited by MF but not by DME. Methane oxidation was ∼100-fold more sensitive to MF than was methanogenesis, indicating that an optimum concentration could be employed to selectively block methanotrophy. MF inhibited methane oxidation by cell suspensions of
Methylococcus capsulatus
; however, DME was a much less effective inhibitor.
Organophosphonate utilization by the wild-type strain of Pseudomonas fluorescens
Authors: Zboińska E , Lejczak B , Kafarski P
Published: January 2020

The wild-type strain of Pseudomonas fluorescens was found to utilize a range of structurally diverse organophosphonates as its sole carbon or nitrogen sources. Representative compounds included aminoalkylphosphonates, hydroxyalkylphosphonates, oxoalkylphosphonates, and phosphono dipeptides. Among them, amino(phenyl)methylphosphonate,2-aminoethylphosphonate, aminomethylphosphonate, diisopropyl 9-aminofluoren-9-ylphosphonate, and 2-oxoalkylphosphonates were used by P. fluorescens as its sole sources of phosphorus. Only slight growth was observed on the herbicide glyphosate (N-phosphonomethylglycine), which was metabolized to aminomethylphosphonate. Neither phosphinothricin nor its dialanyl tripeptide, bialaphos, supported growth of P. fluorescens. The possible mechanisms of organophosphonate degradation by this strain are discussed.
Importance of unattached bacteria and bacteria attached to sediment in determining potentials for degradation of xenobiotic organic contaminants in an aerobic aquifer
Authors: Holm P E , Nielsen P H , Albrechtsen H J , Christensen T H
Published: January 2020

The bacterial abundance, distribution, and degradation potential (in terms of degradation versus lack of degradation) for four xenobiotic compounds in an aerobic aquifer sediment have been examined in laboratory and field experiments. The xenobiotic compounds studied were benzene, toluene, o-xylene, and naphthalene (all at concentrations of approximately 120 micrograms/liter). The aerobic degradation experiments ran for approximately 90 days at 10 degrees C, which corresponded to the groundwater temperature. At the end of the experiment, the major part of the microbial biomass, quantified as acridine orange direct counts, was attached to the groundwater sediment (18 x 10(6) to 25 x 10(6) cells per g [dry weight], and only a minor part was unattached in the groundwater (0.6 x 10(6) to 5.5 x 10(6) cells per ml). Experiments involving aquifer sediment suspensions showed identical degradation potentials in the laboratory and in the field. However, laboratory experiments involving only groundwater (excluding aquifer sediment) showed less degradation potential than in situ experiments involving only groundwater, indicating that the manipulation or approach of the laboratory experiments could affect the determination of the degradation potentials. No differences were observed between the groundwater-only and the sediment compartments in the in situ experiments in the ability to degrade the compounds, but the maximum degradation rates were substantially lower in the groundwater-only compartment. Preparations used in laboratory experiments for studying the degradation potential for xenobiotic organic contaminants should contain sediment to obtain the highest numbers of bacteria as well as the broadest and most stable degradation.(ABSTRACT TRUNCATED AT 250 WORDS)
Cometabolic degradation of chlorinated alkenes by alkene monooxygenase in a propylene-grown Xanthobacter strain
Authors: Ensign S A , Hyman M R , Arp D J
Published: January 2020

Propylene-grown Xanthobacter cells (strain Py2) degraded several chlorinated alkenes of environmental concern, including trichloroethylene, 1-chloroethylene (vinyl chloride), cis- and trans-1,2-dichloroethylene, 1,3-dichloropropylene, and 2,3-dichloropropylene. 1,1-Dichloroethylene was not degraded efficiently, while tetrachloroethylene was not degraded. The role of alkene monooxygenase in catalyzing chlorinated alkene degradations was established by demonstrating that glucose-grown cells which lack alkene monooxygenase and propylene-grown cells in which alkene monooxygenase was selectively inactivated by propyne were unable to degrade the compounds. C2 and C3 chlorinated alkanes were not oxidized by alkene monooxygenase, but a number of these compounds were inhibitors of propylene and ethylene oxidation, suggesting that they compete for binding to the enzyme. A number of metabolites enhanced the rate of degradation of chlorinated alkenes, including propylene oxide, propionaldehyde, and glucose. Propylene stimulated chlorinated alkene oxidation slightly when present at a low concentration but became inhibitory at higher concentrations. Toxic effects associated with chlorinated alkene oxidations were determined by measuring the propylene oxidation and propylene oxide-dependent O2 uptake rates of cells previously incubated with chlorinated alkenes. Compounds which were substrates for alkene monooxygenase exhibited various levels of toxicity, with 1,1-dichloroethylene and trichloroethylene being the most potent inactivators of propylene oxidation and 1,3- and 2,3-dichloropropylene being the most potent inactivators of propylene oxide-dependent O2 uptake. No toxic effects were seen when cells were incubated with chlorinated alkenes anaerobically, indicating that the product(s) of chlorinated alkene oxidation mediates toxicity.
Characteristics of a Hydrated, Alginate-Based Delivery System for Cultivation of the Button Mushroom
Authors: Romaine C. P. , Schlagnhaufer B.
Published: January 2020

The production of the button mushroom
Agaricus bisporus
with mycelium-colonized alginate pellets as an inoculant of the growing medium was investigated. Pellets having an irregular surface and porous internal structure were prepared by complexing a mixture of 1% sodium alginate, 2 to 6% vermiculite, 2% hygramer, and various concentrations of Nutrisoy (soy protein) with calcium chloride. The porous structure allowed the pellets to be formed septically and then inoculated and colonized with the fungus following sterilization. By using an enzyme-linked immunosorbent assay (ELISA) to estimate fungal biomass, the matrix components of the pellet were found to be of no nutritive value to
A. bisporus.
Pellets amended with Nutrisoy at a concentration of 0.5 to 8% supported extensive mycelial growth, as determined by significantly increased ELISA values, with a concentration of 4% being optimal and higher concentrations proving inhibitory. The addition of hydrated, mycelium-invaded pellets to the compost or casing layer supported the thorough colonization of the growing substrate and culminated in the formation of mushrooms that showed normal development and typical morphology. Yields and sizes of mushrooms were comparable from composts seeded with either colonized pellets or cereal grain spawn. Similarly, amending the casing layer with pelletized-mycelium-colonized compost resulted in a 2- to 3-day-earlier and more-synchronous emergence of mushrooms than with untreated casing. This technology shows the greatest potential as a pathogen-free inoculant of the casing layer in the commercial cultivation of mushrooms.
Role of heterotrophic bacteria in complete mineralization of trichloroethylene by Methylocystis sp. strain M
Authors: Uchiyama H , Nakajima T , Yagi O , Nakahara T
Published: January 2020

Biodegradation experiments with radioactively labeled trichloroethylene showed that 32% of the radioactive carbon was converted to glyoxylic acid, dichloroacetic acid and trichloroacetic acid and that the same percentage was converted to CO2 and CO after 140 h of incubation by a pure culture of a type II methane-utilizing bacterium, Methylocystis sp. strain M, isolated from a mixed culture, MU-81, in our laboratory. In contrast, these water-soluble (14C)trichloroethylene degradation products were completely or partially degraded further and converted to CO2 by the MU-81 mixed culture. This phenomenon was attributed to the presence of a heterotrophic bacterium (strain DA4), which was identified as Xanthobacter autotrophicus, in the MU-81 culture. The results indicate that the heterotrophic bacteria play an important role in complete trichloroethylene degradation by methanotrophs.
Metabolism of hexadecyltrimethylammonium chloride in Pseudomonas strain B1
Authors: van Ginkel C G , van Dijk J B , Kroon A G
Published: January 2020

A bacterium (strain B1) utilizing hexadecyltrimethylammonium chloride as a carbon and energy source was isolated from activated sludge and tentatively identified as a Pseudomonas sp. This bacterium only grew on alkyltrimethylammonium salts (C12 to C22) and possible intermediates of hexadecyltrimethylammonium chloride breakdown such as hexadecanoate and acetate. Pseudomonas strain B1 did not grow on amines. Simultaneous adaptation studies suggested that the bacterium oxidized only the alkyl chain of hexadecyltrimethylammonium chloride. This was confirmed by the stoichiometric formation of trimethylamine from hexadecyltrimethylammonium chloride. The initial hexadecyltrimethylammonium chloride oxygenase activity, measured by its ability to form trimethylamine, was NAD(P)H and O2 dependent. Finally, assays of aldehyde dehydrogenase, hexadecanoyl-coenzyme A dehydrogenase, and isocitrate lyase in cell extracts revealed the potential of Pseudomonas strain B1 to metabolize the alkyl chain via beta-oxidation.
A new assay for lignin-type peroxidases employing the dye azure B
Authors: Archibald F S
Published: January 2020

The discovery in 1983 of fungal "ligninases" capable of catalyzing the peroxidation of nonphenolic aromatic lignin components has been seen as a major advance in understanding how certain basidiomycete fungi can completely degrade lignin. The ability of these lignin-type peroxidases to covert millimolar concentrations of veratryl alcohol to veratraldehyde, indicated by a change in the A310 of veratraldehyde, has become the standard assay for routine quantitation of LP activity. A new assay based on the oxidation of micromolar concentrations of the dye Azure B is presented. Although it is as simple and rapid as the veratryl alcohol assay, it appears to overcome some of the shortcomings of that assay. In particular, interference from UV- and short-wavelength visible-light-absorbing materials is greatly reduced and assay specificity is improved.
Metabolic and energetic control of Pseudomonas mendocina growth during transitions from aerobic to oxygen-limited conditions in chemostat cultures
Authors: Verdoni N , Aon M A , Lebeault J M
Published: January 2020

Several metabolic fluxes were analyzed during gradual transitions from aerobic to oxygen-limited conditions in chemostat cultures of Pseudomonas mendocina growing in synthetic medium at a dilution rate of 0.25 h-1. P. mendocina growth was glucose limited at high oxygen partial pressures (70 and 20% pO2) and exhibited an oxidative type of metabolism characterized by respiratory quotient (RQ) values of 1.0. A similar RQ value was obtained at low pO2 (2%), and detectable levels of acetic, formic, and lactic acids were determined in the extracellular medium. RQs of 0.9 +/- 0.12 were found at 70% pO2 for growth rates ranging from 0.025 to 0.5 h-1. At high pO2, the control coefficients of oxygen on catabolic fluxes were 0.19 and 0.22 for O2 uptake and CO2 production, respectively. At low pO2 (2%), the catabolic and anabolic fluxes were highly controlled by oxygen. P. mendocina showed a mixed-type fermentative metabolism when nitrogen was flushed into chemostat cultures. Ethanol and acetic, lactic, and formic acids were excreted and represented 7.5% of the total carbon recovered. Approximately 50% of the carbon was found as uronic acids in the extracellular medium. Physiological studies were performed under microaerophilic conditions (nitrogen flushing) in continuous cultures for a wide range of growth rates (0.03 to 0.5 h-1). A cell population, able to exhibit a near-maximum theoretical yield of ATP (YmaxATP = 25 g/mol) with a number of ATP molecules formed during the transfer of an electron towards oxygen along the respiration chain (P/O ratio) of 3, appears to have adapted to microaerophilic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Rapid determination of members of the family Enterobacteriaceae in drinking water by an immunological assay using a monoclonal antibody against enterobacterial common antigen
Authors: Hübner I , Steinmetz I , Obst U , Giebel D , Bitter-Suermann D
Published: January 2020

An immunological method for the detection of members of the family Enterobacteriaceae in drinking water was developed. The method was based on a sandwich enzyme-linked immunosorbent assay (ELISA) with monoclonal antibody immunoglobulin G2a 898 against enterobacterial common antigen. The enterobacterial common antigen sandwich ELISA combined with selective preenrichment culture could be performed in only 24 h. Six hundred sixty-eight water samples from a variety of German public water supplies were screened to verify the effectiveness of the new method. Ninety-eight percent of the results obtained by the immunological method could be confirmed by conventional microbiological methods. The immunological method proved to be considerably faster and more specific and sensitive than the standard method specified by the German drinking water regulations.
Bacterial Disproportionation of Elemental Sulfur Coupled to Chemical Reduction of Iron or Manganese
Authors: Thamdrup Bo , Finster Kai , Hansen Jens Würgler , Bak Friedhelm
Published: January 2020

A new chemolithotrophic bacterial metabolism was discovered in anaerobic marine enrichment cultures. Cultures in defined medium with elemental sulfur (S
0
) and amorphous ferric hydroxide (FeOOH) as sole substrates showed intense formation of sulfate. Furthermore, precipitation of ferrous sulfide and pyrite was observed. The transformations were accompanied by growth of slightly curved, rod-shaped bacteria. The quantification of the products revealed that S
0
was microbially disproportionated to sulfate and sulfide, as follows: 4S
0
+ 4H
2
O → SO
4
2-
+ 3H
2
S + 2H
+
. Subsequent chemical reactions between the formed sulfide and the added FeOOH led to the observed precipitation of iron sulfides. Sulfate and iron sulfides were also produced when FeOOH was replaced by FeCO
3
. Further enrichment with manganese oxide, MnO
2
, instead of FeOOH yielded stable cultures which formed sulfate during concomitant reduction of MnO
2
to Mn
2+
. Growth of small rod-shaped bacteria was observed. When incubated without MnO
2
, the culture did not grow but produced small amounts of SO
4
2-
and H
2
S at a ratio of 1:3, indicating again a disproportionation of S
0
. The observed microbial disproportionation of S
0
only proceeds significantly in the presence of sulfide-scavenging agents such as iron and manganese compounds. The population density of bacteria capable of S
0
disproportionation in the presence of FeOOH or MnO
2
was high, > 10
4
cm
-3
in coastal sediments. The metabolism offers an explanation for recent observations of anaerobic sulfide oxidation to sulfate in anoxic sediments.
Arbitrary primer polymerase chain reaction, a powerful method to identify Bacillus thuringiensis serovars and strains
Authors: Brousseau R , Saint-Onge A , Préfontaine G , Masson L , Cabana J
Published: January 2020

Arbitrary primer polymerase chain reaction technology has been applied to the identification of commercial strains of Bacillus thuringiensis by using total DNAs extracted from single bacterial colonies as templates. Characteristic DNA banding patterns can be readily and reproducibly obtained by agarose gel electrophoresis. This method has been used to distinguish commercial products containing B. thuringiensis serovar kurstaki (3a3b). When a single primer was used this method was capable of producing discriminating DNA fingerprints for 33 known serovars. Differentiation from the closely related species Bacillus cereus is also readily achieved. This technique should prove to be a powerful tool for identification and discrimination of individual B. thuringiensis strains.
Differentiation of Two Abortive Mechanisms by Using Monoclonal Antibodies Directed toward Lactococcal Bacteriophage Capsid Proteins
Authors: Moineau Sylvain , Durmaz Evelyn , Pandian Sithian , Klaenhammer Todd R.
Published: January 2020

Monoclonal antibodies were used to monitor the accumulation of the major capsid protein of the lactococcal small isometric bacteriophage u136 (P335 species) over the course of a one-step growth curve. A sandwich enzyme-linked immunosorbent assay was then used to distinguish two abortive phage resistance mechanisms, Hsp and Prf. Capsid protein production of u136 was almost totally inhibited by the Hsp-induced abortive mechanism, supporting previous data that this mechanism blocks phage DNA replication. Prf-induced abortive infection only partially (50%) inhibited capsid protein production, suggesting that this mechanism targets some other point, perhaps within transcription or translation processes. The results confirmed that Hsp and Prf act at different targets in the phage lytic cycle. Use of monoclonal antibodies also demonstrated that production of the major capsid protein is a nonlimiting step in the lytic cycle of lactococcal phage u136.
Insertion of Transposon Tn
917
Derivatives into the
Lactococcus lactis
subsp.
lactis
Chromosome
Authors: Israelsen Hans , Hansen Egon Bech
Published: January 2020

Two transposition vectors, pTV32 and pLTV1, containing transposon Tn
917
derivatives TV32 and LTV1, respectively, were introduced into
Lactococcus lactis
subsp.
lactis
MG1614. It was found that pTV32 and pLTV1 replicate and that TV32 and LTV1 transpose in this strain. A protocol for production of a collection of Tn
917
insertions in
L. lactis
subsp.
lactis
was developed. The physical locations of TV32 on the chromosomal
Sma
I fragments of 62 independent transpositions were established by pulsed-field gel electrophoresis. These transpositions could be divided into at least 38 different groups that exhibited no Tn
917
-dominating hot spots on the
L. lactis
subsp.
lactis
chromosome. A total of 10 of the 62 transpositions resulted in strains that express β-galactosidase. This indicates that there was fusion of the promoterless
lacZ
of the Tn
917
derivatives to a chromosomal promoter. Thus, the Tn
917
-derived transposons should be powerful genetic tools for studying
L. lactis
subsp.
lactis.