bluuebunny/crossref_metadata_2025 huggingface dataset:
Release of Dissolved Organic Nitrogen by Marine Diazotrophic Cyanobacteria,
Trichodesmium
spp
Authors: Glibert Patricia M. , Bronk Deborah A.
Published: January 2020

Trichodesmium
sp. is a filamentous, colonial cyanobacterium which contributes substantially to the input of nitrogen in tropical and subtropical oceanic waters through nitrogen fixation (N
2
fixation). We applied a
15
N tracer technique to assess the rate of release of dissolved organic nitrogen (DON) from this cyanobacterium and compared those rates with rates of N
2
fixation determined for the same assemblages at the same times of day. Rates of release of DON showed considerable variation within replicate experiments and were variable depending on time of day and duration of time course experiments. On average, rates of DON release were ca. 50% the rates of N
2
fixation. We also fractionated the DON released by using ultrafiltration and found that 60 to 80% of the total organic release was of the size class <10,000 Da. The release of these organic compounds by
Trichodesmium
spp. is likely a significant source of new nitrogen for the associated bacteria or the non-nitrogen-fixing filaments of the
Trichodesmium
colonies.
Investigation of an Iron-Oxidizing Microbial Mat Community Located near Aarhus, Denmark: Field Studies
Authors: Emerson David , Revsbech Niels Peter
Published: January 2020

We investigated the microbial community that developed at an iron seep where anoxic groundwater containing up to 250 μM Fe
2+
flowed out of a rock wall and dense, mat-like aggregations of ferric hydroxides formed at the oxic-anoxic interface. In situ analysis with oxygen microelectrodes revealed that the oxygen concentrations in the mat were rarely more than 50% of air saturation and that the oxygen penetration depth was quite variable, ranging from <0.05 cm to several centimeters. The bulk pH of the mat ranged from 7.1 to 7.6. There appeared to be a correlation between the flow rates at different subsites of the mat and the morphotypes of the microorganisms and Fe oxides that developed. In subsites with low flow rates (<2 ml/s), the iron-encrusted sheaths of
Leptothrix ochracea
predominated. Miniature cores revealed that the top few millimeters of the mat consisted primarily of
L. ochracea
sheaths, only about 7% of which contained filaments of cells. Deeper in the mat, large particulate oxides developed, which were often heavily colonized by unicellular bacteria that were made visible by staining with acridine orange. Direct cell counts revealed that the number of bacteria increased from approximately 10
8
to 10
9
cells per cm
3
and the total iron concentration increased from approximately 0.5 to 3 mmol/cm
3
with depth in the mat. Primarily because of the growth of
L. ochracea,
the mat could accrete at rates of up to 3.1 mm/day at these subsites. The iron-encrusted stalks of
Gallionella
spp. prevailed in localized zones of the same low-flow-rate subsites, usually close to where the source water emanated from the wall. These latter zones had the lowest O
2
concentrations (<10% of the ambient concentration), confirming the microaerobic nature of
Gallionella
spp. In subsites with high flow rates (>6 ml/s) particulate Fe oxides were dominant; direct counts revealed that up to 10
9
cells of primarily unicellular bacteria per cm
3
were associated with these particulate oxides. These zones exhibited little vertical stratification in either the number of cells or iron concentration. Finally, mat samples incubated anaerobically in the presence of acetate or succinate exhibited significant potential for iron reduction, suggesting the possibility that a localized iron cycle could occur within the mat community.
Characterization of Acinetobacter type strains and isolates obtained from wastewater treatment plants by PCR fingerprinting
Authors: Wiedmann-al-Ahmad M , Tichy H V , Schön G
Published: January 2020

Acinetobacter type strains and isolates from wastewater treatment plants were differentiated by PCR fingerprinting. On the first level, PCR fingerprinting with two tRNA-gene specific primers (T5B and T3A) was used for the identification of species (genospecies 1 to 17). On the second level, a single arbitrary primer (DAF 4) was employed for strain differentiation. Upon comparison of Acinetobacter type strains with 28 sewage sludge isolates, 2 could be classified as belonging to A. johnsonii, 8 isolates could be classified as A. lwoffii, 8 could be classified as A. baumannii, and 9 isolates were very closely related to the Acinetobacter species A. junii; only 1 isolate could not be classified as one of the Acinetobacter type strains. The PCR fingerprinting method was found to be a reproducible and fast method for differentiation and identification of Acinetobacter isolates. Because of some resulting discrepancies compared with previously described identification schemes, e.g., DNA-DNA hybridization methods, the original identification experiments should be repeated and the results should be reassessed.
Metabolic Pathways Leading to Mercury Methylation in
Desulfovibrio desulfuricans
LS
Authors: Choi Sung-Chan , Chase Theodore , Bartha Richard
Published: January 2020

The synthesis of methylmercury by
Desulfovibrio desulfuricans
LS was investigated on the basis of
14
C incorporation from precursors and the measurement of relevant enzyme activities in cell extracts. The previously observed incorporation of C-3 from serine into methylmercury was confirmed by measurement of relatively high activities of serine hydroxymethyltransferase and other enzymes of this pathway. High rates of label incorporation into methylmercury from H
14
COO
-
and H
14
CO
3
-
prompted the assay of enzymes of the acetyl coenzyme A (CoA) synthase pathway. These enzymes were found to be present but at activity levels much lower than those reported for acetogens. Propyl iodide inhibited methylmercury and acetyl-CoA syntheses to similar extents, and methylmercury synthesis was found to compete with acetyl-CoA synthesis for methyl groups. On the basis of these findings, we propose that in methylmercury synthesis by
D. desulfuricans
LS the methyl group is transferred from CH
3
-tetrahydrofolate via methylcobalamin. The methyl group may originate from C-3 of serine or from formate via the acetyl-CoA synthase pathway. These pathways are not unique to
D. desulfuricans
LS, and thus the ability of this bacterium to methylate mercury is most likely associated with the substrate specificity of its enzymes.
Sensitive and specific detection of Xanthomonas campestris pv. pelargonii with DNA primers and probes identified by random amplified polymorphic DNA analysis
Authors: Manulis S , Valinsky L , Lichter A , Gabriel D W
Published: January 2020

The random amplified polymorphic DNA method was used to distinguish strains of Xanthomonas campestris pv. pelargonii from 21 other Xanthomonas species and/or pathovars. Among the 42 arbitrarily chosen primers evaluated, 3 were found to reveal diagnostic polymorphisms when purified DNAs from compared strains were amplified by the PCR. The three primers revealed DNA amplification patterns which were conserved among all 53 strains tested of X. campestris pv. pelargonii isolated from various locations worldwide. The distinctive X. compestris pv. pelargonii patterns were clearly different from those obtained with any of 46 other Xanthomonas strains tested. An amplified 1.2-kb DNA fragment, apparently unique to X. campestris pv. pelargonii by these random amplified polymorphic DNA tests, was cloned and evaluated as a diagnostic DNA probe. It hybridized with total DNA from all 53 X. campestris pv. pelargonii strains tested and not with any of the 46 other Xanthomonas strains tested. The DNA sequence of the terminal ends of this 1.2-kb fragment was obtained and used to design a pair of 18-mer oligonucleotide primers specific for X. campestris pv. pelargonii. The custom-synthesized primers amplified the same 1.2-kb DNA fragment from all 53 X. campestris pv. pelargonii strains tested and failed to amplify DNA from any of the 46 other Xanthomonas strains tested. DNA isolated from saprophytes associated with the geranium plant also did not produce amplified DNA with these primers. The sensitivity of the PCR assay using the custom-synthesized primers was between 10 and 50 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Utilization of Dissolved Nitrogen by Heterotrophic Bacterioplankton: Effect of Substrate C/N Ratio
Authors: Jørgensen Niels O. G. , Kroer Niels , Coffin Richard B.
Published: January 2020

The significance of dissolved combined amino acids (DCAA), dissolved free amino acids (DFAA), and dissolved DNA (D-DNA) as sources of C and N for marine bacteria in batch cultures with variable substrate C/N ratios was studied. Glucose, ammonium, alanine, and phosphate were added to the cultures to produce C/N ratios of 5, 10, and 15 and to ensure that phosphorus was not limiting. Maximum bacterial particulate organic carbon production (after 25 h of incubation) was inversely correlated with the C/N ratio: with the addition of identical amounts of carbon, the levels of production were 9.0-, 10.0-, and 11.1-fold higher at C/N ratios of 15, 10, and 5, respectively, relative to an unamended control. The bacterial growth efficiency increased from 22% (control cultures) to 44 to 53% in the cultures with manipulated C/N ratios (C/N-manipulated cultures). Net carbon incorporation from DCAA, DFAA, and D-DNA supported on average 19, 4, and 3% (control cultures and cultures to which only phosphate was added [+P cultures]) and 5, 4, and 0.3% of the particulate organic carbon production (C/N-manipulated cultures), respectively. In the C/N-manipulated cultures, a 2.6- to 3.4-fold-higher level of incorporation of DCAA, relative to that in the control cultures, occurred. Incorporation of D-DNA increased with the substrate C/N ratio, suggesting that D-DNA mainly was a source of N to the bacteria. Organic N (DCAA, DFAA, and D-DNA) sustained 14 to 49% of the net bacterial N production. NH
4
+
was the dominant N source and constituted 55 to 99% of the total N uptake. NO
3
-
contributed up to 23% to the total N uptake but was released in two cultures. The studied N compounds sustained nearly all of the bacterial N demand. Our results show that the C/N ratio of dissolved organic matter available to bacteria has a significant influence on the incorporation of individual compounds like DCAA and D-DNA.
Production and Characterization of an Exopolysaccharide Excreted by a Deep-Sea Hydrothermal Vent Bacterium Isolated from the Polychaete Annelid
Alvinella pompejana
Authors: Vincent P. , Pignet P. , Talmont F. , Bozzi L. , Fournet B. , Guezennec J. , Jeanthon C. , Prieur D.
Published: January 2020

The heterotrophic and mesophilic marine bacterium HYD-1545 was isolated on a metal-amended medium from the dorsal integument of the hydrothermal vent polychaete
Alvinella pompejana
. This strain, which can be assigned to the genus
Alteromonas
on the basis of its G+C content and phenotypical features, produced large amounts of an acidic polysaccharide in batch cultures. The polysaccharide was excreted during the stationary phase of growth and contained glucose, galactose, glucuronic acid, galacturonic acid, and 4,6-O-(1-carboxyethilidene)-galactose as major components. This polysaccharide was a polyelectrolyte, and the viscosity of its solutions depended on the ionic strength. The decrease in viscosity with increasing NaCl concentrations and the effect of Ca
2+
in decreasing the viscosity at low Ca
2+
concentrations support a model in which the polysaccharide carries anionic groups. However, an unusual behavior was observed at higher concentrations and could be related to intermolecular interactions involving Ca
2+
ions.
Hydrolysis of Oleuropein by
Lactobacillus plantarum
Strains Associated with Olive Fermentation
Authors: Ciafardini G. , Marsilio V. , Lanza B. , Pozzi N.
Published: January 2020

Oleuropein (Chemical Abstracts Service registry number 32619-42-4), a bitter-tasting secoiridoid glucoside commonly found in leaves of the olive tree as well as in olives (
Olea europaea
L.), was found to be hydrolyzed by the β-glucosidase (EC 3.2.1.2.1) produced by oleuropeinolytic
Lactobacillus plantarum
-type strains. Three strains, designated B17, B20, and B21, were isolated from the brine of naturally ripe olives not treated with alkali. These strains were rod-shaped forms, grown at a pH 3.5 limit, and tolerated 1% oleuropein and 8% NaCl in the growth medium. The β-glucosidase produced hydrolyzed 5-bromo-4-chloro-3-indolyl-β-
d
-glucopy-ranoside as well as oleuropein. The presence of 2% glucose in the medium inhibited activity by 40 to 50%, depending on the bacterial strain. Chromatographic analysis of the trimethylsilyl derivatives of the products obtained after 7 days of incubation at 30°C of strain B21 showed all the hydrolysis products of oleuropein, i.e., aglycone, iridoid monoterpen, and 3,4-dihydroxyphenylethanol (hydroxytyrosol). Oleuropein and its aglycone after 21 days of incubation decreased to trace levels with the simultaneous increase in concentration of β-3,4-dihydroxyphenylethanol.
Fungal production of volatiles during growth on fiberglass
Authors: Ezeonu I M , Price D L , Simmons R B , Crow S A , Ahearn D G
Published: January 2020

Acoustic and thermal fiberglass insulation materials used in heating, ventilation, and air-conditioning systems were colonized with fungi in laboratory chambers. The mixed fungal population, principally Aspergillus versicolor, Acremonium obclavatum, and Cladosporium herbarum, produced odoriferous volatiles, including 2-ethyl hexanol, cyclohexane, and benzene. These volatiles may be related to poor indoor air quality and the sick building syndrome.
New Composite Biocarriers Engineered To Contain Adsorptive and Ion-Exchange Properties Improve Immobilized-Cell Bioreactor Process Dependability
Authors: Durham Don R. , Marshall Leda C. , Miller James G. , Chmurny Alan B.
Published: January 2020

Novel biocarriers that combine the adsorptive properties of activated carbon with the ion-exchange properties of zeolite-based type Z inorganic oxide biocarriers (D. R. Durham, L. C. Marshall, J. G. Miller, and A. B. Chmurny, Appl. Environ, Microbiol. 60:3329-3335, 1994.) were developed. These biocarriers, designated Type CZ, possess fundamental properties that heretofore have not been described for available microbial immobilization matrices. Type CZ biocarriers provide an environment that promotes dense microbial colonization and maintains bioreactor productivity by buffering immobilized microorganisms from unfavorable operating conditions. Data demonstrating protection of immobilized bacteria from organic shock loads and extended pH shocks are presented. In addition, bioreactors containing the composite Type CZ biocarriers continue to remove waste stream contaminants during periods of oxygen deprivation and nutrient limitation.
Correlation of bioenergetic parameters with cell death in Listeria monocytogenes cells exposed to nisin
Authors: Winkowski K , Bruno M E , Montville T J
Published: January 2020

In Listeria monocytogenes, nisin induced ATP efflux, reduced the intracellular ATP concentration within 1 min, and dissipated the proton motive force within 2 min. Efflux accounted for only 20% of the ATP depletion, suggesting that ATP hydrolysis also occurred. ATP efflux depended on nisin concentration and followed saturation kinetics. These results suggest that nisin breaches the membrane permeability barrier in a manner more consistent with pore formation than with a nonspecific detergent-like membrane destabilization.
Construction of Agrobacterium strains by electroporation of genomic DNA and its utility in analysis of chromosomal virulence mutations
Authors: Charles T C , Doty S L , Nester E W
Published: January 2020

We have extended the technique of electroporation as a genetic tool for manipulating the Agrobacterium tumefaciens chromosome. We used this technique to introduce chromosomal DNA into recipient A. tumefaciens strains by electroporation and constructed isogenic chvE mutants that share the same chromosomal background but differ in their types of pTi (octopine or nopaline). Both nopaline and octopine pTi-carrying chvE mutants were deficient in vir regulon induction and exhibited similar reductions in host range.
New Method for Isolating Barophiles from Intestinal Contents of Deep-Sea Fishes Retrieved from the Abyssal Zone
Authors: Nakayama Akihiko , Yano Yutaka , Yoshida Katsuhiko
Published: January 2020

We devised a new method (the dorayaki method) using marine agar under in situ pressures to isolate barophilic bacteria from the intestinal contents of three deep-sea fishes (two
Coryphaenoides yaquinae
samples and one
Ilyophis
sp. sample) retrieved from depths of 4,700 to 6,100 m in the Northwest Pacific Ocean. All 10 strains isolated from one sample (
C. yaquinae
) were obligately barophilic. One of the 10 strains did not grow at atmospheric pressure and 103.4 MPa but did grow well between 20.7 and 82.7 MPa, with optimal growth at 41.4 MPa. This method is useful for isolating psychrophilic and barophilic deep-sea bacteria.
High-efficiency transformation of Pichia stipitis based on its URA3 gene and a homologous autonomous replication sequence, ARS2
Authors: Yang V W , Marks J A , Davis B P , Jeffries T W
Published: January 2020

This paper describes the first high-efficiency transformation system for the xylose-fermenting yeast Pichia stipitis. The system includes integrating and autonomously replicating plasmids based on the gene for orotidine-5'-phosphate decarboxylase (URA3) and an autonomous replicating sequence (ARS) element (ARS2) isolated from P. stipitis CBS 6054. Ura- auxotrophs were obtained by selecting for resistance to 5-fluoroorotic acid and were identified as ura3 mutants by transformation with P. stipitis URA3. P. stipitis URA3 was cloned by its homology to Saccharomyces cerevisiae URA3, with which it is 69% identical in the coding region. P. stipitis ARS elements were cloned functionally through plasmid rescue. These sequences confer autonomous replication when cloned into vectors bearing the P. stipitis URA3 gene. P. stipitis ARS2 has features similar to those of the consensus ARS of S. cerevisiae and other ARS elements. Circular plasmids bearing the P. stipitis URA3 gene with various amounts of flanking sequences produced 600 to 8,600 Ura+ transformants per micrograms of DNA by electroporation. Most transformants obtained with circular vectors arose without integration of vector sequences. One vector yielded 5,200 to 12,500 Ura+ transformants per micrograms of DNA after it was linearized at various restriction enzyme sites within the P. stipitis URA3 insert. Transformants arising from linearized vectors produced stable integrants, and integration events were site specific for the genomic ura3 in 20% of the transformants examined. Plasmids bearing the P. stipitis URA3 gene and ARS2 element produced more than 30,000 transformants per micrograms of plasmid DNA. Autonomously replicating plasmids were stable for at least 50 generations in selection medium and were present at an average of 10 copies per nucleus.
Detection of Salmonella typhimurium in dairy products with flow cytometry and monoclonal antibodies
Authors: McClelland R G , Pinder A C
Published: January 2020

Flow cytometry, combined with fluorescently labelled monoclonal antibodies, offers advantages of speed and sensitivity for the detection of specific pathogenic bacteria in foods. We investigated the detection of Salmonella typhimurium in eggs and milk. Using a sample clearing procedure, we determined that the detection limit was on the order of 10(3) cells per ml after a total analysis time of 40 min. After 6 h of nonselective enrichment, the detection limits were 10 cells per ml for milk and 1 cell per ml for eggs, even in the presence of a 10,000-fold excess of Escherichia coli cells.
Reduction and mutagenic activation of nitroaromatic compounds by a Mycobacterium sp
Authors: Rafii F , Selby A L , Newton R K , Cerniglia C E
Published: January 2020

Mycobacterium sp. strain Pyr-1 cells, which were grown to the stationary phase in media with and without pyrene, were centrifuged and resuspended in a medium containing 1-nitropyrene. Cells that had been grown with pyrene oxidized up to 20% of the added 1-nitropyrene to 1-nitropyrene-cis-9,10- and 4,5-dihydrodiols. However, cells that had been grown without pyrene reduced up to 70% of the 1-nitropyrene to 1-aminopyrene but did not produce dihydrodiols. The nitroreductase activity was oxygen insensitive, intracellular, and inducible by nitro compounds. Nitroreductase activity was inhibited by p-chlorobenzoic acid, o-iodosobenzoic acid, menadione, dicumarol, and antimycin A. Extracts from cells that had been grown without pyrene activated 1-nitropyrene, 1-amino-7-nitrofluorene, 2,7-dinitro-9-fluorenone, 1,3-dinitropyrene, 1,6-dinitropyrene, and 6-nitrochrysene to DNA-damaging products, as shown in Salmonella typhimurium tester strains by the reversion assay and by induction of the umuC gene. Activation of nitro compounds, as shown by the umu test, was enhanced by NADPH. This study shows that Mycobacterium sp. strain Pyr-1 metabolizes nitroaromatic compounds by both oxidative and reductive pathways. During reduction, it generates products that are mutagenic.
Effect of growth phase and parental cell survival in river water on plasmid transfer between Escherichia coli strains
Authors: Muela A , Pocino M , Arana I , Justo J I , Iriberri J , Barcina I
Published: January 2020

We evaluated the transfer to and from Escherichia coli of endogenously isolated plasmid material from the River Butrón during the growth of three donor strains and two recipient strains as well as after the survival of these parental cells in river water. Transfer frequency varied greatly during the growth of donor cells, with minimum values in the exponential phase; frequency remained constant, however, during the growth of recipient strains. After survival in river water, donor cells lost their ability for plasmid transfer before any other physiological variations in the cells caused by environmental stress were detected. Under the same conditions and during equal periods, however, no variation in the ability of recipient cells to receive and express plasmid material was observed.
PCR primers that allow intergeneric differentiation of ascomycetes and their application to Verticillium spp
Authors: Li K N , Rouse D I , German T L
Published: January 2020

A pair of conserved PCR primers, designated NMS1 and NMS2, that amplify a region in the mitochondrial small rRNA gene region were designed for fungi belonging to the class Ascomycetes. These primers were tested with members of eight fungal genera (Aspergillus, Fusarium, Magnaporthe, Mycospharella, Neurospora, Saccharomyces, Sclerotinia, Verticillium) and 10 Verticillium species (Verticillium albo-atrum, Verticillium chlamydosporium, Verticillium cinnebarium, Verticillium dahliae, Verticillium fungicola, Verticillium lecanii, Verticillium lateritium, Verticillium nigrescens, Verticillium psaliotae, and Verticillium tricorpus). The primers were also tested with 35 isolates of V. dahliae obtained from diverse geographic areas and diverse hosts. The results of a restriction fragment length polymorphism analysis of the region amplified by the primers differentiated the genera examined and the results of a DNA sequence analysis of the amplified region differentiated the Verticillium species. Two Fusarium species were also differentiated by the results of the restriction fragment length polymorphism analysis. On the basis of the nucleotide sequences of the amplified regions, we obtained a pair of PCR primers that could be used to differentiate V. dahliae from the other fungal isolates tested, including V. albo-atrum, a closely related plant-pathogenic species. The V. dahliae-specific PCR primer may aid in more rapid and specific detection of the pathogen directly in plant and/or soil samples. PCR primers NMS1 and NMS2 may be used as potential mitochondrial markers for studying fungal cytoplasmic inheritance of ascomycetes and for identifying DNA probes that are informative at or below the genus level.
Involvement of an
N
-Acetylglucosaminidase in Autolysis of
Propionibacterium freudenreichii
CNRZ 725
Authors: Lemee Riwanon , Lortal Sylvie , Cesselin Bénédicte , van Heijenoort Jean
Published: January 2020

Propionibacterium freudenreichii
plays an important role in Swiss cheese ripening (it produces propionic acid, acetic acid, and CO
2
). Moreover, autolysis of this organism certainly contributes to proteolysis and lipolysis of the curd because intracellular enzymes are released. By varying external factors, we determined the following conditions which promoted autolysis of both whole cells and isolated cell walls of
P. freudenreichii
CNRZ 725: (i) 0.1 M potassium phosphate buffer (pH 5.8) at 40°C and (ii) 0.05 to 0.1 M KCl at 40°C. We found that early-exponential-phase cells possessed the highest autolytic activity. It should be emphasized that the pH of Swiss cheese curd (pH 5.5 to 5.7) is near the optimal pH which we determined. Ultrastructural observations by electron microscopy revealed a 16-nm-thick homogeneous cell wall, as well as degradation of the cell wall that occurred concomitantly with cell autolysis. In the presence of 0.05 M potassium chloride, there was a great deal of isolated cell wall autolysis (the optical density at 650 nm decreased 77.5% ± 7.3% in 3 h), and one-half of the peptidoglycan material was released. Finally, the main autolytic activity was due to an
N
-acetylglucosaminidase activity.
Bleaching of Hardwood Kraft Pulp with Manganese Peroxidase Secreted from
Phanerochaete sordida
YK-624
Authors: Kondo Ryuichiro , Harazono Koichi , Sakai Kokki
Published: January 2020

In vitro bleaching of an unbleached hardwood kraft pulp was performed with manganese peroxidase (MnP) from the fungus
Phanerochaete sordida
YK-624. When the kraft pulp was treated with partially purified MnP in the presence of MnSO
4
, Tween 80, and sodium malonate with continuous addition of H
2
O
2
at 37°C for 24 h, the pulp brightness increased by about 10 points and the kappa number decreased by about 6 points compared with untreated pulp. The pulp brightness was also increased by 43 points to 75.5% by multiple (six) treatments with MnP combined with alkaline extraction. Our results indicate that in vitro degradation of residual lignin in hardwood kraft pulp with MnP is possible.
Zwittermicin A-producing strains of Bacillus cereus from diverse soils
Authors: Stabb E V , Jacobson L M , Handelsman J
Published: January 2020

Bacillus cereus UW85 produces a novel aminopolyol antibiotic, zwittermicin A, that contributes to the ability of UW85 to suppress damping-off of alfalfa caused by Phytophthora medicaginis. UW85 produces a second antibiotic, provisionally designated antibiotic B, which also contributes to suppression of damping-off but has not been structurally defined yet and is less potent than zwittermicin A. The purpose of this study was to isolate genetically diverse strains of B. cereus that produce zwittermicin A and suppress disease. We found that most isolates of B. cereus that were sensitive to phage P7 or inhibited the growth of Erwinia herbicola produced zwittermicin A; therefore, phage typing and E. herbicola inhibition provided indirect, but rapid screening tests for identification of zwittermicin A-producing isolates. We used these tests to screen a collection of 4,307 B. cereus and Bacillus thuringiensis isolates obtained from bacterial stock collections and from diverse soils collected in Honduras, Panama, Australia, The Netherlands, and the United States. A subset of the isolates screened by the P7 sensitivity and E. herbicola inhibition tests were assayed directly for production of zwittermicin A, leading to the identification of 57 isolates that produced zwittermicin A; 41 of these isolates also produced antibiotic B. Eight isolates produced antibiotic B but not zwittermicin A. The assay for phage P7 sensitivity was particularly useful because of its simplicity and rapidity and because 22 of the 23 P7-sensitive isolates tested produced zwittermicin A. However, not all zwittermicin A-producing isolates were sensitive to P7, and the more labor-intensive E. herbicola inhibition assay identified a larger proportion of the zwittermicin A producers.(ABSTRACT TRUNCATED AT 250 WORDS)
Digestion of Herring by Indigenous Bacteria in the Minke Whale Forestomach
Authors: Olsen Monica A. , Aagnes Tove H. , Mathiesen Svein D.
Published: January 2020

Northeastern Atlantic minke whales (
Balaenoptera acutorostrata
) have a multichambered stomach system which includes a nonglandular forestomach resembling that of ruminants. Bacteria from the forestomachs of herring-eating whales were enumerated and isolated in an anaerobic rumen-like culture medium (M8W medium). The total viable population of anaerobic bacteria ranged from 73 × 10
7
to 145 × 10
8
/ml of forestomach fluid (
n
= 4).
Lactobacillus
spp. (19.7%),
Streptococcus
spp. (35.9%), and
Ruminococcus
spp. (12.8%) were the most common of the bacterial strains (
n
= 117) isolated by use of M8W medium from the forestomach fluid population of two minke whales. Most of the isolates stained gram positive (93.2%), 62.4% were cocci, and all strains were strictly anaerobic. The population of lipolytic bacteria in one animal, enumerated by use of a selective lipid medium, constituted 89.7% of the viable population. The total viable population of anaerobic bacteria in freshly caught and homogenized herring (
Clupea harengus
) ranged from 56.7 to 95.0 cells per gram of homogenized prey (
n
= 3) when M8W medium was used.
Pediococcus
spp. (30.6%) and
Aerococcus
spp. (25.0%) were most common of the bacterial strains (
n
= 72) isolated from the homogenized herring. Most of the bacterial strains were gram positive (80.6%), and 70.8% were cocci. Unlike the forestomach bacterial population, as many as 61.1% of the strains from the herring were facultatively anaerobic. All bacterial strains isolated from the prey had phenotypic patterns different from those of strains isolated from the dominant bacterial population in the forestomach, indicating that the forestomach microbiota is indigenous. Scanning electron microscopic examinations revealed large numbers of bacteria, surrounded by a glycocalyx, attached to partly digested food particles in the forestomach. These data support the hypothesis that symbiotic microbial digestion occurs in the forestomach and that the bacteria are indigenous to minke whales.
Phylogenetic analysis of a highly specific association between ectosymbiotic, sulfur-oxidizing bacteria and a marine nematode
Authors: Polz M F , Distel D L , Zarda B , Amann R , Felbeck H , Ott J A , Cavanaugh C M
Published: January 2020

The phylogenetic relationship of chemoautotrophic, sulfur-oxidizing, ectosymbiotic bacteria growing on a marine nematode, a Laxus sp. (formerly a Catanema sp.), to known endosymbionts and free-living bacteria was determined. Comparative 16S rRNA sequencing was used to investigate the unculturable nematode epibionts, and rRNA-targeted oligonucleotide hybridization probes were used to identify the ectosymbionts in situ. Both analyses revealed a remarkably specific and stable symbiosis. Unique hybridization of a specific probe to the ectosymbionts indicated that only one species of bacteria was present and growing on the cuticle of the nematode. Distance and parsimony methods used to infer phylogenetic trees both placed the nematode ectosymbionts at the base of a branch containing chemoautotrophic, sulfur-oxidizing endosymbionts of three bivalve families and of the tube worm Riftia pachyptila. The most closely related free-living bacteria were chemoautotrophic sulfur oxidizers belonging to the genus Thiomicrospira. Furthermore, our results suggested that a second, only distantly related group of thioautotrophic endosymbionts has as its deepest branch surface-colonizing bacteria belonging to the genus Thiothrix, some of which are capable of sulfur-oxidizing chemoautotrophic growth.
Preferential degradation of phenolic lignin units by two white rot fungi
Authors: Camarero S , Galletti G C , Martínez A T
Published: January 2020

The differential biodegradation of phenolic and nonphenolic (C-4-etherified) lignin units in wheat straw treated with the white rot fungi Pleurotus eryngii and Phanerochaete chrysosporium was investigated under solid-state fermentation conditions. Two analytical techniques applied to permethylated straw were used for this purpose, i.e., alkaline CuO degradation and analytical pyrolysis (both followed by gas chromatography-mass spectrometry for product identification). Despite differences in the enzymatic machinery produced, both ligninolytic fungi caused a significant decrease in the relative amount of phenolic lignin units during the degradation process. Nevertheless, no differences in the biodegradation rates of phenolic and etherified cinnamic acids were observed. Changes in lignin composition and cinnamic acid content were also analyzed in the phenolic and nonphenolic lignin moieties. The results obtained are discussed in the context of the enzymatic mechanisms of lignin biodegradation.
Precipitation of Metallic Cations by the Acidic Exopolysaccharides from
Bradyrhizobium japonicum
and
Bradyrhizobium (Chamaecytisus)
Strain BGA-1
Authors: Corzo J. , León-Barrios M. , Hernando-Rico V. , Gutierrez-Navarro A. M.
Published: January 2020

The interaction between the acidic exopolysaccharides produced by two
Bradyrhizobium
strains and several metal cations has been studied. Aqueous solutions in the millimolar range of Fe
3+
but not of Fe
2+
precipitated the exopolysaccharides from
Bradyrhizobium (Chamaecytisus)
strain BGA-1 and, to a lesser extent,
Bradyrhizobium japonicum
USDA 110. The precipitation was pH dependent, with a maximum around pH 3. The precipitate was redissolved by changing the pH and by Fe
3+
reduction or chelation. Deacetylation of
B. japonicum
polysaccharide increased its precipitation by Fe
3+
. At pH near neutrality, the polysaccharide from
Bradyrhizobium (Chamaecytisus)
strain BGA-1 stabilized Fe
3+
solutions, despite the insolubility of Fe(OH)
3
. Aluminum precipitated
Bradyrhizobium (Chamaecytisus)
polysaccharide but not the polysaccharide produced by
B. japonicum.
The precipitation showed a maximum at about pH 4.8, and the precipitate was redissolved after Al
3+
chelation with EDTA. Precipitation was inhibited by increases in the ionic strength over 10 mM.
Bradyrhizobium (Chamaecytisus)
polysaccharide was also precipitated by Th
4+
, Sn
2+
, Mn
2+
, and Co
2+
. The presence of Fe
3+
increased the exopolysaccharide precipitation by aluminum. No precipitation, gelation, or increase in turbidity of polysaccharide solutions occurred when K
+
, Na
+
, Ca
2+
, Mg
2+
, Cu
2+
, Cd
2+
, Pb
2+
, Zn
2+
, Hg
2+
, or U
6+
was added at several pH values. The results suggest that the precipitation is based on the interaction between carboxylate groups from different polysaccharide chains and the partially hydrolyzed aquoions of Fe
3+
, Al
3+
, Th
4+
, and Sn
2+
.
Ability of laboratory methods to predict in-use efficacy of antimicrobial preservatives in an experimental cosmetic
Authors: Farrington J K , Martz E L , Wells S J , Ennis C C , Holder J , Levchuk J W , Avis K E , Hoffman P S , Hitchins A D , Madden J M
Published: January 2020

The abilities of nine antimicrobial systems to preserve an experimental water-based cosmetic formulation were evaluated by six microbiological challenge tests: the U.S. Pharmacopeia test; the British Pharmacopeia test; the Cosmetic, Toiletry, and Fragrance Association test; the rapid screen test; the sequential challenge test; and the post-use test. The antimicrobial systems contained various combinations and amounts of two parabens and a quaternary compound in order to provide a broad range of preservation. The results obtained were compared with the abilities of the formulations to support maintenance and growth of microorganisms in microfloras obtained from human axilla areas and finger skin during an 8-week simulated in-use test. Without statistical analysis all of the tests predicted the results obtained with well-preserved or poorly preserved formulations. The rapid screen test was the best test for predicting differences at intermediate levels of preservation. Statistically, all of the tests were equivalent predictors of preservation efficacy in the in-use test (P = 0.05). At the P = 0.10 level, only the U.S. Pharmacopeia, British Pharmacopeia, rapid screen, Cosmetic, Toiletry, and Fragrance Association tests were significantly predictive. The results of prediction by a test, based on the preservative levels used, agreed well with the in-use test results (P = 0.01). A total of 20% of the formulations that contained excessive microbial levels contained human axilla microorganisms. The levels of preservation in failed products were similar to the levels of preservation in unused controls.
Dechlorination of trichlorofluoromethane (CFC-11) by sulfate-reducing bacteria from an aquifer contaminated with halogenated aliphatic compounds
Authors: Sonier D N , Duran N L , Smith G B
Published: January 2020

Groundwater samples were obtained from a deep aquifer contaminated with halogenated aliphatic compounds. One-milliliter samples contained 9.2 x 10(5) total bacteria (by acridine orange microscopic counts) and 2.5 x 10(3) sulfate-reducing bacteria (by most probable number analysis). Samples were incubated anaerobically in a basal salts medium with acetate as the electron donor and nitrate and sulfate as the electron acceptors. Residual levels of trichlorofluoromethane (CFC-11) in samples were biotically degraded, while trichloroethylene was not. When successively higher levels of CFC-11 were added, increasingly rapid degradation rates were observed. Concomitant with CFC-11 degradation was the near stoichiometric production of fluorodichloromethane (HCFC-21); the production of HCFC-21 was verified by mass spectrometry. CFC-11 degradation was dependent on the presence of acetate (or butyrate) and sulfate but was independent of nitrate. Other carbon sources such as lactate and isopropanol did not support the degradation. The addition of 1 mM sodium sulfide completely inhibited CFC-11 degradation; however, degradation occurred in the presence of 2 mM 2-bromoethanesulfonic acid. These results indicate that the anaerobic dechlorination of CFC-11 is carried out by sulfate-reducing bacteria and not by denitrifying or methanogenic bacteria.
Renibacterium salmoninarum, the causative agent of bacterial kidney disease in salmonid fish, detected by nested reverse transcription-PCR of 16S rRNA sequences
Authors: Magnússon H B , Fridjónsson O H , Andrésson O S , Benediktsdóttir E , Gudmundsdóttir S , Andrésdóttir V
Published: January 2020

An assay based on reverse transcription and nested PCR amplification of hypervariable regions within the 16S rRNA sequence was used to specifically detect Renibacterium salmoninarum, the slowly growing causative agent of bacterial kidney disease in salmonid fish. This assay detected 1 to 10 bacteria per sample and took 1 to 2 days to perform. The assay was used to detect R. salmoninarum in ovarian fluid obtained from naturally infected fish. The assay was unreliable when it was used to examine kidney tissue.
Detection of β-Glucosidase Activity in Polyacrylamide Gels with Esculin as Substrate
Authors: Kwon Ki-Sun , Lee Jaehoon , Kang Hyung Gyoo , Hah Yung Chil
Published: January 2020

β-Glucosidase can be located after nondenaturing polyacrylamide gel electrophoresis by incubating the gel with 0.1% esculin and 0.03% ferric chloride. The esculetin released from esculin by β-glucosidase action reacts with ferric ion to produce a black band, corresponding to the β-glucosidase, against the transparent background.
Incidence of Listeria spp. and Listeria monocytogenes in a poultry processing environment and in poultry products and their rapid confirmation by multiplex PCR
Authors: Lawrence L M , Gilmour A
Published: January 2020

The incidence of Listeria spp. and Listeria monocytogenes in a poultry processing plant and in raw and cooked poultry products was determined over a 6-month period. Within the raw and cooked poultry processing environments, 46% (36 of 79) and 29% (51 of 173) of the samples contained Listeria spp. while 26% (21 of 79) and 15% (27 of 173) contained L. monocytogenes, respectively. Various sites within the processing environment were found to be consistently positive for L. monocytogenes throughout the entire sampling period. Of the raw and cooked products tested, 91% (53 of 58) and 8% (8 of 96) were found to contain Listeria spp. while 59% (34 of 58) and 0% (0 of 96) contained L. monocytogenes, respectively. Although L. monocytogenes was not detected in the cooked products examined, the presence of other Listeria spp. highlights the potential which exists for postprocessing contamination. Multiplex PCR proved to be a convenient and time-saving technique for rapid confirmation of Listeria spp. and L. monocytogenes in a single reaction.
Identification and analysis of the antigens detected by two commercial Bacillus cereus diarrheal enterotoxin immunoassay kits
Authors: Beecher D J , Wong A C
Published: January 2020

The usefulness of two commercial immunoassays for the detection of diarrheal enterotoxin of Bacillus cereus is unclear because the identity of the enterotoxin(s) has not been proven and the kits detect different proteins. We found that the Bacillus cereus Enterotoxin-Reversed Passive Latex Agglutination kit (Oxoid) detects the L2 component from hemolysin BL, and the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (Tecra) detects two apparently nontoxic proteins.
Purification and some properties of a xylanase from Aspergillus sydowii MG49
Authors: Ghosh M , Nanda G
Published: January 2020

Aspergillus sydowii MG49 produces a 30-kDa exosplitting xylobiohydrolase during growth on xylan. A specific chemical modification and substrate protection analysis of purified xylanase provided evidence that tryptophan and carboxy and amino groups are present at the catalytic site of this enzyme. Thermal inactivation of the xylanase occurs because of irreversible polymolecular aggregation, which is slower in the presence of glycerol.
Comparative sensitivity of the echovirus type 25 JV-4 prototype strain and two recent isolates to glutaraldehyde at low concentrations
Authors: Chambon M , Bailly J L , Peigue-Lafeuille H
Published: January 2020

The sensitivity of two recently isolated antigenic variants of echovirus type 25 (Montpellier 76-1262 and Thionville 86-222) to glutaraldehyde (GTA) at low concentrations was compared with that of the JV-4 prototype strain. The purified viruses were treated under the same conditions with GTA at concentrations ranging from 0.002 to 0.10%. The wild strains exhibited significantly lower sensitivity to GTA than did the prototype strain; with 0.10% GTA, a 2 log10 unit reduction was obtained in 5 min for JV-4 and in 60 and 80 min for Montpellier 76-1262 and Thionville 86-222, respectively. A comparison with previous results obtained with poliovirus type 1 showed that the inactivation rates of echovirus type 25 wild strains were fivefold lower than those of the poliovirus type 1 Sabin strain. The comparative electrophoretic and immunoblot analyses showed differences in the results of GTA binding with capsid proteins of the viruses. Unlike in the poliovirus type 1 Mahoney strain and in the echovirus type 25 JV-4 reference strain, GTA produced only minor intermolecular cross-linkings in the viral particles of the two wild strains of echovirus type 25. Our results suggest that there are both intertypic and intratypic differences in the GTA sensitivities of enterovirus strains. They are of relevance to disinfection procedures in digestive endoscopy and to the choice of the enterovirus strain used for evaluating the efficacy of disinfectants.
Lignin Peroxidase Oxidation of Aromatic Compounds in Systems Containing Organic Solvents
Authors: Vazquez-Duhalt Rafael , Westlake Donald W. S. , Fedorak Phillip M.
Published: January 2020

Lignin peroxidase from
Phanerochaete chrysosporium
was used to study the oxidation of aromatic compounds, including polycyclic aromatic hydrocarbons and heterocyclic compounds, that are models of moieties of asphaltene molecules. The oxidations were done in systems containing water-miscible organic solvents, including methanol, isopropanol,
N, N
-dimethylformamide, acetonitrile, and tetrahydrofuran. Of the 20 aromatic compounds tested, 9 were oxidized by lignin peroxidase in the presence of hydrogen peroxide. These included anthracene, 1-, 2-, and 9-methylanthracenes, acenaphthene, fluoranthene, pyrene, carbazole, and dibenzothiophene. Of the compounds studied, lignin peroxidase was able to oxidize those with ionization potentials of <8 eV (measured by electron impact). The reaction products contain hydroxyl and keto groups. In one case, carbon-carbon bond cleavage, yielding anthraquinone from 9-methylanthracene, was detected. Kinetic constants and stability characteristics of lignin peroxidase were determined by using pyrene as the substrate in systems containing different amounts of organic solvent. Benzyl alkylation of lignin peroxidase improved its activity in a system containing water-miscible organic solvent but did not increase its resistance to inactivation at high solvent concentrations.
Carbon isotope effects associated with aceticlastic methanogenesis
Authors: Gelwicks J T , Risatti J B , Hayes J M
Published: January 2020

The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems.
Physiological Aspects of Biosynthesis of Lignin Peroxidases by
Phanerochaete chrysosporium
Authors: Leštan Domen , Leštan Marjeta , Perdih Anton
Published: January 2020

Methods based on UV-visible diffuse reflectance spectroscopy were used to study the physiological aspects of lignin-peroxidase biosynthesis by
Phanerochaete chrysosporium.
Here we introduce the use of cytochrome
aa
3
as an indicator of active fungal biomass and of its redox state to calculate the oxygen mass transport coefficient between the growth medium and the fungal cell interior. When lignin peroxidase biosynthesis was enhanced by the addition of Tween 80 or Tween 20 to the growth medium, a higher proportion of reduced cytochrome
aa
3
and a higher oxygen diffusion barrier were observed compared with control cultures. In cultures supplemented with Tween 80 or Tween 20, a higher oxygen mass transport coefficient between the growth medium and the interior of the fungal cell was also found. The beginning of the lignin peroxidase activity in these cultures was found to coincide with a temporary cessation in the dry biomass increase and a reduction in the relative active-biomass concentration. During the lignin peroxidase activity, a decrease in the intracellular pH and an increase in the growth medium pH were determined in cultures supplemented with Tween 80.