bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of Infectious Enteroviruses, Enterovirus Genomes, Somatic Coliphages, and
Bacteroides fragilis
Phages in Treated Wastewater
Authors: Gantzer C. , Maul A. , Audic J. M. , Schwartzbrod L. 
Published: December 2019

ABSTRACT

In this study, three types of treated wastewater were tested for infectious enteroviruses, the enterovirus genome, somatic coliphages, and
Bacteroides fragilis
phages. The aim of this work was to determine whether the presence of the two types of bacteriophages or of the enterovirus genome was a good indicator of infectious enterovirus contamination. The enterovirus genome was detected by reverse transcription-polymerase chain reaction. Infectious enteroviruses were quantified by cell culturing (BGM cells), and the bacteriophages were quantified by plaque formation on the host bacterium (
Escherichia coli
or
B. fragilis
) in agar medium. Forty-eight samples of treated wastewater were analyzed. Sixteen samples had been subjected to a secondary treatment for 8 to 12 h (A), 16 had been subjected to a secondary treatment for 30 h (B1), and 16 had been subjected to both secondary and tertiary treatments (B2). The mean concentrations of somatic coliphages were 4.9 × 10
4
PFU · liter
−1
for treatment line A, 9.8 × 10
3
PFU · liter
−1
for B1, and 1.4 × 10
3
PFU · liter
−1
for B2, with all the samples testing positive (100%). The mean concentrations of
B. fragilis
phages were 1.7 × 10
3
PFU · liter
−1
for A (100% positive samples), 17 to 24 PFU · liter
−1
for B1 (44% positive samples), and 0.8 to 13 PFU · liter
−1
for B2 (6% positive samples). The mean concentrations of infectious enteroviruses were 4 most probable number of cytopathogenic units (MPNCU) · liter
−1
for A (31% positive samples) and <1 MPNCU · liter
−1
for B1 and B2 (0% positive samples). The percentages of samples testing positive for the enterovirus genome were 100% for A, 56% for B1, and 19% for B2. The percentages of samples testing positive for the enterovirus genome were significantly higher than those for infectious enteroviruses. This finding may have been due to the presence of noninfectious enteroviruses or to the presence of infectious enteroviruses that do not multiply in BGM cell cultures. However, under our experimental conditions, nondetection of the genome implies the absence of infectious viruses. There was a significant correlation between the concentration of somatic coliphages or
B. fragilis
phages and the presence of infectious enteroviruses or the presence of the enterovirus genome. However, the somatic coliphage concentration did not lead to fluctuations in the infectious enterovirus concentration, whereas the
B. fragilis
phage concentration did.
Identification and Quantification of Toxic Chemicals by Use of
Escherichia coli
Carrying
lux
Genes Fused to Stress Promoters
Authors: Ben-Israel Oren , Ben-Israel Haggit , Ulitzur Shimon 
Published: December 2019

ABSTRACT

The
luxCDABE
bioluminescence genes of the
Vibrio fischeri lux
system have been used as a reporter system for different stress and regulatory promoters of
Escherichia coli
. Selected
E. coli
strains carrying
lux
genes fused to different promoters were exposed to various toxic chemicals, and the recorded luminescence was used for the characterization of the biologic signature of each compound. Analysis of these data with the aid of a proper algorithm allowed quantitative and qualitative assessment of toxic chemicals. Of the 25 tested chemicals, 23 were identified by this novel strategy in a 3-h procedure. This system can also be adapted for the identification of simple mixtures of toxic agents when the biologic signatures of the individual compounds are known. This biologic recognition strategy also provides a tool for evaluating the degree of similarity between the modes of action of different toxic agents.
Cyt1Aa Protein of
Bacillus thuringiensis
Is Toxic to the Cottonwood Leaf Beetle,
Chrysomela scripta
, and Suppresses High Levels of Resistance to Cry3Aa
Authors: Federici Brian A. , Bauer Leah S. 
Published: December 2019

ABSTRACT

The insecticidal activity of
Bacillus thuringiensis
is due primarily to Cry and Cyt proteins. Cry proteins are typically toxic to lepidopterous, coleopterous, or dipterous insects, whereas the known toxicity of Cyt proteins is limited to dipterans. We report here that a Cyt protein, Cyt1Aa, is also highly toxic to the cottonwood leaf beetle,
Chrysomela scripta
, with a median lethal concentration of 2.5 ng/mm
2
of leaf surface for second-instar larvae. Additionally, we show that Cyt1Aa suppresses resistance to Cry3Aa greater than 5,000-fold in
C. scripta
, a level only partially overcome by Cry1Ba due to cross-resistance. Studies of the histopathology of
C. scripta
larvae treated with Cyt1Aa revealed disruption and sloughing of midgut epithelial cells, indicating that its mechanism of action against
C. scripta
is similar to that observed in mosquito and blackfly larvae. These novel properties suggest that Cyt proteins may have an even broader spectrum of activity against insects and, owing to their different mechanism of action in comparison to Cry proteins, might be useful in managing resistance to Cry3 and possibly other Cry toxins used in microbial insecticides and transgenic plants.
Implications of rRNA Operon Copy Number and Ribosome Content in the Marine Oligotrophic Ultramicrobacterium
Sphingomonas
sp. Strain RB2256
Authors: Fegatella Fitri , Lim Julianne , Kjelleberg Staffan , Cavicchioli Ricardo 
Published: December 2019

ABSTRACT

Sphingomonas
sp. strain RB2256 is a representative of the dominant class of ultramicrobacteria that are present in marine oligotrophic waters. In this study we examined the rRNA copy number and ribosome content of RB2256 to identify factors that may be associated with the relatively low rate of growth exhibited by the organism. It was found that RB2256 contains a single copy of the rRNA operon, in contrast to
Vibrio
spp., which contain more than eight copies. The maximum number of ribosomes per cell was observed during mid-log phase; however, this maximum content was low compared to those of faster-growing, heterotrophic bacteria (approximately 8% of the maximum ribosome content of
Escherichia coli
with a growth rate of 1.5 h
−1
). The low number of ribosomes per cell appears to correlate with the low rate of growth (0.16 to 0.18 h
−1
) and the presence of a single copy of the rRNA operon. However, on the basis of cell volume, RB2256 appears to have a higher concentration of ribosomes than
E. coli
(approximately double that of
E. coli
with a growth rate of 1.5 h
−1
). Ribosome numbers reached maximum levels during mid-log-phase growth but decreased rapidly to 10% of maximum during late log phase through 7 days of starvation. The cells in late log phase and at the onset of starvation displayed an immediate response to a sudden addition of excess glucose (3 mM). This result demonstrates that a ribosome content 10% of maximum is sufficient to allow cells to immediately respond to nutrient upshift and achieve maximum rates of growth. These data indicate that the bulk of the ribosome pool is not required for protein synthesis and that ribosomes are not the limiting factor contributing to a low rate of growth. Our findings show that the regulation of ribosome content, the number of ribosomes per cell, and growth rate responses in RB2256 are fundamentally different from those characteristics in fast-growing heterotrophs like
E. coli
and that they may be characteristics typical of oligotrophic ultramicrobacteria.
Influence of Pretreatment and Experimental Conditions on Electrophoretic Mobility and Hydrophobicity of
Cryptosporidium parvum
Oocysts
Authors: Brush Charles F. , Walter Michael F. , Anguish Lynne J. , Ghiorse William C. 
Published: December 2019

ABSTRACT

Surface properties of
Cryptosporidium parvum
oocysts were investigated by using electrophoretic mobility and hydrophobicity measurements. Oocysts purified from calf feces by several sucrose flotation steps and deionized water (DI) washes (DIS method) had an electrophoretic mobility (neutral surface charge) near 0.0 m
2
V
−1
s
−1
over a pH range of 2 to 10. The mean electrophoretic mobility of oocysts stored in DI containing a mixture of antibiotics had a lower standard deviation (ς = 0.36) than that of oocysts stored in DI without antibiotics (ς = 0.53); their electrophoretic mobility remained unchanged up to 121 days after collection. The electrophoretic mobility of oocysts purified on a cold Percoll-sucrose gradient after the feces was defatted with ethyl acetate (EAPS method) varied linearly with pH from 0.0 m
2
V
−1
s
−1
at pH 2.4 to −3.2 × 10
−8
m
2
V
−1
s
−1
at pH 10 (ς = 0.52), thus displaying the negative surface charge at neutral pH observed by other researchers. The hydrophobicity of oocysts and two types of polystyrene beads was measured as a function of ionic strength by adhesion to polystyrene. Oocysts were purified by the DIS method. The ionic strength of the suspending solution was varied from 0 to 95 mmol liter
−1
. Two-week-old oocysts exhibited strong adhesion (∼85%) at ionic strengths of 0 to 10 mmol liter
−1
and moderate adhesion (∼20%) at ionic strengths of 20 to 95 mmol liter
−1
. Two-month-old oocysts exhibited high adhesion (∼60 to 80%) at all ionic strengths. These results show that adhesion properties governed by the electrophoretic mobility of purified
C. parvum
oocysts can be altered by the method of purification and that hydrophobicity can change as oocysts age.
Sedimentation of Free and Attached
Cryptosporidium
Oocysts and
Giardia
Cysts in Water
Authors: Medema G. J. , Schets F. M. , Teunis P. F. M. , Havelaar A. H. 
Published: December 2019

ABSTRACT

Experimental analysis of the sedimentation velocity of
Cryptosporidium parvum
oocysts and
Giardia lamblia
cysts was compared with mathematical description of their sedimentation velocities by using measurements of (oo)cyst size and density and the density and viscosity of the sedimentation medium to determine if the sedimentation kinetics of freely suspended oocysts of
C. parvum
and cysts of
G. lamblia
can be described by Stokes’ law. The theoretically calculated sedimentation kinetics showed a good agreement with the experimentally observed kinetics. Both showed a decline in sedimentation velocity over time, caused primarily by variation in (oo)cyst density. The initial apparent sedimentation velocities in Hanks balanced salt solution at 23°C was 0.35 μm · s
−1
for oocysts and 1.4 μm · s
−1
for cysts. (Oo)cysts that enter the surface water environment by discharges of biologically treated sewage may be attached to sewage particles, and this will affect their sedimentation kinetics. Therefore, (oo)cysts were mixed with settled secondary effluent. (Oo)cysts readily attached to the (biological) particles in effluent; 30% of both cysts and oocysts attached during the first minutes of mixing, and this fraction increased to approximately 75% after 24 h. The sedimentation velocity of (oo)cysts attached to secondary effluent particles increased with particle size and was (already in the smallest size fraction [1 to 40 μm]) determined by the sedimentation kinetics of the effluent particles. The observed sedimentation velocities of freely suspended (oo)cysts are probably too low to cause significant sedimentation in surface water or reservoirs. However, since a significant proportion of both cysts and oocysts attached readily to organic biological particles in secondary effluent, sedimentation of attached (oo)cysts after discharge into surface water will probably be a significant factor in the environmental ecology of
C. parvum
and
G. lamblia
. Attachment to particles influences not only sedimentation of (oo)cysts in surface water but also their behavior in drinking water treatment processes.
Antifungal Metabolites (Monorden, Monocillin IV, and Cerebrosides) from
Humicola fuscoatra
Traaen NRRL 22980, a Mycoparasite of
Aspergillus flavus
Sclerotia
Authors: Wicklow Donald T. , Joshi Biren K. , Gamble William R. , Gloer James B. , Dowd Patrick F. 
Published: December 2019

ABSTRACT

The mycoparasite
Humicola fuscoatra
NRRL 22980 was isolated from a sclerotium of
Aspergillus flavus
that had been buried in a cornfield near Tifton, Ga. When grown on autoclaved rice, this fungus produced the antifungal metabolites monorden, monocillin IV, and a new monorden analog. Each metabolite produced a clear zone of inhibition surrounding paper assay disks on agar plates seeded with conidia of
A. flavus
. Monorden was twice as inhibitory to
A. flavus
mycelium extension (MIC > 28 μg/ml) as monocillin IV (MIC > 56 μg/ml). Cerebrosides C and D, metabolites known to potentiate the activity of cell wall-active antibiotics, were separated from the ethyl acetate extract but were not inhibitory to
A. flavus
when tested as pure compounds. This is the first report of natural products from
H. fuscoatra
.
Quantification of 16S rRNAs in Complex Bacterial Communities by Multiple Competitive Reverse Transcription-PCR in Temperature Gradient Gel Electrophoresis Fingerprints
Authors: Felske Andreas , Akkermans Antoon D. L. , De Vos Willem M. 
Published: December 2019

ABSTRACT
A novel approach was developed to quantify rRNA sequences in complex bacterial communities. The main bacterial 16S rRNAs in Drentse A grassland soils (The Netherlands) were amplified by reverse transcription (RT)-PCR with bacterium-specific primers and were separated by temperature gradient gel electrophoresis (TGGE). The primer pair used (primers U968-GC and L1401) was found to amplify with the same efficiency 16S rRNAs from bacterial cultures containing different taxa and cloned 16S ribosomal DNA amplicons from uncultured soil bacteria. The sequence-specific efficiency of amplification was determined by monitoring the amplification kinetics by kinetic PCR. The primer-specific amplification efficiency was assessed by competitive PCR and RT-PCR, and identical input amounts of different 16S rRNAs resulted in identical amplicon yields. The sequence-specific detection system used for competitive amplifications was TGGE, which also has been found to be suitable for simultaneous quantification of more than one sequence. We demonstrate that this approach can be applied to TGGE fingerprints of soil bacteria to estimate the ratios of the bacterial 16S rRNAs.
Genetic Characterization of
pepP
, Which Encodes an Aminopeptidase P Whose Deficiency Does Not Affect
Lactococcus lactis
Growth in Milk, Unlike Deficiency of the X-Prolyl Dipeptidyl Aminopeptidase
Authors: Matos J. , Nardi M. , Kumura H. , Monnet V. 
Published: December 2019

ABSTRACT

We sequenced the
pepP
gene of
Lactococcus lactis
, which encodes an aminopeptidase P (PepP), and demonstrated that the X-prolyl dipeptidyl aminopeptidase PepX plays a more important role than PepP in nitrogen nutrition. PepP shares homology with methionine aminopeptidases and could play a role in the maturation of nascent proteins.
Metal Toxicity Reduction in Naphthalene Biodegradation by Use of Metal-Chelating Adsorbents
Authors: Malakul Pomthong , Srinivasan Keeran R. , Wang Henry Y. 
Published: December 2019

ABSTRACT
A model system comprising microbial degradation of naphthalene in the presence of cadmium has been developed to evaluate metal toxicity associated with polyaromatic hydrocarbon biodegradation and its reduction by the use of unmodified and surfactant-modified clays in comparison with a commercially available chelating resin (Chelex 100; Bio-Rad). The toxicity of cadmium associated with naphthalene biodegradation was shown to be reduced significantly by using the modified-clay complex and Chelex resin, while unmodified clay has no significant impact on this reduction. The degree of metal toxicity reduction can be quantitatively related to the metal adsorption characteristics of these adsorbents, such as adsorption capacity and selectivity.
Response of
Salmonella choleraesuis
LT2 Spheroplasts and Permeabilized Cells to the Bacteriocin AS-48
Authors: Abriouel H. , Valdivia E. , Gálvez A. , Maqueda M. 
Published: December 2019

ABSTRACT

The bacteriocin AS-48 was not active against intact cells of
Salmonella choleraesuis
LT2 at neutral pH, but it was very effective on spheroplasts, suggesting that the outer membrane (OM) acts as a protective barrier. Cells sublethally injured by heat or treated with OM-permeabilizing agents (i.e., EDTA and Tris) became sensitive to AS-48. The combination of two or more treatments decreased the amount of AS-48 required for cell killing. The activity of AS-48 against heat-injured cells did not change significantly in the pH range of 4.0 to 8.0. AS-48 showed bactericidal activity against intact cells of
Salmonella
at pH 4.0. The potency of AS-48 increased greatly when the bacteriocin was dissolved at pH 9.0.
Effect of Low-Osmolality Nutrient Media on Growth and Culturability of
Campylobacter
Species
Authors: Reezal Abdul , McNeil Brian , Anderson John G. 
Published: December 2019

ABSTRACT

The growth and culturability of
Campylobacter jejuni
NCTC 11351 and other campylobacters were examined in media having different osmolalities at a range of temperatures (4, 25, and 42°C). The medium osmolalities used ranged from the osmolality of full-strength nutrient medium (modified campylobacter broth having an osmolality of around 254 mosmol) down to 96 mosmol. The following two methods were used to produce media having different osmolalities: dilution of the nutrient medium with distilled water and reformulation of the medium such that the concentrations of various osmolytes were altered while the nutrient content of the medium was unchanged. The results obtained with the two experimental methods were similar, indicating that there was an osmotic threshold effect, such that none of the campylobacters examined (
C. jejuni
NCTC 11351 and ATCC 33291,
Campylobacter lari
, and
Campylobacter coli
) grew in media having osmolalities around 130 mosmol and at temperatures below at 42°C. Conversely, growth occurred in media having osmolalities of around 175 mosmol and above. Osmolar concentrations can be expressed in terms of osmolarity or osmolality. Osmolality is easier to evaluate, is the more commonly used term, and was used in the current study. In nutrient media having low osmolalities (i.e., 130 mosmol and below), the number of CFUs per milliliter declined rapidly regardless of the temperature, and no cells were recovered after 24 h. However, at nongrowth temperatures (25 and 4°C) in higher-osmolality media (175 mosmol and above) a significant population was recovered throughout the experiment (up to 96 h). In low-osmolality nutrient media, the cellular morphology was principally coccoid, while in the early stages of growth in full-strength media the morphology was predominantly rodlike. We propose that the formation of coccoid cells in these experiments was the result of osmotic stress in low-osmolality media. This osmotic effect was apparent regardless of the osmolyte used to reformulate the medium (NaCl, KCl, Na
2
SO
4
, NH
4
Cl, and glucose were used).
Use of
13
C Nuclear Magnetic Resonance and Gas Chromatography To Examine Methionine Catabolism by Lactococci
Authors: Gao Song , Mooberry Ed S. , Steele James L. 
Published: December 2019

ABSTRACT

Formation of methanethiol from methionine is widely believed to play a significant role in development of cheddar cheese flavor. However, the catabolism of methionine by cheese-related microorganisms has not been well characterized. Two independent methionine catabolic pathways are believed to be present in lactococci, one initiated by a lyase and the other initiated by an aminotransferase. To differentiate between these two pathways and to determine the possible distribution between the pathways,
13
C nuclear magnetic resonance (NMR) performed with uniformly enriched [
13
C]methionine was utilized. The catabolism of methionine by whole cells and cell extracts of five strains of
Lactococcus lactis
was examined. Only the aminotransferase-initiated pathway was observed. The intermediate and major end products were determined to be 4-methylthio-2-oxobutyric acid and 2-hydroxyl-4-methylthiobutyric acid, respectively. Production of methanethiol was not observed in any of the
13
C NMR studies. Gas chromatography was utilized to determine if the products of methionine catabolism in the aminotransferase pathway were precursors of methanethiol. The results suggest that the direct precursor of methanethiol is 4-methylthiol-2-oxobutyric acid. These results support the conclusion that an aminotransferase initiates the catabolism of methionine to methanethiol in lactococci.
An Ecological Study of Lactococci Isolated from Raw Milk in the Camembert Cheese Registered Designation of Origin Area
Authors: Corroler D. , Mangin I. , Desmasures N. , Gueguen M. 
Published: December 2019

ABSTRACT

The genetic diversity of lactococci isolated from raw milk in the Camembert cheese Registered Designation of Origin area was studied. Two seasonal samples (winter and summer) of raw milk were obtained from six farms in two areas (Bessin and Bocage Falaisien) of Normandy. All of the strains analyzed had a
Lactococcus lactis
subsp.
lactis
phenotype, whereas the randomly amplified polymorphic DNA (RAPD) technique genotypically identified the strains as members of
L. lactis
subsp.
lactis
or
L. lactis
subsp.
cremoris
. The genotypes were confirmed by performing standard PCR with primers corresponding to a region of the histidine biosynthesis operon. The geographic distribution of each subspecies of
L. lactis
was determined; 80% of the Bocage Falaisien strains were members of
L. lactis
subsp.
lactis
, and 30.5% of the Bessin strains were members of
L. lactis
subsp.
lactis
. A dendrogram was produced from a computer analysis of the RAPD profiles in order to evaluate the diversity of the lactococci below the subspecies level. The coefficient of similarity for 117 of the 139 strains identified as members of
L. lactis
subsp.
cremoris
was as high as 66%. The
L. lactis
subsp.
lactis
strains were more heterogeneous and formed 10 separate clusters (the level of similarity among the clusters was 18%). Reference strains of
L. lactis
subsp.
lactis
fell into 2 of these 10 clusters, demonstrating that lactococcal isolates are clearly different. As determined by the RAPD profiles, some
L. lactis
subsp.
lactis
strains were specific to the farms from which they originated and were recovered throughout the year (in both summer and winter). Therefore, the typicality of
L. lactis
subsp.
lactis
strains was linked to the farm of origin rather than the area. These findings emphasize the significance of designation of origin and the specificity of “Camembert de Normandie” cheese.
Cloning, Expression, and Chromosomal Stabilization of thePropionibacterium shermaniiProline Iminopeptidase Gene (pip) for Food-Grade Application inLactococcus lactis
Authors: Leenhouts Kees , Bolhuis Albert , Boot Johan , Deutz Inge , Toonen Marjolein , Venema Gerard , Kok Jan , Ledeboer Aat 
Published: December 2019

ABSTRACTProline iminopeptidase produced byPropionibacterium shermaniiplays an essential role in the flavor development of Swiss-type cheeses. The enzyme (Pip) was purified and characterized, and the gene (pip) was cloned and expressed inEscherichia coliandLactococcus lactis, the latter species being an extensively studied, primary cheese starter culture that is less fastidious in its growth condition requirements thanP. shermanii. The levels of expression of thepipgene could be enhanced with a factor 3 to 5 by using a strong constitutive promoter inL. lactisor the inducibletacpromoter inE. coli. Stable replication of the rolling-circle replicating (rcr) plasmid, used to expresspipinL. lactis, could only be obtained by providing therepAgene intrans. Upon the integration ofpip, clear gene dosage effects were observed and stable multicopy integrants could be maintained upon growth under the selective pressure of sucrose. The multicopy integrants demonstrated a high degree of stability in the presence of glucose. This study examines the possibilities to overexpress genes that play an important role in food fermentation processes and shows a variety of options to obtain stable food-grade expression of such genes inL. lactis.