bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Apple Cultivars on Inactivation of Different Strains of
Escherichia coli
O157:H7 in Apple Cider by UV Irradiation
Authors: Basaran N. , Quintero-Ramos A. , Moake M. M. , Churey J. J. , Worobo R. W. 
Published: October 2004

ABSTRACT

This study examined the effect of different apple cultivars upon the UV inactivation of
Escherichia coli
O157:H7 strains within unfiltered apple cider. Apple cider was prepared from eight different apple cultivars, inoculated with approximately 10
6
to 10
7
CFU of three strains of
E. coli
O157:H7 per ml (933, ATCC 43889, and ATCC 43895), and exposed to 14 mJ of UV irradiation per cm
2
. Bacterial populations for treated and untreated samples were then enumerated by using nonselective media.
E. coli
O157:H7 ATCC 43889 showed the most sensitivity to this disinfection process with an average 6.63-log reduction compared to an average log reduction of 5.93 for both strains 933 and ATCC 43895. The highest log reduction seen, 7.19, occurred for strain ATCC 43889 in Rome cider. The same cider produced the lowest log reductions: 5.33 and 5.25 for strains 933 and ATCC 43895, respectively. Among the apple cultivars, an average log reduction range of 5.78 (Red Delicious) to 6.74 (Empire) was observed, with two statistically significant (α ≤ 0.05) log reduction groups represented. Within the paired cultivar-strain analysis, five of eight ciders showed statistically significant (α ≤ 0.05) differences in at least two of the
E. coli
strains used. Comparison of log reductions among the
E. coli
strains to the cider parameters of °Brix, pH, and malic acid content failed to show any statistically significant relationship (
R
2
≥ 0.95). However, the results of this study indicate that regardless of the apple cultivar used, a minimum 5-log reduction is achieved for all of the strains of
E. coli
O157:H7 tested.
Novel Cassette-Based Shuttle Vector System for Gram-Positive Bacteria
Authors: Charpentier Emmanuelle , Anton Ana I. , Barry Peter , Alfonso Berenice , Fang Yuan , Novick Richard P. 
Published: October 2004

ABSTRACT

Our understanding of staphylococcal pathogenesis depends on reliable genetic tools for gene expression analysis and tracing of bacteria. Here, we have developed and evaluated a series of novel versatile
Escherichia coli
-staphylococcal shuttle vectors based on PCR-generated interchangeable cassettes. Advantages of our module system include the use of (i) staphylococcal low-copy-number, high-copy-number, thermosensitive and theta replicons and selectable markers (choice of erythromycin, tetracycline, chloramphenicol, kanamycin, or spectinomycin); (ii) an
E. coli
replicon and selectable marker (ampicillin); and (iii) a staphylococcal phage fragment that allows high-frequency transduction and an SaPI fragment that allows site-specific integration into the
Staphylococcus aureus
chromosome. The staphylococcal cadmium-inducible P

cad

-cadC
and constitutive P

blaZ

promoters were designed and analyzed in transcriptional fusions to the staphylococcal β-lactamase
blaZ
, the
Vibrio fischeri luxAB
, and the
Aequorea victoria
green fluorescent protein reporter genes. The modular design of the vector system provides great flexibility and variety. Questions about gene dosage, complementation, and
cis-trans
effects can now be conveniently addressed, so that this system constitutes an effective tool for studying gene regulation of staphylococci in various ecosystems.
Transcriptional Analysis of Biofilm Formation Processes in the Anaerobic, Hyperthermophilic BacteriumThermotoga maritima
Authors: Pysz Marybeth A. , Conners Shannon B. , Montero Clemente I. , Shockley Keith R. , Johnson Matthew R. , Ward Donald E. , Kelly Robert M. 
Published: October 2004

ABSTRACTThermotoga maritima, a fermentative, anaerobic, hyperthermophilic bacterium, was found to attach to bioreactor glass walls, nylon mesh, and polycarbonate filters during chemostat cultivation on maltose-based media at 80°C. A whole-genome cDNA microarray was used to examine differential expression patterns between biofilm and planktonic populations. Mixed-model statistical analysis revealed differential expression (twofold or more) of 114 open reading frames in sessile cells (6% of the genome), over a third of which were initially annotated as hypothetical proteins in theT. maritimagenome. Among the previously annotated genes in theT. maritimagenome, which showed expression changes during biofilm growth, were several that corresponded to biofilm formation genes identified in mesophilic bacteria (i.e.,Pseudomonasspecies,Escherichia coli, andStaphylococcus epidermidis). Most notably,T. maritimabiofilm-bound cells exhibited increased transcription of genes involved in iron and sulfur transport, as well as in biosynthesis of cysteine, thiamine, NAD, and isoprenoid side chains of quinones. These findings were all consistent with the up-regulation of iron-sulfur cluster assembly and repair functions in biofilm cells. Significant up-regulation of several β-specific glycosidases was also noted in biofilm cells, despite the fact that maltose was the primary carbon source fed to the chemostat. The reasons for increased β-glycosidase levels are unclear but are likely related to the processing of biofilm-based polysaccharides. In addition to revealing insights into the phenotype of sessileT. maritimacommunities, the methodology developed here can be extended to study other anaerobic biofilm formation processes as well as to examine aspects of microbial ecology in hydrothermal environments.
Helix 4 Mutants of the
Bacillus thuringiensis
Insecticidal Toxin Cry1Aa Display Altered Pore-Forming Abilities
Authors: Vachon Vincent , Préfontaine Gabrielle , Rang Cécile , Coux Florence , Juteau Marc , Schwartz Jean-Louis , Brousseau Roland , Frutos Roger , Laprade Raynald , Masson Luke 
Published: October 2004

ABSTRACT

The role played by α-helix 4 of the
Bacillus thuringiensis
toxin Cry1Aa in pore formation was investigated by individually replacing each of its charged residues with either a neutral or an oppositely charged amino acid by using site-directed mutagenesis. The majority of the resulting mutant proteins were considerably less toxic to
Manduca sexta
larvae than Cry1Aa. Most mutants also had a considerably reduced ability to form pores in midgut brush border membrane vesicles isolated from this insect, with the notable exception of those with alterations at amino acid position 127 (R127N and R127E), located near the N-terminal end of the helix. Introducing a negatively charged amino acid near the C-terminal end of the helix (T142D and T143D), a region normally devoid of charged residues, completely abolished pore formation. For each mutant that retained detectable pore-forming activity, reduced membrane permeability to KCl was accompanied by an approximately equivalent reduction in permeability to
N
-methyl-
d
-glucamine hydrochloride, potassium gluconate, sucrose, and raffinose and by a reduced rate of pore formation. These results indicate that the main effect of the mutations was to decrease the toxin's ability to form pores. They provide further evidence that α-helix 4 plays a crucial role in the mechanism of pore formation.
Detection of Low Levels of
Listeria monocytogenes
Cells by Using a Fiber-Optic Immunosensor
Authors: Geng Tao , Morgan Mark T. , Bhunia Arun K. 
Published: October 2004

ABSTRACT

Biosensor technology has a great potential to meet the need for sensitive and nearly real-time microbial detection from foods. An antibody-based fiber-optic biosensor to detect low levels of
Listeria monocytogenes
cells following an enrichment step was developed. The principle of the sensor is a sandwich immunoassay where a rabbit polyclonal antibody was first immobilized on polystyrene fiber waveguides through a biotin-streptavidin reaction to capture
Listeria
cells on the fiber. Capture of cells on the fibers was confirmed by scanning electron microscopy. A cyanine 5-labeled murine monoclonal antibody, C11E9, was used to generate a specific fluorescent signal, which was acquired by launching a 635-nm laser light from an Analyte 2000 and collected by a photodetector at 670 to 710 nm. This immunosensor was specific for
L. monocytogenes
and showed a significantly higher signal strength than for other
Listeria
species or other microorganisms, including
Escherichia coli
,
Enterococcus faecalis
,
Salmonella enterica
,
Lactobacillus plantarum
,
Carnobacterium gallinarum
,
Hafnia alvei
,
Corynebacterium glutamicum
,
Enterobacter aerogenes
,
Pseudomonas aeruginosa
, and
Serratia marcescens
, in pure or in mixed-culture setup. Fiber-optic results could be obtained within 2.5 h of sampling. The sensitivity threshold was about 4.3 × 10
3
CFU/ml for a pure culture of
L. monocytogenes
grown at 37°C. When
L. monocytogenes
was mixed with lactic acid bacteria or grown at 10°C with 3.5% NaCl, the detection threshold was 4.1 × 10
4
or 2.8 × 10
7
CFU/ml, respectively. In less than 24 h, this method could detect
L. monocytogenes
in hot dog or bologna naturally contaminated or artificially inoculated with 10 to 1,000 CFU/g after enrichment in buffered
Listeria
enrichment broth.
Quorum Quenching: Enzymatic Disruption ofN-Acylhomoserine Lactone-Mediated Bacterial Communication inBurkholderia thailandensis
Authors: Ulrich Ricky L. 
Published: October 2004

ABSTRACTMany species of gram-negative bacteria communicate by synthesizing, secreting, and responding toN-acylhomoserine lactones (AHLs), a mechanism termed quorum sensing. Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates ofBacillusspp. TheBurkholderia thailandensisquorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins. Expression of theBacillus anthracis(Ames strain) AiiA lactonase inB. thailandensiscompletely abolished the accumulation ofN-decanoylhomoserine lactone (C10-HSL) andN-octanoylhomoserine lactone (C8-HSL), reducedN-hexanoylhomoserine lactone (C6-HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism. In contrast, heterologous expression of theBacillus cereusstrain A24 AiiA lactonase inB. thailandensisreduced the concentrations of C6-HSL, C8-HSL, and C10-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization. Individual disruption of theB. thailandensisAHSs, specifically disruption of thebtaI1andbtaI3genes, which encode the proteins that direct the synthesis of C8-HSL and C6-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage inB. thailandensisby theBacillusAiiA lactonases failed to enhance beta-hemolytic activity. The results of this study demonstrate that heterologous expression ofBacillussp. AiiA lactonases inB. thailandensisreduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the beta-hemolysis of sheep erythrocytes.
Persistence of
Streptococcus mutans
in Stationary-Phase Batch Cultures and Biofilms
Authors: Renye John A. , Piggot Patrick J. , Daneo-Moore Lolita , Buttaro Bettina A. 
Published: October 2004

ABSTRACT

Streptococcus mutans
is a member of oral plaque biofilms and is considered the major etiological agent of dental caries. We have characterized the survival of
S. mutans
strain UA159 in both batch cultures and biofilms. Bacteria grown in batch cultures in a chemically defined medium, FMC, containing an excess of glucose or sucrose caused the pH to decrease to 4.0 at the entry into stationary phase, and they survived for about 3 days. Survival was extended up to 11 days when the medium contained a limiting concentration of glucose or sucrose that was depleted by the time the bacteria reached stationary phase. Sugar-limited cultures maintained a pH of 7.0 throughout stationary phase. Their survival was shortened to 3 days by the addition of exogenous lactic acid at the entry into stationary phase. Sugar starvation did not lead to comparable survival in biofilms. Although the pH remained at 7.0, bacteria could no longer be cultured from biofilms 4 days after the imposition of glucose or sucrose starvation;
Bac
Light staining results did not agree with survival results based on culturability. In both batch cultures and biofilms, survival could be extended by the addition of 0.5% mucin to the medium. Batch survival increased to an average of 26 (±8) days, and an average of 2.7 × 10
5
CFU per chamber were still present in biofilms that were starved of sucrose for 12 days.
Stratified Growth in
Pseudomonas aeruginosa
Biofilms
Authors: Werner Erin , Roe Frank , Bugnicourt Amandine , Franklin Michael J. , Heydorn Arne , Molin Søren , Pitts Betsey , Stewart Philip S. 
Published: October 2004

ABSTRACT

In this study, stratified patterns of protein synthesis and growth were demonstrated in
Pseudomonas aeruginosa
biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct carried an isopropyl-β-
d
-thiogalactopyranoside (IPTG)-inducible
gfpmut2
gene encoding a stable GFP. The second construct carried a GFP derivative,
gfp
-AGA, encoding an unstable GFP under the control of the growth-rate-dependent
rrnBp
1
promoter. Both GFP reporters indicated that active protein synthesis was restricted to a narrow band in the part of the biofilm adjacent to the source of oxygen. The zone of active GFP expression was approximately 60 μm wide in colony biofilms and 30 μm wide in flow cell biofilms. The region of the biofilm in which cells were capable of elongation was mapped by treating colony biofilms with carbenicillin, which blocks cell division, and then measuring individual cell lengths by transmission electron microscopy. Cell elongation was localized at the air interface of the biofilm. The heterogeneous anabolic patterns measured inside these biofilms were likely a result of oxygen limitation in the biofilm. Oxygen microelectrode measurements showed that oxygen only penetrated approximately 50 μm into the biofilm.
P. aeruginosa
was incapable of anaerobic growth in the medium used for this investigation. These results show that while mature
P. aeruginosa
biofilms contain active, growing cells, they can also harbor large numbers of cells that are inactive and not growing.
Spatiotemporal Distribution of Marine Magnetotactic Bacteria in a Seasonally Stratified Coastal Salt Pond
Authors: Simmons S. L. , Sievert S. M. , Frankel R. B. , Bazylinski D. A. , Edwards K. J. 
Published: October 2004

ABSTRACT

The occurrence and distribution of magnetotactic bacteria (MB) were studied as a function of the physical and chemical conditions in meromictic Salt Pond, Falmouth, Mass., throughout summer 2002. Three dominant MB morphotypes were observed to occur within the chemocline. Small microaerophilic magnetite-producing cocci were present at the top of the chemocline, while a greigite-producing packet-forming bacterium occurred at the base of the chemocline. The distributions of these groups displayed sharp changes in abundance over small length scales within the water column as well as strong seasonal fluctuations in population abundance. We identified a novel, greigite-producing rod in the sulfidic hypolimnion that was present in relatively constant abundance over the course of the season. This rod is the first MB that appears to belong to the γ-
Proteobacteria
, which may suggest an iron- rather than sulfur-based respiratory metabolism. Its distribution and phylogenetic identity suggest that an alternative model for the ecological and physiological role of magnetotaxis is needed for greigite-producing MB.
Comparative Analysis of Physical Maps of FourBacillus subtilis(natto) Genomes
Authors: Qiu Dongru , Fujita Kyoko , Sakuma Yuko , Tanaka Teruo , Ohashi Yoshiaki , Ohshima Hideyuki , Tomita Masaru , Itaya Mitsuhiro 
Published: October 2004

ABSTRACTThe complete SfiI and I-CeuI physical maps of fourBacillus subtilis(natto) strains, which were previously isolated as natto (fermented soybean) starters, were constructed to elucidate the genome structure. Not only the similarity in genome size and organization but also the microheterogeneity of the gene context was revealed. No large-scale genome rearrangements among the four strains were indicated by mapping of the genes, including 10 rRNA operons (rrn) and relevant genes required for natto production, to the loci corresponding to those of theB. subtilisstrain Marburg 168. However, restriction fragment length polymorphism and the presence or absence of strain-specific DNA sequences, such as the prophages SPβ,skinelement, and PBSX, as well as the insertion element IS4Bsu1, could be used to identify one of these strains as a Marburg type and the other three strains as natto types. The genome structure and gene heterogeneity were also consistent with the type of indigenous plasmids harbored by the strains.
Family Shuffling of Expandase Genes To Enhance Substrate Specificity for Penicillin G
Authors: Hsu Jyh-Shing , Yang Yunn-Bor , Deng Chan-Hui , Wei Chia-Li , Liaw Shwu-Huey , Tsai Ying-Chieh 
Published: October 2004

ABSTRACT

Deacetoxycephalosporin C synthase (expandase) from
Streptomyces clavuligerus
, encoded by
cefE
, is an important industrial enzyme for the production of 7-aminodeacetoxycephalosporanic acid from penicillin G. To improve the substrate specificity for penicillin G, eight
cefE
-homologous genes were directly evolved by using the DNA shuffling technique. After the first round of shuffling and screening, using an
Escherichia coli
ESS bioassay, four chimeras with higher activity were subjected to a second round. Subsequently, 20 clones were found with significantly enhanced activity. The kinetic parameters of two isolates that lack substrate inhibition showed 8.5- and 118-fold increases in the
k
cat
/

K
m

ratio compared to the
S. clavuligerus
expandase. The evolved enzyme with the 118-fold increase is the most active obtained to date anywhere. Our shuffling results also indicate the remarkable plasticity of the expandase, suggesting that more-active chimeras might be achievable with further rounds.
Abundance of Reverse Tricarboxylic Acid Cycle Genes in Free-Living Microorganisms at Deep-Sea Hydrothermal Vents
Authors: Campbell Barbara J. , Cary S. Craig 
Published: October 2004

ABSTRACT

Since the discovery of hydrothermal vents more than 25 years ago, the Calvin-Bassham-Benson (Calvin) cycle has been considered the principal carbon fixation pathway in this microbe-based ecosystem. However, on the basis of recent molecular data of cultured free-living and noncultured episymbiotic members of the epsilon subdivision of
Proteobacteria
and earlier carbon isotope data of primary consumers, an alternative autotrophic pathway may predominate. Here, genetic and culture-based approaches demonstrated the abundance of reverse tricarboxylic acid cycle genes compared to the abundance of Calvin cycle genes in microbial communities from two geographically distinct deep-sea hydrothermal vents. PCR with degenerate primers for three key genes in the reverse tricarboxylic acid cycle and form I and form II of ribulose 1,5-bisphosphate carboxylase/oxygenase (Calvin cycle marker gene) were utilized to demonstrate the abundance of the reverse tricarboxylic acid cycle genes in diverse vent samples. These genes were also expressed in at least one chimney sample. Diversity, similarity matrix, and phylogenetic analyses of cloned samples and amplified gene products from autotrophic enrichment cultures suggest that the majority of autotrophs that utilize the reverse tricarboxylic acid cycle are members of the epsilon subdivision of
Proteobacteria
. These results parallel the results of previously published molecular surveys of 16S rRNA genes, demonstrating the dominance of members of the epsilon subdivision of
Proteobacteria
in free-living hydrothermal vent communities. Members of the epsilon subdivision of
Proteobacteria
are also ubiquitous in many other microaerophilic to anaerobic sulfidic environments, such as the deep subsurface. Therefore, the reverse tricarboxylic acid cycle may be a major autotrophic pathway in these environments and significantly contribute to global autotrophic processes.
Molecular Characterization of Two Lactate Dehydrogenase Genes with a Novel Structural Organization on the Genome of
Lactobacillus
sp. Strain MONT4
Authors: Weekes Jennifer , Yüksel Gülhan Ü. 
Published: October 2004

ABSTRACT

Two lactate dehydrogenase (
ldh
) genes from
Lactobacillu
s sp. strain MONT4 were cloned by complementation in
Escherichia coli
DC1368 (
ldh pfl
) and were sequenced. The sequence analysis revealed a novel genomic organization of the
ldh
genes. Subcloning of the individual
ldh
genes and their Northern blot analyses indicated that the genes are monocistronic.
Aquatic Snails, Passive Hosts of
Mycobacterium ulcerans
Authors: Marsollier Laurent , Sévérin Tchibozo , Aubry Jacques , Merritt Richard W. , Saint André Jean-Paul , Legras Pierre , Manceau Anne-Lise , Chauty Annick , Carbonnelle Bernard , Cole Stewart T. 
Published: October 2004

ABSTRACT

Accumulative indirect evidence of the epidemiology of
Mycobacterium ulcerans
infections causing chronic skin ulcers (i.e., Buruli ulcer disease) suggests that the development of this pathogen and its transmission to humans are related predominantly to aquatic environments. We report that snails could transitorily harbor
M. ulcerans
without offering favorable conditions for its growth and replication. A novel intermediate link in the transmission chain of
M. ulcerans
becomes likely with predator aquatic insects in addition to phytophage insects. Water bugs, such as
Naucoris cimicoides
, a potential vector of
M. ulcerans,
were shown to be infected specifically by this bacterium after feeding on snails experimentally exposed to
M. ulcerans
.
Rapid Quantitative Detection of
Listeria monocytogenes
in Meat Products by Real-Time PCR
Authors: Rodríguez-Lázaro David , Jofré Anna , Aymerich Teresa , Hugas Marta , Pla Maria 
Published: October 2004

ABSTRACT

We describe a quick and simple method for the quantitative detection of
Listeria monocytogenes
in meat products. This method is based on filtration, Chelex-100-based DNA purification, and real-time PCR. It can detect as few as 100 CFU/g and quantify as few as 1,000 CFU/g, with excellent accuracy compared to that of the plate count method. Therefore, it is a promising alternative for the detection of
L. monocytogenes
in meat products.
Role of Hippoboscidae Flies as Potential Vectors of
Bartonella
spp. Infecting Wild and Domestic Ruminants
Authors: Halos Lénaïg , Jamal Taoufik , Maillard Renaud , Girard Benjamin , Guillot Jacques , Chomel Bruno , Vayssier-Taussat Muriel , Boulouis Henri-Jean 
Published: October 2004

ABSTRACT

The putative role of biting flies in
Bartonella
transmission among ruminants was investigated. Amplification of the
Bartonella
citrate synthase gene from 83 Hippoboscidae was detected in 94% of 48 adult
Lipoptena cervi
flies, 71% of 17 adult
Hippobosca equina
flies, 100% of 20 adult
Melophagus ovinus
flies, and 100% of 10
M. ovinus
pupae. Our findings suggest that Hippoboscidae play a role in the transmission of
Bartonella
among ruminants. The vertical transmission of
Bartonella
in
M. ovinus
and the presence of
Bartonella
DNA in all samples suggest a symbiotic association between
Bartonella
and
M. ovinus
.
Metabolism of 2-Mercaptobenzothiazole by
Rhodococcus rhodochrous
Authors: Haroune Nicolas , Combourieu Bruno , Besse Pascale , Sancelme Martine , Kloepfer Achim , Reemtsma Thorsten , De Wever Heleen , Delort Anne-Marie 
Published: October 2004

ABSTRACT

2-Mercaptobenzothiazole, which is mainly used in the rubber industry as a vulcanization accelerator, is very toxic and is considered to be recalcitrant. We show here for the first time that it can be biotransformed and partially mineralized by a pure-culture bacterial strain of
Rhodococcus rhodochrous
. Three metabolites, among four detected, were identified.