bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Intestinal Microbiota and Response to Dietary Virginiamycin Supplementation in the Broiler Chicken
Authors: Dumonceaux Tim J. , Hill Janet E. , Hemmingsen Sean M. , Van Kessel Andrew G. 
Published: April 2006

ABSTRACTThe inclusion of antibiotic growth promoters, such as virginiamycin, at subtherapeutic levels in poultry feeds has a positive effect on health and growth characteristics, possibly due to beneficial effects on the host gastrointestinal microbiota. To improve our understanding of the chicken gastrointestinal microbiota and the effect of virginiamycin on its composition, we characterized the bacteria found in five different gastrointestinal tract locations (duodenal loop, mid-jejunum, proximal ileum, ileocecal junction, and cecum) in 47-day-old chickens that were fed diets excluding or including virginiamycin throughout the production cycle. Ten libraries (five gastrointestinal tract locations from two groups of birds) of approximately 555-bp chaperonin 60 PCR products were prepared, and 10,932 cloned sequences were analyzed. A total of 370 distinctcpn60sequences were identified, which ranged in frequency of recovery from 1 to 2,872. The small intestinal libraries were dominated by sequences from theLactobacillales(90% of sequences), while the cecum libraries were more diverse and included members of theClostridiales(68%),Lactobacillales(25%), andBacteroidetes(6%). To assess the effects of virginiamycin on the gastrointestinal microbiota, 15 bacterial targets were enumerated using quantitative, real-time PCR. Virginiamycin was associated with increased abundance of many of the targets in the proximal gastrointestinal tract (duodenal loop to proximal ileum), with fewer targets affected in the distal regions (ileocecal junction and cecum). These findings provide improved profiling of the composition of the chicken intestinal microbiota and indicate that microbial responses to virginiamycin are most significant in the proximal small intestine.
Characterization of Biofilm Formation by Clinically Relevant Serotypes of Group A Streptococci
Authors: Lembke Cordula , Podbielski Andreas , Hidalgo-Grass Carlos , Jonas Ludwig , Hanski Emanuel , Kreikemeyer Bernd 
Published: April 2006

ABSTRACT

Streptococcus pyogenes
(group A streptococcus [GAS]) is a frequent cause of purulent infections in humans. As potentially important aspects of its pathogenicity, GAS was recently shown to aggregate, form intratissue microcolonies, and potentially participate in multispecies biofilms. In this study, we show that GAS in fact forms monospecies biofilms in vitro, and we analyze the basic parameters of
S. pyogenes
in vitro biofilm formation, using
Streptococcus epidermidis
as a biofilm-positive control. Of nine clinically important serotype strains, M2, M6, M14, and M18 were found to significantly adhere to coated and uncoated polystyrene surfaces. Fibronectin and collagen types I and IV best supported primary adherence of serotype M2 and M18 strains, respectively, whereas serotype M6 and M14 strains strongly bound to uncoated polystyrene surfaces. Absorption measurements of safranin staining, as well as electron scanning and confocal laser scanning microscopy, documented that primary adherence led to subsequent formation of three-dimensional biofilm structures consisting of up to 46 bacterial layers. Of note, GAS isolates belonging to the same serotype were found to be very heterogeneous in their biofilm-forming behavior. Biofilm formation was equally efficient under static and continuous flow conditions and consisted of the classical three steps, including partial disintegration after long-term incubation. Activity of the SilC signaling peptide as a component of a putative quorum-sensing system was found to influence the biofilm structure and density of serotype M14 and M18 strains. Based on the presented methods and results, standardized analyses of GAS biofilms and their impact on GAS pathogenicity are now feasible.
Novel Luciferase Reporter System for In Vitro and Organ-Specific Monitoring of Differential Gene Expression inListeria monocytogenes
Authors: Bron Peter A. , Monk Ian R. , Corr Sinéad C. , Hill Colin , Gahan Cormac G. M. 
Published: April 2006

ABSTRACTIn this paper we describe construction of a luciferase-based vector, pPL2lux, and use of this vector to study gene expression inListeria monocytogenes. pPL2luxis a derivative of the listerial integration vector pPL2 and harbors a syntheticluxABCDEoperon encoding a fatty acid reductase complex (LuxCDE) involved in synthesis of the fatty aldehyde substrate for the bioluminescence reaction catalyzed by the LuxAB luciferase. We constructed pPL2luxderivatives in which thesecAandhlyApromoters were translationally fused toluxABCDEand integrated as a single copy into the chromosome ofL. monocytogenesEGD-e. Growth experiments revealed thathlyAwas expressed predominantly in the stationary phase in LB medium buffered at pH 7.4, whereassecAexpression could be detected in the exponential growth phase. Moreover, the correlation between luciferase activity and transcription levels, as determined by reverse transcriptase PCR, was confirmed using conditions known to lead to repression and activation of hemolysin expression (addition of cellobiose and activated charcoal, respectively). Furthermore, hemolysin expression could be monitored in real time during invasion of an intact monolayer of C2Bbe1 (Caco-2-derived) cells. Finally, hemolysin expression could be detected in the livers, spleens, and kidneys of mice 3 days postinfection. These experiments clearly established the effectiveness of pPL2luxas a quantitative reporter system for real-time, noninvasive evaluation of gene expression inL. monocytogenes.
Reduction of Soluble and Insoluble Iron Forms by Membrane Fractions of
Shewanella oneidensis
Grown under Aerobic and Anaerobic Conditions
Authors: Ruebush Shane S. , Brantley Susan L. , Tien Ming 
Published: April 2006

ABSTRACT

The effect of iron substrates and growth conditions on in vitro dissimilatory iron reduction by membrane fractions of
Shewanella oneidensis
MR-1 was characterized. Membrane fractions were separated by sucrose density gradients from cultures grown with O
2
, fumarate, and aqueous ferric citrate as the terminal electron acceptor. Marker enzyme assays and two-dimensional gel electrophoresis demonstrated the high degree of separation between the outer and cytosolic membrane. Protein expression pattern was similar between chelated iron- and fumarate-grown cultures, but dissimilar for oxygen-grown cultures. Formate-dependent ferric reductase activity was assayed with citrate-Fe
3+
, ferrozine-Fe
3+
, and insoluble goethite as electron acceptors. No activity was detected in aerobic cultures. For fumarate and chelated iron-grown cells, the specific activity for the reduction of soluble iron was highest in the cytosolic membrane. The reduction of ferrozine-Fe
3+
was greater than the reduction of citrate-Fe
3+
. With goethite, the specific activity was highest in the total membrane fraction (containing both cytosolic and outer membrane), indicating participation of the outer membrane components in electron flow. Heme protein content and specific activity for iron reduction was highest with chelated iron-grown cultures with no heme proteins in aerobically grown membrane fractions. Western blots showed that CymA, a heme protein involved in iron reduction, expression was also higher in iron-grown cultures compared to fumarate- or aerobic-grown cultures. To study these processes, it is important to use cultures grown with chelated Fe
3+
as the electron acceptor and to assay ferric reductase activity using goethite as the substrate.
Shear Stress, Temperature, and Inoculation Concentration Influence the Adhesion of Water-Stressed
Helicobacter pylori
to Stainless Steel 304 and Polypropylene
Authors: Azevedo N. F. , Pinto A. R. , Reis N. M. , Vieira M. J. , Keevil C. W. 
Published: April 2006

ABSTRACT

Although molecular techniques have identified
Helicobacter pylori
in drinking water-associated biofilms, there is a lack of studies reporting what factors affect the attachment of the bacterium to plumbing materials. Therefore, the adhesion of
H. pylori
suspended in distilled water to stainless steel 304 (SS304) coupons placed on tissue culture plates subjected to different environmental conditions was monitored. The extent of adhesion was evaluated for different water exposure times, using epifluorescence microscopy to count total cell numbers. High shear stresses—estimated through computational fluid dynamics—negatively influenced the adhesion of
H. pylori
to the substrata (
P
< 0.001), a result that was confirmed in similar experiments with polypropylene (
P
< 0.05). However, the temperature and inoculation concentration appeared to have no effect on adhesion (
P
> 0.05). After 2 hours,
H. pylori
cells appeared to be isolated on the surface of SS304 and were able to form small aggregates with longer exposure times. However, the formation of a three-dimensional structure was only very rarely observed. This study suggests that the detection of the pathogen in well water described by other authors can be related to the increased ability of
H. pylori
to integrate into biofilms under conditions of low shear stress. It will also allow a more rational selection of locations to perform molecular or plate culture analysis for the detection of
H. pylori
in drinking water-associated biofilms.
A New C-Type Lectin Similar to the Human Immunoreceptor DC-SIGN Mediates Symbiont Acquisition by a Marine Nematode
Authors: Bulgheresi Silvia , Schabussova Irma , Chen Tie , Mullin Nicholas P. , Maizels Rick M. , Ott Jörg A. 
Published: April 2006

ABSTRACT

Although thiotrophic symbioses have been intensively studied for the last three decades, nothing is known about the molecular mechanisms of symbiont acquisition. We used the symbiosis between the marine nematode
Laxus oneistus
and sulfur-oxidizing bacteria to study this process. In this association a monolayer of symbionts covers the whole cuticle of the nematode, except its anterior-most region. Here, we identify a novel Ca
2+
-dependent mannose-specific lectin that was exclusively secreted onto the posterior, bacterium-associated region of
L. oneistus
cuticle. A recombinant form of this lectin induced symbiont aggregation in seawater and was able to compete with the native lectin for symbiont binding in vivo. Surprisingly, the carbohydrate recognition domain of this mannose-binding protein was similar both structurally and functionally to a human dendritic cell-specific immunoreceptor. Our results provide a molecular link between bacterial symbionts and host-secreted mucus in a marine symbiosis and suggest conservation in the mechanisms of host-microbe interactions throughout the animal kingdom.
Protein Kinase C (PkcA) of
Aspergillus nidulans
Is Involved in Penicillin Production
Authors: Herrmann Martina , Spröte Petra , Brakhage Axel A. 
Published: April 2006

ABSTRACT

The biosynthesis of the β-lactam antibiotic penicillin in the filamentous fungus
Aspergillus nidulans
is catalyzed by three enzymes that are encoded by the
acvA
,
ipnA
, and
aatA
genes. A variety of
cis
-acting DNA elements and regulatory factors form a complex regulatory network controlling these β-lactam biosynthesis genes. Regulators involved include the CCAAT-binding complex AnCF and AnBH1. AnBH1 acts as a repressor of the penicillin biosynthesis gene
aatA
. Until now, however, little information has been available on the signal transduction cascades leading to the transcription factors. Here we show that inhibition of protein kinase C (Pkc) activity in
A. nidulans
led to cytoplasmic localization of an AnBH1-enhanced green fluorescent protein (EGFP) fusion protein. Computer analysis of the genome and screening of an
A. nidulans
gene library revealed that the fungus possesses two putative Pkc-encoding genes, which we designated
pkcA
and
pkcB
. Only PkcA showed all the characteristic features of fungal Pkc's. Production of
pkcA
antisense RNA in
A. nidulans
led to reduced growth and conidiation in
Aspergillus
minimal medium, while in fermentation medium it led to enhanced expression of an
aatAp-lacZ
gene fusion, reduced pencillin production, and predominantly cytoplasmic localization of AnBH1. These data agree with the finding that inhibition of Pkc activity prevented nuclear localization of AnBH1-EGFP. As a result, repression of
aatA
expression was relieved. The involvement of Pkc in penicillin biosynthesis is also interesting in light of the fact that in the yeast
Saccharomyces cerevisiae
, Pkc plays a major role in maintaining cell integrity.
Succession and Regulation Factors of Small Eukaryote Community Composition in a Lacustrine Ecosystem (Lake Pavin)
Authors: Lepère Cécile , Boucher Delphine , Jardillier Ludwig , Domaizon Isabelle , Debroas Didier 
Published: April 2006

ABSTRACT

The structure and dynamics of small eukaryotes (cells with a diameter less than 5 μm) were studied over two consecutive years in an oligomesotrophic lake (Lake Pavin in France). Water samples were collected at 5 and 30 m below the surface; when the lake was stratified, these depths corresponded to the epilimnion and hypolimnion. Changes in small-eukaryote structure were analyzed using terminal restriction fragment length polymorphism (T-RFLP) and cloning and sequencing of the 18S rRNA genes. Terminal restriction fragments from clones were used to reveal the dominant taxa in T-RFLP profiles of the environmental samples.
Spumella
-like cells (Chrysophyceae) did not dominate the small eukaryote community identified by molecular techniques in lacustrine ecosystems. Small eukaryotes appeared to be dominated by heterotrophic cells, particularly Cercozoa, which represented nearly half of the identified phylotypes, followed by the Fungi-LKM11 group (25%), choanoflagellates (10.3%) and Chrysophyceae (8.9%). Bicosoecida, Cryptophyta, and ciliates represented less than 9% of the community studied. No seasonal reproducibility in temporal evolution of the small-eukaryote community was observed from 1 year to the next. The T-RFLP patterns were related to bottom-up (resources) and top-down (grazing) variables using canonical correspondence analysis. The results showed a strong top-down regulation of small eukaryotes by zooplankton, more exactly, by cladocerans at 5 m and copepods at 30 m. Among bottom-up factors, temperature had a significant effect at both depths. The concentrations of nitrogenous nutrients and total phosphorus also had an effect on small-eukaryote dynamics at 5 m, whereas bacterial abundance and dissolved oxygen played a more important structuring role in the deeper zone.
Acanthocytes of
Stropharia rugosoannulata
Function as a Nematode-Attacking Device
Authors: Luo Hong , Li Xuan , Li Guohong , Pan Yanbo , Zhang Keqin 
Published: April 2006

ABSTRACT

Efficient killing of nematodes by
Stropharia rugosoannulata
Farlow ex Murrill cultures was observed. This fungus showed the ability to immobilize the free-living nematode
Panagrellus redivivus
Goodey within minutes and to immobilize the pine wilt nematode
Bursaphelenchus xylophilus
(Steiner & Buhrer) Nickle within hours on agar plates. Moreover,
P. redivivus
worms were completely degraded by the fungus within 24 to 48 h. The cultures of
S. rugosoannulata
studied shared the characteristic of abundantly producing cells with finger-like projections called acanthocytes. We showed that the nematode-attacking activity of this fungus is carried out by these spiny acanthocytes and that mechanical force is an important factor in the process. Furthermore, the growth and nematode-attacking activity of the fungus in soil were also determined, and our results suggest that acanthocytes are functional in soil.
Peptidoglycan Hydrolase Fusions Maintain Their Parental Specificities
Authors: Donovan David M. , Dong Shengli , Garrett Wes , Rousseau Geneviève M. , Moineau Sylvain , Pritchard David G. 
Published: April 2006

ABSTRACT

The increased incidence of bacterial antibiotic resistance has led to a renewed search for novel antimicrobials. Avoiding the use of broad-range antimicrobials through the use of specific peptidoglycan hydrolases (endolysins) might reduce the incidence of antibiotic-resistant pathogens worldwide.
Staphylococcus aureus
and
Streptococcus agalactiae
are human pathogens and also cause mastitis in dairy cattle. The ultimate goal of this work is to create transgenic cattle that are resistant to mastitis through the expression of an antimicrobial protein(s) in their milk. Toward this end, two novel antimicrobials were produced. The (i) full-length and (ii) 182-amino-acid, C-terminally truncated
S. agalactiae
bacteriophage B30 endolysins were fused to the mature lysostaphin protein of
Staphylococcus simulans
. Both fusions display lytic specificity for streptococcal pathogens and
S. aureus
. The full lytic ability of the truncated B30 protein also suggests that the SH3b domain at the C terminus is dispensable. The fusions are active in a milk-like environment. They are also active against some lactic acid bacteria used to make cheese and yogurt, but their lytic activity is destroyed by pasteurization (63°C for 30 min). Immunohistochemical studies indicated that the fusion proteins can be expressed in cultured mammalian cells with no obvious deleterious effects on the cells, making it a strong candidate for use in future transgenic mice and cattle. Since the fusion peptidoglycan hydrolase also kills multiple human pathogens, it also may prove useful as a highly selective, multipathogen-targeting antimicrobial agent that could potentially reduce the use of broad-range antibiotics in fighting clinical infections.
Isolation, Pure Culture, and Characterization of “
Candidatus
Arsenophonus arthropodicus,” an Intracellular Secondary Endosymbiont from the Hippoboscid Louse Fly
Pseudolynchia canariensis
Authors: Dale Colin , Beeton Michael , Harbison Christopher , Jones Tait , Pontes Mauricio 
Published: April 2006

ABSTRACT

Members of the genus
Arsenophonus
comprise a large group of bacterial endosymbionts that are widely distributed in arthropods of medical, veterinary, and agricultural importance. At present, little is known about the role of these bacteria in arthropods, because few representatives have been isolated and cultured in the laboratory. In the current study, we describe the isolation and pure culture of an
Arsenophonus
endosymbiont from the hippoboscid louse fly
Pseudolynchia canariensis
. We propose provisional nomenclature for this bacterium in the genus
Arsenophonus
as “
Candidatus
Arsenophonus arthropodicus.” Phylogenetic analyses indicate that “
Candidatus
Arsenophonus arthropodicus” is closely related to the
Arsenophonus
endosymbionts found in psyllids, whiteflies, aphids, and mealybugs. The pure culture of this endosymbiont offers new opportunities to examine the role of
Arsenophonus
in insects. To this end, we describe methods for the culture of “
Candidatus
Arsenophonus arthropodicus” in an insect cell line and the transformation of this bacterium with a broad-host-range plasmid.
Analysis of the Thermostability Determinants of Hyperthermophilic Esterase EstE1 Based on Its Predicted Three-Dimensional Structure
Authors: Rhee Jin-Kyu , Kim Do-Yun , Ahn Dae-Gyun , Yun Jung-Hyuk , Jang Seung-Hwan , Shin Hang-Cheol , Cho Hyun-Soo , Pan Jae-Gu , Oh Jong-Won 
Published: April 2006

ABSTRACT

The three-dimensional (3D) structure of the hyperthermophilic esterase EstE1 was constructed by homology modeling using
Archaeoglobus fulgidus
esterase as a reference, and the thermostability-structure relationship was analyzed. Our results verified the predicted 3D structure of EstE1 and identified the ion pair networks and hydrophobic interactions that are critical determinants for the thermostability of EstE1.
Characterization of
Streptococcus thermophilus
Host Range Phage Mutants
Authors: Duplessis Martin , Lévesque Céline M. , Moineau Sylvain 
Published: April 2006

ABSTRACT

To investigate phage-host interactions in
Streptococcus thermophilus
, a phage-resistant derivative (SMQ-301R) was obtained by challenging a Tn
917
library of phage-sensitive strain
S. thermophilus
SMQ-301 with virulent phage DT1. Mutants of phages DT1 and MD2 capable of infecting SMQ-301 and SMQ-301R were isolated at a frequency of 10
−6
. Four host range phage mutants were analyzed further and compared to the two wild-type phages. Altogether, three genes (
orf15
,
orf17
, and
orf18
) contained point mutations leading to amino acid substitutions and were responsible for the expanded host range. These three proteins were also identified in both phages by N-terminal sequencing and/or matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. The results suggest that at least three phage structural proteins may be involved in phage-host interactions in
S. thermophilus
.
In Vitro and In Vivo Survival and Transit Tolerance of Potentially Probiotic Strains Carried by Artichokes in the Gastrointestinal Tract
Authors: Valerio Francesca , De Bellis Palmira , Lonigro Stella Lisa , Morelli Lorenzo , Visconti Angelo , Lavermicocca Paola 
Published: April 2006

ABSTRACT

The ability of potentially probiotic strains of
Lactobacillus plantarum
and
Lactobacillus paracasei
to survive on artichokes for at least 90 days was shown. The anchorage of bacterial strains to artichokes improved their survival in simulated gastrointestinal digestion.
L. paracasei
IMPC2.1 was further used in an artichoke human feeding study involving four volunteers, and it was shown that the organism could be recovered from stools.
SXT-Related Integrating Conjugative Element in New World
Vibrio cholerae
Authors: Burrus Vincent , Quezada-Calvillo Roberto , Marrero Joeli , Waldor Matthew K. 
Published: April 2006

ABSTRACT

SXT-related integrating conjugative elements (ICEs) became prevalent in Asian
Vibrio cholerae
populations after
V. cholerae
O139 emerged. Here, we describe an SXT-related ICE, ICE
Vch
Mex1, in a Mexican environmental
V. cholerae
isolate. Identification of ICE
Vch
Mex1 represents the first description of an SXT-related ICE in the Western Hemisphere. The significant differences between the SXT and ICE
Vch
Mex1 genomes suggest that these ICEs have evolved independently.
Occurrence of
Vibrio parahaemolyticus
,
V. cholerae
, and
V. vulnificus
in Norwegian Blue Mussels (
Mytilus edulis
)
Authors: Bauer Anette , Østensvik Øyvin , Florvåg Malin , Ørmen Øyvind , Rørvik Liv Marit 
Published: April 2006

ABSTRACT

Vibrio parahaemolyticus
,
V. cholerae
, and
V. vulnificus
were isolated from 10.3%, 1.0%, and 0.1% of 885 blue mussel samples, respectively. Four of the samples contained
trh
+
V. parahaemolyticus
, while no
tdh
-positive isolates were detected. The
V. cholerae
isolates were non-O:1/non-O:139 serotypes and were
ctxA
negative.
Produce Isolates of the
Escherichia coli
Ont:H52 Serotype That Carry both Shiga Toxin 1 and Stable Toxin Genes
Authors: Monday Steven R. , Keys Christina , Hanson Patricia , Shen Yuelian , Whittam Thomas S. , Feng Peter 
Published: April 2006

ABSTRACT

Produce isolates of the
Escherichia coli
Ont:H52 serotype carried Shiga toxin 1 and stable toxin genes but only expressed Stx1. These strains had pulsed-field gel electrophoresis profiles that were 90% homologous to clinical Ont:H52 strains that had identical phenotypes and genotypes. All Ont:H52 strains had identical single nucleotide polymorphism profiles that are suggestive of a unique clonal group.