bluuebunny/crossref_metadata_2025_split huggingface dataset:
Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs
Authors: Fonty Gérard , Joblin Keith , Chavarot Michel , Roux Remy , Naylor Graham , Michallon Fabien 
Published: August 2007

ABSTRACT

The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (10
7
to 10
8
cells g
−1
) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H
2
utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H
2
utilization was similar to that in conventional lambs. H
2
utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H
2
utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H
2
in the rumen.
Use of a Disposable Water Filter for Prevention of False-Positive Results due to Nontuberculosis Mycobacteria in a Clinical Laboratory Performing Routine Acid-Fast Staining for Tuberculosis
Authors: Tu Hui-Zin , Chen Chiao-Shan , Huang Tsi-Shu , Huang Wen-Kuei , Chen Yao-shen , Liu Yung-ching , Lin Yusen Eason 
Published: August 2007

ABSTRACT
A point-of-use 0.2-μm filter was evaluated for elimination of nontuberculosis mycobacteria in laboratory water to reduce false-positive acid-fast bacillus staining results. Use of the point-of-use filter can significantly reduce the false-positive rate to 1.2% compared to samples treated with tap water (10.7%) and deionized water (8.7%).
Inactivation of an Iron Transporter in
Lactococcus lactis
Results in Resistance to Tellurite and Oxidative Stress
Authors: Turner Mark S. , Tan Yu Pei , Giffard Philip M. 
Published: August 2007

ABSTRACT

In
Lactococcus lactis
, the interactions between oxidative defense, metal metabolism, and respiratory metabolism are not fully understood. To provide an insight into these processes, we isolated and characterized mutants of
L. lactis
resistant to the oxidizing agent tellurite (TeO
3
2−
), which generates superoxide radicals intracellularly. A collection of tellurite-resistant mutants was obtained using random transposon mutagenesis of
L. lactis
. These contained insertions in genes encoding a proton-coupled Mn
2+
/Fe
2+
transport homolog (
mntH
), the high-affinity phosphate transport system (
pstABCDEF
), a putative osmoprotectant uptake system (
choQ
), and a homolog of the oxidative defense regulator
spx
(
trmA
). The tellurite-resistant mutants all had better survival than the wild type following aerated growth. The
mntH
mutant was found to be impaired in Fe
2+
uptake, suggesting that MntH is a Fe
2+
transporter in
L. lactis
. This mutant is capable of carrying out respiration but does not generate as high a final pH and does not exhibit the long lag phase in the presence of hemin and oxygen that is characteristic of wild-type
L. lactis
. This study suggests that tellurite-resistant mutants also have increased resistance to oxidative stress and that intracellular Fe
2+
can heighten tellurite and oxygen toxicity.
Absence of Serotype-Specific Surface Antigen in Laboratory Variants of Epidemic-Associated
Listeria monocytogenes
Strains
Authors: Cheng Ying , Yue Lili , Elhanafi Driss , Kathariou S. 
Published: August 2007

ABSTRACT

Variants that lacked reactivity with the serotype 4b-specific monoclonal antibody c74.22 and that lost susceptibility to certain
Listeria
- or serotype 4b-specific phages were identified in the course of genetic studies with serotype 4b
Listeria monocytogenes
strains H7550 and F2381L (epidemic clones I and II, respectively). Our findings suggest that such variants can become inadvertently established under laboratory conditions and suggest caution in work involving serotype 4b strains and genetic constructs thereof.
Diatom-Derived Carbohydrates as Factors Affecting Bacterial Community Composition in Estuarine Sediments
Authors: Haynes Kelly , Hofmann Tanja A. , Smith Cindy J. , Ball Andrew S. , Underwood Graham J. C. , Osborn A. Mark 
Published: August 2007

ABSTRACT

Microphytobenthic biofilms in estuaries, dominated by epipelic diatoms, are sites of high primary productivity. These diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides and glycoproteins, providing a substantial pool of organic carbon available to heterotrophs within the sediment. In this study, sediment slurry microcosms were enriched with either colloidal carbohydrates or colloidal EPS (cEPS) or left unamended. Over 10 days, the fate of these carbohydrates and changes in β-glucosidase activity were monitored. Terminal restriction fragment length polymorphism (T-RFLP), DNA sequencing, and quantitative PCR (Q-PCR) analysis of 16S rRNA sequences were used to determine whether sediment bacterial communities exhibited compositional shifts in response to the different available carbon sources. Initial heterotrophic activity led to reductions in carbohydrate concentrations in all three microcosms from day 0 to day 2, with some increases in β-glucosidase activity. During this period, treatment-specific shifts in bacterial community composition were not observed. However, by days 4 and 10, the bacterial community in the cEPS-enriched sediment diverged from those in colloid-enriched and unamended sediments, with Q-PCR analysis showing elevated bacterial numbers in the cEPS-enriched sediment at day 4. Community shifts were attributed to changes in cEPS concentrations and increased β-glucosidase activity. T-RFLP and sequencing analyses suggested that this shift was not due to a total community response but rather to large increases in the relative abundance of members of the γ-proteobacteria, particularly
Acinetobacter
-related bacteria. These experiments suggest that taxon- and substrate-specific responses within the bacterial community are involved in the degradation of diatom-derived extracellular carbohydrates.
Saccharomyces cerevisiae
BLYAS, a New Bioluminescent Bioreporter for Detection of Androgenic Compounds
Authors: Eldridge Melanie L. , Sanseverino John , Layton Alice C. , Easter James P. , Schultz T. Wayne , Sayler Gary S. 
Published: August 2007

ABSTRACT

A
Saccharomyces cerevisiae
strain, capable of autonomous bioluminescence, was engineered to respond to androgenic chemicals. The strain,
S. cerevisiae
BLYAS, contains the human androgen receptor in the chromosome and was constructed by inserting a series of androgen response elements between divergent yeast promoters GPD and ADH1 on pUTK401 that constitutively expressed
luxA
and
luxB
to create pUTK420. Cotransformation of this plasmid with a second plasmid (pUTK404), containing the genes required for aldehyde synthesis (
luxCDE
) and FMN reduction (
frp
), yielded a bioluminescent bioreporter responsive to androgenic chemicals. Using dihydrotestosterone (DHT) as a standard, the response time and the 50% effective concentration values were 3 to 4 h and (9.7 ± 4.6) × 10
−9
M, respectively. The lower limit of detection in response to DHT was 2.5 × 10
−9
M, and in response to testosterone it was 2.5 × 10
−10
M. This strain is suitable for high-throughput screening of chemicals with potential for remote environmental monitoring systems because of the assay speed, sensitivity, and self-containment.
Inhibition of Quorum Sensing in
Serratia marcescens
AS-1 by Synthetic Analogs of
N
-Acylhomoserine Lactone
Authors: Morohoshi Tomohiro , Shiono Toshitaka , Takidouchi Kiyomi , Kato Masashi , Kato Norihiro , Kato Junichi , Ikeda Tsukasa 
Published: August 2007

ABSTRACT

Quorum sensing is a regulatory system for controlling gene expression in response to increasing cell density.
N
-Acylhomoserine lactone (AHL) is produced by gram-negative bacteria, which use it as a quorum-sensing signal molecule.
Serratia marcescens
is a gram-negative opportunistic pathogen which is responsible for an increasing number of serious nosocomial infections.
S. marcescens
AS-1 produces
N
-hexanoyl homoserine lactone (C
6
-HSL) and
N
-(3-oxohexanoyl) homoserine lactone and regulates prodigiosin production, swarming motility, and biofilm formation by AHL-mediated quorum sensing. We synthesized a series of
N
-acyl cyclopentylamides with acyl chain lengths ranging from 4 to 12 and estimated their inhibitory effects on prodigiosin production in AS-1. One of these molecules,
N
-nonanoyl-cyclopentylamide (C
9
-CPA), had a strong inhibitory effect on prodigiosin production. C
9
-CPA also inhibited the swarming motility and biofilm formation of AS-1. A competition assay revealed that C
9
-CPA was able to inhibit quorum sensing at four times the concentration of exogenous C
6
-HSL and was more effective than the previously reported halogenated furanone. Our results demonstrated that C
9
-CPA was an effective quorum-sensing inhibitor for
S. marcescens
AS-1.
σB-Dependent and σB-Independent Mechanisms Contribute to Transcription ofListeria monocytogenesCold Stress Genes during Cold Shock and Cold Growth
Authors: Chan Yvonne C. , Boor Kathryn J. , Wiedmann Martin 
Published: August 2007

ABSTRACTThe role of the stress response regulator σB(encoded bysigB) in directing the expression of selected putative and confirmed cold response genes was evaluated usingListeria monocytogenes10403S and an isogenic ΔsigBmutant, which were either cold shocked at 4°C in brain heart infusion (BHI) broth for up to 30 min or grown at 4°C in BHI for 12 days. Transcript levels of the housekeeping genesrpoBandgap, the σB-dependent genesopuCAandbsh, and the cold stress genesltrC, oppA, andfriwere measured using quantitative reverse transcriptase PCR. Transcriptional start sites forltrC, oppA, andfriwere determined using rapid amplification of cDNA ends PCR. Centrifugation was found to rapidly induce σB-dependent transcription, which necessitated the use of centrifugation-independent protocols to evaluate the contributions of σBto transcription during cold shock. Our data confirmed that transcription of the cold stress genesltrCandfriis at least partially σBdependent and experimentally identified a σB-dependentltrCpromoter. In addition, our data indicate that (i) while σBactivity is induced during 30 min of cold shock, this cold shock does not induce the transcription of σB-dependent or -independent cold shock genes; (ii) σBis not required forL. monocytogenesgrowth at 4°C in BHI; and (iii) transcription of the putative cold stress genesopuCA, fri, andoppAis σBindependent during growth at 4°C, while bothbshandltrCshow growth phase and σB-dependent transcription during growth at 4°C. We conclude that σB-dependent and σB-independent mechanisms contribute to the ability ofL. monocytogenesto survive and grow at low temperatures.
The Motility Symbiont of the Termite Gut FlagellateCaduceia versatilisIs a Member of the “Synergistes” Group
Authors: Hongoh Yuichi , Sato Tomoyuki , Dolan Michael F. , Noda Satoko , Ui Sadaharu , Kudo Toshiaki , Ohkuma Moriya 
Published: August 2007

ABSTRACTThe flagellateCaduceia versatilisin the gut of the termiteCryptotermes cavifronsreportedly propels itself not by its own flagella but solely by the flagella of ectosymbiotic bacteria. Previous microscopic observations have revealed that the motility symbionts are flagellated rods partially embedded in the host cell surface and that, together with a fusiform type of ectosymbiotic bacteria without flagella, they cover almost the entire surface. To identify these ectosymbionts, we conducted 16S rRNA clone analyses of bacteria physically associated with theCaduceiacells. Two phylotypes were found to predominate in the clone library and were phylogenetically affiliated with the “Synergistes” phylum and the orderBacteroidalesin theBacteroidetesphylum. Probes specifically targeting 16S rRNAs of the respective phylotypes were designed, and fluorescence in situ hybridization (FISH) was performed. As a result, the “Synergistes” phylotype was identified as the motility symbiont; theBacteroidalesphylotype was the fusiform ectobiont. The “Synergistes” phylotype was a member of a cluster comprising exclusively uncultured clones from the guts of various termite species. Interestingly, four other phylotypes in this cluster, including the one sharing 95% sequence identity with the motility symbiont, were identified as nonectosymbiotic, or free-living, gut bacteria by FISH. We thus suggest that the motility ectosymbiont has evolved from a free-living gut bacterium within this termite-specific cluster. Based on these molecular and previous morphological data, we here propose a novel genus and species, “CandidatusTammella caduceiae,” for this unique motility ectosymbiont ofCaducaia versatilis.
Isolation ofSalmonella entericaSerovar Enteritidis from Houseflies (Musca domestica) Found in Rooms ContainingSalmonellaSerovar Enteritidis-Challenged Hens
Authors: Holt Peter S. , Geden Christopher J. , Moore Randle W. , Gast Richard K. 
Published: August 2007

ABSTRACTHouseflies (Musca domestica) released into rooms containing hens challenged withSalmonella entericaserovar Enteritidis (Salmonellaserovar Enteritidis) rapidly became contaminated withSalmonellaserovar Enteritidis. Forty to 50% of the flies were contaminated at 48 h, and the percentage increased to 50 to 70% at 4 and 7 days postexposure and then decreased to 30% at day 15. Initial attempts at recovering surface organisms for culture using an aqueous rinse were largely unsuccessful, while cultures of internal contents readily recoveredSalmonellaserovar Enteritidis. However, when 0.5% detergent was incorporated into the rinse, high recovery levels of bacteria were observed from both external and internal culture regimens, indicating equal distribution of the organism on and in the fly and a tighter interaction of the organism with the host than previously thought.Salmonellaserovar Enteritidis was isolated routinely from the fly gut, on rare occasions from the crop, and never from the salivary gland. Feeding contaminated flies to hens resulted in gut colonization of a third of the birds, but release of contaminated flies in a room containing previously unchallenged hens failed to result in colonization of any of the subject birds. These results indicate that flies exposed to an environment containingSalmonellaserovar Enteritidis can become colonized with the organism and might serve as a source for transmission ofSalmonellaserovar Enteritidis within a flock situation.
Survival of
Mycobacterium avium
in Drinking Water Biofilms as Affected by Water Flow Velocity, Availability of Phosphorus, and Temperature
Authors: Torvinen Eila , Lehtola Markku J. , Martikainen Pertti J. , Miettinen Ilkka T. 
Published: August 2007

ABSTRACT

Mycobacterium avium
is a potential pathogen occurring in drinking water systems. It is a slowly growing bacterium producing a thick cell wall containing mycolic acids, and it is known to resist chlorine better than many other microbes. Several studies have shown that pathogenic bacteria survive better in biofilms than in water. By using Propella biofilm reactors, we studied how factors generally influencing the growth of biofilms (flow rate, phosphorus concentration, and temperature) influence the survival of
M. avium
in drinking water biofilms. The growth of biofilms was followed by culture and DAPI (4′,6′-diamidino-2-phenylindole) staining, and concentrations of
M. avium
were determined by culture and fluorescence in situ hybridization methods. The spiked
M. avium
survived in biofilms for the 4-week study period without a dramatic decline in concentration. The addition of phosphorus (10 μg/liter) increased the number of heterotrophic bacteria in biofilms but decreased the culturability of
M. avium
. The reason for this result is probably that phosphorus increased competition with other microbes. An increase in flow velocity had no effect on the survival of
M. avium
, although it increased the growth of biofilms. A higher temperature (20°C versus 7°C) increased both the number of heterotrophic bacteria and the survival of
M. avium
in biofilms. In conclusion, the results show that in terms of affecting the survival of slowly growing
M. avium
in biofilms, temperature is a more important factor than the availability of nutrients like phosphorus.
Biofilm Interactions between Distinct Bacterial Genera Isolated from Drinking Water
Authors: Simões Lúcia Chaves , Simões Manuel , Vieira Maria João 
Published: August 2007

ABSTRACT

In the environment, multiple microorganisms coexist as communities, competing for resources and often associated as biofilms. In this study, single- and dual-species biofilm formation by, and specific activities of, six heterotrophic intergeneric bacteria were determined using 96-well polystyrene plates over a 72-h period. These bacteria were isolated from drinking water and identified by partial 16S rRNA gene sequencing. A series of planktonic studies was also performed, assessing the bacterial growth rate, motility, and production of quorum-sensing inhibitors (QSI). This constituted an attempt to identify key attributes allowing bacteria to effectively interact and coexist in a drinking-water environment. We observed that in both pure and dual cultures, all of the isolates formed stable biofilms within 72 h, with specific metabolic activity decreasing, in most cases, with an increase in biofilm mass. The largest single- and dual-biofilm amounts were found for
Methylobacterium
sp. and the combination of
Methylobacterium
sp. and
Mycobacterium mucogenicum
, respectively. Evidences of microbial interactions in dual-biofilm formation, associated with appreciable biomass variation in comparison with single biofilms, were found for the following cases: synergy/cooperation between
Sphingomonas capsulata
and
Burkholderia cepacia, S. capsulata
and
Staphylococcus
sp., and
B. cepacia
and
Acinetobacter calcoaceticus
and antagonism between
S. capsulata
and
M. mucogenicum, S. capsulata
and
A. calcoaceticus
, and
M. mucogenicum
and
Staphylococcus
sp. A neutral interaction was found for
Methylobacterium
sp.-
M. mucogenicum, S. capsulata
-
Staphylococcus
sp.,
M. mucogenicum
-
A. calcoaceticus
, and
Methylobacterium
sp.-
A. calcoaceticus
biofilms, since the resultant dual biofilms had a mass and specific metabolic activity similar to the average for each single biofilm.
B. cepacia
had the highest growth rate and motility and produced QSI. Other bacteria producing QSI were
Methylobacterium
sp.,
S. capsulata
, and
Staphylococcus
sp. However, only for
S. capsulata
-
M. mucogenicum, S. capsulata
-
A. calcoaceticus
, and
M. mucogenicum
-
Staphylococcus
sp., dual-biofilm formation seems to be regulated by the QSI produced by
S. capsulata
and
Staphylococcus
sp. and by the increased growth rate of
S. capsulata
. The parameters assessed by planktonic studies did not allow prediction and generalization of the exact mechanism regulating dual-species biofilm formation between the drinking-water bacteria.
Optimization of Airborne Endotoxin Exposure Assessment: Effects of Filter Type, Transport Conditions, Extraction Solutions, and Storage of Samples and Extracts
Authors: Spaan Suzanne , Heederik Dick J. J. , Thorne Peter S. , Wouters Inge M. 
Published: August 2007

ABSTRACT
Endotoxin exposure occurs in homes and occupational environments and is known to cause adverse health effects. In order to compare results from different studies and establish standards, airborne endotoxin exposures should be assessed using standardized methods. Although the European Committee for Standardization (CEN) developed guidelines for endotoxin exposure assessment, these leave room for individual interpretation. The influence of methods of sampling, extraction, and analysis has never been investigated in a full experimental design. Thus, we sought to fully elucidate the importance of all facets of endotoxin assessment. Inhalable dust samples collected simultaneously were used to investigate the effects on and interactions with airborne endotoxin concentration in two working environments of filter type (glass fiber or Teflon), transport conditions (with/without desiccant), sample storage (−20 or 4°C), extraction solution (pyrogen-free water [PFW] or PFW plus 0.05% Tween 20), extract storage (−20 or 4°C), and assay solution (PFW or PFW plus 0.05% Tween 20). Four hundred samples were collected and randomly distributed over the 20 combinations of treatments. There were no differences found for transport conditions and storage temperature of extracts. Also, no interactions between study variables existed. Sampling on glass-fiber filters, storage of samples in the freezer, and extraction in PFW plus 0.05% Tween 20 resulted in 1.3-, 1.1-, and 2.1-fold-higher estimated endotoxin concentrations, respectively. Use of PFW plus 0.05% Tween 20 in the assay solution had an additive effect. Thus, this study investigated gaps in the CEN protocol and provides data with which to fully specify a protocol for standardization of endotoxin exposure assessment.
Influence of Geographical Origin and Flour Type on Diversity of Lactic Acid Bacteria in Traditional Belgian Sourdoughs
Authors: Scheirlinck Ilse , Van der Meulen Roel , Van Schoor Ann , Vancanneyt Marc , De Vuyst Luc , Vandamme Peter , Huys Geert 
Published: August 2007

ABSTRACTA culture-based approach was used to investigate the diversity of lactic acid bacteria (LAB) in Belgian traditional sourdoughs and to assess the influence of flour type, bakery environment, geographical origin, and technological characteristics on the taxonomic composition of these LAB communities. For this purpose, a total of 714 LAB from 21 sourdoughs sampled at 11 artisan bakeries throughout Belgium were subjected to a polyphasic identification approach. The microbial composition of the traditional sourdoughs was characterized by bacteriological culture in combination with genotypic identification methods, including repetitive element sequence-based PCR fingerprinting and phenylalanyl-tRNA synthase (pheS) gene sequence analysis. LAB from Belgian sourdoughs belonged to the generaLactobacillus, Pediococcus, Leuconostoc, Weissella, andEnterococcus, with the heterofermentative speciesLactobacillus paralimentarius, Lactobacillus sanfranciscensis, Lactobacillus plantarum, andLactobacillus pontisas the most frequently isolated taxa. Statistical analysis of the identification data indicated that the microbial composition of the sourdoughs is mainly affected by the bakery environment rather than the flour type (wheat, rye, spelt, or a mixture of these) used. In conclusion, the polyphasic approach, based on rapid genotypic screening and high-resolution, sequence-dependent identification, proved to be a powerful tool for studying the LAB diversity in traditional fermented foods such as sourdough.