bluuebunny/crossref_metadata_2025_split huggingface dataset:
Postprocessing In Vitro Digestion Challenge To Evaluate Survival of
Escherichia coli
O157:H7 in Fermented Dry Sausages
Authors: Naim Fadia , Messier Serge , Saucier Linda , Piette Gabriel 
Published: November 2004

ABSTRACT

Fermented dry sausages, inoculated with
Escherichia coli
O157:H7 during batter preparation, were submitted to an in vitro digestion challenge to evaluate the extent to which passage through the human gastrointestinal tract could inactivate the pathogenic cells, previously stressed by the manufacturing process. The numbers of surviving
E. coli
O157:H7 cells remained constant after a 1-min exposure of the finely chopped sausage to synthetic saliva or during the following 120-min exposure to synthetic gastric juice at an initial pH of 2.0. However, significant (
P
≤ 0.05) growth of the pathogen (1.03 to 2.16 log
10
CFU/g) was observed in a subsequent 250-min exposure to a synthetic pancreatic juice at pH 8.0. In a different set of experiments, fractions from the gastric suspension were transferred into the synthetic pancreatic juice at 30-min intervals to mimic the dynamics of gastric emptying. Concurrently, the pH of the remaining gastric fluid was reduced to 3.0, 2.5, and 2.0 to simulate the gradual reacidification of the stomach contents after the initial buffering effect resulting from meal ingestion. Under these new conditions, pathogen growth during pancreatic challenge was observed for the first few fractions released from the stomach (90 min of exposure [pH 2.5]), but growth was no longer possible in the fractions submitted to the most severe gastric challenge (120 min of exposure [pH < 2.2]).
Dynamics of Multiple
lin
Gene Expression in
Sphingomonas paucimobilis
B90A in Response to Different Hexachlorocyclohexane Isomers
Authors: Suar Mrutyunjay , van der Meer Jan Roelof , Lawlor Kirsten , Holliger Christof , Lal Rup 
Published: November 2004

ABSTRACT

Sphingomonas paucimobilis
B90A is able to degrade the α-, β-, γ-, and δ-isomers of hexachlorocyclohexane (HCH). It contains the genes
linA
,
linB
,
linC
,
linD
,
linE
, and
linR
, which have been implicated in HCH degradation. In this study, dynamic expression of the
lin
genes was measured in chemostat-grown
S. paucimobilis
B90A by RNA dot blot hybridization and real-time reverse transcriptase PCR upon exposure to a pulse of different HCH isomers. Irrespective of the addition of HCH,
linA
,
linB
, and
linC
were all expressed constitutively. In contrast,
linD
and
linE
were induced with α-HCH (2 mg/liter) and γ-HCH (7 mg/liter). A sharp increase in mRNA levels for
linD
and
linE
was observed from 10 to 45 min after the addition of α- or γ-HCH. Induction of
linD
and
linE
was not detectable upon the addition of 0.7 mg of γ-HCH per liter, although the compound was degraded by the cells. The addition of β-HCH (5 mg/liter) or δ-HCH (20 mg/liter) did not lead to
linE
and
linD
induction, despite the fact that 50% of the compounds were degraded. This suggests that degradation of β- and δ-HCH proceeds by a different pathway than that of α- and γ-HCH.
Molecular Characterization of
Brevibacillus laterosporus
and Its Potential Use in Biological Control
Authors: de Oliveira Edmar Justo , Rabinovitch Leon , Monnerat Rose Gomes , Passos Liana Konovaloff Jannotti , Zahner Viviane 
Published: November 2004

ABSTRACT

Thirty-three strains of
Brevibacillus laterosporus
, including three novel strains isolated from Brazilian soil samples, were examined for genetic variability by the use of different PCR-based methods. Molecular markers that could characterize bacterial strains with regards to their pathogenic potential were investigated. In addition, toxicity was assessed by the use of insects belonging to the orders Lepidoptera and Coleoptera and the mollusk
Biomphalaria glabrata
. Among the targets tested,
Biomphalaria glabrata
demonstrated the highest degree of sensitivity to
B. laterosporus
, with some strains inducing 90 to 100% mortality in snails aged 3 and 12 days posteclosion. Larvae of the coleopteron
Anthonomus grandis
were also susceptible, presenting mortality levels of between 33 and 63%. Toxicity was also noted towards the lepidopteron
Anticarsia gemmatalis
. In contrast, no mortality was recorded among test populations of
Tenebrio molitor
or
Spodoptera frugiperda
. The application of intergenic transcribed spacer PCR and BOX-PCR generated 15 and 17 different genotypes, respectively. None of the molecular techniques allowed the identification of a convenient marker that was associated with any entomopathogenic phenotype. However, a 1,078-bp amplicon was detected for all strains of
B. laterosporus
when a primer for amplification of the BOXA1R region was used. Similarly, a 900-bp amplicon was generated from all isolates by use of the primer OPA-11 for randomly amplified polymorphic DNA analysis. These amplicons were not detected for other phenotypically related
Brevibacillus
species, indicating that they represent markers that are specific for
B. laterosporus
, which may prove useful for the isolation and identification of new strains of this species.
Pore Size Dependence on Growth Temperature Is a Common Characteristic of the Major Outer Membrane Protein OprF in Psychrotrophic and Mesophilic
Pseudomonas
Species
Authors: Jaouen Thomas , Dé Emmanuelle , Chevalier Sylvie , Orange Nicole 
Published: November 2004

ABSTRACT

Pseudomonas
species adapt well to hostile environments, which are often subjected to rapid variations. In these bacteria, the outer membrane plays an important role in the sensing of environmental conditions such as temperature. In previous studies, it has been shown that in the psychrotrophic strain
P. fluorescens
MF0, the major porin OprF changes its channel size according to the growth conditions and could affect outer membrane permeability. Studies of the channel-forming properties of OprFs from
P. putida
01G3 and
P. aeruginosa
PAO1 in planar lipid bilayers generated similar results. The presence of a cysteine- or proline-rich cluster in the central linker region is not essential for channel size modulations. These findings suggest that OprF could adopt two alternative conformations in the outer membrane and that folding is thermoregulated. In contrast, no difference according to growth temperature was observed for structurally different outer membrane proteins, such as OprE3 from the
Pseudomonas
OprD family of specific porins. Our results are consistent with the fact that the decrease in channel size observed at low growth temperature is a particular feature of the OprF porin in various psychrotrophic and mesophilic
Pseudomonas
species isolated from diverse ecological niches. The ability to reduce outer membrane permeability at low growth temperature could provide these bacteria with adaptive advantages.
Life History Implications of rRNA Gene Copy Number in
Escherichia coli
Authors: Stevenson Bradley S. , Schmidt Thomas M. 
Published: November 2004

ABSTRACT

The role of the rRNA gene copy number as a central component of bacterial life histories was studied by using strains of
Escherichia coli
in which one or two of the seven rRNA operons (
rrnA
and/or
rrnB
) were deleted. The relative fitness of these strains was determined in competition experiments in both batch and chemostat cultures. In batch cultures, the decrease in relative fitness corresponded to the number of rRNA operons deleted, which could be accounted for completely by increased lag times and decreased growth rates. The magnitude of the deleterious effect varied with the environment in which fitness was measured: the negative consequences of rRNA operon deletions increased under culture conditions permitting more-rapid growth. The rRNA operon deletion strains were not more effective competitors under the regimen of constant, limited resources provided in chemostat cultures. Enhanced fitness in chemostat cultures would have suggested a simple tradeoff in which deletion strains grew faster (due to more efficient resource utilization) under resource limitation. The contributions of growth rate, lag time,

K
s

, and death rate to the fitness of each strain were verified through mathematical simulation of competition experiments. These data support the hypothesis that multiple rRNA operons are a component of bacterial life history and that they confer a selective advantage permitting microbes to respond quickly and grow rapidly in environments characterized by fluctuations in resource availability.
Novel Sulfonolipid in the Extremely Halophilic Bacterium
Salinibacter ruber
Authors: Corcelli Angela , Lattanzio Veronica M. T. , Mascolo Giuseppe , Babudri Francesco , Oren Aharon , Kates Morris 
Published: November 2004

ABSTRACT

Salinibacter ruber
is an extremely halophilic bacterium, phylogenetically affiliated with the
Flavobacterium
/
Cytophaga
branch of the domain
Bacteria
. Electrospray mass analyses (negative ion) of the total lipid extract of a pure culture of
S. ruber
shows a characteristic peak at
m/z
660 as the most prominent peak in the high-mass range of the spectrum. A novel sulfonolipid, giving rise to the molecular ion [M-H]
−
of
m/z
660, has been identified. The sulfonolipid isolated and purified by thin-layer chromatography was shown by chemical degradation, mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance analysis to have the structure 2-carboxy-2-amino-3-
O
-(13′-methyltetradecanoyl)-4-hydroxy-18-methylnonadec-5-ene-1-sulfonic acid. This lipid represents about 10% of total cellular lipids, and it appears to be a structural variant of the sulfonolipids found as main components of the cell envelope of gliding bacteria of the genus
Cytophaga
and closely related genera (W. Godchaux and E. R. Leadbetter, J. Bacteriol.
153
:1238-1246, 1983) and of diatoms (R. Anderson, M. Kates, and B. E. Volcani, Biochim. Biophys. Acta
528
:89-106, 1978). Since this sulfonolipid has never been observed in any other extreme halophilic microorganism, we consider the peak at
m/z
660 the lipid signature of
Salinibacter
. This study suggests that this novel sulfonolipid may be used as a chemotaxonomic marker for the detection of
Salinibacter
within the halophilic microbial community in saltern crystallizer ponds and other hypersaline environments.
Use of Cell Culture-PCR Assay Based on Combination of A549 and BGMK Cell Lines and Molecular Identification as a Tool To Monitor Infectious Adenoviruses and Enteroviruses in River Water
Authors: Lee Cheonghoon , Lee Seung-Hoon , Han Euiri , Kim Sang-Jong 
Published: November 2004

ABSTRACT
Viral contamination in environmental samples can be underestimated because a single cell line might reproduce only some enteric viruses and some enteric viruses do not exhibit apparent cytopathic effects in cell culture. To overcome this problem, we evaluated a cell culture-PCR assay based on a combination of A549 and Buffalo green monkey kidney (BGMK) cell lines as a tool to monitor infectious adenoviruses and enteroviruses in river water. Water samples were collected 10 times at each of four rivers located in Gyeonggi Province, South Korea, and then cultured on group 1 cells (BGMK cells alone) and group 2 cells (BGMK and A549 cells). Reverse transcription and multiplex PCR were performed, followed by phylogenetic analysis of the amplicons. Thirty (75.0%) of the 40 samples were positive for viruses based on cell culture, and the frequency of positive samples grown on group 2 cells (65.0%) was higher than the frequency of positive samples grown on group 1 cells (50.0%). The number of samples positive for adenoviruses was higher with A549 cells (13 samples) than with BGMK cells (one sample); the numbers of samples positive for enteroviruses were similar with both types of cells. By using phylogenetic analysis, adenoviral amplicons were grouped into subgenera A, C, D, and F, and enteroviral amplicons were grouped into coxsackieviruses B3 and B4 and echoviruses 6, 7, and 30, indicating that A549 and BGMK cells were suitable for recovering a wide range of adenoviral and enteroviral types. The cell culture-PCR assay with a combination of A549 and BGMK cells and molecular identification could be a useful tool for monitoring infectious adenoviruses and enteroviruses in aquatic environments.
Benthic and Pelagic Viral Decay Experiments: a Model-Based Analysis and Its Applicability
Authors: Fischer Ulrike R. , Weisz Willy , Wieltschnig Claudia , Kirschner Alexander K. T. , Velimirov Branko 
Published: November 2004

ABSTRACT

The viral decay in sediments, that is, the decrease in benthic viral concentration over time, was recorded after inhibiting the production of new viruses. Assuming that the viral abundance in an aquatic system remains constant and that viruses from lysed bacterial cells replace viruses lost by decay, the decay of viral particles can be used as a measure of viral production. Decay experiments showed that this approach is a useful tool to assess benthic viral production. However, the time course pattern of the decay experiments makes their interpretation difficult, regardless of whether viral decay is determined in the water column or in sediments. Different curve-fitting approaches (logarithmic function, power function, and linear regression) to describe the time course of decay experiments found in the literature are used in the present study and compared to a proposed “exponential decay” model based on the assumption that at any moment the decay is proportional to the amount of viruses present. Thus, an equation of the form
d
VA/
dt
= −
k
× VA leading to the time-integrated form VA

t

= VA
0
×

e
−k

×

t

was used, where
k
represents the viral decay rate (h
−1
), VA

t

is the viral abundance (viral particles ml
−1
) at time
t
(h), and VA
0
is the initial viral abundance (viral particles ml
−1
). This approach represents the best solution for an accurate curve fitting based on a mathematical model for a realistic description of viral decay occurring in aquatic systems. Decay rates ranged from 0.0282 to 0.0696 h
−1
(mean, 0.0464 h
−1
). Additionally, a mathematical model is presented that enables the quantification of the viral control of bacterial production. The viral impact on bacteria based on decay rates calculated from the different mathematical approaches varied widely within one and the same decay experiment. A comparison of the viral control of bacterial production in different aquatic environments is, therefore, improper when different mathematical formulas are used to interpret viral decay experiments.
Denaturing Gradient Gel Electrophoretic Analysis of Ammonia-Oxidizing Bacterial Community Structure in the Lower Seine River: Impact of Paris Wastewater Effluents
Authors: Cébron Aurélie , Coci Manuela , Garnier Josette , Laanbroek Hendrikus J. 
Published: November 2004

ABSTRACT

The Seine River is strongly affected by the effluents from the Achères wastewater treatment plant (WWTP) downstream of the city of Paris. We have shown that the effluents introduce large amounts of ammonia and inoculate the receiving medium with nitrifying bacteria. The aim of the present study was to investigate the diversity of the ammonia-oxidizing bacterial population by identifying autochthonous bacteria from upstream and/or allochthonous ammonia-oxidizing bacteria from the WWTP effluents. Measurements of potential nitrifying activity, competitive PCR, and denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal DNA fragments specific to ammonia-oxidizing bacteria (AOB) were used to explore the succession and shifts of the ammonia-oxidizing community in the lower Seine River and to analyze the temporal and spatial functioning of the system at several different sampling dates. A major revelation was the stability of the patterns. The CTO primers used in this study (G. A. Kowalchuk, J. R. Stephen, W. D. Boer, J. I. Prosser, T. M. Embley, and J. W. Woldendorp, Appl. Environ. Microbiol.
63:
1489-1497, 1997) were shown not to be completely specific to AOB of the β subclass of
Proteobacteria
. We further demonstrated that when DGGE patterns are interpreted, all the different bands must be sequenced, as one major DGGE band proved to be affiliated with a group of non-AOB in the β subclass of
Proteobacteria
. The majority of AOB (75 to 90%) present in the lower Seine river downstream of the effluent output belong to lineage 6a, represented by
Nitrosomonas oligotropha-
and
Nitrosomonas ureae
-like bacteria. This dominant lineage was represented by three bands on the DGGE gel. The major lineage-6a AOB species, introduced by the WWTP effluents, survived and might have grown in the receiving medium far downstream, in the estuary; it represented about 40% of the whole AOB population. The other two species belonging to lineage 6a seem to be autochthonous bacteria. One of them developed a few kilometers downstream of the WWTP effluent input in an ammonia-enriched environment, and the other appeared in the freshwater part of the estuary and was apparently more adapted to estuarine conditions, i.e., an increase in the amount of suspended matter, a low ammonia concentration, and high turnover of organic matter. The rest of the AOB population was represented in equal proportions by
Nitrosospira
- and
Nitrosococcus mobilis
-like species.
Bacterial Diversity and Function of Aerobic Granules Engineered in a Sequencing Batch Reactor for Phenol Degradation
Authors: Jiang He-Long , Tay Joo-Hwa , Maszenan Abdul Majid , Tay Stephen Tiong-Lee 
Published: November 2004

ABSTRACT

Aerobic granules are self-immobilized aggregates of microorganisms and represent a relatively new form of cell immobilization developed for biological wastewater treatment. In this study, both culture-based and culture-independent techniques were used to investigate the bacterial diversity and function in aerobic phenol- degrading granules cultivated in a sequencing batch reactor. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes demonstrated a major shift in the microbial community as the seed sludge developed into granules. Culture isolation and DGGE assays confirmed the dominance of β-
Proteobacteria
and high-G+C gram-positive bacteria in the phenol-degrading aerobic granules. Of the 10 phenol-degrading bacterial strains isolated from the granules, strains PG-01, PG-02, and PG-08 possessed 16S rRNA gene sequences that matched the partial sequences of dominant bands in the DGGE fingerprint belonging to the aerobic granules. The numerical dominance of strain PG-01 was confirmed by isolation, DGGE, and in situ hybridization with a strain-specific probe, and key physiological traits possessed by PG-01 that allowed it to outcompete and dominate other microorganisms within the granules were then identified. This strain could be regarded as a functionally dominant strain and may have contributed significantly to phenol degradation in the granules. On the other hand, strain PG-08 had low specific growth rate and low phenol degradation ability but showed a high propensity to autoaggregate. By analyzing the roles played by these two isolates within the aerobic granules, a functional model of the microbial community within the aerobic granules was proposed. This model has important implications for rationalizing the engineering of ecological systems.
Poly(3-Hydroxybutyrate) Biosynthesis in the Biofilm of
Alcaligenes eutrophus
, Using Glucose Enzymatically Released from Pulp Fiber Sludge
Authors: Zhang Songping , Norrlöw Olof , Wawrzynczyk Joanna , Dey Estera Szwajcer 
Published: November 2004

ABSTRACT

Glucose, enzymatically released from pulp fiber sludge, was combined with inorganic salts and used as a growth medium for
Alcaligenes eutrophus
, a gram-negative strain producing poly(3-hydroxybutyrate) (PHB). By controlling the concentrations of the inorganic salts in the growth medium, almost 78% of the cell mass was converted to pure PHB. Efforts were made to find conditions for bacterial growth in the form of a biofilm on a cheap and reusable carrier. A number of positively charged carriers were tested, and the anion exchanger DEAE-Sephadex A-25 was chosen as a microcarrier for packed-bed biofilm cultures of
A. eutrophus.
Conditions for attachment, growth, and detachment were established. Biofilm formation on the microcarrier is strongly dependent on the ionic strength of the attachment medium. In order to achieve formation of the biofilm and its recovery from the microcarrier, the ionic strengths of the attachment and the detachment media were varied. Low ionic strength was tested for attachment, and high ionic strength was tested for detachment. Although biofilm formation in the packed-bed reactor is limited, the volumetric yield of cells based on the void volume of the packed bed is comparable with the batch culture yield.
Interaction and Transmission of Two
Borrelia burgdorferi
Sensu Stricto Strains in a Tick-Rodent Maintenance System
Authors: Derdáková Markéta , Dudiòák Vladimír , Brei Brandon , Brownstein John S. , Schwartz Ira , Fish Durland 
Published: November 2004

ABSTRACT

In the northeastern United States, the Lyme disease agent,
Borrelia burgdorferi
sensu stricto, is maintained by enzoonotic transmission, cycling between white-footed mice (
Peromyscus leucopus
) and black-legged ticks (
Ixodes scapularis
).
B. burgdorferi
sensu stricto is genetically variable and has been divided into three major genotypes based on 16S-23S ribosomal DNA spacer (RST) analysis. To better understand how genetic differences in
B. burgdorferi
sensu stricto may influence transmission dynamics in nature, we investigated the interaction between an RST1 and an RST3 strain in a laboratory system with
P. leucopus
mice and
I. scapularis
ticks. Two groups of mice were infected with either BL206 (RST1) or B348 (RST3). Two weeks later, experimental mice were challenged with the opposite strain, while control mice were challenged with the same strain as that used for the primary infection. The transmission of BL206 and B348 from infected mice was then determined by xenodiagnosis with uninfected larval ticks at weekly intervals for 42 days. Mice in both experimental groups were permissive for infection with the second strain and were able to transmit both strains to the xenodiagnostic ticks. However, the overall transmission efficiencies of BL206 and B348 were significantly different. BL206 was more efficiently transmitted than B348 to xenodiagnostic ticks. Significantly fewer double infections than expected were detected in xenodiagnostic ticks. The results suggest that some
B. burgdorferi
sensu stricto strains, such as BL206, may be preferentially maintained in transmission cycles between ticks and white-footed mice. Other strains, such as B348, may be more effectively maintained in different tick-vertebrate transmission cycles.