bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic regulation and overproduction of primary metabolites
Authors: Sanchez Sergio , Demain Arnold L.
Published: February 2008

Overproduction of microbial metabolites is related to developmental phases of microorganisms. Inducers, effectors, inhibitors and various signal molecules play a role in different types of overproduction. Biosynthesis of enzymes catalysing metabolic reactions in microbial cells is controlled by well‐known positive and negative mechanisms, e.g. induction, nutritional regulation (carbon or nitrogen source regulation), feedback regulation, etc. The microbial production of primary metabolites contributes significantly to the quality of life. Fermentative production of these compounds is still an important goal of modern biotechnology. Through fermentation, microorganisms growing on inexpensive carbon and nitrogen sources produce valuable products such as amino acids, nucleotides, organic acids and vitamins which can be added to food to enhance its flavour, or increase its nutritive values. The contribution of microorganisms goes well beyond the food and health industries with the renewed interest in solvent fermentations. Microorganisms have the potential to provide many petroleum‐derived products as well as the ethanol necessary for liquid fuel. Additional applications of primary metabolites lie in their impact as precursors of many pharmaceutical compounds. The roles of primary metabolites and the microbes which produce them will certainly increase in importance as time goes on. In the early years of fermentation processes, development of producing strains initially depended on classical strain breeding involving repeated random mutations, each followed by screening or selection. More recently, methods of molecular genetics have been used for the overproduction of primary metabolic products. The development of modern tools of molecular biology enabled more rational approaches for strain improvement. Techniques of transcriptome, proteome and metabolome analysis, as well as metabolic flux analysis. have recently been introduced in order to identify new and important target genes and to quantify metabolic activities necessary for further strain improvement.
Old Paths and New Directions: Studying Emotions in the Workplace
Authors: Meanwell Emily , Wolfe Joseph D. , Hallett Tim
Published: February 2008

The study of emotions in the workplace is a vibrant area of research that has grown considerably over the last 25 years. This research has traveled far, but it has not run its course. This article maps the different paths that have been explored, beginning with Hochschild's classic work on emotional labor in the form of surface and deep acting, and charts new directions for future research. We start by reviewing the literature on emotional labor and emotion management in the workplace. Next, we discuss new theoretical developments in the sociology of emotions – interaction ritual chain theory, theories of identity and affect control, and theories about power, status, and exchange – and their potential utility for understanding emotions at work. Finally, we discuss new methodological directions that can be pursued in future research on emotions in work and organizational settings.
The angiotensin receptor type 1–Gqprotein–phosphatidyl inositol phospholipase Cβ–protein kinase C pathway is involved in activation of proximal tubule Na+‐ATPase activity by angiotensin(1–7) in pig kidneys
Authors: Lara Lucienne S. , Correa Juliana S. , Lavelle Anouchka B. , Lopes Anibal G. , Caruso‐Neves Celso
Published: February 2008

In a previous study, we observed that angiotensin(1–7) (Ang(1–7)) stimulates proximal tubule Na+‐ATPase activity through the angiotensin receptor type 1 (AT1R). Here we aimed to study the signalling pathways involved. Our results show that the stimulatory effect of Ang(1–7) on Na+‐ATPase activity through AT1R involves a Gqprotein–phosphatidyl inositol‐phospholipase Cβ(PI‐PLCβ) pathway because: (1) the effect was reversed by GDPβS, a non‐hydrolysable GDP analogue, and by a monoclonal Gqprotein antibody; (2) the effect was similar and not additive to that of GTPγS, a non‐hydrolysable GTP analogue; (3) Ang(1–7) induced a rapid decrease (30 s) in phosphatidylinositol 4,5‐bisphosphate levels, a PI‐PLCβ substrate; and (4) U73122, a specific inhibitor of PI‐PLCβ, abolished Ang(1–7)‐induced stimulation of Na+‐ATPase activity. Angiotensin(1–7) increased the protein kinase C (PKC) activity similarly to phorbol‐12‐myristate‐13‐acetate (PMA), an activator of PKC. This effect was reversed by losartan, a specific antagonist of AT1R. The stimulatory effects of Ang(1–7) and PMA on Na+‐ATPase activity are similar, non‐additive and reversed by calphostin C, a specific inhibitor of PKC. A catalytic subunit of PKC (PKC‐M) increased the Na+‐ATPase activity. These data show that Ang(1–7) stimulates Na+‐ATPase activity through the AT1R–Gqprotein–PI‐PLCβ–PKC pathway. This effect is similar to that described for angiotensin II, showing for the first time that these compounds could have similar effects in the renal system.
Influence of prior exercise on muscle [phosphorylcreatine] and deoxygenation kinetics during high‐intensity exercise in men
Authors: Jones Andrew M. , Fulford Jonathan , Wilkerson Daryl P.
Published: February 2008

31Phosphate‐magnetic resonance spectroscopy and near infrared spectroscopy (NIRS) were used for the simultaneous assessment of changes in quadriceps muscle metabolism and oxygenation during consecutive bouts of high‐intensity exercise. Six male subjects completed two 6 min bouts of single‐legged knee‐extension exercise at 80% of the peak work rate separated by 6 min of rest while positioned inside the bore of a 1.5 T superconducting magnet. The total haemoglobin and oxyhaemoglobin concentrations in the area of the quadriceps muscle interrogated with NIRS were significantly higher in the baseline period prior to the second compared with the first exercise bout, consistent with an enhanced muscle oxygenation. Intramuscular phosphorylcreatine concentration ([PCr]) dynamics were not different over the fundamental region of the response (time constant for bout 1, 51 ± 15 s versus bout 2, 52 ± 17 s). However, the [PCr] dynamics over the entire response were faster in the second bout (mean response time for bout 1, 72 ± 16 s versus bout 2, 57 ± 8 s; P < 0.05), as a consequence of a greater fall in [PCr] in the fundamental phase and a reduction in the magnitude of the ‘slow component’ in [PCr] beyond 3 min of exercise (bout 1, 10 ± 6%versus bout 2, 5 ± 3%; P < 0.05). These data suggest that the increased muscle O2 availability afforded by the performance of a prior bout of high‐intensity exercise does not significantly alter the kinetics of [PCr] hydrolysis at the onset of a subsequent bout of high‐intensity exercise. The greater fall in [PCr] over the fundamental phase of the response following prior high‐intensity exercise indicates that residual fatigue acutely reduces muscle efficiency.
Higher-order acoustic diffraction by edges of finite thickness
Authors: Chu Dezhang , Stanton Timothy K. , Pierce Allan D.
Published: February 2008

A cw solution of acoustic diffraction by a three-sided semi-infinite barrier or a double edge, where the width of the midplanar segment is finite and cannot be ignored, involving all orders of diffraction is presented. The solution is an extension of the asymptotic formulas for the double-edge second-order diffraction via amplitude and phase matching given by Pierce [A. D. Pierce, J. Acoust. Soc. Am. 55, 943–955 (1974)]. The model accounts for all orders of diffraction and is valid for all kw, where k is the acoustic wave number and w is the width of the midplanar segment and reduces to the solution of diffraction by a single knife edge as w→0. The theory is incorporated into the deformed edge solution [Stanton et al., J. Acoust. Soc. Am. 122, 3167 (2007)] to model the diffraction by a disk of finite thickness, and is compared with laboratory experiments of backscattering by elastic disks of various thicknesses and by a hard strip. It is shown that the model describes the edge diffraction reasonably well in predicting the diffraction as a function of scattering angle, edge thickness, and frequency.
Comparing stimulus-frequency otoacoustic emissions measured by compression, suppression, and spectral smoothing
Authors: Kalluri Radha , Shera Christopher A.
Published: February 2008

Stimulus-frequency otoacoustic emissions (SFOAEs) have been measured in several different ways, including (1) nonlinear compression, (2) two-tone suppression, and (3) spectral smoothing. Each of the three methods exploits a different cochlear phenomenon or signal-processing technique to extract the emission. The compression method makes use of the compressive growth of emission amplitude relative to the linear growth of the stimulus. The emission is defined as the complex difference between ear-canal pressure measured at one intensity and the rescaled pressure measured at a higher intensity for which the emission is presumed negligible. The suppression method defines the SFOAE as the complex difference between the ear-canal pressure measured with and without a suppressor tone at a nearby frequency. The suppressor tone is presumed to substantially reduce or eliminate the emission. The spectral smoothing method involves convolving the complex ear-canal pressure spectrum with a smoothing function. The analysis exploits the differing latencies of stimulus and emission and is equivalent to windowing in the corresponding latency domain. Although the three methods are generally assumed to yield identical emissions, no equivalence has ever been established. This paper compares human SFOAEs measured with the three methods using procedures that control for temporal drifts, contamination of the calibration by evoked emissions, and other potential confounds. At low stimulus intensities, SFOAEs measured using all three methods are nearly identical. At higher intensities, limitations of the procedures contribute to small differences, although the general spectral shape and phase of the three SFOAEs remain similar. The near equivalence of SFOAEs measured by compression, suppression, and spectral smoothing indicates that SFOAE characteristics are not mere artifacts of measurement methodology.
Analytic mode matching for a circular dissipative silencer containing mean flow and a perforated pipe
Authors: Kirby Ray , Denia Francisco D.
Published: February 2008

An analytic mode matching scheme that includes higher order modes is developed for a straight-through circular dissipative silencer. Uniform mean flow is added to the central airway and a concentric perforated screen separates the mean flow from a bulk reacting porous material. Transmission loss predictions are compared with experimental measurements and good agreement is demonstrated for three different silencers. Furthermore, it is demonstrated that, when mean flow is present, the axial kinematic matching condition should equate to that chosen for the radial kinematic boundary condition over the interface between the airway and the material. Accordingly, if the radial matching conditions are continuity of pressure and displacement, then the axial matching conditions should also be continuity of pressure and displacement, rather than pressure and velocity as previously thought. When a perforated screen is present the radial pressure condition changes, but the radial kinematic condition should always remain equivalent to that chosen for the axial kinematic matching condition; here, results indicate that continuity of displacement should be retained when a perforated screen is present.
Spectral integration and wideband analysis in gap detection and overshoot paradigms
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: February 2008

Several listening conditions show that energy remote from a target frequency can deleteriously affect sensitivity. One interpretation of such results entails a wideband analysis involving a wide predetection filter. The present study tested the hypothesis that both temporal gap detection and overshoot results are consistent with a wideband analysis, as contrasted with statistical combination of information across independent channels. For gap detection, stimuli were random or comodulated 50-Hz-wide noise bands centered on 1000, 1932, 3569, and 6437Hz. For overshoot, the masker was an 8-kHz low-pass filtered noise, with 5-ms tone bursts presented at the same center frequencies used for gap detection. Signals were presented with either 0- or 250-ms delay after masker onset. In each paradigm, the target was introduced at only one frequency or at all four frequencies. Results from gap detection conditions did not favor a wideband analysis interpretation: Results in the random condition were consistent with an optimal combination of cues across frequency. An across-channel interference effect was also evident when only one of the four bands contained the gap. Although results from the overshoot conditions were consistent with a wideband analysis interpretation, they were more parsimoniously accounted for in terms of statistical combination of information.
On the one-dimensional acoustic propagation in conical ducts with stationary mean flow
Authors: Barjau Ana
Published: February 2008

This paper proposes a direct time-domain calculation of the time-domain responses of anechoic conical tubes with steady weak mean flow. The starting point is the approximated linear one-dimensional wave equation governing the velocity potential for the case of steady flow with low Mach number. A traveling solution with general space-dependent propagation velocity is then proposed from which the inward and outward pressure and velocity impulse responses can be obtained. The results include the well-known responses of conical and cylindrical ducts with zero mean flow.
Application of metrics constructed from vibrotactile thresholds to the assessment of tactile sensory changes in the hands
Authors: Brammer A. J. , Sutinen P. , Diva U. A. , Pyykkö I. , Toppila E. , Starck J.
Published: February 2008

Two tools for assessing tactile sensory disturbances in the hands have been constructed from mechanoreceptor-specific vibrotactile threshold shifts, and thresholds changes with time, and employed in a prospective study of forest workers (N=18). Statistically significant positive threshold shifts (i.e., reductions in sensitivity compared to the hands of healthy persons) were found in five hands at study inception (13.9%), and 15 hands at follow-up (41.7%). Four patterns of threshold shift could be identified, involving selectively the median and/or ulnar nerve pathways and/or end organs. Statistically significant positive threshold changes (i.e., reductions in sensitivity with time) were recorded in 69.4% of the hands over a five-year period, even though a majority of the workers remained symptom free. If the thresholds recorded from subjects not working with power tools are used to control for aging, lifestyle, and environmental factors during the five year period, then 40% of the remaining subjects are found to be experiencing work-related threshold changes in their hands. The ability of the threshold shift metric to predict the numbness reported by these subjects shows that it is closely associated with the tactile sensory changes occurring in their hands.
Evaluating noise in social context: The effect of procedural unfairness on noise annoyance judgments
Authors: Maris Eveline , Stallen Pieter J. , Vermunt Riel , Steensma Herman
Published: February 2008

General dosage-response curves typically over- or underestimate the actual prevalence of noise annoyance for specific groups of individuals. The present study applies a social psychological approach to noise annoyance that helps to understand and predict collective deflections from the curve. The approach holds that being exposed to man-made sound is more than mere exposure; it is a social experience, too: You expose Me. In effect, social aspects of the situation, like the evaluation of the sound management procedure, influence the evaluation of sound. The laboratory experiment (N=90) investigates the effect of procedural unfairness on noise annoyance. The sound management procedure is varied systematically: Participants are promised they will listen to the sound of their choice (i.e., bird song, radio sound, or aircraft sound) but receive aircraft sound despite their expressed preference (unfair procedure), or they are simply told they will listen to aircraft sound (neutral procedure). All are exposed to aircraft sound (50 or 70dBA Leq). A collective rise in noise annoyance is predicted in the unfair relative to the neutral procedure conditions. Results show that noise annoyance ratings are significantly higher in the unfair relative to the neutral conditions. Consequences for theory and practice are discussed.
Short- and long-term changes in right whale calling behavior: The potential effects of noise on acoustic communication
Authors: Parks Susan E. , Clark C. W. , Tyack P. L.
Published: February 2008

The impact of anthropogenic noise on marine mammals has been an area of increasing concern over the past two decades. Most low-frequency anthropogenic noise in the ocean comes from commercial shipping which has contributed to an increase in ocean background noise over the past 150 years. The long-term impacts of these changes on marine mammals are not well understood. This paper describes both short- and long-term behavioral changes in calls produced by the endangered North Atlantic right whale (Eubalaena glacialis) and South Atlantic right whale (Eubalaena australis) in the presence of increased low-frequency noise. Right whales produce calls with a higher average fundamental frequency and they call at a lower rate in high noise conditions, possibly in response to masking from low-frequency noise. The long-term changes have occurred within the known lifespan of individual whales, indicating that a behavioral change, rather than selective pressure, has resulted in the observed differences. This study provides evidence of a behavioral change in sound production of right whales that is correlated with increased noise levels and indicates that right whales may shift call frequency to compensate for increased band-limited background noise.
Packaging of Live
Legionella pneumophila
into Pellets Expelled by
Tetrahymena
spp. Does Not Require Bacterial Replication and Depends on a Dot/Icm-Mediated Survival Mechanism
Authors: Berk Sharon G. , Faulkner Gary , Garduño Elizabeth , Joy Mark C. , Ortiz-Jimenez Marco A. , Garduño Rafael A.
Published: February 2008

The freshwater ciliate
Tetrahymena
sp. efficiently ingested, but poorly digested, virulent strains of the gram-negative intracellular pathogen
Legionella pneumophila
. Ciliates expelled live legionellae packaged in free spherical pellets. The ingested legionellae showed no ultrastructural indicators of cell division either within intracellular food vacuoles or in the expelled pellets, while the number of CFU consistently decreased as a function of time postinoculation, suggesting a lack of
L. pneumophila
replication inside
Tetrahymena
. Pulse-chase feeding experiments with fluorescent
L. pneumophila
and
Escherichia coli
indicated that actively feeding ciliates maintain a rapid and steady turnover of food vacuoles, so that the intravacuolar residence of the ingested bacteria was as short as 1 to 2 h.
L. pneumophila
mutants with a defective Dot/Icm virulence system were efficiently digested by
Tetrahymena
sp. In contrast to pellets of virulent
L. pneumophila
, the pellets produced by ciliates feeding on
dot
mutants contained very few bacterial cells but abundant membrane whorls. The whorls became labeled with a specific antibody against
L. pneumophila
OmpS, indicating that they were outer membrane remnants of digested legionellae. Ciliates that fed on genetically complemented
dot
mutants produced numerous pellets containing live legionellae, establishing the importance of the Dot/Icm system to resist digestion. We thus concluded that production of pellets containing live virulent
L. pneumophila
depends on bacterial survival (mediated by the Dot/Icm system) and occurs in the absence of bacterial replication. Pellets of virulent
L. pneumophila
may contribute to the transmission of Legionnaires’ disease, an issue currently under investigation.
Abundances and Distributions of the Dominant
nifH
Phylotypes in the Northern Atlantic Ocean
Authors: Langlois Rebecca J. , Hümmer Diana , LaRoche Julie
Published: February 2008

Understanding the factors that influence the distribution and abundance of marine diazotrophs is important in order to assess their role in the oceanic nitrogen cycle. Environmental DNA samples from four cruises to the North Atlantic Ocean, covering a sampling area of 0°N to 42°N and 67°W to 13°W, were analyzed for the presence and amount of seven
nifH
phylotypes using real-time quantitative PCR and TaqMan probes. The cyanobacterial phylotypes dominated in abundance (94% of all
nifH
copies detected) and were the most widely distributed. The filamentous cyanobacterial type, which included both
Trichodesmium
and
Katagnymene
, was the most abundant (51%), followed by group A, an uncultured unicellular cyanobacterium (33%), and gamma A, an uncultured gammaproteobacterium (6%). Group B, unicellular cyanobacterium
Crocosphaera
, and group C
Cyanothece
-like phylotypes were not often detected (6.9% and 2.3%, respectively), but where present, could reach high concentrations. Gamma P, another uncultured gammaproteobacterium, was seldom detected (0.5%). Water temperature appeared to influence the distribution of many
nifH
phylotypes. Very high (up to 1 × 10
6
copies liter
−1
)
nifH
concentrations of group A were detected in the eastern basin (25 to 17°N, 27 to 30°W), where the temperature ranged from 20 to 23°C. The highest concentrations of filamentous phylotypes were measured between 25 and 30°C. The uncultured cluster III phylotype was uncommon (0.4%) and was associated with mean water temperatures of 18°C. Diazotroph abundance was highest in regions where modeled average dust deposition was between 1 and 2 g/m
2
/year.
Construction of Sterileime1Δ-TransgenicSaccharomyces cerevisiaeWine Yeasts Unable To Disseminate in Nature
Authors: Ramírez Manuel , Ambrona Jesús
Published: February 2008

The use of new transgenic yeasts in industry carries a potential environmental risk because their dispersal, introducing new artificial genetic combinations into nature, could have unpredictable consequences. This risk could be avoided by using sterile transgenic yeasts that are unable to sporulate and mate with wild yeasts. These sterile yeasts would not survive the annual cyclic harvesting periods, being condemned to disappear in the wineries and vineyards in less than a year. We have constructed newime1Δwine yeasts that are unable to sporulate and mate, bear easy-to-detect genetic markers, and quickly disappear in grape must fermentation immediately after sporulation of the yeast population. These sterile yeasts maintained the same biotechnological properties as their parent yeasts without any detectable deleterious effect of theime1Δmutation. These yeasts are therefore interesting biotechnologically for food industry applications and for genetically modified microorganism environmental monitoring studies.
Activation of the Diacetyl/Acetoin Pathway in
Lactococcus lactis
subsp.
lactis
bv. diacetylactis CRL264 by Acidic Growth
Authors: García-Quintáns Nieves , Repizo Guillermo , Martín Mauricio , Magni Christian , López Paloma
Published: February 2008

Lactococcus lactis
subsp.
lactis
bv. diacetylactis strains are aroma-producing organisms used in starter cultures for the elaboration of dairy products. This species is essentially a fermentative microorganism, which cometabolizes glucose and citrate to yield aroma compounds through the diacetyl/acetoin biosynthetic pathway. Our previous results have shown that under acidic growth
Lactococcus
bv. diacetylactis CRL264 expresses coordinately the genes responsible for citrate transport and its conversion into pyruvate. In the present work the impact of acidic growth on glucose, citrate, and pyruvate metabolism of
Lactococcus
bv. diacetylactis CRL264 has been investigated by proteomic analysis. The results indicated that acid growth triggers the conversion of citrate, but not glucose, into α-acetolactate via pyruvate. Moreover, they showed that low pH has no influence on levels of lactate dehydrogenase and pyruvate dehydrogenase. Therefore, the influence of external pH on regulation of the diacetyl/acetoin biosynthetic pathway in
Lactococcus
bv. diacetylactis CRL264 has been analyzed at the transcriptional level. Expression of the
als
,
aldB
,
aldC
, and
butBA
genes encoding the enzymes involved in conversion of pyruvate into aroma compounds has been investigated by primer extension, reverse transcription-PCR analysis, and transcriptional fusions. The results support that this biosynthetic pathway is induced at the transcriptional level by acidic growth conditions, presumably contributing to lactococcal pH homeostasis by synthesis of neutral compounds and by decreasing levels of pyruvate.
Antibacterial Activity and Mechanism of Action of the Silver Ion in
Staphylococcus aureus
and
Escherichia coli
Authors: Jung Woo Kyung , Koo Hye Cheong , Kim Ki Woo , Shin Sook , Kim So Hyun , Park Yong Ho
Published: February 2008

The antibacterial effect and mechanism of action of a silver ion solution that was electrically generated were investigated for
Staphylococcus aureus
and
Escherichia coli
by analyzing the growth, morphology, and ultrastructure of the bacterial cells following treatment with the silver ion solution. Bacteria were exposed to the silver ion solution for various lengths of time, and the antibacterial effect of the solution was tested using the conventional plate count method and flow cytometric (FC) analysis. Reductions of more than 5 log
10
CFU/ml of both
S. aureus
and
E. coli
bacteria were confirmed after 90 min of treatment with the silver ion solution. Significant reduction of
S. aureus
and
E. coli
cells was also observed by FC analysis; however, the reduction rate determined by FC analysis was less than that determined by the conventional plate count method. These differences may be attributed to the presence of bacteria in an active but nonculturable (ABNC) state after treatment with the silver ion solution. Transmission electron microscopy showed considerable changes in the bacterial cell membranes upon silver ion treatment, which might be the cause or consequence of cell death. In conclusion, the results of the present study suggest that silver ions may cause
S. aureus
and
E. coli
bacteria to reach an ABNC state and eventually die.
Autoinducer-2 Triggers the Oxidative Stress Response in
Mycobacterium avium
, Leading to Biofilm Formation
Authors: Geier Henriette , Mostowy Serge , Cangelosi Gerard A. , Behr Marcel A. , Ford Timothy E.
Published: February 2008

Mycobacterium avium
is an environmental organism and opportunistic pathogen with inherent resistance to drugs, environmental stresses, and the host immune response. To adapt to these disparate conditions,
M. avium
must control its transcriptional response to environmental cues.
M. avium
forms biofilms in various environmental settings, including drinking water pipes and potable water reservoirs. In this study, we investigated the role of the universal signaling molecule autoinducer-2 (AI-2) in biofilm formation by
M. avium
. The addition of the compound to planktonic
M. avium
cultures resulted in increased biofilm formation. Microarray and reverse transcriptase PCR studies revealed an upregulation of the oxidative stress response upon addition of AI-2. This suggests that the response to AI-2 might be related to oxidative stress, rather than quorum sensing. Consistent with this model, addition of hydrogen peroxide, a known stimulus of the oxidative stress response, to
M. avium
cultures resulted in elevated biofilm formation. These results suggest that AI-2 does not act as a quorum-sensing signal in
M. avium
. Instead, biofilm formation is triggered by environmental stresses of biotic and abiotic origins and AI-2 may exert effects on that level.
Survival of Gastric and Enterohepatic
Helicobacter
spp. in Water: Implications for Transmission
Authors: Azevedo N. F. , Almeida C. , Fernandes I. , Cerqueira L. , Dias S. , Keevil C. W. , Vieira M. J.
Published: February 2008

Part of the reason for rejecting aquatic environments as possible vectors for the transmission of
Helicobacter pylori
has been the preference of this microorganism to inhabit the human stomach and hence use a direct oral-oral route for transmission. On the other hand, most enteric bacterial pathogens are well known for being able to use water as an environmental reservoir. In this work, we have exposed 13 strains of seven different
Helicobacter
spp. (both gastric and enterohepatic) to water and tracked their survival by standard plating methods and membrane integrity assessment. The influence of different plating media and temperatures and the presence of light on recovery was also assessed. There was good correlation between cultivability and membrane integrity results (Pearson's correlation coefficient = 0.916), confirming that the culture method could reliably estimate differences in survival among different
Helicobacter
spp. The species that survived the longest in water was
H. pylori
(>96 h in the dark at 25°C), whereas
H. felis
appeared to be the most sensitive to water (<6 h). A hierarchical cluster analysis demonstrated that there was no relationship between the enterohepatic nature of
Helicobacter
spp. and an increased time of survival in water. This work assesses for the first time the survival of multiple
Helicobacter
spp., such has
H. mustelae
,
H. muridarum
,
H. felis
,
H. canadensis
,
H. pullorum
, and
H. canis
, in water under several conditions and concludes that the roles of water in transmission between hosts are likely to be similar for all these species, whether enterohepatic or not.
Genomic and Genetic Characterization of the Bile Stress Response of ProbioticLactobacillus reuteriATCC 55730
Authors: Whitehead Kristi , Versalovic James , Roos Stefan , Britton Robert A.
Published: February 2008

Probiotic bacteria encounter various stresses after ingestion by the host, including exposure to the low pH in the stomach and bile in the small intestine. The probiotic microorganismLactobacillus reuteriATCC 55730 has previously been shown to survive in the human small intestine. To address howL. reuterican resist bile stress, we performed microarray experiments to determine gene expression changes that occur when the organism is exposed to physiological concentrations of bile. A wide variety of genes that displayed differential expression in the presence of bile indicated that the cells were dealing with several types of stress, including cell envelope stress, protein denaturation, and DNA damage. Mutations in three genes were found to decrease the strain's ability to survive bile exposure: lr1864, a Clp chaperone; lr0085, a gene of unknown function; and lr1516, a putative esterase. Mutations in two genes that form an operon, lr1584 (a multidrug resistance transporter in the major facilitator superfamily) and lr1582 (unknown function), were found to impair the strain's ability to restart growth in the presence of bile. This study provides insight into the possible mechanisms thatL. reuteriATCC 55730 may use to survive and grow in the presence of bile in the small intestine.
Inactivation and UV Disinfection of Murine Norovirus with TiO
2
under Various Environmental Conditions
Authors: Lee JungEun , Zoh KyungDuk , Ko GwangPyo
Published: February 2008

We studied inactivation and UV disinfection of murine norovirus (MNV) as a surrogate for human norovirus. We investigated the effects of different surface characteristics, temperatures, and NaCl concentrations on MNV survival using both a plaque assay and a real-time TaqMan reverse transcription (RT)-PCR assay. MNV survived more than 40 days on diaper material, on gauze, and in a stool suspension. Compared to inactivation at lower temperatures (−20 and 4°C), inactivation of MNV was greater at higher temperatures (18 and 30°C). On the surface of both gauze and diaper material, there was a <2-log
10
reduction in the amount of infectious MNV in 40 days after incubation at both −20 and 4°C, compared to a >5-log
10
reduction after incubation at 30°C in 24 days. MNV survived better in a stool suspension than on the surface of gauze or diaper material. A higher salt concentration increased the rate of inactivation of MNV. In 72 h, <0.3-, 1.5-, and 2.5-log
10
reductions in the amount of infectious MNV occurred in distilled water and 0.5 and 1 M NaCl, respectively. We observed only minor reductions in the numbers of viral RNA copies as quantified by real-time TaqMan RT-PCR regardless of the temperature, the salt concentration, or the suspending medium. We also evaluated UV disinfection of infectious MNV with and without TiO
2
. The amount of MNV was significantly reduced by 254-nm UV with and without TiO
2
. When 25 mJ/cm
2
UV was used, 3.3- and 3.6-log
10
reductions in the amounts of infectious MNV occurred with and without TiO
2
, respectively. Our results demonstrate that MNV can persist in various environmental conditions and can be efficiently controlled by UV disinfection.
Use of In Vivo
13
C Nuclear Magnetic Resonance Spectroscopy To Elucidate
l
-Arabinose Metabolism in Yeasts
Authors: Fonseca César , Neves Ana Rute , Antunes Alexandra M. M. , Noronha João Paulo , Hahn-Hägerdal Bärbel , Santos Helena , Spencer-Martins Isabel
Published: February 2008

Candida arabinofermentans
PYCC 5603
T
and
Pichia guilliermondii
PYCC 3012 were shown to grow well on
l
-arabinose, albeit exhibiting distinct features that justify an in-depth comparative study of their respective pentose catabolism. Carbon-13 labeling experiments coupled with in vivo nuclear magnetic resonance (NMR) spectroscopy were used to investigate
l
-arabinose metabolism in these yeasts, thereby complementing recently reported physiological and enzymatic data. The label supplied in
l
-[2-
13
C]arabinose to nongrowing cells, under aerobic conditions, was found on C-1 and C-2 of arabitol and ribitol, on C-2 of xylitol, and on C-1, C-2, and C-3 of trehalose. The detection of labeled arabitol and xylitol constitutes additional evidence for the operation in yeast of the redox catabolic pathway, which is widespread among filamentous fungi. Furthermore, labeling at position C-1 of trehalose and arabitol demonstrates that glucose-6-phosphate is recycled through the oxidative pentose phosphate pathway (PPP). This result was interpreted as a metabolic strategy to regenerate NADPH, the cofactor essential for sustaining
l
-arabinose catabolism at the level of
l
-arabinose reductase and
l
-xylulose reductase. Moreover, the observed synthesis of
d
-arabitol and ribitol provides a route with which to supply NAD
+
under oxygen-limiting conditions. In
P. guilliermondii
PYCC 3012, the strong accumulation of
l
-arabitol (intracellular concentration of up to 0.4 M) during aerobic
l
-arabinose metabolism indicates the existence of a bottleneck at the level of
l
-arabitol 4-dehydrogenase. This report provides the first experimental evidence for a link between
l
-arabinose metabolism in fungi and the oxidative branch of the PPP and suggests rational guidelines for the design of strategies for the production of new and efficient
l
-arabinose-fermenting yeasts.
Cinnamic Acid, an Autoinducer of Its Own Biosynthesis, Is Processed via Hca Enzymes in
Photorhabdus luminescens
Authors: Chalabaev Sabina , Turlin Evelyne , Bay Sylvie , Ganneau Christelle , Brito-Fravallo Emma , Charles Jean-François , Danchin Antoine , Biville Francis
Published: February 2008

Photorhabdus luminescens
, an entomopathogenic bacterium and nematode symbiont, has homologues of the Hca and Mhp enzymes. In
Escherichia coli
, these enzymes catalyze the degradation of the aromatic compounds 3-phenylpropionate (3PP) and cinnamic acid (CA) and allow the use of 3PP as sole carbon source.
P. luminescens
is not able to use 3PP and CA as sole carbon sources but can degrade them. Hca dioxygenase is involved in this degradation pathway.
P. luminescens
synthesizes CA from phenylalanine via a phenylalanine ammonia-lyase (PAL) and degrades it via the not-yet-characterized biosynthetic pathway of 3,5-dihydroxy-4-isopropylstilbene (ST) antibiotic. CA induces its own synthesis by enhancing the expression of the
stlA
gene that codes for PAL.
P. luminescens
bacteria release endogenous CA into the medium at the end of exponential growth and then consume it. Hca dioxygenase is involved in the consumption of endogenous CA but is not required for ST production. This suggests that CA is consumed via at least two separate pathways in
P. luminescens
: the biosynthesis of ST and a pathway involving the Hca and Mhp enzymes.
Molecular Analysis of Shiga Toxin-Producing
Escherichia coli
Strains Isolated from Hemolytic-Uremic Syndrome Patients and Dairy Samples in France
Authors: Pradel Nathalie , Bertin Yolande , Martin Christine , Livrelli Valérie
Published: February 2008

Shiga toxin-producing
Escherichia coli
(STEC) has been associated with food-borne diseases ranging from uncomplicated diarrhea to hemolytic-uremic syndrome (HUS). While most outbreaks are associated with
E. coli
O157:H7, about half of the sporadic cases may be due to non-O157:H7 serotypes. To assess the pathogenicity of STEC isolated from dairy foods in France, 40 strains isolated from 1,130 raw-milk and cheese samples were compared with 15 STEC strains isolated from patients suffering from severe disease. The presence of genes encoding Shiga toxins (
stx
1
,
stx
2
, and variants), intimin (
eae
and variants), adhesins (
bfp
,
efa1
), enterohemolysin (
ehxA
), serine protease (
espP
), and catalase-peroxidase (
katP
) was determined by PCR and/or hybridization. Plasmid profiling, ribotyping, and pulsed-field gel electrophoresis (PFGE) were used to further compare the strains at the molecular level. A new
stx
2
variant,
stx
2-CH013
, associated with an O91:H10 clinical isolate was identified. The presence of the
stx
2
,
eae
, and
katP
genes, together with a combination of several
stx
2
variants, was clearly associated with human-pathogenic strains. In contrast, dairy food STEC strains were characterized by a predominance of
stx
1
, with a minority of isolates harboring
eae
,
espP
, and/or
katP
. These associations may help to differentiate less virulent STEC strains from those more likely to cause disease in humans. Only one dairy O5 isolate had a virulence gene panel identical to that of an HUS-associated strain. However, the ribotype and PFGE profiles were not identical. In conclusion, most STEC strains isolated from dairy products in France showed characteristics different from those of strains isolated from patients.
Human
Salmonella
Clinical Isolates Distinct from Those of Animal Origin
Authors: Heithoff Douglas M. , Shimp William R. , Lau Patrick W. , Badie Golnaz , Enioutina Elena Y. , Daynes Raymond A. , Byrne Barbara A. , House John K. , Mahan Michael J.
Published: February 2008

The global trend toward intensive livestock production has led to significant public health risks and industry-associated losses due to an increased incidence of disease and contamination of livestock-derived food products. A potential factor contributing to these health concerns is the prospect that selective pressure within a particular host may give rise to bacterial strain variants that exhibit enhanced fitness in the present host relative to that in the parental host from which the strain was derived. Here, we assessed 184
Salmonella enterica
human and animal clinical isolates for their virulence capacities in mice and for the presence of the
Salmonella
virulence plasmid encoding the SpvB actin cytotoxin required for systemic survival and Pef fimbriae, implicated in adherence to the murine intestinal epithelium. All (21 of 21) serovar Typhimurium clinical isolates derived from animals were virulent in mice, whereas many (16 of 41) serovar Typhimurium isolates derived from human salmonellosis patients lacked this capacity. Additionally, many (10 of 29) serovar Typhimurium isolates derived from gastroenteritis patients did not possess the
Salmonella
virulence plasmid, in contrast to all animal and human bacteremia isolates tested. Lastly, among serovar Typhimurium isolates that harbored the
Salmonella
virulence plasmid, 6 of 31 derived from human salmonellosis patients were avirulent in mice, which is in contrast to the virulent phenotype exhibited by all the animal isolates examined. These studies suggest that
Salmonella
isolates derived from human salmonellosis patients are distinct from those of animal origin. The characterization of these bacterial strain variants may provide insight into their relative pathogenicities as well as into the development of treatment and prophylactic strategies for salmonellosis.
Bot1p Is Required for Mitochondrial Translation, Respiratory Function, and Normal Cell Morphology in the Fission Yeast
Schizosaccharomyces pombe
Authors: Wiley David J. , Catanuto Paola , Fontanesi Flavia , Rios Carmen , Sanchez Natalie , Barrientos Antoni , Verde Fulvia
Published: February 2008

Maintenance of cell morphology is essential for normal cell function. For eukaryotic cells, a growing body of recent evidence highlights a close interdependence between mitochondrial function, the cytoskeleton, and cell cycle control mechanisms; however, the molecular details of this interconnection are still not completely understood. We have identified a novel protein, Bot1p, in the fission yeast
Schizosaccharomyces pomb
e. The
bot1
gene is essential for cell viability.
bot1Δ
mutant cells expressing lower levels of Bot1p display altered cell size and cell morphology and a disrupted actin cytoskeleton. Bot1p localizes to the mitochondria in live cells and cofractionates with purified mitochondrial ribosomes. Reduced levels of Bot1p lead to mitochondrial fragmentation, decreased mitochondrial protein translation, and a corresponding decrease in cell respiration. Overexpression of Bot1p results in cell cycle delay, with increased cell size and cell length and enhanced cell respiration rate. Our results show that Bot1p has a novel function in the control of cell respiration by acting on the mitochondrial protein synthesis machinery. Our observations also indicate that in fission yeast, alterations of mitochondrial function are linked to changes in cell cycle and cell morphology control mechanisms.
Investigation of Regulation of FtsZ Assembly by SulA and Development of a Model for FtsZ Polymerization
Authors: Dajkovic Alex , Mukherjee Amit , Lutkenhaus Joe
Published: February 2008

InEscherichia coliFtsZ organizes into a cytoskeletal ring structure, the Z ring, which effects cell division. FtsZ is a GTPase, but the free energy of GTP hydrolysis does not appear to be used for generation of the constriction force, leaving open the question of the function of the GTPase activity of FtsZ. Here we study the mechanism by which SulA, an inhibitor of FtsZ induced during the SOS response, inhibits FtsZ function. We studied the effects of SulA on the in vitro activities of FtsZ, on Z rings in vivo, and on a kinetic model for FtsZ polymerization in silico. We found that the binding of SulA to FtsZ is necessary but not sufficient for inhibition of polymerization, since the assembly of FtsZ polymers in the absence of the GTPase activity was not inhibited by SulA. We developed a new model for FtsZ polymerization that accounts for the cooperativity of FtsZ and could account for cooperativity observed in other linear polymers. When SulA was included in the kinetic scheme, simulations revealed that SulA with strong affinity for FtsZ delayed, but did not prevent, the assembly of polymers when they were not hydrolyzing GTP. Furthermore, the simulations indicated that SulA controls the assembly of FtsZ by binding to a polymerization-competent form of the FtsZ molecule and preventing it from participating in assembly. In vivo stoichiometry of the disruption of Z rings by SulA suggests that FtsZ may undergo two cooperative transitions in forming the Z ring.
Swarming ofPseudomonas aeruginosaIs a Complex Adaptation Leading to Increased Production of Virulence Factors and Antibiotic Resistance
Authors: Overhage Joerg , Bains Manjeet , Brazas Michelle D. , Hancock Robert E. W.
Published: February 2008

In addition to exhibiting swimming and twitching motility,Pseudomonas aeruginosais able to swarm on semisolid (viscous) surfaces. Recent studies have indicated that swarming is a more complex type of motility influenced by a large number of different genes. To investigate the adaptation process involved in swarming motility, gene expression profiles were analyzed by performing microarrays on bacteria from the leading edge of a swarm zone compared to bacteria growing in identical medium under swimming conditions. Major shifts in gene expression patterns were observed under swarming conditions, including, among others, the overexpression of a large number of virulence-related genes such as those encoding the type III secretion system and its effectors, those encoding extracellular proteases, and those associated with iron transport. In addition, swarming cells exhibited adaptive antibiotic resistance against polymyxin B, gentamicin, and ciprofloxacin compared to what was seen for their planktonic (swimming) counterparts. By analyzing a large subset of up-regulated genes, we were able to show that two virulence genes,lasBandpvdQ, were required for swarming motility. These results clearly favored the conclusion that swarming ofP. aeruginosais a complex adaptation process in response to a viscous environment resulting in a substantial change in virulence gene expression and antibiotic resistance.
Mycobacterium aviumsubsp.paratuberculosisandM. aviumsubsp.aviumAre Independently Evolved Pathogenic Clones of a Much Broader Group ofM. aviumOrganisms
Authors: Turenne Christine Y. , Collins Desmond M. , Alexander David C. , Behr Marcel A.
Published: February 2008

Mycobacterium aviumcomprises organisms that share the same species designation despite considerable genomic and phenotypic variability. To determine the degree and nature of variability between subspecies and strains ofM. avium, we used multilocus sequencing analysis, studying 56 genetically diverse strains ofM. aviumthat included all described subspecies. In total, 8,064 bp of sequence from 10 gene loci were studied, with 205 (2.5%) representing variable positions. The majority (149/205) of these variations were found amongM. aviumsubsp.hominissuisorganisms. Recombination was also evident in this subspecies. In contrast, there was comparatively little variability and no evidence of recombination within the pathogenic subspecies,M. aviumsubsp.paratuberculosis,M. aviumsubsp.avium, andM. aviumsubsp.silvaticum.Phylogenetic analysis showed thatM. aviumsubsp.aviumandM. aviumsubsp.silvaticumstrains clustered together on one branch, while a distinct branch definedM. aviumsubsp.paratuberculosisorganisms. Despite the independent origin of these pathogenic subspecies, an analysis of their rates of nonsynonymous (dN) to synonymous (dS) substitutions showed increased dN/dS ratios for both: 0.67 forM. aviumsubsp.paratuberculosisand 0.50 forM. aviumsubsp.avium/M. aviumsubsp.silvaticum, while the value was 0.08 forM. aviumsubsp.hominissuisorganisms. In conclusion,M. aviumsubsp.hominissuisrepresents a diverse group of organisms from which two pathogenic clones (M. aviumsubsp.paratuberculosisandM. aviumsubsp.avium/M. aviumsubsp.silvaticum) have evolved independently.