bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation of Adenoviruses, Enteroviruses, and Murine Norovirus in Water by Free Chlorine and Monochloramine
Authors: Cromeans Theresa L. , Kahler Amy M. , Hill Vincent R. 
Published: December 2009

ABSTRACT

Inactivation of infectious viruses during drinking water treatment is usually achieved with free chlorine. Many drinking water utilities in the United States now use monochloramine as a secondary disinfectant to minimize disinfectant by-product formation and biofilm growth. The inactivation of human adenoviruses 2, 40, and 41 (HAdV2, HAdV40, and HAdV41), coxsackieviruses B3 and B5 (CVB3 and CVB5), echoviruses 1 and 11 (E1 and E11), and murine norovirus (MNV) are compared in this study. Experiments were performed with 0.2 mg of free chlorine or 1 mg of monochloramine/liter at pH 7 and 8 in buffered reagent-grade water at 5°C. CT values (disinfectant concentration × time) for 2- to 4-log
10
(99 to 99.99%) reductions in virus titers were calculated by using the efficiency factor Hom model. The enteroviruses required the longest times for chlorine inactivation and MNV the least time. CVB5 required the longest exposure time, with CT values of 7.4 and 10 mg·min/liter (pH 7 and 8) for 4-log
10
inactivation. Monochloramine disinfection was most effective for E1 (CT values ranged from 8 to 18 mg·min/liter for 2- and 3-log
10
reductions, respectively). E11 and HAdV2 were the least susceptible to monochloramine disinfection (CT values of 1,300 and 1,600 mg-min/liter for 3-log
10
reductions, respectively). Monochloramine inactivation was most successful for the adenoviruses, CVB5, and E1 at pH 7. A greater variation in inactivation rates between viruses was observed during monochloramine disinfection than during chlorine disinfection. These data will be useful in drinking water risk assessment studies and disinfection system planning.
Mechanisms Involved in Governing Adherence ofVibrio choleraeto Granular Starch
Authors: Niderman-Meyer Orly , Zeidman Tal , Shimoni Eyal , Kashi Yechezkel 
Published: December 2009

ABSTRACTVibrio choleraehas been shown to adhere to cornstarch granules. The present work explored the mechanisms involved in this adhesion and the possibility of its occurrencein vivo. The findings suggest that both specific and nonspecific interactions are involved in the adhesion. Nonspecific hydrophobic interactions may play a role, since bothV. choleraeand cornstarch granules exhibited hydrophobic properties when they were tested using a xylene-water system. In addition, the presence of bile acids reduced the adhesion. The adhesion also involves some specific carbohydrate-binding moieties on the cell surface, as reflected by reduced adhesion following pretreatment of the bacteria with proteinase K and sodiumm-periodate. Further investigations supported these observations and showed that media containing low-molecular-weight carbohydrates had a significant inhibitory effect. Binding cell lysate to starch granules and removing the adhered proteins using either glucose or bile acids led to identification (by liquid chromatography-tandem mass spectrometry analysis) of several candidateV. choleraeouter membrane-associated starch-binding proteins. Different sets of proteins were isolated by removal in a glucose solution or bile acids. When the upper gastrointestinal tract conditions were simulatedin vitro, both bile salts and the amylolytic activity of the pancreatic juices were found to have an inhibitory effect on the adherence ofV. choleraeto starch. However, during acute diarrhea, this inhibitory effect may be significantly reduced due to dilution, suggesting that adhesion does occurin vivo. Such adhesion may contribute to the beneficial effects observed following administration of granular starch-based oral rehydration solutions to cholera patients.
Yeast Surface Display of Trifunctional Minicellulosomes for Simultaneous Saccharification and Fermentation of Cellulose to Ethanol
Authors: Wen Fei , Sun Jie , Zhao Huimin 
Published: December 2009

ABSTRACT

By combining cellulase production, cellulose hydrolysis, and sugar fermentation into a single step, consolidated bioprocessing (CBP) represents a promising technology for biofuel production. Here we report engineering of
Saccharomyces cerevisiae
strains displaying a series of uni-, bi-, and trifunctional minicellulosomes. These minicellulosomes consist of (i) a miniscaffoldin containing a cellulose-binding domain and three cohesin modules, which was tethered to the cell surface through the yeast a-agglutinin adhesion receptor, and (ii) up to three types of cellulases, an endoglucanase, a cellobiohydrolase, and a β-glucosidase, each bearing a C-terminal dockerin. Cell surface assembly of the minicellulosomes was dependent on expression of the miniscaffoldin, indicating that formation of the complex was dictated by the high-affinity interactions between cohesins and dockerins. Compared to the unifunctional and bifunctional minicellulosomes, the quaternary trifunctional complexes showed enhanced enzyme-enzyme synergy and enzyme proximity synergy. More importantly, surface display of the trifunctional minicellulosomes gave yeast cells the ability to simultaneously break down and ferment phosphoric acid-swollen cellulose to ethanol with a titer of ∼1.8 g/liter. To our knowledge, this is the first report of a recombinant yeast strain capable of producing cell-associated trifunctional minicellulosomes. The strain reported here represents a useful engineering platform for developing CBP-enabling microorganisms and elucidating principles of cellulosome construction and mode of action.
Metabolic Differentiation in Biofilms as Indicated by Carbon Dioxide Production Rates
Authors: Bester Elanna , Kroukamp Otini , Wolfaardt Gideon M. , Boonzaaier Leandro , Liss Steven N. 
Published: December 2009

ABSTRACT

The measurement of carbon dioxide production rates as an indication of metabolic activity was applied to study biofilm development and response of
Pseudomonas
sp. biofilms to an environmental disturbance in the form of a moving air-liquid interface (i.e., shear). A differential response in biofilm cohesiveness was observed after bubble perturbation, and the biofilm layers were operationally defined as either shear-susceptible or non-shear-susceptible. Confocal laser scanning microscopy and image analysis showed a significant reduction in biofilm thickness and biomass after the removal of the shear-susceptible biofilm layer, as well as notable changes in the roughness coefficient and surface-to-biovolume ratio. These changes were accompanied by a 72% reduction of whole-biofilm CO
2
production; however, the non-shear-susceptible region of the biofilm responded rapidly after the removal of the overlying cells and extracellular polymeric substances (EPS) along with the associated changes in nutrient and O
2
flux, with CO
2
production rates returning to preperturbation levels within 24 h. The adaptable nature and the ability of bacteria to respond to environmental conditions were further demonstrated by the outer shear-susceptible region of the biofilm; the average CO
2
production rate of cells from this region increased within 0.25 h from 9.45 ± 5.40 fmol of CO
2
·cell
−1
·h
−1
to 22.6 ± 7.58 fmol of CO
2
·cell
−1
·h
−1
when cells were removed from the biofilm and maintained in suspension without an additional nutrient supply. These results also demonstrate the need for sufficient monitoring of biofilm recovery at the solid substratum if mechanical methods are used for biofouling control.
Seasonal Retention and Release of
Cryptosporidium parvum
Oocysts by Environmental Biofilms in the Laboratory
Authors: Wolyniak E. A. , Hargreaves B. R. , Jellison K. L. 
Published: December 2009

ABSTRACT

Cryptosporidium
is a genus of waterborne protozoan parasites that causes significant gastrointestinal disease in humans. These parasites can accumulate in environmental biofilms and be subsequently released to contaminate water supplies. Natural microbial assemblages were collected each season from an eastern Pennsylvania stream and used to grow biofilms in laboratory microcosms in which influx, efflux, and biofilm retention were determined from daily oocyst counts. For each seasonal biofilm, oocysts attached to the biofilm quickly during oocyst dosing. Upon termination of oocyst dosing, the percentage of oocysts retained within the biofilm decreased to a new steady state within 5 days. Seasonal differences in biofilm retention of oocysts were observed. The spring biofilm retained the greatest percentage of oocysts, followed (in decreasing order) by the winter, summer, and fall biofilms. There was no statistically significant correlation between the percentage of oocysts attached to the biofilm and (i) any measured stream water quality parameter (including temperature, pH, conductivity, and dissolved organic carbon concentration) or (ii) experimental temperature. Seasonal differences in oocyst retention persisted when biofilms were tested with stream water from a different season. These data suggest that seasonal variation in the microbial community and resulting biofilm architecture may be more important to oocyst transport in this stream site than water quality. The biofilm attachment and detachment dynamics of
C. parvum
oocysts have implications for public health, and the drinking water industry should recognize that the potential exists for pathogen-free water to become contaminated during the distribution process as a result of biofilm dynamics.
Use of a Foam Spatula for Sampling Surfaces after Bioaerosol Deposition
Authors: Lewandowski Rafał , Kozłowska Krystyna , Szpakowska Małgorzata , Stępińska Małgorzata , Trafny Elżbieta A. 
Published: December 2009

ABSTRACT

The present study had three goals: (i) to evaluate the relative quantities of aerosolized
Bacillus atrophaeus
spores deposited on the vertical, horizontal top, and horizontal bottom surfaces in a chamber; (ii) to assess the relative recoveries of the aerosolized spores from glass and stainless steel surfaces with a polyester swab and a macrofoam sponge wipe; and (iii) to estimate the relative recovery efficiencies of aerosolized
B. atrophaeus
spores and
Pantoea agglomerans
using a foam spatula at several different bacterial loads by aerosol distribution on glass surfaces. The majority of spores were collected from the bottom horizontal surface regardless of which swab type and extraction protocol were used. Swabbing with a macrofoam sponge wipe was more efficient in recovering spores from surfaces contaminated with high bioaerosol concentrations than swabbing with a polyester swab.
B. atrophaeus
spores and
P. agglomerans
culturable cells were detected on glass surfaces using foam spatulas when the theoretical surface bacterial loads were 2.88 × 10
4
CFU and 8.09 × 10
6
CFU per 100-cm
2
area, respectively. The median recovery efficiency from the surfaces using foam spatulas was equal to 9.9% for
B. atrophaeus
spores when the recovery was calculated relative to the theoretical surface spore load. Using a foam spatula permits reliable sampling of spores on the bioaerosol-exposed surfaces in a wide measuring range. The culturable
P. agglomerans
cells were recovered with a median efficiency of 0.001%, but staining the swab extracts with fluorescent dyes allowed us to observe that the viable cell numbers were higher by 1.83 log units than culturable organisms. However, additional work is needed to improve the analysis of the foam extracts in order to decrease the limit of detection of
Bacillus
spores and Gram-negative bacteria on contaminated surfaces.
Prolonged Survival ofCampylobacterSpecies in Bovine Manure Compost
Authors: Inglis G. Douglas , McAllister Tim A. , Larney Francis J. , Topp Edward 
Published: December 2009

ABSTRACTThe persistence of naturally occurring campylobacteria in aerobic compost constructed of manure from beef cattle that were administered chlortetracycline and sulfamethazine (AS700) or from cattle not administered antibiotics (control) was examined. Although there were no differences in population sizes of heterotrophic bacteria, the temperature of AS700 compost was more variable and did not become as high as that of control compost. There were significant differences in water content, total carbon (C), total nitrogen (N), and electrical conductivity but not in the C/N ratio or pH between the two compost treatments. Campylobacteria were readily isolated from pen manure, for up to day 15 from control compost, and throughout the active phase of AS700 compost.CampylobacterDNA (includingCampylobacter coli,Campylobacter fetus,Campylobacter hyointestinalis, andCampylobacter jejuni) was detected over the ca. 10-month composting period, and no reductions in quantities ofC. jejuniDNA were observed over the duration of the active phase. The utilization of centrifugation in combination with ethidium monoazide (EMA) significantly reduced (>90%) the amplification ofC. jejuniDNA that did not originate from cells with intact cell membranes. No differences were observed in the frequency ofCampylobacterDNA detection between EMA- and non-EMA-treated samples, suggesting thatCampylobacterDNA amplified from compost was extracted from cells with intact cell membranes (i.e., from viable cells). The findings of this study indicate that campylobacteria excreted in cattle feces persist for long periods in compost and call into question the common belief that these bacteria do not persist in manure.
Optimization of RNA Extraction for PCR Quantification of Aromatic Compound Degradation Genes
Authors: Kong Weidong , Nakatsu Cindy H. 
Published: December 2009

ABSTRACT
Seven different bacterial strains and primer sets and a mixed community were used to evaluate the use of reverse transcriptase quantitative PCR (Q-PCR) and Q-PCR of oxygenase genes to assess various approaches for monitoring the bioremediation of polluted sites. Differences in maximum activity were seen when different RNA extraction kits were compared.
Regulation of Arabinose and Xylose Metabolism inEscherichia coli
Authors: Desai Tasha A. , Rao Christopher V. 
Published: December 2009

ABSTRACTBacteria such asEscherichia coliwill often consume one sugar at a time when fed multiple sugars, in a process known as carbon catabolite repression. The classic example involves glucose and lactose, whereE. coliwill first consume glucose, and only when it has consumed all of the glucose will it begin to consume lactose. In addition to that of lactose, glucose also represses the consumption of many other sugars, including arabinose and xylose. In this work, we characterized a second hierarchy inE. coli, that between arabinose and xylose. We show that, when grown in a mixture of the two pentoses,E. coliwill consume arabinose before it consumes xylose. Consistent with a mechanism involving catabolite repression, the expression of the xylose metabolic genes is repressed in the presence of arabinose. We found that this repression is AraC dependent and involves a mechanism where arabinose-bound AraC binds to the xylose promoters and represses gene expression. Collectively, these results demonstrate that sugar utilization inE. coliinvolves multiple layers of regulation, where cells will consume first glucose, then arabinose, and finally xylose. These results may be pertinent in the metabolic engineering ofE. colistrains capable of producing chemical and biofuels from mixtures of hexose and pentose sugars derived from plant biomass.
Shear-Enhanced Oral Microbial Adhesion
Authors: Ding Albert M. , Palmer Robert J. , Cisar John O. , Kolenbrander Paul E. 
Published: December 2009

ABSTRACT

Shear-enhanced adhesion, although not observed for fimbria-mediated adhesion of oral
Actinomyces
spp., was noted for Hsa-mediated adhesion of
Streptococcus gordonii
to sialic acid-containing receptors, an interaction implicated in the pathogenesis of infective endocarditis.
Association of Hemolytic Activity ofPseudomonas entomophila, a Versatile Soil Bacterium, with Cyclic Lipopeptide Production
Authors: Vallet-Gely Isabelle , Novikov Alexey , Augusto Luis , Liehl Peter , Bolbach Gérard , Péchy-Tarr Maria , Cosson Pierre , Keel Christoph , Caroff Martine , Lemaitre Bruno 
Published: December 2009

ABSTRACTPseudomonas entomophilais an entomopathogenic bacterium that is able to infect and killDrosophila melanogasterupon ingestion. Its genome sequence suggests that it is a versatile soil bacterium closely related toPseudomonas putida. The GacS/GacA two-component system plays a key role inP. entomophilapathogenicity, controlling many putative virulence factors and AprA, a secreted protease important to escape the fly immune response.P. entomophilasecretes a strong diffusible hemolytic activity. Here, we showed that this activity is linked to the production of a new cyclic lipopeptide containing 14 amino acids and a 3-C10OH fatty acid that we called entolysin. Three nonribosomal peptide synthetases (EtlA, EtlB, EtlC) were identified as responsible for entolysin biosynthesis. Two additional components (EtlR, MacAB) are necessary for its production and secretion. TheP. entomophilaGacS/GacA two-component system regulates entolysin production, and we demonstrated that its functioning requires two small RNAs and two RsmA-like proteins. Finally, entolysin is required for swarming motility, as described for other lipopeptides, but it does not participate in the virulence ofP. entomophilaforDrosophila. While investigating the physiological role of entolysin, we also uncovered new phenotypes associated withP. entomophila, including strong biocontrol abilities.
Improved Electrotransformation and Decreased Antibiotic Resistance of the Cystic Fibrosis Pathogen
Burkholderia cenocepacia
Strain J2315
Authors: Dubarry Nelly , Du Wenli , Lane David , Pasta Franck 
Published: December 2009

ABSTRACT

The bacterium
Burkholderia cenocepacia
is pathogenic for sufferers from cystic fibrosis (CF) and certain immunocompromised conditions. The
B. cenocepacia
strain most frequently isolated from CF patients, and which serves as the reference for CF epidemiology, is J2315. The J2315 genome is split into three chromosomes and one plasmid. The strain was sequenced several years ago, and its annotation has been released recently. This information should allow genetic experimentation with J2315, but two major impediments appear: the poor potential of J2315 to act as a recipient in transformation and conjugation and the high level of resistance it mounts to nearly all antibiotics. Here, we describe modifications to the standard electroporation procedure that allow routine transformation of J2315 by DNA. In addition, we show that deletion of an efflux pump gene and addition of spermine to the medium enhance the sensitivity of J2315 to certain commonly used antibiotics and so allow a wider range of antibiotic resistance genes to be used for selection.
Adaptation of the Highly Productive T7 Expression System to
Streptomyces lividans
Authors: Lussier François-Xavier , Denis François , Shareck François 
Published: December 2009

ABSTRACT

Streptomyces lividans
is a Gram-positive bacterium known for its remarkable secretion efficiency and low extracellular protease activity. In the present work, we adapted the highly productive T7 expression system to
S. lividans
. A codon-optimized T7 RNA polymerase gene was chromosomally integrated, and a bifunctional T7 expression vector was constructed.
Type II Diacylglycerol Acyltransferase fromClaviceps purpureawith Ricinoleic Acid, a Hydroxyl Fatty Acid of Industrial Importance, as Preferred Substrate
Authors: Mavraganis Ioannis , Meesapyodsuk Dauenpen , Vrinten Patricia , Smith Mark , Qiu Xiao 
Published: December 2009

ABSTRACTClaviceps purpurea, the fungal pathogen that causes the cereal disease ergot, produces glycerides that contain high levels of ricinoleic acid [(R)-12-hydroxyoctadec-cis-9-enoic acid] in its sclerotia. Recently, a fatty acid hydroxylase (C. purpureaFAH [CpFAH]) involved in the biosynthesis of ricinoleic acid was identified from this fungus (D. Meesapyodsuk and X. Qiu, Plant Physiol.147:1325-1333, 2008). Here, we describe the cloning and biochemical characterization of aC. purpureatype II diacylglycerol acyltransferase (CpDGAT2) involved in the assembly of ricinoleic acid into triglycerides. TheCpDGAT2gene was cloned by degenerate RT-PCR (reverse transcription-PCR). The expression of this gene restored thein vivosynthesis of triacylglycerol (TAG) in the quadruple mutant strainSaccharomyces cerevisiaeH1246, in which all four TAG biosynthesis genes (DGA1,LRO1,ARE1, andARE2) are disrupted.In vitroenzymatic assays using microsomal preparations from the transformed yeast strain indicated that CpDGAT2 prefers ricinoleic acid as an acyl donor over linoleic acid, oleic acid, or linolenic acid, and it prefers 1,2-dioleoyl-sn-glycerol over 1,2-dipalmitoyl-sn-glycerol as an acyl acceptor. The coexpression of CpFAH with CpDGAT2 in yeast resulted in an increased accumulation of ricinoleic acid compared to the coexpression of CpFAH with the native yeast DGAT2 (S. cerevisiaeDGA1 [ScDGA1]) or the expression of CpFAH alone. Northern blot analysis indicated thatCpFAHis expressed solely in sclerotium cells, with no transcripts of this gene being detected in mycelium or conidial cells. CpDGAT2 was more widely expressed among the cell types examined, although expression was low in conidiospores. The high expression of CpDGAT2 and CpFAH in sclerotium cells, where high levels of ricinoleate glycerides accumulate, provided further evidence supporting the roles of CpDGAT2 and CpFAH as key enzymes for the synthesis and assembly of ricinoleic acid inC. purpurea.
Musca domestica
Salivary Gland Hypertrophy Virus, a Globally Distributed Insect Virus That Infects and Sterilizes Female Houseflies
Authors: Prompiboon Pannipa , Lietze Verena-Ulrike , Denton John S. S. , Geden Christopher J. , Steenberg Tove , Boucias Drion G. 
Published: December 2009

ABSTRACT

The housefly,
Musca domestica
, is a cosmopolitan pest of livestock and poultry and is of economic, veterinary, and public health importance. Populations of
M. domestica
are naturally infected with
M. domestica
salivary gland hypertrophy virus (MdSGHV), a nonoccluded double-stranded DNA virus that inhibits egg production in infected females and is characterized by salivary gland hypertrophy (SGH) symptoms. MdSGHV has been detected in housefly samples from North America, Europe, Asia, the Caribbean, and the southwestern Pacific. In this study, houseflies were collected from various locations and dissected to observe SGH symptoms, and infected gland pairs were collected for MdSGHV isolation and amplification in laboratory-reared houseflies. Differences among the MdSGHV isolates were examined by using molecular and bioassay approaches. Approximately 600-bp nucleotide sequences from each of five open reading frames having homology to genes encoding DNA polymerase and partial homology to the genes encoding four
per os
infectivity factor proteins (p74, pif-1, pif-2, and pif-3) were selected for phylogenetic analyses. Nucleotide sequences from 16 different geographic isolates were highly homologous, and the polymorphism detected was correlated with geographic source. The virulence of the geographic MdSGHV isolates was evaluated by
per os
treatment of newly emerged and 24-h-old houseflies with homogenates of infected salivary glands. In all cases, 24-h-old flies displayed a resistance to oral infection that was significantly greater than that displayed by newly eclosed adults. Regardless of the MdSGHV isolate tested, all susceptible insects displayed similar degrees of SGH and complete suppression of oogenesis.