bluuebunny/crossref_metadata_2025_split huggingface dataset:
SOD1, a New
Kluyveromyces lactis
Helper Gene for Heterologous Protein Secretion
Authors: Raimondi S. , Zanni E. , Talora C. , Rossi M. , Palleschi C. , Uccelletti D. 
Published: October 2008

ABSTRACT

Bottlenecks in protein expression and secretion often limit the development of industrial processes. By manipulating chaperone and foldase levels, improvements in yeast secretion were found for a number of proteins. Recently, sustained endoplasmic reticulum stress, occurring due to recombinant protein production, was reported to cause oxidative stress in yeast.
Saccharomyces cerevisiae
cells are able to trigger an adaptive response to oxidative-stress conditions, resulting in the upregulation of both primary and secondary antioxidant defenses.
SOD1
encodes for a superoxide dismutase that catalyzes the dismutation of superoxide anions (O
2
−
) into oxygen and hydrogen peroxide. It is a Cu
2+
/Zn
2+
metalloenzyme and represents an important antioxidant defense in nearly all aerobic and aerotolerant organisms. We found that overexpression of the
Kluyveromyces lactis SOD1
(Kl
SOD1
) gene was able to increase the production of two different heterologous proteins, human serum albumin (HSA) and glucoamylase from
Arxula adeninivorans
. In addition, Kl
SOD1
overexpression led to a significant decrease in the amount of reactive oxygen species (ROS) that originated during protein production. The yield of HSA also increased when
K. lactis
cells were grown in the presence of the antioxidant agent ascorbic acid and decreased when cells were challenged with menadione, a ROS generator compound. Moreover, we observed that, in high-osmolarity medium, cells overexpressing Kl
SOD1
showed higher growth rates than control cells. Our results thus further support the notion that the production of some heterologous proteins may be improved by manipulating genes involved in general stress responses.
Cloning and Heterologous Expression of Insecticidal-Protein-Encoding Genes from
Photorhabdus luminescens
TT01 in
Enterobacter cloacae
for Termite Control
Authors: Zhao Ruihua , Han Richou , Qiu Xuehong , Yan Xun , Cao Li , Liu Xiuling 
Published: October 2008

ABSTRACT

Enterobacter cloacae
, one of the indigenous gut bacteria of the Formosan subterranean termite (
Coptotermes formosanus
), was genetically modified with a transposon Tn
5
vector containing genes (
tcdA1
and
tcdB1
) encoding orally insecticidal proteins from the entomopathogenic bacterium
Photorhabdus luminescens
subsp.
laumondii
TT01, a symbiont of the entomopathogenic nematode
Heterorhabditis bacteriophora
, for termite control. In the laboratory, termites were fed filter paper inoculated with the recombinant bacteria. The chromosomal expression of the introduced genes showed that there were insecticidal activities against termite workers and soldiers challenged with the transformed bacteria. After termites were fed recombinant bacteria, the termite mortality was 3.3% at day 5, and it increased from 8.7% at day 9 to 93.3% at day 29. All the dead termites contained the recombinant bacteria in their guts. Transfer of the recombinant bacteria occurred between donor workers (initially fed recombinant bacteria) and recipient workers (not fed). More than 20% of the recipient termites ingested recombinant bacteria within 2 h, and 73.3% of them had ingested recombinant bacteria after 12 h. The method described here provides a useful alternative for sustainable control of the Formosan subterranean termite (
C. formosanus
) and other social insects, such as the imported red fire ant (
Solenopsis invicta
).
Secretion of Insulinotropic Proteins by Commensal Bacteria: Rewiring the Gut To Treat Diabetes
Authors: Duan Faping , Curtis Katherine L. , March John C. 
Published: October 2008

ABSTRACT

Here, we show that commensal bacteria can stimulate intestinal epithelial cells to secrete insulin in response to glucose. Commensal strains were engineered to secrete the insulinotropic proteins GLP-1 and PDX-1. Epithelia stimulated by engineered strains and glucose secreted up to 1 ng ml
−1
of insulin with no significant background secretion.
Host Adaptation of aWolbachiaStrain after Long-Term Serial Passage in Mosquito Cell Lines
Authors: McMeniman Conor J. , Lane Amanda M. , Fong Amy W. C. , Voronin Denis A. , Iturbe-Ormaetxe Iñaki , Yamada Ryuichi , McGraw Elizabeth A. , O'Neill Scott L. 
Published: October 2008

ABSTRACTThe horizontal transfer of the bacteriumWolbachia pipientisbetween invertebrate hosts hinges on the ability ofWolbachiato adapt to new intracellular environments. The experimental transfer ofWolbachiabetween distantly related host species often results in the loss of infection, presumably due to an inability ofWolbachiato adapt quickly to the new host. To examine the process of adaptation to a novel host, we transferred a life-shorteningWolbachiastrain,wMelPop, from the fruit flyDrosophila melanogasterinto a cell line derived from the mosquitoAedes albopictus. After long-term serial passage in this cell line, we transferred the mosquito-adaptedwMelPop into cell lines derived from two other mosquito species,Aedes aegyptiandAnopheles gambiae. After a prolonged period of serial passage in mosquito cell lines,wMelPop was reintroduced into its native host,D. melanogaster, by embryonic microinjection. The cell line-adaptedwMelPop strains were characterized by a loss of infectivity when reintroduced into the original host, grew to decreased densities, and had reduced abilities to cause life-shortening infection and cytoplasmic incompatibility compared to the original strain. We interpret these shifts in phenotype as evidence for genetic adaptation to the mosquito intracellular environment. The use of cell lines to preadaptWolbachiato novel hosts is suggested as a possible strategy to improve the success of transinfection in novel target insect species.
Development and Implementation of a Multiplex Single-Nucleotide Polymorphism Genotyping Assay for Detection of Virulence-Attenuating Mutations in theListeria monocytogenesVirulence-Associated GeneinlA
Authors: Van Stelten A. , Nightingale K. K. 
Published: October 2008

ABSTRACTThe virulence factor internalin A (InlA) facilitates the uptake ofListeria monocytogenesby epithelial cells that express the human isoform of E-cadherin. Previous studies identified naturally occurring premature stop codon (PMSC) mutations ininlAand demonstrated that these mutations are responsible for virulence attenuation. We assembled >1,700L. monocytogenesisolates from diverse sources representing 90 EcoRI ribotypes. A subset of this isolate collection was selected based on ribotype frequency and characterized by a Caco-2 cell invasion assay. The sequencing ofinlAgenes from isolates with attenuated invasion capacities revealed three novelinlAPMSCs which had not been identified previously among U.S. isolates. Since ribotypes include isolates with and withoutinlAPMSCs, we developed a multiplex single-nucleotide polymorphism (SNP) genotyping assay to detect isolates with virulence-attenuating PMSC mutations ininlA. The SNP genotyping assay detects allinlAPMSC mutations that have been reported worldwide and verified in this study to date by the extension of unlabeled primers with fluorescently labeled dideoxynucleoside triphosphates. We implemented the SNP genotyping assay to characterize human clinical and food isolates representing common ribotypes associated with novelinlAPMSC mutations. PMSCs ininlAwere significantly (ribotypes DUP-1039C and DUP-1045B;P< 0.001) or marginally (ribotype DUP-1062D;P= 0.11) more common among food isolates than human clinical isolates. SNP genotyping revealed a fourth novel PMSC mutation among U.S.L. monocytogenesisolates, which was observed previously among isolates from France and Portugal. This SNP genotyping assay may be implemented by regulatory agencies and the food industry to differentiateL. monocytogenesisolates carrying virulence-attenuating PMSC mutations ininlAfrom strains representing the most significant health risk.
A Putative ABC Transporter Is Involved in Negative Regulation of Biofilm Formation by
Listeria monocytogenes
Authors: Zhu Xinna , Long Fei , Chen Yonghui , Knøchel Susanne , She Qunxin , Shi Xianming 
Published: October 2008

ABSTRACT

Listeria monocytogenes
may persist for long periods in food processing environments. In some instances, this may be due to aggregation or biofilm formation. To investigate the mechanism controlling biofilm formation in the food-borne pathogen
L. monocytogenes
, we characterized LM-49, a mutant with enhanced ability of biofilm formation generated via transposon Tn
917
mutagenesis of
L. monocytogenes
4b G. In this mutant, a Tn
917
insertion has disrupted the coding region of the gene encoding a putative ATP-binding cassette (ABC) transporter permease identical to Lmof2365_1771 (a putative ABC transporter permease) presented in the sequenced strain
L. monocytogenes
strain 4b F2365. This disrupted gene, denoted lm.G_1771, encoded a protein with 10 transmembrane helixes. The revertant, LM-49RE, was obtained by replacing lm.G_1771::
Tn917
with lm.G_1771 via homologous recombination. We found that LM-49RE formed the same amount of biofilm biomass as the wild-type strain. Furthermore, transcription of the downstream lm.G_1770 gene was not influenced by the upstream Tn
917
insertion, and the presence of Tn
917
has no effect on biofilm formation. These results suggest that lm.G_1771 was solely responsible for the negative regulation of biofilm formation by
L. monocytogenes
4b G. The immediate gene upstream of lm.G_1771 encoded an ATP-binding protein. Bioinformatics analysis suggested that these two genes were organized into an operon and that their proteins formed an export ABC transporter. Here, we report the characterization of the mutant and identification of a novel ABC transporter that functions in negative regulation of biofilm formation in
L. monocytogenes
.
Persistent Association of
Mycobacterium ulcerans
with West African Predaceous Insects of the Family Belostomatidae
Authors: Mosi Lydia , Williamson Heather , Wallace John R. , Merritt Richard W. , Small P. L. C. 
Published: October 2008

ABSTRACT

A number of studies have suggested that
Mycobacterium ulcerans
, the etiological agent of Buruli ulcer, may be transmitted to humans by insect bites.
M. ulcerans
has been isolated from a predaceous aquatic insect, and PCR detection of
M. ulcerans
DNA in aquatic environments suggests that the organism is widely distributed within many invertebrate taxa and functional feeding groups. Thus,
M. ulcerans
may be concentrated through different trophic links. However, the specific environmental niche of
M. ulcerans
and route of transmission to humans remain a mystery. In this study, a biologically relevant infection model in which
M. ulcerans
-infected mosquito larvae were fed to a species of predaceous hemiptera (African Belostomatidae) was used to demonstrate the persistent colonization of
M. ulcerans
and subsequent transmission of bacteria to naïve prey. The association of
M. ulcerans
with specific anatomical compartments showed that
M. ulcerans
accumulates preferentially on the exoskeleton. In contrast, few organisms were found in dissected guts or salivary glands. No difference was found between the ability of wild-type
M. ulcerans
and an
M. ulcerans
isogenic mycolactone-negative mutant to colonize belostomatids. These data show that African belostomatids can successfully be colonized by
M. ulcerans
and support the trophic transfer of
M. ulcerans
within the environment.
Expression Profiles and Physiological Roles of Two Types of Molecular Chaperonins from the Hyperthermophilic Archaeon
Thermococcus kodakarensis
Authors: Fujiwara Shinsuke , Aki Ryohei , Yoshida Masaya , Higashibata Hiroki , Imanaka Tadayuki , Fukuda Wakao 
Published: October 2008

ABSTRACT

Thermococcus kodakarensis
possesses two chaperonins, CpkA and CpkB, and their expression is induced by the downshift and upshift, respectively, of the cell cultivation temperature. The expression levels of the chaperonins were examined by using specific antibodies at various cell growth temperatures in the logarithmic and stationary phases. At 60°C, CpkA was highly expressed in both the logarithmic and stationary phases; however, CpkB was not expressed in either phase. At 85°C, CpkA and CpkB were expressed in both phases; however, the CpkA level was decreased in the stationary phase. At 93°C, CpkA was expressed only in the logarithmic phase and not in the stationary phase. In contrast, CpkB was highly expressed in both phases. The results of reverse transcription-PCR experiments showed the same growth phase- and temperature-dependent profiles as observed in immunoblot analyses, indicating that the expression of
cpkA
and
cpkB
is regulated at the mRNA level. The
cpkA
or
cpkB
gene disruptant was then constructed, and its growth profile was monitored. The
cpkA
disruptant showed poor cell growth at 60°C but no significant defects at 85°C and 93°C. On the other hand,
cpkB
disruption led to growth defects at 93°C but no significant defects at 60°C and 85°C. These data indicate that CpkA and CpkB are necessary for cell growth at lower and higher temperatures, respectively. The logarithmic-phase-dependent expression of CpkA at 93°C suggested that CpkA participates in initial cell growth in addition to lower-temperature adaptation. Promoter mapping and quantitative analyses using the Phr (
Pyrococcus
heat-shock regulator) gene disruptant revealed that temperature-dependent expression was achieved in a Phr-independent manner.
Metalloprotease Vsm Is the Major Determinant of Toxicity for Extracellular Products ofVibrio splendidus
Authors: Binesse Johan , Delsert Claude , Saulnier Denis , Champomier-Vergès Marie-Christine , Zagorec Monique , Munier-Lehmann Hélène , Mazel Didier , Le Roux Frédérique 
Published: October 2008

ABSTRACTGenomic data combined with reverse genetic approaches have contributed to the characterization of major virulence factors ofVibriospecies; however, these studies have targeted primarily human pathogens. Here, we investigate virulence factors in the oyster pathogenVibrio splendidusLGP32 and show that toxicity is correlated to the presence of a metalloprotease and its correspondingvsmgene. Comparative genomics showed that an avirulent strain closely related to LGP32 lacked the metalloprotease. The toxicity of LGP32 metalloprotease was confirmed by exposing mollusk and mouse fibroblastic cell lines to extracellular products (ECPs) of the wild type (wt) and avsmdeletion mutant (Δvsmmutant). The ECPs of the wt induced a strong cytopathic effect whose severity was cell type dependent, while those of the Δvsmmutant were much less toxic, and exposure to purified protein demonstrated the direct toxicity of the Vsm metalloprotease. Finally, to investigate Vsm molecular targets, a proteomic analysis of the ECPs of both LGP32 and the Δvsmmutant was performed, revealing a number of differentially expressed and/or processed proteins. One of these, the VSA1062 metalloprotease, was found to have significant identity to the immune inhibitor A precursor, a virulence factor ofBacillus thuringiensis. Deletion mutants corresponding to several of the major proteins were constructed by allelic exchange, and the ECPs of these mutants proved to be toxic to both cell cultures and animals. Taken together, these data demonstrate that Vsm is the major toxicity factor in the ECPs ofV. splendidus.
Inactivation of Efflux Pumps Abolishes Bacterial Biofilm Formation
Authors: Kvist Malin , Hancock Viktoria , Klemm Per 
Published: October 2008

ABSTRACT
Bacterial biofilms cause numerous problems in health care and industry; notably, biofilms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial biofilms, thus making efflux pumps attractive targets for antibiofilm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofilm formation, and in combination they could abolish biofilm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofilms. The results of this feasibility study might pave the way for new treatments for biofilm-related infections and may be exploited for prevention of biofilms in general.
Identification of a Novel Genomic Island Specific to Hospital-Acquired Clonal Complex 17
Enterococcus faecium
Isolates
Authors: Heikens Esther , van Schaik Willem , Leavis Helen L. , Bonten Marc J. M. , Willems Rob J. L. 
Published: October 2008

ABSTRACT

Hospital-acquired clonal complex 17 (CC17)
Enterococcus faecium
strains are genetically distinct from indigenous strains and are enriched with resistance genes and virulence genes. We identified a genomic island in CC17
E. faecium
tentatively encoding a metabolic pathway involved in carbohydrate transport and metabolism, which may provide a competitive advantage over the indigenous
E. faecium
microbiota.
Fast Sterility Assessment by Germinable-Endospore Biodosimetry
Authors: Yung Pun To , Ponce Adrian 
Published: October 2008

ABSTRACT

The increased demand for sterile products has created the need for rapid technologies capable of validating the hygiene of industrial production processes.
Bacillus
endospores are in standard use as biological indicators for evaluating the effectiveness of sterilization processes. Currently, culture-based methods, requiring more than 2 days before results become available, are employed to verify endospore inactivation. We describe a rapid, microscopy-based endospore viability assay (μEVA) capable of enumerating germinable endospores in less than 15 min. μEVA employs time-gated luminescence microscopy to enumerate single germinable endospores via terbium-dipicolinate (Tb-DPA) luminescence, which is triggered under UV excitation as 10
8
DPA molecules are released during germination on agarose containing Tb
3+
and a germinant (e.g.,
l
-alanine). Inactivation of endospore populations to sterility was monitored with μEVA as a function of thermal and UV dosage. A comparison of culturing results yielded nearly identical decimal reduction values, thus validating μEVA as a rapid biodosimetry method for monitoring sterilization processes. The simple Tb-DPA chemical test for germinability is envisioned to enable fully automated instrumentation for in-line monitoring of hygiene in industrial production processes.
Inferences about the Global Population Structures of
Cryptosporidium parvum
and
Cryptosporidium hominis
Authors: Tanrıverdi Sultan , Grinberg Alex , Chalmers Rachel M. , Hunter Paul R. , Petrovic Zorana , Akiyoshi Donna E. , London Eric , Zhang Linghui , Tzipori Saul , Tumwine James K. , Widmer Giovanni 
Published: October 2008

ABSTRACT

Cryptosporidium parvum
and
Cryptosporidium hominis
are two related species of apicomplexan protozoa responsible for the majority of human cases of cryptosporidiosis. In spite of their considerable public health impact, little is known about the population structures of these species. In this study, a battery of
C. parvum
and
C. hominis
isolates from seven countries was genotyped using a nine-locus DNA subtyping scheme. To assess the existence of geographical partitions, the multilocus genotype data were mined using a cluster analysis based on the nearest-neighbor principle. Within each country, the population genetic structures were explored by combining diversity statistical tests, linkage disequilibrium, and eBURST analysis. For both parasite species, a quasi-complete phylogenetic segregation was observed among the countries. Cluster analysis accurately identified recently introduced isolates. Rather than conforming to a strict paradigm of either a clonal or a panmictic population structure, data are consistent with a flexible reproductive strategy characterized by the cooccurrence of both propagation patterns. The relative contribution of each pattern appears to vary between the regions, perhaps dependent on the prevailing ecological determinants of transmission.
Quantification and Genotyping of Torque Teno Virus at a Wastewater Treatment Plant in Japan
Authors: Haramoto Eiji , Katayama Hiroyuki , Ohgaki Shinichiro 
Published: October 2008

ABSTRACT

Torque teno virus (TTV) DNA was quantitatively detected in influent and effluent samples collected from a wastewater treatment plant in Japan, with the highest concentration being 4.8 × 10
4
copies/liter. Genogroup-specific nested PCR demonstrated that TTV of genogroup 3 was the most abundant in wastewater among the five genogroups tested.
Regulation of Aromatic Alcohol Production in
Candida albicans
Authors: Ghosh Suman , Kebaara Bessie W. , Atkin Audrey L. , Nickerson Kenneth W. 
Published: October 2008

ABSTRACT

Colonization by the fungal pathogen
Candida albicans
varies significantly, depending upon the pH and availability of oxygen. Because of our interest in extracellular molecules as potential quorum-sensing molecules, we examined the physiological conditions which regulate the production of the aromatic alcohols, i.e., phenethyl alcohol, tyrosol, and tryptophol. The production of these fusel oils has been well studied for
Saccharomyces cerevisiae
. Our data show that aromatic alcohol yields for
C. albicans
are determined by growth conditions. These conditions include the availability of aromatic amino acids, the pH, oxygen levels, and the presence of ammonium salts. For example, for wild-type
C. albicans
, tyrosol production varied 16-fold merely with the inclusion of tyrosine or ammonium salts in the growth medium. Aromatic alcohol production also depends on the transcription regulator Aro80p. Our results are consistent with aromatic alcohol production—aromatic transaminases (gene products for
ARO8
and
ARO9
), aromatic decarboxylase (
ARO10
), and alcohol dehydrogenase (
ADH
)—via the fusel oil pathway. The expression of
ARO8, ARO9
, and
ARO10
is also pH dependent.
ARO8
and
ARO9
were alkaline upregulated, while
ARO10
was alkaline downregulated. The alkaline-dependent change in expression of
ARO8
was Rim101 independent, while the expression of
ARO9
was Rim101 dependent.
Comparison of Electrode Reduction Activities of
Geobacter sulfurreducens
and an Enriched Consortium in an Air-Cathode Microbial Fuel Cell
Authors: Ishii Shun'ichi , Watanabe Kazuya , Yabuki Soichi , Logan Bruce E. , Sekiguchi Yuji 
Published: October 2008

ABSTRACT

An electricity-generating bacterium,
Geobacter sulfurreducens
PCA, was inoculated into a single-chamber, air-cathode microbial fuel cell (MFC) in order to determine the maximum electron transfer rate from bacteria to the anode. To create anodic reaction-limiting conditions, where electron transfer from bacteria to the anode is the rate-limiting step, anodes with electrogenic biofilms were reduced in size and tests were conducted using anodes of six different sizes. The smallest anode (7 cm
2
, or 1.5 times larger than the cathode) achieved an anodic reaction-limiting condition as a result of a limited mass of bacteria on the electrode. Under these conditions, the limiting current density reached a maximum of 1,530 mA/m
2
, and power density reached a maximum of 461 mW/m
2
. Per-biomass efficiency of the electron transfer rate was constant at 32 fmol cell
−1
day
−1
(178 μmol g of protein
−1
min
−1
), a rate comparable to that with solid iron as the electron acceptor but lower than rates achieved with fumarate or soluble iron. In comparison, an enriched electricity-generating consortium reached 374 μmol g of protein
−1
min
−1
under the same conditions, suggesting that the consortium had a much greater capacity for electrode reduction. These results demonstrate that per-biomass electrode reduction rates (calculated by current density and biomass density on the anode) can be used to help make better comparisons of electrogenic activity in MFCs.