bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Desiccation on Tolerance ofSalmonella entericato Multiple Stresses
Authors: Gruzdev Nadia , Pinto Riky , Sela Shlomo 
Published: January 2011

ABSTRACTReducing the available water in food is a long-established method for controlling bacterial growth in the food industry. Nevertheless, food-borne outbreaks of salmonellosis due to consumption of dry foods have been continuously reported. Previous studies showed that driedSalmonellacells acquire high tolerance to heat and ethanol. In order to examine if dehydration also induces tolerance to other stressors, driedSalmonella entericaserotype Typhimurium cells were exposed to multiple stresses, and their viability was assessed. Indeed, desiccatedS. Typhimurium acquired higher tolerance to multiple stressors than nondesiccated cells. The dried cells were significantly more resistant to most stressors, including ethanol (10 to 30%, 5 min), sodium hypochlorite (10 to 100 ppm, 10 min), didecyl dimethyl ammonium chloride (0.05 to 0.25%, 5 min), hydrogen peroxide (0.5 to 2.0%, 30 min), NaCl (0.1 to 1 M, 2 h), bile salts (1 to 10%, 2 h), dry heat (100°C, 1 h), and UV irradiation (125 μW/cm2, 25 min). In contrast, exposure ofSalmonellato acetic and citric acids reduced the survival of the dried cells (1.5 log) compared to that of nondesiccated cells (0.5 log). Three otherS. entericaserotypes,S. Enteritidis,S. Newport, andS. Infantis, had similar stress responses asS. Typhimurium, whileS. Hadar was much more susceptible and gained tolerance to only a few stressors. Our findings indicate that dehydration induces cross-tolerance to multiple stresses inS. enterica, demonstrating the limitations of current chemical and physical treatments utilized by the food industry to inactivate food-borne pathogens.
Lambda Red-Mediated Genetic Modification of the Insect Endosymbiont
Sodalis glossinidius
Authors: Pontes Mauricio H. , Dale Colin 
Published: January 2011

ABSTRACT

In the current study, we adapted and optimized the lambda Red recombineering strategy to genetically manipulate the fastidious insect endosymbiont
Sodalis glossinidius
. This work greatly facilitates the application of genetics to the study of insect symbionts and should also prove useful in the context of long-awaited paratransgenic insect control strategies.
Influence of the Host Contact Sequence on the Outcome of Competition among
Aspergillus flavus
Isolates during Host Tissue Invasion
Authors: Mehl H. L. , Cotty P. J. 
Published: January 2011

ABSTRACT

Biological control of aflatoxin contamination by
Aspergillus flavus
is achieved through competitive exclusion of aflatoxin producers by atoxigenic strains. Factors dictating the extent to which competitive displacement occurs during host infection are unknown. The role of initial host contact in competition between pairs of
A. flavus
isolates coinfecting maize kernels was examined. Isolate success during tissue invasion and reproduction was assessed by quantification of isolate-specific single nucleotide polymorphisms using pyrosequencing. Isolates were inoculated either simultaneously or 1 h apart. Increased success during competition was conferred to the first isolate to contact the host independent of that isolate's innate competitive ability. The first-isolate advantage decreased with the conidial concentration, suggesting capture of limited resources on kernel surfaces contributes to competitive exclusion. Attempts to modify access to putative attachment sites by either coating kernels with dead conidia or washing kernels with solvents did not influence the success of the first isolate, suggesting competition for limited attachment sites on kernel surfaces does not mediate first-isolate advantage. The current study is the first to demonstrate an immediate competitive advantage conferred to
A. flavus
isolates upon host contact and prior to either germ tube emergence or host colonization. This suggests the timing of host contact is as important to competition during disease cycles as innate competitive ability. Early dispersal to susceptible crop components may allow maintenance within
A. flavus
populations of genetic types with low competitive ability during host tissue invasion.
Transcriptome Analysis of an Antibiotic Downregulator Mutant and Synergistic Actinorhodin Stimulation via Disruption of a Precursor Flux Regulator in
Streptomyces coelicolor
Authors: Kim Seon-Hye , Lee Han-Na , Kim Hye-Jin , Kim Eung-Soo 
Published: January 2011

ABSTRACT

Through microarray analysis of an antibiotic-downregulator-deleted
Streptomyces coelicolor
Δ
wblA
ΔSCO1712 mutant, 28
wblA
- and SCO1712-dependent genes were identified and characterized. Among 14
wblA
- and SCO1712-independent genes, a carbon flux regulating 6-phosphofructokinase SCO5426 was additionally disrupted in the Δ
wblA
ΔSCO1712 mutant and further stimulated actinorhodin production in
S. coelicolor
, implying that both regulatory and precursor flux pathways could be synergistically optimized for antibiotic production.
ArcobacterPopulation Dynamics in Pigs on Farrow-to-Finish Farms
Authors: De Smet Sarah , De Zutter Lieven , Debruyne Lies , Vangroenweghe Frédéric , Vandamme Peter , Houf Kurt 
Published: January 2011

ABSTRACTHealthy pigs are an important reservoir for the emerging human pathogenArcobacterwhich can result in contamination of porcine carcasses and pork and the spread of arcobacters into the environment. Up to now, the excretion of arcobacters by pigs has been studied, but information about the transmission routes in fattening pigs is lacking. The present study aimed to elucidate theArcobacterpopulation dynamics in pigs during the fattening period on four farrow-to-finish farms. On each farm, 30 clinically healthy, 12-week-old piglets were selected. Fecal samples were collected on 10 sampling occasions until a slaughter age of 30 weeks was reached.Arcobacterspp. were isolated by a selective method and identified by multiplex PCR. The genetic diversity was examined by amplified fragment length polymorphism and enterobacterial repetitive intergenic consensus PCR. TheArcobacterpresence in the fecal samples on the four farms ranged from 11.3 to 50.0%, with excretion levels of up to 104CFU/g feces. The ratio in whichArcobacterspecies were isolated varied between the farms and over time. Characterization revealed a high degree of genotypic diversity among the isolates.Arcobacterstrains persisted and spread within the finishing unit during the fattening period. The occurrence of both unique and shared genotypes in pigs in adjacent and nonadjacent pens demonstrates that transmission routes other than fecal-oral transmission occur.
Thermodynamics of Microbial Growth Coupled to Metabolism of Glucose, Ethanol, Short-Chain Organic Acids, and Hydrogen
Authors: Roden Eric E. , Jin Qusheng 
Published: January 2011

ABSTRACT

A literature compilation demonstrated a linear relationship between microbial growth yield and the free energy of aerobic and anaerobic (respiratory and/or fermentative) metabolism of glucose, ethanol, formate, acetate, lactate, propionate, butyrate, and H
2
. This relationship provides a means to estimate growth yields for modeling microbial redox metabolism in soil and sedimentary environments.
Ecological Aspects of the Distribution of Different Autotrophic CO
2
Fixation Pathways
Authors: Berg Ivan A. 
Published: January 2011

ABSTRACT

Autotrophic CO
2
fixation represents the most important biosynthetic process in biology. Besides the well-known Calvin-Benson cycle, five other totally different autotrophic mechanisms are known today. This minireview discusses the factors determining their distribution. As will be made clear, the observed diversity reflects the variety of the organisms and the ecological niches existing in nature.
Extended-Spectrum Beta-Lactamase Gene Sequences in Gram-Negative Saprophytes on Retail Organic and Nonorganic Spinach
Authors: Raphael Eva , Wong Lisa K. , Riley Lee W. 
Published: January 2011

ABSTRACT

A substantial proportion of infections caused by drug-resistant Gram-negative bacteria (GNB) in community and health care settings are recognized to be caused by evolutionarily related GNB strains. Their global spread has been suggested to occur due to human activities, such as food trade and travel. These multidrug-resistant GNB pathogens often harbor mobile drug resistance genes that are highly conserved in their sequences. Because they appear across different GNB species, these genes may have origins other than human pathogens. We hypothesized that saprophytes in common human food products may serve as a reservoir for such genes. Between July 2007 and April 2008, we examined 25 batches of prepackaged retail spinach for cultivatable GNB population structure by 16S rRNA gene sequencing and for antimicrobial drug susceptibility testing and the presence of extended-spectrum beta-lactamase (ESBL) genes. We found 20 recognized GNB species among 165 (71%) of 231 randomly selected colonies cultured from spinach. Twelve strains suspected to express ESBLs based on resistance to cefotaxime and ceftazidime were further examined for
bla
CTX-M
and
bla
TEM
genes. We found a 712-bp sequence in
Pseudomonas teessidea
that was 100% identical to positions 10 to 722 of an 876-bp
bla
CTX-M-15
gene of an
E. coli
strain. Additionally, we identified newly recognized ESBL
bla
RAHN-2
sequences from
Rahnella aquatilis
. These observations demonstrate that saprophytes in common fresh produce can harbor drug resistance genes that are also found in internationally circulating strains of GNB pathogens; such a source may thus serve as a reservoir for drug resistance genes that ultimately enter pathogens to affect human health.
Terminal Olefin (1-Alkene) Biosynthesis by a Novel P450 Fatty Acid Decarboxylase from
Jeotgalicoccus
Species
Authors: Rude Mathew A. , Baron Tarah S. , Brubaker Shane , Alibhai Murtaza , Del Cardayre Stephen B. , Schirmer Andreas 
Published: January 2011

ABSTRACT

Terminal olefins (1-alkenes) are natural products that have important industrial applications as both fuels and chemicals. However, their biosynthesis has been largely unexplored. We describe a group of bacteria,
Jeotgalicoccus
spp., which synthesize terminal olefins, in particular 18-methyl-1-nonadecene and 17-methyl-1-nonadecene. These olefins are derived from intermediates of fatty acid biosynthesis, and the key enzyme in
Jeotgalicoccus
sp. ATCC 8456 is a terminal olefin-forming fatty acid decarboxylase. This enzyme,
Jeotgalicoccus
sp. OleT (OleT
JE
), was identified by purification from cell lysates, and its encoding gene was identified from a draft genome sequence of
Jeotgalicoccus
sp. ATCC 8456 using reverse genetics. Heterologous expression of the identified gene conferred olefin biosynthesis to
Escherichia coli.
OleT
JE
is a P450 from the cyp152 family, which includes bacterial fatty acid hydroxylases. Some cyp152 P450 enzymes have the ability to decarboxylate and to hydroxylate fatty acids (in α- and/or β-position), suggesting a common reaction intermediate in their catalytic mechanism and specific structural determinants that favor one reaction over the other. The discovery of these terminal olefin-forming P450 enzymes represents a third biosynthetic pathway (in addition to alkane and long-chain olefin biosynthesis) to convert fatty acid intermediates into hydrocarbons. Olefin-forming fatty acid decarboxylation is a novel reaction that can now be added to the catalytic repertoire of the versatile cytochrome P450 enzyme family.
Subpopulation-Specific Metabolic Pathway Usage in Mixed Cultures as Revealed by Reporter Protein-Based
13
C Analysis
Authors: Rühl Martin , Hardt Wolf-Dietrich , Sauer Uwe 
Published: January 2011

ABSTRACT

Most large-scale biological processes, like global element cycling or decomposition of organic matter, are mediated by microbial consortia. Commonly, the different species in such consortia exhibit mutual metabolic dependencies that include the exchange of nutrients. Despite the global importance, surprisingly little is known about the metabolic interplay between species in particular subpopulations. To gain insight into the intracellular fluxes of subpopulations and their interplay within such mixed cultures, we developed here a
13
C flux analysis approach based on affinity purification of the recombinant fusion glutathione
S
-transferase (GST) and green fluorescent protein (GFP) as a reporter protein. Instead of detecting the
13
C labeling patterns in the typically used amino acids from the total cellular protein, our method detects these
13
C patterns in amino acids from the reporter protein that has been expressed in only one species of the consortium. As a proof of principle, we validated our approach by mixed-culture experiments of an
Escherichia coli
wild type with two metabolic mutants. The reporter method quantitatively resolved the expected mutant-specific metabolic phenotypes down to subpopulation fractions of about 1%.
The Pathogenic Fungus Paracoccidioides brasiliensis Exports Extracellular Vesicles Containing Highly Immunogenic α-Galactosyl Epitopes
Authors: Vallejo Milene C. , Matsuo Alisson L. , Ganiko Luciane , Medeiros Lia C. Soares , Miranda Kildare , Silva Luiz S. , Freymüller-Haapalainen Edna , Sinigaglia-Coimbra Rita , Almeida Igor C. , Puccia Rosana 
Published: January 2011

ABSTRACTExosome-like vesicles containing virulence factors, enzymes, and antigens have recently been characterized in fungal pathogens, such asCryptococcus neoformansandHistoplasma capsulatum. Here, we describe extracellular vesicles carrying highly immunogenic α-linked galactopyranosyl (α-Gal) epitopes inParacoccidioides brasiliensis. P. brasiliensisis a dimorphic fungus that causes human paracoccidioidomycosis (PCM). For vesicle preparations, cell-free supernatant fluids from yeast cells cultivated in Ham's defined medium-glucose were concentrated in an Amicon ultrafiltration system and ultracentrifuged at 100,000 ×g. P. brasiliensisantigens were present in preparations from phylogenetically distinct isolates Pb18 and Pb3, as observed in immunoblots revealed with sera from PCM patients. In an enzyme-linked immunosorbent assay (ELISA), vesicle components containing α-Gal epitopes reacted strongly with anti-α-Gal antibodies isolated from both Chagas' disease and PCM patients, withMarasmius oreadesagglutinin (MOA) (a lectin that recognizes terminal α-Gal), but only faintly with natural anti-α-Gal. Reactivity was inhibited after treatment with α-galactosidase. Vesicle preparations analyzed by electron microscopy showed vesicular structures of 20 to 200 nm that were labeled both on the surface and in the lumen with MOA. InP. brasiliensiscells, components carrying α-Gal epitopes were found distributed on the cell wall, following a punctuated confocal pattern, and inside large intracellular vacuoles. Lipid-free vesicle fractions reacted with anti-α-Gal in ELISA only when not digested with α-galactosidase, while reactivity with glycoproteins was reduced after β-elimination, which is indicative of partial O-linked chain localization. Our findings open new areas to explore in terms of host-parasite relationships in PCM and the role playedin vivoby vesicle components and α-galactosyl epitopes.
Nutrient Transport and Pathogenesis in Selected Parasitic Protozoa
Authors: Landfear Scott M. 
Published: January 2011

ABSTRACTParasitic protozoa, such as malaria parasites, trypanosomes, andLeishmania, acquire a plethora of nutrients from their hosts, employing transport proteins located in the plasma membrane of the parasite. Application of molecular genetic approaches and the completion of genome projects have allowed the identification and functional characterization of a cohort of transporters and their genes in these parasites. This review focuses on a subset of these permeases that have been studied in some detail, that import critical nutrients, and that provide examples of approaches being undertaken broadly with these and other parasite transporters. Permeases reviewed include those for hexoses, purines, iron, polyamines, carboxylates, and amino acids. Topics of special emphasis include structure-function approaches, critical roles for transporters in parasite viability and physiology, regulation of transporter expression, and subcellular targeting. Investigations of parasite transporters impact a broad spectrum of basic biological problems in these protozoa.
Interaction of SNF1 Protein Kinase with Its Activating Kinase Sak1
Authors: Liu Yang , Xu Xinjing , Carlson Marian 
Published: January 2011

ABSTRACT

The
Saccharomyces cerevisiae
SNF1 protein kinase, a member of the SNF1/AMP-activated protein kinase (AMPK) family, is activated by three kinases, Sak1, Tos3, and Elm1, which phosphorylate the Snf1 catalytic subunit on Thr-210 in response to glucose limitation and other stresses. Sak1 is the primary Snf1-activating kinase and is associated with Snf1 in a complex. Here we examine the interaction of Sak1 with SNF1. We report that Sak1 coimmunopurifies with the Snf1 catalytic subunit from extracts of both glucose-replete and glucose-limited cultures and that interaction occurs independently of the phosphorylation state of Snf1 Thr-210, Snf1 catalytic activity, and other SNF1 subunits. Sak1 interacts with the Snf1 kinase domain, and nonconserved sequences C terminal to the Sak1 kinase domain mediate interaction with Snf1 and augment the phosphorylation and activation of Snf1. The Sak1 C terminus is modified in response to glucose depletion, dependent on SNF1 activity. Replacement of the C terminus of Elm1 (or Tos3) with that of Sak1 enhanced the ability of the Elm1 kinase domain to interact with and phosphorylate Snf1. These findings indicate that the C terminus of Sak1 confers its function as the primary Snf1-activating kinase and suggest that the physical association of Sak1 with SNF1 facilitates responses to environmental change.
ThetibAdherence Locus of EnterotoxigenicEscherichia coliIs Regulated by Cyclic AMP Receptor Protein
Authors: Espert Shirley M. , Elsinghorst Eric A. , Munson George P. 
Published: January 2011

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) is a Gram-negative enteric pathogen that causes profuse watery diarrhea through the elaboration of heat-labile and/or heat-stable toxins. Virulence is also dependent upon the expression of adhesive pili and afimbrial adhesins that allow the pathogen to adhere to the intestinal epithelium or mucosa. Both types of enterotoxins are regulated at the level of transcription by cyclic AMP (cAMP) receptor protein (CRP). To further our understanding of virulence gene regulation, anin silicoapproach was used to identify putative CRP binding sites in the genome ofH10407(O78:H11), an ETEC strain that was originally isolated from the stool of a Bangledeshi patient with cholera-like symptoms circa 1971. One of the predicted binding sites was located within an intergenic region upstream oftibDBCA. TibA is an autotransporter and afimbrial adhesin that is glycosylated by TibC. Expression of the TibA glycoprotein was abolished in anH10407crpmutant and restored whencrpwas provided intrans. TibA-dependent aggregation was also abolished in acyaA::kanstrain and restored by addition of exogenous cAMP to the growth medium. DNase I footprinting confirmed that the predicted site upstream oftibDBCAis bound by CRP. Point mutations within the CRP binding site were found to abolish or significantly impair CRP-dependent activation of thetibDBpromoter. Thus, these studies demonstrate that CRP positively regulates the expression of the glycosylated afimbrial adhesin TibA through occupancy of a binding site withintibDBp.
Purification and Characterization of Dimethylsulfide Monooxygenase fromHyphomicrobium sulfonivorans
Authors: Boden Rich , Borodina Elena , Wood Ann P. , Kelly Donovan P. , Murrell J. Colin , Schäfer Hendrik 
Published: January 2011

ABSTRACTDimethylsulfide (DMS) is a volatile organosulfur compound which has been implicated in the biogeochemical cycling of sulfur and in climate control. Microbial degradation is a major sink for DMS. DMS metabolism in some bacteria involves its oxidation by a DMS monooxygenase in the first step of the degradation pathway; however, this enzyme has remained uncharacterized until now. We have purified a DMS monooxygenase fromHyphomicrobium sulfonivorans, which was previously isolated from garden soil. The enzyme is a member of the flavin-linked monooxygenases of the luciferase family and is most closely related to nitrilotriacetate monooxygenases. It consists of two subunits: DmoA, a 53-kDa FMNH2-dependent monooxygenase, and DmoB, a 19-kDa NAD(P)H-dependent flavin oxidoreductase. Enzyme kinetics were investigated with a range of substrates and inhibitors. The enzyme had aKmof 17.2 (± 0.48) μM for DMS (kcat= 5.45 s−1) and aVmaxof 1.25 (± 0.01) μmol NADH oxidized min−1(mg protein−1). It was inhibited by umbelliferone, 8-anilinonaphthalenesulfonate, a range of metal-chelating agents, and Hg2+, Cd2+, and Pb2+ions. The purified enzyme had no activity with the substrates of related enzymes, including alkanesulfonates, aldehydes, nitrilotriacetate, or dibenzothiophenesulfone. The gene encoding the 53-kDa enzyme subunit has been cloned and matched to the enzyme subunit by mass spectrometry. DMS monooxygenase represents a new class of FMNH2-dependent monooxygenases, based on its specificity for dimethylsulfide and the molecular phylogeny of its predicted amino acid sequence. The gene encoding the large subunit of DMS monooxygenase is colocated with genes encoding putative flavin reductases, homologues of enzymes of inorganic and organic sulfur compound metabolism, and enzymes involved in riboflavin synthesis.
Control of Heme Homeostasis inCorynebacterium glutamicumby the Two-Component System HrrSA
Authors: Frunzke Julia , Gätgens Cornelia , Brocker Melanie , Bott Michael 
Published: January 2011

ABSTRACTThe response regulator HrrA of the HrrSA two-component system (previously named CgtSR11) was recently found to be repressed by the global iron-dependent regulator DtxR inCorynebacterium glutamicum. Here, we provide evidence that HrrA mediates heme-dependent gene regulation in this nonpathogenic soil bacterium. Growth experiments and DNA microarray analysis revealed thatC. glutamicumis able to use hemin as an alternative iron source and emphasize the involvement of the putative hemin ABC transporter HmuTUV and heme oxygenase (HmuO) in heme utilization. As a central part of this study, we investigated the regulon of the response regulator HrrA via comparative transcriptome analysis of anhrrAdeletion mutant andC. glutamicumwild-type strain in combination with DNA-protein interaction studies with purified HrrA protein. Our data provide evidence for a heme-dependent transcriptional activation of heme oxygenase. Based on our results, it can be furthermore deduced that HrrA activates the expression of heme-containing components of the respiratory chain, namely,ctaDand thectaE-qcrCABoperon encoding subunits I and III of cytochromeaa3oxidase and three subunits of the cytochromebc1complex. In addition, HrrA was found to repress almost all genes involved in heme biosynthesis, including those for glutamyl-tRNA reductase (hemA), uroporphyrinogen decarboxylase (hemE), and ferrochelatase (hemH). Growth experiments with anhrrAdeletion mutant showed that this strain is significantly impaired in heme utilization. In summary, our results provide evidence for a central role of the HrrSA system in the control of heme homeostasis inC. glutamicum.