bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial Contents of Vacuum Cleaner Bag Dust and Emitted Bioaerosols and Their Implications for Human Exposure Indoors
Authors: Veillette Marc , Knibbs Luke D. , Pelletier Ariane , Charlebois Remi , Blais Lecours Pascale , He Congrong , Morawska Lidia , Duchaine Caroline 
Published: August 2013

ABSTRACT

Vacuum cleaners can release large concentrations of particles, both in their exhaust air and from resuspension of settled dust. However, the size, variability, and microbial diversity of these emissions are unknown, despite evidence to suggest they may contribute to allergic responses and infection transmission indoors. This study aimed to evaluate bioaerosol emission from various vacuum cleaners. We sampled the air in an experimental flow tunnel where vacuum cleaners were run, and their airborne emissions were sampled with closed-face cassettes. Dust samples were also collected from the dust bag. Total bacteria, total archaea,
Penicillium
/
Aspergillus
, and total
Clostridium
cluster 1 were quantified with specific quantitative PCR protocols, and emission rates were calculated.
Clostridium botulinum
and antibiotic resistance genes were detected in each sample using endpoint PCR. Bacterial diversity was also analyzed using denaturing gradient gel electrophoresis (DGGE), image analysis, and band sequencing. We demonstrated that emission of bacteria and molds (
Penicillium
/
Aspergillus
) can reach values as high as 1E5 cell equivalents/min and that those emissions are not related to each other. The bag dust bacterial and mold content was also consistent across the vacuums we assessed, reaching up to 1E7 bacterial or mold cell equivalents/g. Antibiotic resistance genes were detected in several samples. No archaea or
C. botulinum
was detected in any air samples. Diversity analyses showed that most bacteria are from human sources, in keeping with other recent results. These results highlight the potential capability of vacuum cleaners to disseminate appreciable quantities of molds and human-associated bacteria indoors and their role as a source of exposure to bioaerosols.
Microgradients of pH Do Not Occur around Lactococcus Colonies in a Model Cheese
Authors: Jeanson Sophie , Floury Juliane , Issulahi Al Amine , Madec Marie-Noëlle , Thierry Anne , Lortal Sylvie 
Published: August 2013

ABSTRACT
Lactococci inoculated into cheese grow as colonies producing lactic acid. The pH microgradients were investigated around colonies in a complex food such as cheese. The results, obtained using a nondestructive technique, demonstrated that pH microgradients did not occur regardless of the acidification kinetics and the size of the colony.
X-Ray Absorption Near-Edge Structure (XANES) Spectroscopy Study of the Interaction of Silver Ions with Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli
Authors: Bovenkamp Gudrun Lisa , Zanzen Ulrike , Krishna Katla Sai , Hormes Josef , Prange Alexander 
Published: August 2013

ABSTRACT

Silver ions are widely used as antibacterial agents, but the basic molecular mechanism of this effect is still poorly understood. X-ray absorption near-edge structure (XANES) spectroscopy at the Ag
LIII
, S
K
, and P
K
edges reveals the chemical forms of silver in
Staphylococcus aureus
and
Escherichia coli
(Ag
+
treated). The Ag
LIII
-edge XANES spectra of the bacteria are all slightly different and very different from the spectra of silver ions (silver nitrate and silver acetate), which confirms that a reaction occurs. Death or inactivation of bacteria was observed by plate counting and light microscopy. Silver bonding to sulfhydryl groups (Ag-S) in cysteine and Ag-N or Ag-O bonding in histidine, alanine, and
dl
-aspartic acid was detected by using synthesized silver-amino acids. Significantly lower silver-cysteine content, coupled with higher silver-histidine content, in Gram-positive
S. aureus
and
Listeria monocytogenes
cells indicates that the peptidoglycan multilayer could be buffering the biocidal effect of silver on Gram-positive bacteria, at least in part. Bonding of silver to phosphate groups was not detected. Interaction with DNA or proteins can occur through Ag-N bonding. The formation of silver-cysteine can be confirmed for both bacterial cell types, which supports the hypothesis that enzyme-catalyzed reactions and the electron transport chain within the cell are disrupted.
Behavior of Yersinia enterocolitica in the Presence of the Bacterivorous Acanthamoeba castellanii
Authors: Lambrecht E. , Baré J. , Van Damme I. , Bert W. , Sabbe K. , Houf K. 
Published: August 2013

ABSTRACT

Free-living protozoa play an important role in the ecology and epidemiology of human-pathogenic bacteria. In the present study, the interaction between
Yersinia enterocolitica
, an important food-borne pathogen, and the free-living amoeba
Acanthamoeba castellanii
was studied. Several cocultivation assays were set up to assess the resistance of
Y. enterocolitica
to
A. castellanii
predation and the impact of environmental factors and bacterial strain-specific characteristics. Results showed that all
Y. enterocolitica
strains persist in association with
A. castellanii
for at least 14 days, and associations with
A. castellanii
enhanced survival of
Yersinia
under nutrient-rich conditions at 25°C and under nutrient-poor conditions at 37°C. Amoebae cultivated in the supernatant of one
Yersinia
strain showed temperature- and time-dependent permeabilization. Intraprotozoan survival of
Y. enterocolitica
depended on nutrient availability and temperature, with up to 2.8 log CFU/ml bacteria displaying intracellular survival at 7°C for at least 4 days in nutrient-rich medium. Transmission electron microscopy was performed to locate the
Yersinia
cells inside the amoebae. As
Yersinia
and
Acanthamoeba
share similar ecological niches, this interaction identifies a role of free-living protozoa in the ecology and epidemiology of
Y. enterocolitica
.
Environmental Surveillance of Human Parechoviruses in Sewage in the Netherlands
Authors: Lodder W. J. , Wuite M. , de Roda Husman A. M. , Rutjes S. A. 
Published: August 2013

ABSTRACT

The circulation of human parechoviruses (HPeVs) in the population was studied by environmental surveillance comprising of molecular analyses of sewage samples (
n
= 89) that were collected from 15 different locations in the Netherlands. Samples were taken from sewage originating from schools (
n
= 9) or from parts of municipalities (
n
= 6) during the Dutch school year 2010-2011. At 13/15 locations HPeV1, HPeV3, or HPeV6 RNA was detected at least once; however, sequence diversity did not reflect associations in time or place. A higher percentage of positives was observed in the samples originating from the municipalities. It was demonstrated that HPeV circulated in the studied population to a higher extent than would be expected from the current knowledge on infections predominating in young children.
Functional and Expression Analysis of the Metal-Inducible
dmeRF
System from Rhizobium leguminosarum bv. viciae
Authors: Rubio-Sanz L. , Prieto R. I. , Imperial J. , Palacios J. M. , Brito B. 
Published: August 2013

ABSTRACT

A gene encoding a homolog to the cation diffusion facilitator protein DmeF from
Cupriavidus metallidurans
has been identified in the genome of
Rhizobium leguminosarum
UPM791. The
R. leguminosarum dmeF
gene is located downstream of an open reading frame (designated
dmeR
) encoding a protein homologous to the nickel- and cobalt-responsive transcriptional regulator RcnR from
Escherichia coli
. Analysis of gene expression showed that the
R. leguminosarum dmeRF
genes are organized as a transcriptional unit whose expression is strongly induced by nickel and cobalt ions, likely by alleviating the repressor activity of DmeR on
dmeRF
transcription. An
R. leguminosarum dmeRF
mutant strain displayed increased sensitivity to Co(II) and Ni(II), whereas no alterations of its resistance to Cd(II), Cu(II), or Zn(II) were observed. A decrease of symbiotic performance was observed when pea plants inoculated with an
R. leguminosarum dmeRF
deletion mutant strain were grown in the presence of high concentrations of nickel and cobalt. The same mutant induced significantly lower activity levels of NiFe hydrogenase in microaerobic cultures. These results indicate that the
R. leguminosarum
DmeRF system is a metal-responsive efflux mechanism acting as a key element for metal homeostasis in
R. leguminosarum
under free-living and symbiotic conditions. The presence of similar
dmeRF
gene clusters in other
Rhizobiaceae
suggests that the
dmeRF
system is a conserved mechanism for metal tolerance in legume endosymbiotic bacteria.
mhpT
Encodes an Active Transporter Involved in 3-(3-Hydroxyphenyl)Propionate Catabolism by Escherichia coli K-12
Authors: Xu Ying , Chen Bing , Chao Hongjun , Zhou Ning-Yi 
Published: August 2013

ABSTRACT

Escherichia coli
K-12 utilizes 3-(3-hydroxyphenyl)propionate (3HPP) as a sole carbon and energy source. Among the genes in its catabolic cluster in the genome,
mhpT
was proposed to encode a hypothetical transporter. Since no transporter for 3HPP uptake has been identified, we investigated whether MhpT is responsible for 3HPP uptake. MhpT fused with green fluorescent protein was found to be located at the periphery of cells by confocal microscopy, consistent with localization to the cytoplasmic membrane. Gene knockout and complementation studies clearly indicated that
mhpT
is essential for 3HPP catabolism in
E. coli
K-12 W3110 at pH 8.2. Uptake assays with
14
C-labeled substrates demonstrated that strain W3110 and strain W3110Δ
mhpT
containing recombinant MhpT specifically transported 3HPP but not benzoate, 3-hydroxybenzoate, or gentisate into cells. Energy dependence assays suggested that MhpT-mediated 3HPP transport was driven by the proton motive force. The change of Ala-272 of MhpT to a histidine, surprisingly, resulted in enhanced transport activity, and strain W3110Δ
mhpT
containing the MhpT A272H mutation had a slightly higher growth rate than the wild-type strain at pH 8.2. Hence, we demonstrated that MhpT is a specific 3HPP transporter and vital for
E. coli
K-12 W3110 growth on this substrate under basic conditions.
Prevalence of Hemolysin Genes and Comparison of
ehxA
Subtype Patterns in Shiga Toxin-Producing Escherichia coli (STEC) and Non-STEC Strains from Clinical, Food, and Animal Sources
Authors: Lorenz Sandra C. , Son Insook , Maounounen-Laasri Anna , Lin Andrew , Fischer Markus , Kase Julie A. 
Published: August 2013

ABSTRACT

Shiga toxin-producing
Escherichia coli
(STEC) belonging to certain serogroups (e.g., O157 and O26) can cause serious conditions like hemolytic-uremic syndrome (HUS), but other strains might be equally pathogenic. While virulence factors, like
stx
and
eae
, have been well studied, little is known about the prevalence of the
E. coli
hemolysin genes (
hlyA
,
ehxA
,
e-hlyA
, and
sheA
) in association with these factors. Hemolysins are potential virulence factors, and
ehxA
and
hlyA
have been associated with human illness, but the significance of
sheA
is unknown. Hence, 435
E. coli
strains belonging to 62 different O serogroups were characterized to investigate gene presence and phenotypic expression of hemolysis. We further investigated
ehxA
subtype patterns in
E. coli
isolates from clinical, animal, and food sources. While
sheA
and
ehxA
were widely distributed,
e-hlyA
and
hlyA
were rarely found. Most strains (86.7%) were hemolytic, and significantly more hemolytic (95%) than nonhemolytic strains (49%) carried
stx
and/or
eae
(
P
< 0.0001).
ehxA
subtyping, as performed by using PCR in combination with restriction fragment length polymorphism analysis, resulted in six closely related subtypes (>94.2%), with subtypes A/D being
eae
-negative STECs and subtypes B, C, E, and F
eae
positive. Unexpectedly,
ehxA
subtype patterns differed significantly between isolates collected from different sources (
P
< 0.0001), suggesting that simple linear models of exposure and transmission need modification; animal isolates carried mostly subtypes A/C (39.3%/42.9%), food isolates carried mainly subtype A (81.9%), and clinical isolates carried mainly subtype C (66.4%). Certain O serogroups correlated with particular
ehxA
subtypes: subtype A with O104, O113, and O8; B exclusively with O157; C with O26, O111, and O121.
Monitoring the Metabolic State of Fungal Hyphae and the Presence of Melanin by Nonlinear Spectral Imaging
Authors: Knaus Helene , Blab Gerhard A. , Agronskaia Alexandra V. , van den Heuvel Dave J. , Gerritsen Hans C. , Wösten Han A. B. 
Published: August 2013

ABSTRACT

Label-free nonlinear spectral imaging microscopy (NLSM) records two-photon-excited fluorescence emission spectra of endogenous fluorophores within the specimen. Here, NLSM is introduced as a novel, minimally invasive method to analyze the metabolic state of fungal hyphae by monitoring the autofluorescence of NAD(P)H and flavin adenine dinucleotide (FAD). Moreover, the presence of melanin was analyzed by NLSM. NAD(P)H, FAD, and melanin were used as biomarkers for freshness of mushrooms of
Agaricus bisporus
(white button mushroom) that had been stored at 4°C for 0 to 17 days. During this period, the mushrooms did not show changes in morphology or color detectable by eye. In contrast, FAD/NAD(P)H and melanin/NAD(P)H ratios increased over time. For instance, these ratios increased from 0.92 to 2.02 and from 0.76 to 1.53, respectively, at the surface of mushroom caps that had been harvested by cutting the stem. These ratios were lower under the skin than at the surface of fresh mushrooms (0.78 versus 0.92 and 0.41 versus 0.76, respectively), indicative of higher metabolism and lower pigment formation within the fruiting body. Signals were different not only between tissues of the mushroom but also between neighboring hyphae. These data show that NLSM can be used to determine the freshness of mushrooms and to monitor the postharvest browning process at an early stage. Moreover, these data demonstrate the potential of NLSM to address a broad range of fundamental and applied microbiological processes.
Development of a Tunable Wide-Range Gene Induction System Useful for the Study of Streptococcal Toxin-Antitoxin Systems
Authors: Xie Zhoujie , Qi Fengxia , Merritt Justin 
Published: August 2013

ABSTRACT

Despite the plethora of genetic tools that have been developed for use in
Streptococcus mutans
, the
S. mutans
genetic system still lacks an effective gene induction system exhibiting low basal expression and strong inducibility. Consequently, we created two hybrid gene induction cassettes referred to as Xyl-S1 and Xyl-S2. Both Xyl-S cassettes are xylose inducible and controlled by the
Bacillus megaterium
xylose repressor. The Xyl-S cassettes each demonstrated >600-fold-increased reporter activity in the presence of 1.2% (wt/vol) xylose. However, the Xyl-S1 cassette yielded a much higher maximum level of gene expression, whereas the Xyl-S2 cassette exhibited much lower uninduced basal expression. The cassettes also performed similarly in
Streptococcus sanguinis
and
Streptococcus gordonii
, which suggests that they are likely to be useful in a variety of streptococci. We demonstrate how both Xyl-S cassettes are particularly useful for the study of toxin-antitoxin (TA) modules using both the previously characterized
S. mutans mazEF
TA module and a previously uncharacterized HicAB TA module in
S. mutans
. HicAB TA modules are widely distributed among bacteria and archaea, but little is known about their function. We show that HicA serves as the toxin component of the module, while HicB serves as the antitoxin. Our results suggest that, in contrast to that of typical TA modules, HicA toxicity in
S. mutans
is modest at best. The implications of these results for HicAB function are discussed.
U(VI) Reduction by Diverse Outer Surface
c
-Type Cytochromes of Geobacter sulfurreducens
Authors: Orellana Roberto , Leavitt Janet J. , Comolli Luis R. , Csencsits Roseann , Janot Noemie , Flanagan Kelly A. , Gray Arianna S. , Leang Ching , Izallalen Mounir , Mester Tünde , Lovley Derek R. 
Published: August 2013

ABSTRACT

Early studies with
Geobacter sulfurreducens
suggested that outer-surface
c
-type cytochromes might play a role in U(VI) reduction, but it has recently been suggested that there is substantial U(VI) reduction at the surface of the electrically conductive pili known as microbial nanowires. This phenomenon was further investigated. A strain of
G. sulfurreducens
, known as Aro-5, which produces pili with substantially reduced conductivity reduced U(VI) nearly as well as the wild type, as did a strain in which the gene for PilA, the structural pilin protein, was deleted. In order to reduce rates of U(VI) reduction to levels less than 20% of the wild-type rates, it was necessary to delete the genes for the five most abundant outer surface
c
-type cytochromes of
G. sulfurreducens
. X-ray absorption near-edge structure spectroscopy demonstrated that whereas 83% ± 10% of the uranium associated with wild-type cells correspond to U(IV) after 4 h of incubation, with the quintuple mutant, 89% ± 10% of uranium was U(VI). Transmission electron microscopy and X-ray energy dispersion spectroscopy revealed that wild-type cells did not precipitate uranium along pili as previously reported, but U(IV) was precipitated at the outer cell surface. These findings are consistent with those of previous studies, which have suggested that
G. sulfurreducens
requires outer-surface
c
-type cytochromes but not pili for the reduction of soluble extracellular electron acceptors.
Evidence for Benzylsuccinate Synthase Subtypes Obtained by Using Stable Isotope Tools
Authors: Kümmel Steffen , Kuntze Kevin , Vogt Carsten , Boll Matthias , Heider Johann , Richnow Hans H. 
Published: August 2013

ABSTRACT

We studied the benzylsuccinate synthase (Bss) reaction mechanism with respect to the hydrogen-carbon bond cleavage at the methyl group of toluene by using different stable isotope tools. Λ values (slopes of linear regression curves for carbon and hydrogen discrimination) for two-dimensional compound-specific stable isotope analysis (2D-CSIA) of toluene activation by Bss-containing cell extracts (
in vitro
studies) were found to be similar to previously reported data from analogous experiments with whole cells (
in vivo
studies), proving that Λ values generated by whole cells are caused by Bss catalysis. The Bss enzymes of facultative anaerobic bacteria produced smaller Λ values than those of obligate anaerobes. In addition, a partial exchange of a single deuterium atom in benzylsuccinate with hydrogen was observed in experiments with deuterium-labeled toluene. In this study, the Bss enzymes of the tested facultative anaerobes showed 3- to 8-fold higher exchange probabilities than those for the enzymes of the tested obligate anaerobic bacteria. The phylogeny of the Bss variants, determined by sequence analyses of BssA, the gene product corresponding to the α subunit of Bss, correlated with the observed differences in Λ values and hydrogen exchange probabilities. In conclusion, our results suggest subtle differences in the reaction mechanisms of Bss isoenzymes of facultative and obligate anaerobes and show that the putative isoenzymes can be differentiated by 2D-CSIA.
Staphylococcus aureus Mutants Lacking the LytR-CpsA-Psr Family of Enzymes Release Cell Wall Teichoic Acids into the Extracellular Medium
Authors: Chan Yvonne G. Y. , Frankel Matthew B. , Dengler Vanina , Schneewind Olaf , Missiakas Dominique 
Published: August 2013

ABSTRACT

The LytR-CpsA-Psr (LCP) proteins are thought to transfer bactoprenol-linked biosynthetic intermediates of wall teichoic acid (WTA) to the peptidoglycan of Gram-positive bacteria. In
Bacillus subtilis
, mutants lacking all three LCP enzymes do not deposit WTA in the envelope, while
Staphylococcus aureus
Δ
lcp
mutants display impaired growth and reduced levels of envelope phosphate. We show here that the
S. aureus
Δ
lcp
mutant synthesized WTA yet released ribitol phosphate polymers into the extracellular medium. Further, Δ
lcp
mutant staphylococci no longer restricted the deposition of LysM-type murein hydrolases to cell division sites, which was associated with defects in cell shape and increased autolysis. Mutations in
S. aureus
WTA synthesis genes (
tagB
,
tarF
, or
tarJ2
) inhibit growth, which is attributed to the depletion of bactoprenol, an essential component of peptidoglycan synthesis (lipid II). The growth defect of
S. aureus tagB
and
tarFJ
mutants was alleviated by inhibition of WTA synthesis with tunicamycin, whereas the growth defect of the Δ
lcp
mutant was not relieved by tunicamycin treatment or by mutation of
tagO
, whose product catalyzes the first committed step of WTA synthesis. Further, sortase A-mediated anchoring of proteins to peptidoglycan, which also involves bactoprenol and lipid II, was not impaired in the Δ
lcp
mutant. We propose a model whereby the
S. aureus
Δ
lcp
mutant, defective in tethering WTA to the cell wall, cleaves WTA synthesis intermediates, releasing ribitol phosphate into the medium and recycling bactoprenol for peptidoglycan synthesis.
Deciphering the Interplay between Two Independent Functions of the Small RNA Regulator SgrS in Salmonella
Authors: Balasubramanian Divya , Vanderpool Carin K. 
Published: August 2013

ABSTRACT

Bacterial dual-function small RNAs regulate gene expression by RNA-RNA base pairing and also code for small proteins. SgrS is a dual-function small RNA in
Escherichia coli
and
Salmonella
that is expressed under stress conditions associated with accumulation of sugar-phosphates, and its activity is crucial for growth during stress. The base-pairing function of SgrS regulates a number of mRNA targets, resulting in reduced uptake and enhanced efflux of sugars. SgrS also encodes the SgrT protein, which reduces sugar uptake by a mechanism that is independent of base pairing. While SgrS base-pairing activity has been characterized in detail, little is known about how base pairing and translation of
sgrT
are coordinated. In the current study, we utilized a series of mutants to determine how translation of
sgrT
affected the efficiency of base pairing-dependent regulation and vice versa. Mutations that abrogated
sgrT
translation had minimal effects on base-pairing activity. Conversely, mutations that impaired base-pairing interactions resulted in increased SgrT production. Furthermore, while ectopic overexpression of
sgrS
mutant alleles lacking only one of the two functions rescued cell growth under stress conditions, the SgrS base-pairing function alone was indispensable for growth rescue when alleles were expressed from the native locus. Collectively, the results suggest that during stress, repression of sugar transporter synthesis via base pairing with sugar transporter mRNAs is the first priority of SgrS. Subsequently, SgrT is made and acts on preexisting transporters. The combined action of these two functions produces an effective stress response.