bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of Selenite and Detoxification of Elemental Selenium by the Phototrophic Bacterium
Rhodospirillum rubrum
Authors: Kessi J. , Ramuz M. , Wehrli E. , Spycher M. , Bachofen R. 
Published: December 2019

ABSTRACT

The effect of selenite on growth kinetics, the ability of cultures to reduce selenite, and the mechanism of detoxification of selenium were investigated by using
Rhodospirillum rubrum
. Anoxic photosynthetic cultures were able to completely reduce as much as 1.5 mM selenite, whereas in aerobic cultures a 0.5 mM selenite concentration was only reduced to about 0.375 mM. The presence of selenite in the culture medium strongly affected cell division. In the presence of a selenite concentration of 1.5 mM cultures reached final cell densities that were only about 15% of the control final cell density. The cell density remained nearly constant during the stationary phase for all of the selenite concentrations tested, showing that the cells were not severely damaged by the presence of selenite or elemental selenium. Particles containing elemental selenium were observed in the cytoplasm, which led to an increase in the buoyant density of the cells. Interestingly, the change in the buoyant density was reversed after selenite reduction was complete; the buoyant density of the cells returned to the buoyant density of the control cells. This demonstrated that
R. rubrum
expels elemental selenium across the plasma membrane and the cell wall. Accordingly, electron-dense particles were more numerous in the cells during the reduction phase than after the reduction phase.
Characterization of Cadmium Uptake in
Lactobacillus plantarum
and Isolation of Cadmium and Manganese Uptake Mutants
Authors: Hao Zhiqi , Reiske Heinz R. , Wilson David B. 
Published: December 2019

ABSTRACT

Two different Cd
2+
uptake systems were identified in
Lactobacillus plantarum
. One is a high-affinity, high-velocity Mn
2+
uptake system which also takes up Cd
2+
and is induced by Mn
2+
starvation. The calculated

K
m

and
V
max
are 0.26 μM and 3.6 μmol g of dry cell
−1
min
−1
, respectively. Unlike Mn
2+
uptake, which is facilitated by citrate and related tricarboxylic acids, Cd
2+
uptake is weakly inhibited by citrate. Cd
2+
and Mn
2+
are competitive inhibitors of each other, and the affinity of the system for Cd
2+
is higher than that for Mn
2+
. The other Cd
2+
uptake system is expressed in Mn
2+
-sufficient cells, and no

K
m

can be calculated for it because uptake is nonsaturable. Mn
2+
does not compete for transport through this system, nor does any other tested cation, i.e., Zn
2+
, Cu
2+
, Co
2+
, Mg
2+
, Ca
2+
, Fe
2+
, or Ni
2+
. Both systems require energy, since uncouplers completely inhibit their activities. Two Mn
2+
-dependent
L. plantarum
mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn
2+
for growth as the parental strain. Mn
2+
starvation-induced Cd
2+
uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn
2+
or Cd
2+
accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn
2+
and Cd
2+
uptake system.
Prediction of Toxigenic Fungal Growth in Buildings by Using a Novel Modelling System
Authors: Rowan Neil J. , Johnstone Cameron M. , McLean R. Craig , Anderson John G. , Clarke Joe A. 
Published: December 2019

ABSTRACT

There is growing concern about the adverse effects of fungal bioaerosols on the occupants of damp dwellings. Based on an extensive analysis of previously published data and on experiments carried out within this study, critical limits for the growth of the indoor fungi
Eurotium herbariorum
,
Aspergillus versicolor
, and
Stachybotrys chartarum
were mathematically described in terms of growth limit curves (isopleths) which define the minimum combination of temperature (T) and relative humidity (RH) at which growth will occur. Each growth limit curve was generated from a series of data points on a T-RH plot and mathematically fitted by using a third-order polynomial equation of the form RH =
a
3
T
3
+
a
2
T
2
+
a
1
T +
a
0
. This fungal growth prediction model was incorporated within the ESP-
r
(Environmental Systems Performance [
r
stands for “research”]) computer-based program for transient simulation of the energy and environmental performance of buildings. For any specified location, the ESP-
r
system is able to predict the time series evolution of local surface temperature and relative humidity, taking explicit account of constructional moisture flow, moisture generation sources, and air movement. This allows the predicted local conditions to be superimposed directly onto fungal growth curves. The concentration of plotted points relative to the curves allows an assessment of the risk of fungal growth. The system’s predictive capability was tested via laboratory experiments and by comparison with monitored data from a fungus-contaminated house.
Expression of the
ggpS
Gene, Involved in Osmolyte Synthesis in the Marine Cyanobacterium
Synechococcus
sp. Strain PCC 7002, Revealed Regulatory Differences between This Strain and the Freshwater Strain
Synechocystis
sp. Strain PCC 6803
Authors: Engelbrecht Friederike , Marin Kay , Hagemann Martin 
Published: December 2019

ABSTRACT

Synthesis of the osmolyte glucosylglycerol (GG) in the marine cyanobacterium
Synechococcus
sp. strain PCC 7002 was characterized. The
ggpS
gene, which encodes the key enzyme (GG-phosphate synthase [GgpS]) in GG biosynthesis, was cloned by using PCR. A 2,030-bp DNA sequence which contained one open reading frame (ORF) was obtained. The protein deduced from this ORF exhibited 85% similarity to the GgpS of the freshwater cyanobacterium
Synechocystis
sp. strain PCC 6803. The function of the protein was confirmed by generating a
ggpS
null mutant, which was not able to synthesize GG and thus exhibited a salt-sensitive phenotype. Expression of the
ggpS
gene was analyzed in salt-shocked cells by performing Northern blot and immunoblot experiments. While almost no expression was detected in cells grown in low-salt medium, immediately after a salt shock the amounts of
ggpS
mRNA and GgpS protein increased up to 100-fold. The finding that salt-induced expression occurred was confirmed by measuring enzyme activities, which were negligible in control cells but clearly higher in salt-treated
Synechococcus
sp. cells. The salt-induced increase in GgpS activity could be inhibited by adding chloramphenicol, while in protein extracts of the freshwater cyanobacterium
Synechocystis
sp. strain PCC 6803 a constitutive, high level of enzyme activity that was not affected by chloramphenicol was found. A comparison of GG accumulation in the two cyanobacteria revealed that in the marine strain osmolyte synthesis seemed to be regulated mainly by transcriptional control, whereas in the freshwater strain control seemed to be predominantly posttranslational.
Phylogenetic Differentiation of Two Closely Related
Nitrosomonas
spp. That Inhabit Different Sediment Environments in an Oligotrophic Freshwater Lake
Authors: Whitby Corinne B. , Saunders Jon R. , Rodriguez Juana , Pickup Roger W. , McCarthy Alan 
Published: December 2019

ABSTRACT

The population of ammonia-oxidizing bacteria in a temperate oligotrophic freshwater lake was analyzed by recovering 16S ribosomal DNA (rDNA) from lakewater and sediment samples taken throughout a seasonal cycle.
Nitrosospira
and
Nitrosomonas
16S rRNA genes were amplified in a nested PCR, and the identity of the products was confirmed by oligonucleotide hybridization.
Nitrosospira
DNA was readily identified in all samples, and nitrosomonad DNA of the
Nitrosomonas europaea-Nitrosomonas eutropha
lineage was also directly detected, but during the summer months only. Phylogenetic delineation with partial (345 bp) 16S rRNA gene sequences of clones obtained from sediments confirmed the fidelity of the amplified nitrosomonad DNA and identified two sequence clusters closely related to either
N. europaea
or
N. eutropha
that were equated with the littoral and profundal sediment sites, respectively. Determination of 701-bp sequences for 16S rDNA clones representing each cluster confirmed this delineation. A PCR-restriction fragment length polymorphism (RFLP) system was developed that enabled identification of clones containing
N. europaea
and
N. eutropha
16S rDNA sequences, including subclasses therein. It proved possible to analyze 16S rDNA amplified directly from sediment samples to determine the relative abundance of each species compared with that of the other.
N. europaea
and
N. eutropha
are very closely related, and direct evidence for their presence in lake systems is limited. The correlation of each species with a distinct spatial location in sediment is an unusual example of niche adaptation by two genotypically similar bacteria. Their occurrence and relative distribution can now be routinely monitored in relation to environmental variation by the application of PCR-RFLP analysis.
Combined Effects of pH and Sugar on Growth Rate of
Zygosaccharomyces rouxii
, a Bakery Product Spoilage Yeast
Authors: Membré Jeanne-Marie , Kubaczka Martine , Chéné Christine 
Published: December 2019

ABSTRACT

The effects of citric acid-modified pH (pH 2.5, 2.75, 3, 3.5, 4, 4.5, 5, and 5.5) and a 30% glucose–70% sucrose mixture (300, 400, 500, 600, 700, 800, 875, and 900 g/liter) on an osmophilic yeast,
Zygosaccharomyces rouxii
, were determined by using synthetic medium. One hundred experiments were carried out; 50-ml culture flasks were inoculated with 10
3
CFU ml
−1
by using a collection strain and a wild-type strain cocktail. The biomass was measured by counting cell colonies, and growth curves were fitted by using a Baranyi equation. The growth rate decreased linearly with sugar concentration, while the effect of pH was nonlinear. Indeed, the optimal pH range was found to be pH 3.5 to 5, and pH 2.5 resulted in a 30% reduction in the growth rate. Finally, we evaluated the performance of two nonlinear predictive models developed previously to describe bacterial contamination. Equations derived from the Rosso and Ratkowsky models gave similar results; however, the model that included dimensionless terms based on the Ratkowsky equation was preferred because it contained fewer estimated parameters and also because biological interpretation of the results was easier.
Molecular Characterization of Laccase Genes from the Basidiomycete
Coprinus cinereus
and Heterologous Expression of the Laccase Lcc1
Authors: Yaver Debbie S. , Overjero Maria Del Carmen , Xu Feng , Nelson Beth A. , Brown Kim M. , Halkier Torben , Bernauer Sheryl , Brown Stephen H. , Kauppinen Sakari 
Published: December 2019

ABSTRACT

A laccase from
Coprinus cinereus
is active at alkaline pH, an essential property for some potential applications. We cloned and sequenced three laccase genes (
lcc1
,
lcc2
, and
lcc3
) from the ink cap basidiomycete
C. cinereus
. The
lcc1
gene contained 7 introns, while both
lcc2
and
lcc3
contained 13 introns. The predicted mature proteins (Lcc1 to Lcc3) are 58 to 80% identical at the amino acid level. The predicted Lcc1 contains a 23-amino-acid C-terminal extension rich in arginine and lysine, suggesting that C-terminal processing may occur during its biosynthesis. We expressed the Lcc1 protein in
Aspergillus oryzae
and purified it. The Lcc1 protein as expressed in
A. oryzae
has an apparent molecular mass of 66 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and absorption maxima at 278 and 614 nm. Based on the N-terminal protein sequence of the laccase, a 4-residue propeptide was processed during the maturation of the enzyme. The dioxygen specificity of the laccase showed an apparent

K
m

of 21 ± 2 μM and a catalytic constant of 200 ± 10 min
−1
for O
2
with 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) as the reducing substrate at pH 5.5. Lcc1 from
A. oryzae
may be useful in industrial applications. This is the first report of a basidiomycete laccase whose biosynthesis involves both N-terminal and C-terminal processing.
Screening of Probiotic Activities of Forty-Seven Strains of
Lactobacillus
spp. by In Vitro Techniques and Evaluation of the Colonization Ability of Five Selected Strains in Humans
Authors: Jacobsen C. N. , Rosenfeldt Nielsen V. , Hayford A. E. , Møller P. L. , Michaelsen K. F. , Pærregaard A. , Sandström B. , Tvede M. , Jakobsen M. 
Published: December 2019

ABSTRACT

The probiotic potential of 47 selected strains of
Lactobacillus
spp. was investigated. The strains were examined for resistance to pH 2.5 and 0.3% oxgall, adhesion to Caco-2 cells, and antimicrobial activities against enteric pathogenic bacteria in model systems. From the results obtained in vitro, five strains,
Lactobacillus rhamnosus
19070-2,
L. reuteri
DSM 12246,
L. rhamnosus
LGG,
L. delbrueckii
subsp.
lactis
CHCC 2329, and
L. casei
subsp.
alactus
CHCC 3137, were selected for in vivo studies. The daily consumption by 12 healthy volunteers of two doses of 10
10
freeze-dried bacteria of the selected strains for 18 days was followed by a washout period of 17 days. Fecal samples were taken at days 0 and 18 and during the washout period at days 5 and 11.
Lactobacillus
isolates were initially identified by API 50CHL and internal transcribed spacer PCR, and their identities were confirmed by restriction enzyme analysis in combination with pulsed-field gel electrophoresis. Among the tested strains,
L. rhamnosus
19070-2,
L. reuteri
DSM 12246, and
L. rhamnosus
LGG were identified most frequently in fecal samples; they were found in 10, 8, and 7 of the 12 samples tested during the intervention period, respectively, whereas reisolations were less frequent in the washout period. The bacteria were reisolated in concentrations from 10
5
to 10
8
cells/g of feces. Survival and reisolation of the bacteria in vivo appeared to be linked to pH tolerance, adhesion, and antimicrobial properties in vitro.
Bacterial Adhesion at Synthetic Surfaces
Authors: Cunliffe D. , Smart C. A. , Alexander C. , Vulfson E. N. 
Published: December 2019

ABSTRACT

A systematic investigation into the effect of surface chemistry on bacterial adhesion was carried out. In particular, a number of physicochemical factors important in defining the surface at the molecular level were assessed for their effect on the adhesion of
Listeria monocytogenes
,
Salmonella typhimurium
,
Staphylococcus aureus
, and
Escherichia coli
. The primary experiments involved the grafting of groups varying in hydrophilicity, hydrophobicity, chain length, and chemical functionality onto glass substrates such that the surfaces were homogeneous and densely packed with functional groups. All of the surfaces were found to be chemically well defined, and their measured surface energies varied from 15 to 41 mJ · m
−2
. Protein adsorption experiments were performed with
3
H-labelled bovine serum albumin and cytochrome
c
prior to bacterial attachment studies. Hydrophilic uncharged surfaces showed the greatest resistance to protein adsorption; however, our studies also showed that the effectiveness of poly(ethyleneoxide) (PEO) polymers was not simply a result of its hydrophilicity and molecular weight alone. The adsorption of the two proteins approximately correlated with short-term cell adhesion, and bacterial attachment for
L. monocytogenes
and
E. coli
also correlated with the chemistry of the underlying substrate. However, for
S. aureus
and
S. typhimurium
a different pattern of attachment occurred, suggesting a dissimilar mechanism of cell attachment, although high-molecular-weight PEO was still the least-cell-adsorbing surface. The implications of this for in vivo attachment of cells suggest that hydrophilic passivating groups may be the best method for preventing cell adsorption to synthetic substrates provided they can be grafted uniformly and in sufficient density at the surface.
Protein-Mediated Adhesion of the Dissimilatory Fe(III)-Reducing Bacterium
Shewanella alga
BrY to Hydrous Ferric Oxide
Authors: Caccavo Frank 
Published: December 2019

ABSTRACT

The rate and extent of bacterial Fe(III) mineral reduction are governed by molecular-scale interactions between the bacterial cell surface and the mineral surface. These interactions are poorly understood. This study examined the role of surface proteins in the adhesion of
Shewanella alga
BrY to hydrous ferric oxide (HFO). Enzymatic degradation of cell surface polysaccharides had no effect on cell adhesion to HFO. The proteolytic enzymes
Streptomyces griseus
protease and chymotrypsin inhibited the adhesion of
S. alga
BrY cells to HFO through catalytic degradation of surface proteins. Trypsin inhibited
S. alga
BrY adhesion solely through surface-coating effects. Protease and chymotrypsin also mediated desorption of adhered
S. alga
BrY cells from HFO while trypsin did not mediate cell desorption. Protease removed a single peptide band that represented a protein with an apparent molecular mass of 50 kDa. Chymotrypsin removed two peptide bands that represented proteins with apparent molecular masses of 60 and 31 kDa. These proteins represent putative HFO adhesion molecules.
S. alga
BrY adhesion was inhibited by up to 46% when cells were cultured at sub-MICs of chloramphenicol, suggesting that protein synthesis is necessary for adhesion. Proteins extracted from the surface of
S. alga
BrY cells inhibited adhesion to HFO by up to 41%. A number of these proteins bound specifically to HFO, suggesting that a complex system of surface proteins mediates
S. alga
BrY adhesion to HFO.
Adhesion of Biodegradative Anaerobic Bacteria to Solid Surfaces
Authors: van Schie Paula M. , Fletcher Madilyn 
Published: December 2019

ABSTRACT

In order to exploit the ability of anaerobic bacteria to degrade certain contaminants for bioremediation of polluted subsurface environments, we need to understand the mechanisms by which such bacteria partition between aqueous and solid phases, as well as the environmental conditions that influence partitioning. We studied four strictly anaerobic bacteria,
Desulfomonile tiedjei
,
Syntrophomonas wolfei
,
Syntrophobacter wolinii
, and
Desulfovibrio
sp. strain G11, which theoretically together can constitute a tetrachloroethylene- and trichloroethylene-dechlorinating consortium. Adhesion of these organisms was evaluated by microscopic determination of the numbers of cells that attached to glass coverslips exposed to cell suspensions under anaerobic conditions. We studied the effects of the growth phase of the organisms on adhesion, as well as the influence of electrostatic and hydrophobic properties of the substratum. Results indicate that
S. wolfei
adheres in considerably higher numbers to glass surfaces than the other three organisms. Starvation greatly decreases adhesion of
S. wolfei
and
Desulfovibrio
sp. strain G11 but seems to have less of an effect on the adhesion of the other bacteria. The presence of Fe
3+
on the substratum, which would be electropositive, significantly increased the adhesion of
S. wolfei
, whereas the presence of silicon hydrophobic groups decreased the numbers of attached cells of all species. Measurements of transport of cells through hydrophobic-interaction and electrostatic-interaction columns indicated that all four species had negatively charged cell surfaces and that
D. tiedjei
and
Desulfovibrio
sp. strain G11 possessed some hydrophobic cell surface properties. These findings are an early step toward understanding the dynamic attachment of anaerobic bacteria in anoxic environments.
Substrate Uptake by Uncultured Bacteria from the Genus
Achromatium
Determined by Microautoradiography
Authors: Gray N. D. , Howarth R. , Pickup R. W. , Jones J. Gwyn , Head I. M. 
Published: December 2019

ABSTRACT

Microautoradiography was used to investigate substrate uptake by natural communities of uncultured bacteria from the genus
Achromatium
. Studies of the uptake of
14
C-labelled substrates demonstrated that
Achromatium
cells from freshwater sediments were able to assimilate
14
C from bicarbonate, acetate, and protein hydrolysate; however,
14
C-labelled glucose was not assimilated. The pattern of substrate uptake by
Achromatium
spp. was therefore similar to those of a number of other freshwater and marine sulfur-oxidizing bacteria. Different patterns of radiolabelled bicarbonate uptake were noted for
Achromatium
communities from different geographical locations and indicated that one community (Rydal Water) possessed autotrophic potential, while the other (Hell Kettles) did not. Furthermore, the patterns of organic substrate uptake within a single population suggested that physiological diversity existed in natural communities of
Achromatium
. These observations are consistent with and may relate to the phylogenetic diversity observed in
Achromatium
communities. Incubation of
Achromatium
-bearing sediment cores from Rydal Water with
35
S-labelled sulfate in the presence and absence of sodium molybdate demonstrated that this bacterial population was capable of oxidizing sulfide to intracellular elemental sulfur. This finding supported the role of
Achromatium
in the oxidative component of a tightly coupled sulfur cycle in Rydal Water sediment. The oxidation of sulfide to sulfur and ultimately to sulfate by
Achromatium
cells from Rydal Water sediment is consistent with an ability to conserve energy from sulfide oxidation.
Thermicanus aegyptius
gen. nov., sp. nov., Isolated from Oxic Soil, a Fermentative Microaerophile That Grows Commensally with the Thermophilic Acetogen
Moorella thermoacetica
Authors: Gößner Anita S. , Devereux Richard , Ohnemüller Nadja , Acker Georg , Stackebrandt Erko , Drake Harold L. 
Published: December 2019

ABSTRACT

A thermophilic, fermentative microaerophile (ET-5b) and a thermophilic acetogen (ET-5a) were coisolated from oxic soil obtained from Egypt. The 16S rRNA gene sequence of ET-5a was 99.8% similar to that of the classic acetogen
Moorella thermoacetica
. Further analyses confirmed that ET-5a was a new strain of
M. thermoacetica
. For ET-5b, the nearest 16S rRNA gene sequence similarity value to known genera was approximately 88%. ET-5b was found to be a motile rod with a genomic G+C content of 50.3 mol%. Cells were weakly gram positive and lacked spores. Growth was optimal at 55 to 60°C and pH 6.5 to 7.0. ET-5b grew under both oxic and anoxic conditions, but growth was erratic under atmospheric concentrations of O
2
. Utilizable substrates included oligosaccharides and monosaccharides. Acetate, formate, and succinate supported growth only under oxic conditions. Saccharides yielded succinate, lactate, ethanol, acetate, formate, and H
2
under anoxic conditions; fermentation products were also formed under oxic conditions. A new genus is proposed, the type strain being
Thermicanus aegyptius
ET-5b gen. nov., sp. nov. (DSMZ 12793).
M. thermoacetica
ET-5a (DSMZ 12797) grew commensally with
T. aegyptius
ET-5b on oligosaccharides via the interspecies transfer of H
2
formate, and lactate. In support of this interaction, uptake hydrogenase and formate dehydrogenase specific activities were fundamentally greater in
M. thermoacetica
ET-5a than in
T. aegyptius
ET-5b. These results demonstrate that (i) soils subject to high temperatures harbor uncharacterized thermophilic microaerophiles, (ii) the classic acetogen
M. thermoacetica
resides in such soils, and (iii) trophic links between such soil bacteria might contribute to their in situ activities.
Display of Polyhistidine Peptides on the
Escherichia coli
Cell Surface by Using Outer Membrane Protein C as an Anchoring Motif
Authors: Xu Zhaohui , Lee Sang Yup 
Published: December 2019

ABSTRACT

A novel cell surface display system was developed by employing
Escherichia coli
outer membrane protein C (OmpC) as an anchoring motif. Polyhistidine peptides consisting of up to 162 amino acids could be successfully displayed on the seventh exposed loop of OmpC. Recombinant cells displaying polyhistidine could adsorb up to 32.0 μmol of Cd
2+
per g (dry weight) of cells.