bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Low Temperatures on Growth, Structure, and Metabolism of
Campylobacter coli
SP10
Authors: Höller Christiane , Witthuhn Doris , Janzen-Blunck Birgit 
Published: December 2019

ABSTRACT

The effect of low temperatures on the survival, structure, and metabolism of
Campylobacter coli
SP10, a virulent strain, was investigated.
C. coli
became nonculturable rapidly at 20 and 10°C and slightly later at 4°C. Incubation in a microaerobic atmosphere improved survival, but after day 8, campylobacters were detectable by direct-count procedures only. The increase in the number of coccoid cells was most pronounced at 37°C but also was noticeable at 20 and 10°C. Two forms of coccoid cells were seen electron microscopically, but only one (20 and 10°C) seemed to be a degenerative form. The flagella were shorter at 20 and 10°C, a result which correlates well with the observed slight changes in the 62-kDa protein band. The fatty acid composition of bacterial cells was influenced significantly by low temperatures. An increase in the short-chain and unsaturated acids was noted; above all, a drastic increase in C
19:0
cyc at 20°C with a concomitant decrease in C
18:1
trans9,cis11 was seen. The concentrations of excreted metabolites were analyzed to obtain information on metabolic activity. Depending on the magnitude of the temperature downshift, the production of organic acids decreased, but it was always observable after a temperature-specific lag phase and regardless of ability to be cultured. Under optimal conditions, succinate, lactate, and acetate were the main metabolites, other acids being of less importance. The pattern changed significantly at lower temperatures. Succinate was never detected at 20°C and was only occasionally detected at 10 and 4°C. At the same time, fumarate concentrations, which are normally not detectable at 37°C, were highest at 20°C and reduced at 10 and 4°C. Inactivation of fumarate reductase was considered to be a possible explanation.
Endophytic Fungi in Indigenous Australasian Grasses Associated with Toxicity to Livestock
Authors: Miles Christopher O. , di Menna Margaret E. , Jacobs Surrey W. L. , Garthwaite Ian , Lane Geoffrey A. , Prestidge Ron A. , Marshall Sergio L. , Wilkinson Heather H. , Schardl Christopher L. , Ball Olivier J.-P. , Latch Garrick C. M. 
Published: December 2019

ABSTRACTGrazing ofEchinopogonspp. by livestock in Australia has caused symptoms similar to those of perennial ryegrass staggers. We observed an endophytic fungus in the intercellular spaces of the leaves and seeds of New Zealand and Australian specimens ofEchinopogon ovatus. Culture of surface-sterilized seeds from New Zealand specimens yielded a slow-growing fungus. An examination in which immunoblotting and an enzyme-linked immunosorbent assay (ELISA) were used indicated thatE. ovatusplants from Australia and New Zealand were infected with fungi serologically related toNeotyphodium lolii(the endophyte of perennial ryegrass) and otherEpichloeandNeotyphodiumspp. endophytic in pooid grasses. No lolitrems (the indole–diterpenoids implicated as the causative agents of perennial ryegrass staggers), peramine analogs, or ergot alkaloids were detected in the infected specimens by high-performance liquid chromatography or ELISA. However, in endophyte-infectedE. ovatusplants from New Zealand, analogs of the indole–diterpenoid paxilline (thought to be a biosynthetic precursor of the lolitrems and related tremorgens) were detected by ELISA, andN-formylloline was detected by gas chromatography. Endophyte-free specimens of New ZealandE. ovatusdid not contain detectable paxilline analogs or lolines and were more palatable than infected specimens to adults of the pasture pestListronotus bonariensis(Argentine stem weevil). Hyphae similar to those of theE. ovatusendophyte were also found in herbarium specimens ofEchinopogon nutansvar.major,Echinopogon intermedius,Echinopogon caespitosus, andEchinopogon cheeli. This appears to be the first time that an endophyticNeotyphodiumspecies has been identified in grasses endemic to New Zealand or Australia.
Identification of Hydrocarbon-Degrading Bacteria in Soil by Reverse Sample Genome Probing
Authors: Shen Yin , Stehmeier Lester G. , Voordouw Gerrit 
Published: December 2019

ABSTRACT

Bacteria with limited genomic cross-hybridization were isolated from soil contaminated with C5+, a mixture of hydrocarbons, and identified by partial 16S rRNA sequencing. Filters containing denatured genomic DNAs were used in a reverse sample genome probe (RSGP) procedure for analysis of the effect of an easily degradable compound (toluene) and a highly recalcitrant compound (dicyclopentadiene [DCPD]) on community composition. Hybridization with labeled total-community DNA isolated from soil exposed to toluene indicated enrichment of several
Pseudomonas
spp., which were subsequently found to be capable of toluene mineralization. Hybridization with labeled total-community DNA isolated from soil exposed to DCPD indicated enrichment of a
Pseudomonas
sp. or a
Sphingomonas
sp. These two bacteria appeared capable of producing oxygenated DCPD derivatives in the soil environment, but mineralization could not be shown. These results demonstrate that bacteria, which metabolize degradable or recalcitrant hydrocarbons, can be identified by the RSGP procedure.
Determination of Bacterial Cell Dry Mass by Transmission Electron Microscopy and Densitometric Image Analysis
Authors: Loferer-Krößbacher M. , Klima J. , Psenner R. 
Published: December 2019

ABSTRACT

We applied transmission electron microscopy and densitometric image analysis to measure the cell volume (
V
) and dry weight (DW) of single bacterial cells. The system was applied to measure the DW of
Escherichia coli
DSM 613 at different growth phases and of natural bacterial assemblages of two lakes, Piburger See and Gossenköllesee. We found a functional allometric relationship between DW (in femtograms) and
V
(in cubic micrometers) of bacteria (DW = 435 ·
V
0.86
); i.e., smaller bacteria had a higher ratio of DW to
V
than larger cells. The measured DW of
E. coli
cells ranged from 83 to 1,172 fg, and
V
ranged from 0.1 to 3.5 μm
3
(
n
= 678). Bacterial cells from Piburger See and Gossenköllesee (
n
= 465) had DWs from 3 fg (
V
= 0.003 μm
3
) to 1,177 fg (
V
= 3.5 μm
3
). Between 40 and 50% of the cells had a DW of less than 20 fg. By assuming that carbon comprises 50% of the DW, the ratio of carbon content to
V
of individual cells varied from 466 fg of C μm
−3
for
V
s of 0.001 to 0.01 μm
3
to 397 fg of C μm
−3
(0.01 to 0.1 μm
3
) and 288 fg of C μm
−3
(0.1 to 1 μm
3
). Exponentially growing and stationary cells of
E. coli
DSM 613 showed conversion factors of 254 fg of C μm
−3
(0.1 to 1 μm
3
) and 211 fg of C μm
−3
(1 to 4 μm
3
), respectively. Our data suggest that bacterial biomass in aquatic environments is higher and more variable than previously assumed from volume-based measurements.
Oxygen Consumption byDesulfovibrioStrains with and without Polyglucose
Authors: van Niel Ed W. J. , Gottschal Jan C. 
Published: December 2019

ABSTRACTThe kinetics of oxygen reduction byDesulfovibrio salexigensMast1 and the role of polyglucose in this activity were examined and compared with those of strains ofD. desulfuricansandD. gigas. Oxidation rates were highest at air saturation (up to 40 nmol of O2min−1mg of protein−1) and declined with decreasing oxygen concentrations. Studies with cell extracts (CE) indicated that NADH oxidase was entirely responsible for the oxygen reduction in strain Mast1. InD. desulfuricansCSN, at least three independent systems appeared to reduce oxygen. Two were active at all oxygen concentrations (NADH oxidase and NADPH oxidase), and one was maximally active at less than 10 μM oxygen. In contrast toD. gigasandD. salexigensstrains, theD. desulfuricansstrains also contained NADH peroxidase and NADPH peroxidase activities and did not accumulate polyglucose under nonlimiting growth conditions. At air saturation, initial activities of the oxidases and peroxidases of cells harvested at the end of the log phase were on the order of 20 to 140 nmol of O2min−1mg of protein−1. In all strains, these enzymes were relatively stable but were susceptible to inactivation as soon as substrates were added to the assay mixture. Under those conditions, all oxidation activity disappeared after ca. 1 h of incubation. The same finding was observed with whole cells ofD. desulfuricansCSN andD. desulfuricansATCC 27774, but inactivation was less pronounced with cells ofD. salexigensMast1. It appeared that the presence of polyglucose in the whole cells retarded the process of inactivation of NADH oxidase, but this property was lost in crude CE. In spite of the effect of polyglucose on the oxidative potential, oxygen-dependent growth ofD. salexigensMast1 could be demonstrated neither in batch nor in continuous culture.
Dibiphytanyl Ether Lipids in Nonthermophilic Crenarchaeotes
Authors: DeLong Edward F. , King Linda L. , Massana Ramon , Cittone Henry , Murray Alison , Schleper Christa , Wakeham Stuart G. 
Published: December 2019

ABSTRACT

The kingdom
Crenarchaeota
is now known to include archaea which inhabit a wide variety of low-temperature environments. We report here lipid analyses of nonthermophilic crenarchaeotes, which revealed the presence of cyclic and acyclic dibiphytanylglycerol tetraether lipids. Nonthermophilic crenarchaeotes appear to be a major biological source of tetraether lipids in marine planktonic environments.
Hydrostatic Pressure Enhances Vital Staining with Carboxyfluorescein or Carboxydichlorofluorescein in
Saccharomyces cerevisiae
: Efficient Detection of Labeled Yeasts by Flow Cytometry
Authors: Abe Fumiyoshi 
Published: December 2019

ABSTRACT

The extent of intracellular accumulation of the fluorescent dye carboxyfluorescein or carboxydichlorofluorescein (CDCF) in
Saccharomyces cerevisiae
was found to be increased 5- to 10-fold under a nonlethal hydrostatic pressure of 30 to 50 MPa. This observation was confirmed by analysis of individual labeled cells by flow cytometry. The pressure-induced enhancement of staining with CDCF required
d
-glucose and was markedly inhibited by 2-deoxy-
d
-glucose, suggesting that glucose metabolism has a role in the process.
Engineering of Plasmin-Resistant Forms of Streptokinase and Their Production in
Bacillus subtilis
: Streptokinase with Longer Functional Half-Life
Authors: Wu Xu-Chu , Ye Ruiqiong , Duan Yanjun , Wong Sui-Lam 
Published: December 2019

ABSTRACT

The short in vivo half-life of streptokinase limits its efficacy as an efficient blood clot-dissolving agent. During the clot-dissolving process, streptokinase is processed to smaller intermediates by plasmin. Two of the major processing sites are Lys59 and Lys386. We engineered two versions of streptokinase with either one of the lysine residues changed to glutamine and a third version with both mutations. These mutant streptokinase proteins (muteins) were produced by secretion with the protease-deficient
Bacillus subtilis
WB600 as the host. The purified muteins retained comparable kinetics parameters in plasminogen activation and showed different degrees of resistance to plasmin depending on the nature of the mutation. Muteins with double mutations had half-lives that were extended 21-fold when assayed in a 1:1 molar ratio with plasminogen in vitro and showed better plasminogen activation activity with time in the radial caseinolysis assay. This study indicates that plasmin-mediated processing leads to the inactivation of streptokinase and is not required to convert streptokinase to its active form. Plasmin-resistant forms of streptokinase can be engineered without affecting their activity, and blockage of the N-terminal cleavage site is essential to generate engineered streptokinase with a longer in vitro functional half-life.
Regulation of the
Aspergillus nidulans
Penicillin Biosynthesis Gene
acvA
(
pcbAB
) by Amino Acids: Implication for Involvement of Transcription Factor PACC
Authors: Bergh Katharina Then , Brakhage Axel A. 
Published: December 2019

ABSTRACT

The β-lactam antibiotic penicillin is produced as an end product by some filamentous fungi only. It is synthesized from the amino acid precursors
l
-α-aminoadipic acid,
l
-cysteine, and
l
-valine. Previous data suggested that certain amino acids play a role in the regulation of its biosynthesis. Therefore, in this study the effects of externally added amino acids on both
Aspergillus
(
Emericella
)
nidulans
penicillin production and expression of the bidirectionally oriented biosynthesis genes
acvA
(
pcbAB
) and
ipnA
(
pcbC
) were comprehensively investigated. Different effects caused by amino acids on the expression of penicillin biosynthesis genes and penicillin production were observed. Amino acids with a major negative effect on the expression of
acvA-uidA
and
ipnA-lacZ
gene fusions, i.e., histidine, valine, lysine, and methionine, led to a decreased ambient pH during cultivation of the fungus. An analysis of deletion clones lacking binding sites for the pH-dependent transcriptional factor PACC in the intergenic regions between
acvA-uidA
and
ipnA-lacZ
gene fusions and in a
pacC5
mutant (PacC5-5) suggested that the negative effects of histidine and valine on
acvA-uidA
expression were due to reduced activation by PACC under acidic conditions. These data also implied that PACC regulates the expression of
acvA
, predominantly through PACC binding site ipnA3. The repressing effect caused by lysine and methionine on
acvA
expression, however, was even enhanced in one of the deletion clones and the
pacC5
mutant strain, suggesting that regulators other than PACC are also involved.
Use of an Oxygen-Insensitive Microscale Biosensor for Methane To Measure Methane Concentration Profiles in a Rice Paddy
Authors: Damgaard Lars R. , Revsbech Niels Peter , Reichardt Wolfgang 
Published: December 2019

ABSTRACT
An oxygen-insensitive microscale biosensor for methane was constructed by furnishing a previously described biosensor with an oxygen guard. The guard consisted of a glass capillary containing heterotrophic bacteria, which consumed oxygen diffusing through the tip membrane, thus preventing it from diffusing into the methane-sensing unit. Oxygen microprofiles were measured through the oxygen guard capillary, demonstrating the principle and limitations of the method. When the tip of the guard capillary was exposed to 100% oxygen at 21°C, heterotrophic oxygen consumption prevented oxygen from diffusing further than 170 μm into the capillary, whereas atmospheric levels of oxygen were consumed within 50 μm. The capacity of the oxygen guard for scavenging oxygen decreased with decreasing temperature, and atmospheric levels of oxygen caused oxygen penetration to 200 μm at 5°C. The sensors could be manufactured with tip diameters as small as 25 μm, and response times were about 1 min at room temperature. Pore water profiles of methane concentrations in a rice paddy soil were measured, and a strong correlation between the depths of oxygen penetration and methane appearance was observed as a function of the light regimen; this finding confirmed the role of microbenthic photosynthesis in limiting methane emissions from surfaces of waterlogged sediments and soils.
PCR Amplification of Ribosomal DNA for Species Identification in the Plant Pathogen Genus
Phytophthora
Authors: Ristaino Jean B. , Madritch Michael , Trout Carol L. , Parra Gregory 
Published: December 2019

ABSTRACT

We have developed a PCR procedure to amplify DNA for quick identification of the economically important species from each of the six taxonomic groups in the plant pathogen genus
Phytophthora
. This procedure involves amplification of the 5.8S ribosomal DNA gene and internal transcribed spacers (ITS) with the ITS primers ITS 5 and ITS 4. Restriction digests of the amplified DNA products were conducted with the restriction enzymes
Rsa
I,
Msp
I, and
Hae
III. Restriction fragment patterns were similar after digestions with
Rsa
I for the following species:
P. capsici
and
P. citricola
;
P. infestans
,
P. cactorum
, and
P. mirabilis
;
P. fragariae
,
P. cinnamomi
, and
P. megasperma
from peach;
P. palmivora
,
P. citrophthora
,
P. erythroseptica
, and
P. cryptogea
; and
P. megasperma
from raspberry and
P. sojae
. Restriction digests with
Msp
I separated
P. capsici
from
P. citricola
and separated
P. cactorum
from
P. infestans
and
P. mirabilis
. Restriction digests with
Hae
III separated
P. citrophthora
from
P. cryptogea
,
P. cinnamomi
from
P. fragariae
and
P. megasperma
on peach,
P. palmivora
from
P. citrophthora
, and
P. megasperma
on raspberry from
P. sojae. P. infestans
and
P. mirabilis
digests were identical and
P. cryptogea
and
P. erythroseptica
digests were identical with all restriction enzymes tested. A unique DNA sequence from the ITS region I in
P. capsici
was used to develop a primer called PCAP. The PCAP primer was used in PCRs with ITS 1 and amplified only isolates of
P. capsici
,
P. citricola
, and
P. citrophthora
and not 13 other species in the genus. Restriction digests with
Msp
I separated
P. capsici
from the other two species. PCR was superior to traditional isolation methods for detection of
P. capsici
in infected bell pepper tissue in field samples. The techniques described will provide a powerful tool for identification of the major species in the genus
Phytophthora.
Pyruvate Decarboxylase Catalyzes Decarboxylation of Branched-Chain 2-Oxo Acids but Is Not Essential for Fusel Alcohol Production by
Saccharomyces cerevisiae
Authors: ter Schure Eelko G. , Flikweert Marcel T. , van Dijken Johannes P. , Pronk Jack T. , Verrips C. Theo 
Published: December 2019

ABSTRACT

The fusel alcohols 3-methyl-1-butanol, 2-methyl-1-butanol, and 2-methyl-propanol are important flavor compounds in yeast-derived food products and beverages. The formation of these compounds from branched-chain amino acids is generally assumed to occur via the Ehrlich pathway, which involves the concerted action of a branched-chain transaminase, a decarboxylase, and an alcohol dehydrogenase. Partially purified preparations of pyruvate decarboxylase (EC
4.1.1.1
) have been reported to catalyze the decarboxylation of the branched-chain 2-oxo acids formed upon transamination of leucine, isoleucine, and valine. Indeed, in a coupled enzymatic assay with horse liver alcohol dehydrogenase, cell extracts of a wild-type
Saccharomyces cerevisiae
strain exhibited significant decarboxylation rates with these branched-chain 2-oxo acids. Decarboxylation of branched-chain 2-oxo acids was not detectable in cell extracts of an isogenic strain in which all three
PDC
genes had been disrupted. Experiments with cell extracts from
S. cerevisiae
mutants expressing a single
PDC
gene demonstrated that both
PDC1
- and
PDC5
-encoded isoenzymes can decarboxylate branched-chain 2-oxo acids. To investigate whether pyruvate decarboxylase is essential for fusel alcohol production by whole cells, wild-type
S. cerevisiae
and an isogenic pyruvate decarboxylase-negative strain were grown on ethanol with a mixture of leucine, isoleucine, and valine as the nitrogen source. Surprisingly, the three corresponding fusel alcohols were produced in both strains. This result proves that decarboxylation of branched-chain 2-oxo acids via pyruvate decarboxylase is not an essential step in fusel alcohol production.
The
Desulfuromonas acetoxidans
Triheme Cytochrome
c
7
Produced in
Desulfovibrio desulfuricans
Retains Its Metal Reductase Activity
Authors: Aubert Corinne , Lojou Elisabeth , Bianco Pierre , Rousset Marc , Durand Marie-Claire , Bruschi Mireille , Dolla Alain 
Published: December 2019

ABSTRACT

Multiheme cytochrome
c
proteins that belong to class III have been recently shown to exhibit a metal reductase activity, which could be of great environmental interest, especially in metal bioremediation. To get a better understanding of these activities, the gene encoding cytochrome
c
7
from the sulfur-reducing bacterium
Desulfuromonas acetoxidans
was cloned from genomic DNA by PCR and expressed in
Desulfovibrio desulfuricans
G201. The expression system was based on the
cyc
transcription unit from
Desulfovibrio vulgaris
Hildenborough and led to the synthesis of holocytochrome
c
7
when transferred by electrotransformation into the sulfate reducer
Desulfovibrio desulfuricans
G201. The produced cytochrome was indistinguishable from the protein purified from
Desulfuromonas acetoxidans
cells with respect to several biochemical and biophysical criteria and exhibited the same metal reductase activities as determined from electrochemical experiments. This suggests that the molecule was correctly folded in the host organism.
Desulfovibrio desulfuricans
produces functional multiheme
c
-type cytochromes from bacteria belonging to a different genus and may be considered a suitable host for the heterologous biogenesis of multiheme
c
-type cytochromes for either structural or engineering studies. This report, which presents the first example of the transformation of a
Desulfovibrio desulfuricans
strain by electrotransformation, describes work that is the first necessary step of a protein engineering program that aims to specify the structural features that are responsible for the metal reductase activities of multiheme cytochrome
c
7
.
A Competitive Microflora Increases the Resistance of
Salmonella typhimurium
to Inimical Processes: Evidence for a Suicide Response
Authors: Aldsworth Timothy G. , Sharman Rachel L. , Dodd Christine E. R. , Stewart Gordon S. A. B. 
Published: December 2019

ABSTRACT

The presence of a viable competitive microflora at cell densities of 10
8
CFU ml
−1
protects an underlying population of 10
5
CFU of
Salmonella typhimurium
ml
−1
against freeze injury. The mechanism of enhanced resistance was initially postulated to be via an RpoS-mediated adaptive response. By using an
spvRA::luxCDABE
reporter we have shown that although the onset of RpoS-mediated gene expression was brought forward by the addition of a competitive microflora, the time taken for induction was measured in hours. Since the protective effect of a competitive microflora is essentially instantaneous, the stationary-phase adaptive response is excluded as the physiological mechanism. The only instantaneous effect of the competitive microflora was a reduction in the percent saturation of oxygen from 100% to less than 10%. For both mild heat treatment (55°C) and freeze injury this change in oxygen tension affords
Salmonella
a substantive (2 orders of magnitude) enhancement in survival. By reducing the levels of dissolved oxygen through active respiration, a competitive microflora reduces oxidative damage to exponential-phase cells irrespective of the inimical treatment. These results have led us to propose a suicide hypothesis for the destruction of rapidly growing cells by inimical processes. In essence, the suicide hypothesis proposes that a mild inimical process leads to the growth arrest of exponential-phase cells and to the decoupling of anabolic and catabolic metabolism. The result of this is a free radical burst which is lethal to unadapted cells.