bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tn
5
-Induced and Spontaneous Switching of
Sinorhizobium meliloti
to Faster-Swarming Behavior
Authors: Wei Xueming , Bauer Wolfgang D. 
Published: December 2019

ABSTRACT

Tn
5
mutants of
Sinorhizobium meliloti
RMB7201 which swarmed 1.5 to 2.5 times faster than the parental strain in semisolid agar, moist sand, and viscous liquid were identified. These faster-swarming (FS) mutants outgrew the wild type 30- to 40-fold within 2 days in mixed swarm colonies. The FS mutants survived and grew as well as or better than the wild type under all of the circumstances tested, except in a soil matrix subjected to air drying. Exopolysaccharide (EPS) synthesis was reduced in each of the FS mutants when they were grown on defined succinate-nitrate medium, but the extent of reduction was different for each. It appears that FS behavior likely results from a modest, general derepression of motility involving an increased proportion of motile and flagellated cells and an increased average number of flagella per cell and increased average flagellar length. Spontaneous FS variants of RMB7201 were obtained at a frequency of about 1 per 10,000 to 20,000 cells by either enrichment from the periphery of swarm colonies or screening of colonies for reduced EPS synthesis on succinate-nitrate plates. The spontaneous FS variants and Tn
5
FS mutants were symbiotically effective and competitive in alfalfa nodulation. Reversion of FS variants to wild-type behavior was sporadic, indicating that reversion is affected by unidentified environmental factors. Based on phenotypic and molecular differences between individual FS variants and mutants, it appears that there may be multiple genetic configurations that result in FS behavior in RMB7201. The facile isolation of spontaneous FS variants of
Escherichia coli
and
Pseudomonas aeruginosa
indicates that switching to FS behavior may be fairly common among bacterial species. The substantial growth advantage of FS mutants and variants wherever nutrient gradients exist suggests that switching to FS forms may be an important behavioral adaptation in natural environments.
Pulsed-Light Inactivation of Food-Related Microorganisms
Authors: Rowan N. J. , MacGregor S. J. , Anderson J. G. , Fouracre R. A. , McIlvaney L. , Farish O. 
Published: December 2019

ABSTRACT

The effects of high-intensity pulsed-light emissions of high or low UV content on the survival of predetermined populations of
Listeria monocytogenes
,
Escherichia coli
,
Salmonella enteritidis
,
Pseudomonas aeruginosa
,
Bacillus cereus
, and
Staphylococcus aureus
were investigated. Bacterial cultures were seeded separately on the surface of tryptone soya-yeast extract agar and were reduced by up to 2 or 6 log
10
orders with 200 light pulses (pulse duration, ∼100 ns) of low or high UV content, respectively (
P
< 0.001).
Isolation ofVibrio vulnificusSerovar E from Aquatic Habitats in Taiwan
Authors: Amaro Carmen , Hor Lien-I , Marco-Noales Ester , Bosque Teresa , Fouz Belén , Alcaide Elena 
Published: December 2019

ABSTRACTThe existence of strains ofVibrio vulnificusserovar E that are avirulent for eels is reported in this work. These isolates were recovered from water and oysters and differed from eel virulent strains in (i) fermentation and utilization of mannitol, (ii) ribotyping afterHindIII digestion, and (iii) susceptibility to eel serum. Lipopolysaccharide of these strains lacked the highest molecular weight immunoreactive bands, which are probably involved in serum resistance.
Electron Microscopy Studies of Cell-Wall-Anchored Cellulose (Avicel)-Binding Protein (AbpS) from
Streptomyces reticuli
Authors: Walter Stefan , Rohde Manfred , Machner Matthias , Schrempf Hildgund 
Published: December 2019

ABSTRACT

Streptomyces reticuli
produces a 35-kDa cellulose (Avicel)-binding protein (AbpS) which interacts strongly with crystalline cellulose but not with soluble types of cellulose. Antibodies that were highly specific for the NH
2
-terminal part of AbpS were isolated by using truncated AbpS proteins that differed in the length of the NH
2
terminus. Using these antibodies for immunolabelling and investigations in which fluorescence, transmission electron, or immunofield scanning electron microscopy was used showed that the NH
2
terminus of AbpS protrudes from the murein layer of
S. reticuli
. Additionally, inspection of ultrathin sections of the cell wall, as well as biochemical experiments performed with isolated murein, revealed that AbpS is tightly and very likely covalently linked to the polyglucane layer. As AbpS has also been found to be associated with protoplasts, we predicted that a COOH-terminal stretch consisting of 17 hydrophobic amino acids anchors the protein to the membrane. Different amounts of AbpS homologues of several
Streptomyces
strains were synthesized.
The Nuclear Ribosomal DNA Intergenic Spacer as a Target Sequence To Study Intraspecific Diversity of the Ectomycorrhizal BasidiomyceteHebeloma cylindrosporumDirectly onPinusRoot Systems
Authors: Guidot Alice , Lumini Erica , Debaud Jean-Claude , Marmeisse Roland 
Published: December 2019

ABSTRACTPolymorphism of the nuclear ribosomal DNA intergenic spacer (IGS) of the ectomycorrhizal basidiomyceteHebeloma cylindrosporumwas studied to evaluate whether this sequence could be used in field studies to estimate the diversity of strains forming mycorrhizas on individualPinus pinasterroot systems. This sequence was amplified by PCR from 125 haploid homokaryotic strains collected in 14P. pinasterstands along the Atlantic coast of France by using conserved oligonucleotide primers. Restriction enzyme digestion of the amplified 3.4-kbp-long IGS allowed us to characterize 24 alleles whose frequencies differed. Nine of these alleles were found only once, whereas about 60% of the strains contained four of the alleles. Local populations could be almost as diverse as the entire population along a 150-km stretch of coastline that was examined; for example, 13 alleles were found in a single forest stand. The IGS from one strain was partially sequenced, and the sequence data were used to design oligonucleotides which allowed separate PCR amplification of three different segments of the IGS. Most polymorphisms observed among the full-length IGS regions resulted from polymorphisms in an internal ca. 1,500-bp-long sequence characterized by length variations that may have resulted from variable numbers of a T2AG3motif. This internal polymorphic sequence could not be amplified from the genomes of nine otherHebelomaspecies. Analysis of this internal sequence amplified from the haploid progenies of 10 fruiting bodies collected in a 70-m2area resulted in identification of six allelic forms and seven distinct diplotypes out of the 21 possible different combinations. Moreover, optimization of the PCR conditions resulted in amplification of this sequence from more than 80% of the DNA samples extracted from individualH. cylindrosporuminfectedP. pinastermycorrhizal root tips, thus demonstrating the usefulness of this sequence for studying the below-ground diversity of mycorrhizas formed by genets belonging to the same fungal species.
Inhibition of
Vibrio anguillarum
by
Pseudomonas fluorescens
AH2, a Possible Probiotic Treatment of Fish
Authors: Gram Lone , Melchiorsen Jette , Spanggaard Bettina , Huber Ingrid , Nielsen Torben F. 
Published: December 2019

ABSTRACT

To study the possible use of probiotics in fish farming, we evaluated the in vitro and in vivo antagonism of antibacterial strain
Pseudomonas fluorescens
strain AH2 against the fish-pathogenic bacterium
Vibrio anguillarum
. As iron is important in virulence and bacterial interactions, the effect of
P. fluorescens
AH2 was studied under iron-rich and iron-limited conditions. Sterile-filtered culture supernatants from iron-limited
P. fluorescens
AH2 inhibited the growth of
V. anguillarum
, whereas sterile-filtered supernatants from iron-replete cultures of
P. fluorescens
AH2 did not.
P. fluorescens
AH2 inhibited the growth of
V. anguillarum
during coculture, independently of the iron concentration, when the initial count of the antagonist was 100 to 1,000 times greater that of the fish pathogen. These in vitro results were successfully repeated in vivo. A probiotic effect in vivo was tested by exposing rainbow trout (
Oncorynchus mykiss
Walbaum) to
P. fluorescens
AH2 at a density of 10
5
CFU/ml for 5 days before a challenge with
V. anguillarum
at 10
4
to 10
5
CFU/ml for 1 h. Some fish were also exposed to
P. fluorescens
AH2 at 10
7
CFU/ml during the 1-h infection. The combined probiotic treatment resulted in a 46% reduction of calculated accumulated mortality; accumulated mortality was 25% after 7 days at 12°C in the probiotic-treated fish, whereas mortality was 47% in fish not treated with the probiont.
A Cold-Active Glucanase from the Ruminal Bacterium
Fibrobacter succinogenes
S85
Authors: Iyo Abiye H. , Forsberg Cecil W. 
Published: December 2019

ABSTRACT

We previously characterized two endoglucanases, CelG and EGD, from the mesophilic ruminal anaerobe
Fibrobacter succinogenes
S85. Further comparative experiments have shown that CelG is a cold-active enzyme whose catalytic properties are superior to those of several other intensively studied cold-active enzymes. It has a lower temperature optimum, of 25°C, and retains about 70% of its maximum activity at 0°C, while EGD has a temperature optimum of 35°C and retains only about 18% of its maximal activity at 0°C. When assayed at 4°C, CelG exhibits a 33-fold-higher k
cat
value and a 73-fold-higher physiological efficiency (k
cat
/

K
m

) than EGD. CelG has a low thermal stability, as indicated by the effect of temperature on its activity and secondary structure. The presence of small amino acids around the putative catalytic residues may add to the flexibility of the enzyme, thereby increasing its activity at cold temperatures. Its activity is modulated by sodium chloride, with an increase of over 1.8-fold at an ionic strength of 0.03. Possible explanations for the presence of a cold-active enzyme in a mesophile are that cold-active enzymes are more broadly distributed than previously expected, that lateral transfer of the gene from a psychrophile occurred, or that
F. succinogenes
originated from the marine environment.
Geographic Distribution and Genetic Diversity of
Ceanothus
-Infective
Frankia
Strains
Authors: Ritchie Nancy J. , Myrold David D. 
Published: December 2019

ABSTRACT

Little is known about
Ceanothus
-infective
Frankia
strains because no
Frankia
strains that can reinfect the host plants have been isolated from
Ceonothus
spp. Therefore, we studied the diversity of the
Ceonothus
-infective
Frankia
strains by using molecular techniques.
Frankia
strains inhabiting root nodules of nine
Ceanothus
species were characterized. The
Ceanothus
species used represent the taxonomic diversity and geographic range of the genus; therefore, the breadth of the diversity of
Frankia
strains that infect
Ceanothus
spp. was studied. DNA was amplified directly from nodular material by using the PCR. The amplified region included the 3′ end of the 16S rRNA gene, the intergenic spacer, and a large portion of the 23S rRNA gene. A series of restriction enzyme digestions of the PCR product allowed us to identify PCR-restriction fragment length polymorphism (RFLP) groups among the
Ceanothus
-infective
Frankia
strains tested. Twelve different enzymes were used, which resulted in four different PCR-RFLP groups. The groups did not follow the taxonomic lines of the
Ceanothus
host species. Instead, the
Frankia
strains present were related to the sample collection locales.
Integrative Model for Binding of
Bacillus thuringiensis
Toxins in Susceptible and Resistant Larvae of the Diamondback Moth (
Plutella xylostella
)
Authors: Ballester Victoria , Granero Francisco , Tabashnik Bruce E. , Malvar Thomas , Ferré Juan 
Published: December 2019

ABSTRACT

Insecticidal crystal proteins from
Bacillus thuringiensis
in sprays and transgenic crops are extremely useful for environmentally sound pest management, but their long-term efficacy is threatened by evolution of resistance by target pests. The diamondback moth (
Plutella xylostella
) is the first insect to evolve resistance to
B. thuringiensis
in open-field populations. The only known mechanism of resistance to
B. thuringiensis
in the diamondback moth is reduced binding of toxin to midgut binding sites. In the present work we analyzed competitive binding of
B. thuringiensis
toxins Cry1Aa, Cry1Ab, Cry1Ac, and Cry1F to brush border membrane vesicles from larval midguts in a susceptible strain and in resistant strains from the Philippines, Hawaii, and Pennsylvania. Based on the results, we propose a model for binding of
B. thuringiensis
crystal proteins in susceptible larvae with two binding sites for Cry1Aa, one of which is shared with Cry1Ab, Cry1Ac, and Cry1F. Our results show that the common binding site is altered in each of the three resistant strains. In the strain from the Philippines, the alteration reduced binding of Cry1Ab but did not affect binding of the other crystal proteins. In the resistant strains from Hawaii and Pennsylvania, the alteration affected binding of Cry1Aa, Cry1Ab, Cry1Ac, and Cry1F. Previously reported evidence that a single mutation can confer resistance to Cry1Ab, Cry1Ac, and Cry1F corresponds to expectations based on the binding model. However, the following two other observations do not: the mutation in the Philippines strain affected binding of only Cry1Ab, and one mutation was sufficient for resistance to Cry1Aa. The imperfect correspondence between the model and observations suggests that reduced binding is not the only mechanism of resistance in the diamondback moth and that some, but not all, patterns of resistance and cross-resistance can be predicted correctly from the results of competitive binding analyses of susceptible strains.
Isolation and Characterization of Alfalfa-Nodulating Rhizobia Present in Acidic Soils of Central Argentina and Uruguay
Authors: del Papa María F. , Balagué Laura J. , Sowinski Susana Castro , Wegener Caren , Segundo Eduardo , Abarca Francisco Martínez , Toro Nicolás , Niehaus Karsten , Pühler Alfred , Aguilar O. Mario , Martínez-Drets Gloria , Lagares Antonio 
Published: December 2019

ABSTRACT

We describe the isolation and characterization of alfalfa-nodulating rhizobia from acid soils of different locations in Central Argentina and Uruguay. A collection of 465 isolates was assembled, and the rhizobia were characterized for acid tolerance. Growth tests revealed the existence of 15 acid-tolerant (AT) isolates which were able to grow at pH 5.0 and formed nodules in alfalfa with a low rate of nitrogen fixation. Analysis of those isolates, including partial sequencing of the genes encoding 16S rRNA and genomic PCR-fingerprinting with MBOREP1 and BOXC1 primers, demonstrated that the new isolates share a genetic background closely related to that of the previously reported
Rhizobium
sp. Or191 recovered from an acid soil in Oregon (B. D. Eardly, J. P. Young, and R. K. Selander, Appl. Environ. Microbiol. 58:1809–1815, 1992). Growth curves, melanin production, temperature tolerance, and megaplasmid profiles of the AT isolates were all coincident with these characteristics in strain Or191. In addition to the ability of all of these strains to nodulate alfalfa (
Medicago sativa
) inefficiently, the AT isolates also nodulated the common bean and
Leucaena leucocephala
, showing an extended host range for nodulation of legumes. In alfalfa, the time course of nodule formation by the AT isolate LPU 83 showed a continued nodulation restricted to the emerging secondary roots, which was probably related to the low rate of nitrogen fixation by the largely ineffective nodules. Results demonstrate the complexity of the rhizobial populations present in the acidic soils represented by a main group of N
2
-fixing rhizobia and a second group of ineffective and less-predominant isolates related to the AT strain Or191.
Identification of
Cryptosporidium felis
in a Cow by Morphologic and Molecular Methods
Authors: Bornay-Llinares Fernando J. , da Silva Alexandre J. , Moura Iaci N. S. , Myjak Przemysław , Pietkiewicz Halina , Kruminis-Łozowska Wiesława , Graczyk Thaddeus K. , Pieniazek Norman J. 
Published: December 2019

ABSTRACT

Apicomplexan
Cryptosporidium
parasites infect a wide range of vertebrate hosts. While some species are limited to a single host group, such as
Cryptosporidium baileyi
, which infects chickens, other species of this genus, such as
C. parvum
, infect a wide range of mammalian species from mice to humans. During an investigation of
Cryptosporidium
infection in cattle on a farm in northern Poland, we identified an infection caused by
C. felis
, in addition to known infections with
C. muris
and
C. parvum
. This new infection was identified based on the size of the oocysts (mean size, 4.3 ± 0.4 μm; range, 3.5 to 5.0 μm), as well as by analysis of the molecular sequence of the variable region of the small-subunit rRNA. This finding demonstrates the complex host specificity and circulation in the environment of
Cryptosporidium
species.
Cyclic-Imide-Hydrolyzing Activity of
d
-Hydantoinase from
Blastobacter
sp. Strain A17p-4
Authors: Soong Chee-Leong , Ogawa Jun , Honda Michinari , Shimizu Sakayu 
Published: December 2019

ABSTRACT

The cyclic-imide-hydrolyzing activity of a prokaryotic cyclic-ureide-hydrolyzing enzyme,
d
-hydantoinase, was investigated. The enzyme hydrolyzed cyclic imides with bulky substituents such as 2-methylsuccinimide, 2-phenylsuccinimide, phthalimide, and 3,4-pyridine dicarboximide to the corresponding half-amides. However, simple cyclic imides without substituents, which are substrates of imidase (i.e., succinimide, glutarimide, and sulfur-containing cyclic imides such as 2,4-thiazolidinedione and rhodanine), were not hydrolyzed. The combined catalytic actions of bacterial
d
-hydantoinase and imidase can cover the function of a single mammalian enzyme, dihydropyrimidinase. Prokaryotic
d
-hydantoinase also catalyzed the dehydrative cyclization of the half-amide phthalamidic acid to the corresponding cyclic imide, phthalimide. The reversible hydrolysis of cyclic imides shown by prokaryotic
d
-hydantoinase suggested that, in addition to pyrimidine metabolism, it may also function in cyclic-imide metabolism.
Microbiology of the Oil Fly,
Helaeomyia petrolei
Authors: Kadavy Dana R. , Plantz Bradley , Shaw Christopher A. , Myatt Jill , Kokjohn Tyler A. , Nickerson Kenneth W. 
Published: December 2019

ABSTRACT

Helaeomyia petrolei
larvae isolated from the asphalt seeps of Rancho La Brea in Los Angeles, Calif., were examined for microbial gut contents. Standard counts on Luria-Bertani, MacConkey, and blood agar plates indicated ca. 2 × 10
5
heterotrophic bacteria per larva. The culturable bacteria represented 15 to 20% of the total population as determined by acridine orange staining. The gut itself contained large amounts of the oil, had no observable ceca, and maintained a slightly acidic pH of 6.3 to 6.5. Despite the ingestion of large amounts of potentially toxic asphalt by the larvae, their guts sustained the growth of 100 to 1,000 times more bacteria than did free oil. All of the bacteria isolated were nonsporeformers and gram negative. Fourteen isolates were chosen based on representative colony morphologies and were identified by using the Enterotube II and API 20E systems and fatty acid analysis. Of the 14 isolates, 9 were identified as
Providencia rettgeri
and 3 were likely
Acinetobacter
isolates. No evidence was found that the isolates grew on or derived nutrients from the asphalt itself or that they played an essential role in insect development. Regardless, any bacteria found in the oil fly larval gut are likely to exhibit pronounced solvent tolerance and may be a future source of industrially useful, solvent-tolerant enzymes.
Disaccharides as a New Class of Nonaccumulated Osmoprotectants for
Sinorhizobium meliloti
Authors: Gouffi Kamila , Pica Nathalie , Pichereau Vianney , Blanco Carlos 
Published: December 2019

ABSTRACT

Sucrose and ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) are very unusual osmoprotectants for
Sinorhizobium meliloti
because these compounds, unlike other bacterial osmoprotectants, do not accumulate as cytosolic osmolytes in salt-stressed
S. meliloti
cells. Here, we show that, in fact, sucrose and ectoine belong to a new family of nonaccumulated sinorhizobial osmoprotectants which also comprises the following six disaccharides: trehalose, maltose, cellobiose, gentiobiose, turanose, and palatinose. Also, several of these disaccharides were very effective exogenous osmoprotectants for strains of
Rhizobium leguminosarum
biovars phaseoli and trifolii. Sucrose and trehalose are synthesized as endogenous osmolytes in various bacteria, but the other five disaccharides had never been implicated before in osmoregulation in any organism. All of the disaccharides that acted as powerful osmoprotectants in
S. meliloti
and
R. leguminosarum
also acted as very effective competitors of [
14
C]sucrose uptake in salt-stressed cultures of these bacteria. Conversely, disaccharides that were not osmoprotective for
S. meliloti
and
R. leguminosarum
did not inhibit sucrose uptake in these bacteria. Hence, disaccharide osmoprotectants apparently shared the same uptake routes in these bacteria. Natural-abundance
13
C nuclear magnetic resonance spectroscopy and quantification of cytosolic solutes demonstrated that the novel disaccharide osmoprotectants were not accumulated to osmotically significant levels in salt-stressed
S. meliloti
cells; rather, these compounds, like sucrose and ectoine, were catabolized during early exponential growth, and contributed indirectly to enhance the cytosolic levels of two endogenously synthesized osmolytes, glutamate and the dipeptide
N
-acetylglutaminylglutamine amide. The ecological implication of the use of these disaccharides as osmoprotectants is discussed.