bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Model of Thermal Destruction of
Bacillus stearothermophilus
Spores
Authors: Abraham Gerard , Debray Emile , Candau Yves , Piar Georges
Published: January 2020

The experimental survival curves of
Bacillus stearothermophilus
spores in aqueous suspension, for six constant temperatures ranging from 105 to 130°C, displayed an initial shoulder before a linear decline. To interpret these observations, we supposed that, before the heat treatment, the designated spore suspension contained a countable and mortal
N
0
population of activated spores and an
M
0
population of dormant spores which remained masked during spore counting and had to be activated before being destroyed by heat. We also hypothesized that the mechanisms of both activation and destruction are, at constant temperature, ruled by first-order kinetics, with velocity constants
k

A

and
k

D

, respectively. Mathematical analysis showed that this model could represent not only our experimental survival curves, but also all other shapes (linear and biphasic) of survival curves found in the literature; also, there is an inherent symmetry in the model formulation between the activation and destruction reactions, and we showed that the dormancy rate (τ =
M
0
/
N
0
) is the only parameter which permits a distinction between the two reactions. By applying the model to our experimental data and considering that the dormancy rate is not dependent on the treatment temperature, we showed that, for the studied suspension, the limiting reaction was the activation reaction.
Selective Medium for Isolating
Phanerochaete chrysosporium
from Soil
Authors: Dietrich Diane M. , Lamar Richard T.
Published: January 2020

A selective medium was developed that is capable of isolating
Phanerochaete chrysosporium
from soil. This medium contains 15 ppm of benomyl (15 μg g
−1
) and 550 ppm of streptomycin sulfate in 2% malt agar and is held at 39°C after inoculation.
P. chrysosporium
was isolated from three nonsterile forest soils to which the fungus had been added. These soils contained large microbial populations.
Restriction fragment length polymorphism of the Vibrio anguillarum serovar O1 virulence plasmid
Authors: Olsen J E , Larsen J L
Published: January 2020

Seventy-eight strains of Vibrio anguillarum serovar O1, all harboring one 65- to 70-kilobase plasmid, were typed according to restriction fragment length polymorphism of the plasmid. Six types, three of which comprised 96% of the strains examined, were produced with the restriction endonuclease BamHI. The fragment length polymorphism type did not correlate to any of 12 different phenotypic properties tested.
Highly selective medium for isolation of Listeria monocytogenes from food
Authors: al-Zoreky N , Sandine W E
Published: January 2020

A new selective medium (Al-Zoreky-Sandine listeria medium [ASLM]) was formulated to recover Listeria monocytogenes from food specimens; the medium completely inhibited common food microflora. Recognition of Listeria colonies is evident by black discoloration of the medium due to esculin hydrolysis without need for special illuminating equipment. The medium contains acriflavin, ceftazidime, and moxalactam as selective agents. Compared with Listeria Selective Agar, ASLM was equally effective in recovering L. monocytogenes. However, ASLM inhibited micrococci, enterococci, and gram-negative bacteria, especially a strain that mimicked L. monocytogenes on Listeria Selective Agar. The new medium was able to recover heat injured cells with only 15% less count than the nonselective medium.
Purification and Characterization of an Aspecific Glycoside Hydrolase from the Anaerobic Ruminal Fungus
Neocallimastix frontalis
Authors: Hebraud M. , Fevre M.
Published: January 2020

A glycoside hydrolase characterized by β-fucosidase (EC 3.2.1.38) and β-glucosidase (EC 3.2.1.21) activities was purified from the culture medium of the anaerobic ruminal phycomycete
Neocallimastix frontalis
grown on 0.5% Avicel. The enzyme had a molecular mass of 120 kilodaltons and a pI of 3.85. Optimal activity against
p
-nitrophenyl-β-
d
-fucoside and
p
-nitrophenyl-β-D-glucoside occurred at pH 6.0 and 50°C. The β-fucosidase and β-glucosidase activities were stable from pH 6.0 to pH 7.8 and up to 40°C. They were both inhibited by gluconolactone, sodium dodecyl sulfate,
p
-chloromercuribenzoate, and Hg
2+
cation. The enzyme had
K

m

s of 0.26 mg/ml for
p
-nitrophenyl-β-
d
-fucoside and 0.08 mg/ml for
p
-nitrophenyl-β-
d
-glucoside. The purified protein also had low β-galactosidase activity.
Genes from Cellvibrio mixtus encoding beta-1,3 endoglucanase
Authors: Sakellaris H , Pemberton J M , Manners J M
Published: January 2020

Two genes encoding beta-1,3 glucanase activity were cloned from the gram-negative soil bacterium Cellvibrio mixtus. The two clones, designated cwd (cell wall degradation) and lam (laminarin degradation), had distinct endonuclease restriction patterns and encoded enzymes with distinct substrate specificities. The 3.7-kilobase cwd insert encoded an enzyme which degraded yeast cell walls as well as the soluble beta-1,3 glucan laminarin and the insoluble beta-1,3 glucans zymosan and pachyman. The 1.8-kilobase lam insert encoded an enzyme which degraded laminarin only. Both enzymes degraded laminarin in an endohydrolytic manner to yield laminarobiose, laminarotriose, and laminarotetraose as major end products. Radiolabeled translation products of the cwd and lam transcripts were identified.
Production of a novel steroid sulfate metabolite [4,4,24-trimethylcholesta-8,14,24(28)-trien-2 alpha,3 beta,11 alpha,12 beta-tetrol 12-acetate, 3-sulfate] by Fusarium species and its biological activity
Authors: Burmeister H R , Vesonder R F
Published: January 2020

A novel steroid sulfate, 4,4,24-trimethylcholesta-8,14-24(28)-trien-2 alpha,3 beta,11 alpha,12 beta- tetrol 12-acetate, 3-sulfate, was discovered in Fusarium spp. Forty Fusarium strains belonging to F. sporotrichioides, F. chlamydosporum, E. equiseti, F. acuminatum, F. sambucinum, F. culmorum, and F. graminearum produced the steroid on white corn grits at 25 degrees C for 20 days. This steroid sulfate is one of the more abundant and easily attainable microbial steroids. At a concentration of 160 micrograms/ml, it inhibited the growth of six fungi, two gram-positive bacteria, and an alga, as well as the germination of both wheat and tomato seeds.
Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by
Pseudomonas
sp. Strain NCIMB 40135
Authors: Haywood Geoffrey W. , Anderson Alistair J. , Ewing David F. , Dawes Edwin A.
Published: January 2020

A number of
Pseudomonas
species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these,
Pseudomonas
sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C
2
to C
6
); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer synthesis occurred in batch culture after cessation of growth due to exhaustion of nitrogen. In continuous culture under nitrogen limitation up to 16.9% (wt/wt) polyhydroxyalkanoate was synthesized from glucose as the carbon source. The monomer units are mainly of the
R
-(−) configuration. Nuclear magnetic resonance studies confirmed the composition of the polymer. Differential scanning calorimetry suggested that the solvent-extracted polymer contained a significant proportion of crystalline material. The weight-average molecular weight of the polymer from glucose-grown cells was 143,000.
Mixotrophic and Autotrophic Growth of
Thiobacillus acidophilus
on Glucose and Thiosulfate
Authors: Pronk J. T. , Meulenberg R. , van den Berg D. J. C. , Batenburg-van der Vegte W. , Bos P. , Kuenen J. G.
Published: January 2020

Mixotrophic growth of the facultatively autotrophic acidophile
Thiobacillus acidophilus
on mixtures of glucose and thiosulfate or tetrathionate was studied in substrate-limited chemostat cultures. Growth yields in mixotrophic cultures were higher than the sum of the heterotrophic and autotrophic growth yields. Pulse experiments with thiosulfate indicated that tetrathionate is an intermediate during thiosulfate oxidation by cell suspensions of
T. acidophilus
. From mixotrophic growth studies, the energetic value of thiosulfate and tetrathionate redox equivalents was estimated to be 50% of that of redox equivalents derived from glucose oxidation. Ribulose 1,5-bisphosphate carboxylase (RuBPCase) activities in cell extracts and rates of sulfur compound oxidation by cell suspensions increased with increasing thiosulfate/glucose ratios in the influent medium of the mixotrophic cultures. Significant RuBPCase and sulfur compound-oxidizing activities were detected in heterotrophically grown
T. acidophilus
. Polyhedral inclusion bodies (carboxysomes) could be observed at low frequencies in thin sections of cells grown in heterotrophic, glucose-limited chemostat cultures. Highest RuBPCase activities and carboxysome abundancy were observed in cells from autotrophic, CO
2
-limited chemostat cultures. The maximum growth rate at which thiosulfate was still completely oxidized was increased when glucose was utilized simultaneously. This, together with the fact that even during heterotrophic growth the organism exhibited significant activities of enzymes involved in autotrophic metabolism, indicates that
T. acidophilus
is well adapted to a mixotrophic lifestyle. In this respect,
T. acidophilus
may have a competitive advantage over autotrophic acidophiles with respect to the sulfur compound oxidation in environments in which organic compounds are present.
Inverse Diauxy in the Yeast
Hansenula anomala
: Mutants Derepressed for Malic Acid Utilization in the Presence of Glucose
Authors: Côrte-Real Manuela , Leão C. , Van Uden N.
Published: January 2020

Utilization of
l
-malic acid by yeast strain
Hansenula anomala
IGC 4380 is subject to glucose repression. Derepressed mutants were obtained with UV light by use of the nonmetabolizable glucose analog 2-deoxyglucose as a selective agent. Three mutant strains degraded
l
-malic acid in the presence of up to 30% (wt/vol) glucose and are of potential interest for the biological deacidification of grape must. The mutant strains, as compared with the parent strain, displayed inverse diauxy in glucose-malate medium, glucose being metabolized only after malate consumption had been completed.
Bacteriochlorophyll and Photosynthetic Reaction Centers in
Rhizobium
Strain BTAi 1
Authors: Evans William R. , Fleischman Darrell E. , Calvert Harry E. , Pyati Padma V. , Alter Gerald M. , Rao N. S. Subba
Published: January 2020

Rhizobium
strain BTAi 1, which nodulates both stems and roots of
Aeschynomene indica
L., formed bacteriochlorophyll and photosynthetic reaction centers resembling those of purple photosynthetic bacteria when grown aerobically ex planta under a light-dark cycle. Bacteriochlorophyll formation was not observed under continuous dark or light growth conditions. The amount of pigment formed was similar to that previously found in aerobic photosynthetic bacteria. Stem nodules appear to fix nitrogen photosynthetically, as illumination of
A. indica
stem nodules with near-infrared light resulted in an enhanced rate of acetylene reduction. Near-infrared light did not enhance acetylene reduction when either
A. indica
or soybean root nodules were illuminated. The BTAi 1 isolate can be differentiated from members of the family
Rhodospirillaceae
by several criteria.
Chloromethane, Methyl Donor in Veratryl Alcohol Biosynthesis in
Phanerochaete chrysosporium
and Other Lignin-Degrading Fungi
Authors: Harper David B. , Buswell John A. , Kennedy James T. , Hamilton John T. G.
Published: January 2020

Chloromethane, a gaseous natural product implicated in methylation processes in
Phellinus pomaceus
, has been shown to act as methyl donor in veratryl alcohol biosynthesis in the lignin-degrading fungi
Phanerochaete chrysosporium, Phlebia radiata
, and
Coriolus versicolor
, none of which released detectable amounts of CH
3
Cl during growth. When
P. chrysosporium
was grown in a medium containing C
2
H
3
Cl, levels of C
2
H
3
incorporation into the 3- and 4-
O
-methyl groups of veratryl alcohol were very high and initially similar to those observed when the medium was supplemented with
l
-[
methyl
-
2
H
3
]methionine. When C
2
H
3
Cl was added to cultures actively synthesizing veratryl alcohol, incorporation of C
2
H
3
was very rapid, with 81% of veratryl alcohol labeled after 12 h. By contrast, incorporation of C
2
H
3
from
l
-[
methyl
-
2
H
3
]methionine was comparatively slow, attaining 10% after 12 h. It is proposed that these lignin-degrading fungi possess a tightly channeled multienzyme system in which CH
3
Cl biosynthesis is closely coupled to CH
3
Cl utilization for methylation of veratryl alcohol precursors.
Oxidation of Manganese and Iron by
Leptothrix discophora
: Use of
N,N,N′,N′
-Tetramethyl-
p
-Phenylenediamine as an Indicator of Metal Oxidation
Authors: de Vrind-de Jong E. W. , Corstjens P. L. A. M. , Kempers E. S. , Westbroek P. , de Vrind J. P. M.
Published: January 2020

A new method for the quantification and characterization of manganese-oxidizing activity by spent culture medium of
Leptothrix discophora
SS-1 was developed. It is based on the formation of the dye Wurster blue from
N,N,N′,N′
-Tetramethyl-
p
-phenylenediamine by oxidized manganese generated in the spent medium. The kinetic parameters thus obtained agreed well with data obtained with other methods. It was also possible to demonstrate iron oxidation by spent culture medium. The kinetics of the process and inhibition by enzyme poisons suggest that iron oxidation is enzymatically catalyzed. Probably two different factors are involved in manganese and iron oxidation.
Selection of Streptomyces ambofaciens mutants that produce large quantities of spiramycin and determination of optimal conditions for spiramycin production
Authors: Ford L M , Eaton T E , Godfrey O W
Published: January 2020

The aim of this work was to develop a strategy to isolate a morphologically stable mutant of Streptomyces ambofaciens ATCC 15154 which produced high titers of spiramycin. The rationale was to grow a nitrosoguanidine-mutated population for many generations under nonselective conditions followed by two cycles of protoplast formation and regeneration. A total of 2,400 surviving colonies were then screened for spiramycin production and subsequently checked for stability. From this experiment, strain 6-37 was isolated that produced 181 mg of spiramycin per liter and only one morphological type. The parent strain (ATCC 15154) produced 107 mg of spiramycin per liter and four morphological types. Strain 6-37 was then mutated with nitrosoguanidine, and 14,000 colonies were screened for spiramycin production. From this experiment, five strains were isolated that produced titers ranging from 187 to 373 mg of spiramycin per liter. Subsequent media and time studies with these strains resulted in a fermentation that produced 1,728 mg of spiramycin per liter.
Sensitivity to and Degradation of Pentachlorophenol by
Phanerochaete
spp
Authors: Lamar Richard T. , Larsen Michael J. , Kirk T. Kent
Published: January 2020

This research measured mycelial extension rates of selected strains of
Phanerochaete chrysorhiza, Phanerochaete laevis, Phanerochaete sanguinea, Phanerochaete filamentosa, Phanerochaete sordida, Inonotus circinatus
, and
Phanerochaete chrysosporium
and the ability of these organisms to tolerate and degrade the wood preservative pentachlorophenol (PCP) in an aqueous medium and in soil. Most of the tested species had mycelial extension rates in the range of ≤0.5 to 1.5 cm day
−1
, but there were large interspecific differences. A notable exception,
P. sordida
, grew very rapidly, with an average mycelial extension rate of 2.68 cm day
−1
at 28°C. Rank of species by growth rate was as follows:
P. chrysosporium > P. sordida > P. laevis > P. chrysorhiza = P. sanguinea > I. circinatus = P. filamentosa.
There were also significant intraspecific differences in mycelial extension rates. For example, mycelial extension rates among strains of
P. sordida
ranged from 1.78 to 4.81 cm day
−1
.
Phanerochaete
spp. were very sensitive to PCP. Growth of several species was prevented by the presence of 5 ppm (5 μg/g) PCP. However,
P. chrysosporium
and
P. sordida
grew at 25 ppm PCP, albeit at greatly decreased mycelial extension rates. In an aqueous medium, mineralization of PCP by
P. sordida
13 (ca. 12% after 30 days) was significantly greater than that by all other tested
P. sordida
strains and
P. chrysosporium.
After 64 days, the level of PCP had decreased by 96 and 82% in soil inoculated with
P. chrysosporium
and
P. sordida
, respectively. Depletion of PCP by these fungi occurred in a two-stage process. The first stage was characterized by a rapid depletion of PCP that coincided with an accumulation of pentachloroanisole (PCA). At the end of the first stage, ca. 64 and 71% of the PCP was converted to PCA in
P. chrysosporium
and
P. sordida
cultures, respectively. In the second stage, levels of PCP and PCA were reduced by 9.6 and 18%, respectively, in soil inoculated with
P. chrysosporium
and by 3 and 23%, respectively, in soil inoculated with
P. sordida.
PCA was mineralized by both
P. chrysosporium
and
P. sordida
in an aqueous medium.
Antiserum to Nitrogenase Generated from an Amplified DNA Fragment from Natural Populations of
Trichodesmium
spp
Authors: Zehr Jonathan P. , Limberger Ronald J. , Ohki Kaori , Fujita Yoshihiko
Published: January 2020

A fragment of the
nifH
gene was amplified from natural populations of
Trichodesmium
spp. and cloned into a maltose-binding protein (MBP) expression vector. The peptide product of the amplified 359-bp fragment of
nifH
was cleaved from the fusion protein, purified, and used to generate a specific antibody to the Fe protein of nitrogenase. The antiserum recognized the MBP-nitrogenase fusion protein and the cleaved
nif
peptide product but not MBP. The antibody cross-reacted with nitrogenase from natural populations of
Trichodesmium
spp. from the Caribbean Sea and with a cultured isolate from the Kuroshio waters (
Trichodesmium
sp. strain NIBB1067). The same
nifH
fragment was amplified, cloned, and sequenced from
Trichodesmium
sp. strain NIBB1067 and was found to be 98% identical at both the protein and DNA levels to
nifH
from the Caribbean populations. Three of the six nucleotide differences between the
Trichodesmium
sp. strain NIBB1067 and the
Trichodesmium
spp.
nifH
sequence had also been found in a second sequence from the natural populations, indicating either that there is more than one strain of
Trichodesmium
sp. in natural assemblages or that there are multiple copies of
nifH
in the genome. This DNA fragment, which is easily amplified with the polymerase chain reaction, may provide a good indicator of species relatedness without requiring extensive cloning or sequencing. Furthermore, the use of the polymerase chain reaction in combination with a MBP protein fusion vector provides a rapid method for production of highly specific sera, starting with a small amount of DNA.
Dissimilatory Selenate Reduction Potentials in a Diversity of Sediment Types
Authors: Steinberg Nisan A. , Oremland Ronald S.
Published: January 2020

We measured potential rates of bacterial dissimilatory reduction of
75
SeO
4
2−
to
75
Se
0
in a diversity of sediment types, with salinities ranging from freshwater (salinity = 1 g/liter) to hypersaline (salinity = 320 g/liter and with pH values ranging from 7.1 to 9.8. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO
4
2−
per ml of sediment added with isotope) ranged from 0.07 to 22 μmol of SeO
4
2−
reduced liter
−1
h
−1
. Activity followed Michaelis-Menten kinetics in relation to SeO
4
2−
concentration (
K

m

of selenate = 7.9 to 720 μM). There was no linear correlation between potential rates of SeO
4
2−
reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent
K

m

for selenate and with potential rates of denitrification (
r
= 0.92 and 0.81, respectively). NO
3
−
, NO
2
−
, MoO
4
2−
, and WO
4
2−
inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their
K

m

s.
Improved membrane filtration method incorporating catalase and sodium pyruvate for detection of chlorine-stressed coliform bacteria
Authors: Calabrese J P , Bissonnette G K
Published: January 2020

In vitro pure culture studies were conducted on three different strains of Escherichia coli (K-12, EPA 00244, and SWEI) to determine the effect of chlorination on catalase activity. In each case, stationary-phase cells exhibited significant (P less than 0.001) reductions in enzyme activity following exposure to chlorine. Mean differences in activity between control and chlorine-stressed cells ranged from 8.8 to 20.3 U/mg of protein for E. coli SWEI and EPA 00244, respectively. Following initial enzyme studies, resuscitation experiments utilizing the membrane filtration technique were conducted on chlorinated sewage effluent. Five different amendments, including catalase (1,000 U per plate), heat-inactivated catalase (1,000-U per plate), sodium pyruvate (0.05%), a catalase-sodium pyruvate combination (1,500 U/0.01%), and acetic acid (0.05%), were tested for the ability to enhance detection of chlorine-stressed cells on M-fecal coliform (M-FC), mT7, M-Endo, and tryptone-glucose-yeast extract (TGY) media. Significant (P less than 0.001) increases in recovery of fecal coliforms on M-FC, total coliforms on mT7 and M-Endo, and total heterotrophs on TGY were obtained on plates containing catalase, pyruvate, or the combination of these compounds. Supplementation with heat-inactivated catalase and acetic acid did not improve recovery of chlorine-stressed cells compared with recovery on nonamended media. Subsequent analysis of colonies from plates containing compounds which enhanced recovery indicated coliform verification percentages of greater than 80% on M-FC, greater than 90% on mT7, and greater than 94% on M-Endo media. These data suggest that the addition of peroxide-degrading compounds to various standard recovery media may improve detection of both coliform and heterotrophic bacteria in chlorinated waters.
Prolonged survival of Pseudomonas cepacia in commercially manufactured povidone-iodine
Authors: Anderson R L , Vess R W , Panlilio A L , Favero M S
Published: January 2020

Pseudomonas cepacia organisms were recently recovered from a povidone-iodine antiseptic solution. During the subsequent investigation, laboratory studies were initiated to determine the survival time of these organisms in the iodophor solution, which contains 1% titratable iodine. The solution was sampled weekly upon receipt in our laboratory, and P. cepacia was subsequently recovered through 29 weeks of sampling. Current laboratory data and lot production date information from the manufacturer indicate that P. cepacia survived for up to 68 weeks from the time of manufacture. Scanning electron microscopic examination of contaminated solution demonstrated bacterial cells embedded in extracellular material.
Chemical disinfection of hepatitis A virus on environmental surfaces
Authors: Mbithi J N , Springthorpe V S , Sattar S A
Published: January 2020

Hepatitis A virus disinfection was assessed on contaminated stainless-steel disks. Ten microliters of fecally suspended hepatitis A virus was deposited on the center of each disk, dried for 20 min, and then covered with 20 microliters of the test product for 1 min. Of the 20 formulations tested, only 2% glutaraldehyde, a quaternary ammonium formulation containing 23% HCl (toilet bowl cleaner), and sodium hypochlorite (greater than 5,000 ppm [greater than 5,000 micrograms/ml] of free chlorine) reduced the virus titer by greater than 99.9%; phenolics, iodine-based products, alcohols, and solutions of acetic, peracetic, citric, and phosphoric acids were unable to do so.
Degradation of Adsorbed Protein by Attached Bacteria in Relationship to Surface Hydrophobicity
Authors: Samuelsson Matts-Ola , Kirchman David L.
Published: January 2020

The relationships among surface energy, adsorbed organic matter, and attached bacterial growth were examined by measuring the degradation of adsorbed ribulose-1,5-bisphosphate carboxylase (a common algal protein) by attached bacteria (
Pseudomonas
strain S9). We found that surface energy (work of adhesion of water) determined the amount and availability of adsorbed protein and, consequently, the growth of attached bacteria. Percent degradation of adsorbed ribulose-1,5-bisphosphate carboxylase decreased with increasing hydrophobicity of the surface (decreasing work of adhesion). As a result, growth rates of attached bacteria were initially higher on hydrophilic glass than on hydrophobic polyethylene. However, during long (6-h) incubations, growth rates increased with surface hydrophobicity because of increasing amounts of adsorbed protein. Together with previous studies, these results suggest that the number of attached bacteria over time will be a complex function of surface energy. Whereas both protein adsorption and bacterial attachment decrease with increasing surface energy, availability of adsorbed protein and consequently initial bacterial growth rates increase with surface energy.
Isolation and sequence analysis of a beta-tubulin gene from Aspergillus flavus and its use as a selectable marker
Authors: Seip E R , Woloshuk C P , Payne G A , Curtis S E
Published: January 2020

An altered beta-tubulin gene that confers resistance to benomyl [whose active ingredient is 2-(methoxycarbonylamino)benzimidazole (MBC)] was isolated from a DNA library of Aspergillus flavus and used as a selectable marker for transformation. The beta-tubulin gene was cloned into a plasmid vector containing the pyr-4 gene of Neurospora crassa, and transformants were selected either for uracil prototrophy or MBC resistance. Transformants selected for uracil prototrophy were of three phenotypic classes: sensitive, intermediate, and resistant to MBC. Transforming DNA appeared to integrate at several sites in the genome, with the more resistant phenotypes having more copies of the altered beta-tubulin gene than the sensitive and intermediate phenotypes. Transformants were also selected on medium containing MBC. The average frequency of transformation (1 to 3 transformants per micrograms of transforming DNA) was lower than that obtained by selection for uracil prototrophy, presumably because of failure to select transformants that contained few copies of the altered beta-tubulin gene. The sequence of the beta-tubulin gene was determined and compared with the published sequence of the benA gene of A. nidulans; the beta-tubulin gene was found to be highly conserved between the two Aspergillus species. Notable differences were that the beta-tubulin gene of A. flavus lacks intron 6 present in benA and has an additional leucine at position 148. This is the first gene sequence reported from an aflatoxin-producing fungus and adds to the growing body of knowledge of the beta-tubulin genes and their use as selectable markers for transformation of filamentous fungi.
Chemotactic Responses of Marine
Vibrio
sp. Strain S14 (CCUG 15956) to Low-Molecular-Weight Substances under Starvation and Recovery Conditions
Authors: Malmcrona-Friberg Karin , Goodman Amanda , Kjelleberg Staffan
Published: January 2020

The chemotactic responses by starved cells of marine
Vibrio
sp. strain S14 differed from those elicited by cells that were not nutrient limited. The rate of chemotaxis at different concentrations of several attractants varied for starved and growing cells.
Vibrio
sp. strain S14 showed positive chemotaxis to leucine, valine, arginine, and glucose at the onset of energy and nutrient deprivation. A continued, though decreased, positive response was demonstrated fro leucine, arginine, and glucose at 10 h of starvation. Cells starved for 3 h displayed a stronger response to glucose than those starved for shorter or longer times. However, cells starved for 5 and 10 h responded more strongly to a lower concentration of glucose than did cells starved for 0 and 3 h. Starvation for 24 h elicited no measurable chemotaxis to leucine, arginine, or glucose. The motility decreased by over 95% in the cell population after 24 h of starvation, which resulted in a low sensitivity in the chemotaxis assay. A switch in the response to valine was observed by 3 h of starvation. The addition of nutrients of 22-h-starved cells elicited a temporary positive chemotactic response to leucine by 2 and 4 h of nutrient recovery, while cells at 1 and 6 h of recovery showed no response. At 2 h of recovery, the greatest response was recorded to 10
−4
M leucine, whereas at 4 h it was to 10
−2
M leucine. Ten to fifty percent of the 22-h-starved cell population regained their motility after 4 h of nutrient-aided recovery. It is possible that two types of chemosensory systems exist in marine bacteria. Starved and growing cells responded to different concentrations of the attractant, and growing cells displayed a saturated chemotactic system with leucine as the attractant, unlike the response during starvation.
Cloning of a lactate dehydrogenase gene from Clostridium acetobutylicum B643 and expression in Escherichia coli
Authors: Contag P R , Williams M G , Rogers P
Published: January 2020

A lactate dehydrogenase (LDH) gene of Clostridium acetobutylicum B643 was cloned on two recombinant plasmids, pPC37 and pPC58, that were selected by complementation of Escherichia coli PRC436 (acd), a fermentation-defective mutant that does not grow anaerobically on glucose. E. coli PRC436(pPC37) and PRC436(pPC58) grew anaerobically and fermented glucose to mostly lactate. When pPC37 and pPC58 were transformed into E. coli FMJ39 (ldh pfl), an LDH-deficient strain, the resulting strains grew anaerobically on glucose and produced lactate. Crude extracts of E. coli FMJ39(pPC37) and FMJ39(pP58) contained high LDH activity only when assayed for pyruvate reduction to lactate, and the LDH activity was activated 15- to 30-fold by the addition of fructose 1,6-diphosphate (FDP). E. coli FMJ39 had no detectable LDH activity, and E. coli LDH from a wild-type strain was not activated by FDP. Maxicell analysis showed that both plasmids pPC37 and pPC58 expressed a protein with an apparent Mr of 38,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Restriction endonuclease mapping of pPC37 and pPC58 and DNA hybridization studies indicated that a 2.1-kb region of these two clones of C. acetobutylicum DNA encodes the FDP-activated LDH.
Occurrence of Nitrate Reductase and Molybdopterin in
Xanthomonas maltophilia
Authors: Woodard Lisa M. , Bielkie Anthony R. , Eisses John F. , Ketchum Paul A.
Published: January 2020

Fifteen of 23 ATCC strains and 2 of 9 clinical isolates of
Xanthomonas maltophilia
, all of which grew aerobically on ammonia, but not nitrate, as a sole nitrogen source, reduced nitrate to nitrite.
X. maltophilia
failed to grow anaerobically on complex medium with or without nitrate, so it is considered an obligate aerobe. Nitrate-reducing strains contained reduced methyl viologen nitrate reductase (MVH-NR) with specific activities ranging from 49.2 to 192 U mg of protein
−1
. Strain ATCC 17666 doubled its cell mass after 3 h of growth on nitrate broth under low aeration, possessed maximal MVH-NR activity, and converted the added nitrate to nitrite, which accumulated. Dissolved oxygen above 15% saturation greatly suppressed nitrite formation. All strains, except ATCC 14535, possessed between 0.25 and 5.05 pmol of molybdopterin mg of protein
−1
as measured by the
Neurospora crassa nit-1
assay. The molybdopterin activity in the soluble fraction sedimented as a single symmetrical peak with an
s

20,
w

of 5.1. Studies identified MVH-NR in selected strains as a membrane-bound protein. The deoxycholate-solubilized MVH-NR sedimented as a single peak in sucrose density gradients with an
s

20,
w

of 8.8. The MVH-NR of
X. maltophilia
has the physical characteristics of a respiratory nitrate reductase and may enable cells to use nitrate as an electron sink under semiaerobic conditions.
Evaluation of antifungal volatile compounds on the basis of the elongation rate of a single hypha
Authors: Matsuoka H , Ii Y , Takekawa Y , Teraoka T
Published: January 2020

A novel method is proposed for the evaluation of the activity of an antifungal agent administered as a gas. This system is composed of a batch-flow type reaction vessel, a gas flow system, and a microscopic observation system. The agar plate was prepared on the ceiling of the reaction vessel, and the mycelium of a fungus (Aspergillus niger or Rhizoctonia solani) was inoculated onto it. After preincubation at 25 degrees C for 24 h, the reaction vessel was connected to the gas flow system. An appropriate hypha was selected, and its elongation rate was measured. Then a sample holder containing an antifungal compound was inserted into the reaction vessel from the side hole to saturate the atmosphere inside with its vapor. The retardation or inhibition of the hypha elongation was observed on a television monitor and recorded on a video tape recorder. The antifungal compound was then removed, and the reaction vessel was flushed with air. If the hypha lived, it began to elongate again. By this method, antifungal activity of seven odor compounds could be evaluated quantitatively within several hours.
Subunit Composition and Glycosidic Activities of the Cellulase Complex from
Clostridium thermocellum
JW20
Authors: Kohring S. , Wiegel J. , Mayer F.
Published: January 2020

The subunit composition of the extracellular complex from
Clostridium thermocellum
was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Twenty-six bands, representing proteins with apparent molecular sizes ranging from 37,500 to 185,000 Da, could be detected by silver staining. Cultivation of the bacteria with the substrate Avicel, Sigma cellulose, Solka floc, or cellobiose as the carbon source had no influence on the number of detectable protein bands. By activity staining with the substrate carboxymethyl cellulose or xylan added to the SDS-polyacrylamide gels, 15 of the 26 bands exhibited endoglucanase activity and 13 showed xylanase activity. In 8 of the 26 bands, both activities could be found. As minor activities, β-glucosidase, β-xylosidase, β-galactosidase, and β-mannosidase activities could be demonstrated in the cellulase complex. Upon measuring the release of
para
-nitrophenol (PNP) from PNP-cellobioside and determining the amount of glucose formed, the presence of exoglucanase activity was indicated. Upon glycoprotein staining of SDS-polyacrylamide gels, 14 of the 26 bands reacted positive, indicating the glycoprotein nature of the respective proteins. Four proteins (apparent molecular sizes, 58,000, 72,500, 94,000, and 110,000 Da) could be enriched from the originally bound cellulase complex by preparative SDS-PAGE. The two smaller proteins exhibited xylanase activity, whereas the 94,000-Da protein had endo- and exoglucanase activity, and the 110,000-Da protein degraded PNP-pyranosides.
Evidence for a Third Uptake Hydrogenase Phenotype among the Soybean Bradyrhizobia
Authors: van Berkum Peter
Published: January 2020

The existence of a hydrogen uptake host-regulated (Hup-hr) phenotype was established among the soybean bradyrhizobia. The Hup-hr phenotype is characterized by the expression of uptake hydrogenase activity in symbiosis with cowpea but not soybean. Uptake hydrogenase induction is not possible under free-living cultural conditions by using techniques developed for uptake hydrogenase-positive (Hup
+
)
Bradyrhizobium japonicum
. Hydrogen oxidation by Hup-hr phenotype USDA 61 in cowpea symbioses was significant because hydrogen evolution from nitrogen-fixing nodules was not detected. An examination for uptake hydrogenase activity in soybean and cowpea with 123 strains diverse in origin and serology identified 16 Hup
+
and 28 Hup-hr phenotype strains; the remainder appeared to be Hup
−
. The Hup-hr phenotype was associated with serogroups 31, 76, and 94, while strains belonging to serogroups 6, 31, 110, 122, 123, and 38/115 were Hup
+
. Hup
+
strains of the 123 serogroup typed positive with USDA 129-specific antiserum. The presence of the uptake hydrogenase protein in cowpea bacteroids of Hup
+
strains was demonstrated with immunoblot analyses by using antibodies against the 65-kDa subunit of uptake hydrogenase purified from strain SR470. However, the hydrogenase protein of Hup-hr strains was not detected. Results of Southern hybridization analyses with pHU1 showed the region of DNA with hydrogenase genes among Hup
+
strains to be similar. Hybridization was also obtained with Hup-hr strains by using a variety of cloned DNA as probes including hydrogenase structural genes. Both hydrogenase structural genes also hybridized with the DNA of four Hup
−
strains.
Utilization of nucleic acids by Selenomonas ruminantium and other ruminal bacteria
Authors: Cotta M A
Published: January 2020

Species of ruminal bacteria were screened for the ability to grow in media containing RNA or DNA as the energy source. Bacteroides ruminicola D31d and Selenomonas ruminantium HD4, GA192, and D effectively used RNA for growth, but not DNA. B. ruminicola D31d was able grow on nucleosides but not on bases or ribose. The S. ruminantium strains were able to grow when provided with either nucleosides or ribose but not bases. Strains of S. ruminantium, but not B. ruminicola D31d, were also able to use nucleosides as nitrogen sources. These data suggest that RNA fermentation may be a general characteristic of S. ruminantium.
Anaerobic phototrophic metabolism of 3-chlorobenzoate by Rhodopseudomonas palustris WS17
Authors: Kamal V S , Wyndham R C
Published: January 2020

A mixed phototrophic culture was found to reductively metabolize 3-chlorobenzoate in the presence of benzoate following adaptation for a period of 7 weeks. The dominant bacterial isolate from this mixed culture, identified as Rhodopseudomonas palustris WS17, metabolized 3-chlorobenzoate completely in the presence of benzoate and light and in the absence of oxygen. [14C]3-chlorobenzoate was converted to 14CO2 and cell 3-chlorobenzoate metabolism is a common phenomenon in this species.
Aerobic biodegradation of vinyl chloride in groundwater samples
Authors: Davis J W , Carpenter C L
Published: January 2020

Studies were conducted to examine the biodegradation of 14C-labeled vinyl chloride in samples taken from a shallow aquifer. Under aerobic conditions, vinyl chloride was readily degraded, with greater than 99% of the labeled material being degraded after 108 days and approximately 65% being mineralized to 14CO2.
Detection of coliform bacteria in water by polymerase chain reaction and gene probes
Authors: Bej A K , Steffan R J , DiCesare J , Haff L , Atlas R M
Published: January 2020

Polymerase chain reaction (PCR) amplification and gene probe detection of regions of two genes, lacZ and lamB, were tested for their abilities to detect coliform bacteria. Amplification of a segment of the coding region of Escherichia coli lacZ by using a PCR primer annealing temperature of 50 degrees C detected E. coli and other coliform bacteria (including Shigella spp.) but not Salmonella spp. and noncoliform bacteria. Amplification of a region of E. coli lamB by using a primer annealing temperature of 50 degrees C selectively detected E. coli and Salmonella and Shigella spp. PCR amplification and radiolabeled gene probes detected as little as 1 to 10 fg of genomic E. coli DNA and as a few as 1 to 5 viable E. coli cells in 100 ml of water. PCR amplification of lacZ and lamB provides a basis for a method to detect indicators of fecal contamination of water, and amplification of lamB in particular permits detection of E. coli and enteric pathogens (Salmonella and Shigella spp.) with the necessary specificity and sensitivity for monitoring the bacteriological quality of water so as to ensure the safety of water supplies.
Bacterial Production and Growth Rate Estimation from [
3
H]Thymidine Incorporation for Attached and Free-Living Bacteria in Aquatic Systems
Authors: Iriberri Juan , Unanue Marian , Ayo Bego�a , Barcina Isabel , Egea Luis
Published: January 2020

Production and specific growth rates of attached and free-living bacteria were estimated in an oligotrophic marine system, La Salvaje Beach, Vizcaya, Spain, and in a freshwater system having a higher nutrient concentration, Butron River, Vizcaya, Spain. Production was calculated from [
methyl
-
3
H]thymidine incorporation by estimating specific conversion factors (cells or micrograms of C produced per mole of thymidine incorporated) for attached and free-living bacteria, respectively, in each system. Conversion factors were not statistically different between attached and free-living bacteria: 6.812 � 10
11
and 8.678 � 10
11
μg of C mol
−1
for free-living and attached bacteria in the freshwater system, and 1.276 � 10
11
and 1.354 � 10
11
μg of C mol
−1
for free-living and attached bacteria in the marine system. Therefore, use of a unique conversion factor for the mixed bacterial population is well founded. However, conversion factors were higher in the freshwater system than in the marine system. This could be due to the different trophic conditions of the two systems. Free-living bacteria contributed the most to production in the two systems (85% in the marine system and 67% in the freshwater system) because of their greater contribution to total biomass. Specific growth rates calculated from production data and biomass data were similar for attached and free-living bacteria.
Determination of viability within serotypes of a soil population of Rhizobium leguminosarum bv. trifolii
Authors: Bottomley P J , Maggard S P
Published: January 2020

Concern has been raised about the percentage of viable cells within soil rhizobia populations measured by the immunofluorescence direct count method. The purpose of this study was to evaluate a direct viable count technique which is based on the fact that viable bacteria in natural populations undergo cell elongation when they are exposed to a combination of substrate and the inhibitor of DNA gyrase, nalidixic acid. A soil extraction procedure was developed to recover a high proportion of soil bacteria (ca. 10(9)/g of soil) in suspensions with an optical clarity suitable for accurate microscopic enumeration. After incubation for 16 to 20 h at 27 degrees C in the presence of yeast extract (200 mg/liter) and nalidixic acid (10 mg/liter), between 65 and 74% of the bacteria in soil suspension became significantly elongated (greater than or equal to 4.2 microns). In contrast, less than or equal to 0.5% of the same population could be cultured, regardless of the medium composition, nutrient concentration, or incubation conditions. The direct viable count method was combined with immunofluorescence to compare the percent viability and kinetics of appearance of elongated cells within serotypes of a soil population of Rhizobium leguminosarum bv. trifolii. Although the majority of these organisms were viable, as observed by immunofluorescence, we obtained evidence that subpopulations within the soil rhizobia community were in different states of competence to respond to substrate. A consistently low percentage (less than or equal to 30%) of the population of serotype 23 was elongated even after 24 h of incubation and regardless of when the soil was sampled.(ABSTRACT TRUNCATED AT 250 WORDS)
Degradation of pentachlorophenol by a Flavobacterium species grown in continuous culture under various nutrient limitations
Authors: Topp E , Hanson R S
Published: January 2020

A Flavobacterium sp. was grown in continuous culture limited for growth with ammonium, phosphate, sulfate, glucose, glucose + pentachlorophenol (PCP) (0.065 h -1), or PCP. Cells ere harvested, washed, and suspended to 3 x 10(7) cells ml (-1) in shake flasks containing a complete mineral salts medium without added carbon or supplemented with 50 mg of PCP ml(-1) or 50 mg of PCP ml(-1) + 100 mg of glucose ml(-1). The PCP concentration and the viable cell density were determined periodically. Cells that were grown under phosphate, glucose, or glucose + PCP limitation were more sensitive to PCP and took longer to degrade 50 mg of PCP ml(-1) than did cells that very were grown under ammonium, sulfate, or PCP limitation. Glucose stimulated viability and PCP degradation in all cases except when the cells were grown under carbon limitation with glucose and PCP added together as the carbon source. These results indicate that there is a relationship between nutrient limitation, phenotypic variation, and the sensitivity to and degradation of PCP by this organism.
Additive Effects of Alcohols, Their Acidic By-Products, and Temperature on the Yeast
Pachysolen tannophilus
Authors: Barbosa Maria de F. S. , Lee Hung , Collins-Thompson David L.
Published: January 2020

The effects of alcohols on the growth and fermentation of the yeast
Pachysolen tannophilus
were investigated at both 30 and 35�C. Addition of alcohols to the culture medium decreased both the growth rate and the final cell yield in a dose-dependent manner, and this decrease was more severe at 35�C. The concentration for 50% growth rate inhibition decreased as the chain length of the alcohol increased. In fermentations using a high initial cell density, production of acids was always observed when the medium was supplemented with alcohols. Supplementation of the culture medium with a short-chain alcohol plus the corresponding acid was shown to exert an additive deleterious effect on fermentation, and this effect increased with temperature. Production of acids was associated with the presence of alcohol dehydrogenase activity in cell extracts.
Bioconversion of possible T-2 toxin precursors by a mutant strain of Fusarium sporotrichioides NRRL 3299
Authors: McCormick S P , Taylor S L , Plattner R D , Beremand M N
Published: January 2020

Liquid cultures of a mutant strain of Fusarium sporotrichioides NRRL 3299 that accumulates trichodiene rather than T-2 toxin converted tricho-9-ene-2 alpha,3 alpha,11 alpha-triol, trichotriol (tricho-10-ene-2 alpha,3 alpha,9 alpha-triol), tricho-10-ene-2 alpha,3 alpha,9 beta-triol, 3 alpha-hydroxytrichothecene, and 3 alpha-acetoxytrichothecene to T-2 toxin. Other possible oxygenated precursors of T-2 toxin, including trichodiol (tricho-10-ene-2 alpha,9 alpha-diol), trichothecene, 4 alpha-hydroxytrichothecene, and 15-hydroxytrichothecene, were not metabolized. The results indicate that in the biosynthesis of T-2 toxin by F. sporotrichioides, (i) oxygenation at C-3 occurs prior to the second cyclization, (ii) this second cyclization involves two steps that may be nonenzymatic, and (iii) oxidation at C-3 precedes that at C-4 or C-15.