bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of the Most-Probable-Number Technique for Enumerating Rhizobia in Tropical Soils
Authors: Woomer Paul L. , Singleton Paul W. , Bohlool B. Ben
Published: January 2020

We used six rhizobium-legume systems to test the reliability of the most-probable-number (MPN) technique for enumerating rhizobia introduced into 14 sites representing four soil orders. The range-of-transition values (the number of dilution steps between the first not-entirely-positive and the last not-entirely-negative growth units) were compared for each species and for each soil. The probability that the observed data were significantly different from theoretical values varied with the species. The acceptability of MPN codes (
P
> 0.99) was the highest (97 to 99%) with
Vicia sativa, Trifolium repens,
and
Glycine max
and lowest (72%) with
Leucaena leucocephala. Medicago sativa
and
Macroptilium atropurpureum
yielded 87 and 75% acceptable MPN codes, respectively. The acceptability of the MPN data obtained for a host species was related to rooting habit and time to nodulation. Comparison of data for each soil indicated that, despite large differences in characteristics, the soil was not a major source of variability in the MPN counts. There was no significant interaction of the range of transition of rhizobium-legume plant infection count data between species and site.
Production and Characteristics of Avicel-Digesting and Non-Avicel-Digesting Cellobiohydrolases from
Aspergillus ficum
Authors: Hayashida Shinsaku , Mo Kaiguo , Hosoda Akira
Published: January 2020

Two immunologically related cellobiohydrolases, cellobiohydrolase I (CBH I) and cellobiohydrolase II (CBH II), were purified from
Aspergillus ficum.
The Avicel-adsorbable CBH I (molecular weight, 128,000) digested Avicel, cotton, and cellulose powder to cellobiose, but the Avicel-unadsorbable CBH II (molecular weight, 50,000) could not digest those substrates. Both enzymes hydrolyzed insoluble cellooligosaccharides (25) to cellobiose. High-pressure liquid chromatographic analysis of soluble cellooligosaccharide hydrolysates revealed that both enzymes split off strictly cellobiose units from the nonreducing end of the cellulose chain with an exowise mechanism. CBH I showed glucosyltransferase activity, but CBH II did not. The
N
-bromosuccinimideoxidized CBH I was completely inactive but retained the ability to adsorb to Avicel. This suggested that CBH I has separate sites for binding to cellulose and for catalyzing cleavage of glycosidic linkages. Cellobiohydrolases were of two types, CBH I and CBH II. The former can adsorb to and digest Avicel, while the latter can do neither.
Plasmid profiles as indicators of the source of contamination of Staphylococcus aureus endemic within poultry processing plants
Authors: Dodd C E , Chaffey B J , Waites W M
Published: January 2020

A total of 530 strains of Staphylococcus aureus were isolated from the defeathering machinery of a chicken processing plant and from neck skin samples of carcasses at different stages of processing in two visits 4 weeks apart. Eleven different plasmid profiles were detected in the isolates, eight being common to both visits. The plasmid profiles of the strains forming the majority of the population on the freshly slaughtered birds were rarely present in the strains isolated from the pluckers (except at the entry to the first plucker) and were present in only a small proportion of the strains isolated from carcasses after plucking. However, the profiles from the strains isolated from the pluckers on both visits were different from those forming the majority of the population on the incoming birds but formed the major part of the carcass flora after plucking, suggesting that such strains were endemic. These strains were found as a small proportion of the isolates made from the incoming birds, suggesting that this was the route by which the endemic strains were introduced into the plant. Such endemic strains exhibited a clumping growth, even in liquid shake culture, which may have made it easier for them to become established on the pluckers and to resist cleaning and disinfection. This clumping phenotype was correlated with the presence of a 7.5-megadalton plasmid.
Phospholipid Fatty Acid Composition of the Syntrophic Anaerobic Bacterium
Syntrophomonas wolfei
Authors: Henson J. Michael , McInerney Michael J. , Beaty P. Shawn , Nickels Janet , White David C.
Published: January 2020

The membrane phospholipid fatty acids (PLFAs) from several cocultures and a pure culture of
Syntrophomonas wolfei
were determined by capillary column gas chromatography. Cocultures of
S. wolfei
with a
Desulfovibrio
sp. contained PLFAs from both organisms, whereas PLFAs from a coculture with
Methanospirillum hungatei
contained very little biomass to analyze. The pure culture of
S. wolfei
grown on crotonate provided the best material for analysis of the PLFAs. The predominant PLFAs of
S. wolfei
were the monounsaturated 16:1ω7c and 16:1ω9c and the saturated 16:0 and 14:0. A low concentration of the diunsaturated 18:2ω6 was detected. The PLFA analysis provides additional information for consideration in the determination of the profile of PLFAs obtained from anaerobic environments. In addition, this information may aid in the understanding of the physiology and phylogeny of
S. wolfei
and other syntrophic bacteria.
National field evaluation of a defined substrate method for the simultaneous enumeration of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube fermentation method
Authors: Edberg S C , Allen M J , Smith D B
Published: January 2020

A defined substrate method was developed to simultaneously enumerate total coliforms and Escherichia coli from drinking waters without the need for confirmatory or completed tests. It is a new method based on technology that uses a hydrolyzable substrate as a specific indicator-nutrient for the target microbes. No equipment other than a 35 degrees C incubator and long-wavelength (366-nm) light is necessary. To perform the test, one only has to add water to the powdered ingredients in a tube or flask. If total coliforms are present in the water sample, the solution will change from its normal colorless state (no target microbes present) to yellow. The specific presence of E. coli will cause the same tube to fluoresce under a longwave (366-nm) UV lamp. The test, called Autoanalysis Colilert (AC), was compared with Standard Methods for the Examination of Water and Wastewater 10-tube multiple tube fermentation (MTF) in a national evaluation. Five utilities, representing six U.S. Environmental Protection Agency regions, participated. All water samples came from distribution systems. Split samples from a wide variety of water sources were analyzed for the MPN-versus-MPN comparison. A total of 1,086 tubes were positive by MTF, and 1,279 were positive by AC. There was no statistical difference between MTF and AC. Species identifications from positive tubes confirmed the sensitivity of the AC. A national evaluation of the AC test showed that it: (i) was as sensitive as Standard Methods MTF, (ii) specifically enumerated 1 total coliform per 100 ml, in a maximum of 24 h, (iii) simultaneously enumerated 1 E. coli per 100 ml in the same analysis, (iv) was not subject to false-positive or false-negative results by heterotrophic bacteria, (v) did not require confirmatory tests, (vi) grew injured coliforms, (vii) was easy to inoculate, and (viii) was very easy to interpret.
Molecular filtration for recovery of waterborne viruses of fish
Authors: Watanabe R A , Fryer J L , Rohovec J S
Published: January 2020

The effectiveness of tangential flow filtration (TFF) for the recovery of infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) from large volumes of water was evaluated. In laboratory studies, virus recovery from IHNV-seeded water following concentration by TFF was approximately 13%. However, the addition of 0.1 and 1% fetal bovine serum to deionized water stabilized the virus, increasing virus recoveries to 95%. The addition of 0.03 and 0.3% beef extract resulted in IHNV recoveries of 80 and 61%, respectively. Similar results were obtained with IPNV-seeded water. Field studies using the TFF procedure were conducted with water from areas where IHNV is endemic. IHNV was detected in effluent from an adult steelhead trout (Salmo gairdneri) holding pond at an estimated concentration of 1 PFU/5 ml of water. It was also detected at levels of 1 PFU/50 ml in water from a 2-m-diameter circular tank containing IHNV-infected steelhead trout fry. IHNV isolated in samples taken from the Metolius River was detected by TFF at estimated levels of 1 PFU/3 liters.
Formation and regeneration of protoplasts and spheroplasts of gastrointestinal strains of lactobacilli
Authors: Connell H , Lemmon J , Tannock G W
Published: January 2020

Methods were developed for the formation of protoplasts and spheroplasts of gastrointestinal strains of Lactobacillus reuteri, Lactobacillus gasseri, and Lactobacillus salivarius. Attempts to regenerate vegetative cells from protoplasts were not successful, but spheroplasts could be regenerated consistently for five of six strains.
Synthesis of Exopolysaccharide by
Bradyrhizobium japonicum
during Growth on Hydroaromatic Substrates
Authors: Tully Raymond E.
Published: January 2020

The hydroaromatic acids shikimate and quinate, which may be available as carbon sources in the soil, supported production of only low levels of acidic exopolysaccharide by
Bradyrhizobium japonicum.
Exopolysaccharide production (micrograms per 10
9
cells) was 4.9 on quinate and 4.5 on shikimate; in comparison, it was 128 on adipate, 18 on
l
-arabinose, and 39 on
d
-glucose.
Crosses among Homokaryons from Commercial and Wild-Collected Strains of the Mushroom
Agaricus brunnescens
(=
A. bisporus
)
Authors: Castle Alan J. , Horgen Paul A. , Anderson James B.
Published: January 2020

A new technique for the production of hybrid strains of the cultivated mushroom
Agaricus brunnescens
is described. Homokaryons were recovered from regenerated protoplasts obtained from several heterokaryotic strains. A total of 16 novel hybrids were produced in 63 attempted crosses between paired homokaryons. Recovery of both homokaryons and hybrids was verified by analysis of restriction fragment length polymorphisms. Three of four hybrids fruited in small-scale tests, further confirming that the isolates were true hybrids. Colony morphology alone was found to be a poor indicator of hybrid status. In two instances, three homokaryons crossed successfully in all combinations, suggesting that there are at least three alleles at the putative mating-type locus. Crosses between homokaryons from commercial and wild-collected isolates indicated that these strains belong to the same biological species.
Chemotaxis in the Marine Fungus
Rhizophydium littoreum
Authors: Muehlstein Lisa K. , Amon James P. , Leffler Deborah L.
Published: January 2020

Zoospores of the marine chytrid
Rhizophydium littoreum
are attracted to a variety of substances common to their environment. In general, carbohydrates and polysaccharides elicited strong concentration-dependent positive responses. There was no direct correlation between all substances used as foods and those stimulating positive responses. The chemotactic activities of this organism should, however, tend to bring it toward concentrated food sources.
Isolation and characterization of trichothecin from corn cultures of Fusarium graminearum MRC 1125
Authors: Combrinck S , Gelderblom W C , Spies H S , Burger B V , Thiel P G , Marasas W F
Published: January 2020

Trichothecin was isolated and purified from corn cultures of a toxic strain of Fusarium graminearum. This strain, designated MRC 1125, was obtained from corn in southern Africa. The brine shrimp toxicity assay was used throughout the isolation procedure to monitor the toxicity of the fractions. The compound was characterized by detailed 1H (500-MHz) and 13C (125-MHz) nuclear magnetic resonance spectroscopy and mass spectrometry. This is the first report of the production of trichothecin by a Fusarium species.
Immobilization of Leachable Toxic Soil Pollutants by Using Oxidative Enzymes
Authors: Shannon Michael J. R. , Bartha Richard
Published: January 2020

Screening of leachable toxic chemicals in a horseradish peroxidase-H
2
O
2
immobilization system established that immobilization was promising for most phenolic pollutants but not for benzoic acid, 2,6-dinitrocresol, or dibutyl phthalate. The treatment did not mobilize inherently nonmobile pollutants such as anilines and benzo[
a
]pyrene. In a separate study, an extracellular laccase in the culture filtrate of
Geotrichum candidum
was selected from five fungal enzymes evaluated as a cost-effective substitute for horseradish peroxidase. This enzyme was used in demonstrating the immobilization and subsequent fate of
14
C-labeled 4-methylphenol and 2,4-dichlorophenol in soil columns. When applied to Lakewood sand, 98.1% of 4-methylphenol was leached through with distilled water. Two days after immobilization treatment with the
G. candidum
culture filtrate, only 9.1% of the added 4-methylphenol was leached with the same volume of water. Of the more refractory test pollutant 2,4-dichlorophenol, 91.6% had leached at time zero and 48.5% had leached 1 day after the immobilization treatment. However, 2 weeks after immobilization, only 12.0% of the 2,4-dichlorophenol was leached compared with 61.7% from the control column that received no immobilization treatment. No remobilization of the bound pollutants was detected during 3- and 4-week incubation periods. Enzymatic immobilization of phenolic contaminants in soil appears to be a promising technique for the reduction of groundwater pollution by such substances.
Photolysis primes biodegradation of benzo[a]pyrene
Authors: Miller R M , Singer G M , Rosen J D , Bartha R
Published: January 2020

14C-labeled benzo[a]pyrene (BaP) was used as a model-compound for polycyclic aromatic hydrocarbons (PAH) in order to assess the effect of photolytic pretreatment on the subsequent fate of BaP in sewage sludge and soil test systems. Photolysis was performed in methanolic solution with or without 0.1 M H2O2, under either UV light (300 nm) or natural sunlight. The presence of H2O2 greatly enhanced the rate of photolysis both with UV and with natural sunlight. Intact BaP resisted biodegradation in both test systems. Photolysis transformed BaP to polar materials that were subject to increased mineralization and binding in both biological test systems. As shown by the Ames assay, photolysis decreased the mutagenicity of BaP to test strains TA98 and TA104 only moderately. The photolysate had an increased acute toxicity and lost its need for activation by S-9 enzymes. However, during subsequent incubation in soil or sewage sludge, mutagenicity decreased rapidly by one to two orders of magnitude and acute toxicity disappeared due to the mineralization and binding of photoproducts to humic materials. Photolysis of BaP and similar PAH compounds represents a useful treatment option that could be applied to certain PAH-containing petroleum refinery sludge and to coal tar residues in order to facilitate their detoxification and environmentally safe disposal.
Comparison of Streptococcus zooepidemicus and influenza virus pathogenicity in mice by three pulmonary exposure routes
Authors: Sherwood R L , Thomas P T , Kawanishi C Y , Fenters J D
Published: January 2020

Pulmonary infections may be induced in experimental animals by using several exposure routes. Inhalation of microbial aerosols is often viewed as the most relevant exposure route, although the comparability of either intranasal (i.n.) or intratracheal (i.t.) inoculation to aerosol inhalation is unclear. In these studies, the infection of mice with either Streptococcus zooepidemicus or influenza virus was compared following i.n., i.t., or aerosol challenge. The 50% lethal dose was determined by each exposure route for both microbes, and the organ clearance of a 50% lethal dose was determined. Mice were as or more sensitive to bacterial or viral infection following i.n. or i.t. instillation as compared with aerosol challenge. Organ clearance patterns of virus or bacteria varied slightly with exposure route.
Oxidation of Thianthrene by the Ligninase of
Phanerochaete chrysosporium
Authors: Schreiner Roger P. , Stevens S. Edward , Tien Ming
Published: January 2020

The oxidation of heterocyclic sulfur compounds reported to be part of the macrostructure of coal and petroleum was investigated. The oxidation of thianthrene solubilized in 10% dimethylformamide to thianthrene monosulfoxide in the presence of hydrogen peroxide was catalyzed by the ligninase from
Phanerochaete chrysosporium
.
Acetate Inhibition of Methanogenic, Syntrophic Benzoate Degradation
Authors: Dolfing Jan , Tiedje James M.
Published: January 2020

Acetate inhibited benzoate degradation by a syntrophic coculture of an anaerobic benzoate degrader (strain BZ-2) and
Methanospirillum
strain PM-1; the apparent
K

i

for acetate was approximately 40 mM. The addition of acetate resulted in a decrease in the hydrogen concentration in the coculture, indicating that phenomena related to interspecies hydrogen transfer affected this value and that the effect of acetate on the benzoate-degrading partner was probably greater than the apparent
K

i

for the coculture suggests.
Novel compound for identifying Escherichia coli
Authors: Watkins W D , Rippey S R , Clavet C R , Kelley-Reitz D J , Burkhardt W
Published: January 2020

A new chromogenic compound, 5-bromo-4-chloro-3-indoxyl-beta-D-glucuronide, was found to be useful for the rapid, specific, differential identification of Escherichia coli in the sanitary analysis of shellfish and wastewater. Of 1,025 presumptively positive colonies (blue) and 583 presumptively negative colonies (nonblue), only 1% false-negative and 5% false-positive results were found.
Optimum pH levels for eluting enteroviruses from sludge solids with beef extract
Authors: Berg G , Sullivan G
Published: January 2020

This study demonstrates that elution of enteroviruses from a mixture of primary- and activated-sludge solids with beef extract at pH 9.2 +/- 0.2 may be less efficient than elution with beef extract at pH 7.2 +/- 0.2 and that elution of enteroviruses from extended-aeration-sludge solids with beef extract is at best no more efficient at pH 9.2 +/- 0.2 than at pH 7.2 +/- 0.2. Thus, the common practice of adjusting the pH of beef extract used for eluting enteroviruses from the natural neutral level of the elutant to alkaline levels is unnecessary and probably undesirable.
Estimating Bacterial Production in Marine Waters from the Simultaneous Incorporation of Thymidine and Leucine
Authors: Chin-Leo Gerardo , Kirchman David L.
Published: January 2020

We examined the simultaneous incorporation of [
3
H]thymidine and [
14
C]leucine to obtain two independent indices of bacterial production (DNA and protein syntheses) in a single incubation. Incorporation rates of leucine estimated by the dual-label method were generally higher than those obtained by the single-label method, but the differences were small (dual/single = 1.1 ± 0.2 [mean ± standard deviation]) and were probably due to the presence of labeled leucyl-tRNA in the cold trichloroacetic acid-insoluble fraction. There were no significant differences in thymidine incorporation between dual- and single-label incubations (dual/ single = 1.03 ± 0.13). Addition of the two substrates in relatively large amounts (25 nM) did not apparently increase bacterial activity during short incubations (<5 h). With the dual-label method we found that thymidine and leucine incorporation rates covaried over depth profiles of the Chesapeake Bay. Estimates of bacterial production based on thymidine and leucine differed by less than 25%. Although the need for appropriate conversion factors has not been eliminated, the dual-label approach can be used to examine the variation in bacterial production while ensuring that the observed variation in incorporation rates is due to real changes in bacterial production rather than changes in conversion factors or introduction of other artifacts.
Effects of an abrupt diet change from hay to concentrate on microbial numbers and physical environment in the cecum of the pony
Authors: Goodson J , Tyznik W J , Cline J H , Dehority B A
Published: January 2020

Microbial numbers, pH, fluid volume, and turnover rate in the pony cecum were measured during an abrupt change from an all-forage to an all-concentrate diet, both fed at maintenance energy levels. Concentrate feeding resulted in increased (P less than 0.01) numbers of total viable anaerobic bacteria. The numbers of organisms growing on selective starch medium increased (P less than 0.01) when concentrate was fed, while numbers on xylan and pectin media decreased (P less than 0.025). Seven days after the diet change to concentrate, the number of bacteria growing on lactate medium increased (P less than 0.01), followed by a gradual decline. Cellulolytic bacteria occurred in low numbers, ranging from 1.1 x 10(4) to 4.4 x 10(4) per g of cecal contents. Feeding all concentrate decreased both the number of genera (P less than 0.01) and total protozoan numbers (P less than 0.01) in the cecum. Minimum cecal pH values of 6.4 and 5.8 were obtained when forage and concentrate, respectively, were fed, with the minimum pH occurring 6 h postfeeding. Dry-matter percentage of cecal contents followed a diurnal pattern which was the inverse of the pH curve. During forage feeding, the cecum contained an average of 2.2 liters (1.6 to 3.4 liters), which turned over 3.9 times per day. When concentrate was fed, cecal volume averaged 3.9 liters (0.6 to 8.6 liters), with a mean liquid turnover of 4.2 times per day. Microbial numbers and pH changes in the pony cecum associated with an abrupt change in diet from hay to concentrate resembled those which occur in the rumen under similar feeding conditions.
Importance of mucopolysaccharides as substrates for Bacteroides thetaiotaomicron growing in intestinal tracts of exgermfree mice
Authors: Salyers A A , Pajeau M , McCarthy R E
Published: January 2020

We used two approaches to determine whether the mucopolysaccharide chondroitin sulfate is an important source of carbon and energy for Bacteroides thetaiotaomicron in the intestinal tracts of germfree mice. First, we tested the ability of three mutants that grew poorly or not at all on chondroitin sulfate to colonize the intestinal tract of a germfree mouse and to compete with wild-type B. thetaiotaomicron in this model system. One mutant (CG10) was rapidly outcompeted by the wild type. However, since this mutant was unable to grow on chondroitin sulfate because it could not grow on N-acetyl-galactosamine, one of its monosaccharide components, this mutant might also be unable to utilize glycoprotein mucins. Two mutants (46-1 and 46-4) were isolated that grew poorly on chondroitin sulfate but normally on both component sugars. One of them was outcompeted by the wild type, but the percent wild type increased more slowly than with CG10. In one experiment, the percent wild type never reached 100%. The other (46-4) was not outcompeted by the wild type. These results indicate that, although chondroitin sulfate may be a carbon source in the animal, it is not of major importance. Our second approach was to determine by immunoblot analysis whether a 28-kilodalton outer membrane protein that is produced by B. thetaiotaomicron only when it is grown on chondroitin sulfate or hyaluronic acid was being produced at induced level by B. thetaiotaomicron growing in the ceca of exgermfree mice. There was no evidence for induction of this protein in vivo. Thus, the immunoblot results are consistent with results of the mutant competition experiments.
Effects of acidification on mercury methylation, demethylation, and volatilization in sediments from an acid-susceptible lake
Authors: Steffan R J , Korthals E T , Winfrey M R
Published: January 2020

The effect of experimental acidification on mercury methylation, demethylation, and volatilization was examined in surficial sediment samples from a weakly buffered northern Wisconsin lake. All mercury transformations were measured with radioisotopic tracers. Acidification of sediment pH with H2SO4, HCl, or HNO3 significantly decreased 203Hg(II) methylation. Acidification of pH 6.1 (ambient) sediments to pH 4.5 with either H2SO4 or HCl inhibited methylation by over 65%. The decreased methylation was due to the increased hydrogen ion concentration because methylation was not affected by concentrations of Na2SO4 or NaCl equimolar to the amount of acid added. Inhibition of methylation was observed even after prolonged acidification of sediments to pH 5.0 for up to 74 days. Acidification of sediments to pH 5.5, 4.5, and 3.5 with HNO3 resulted in a near complete inhibition of methylation at each pH. Similarly, the addition of equimolar amounts of NaNO3 resulted in a near complete inhibition of methylation, indicating that the inhibition was due to the nitrate ion rather than to the acidity. Demethylation of methyl mercury was not affected by pHs between 8.0 and 4.4, but sharply decreased below pH 4.4. Volatilization of 203Hg(II) from surface sediments was less than 2% of methylation activity and was not significantly different from that in killed sediments. This study indicated that acidification of sediments inhibits mercury methylation and that the observed increase in the mercury burdens in fish from low pH lakes is not due to increased production of methylmercury in sediments.
Experimental Evaluation of Conversion Factors for the [
3
H]Thymidine Incorporation Assay of Bacterial Secondary Productivity
Authors: Coveney Michael F. , Wetzel Robert G.
Published: January 2020

The relationship between bacterial growth and incorporation of [
methyl
-
3
H]thymidine in oligotrophic lake water cultures was investigated. Prescreening, dilution, and addition of organic and inorganic nutrients were treatments used to prevent bacterivory and stimulate bacterial growth. Growth in unmanipulated samples was estimated through separate measurements of grazing losses. Both bacterial number and biovolume growth responses were measured, and incorporation of [
3
H]thymidine in both total macromolecules and nucleic acids was assayed. The treatments had significant effects on conversion factors used to relate thymidine incorporation to bacterial growth. Cell number-based factors ranged from 1.1 × 10
18
to 38 × 10
18
cells mol of total thymidine incorporation
−1
and varied with treatment up to 10-fold for the same initial bacterial assemblage. In contrast, cell biovolume-based conversion factors were similar for two treatment groups across a 16-fold range of [
3
H]thymidine incorporation rates: 5.54 × 10
17
μm
3
mol of total thymidine incorporation
−1
and 15.2 × 10
17
μm
3
mol of nucleic acid incorporation
−1
. Much of the variation in cell number-based conversion factors was related to changes in apparent mean cell volume of produced bacteria. Phosphorus addition stimulated [
3
H]thymidine incorporation more than it increased bacterial growth, which resulted in low conversion factors.
Relationship between nitrogen-fixing sulfate reducers and fermenters in salt marsh sediments and roots of Spartina alterniflora
Authors: Gandy E L , Yoch D C
Published: January 2020

A combination of inhibitors and carbon substrates was used to determine the relative contribution of sulfate-reducing bacteria (SRB) and fermenting bacteria to nitrogen fixation in a salt marsh sediment and on the roots of Spartina alterniflora. Because a lag period precedes acetylene-reducing activity (ARA) in amended sediments, an extensive analysis was done to be sure that this activity was due to the activation of dormant cells, not simply to cell proliferation. Since ARA was not affected by metabolic inhibitors such as rifampin, nalidixic acid, or methionine sulfoximine, it appeared that cell growth was not responsible for this activity. Instead, dormant cells were being activated by the added energy source. Molybdate inhibition studies with glucose-amended sediment slurries indicated that ARA in the upper 5 cm of the salt marsh was due primarily (70%) to SRB and that below that level (5 to 10 cm) it was due primarily (greater than 90%) to fermenting bacteria. ARA associated with washed roots of intact S. alterniflora plants was not inhibited by molybdate, which indicates that bacteria other than SRB were responsible. However, when the roots were excised from the plant, the activity (per unit of root mass) was 10-fold higher and was severely inhibited by molybdate. While this high activity is probably an artifact, due to the release of oxidizable substrates from the excised roots, it indicates that SRB are present in high numbers on Spartina roots.
Fusarium Wilt Suppression and Agglutinability of
Pseudomonas putida
Authors: Tari P. H. , Anderson A. J.
Published: January 2020

Mutants of
Pseudomonas putida
(Agg
−
) that lack the ability to agglutinate with components present in washes of bean and cucumber roots showed limited potential to protect cucumber plants against
Fusarium oxysporum
f. sp.
cucumerinum
. However, a higher level of protection was observed against
Fusarium
wilt in cucumber plants coinoculated with the parental bacterium (Agg
+
), which was agglutinable. The Agg
−
mutants did not colonize the roots of cucumber plants as extensively as the Agg
+
parental isolate did. In competition experiments involving bean roots inoculated with a mixture of Agg
+
and Agg
−
bacteria, the Agg
+
strains colonized roots to a greater extent than the Agg
−
cells did. These data suggest that the Agg
+
phenotype provides additional interactions that aid in the beneficial character of
P. putida.
Hydrogen Peroxide Metabolism in Yeasts
Authors: Verduyn Cornelis , Giuseppin Marco L. F. , Scheffers W. Alexander , van Dijken Johannes P.
Published: January 2020

A catalase-negative mutant of the yeast
Hansenula polymorpha
consumed methanol in the presence of glucose when the organism was grown in carbon-limited chemostat cultures. The organism was apparently able to decompose the H
2
O
2
generated in the oxidation of methanol by alcohol oxidase. Not only H
2
O
2
generated intracellularly but also H
2
O
2
added extracellularly was effectively destroyed by the catalase-negative mutant. From the rate of H
2
O
2
consumption during growth in chemostat cultures on mixtures of glucose and H
2
O
2
, it appeared that the mutant was capable of decomposing H
2
O
2
at a rate as high as 8 mmol · g of cells
−1
· h
−1
. Glutathione peroxidase (EC 1.11.1.9) was absent under all growth conditions. However, cytochrome
c
peroxidase (CCP; EC 1.11.1.5) increased to very high levels in cells which decomposed H
2
O
2
. When wild-type
H. polymorpha
was grown on mixtures of glucose and methanol, the CCP level was independent of the rate of methanol utilization, whereas the level of catalase increased with increasing amounts of methanol in the substrate feed. Also, the wild type decomposed H
2
O
2
at a high rate when cells were grown on mixtures of glucose and H
2
O
2
. In this case, an increase of both CCP and catalase was observed. When
Saccharomyces cerevisiae
was grown on mixtures of glucose and H
2
O
2
, the level of catalase remained low, but CCP increased with increasing rates of H
2
O
2
utilization. From these observations and an analysis of cell yields under the various conditions, two conclusions can be drawn. (i) CCP is a key enzyme of H
2
O
2
detoxification in yeasts. (ii) Catalase can effectively compete with mitochondrial CCP for hydrogen peroxide only if hydrogen peroxide is generated at the site where catalase is located, namely in the peroxisomes.
Influence of unsaturated fatty acid membrane component on sensitivity of an Escherichia coli fatty acid auxotroph to conditions of nutrient depletion
Authors: Massa E M , López Vińals A , Farías R N
Published: January 2020

The unsaturated fatty acid auxotroph Escherichia coli AK7 was provided with either oleic acid (cis 18:1) or linolenic acid (cis 18:3) to vary the degree of unsaturation of cell membrane lipids. The susceptibility of oleic acid- and linolenic acid-grown cells to starvation at 37 degrees C in 154 mM NaCl was compared following the decline in the number of CFU by plating the cells on agar medium. The decline in CFU was faster for linolenic acid-than for oleic acid-grown cells, but it was not indicative of cell death, since culturable CFU was recovered after respirable substrate was added to the starved cell suspension. Cell envelope microviscosity (determined by fluorescence polarization) of oleic acid- and linolenic acid-grown cells was equal in the presence of a respirable substrate, but in its absence the microviscosity of linolenic acid-grown cells was lower than that of oleic acid-grown cells. The results suggest that cell envelope microviscosity is an important factor in determining the sensitivity of E. coli to conditions of nutrient depletion.
Resistance of some common fungi to gamma irradiation
Authors: Saleh Y G , Mayo M S , Ahearn D G
Published: January 2020

Ten species of fungi representing the genera Alternaria, Aspergillus, Caldosporium, Curvularia, Fusarium, and Penicillium were examined for their relative resistance to gamma irradiation from a 137Cs source. Inactivation doses for dematiaceous fungi in agar medium ranged from 0.6 to greater than 1.7 megarads, whereas those for moniliaceous fungi were less than 0.3 megarad. D10 values (the dose required to reduce the inoculum by 1 log) for Curvularia geniculata (greater than 0.29 megarad) exceeded those for control spores of Bacillus pumilus (0.15 megarad).
Plasmid Frequency Fluctuations in Bacterial Populations from Chemically Stressed Soil Communities
Authors: Wickham Gene S. , Atlas Ronald M.
Published: January 2020

The frequency of plasmids in chemically stressed bacterial populations was investigated by individually adding various concentration of kanamycin, ampicillin, and mercuric chloride to soil samples. Viable bacterial populations were enumerated, soil respiration was monitored for up to 6 weeks as an indicator of physiological stress, and bacterial isolates from stressed and control soils were screened for the presence of plasmids. Low levels of the chemical stress factors did not for the most part significantly alter population viability, soil respiration, or plasmid frequency. Exposure to high stress levels of mercury and ampicillin, however, resulted in altered numbers of viable organisms, soil respiration, and plasmid frequency. Plasmid frequency increased in response to ampicillin exposure but was not significantly changed after exposure to kanamycin. In mercuric chloride-stressed soils, there was a decrease in plasmid frequency despite an increase in overall mercury resistance of the isolates, suggesting that mercury resistance in these populations is largely, if not completely, chromosome encoded. Chemical stress did not cause an increase in plasmid-mediated multiple resistance. A genetic response (change in plasmid frequency) was not found unless a physiological (phenotypic) response (change in viable cells and respiratory activity) was also observed. The results indicate that a change in plasmid frequency is dependent on both the amount and type of chemical stress.
Transformations of Halogenated Aromatic Aldehydes by Metabolically Stable Anaerobic Enrichment Cultures
Authors: Neilson Alasdair H. , Allard Ann-Sofie , Hynning Per-Åke , Remberger Mikael
Published: January 2020

Metabolically stable enrichment cultures of anaerobic bacteria obtained by elective enrichment of sediment samples from the Baltic Sea and Gulf of Bothnia have been used to study the oxidation and reduction of the aldehyde group of various halogenated aromatic aldehydes. During the transformation of 5- and 6-chlorovanillin, 6-bromovanillin, 3-chloro-4-hydroxybenzaldehyde, 3,5-dichloro-4-hydroxybenzaldehyde, and 3,5-dibromo-4-hydroxybenzaldehyde, it was shown that synthesis of the corresponding carboxylic acids, which were the principal metabolites, was invariably accompanied by partial reduction of the aldehyde to a hydroxymethyl group in yields of between 3 and 30%. Complete reduction to a methyl group was observed with some of the halogenated vanillins, but to an extremely limited extent with the halogenated 4-hydroxybenzaldehydes. One consortium produced both the hydroxymethyl and methyl compounds from both 5- and 6-chlorovanillin: it was therefore assumed that the methyl compound was the ultimate reduction product. On the basis of the kinetics of formation of the metabolites, it was concluded that the oxidation and reduction reactions were mechanistically related. In addition to these oxidations and reductions, dehalogenation was observed with one of the consortia. In contrast to the transformations of 5- and 6-chlorovanillin, which produced chlorinated methylcatechols, the corresponding compounds were not observed with 5- and 6-bromovanillin: the former was debrominated, forming 4-methylcatechol, whereas the latter produced 6-bromovanillyl alcohol without demethylation. Similarly, although 3-chloro-4-hydroxybenzaldehyde formed the chlorinated carboxylic acid and the benzyl alcohol, the 3-bromo compound was debrominated with formation of 4-hydroxybenzoic acid and, ultimately, phenol. On prolonged incubation, the halogenated carboxylic acids were generally decarboxylated, so that the final products from these substrates were halogenated catechols or phenols. Reductive processes of the type revealed in this study might therefore plausibly occur in the environment during anaerobic transformation of halogenated aromatic aldehydes containing hydroxyl and/or methoxyl groups.
Monoclonal Antibodies to the Cell-Wall-Associated Proteinase of
Lactococcus lactis
subsp.
cremoris
Wg2
Authors: Laan Harry , Smid Eddy J. , de Leij Loe , Schwander Edwin , Konings Wil N.
Published: January 2020

Twelve monoclonal antibodies directed to the cell-wall-associated proteinase of
Lactococcus lactis
subsp.
cremoris
Wg2 were isolated after immunization of BALB/c mice with a partially purified preparation of the proteinase. The monoclonal antibodies reacted with the 126-kilodalton proteinase band in a Western immunoblot. All but one of the monoclonal antibodies reacted with protein bands with a molecular weight below 126,000, possibly degradation products of the proteinase. The monoclonal antibodies could be divided into six groups according to their different reactions with the proteinase degradation products in the Western blot. Different groups of monoclonal antibodies reacted with different components of the
L. lactis
subsp.
cremoris
Wg2 proteinase. Crossed immunoelectrophoresis showed that monoclonal antibody groups I, II, and III react with proteinase component A and that groups IV, V, and VI react with proteinase component B. The isolated monoclonal antibodies cross-reacted with the proteinases of other
L. lactis
subspecies. Monoclonal antibodies of group IV cross-reacted with proteinase component C of other
L. lactis
subsp.
cremoris
strains. The molecular weight of the proteinase attached to the cells of
L. lactis
subsp.
cremoris
Wg2 was 200,000, which is different from the previously reported values. This could be analyzed by immunodetection of the proteinase on a Western blot. This value corresponds to the molecular weight calculated from the amino acid sequence of the cloned
L. lactis
subsp.
cremoris
Wg2 proteinase gene.
Study of Vibrio anguillarum strains from different sources with emphasis on ecological and pathobiological properties
Authors: Larsen J L , Rasmussen H B , Dalsgaard I
Published: January 2020

A total of 317 Vibrio anguillarum strains were isolated from water, sediment, and diseased as well as healthy rainbow trout at a Danish mariculture farm and from feral fish caught close to the farm. All strains were examined serologically. Ten sera permitted determination of the O group in 66.7% of the strains from diseased rainbow trout. Furthermore, the O group could be determined in 45.1 to 65.4% of the strains from mucus, gills, and intestinal contents of healthy rainbow trout, while only 22.2 to 28.8% of the isolates from water, sediment, and gills or mucus of feral fish were groupable. Serogroup O1 and to some extent O2 appeared to be associated with trout. Strains from these serogroups were selected for analyses of hemagglutinating activity and surface hydrophobicity. Serogroup O1 comprised hemagglutinating as well as nonhemagglutinating strains; from cases of vibriosis, all O1 strains were nonhemagglutinating. The strains belonging to serogroup O2 were generally hemagglutinating. Examinations of surface hydrophobicity by salt aggregation and hydrophobic interaction chromatography suggested that the O1 strains were more hydrophobic than the O2 strains. In pathogenicity tests, O1 strains isolated from gills and mucus of healthy rainbow trout killed all trout in the test groups. A strain from the intestinal contents of healthy rainbow trout did not produce significant mortality. This strain could, however, be frequently reisolated from the pronephros of fish in the test group concerned. After challenge with strains from eel mucus and seawater, mortality was not produced, and furthermore, these strains could not be reisolated from the pronephros.
Microbiologically Catalyzed Enantio- and Diastereoselective Oxidation of Chrysanthemol Stereoisomers to Chrysanthemic Acids
Authors: Miski Mahmut , Davis Patrick J.
Published: January 2020

The diastereo- and enantioselective microbial oxidation of a mixture of racemic
cis/trans
-chrysanthemols to the corresponding stereoisomeric chrysanthemic acids by
Aspergillus
species is described. Of the three microorganisms which were found capable of oxidizing racemic
cis/trans
-chrysanthemols,
A. ochraceus
ATCC 18500 showed complete enantioselectivity for (+)-stereoisomers [(+)-
trans
-chrysanthemol and (+)-
cis
-chrysanthemol), whereas
A. flavipes
ATCC 1030 and ATCC 11013 showed complete enantioselectivity for the (+)-
cis
-chrysanthemol but a time-dependent enantioselectivity during oxidation of
trans
-chrysanthemol [oxidation of (+)-
trans
-chrysanthemol prior to (−)-
trans
-chrysanthemol]. The diastereoselectivity of all three microorganisms was time dependent, in that the
trans
-stereoisomers were oxidized prior to the
cis
-isomers.
Bacillus subtilis
β-1, 4-Endoglucanase Products from Intact and Truncated Genes Are Secreted into the Extracellular Medium by
Escherichia coli
Authors: Lo Amy C. , MacKay Ron M. , Seligy Vern L. , Willick Gordon E.
Published: January 2020

We compared the secretion of a
Bacillus subtilis
endo-β-1,4-glucanase (EC 3.2.1.4) in
B. subtilis
and of the product from the cloned gene (pC6.3) expressed in
Escherichia coli.
The cloned enzyme has been isolated previously as the 52.2-kilodalton (kDa) species predicted from the gene sequence (R. M. MacKay, A. Lo, G. Willick, M. Zuker, S. Baird, M. Dove, F. Moranelli, and V. Seligy, Nucleic Acids Res., 14:9159-9170, 1986); this 52.2-kDa species is then converted to an active 35.8-kDa species. The 35.8-kDa species has a segment removed from the COOH terminus. Endoglucanase products were identified by use of an antibody directed to the 35.8-kDa enzyme. Time course studies of the secretion in
B. subtilis
showed that the enzyme was first secreted as a 52.2-kDa proenzyme. This was cleaved progressively to a product of about 32 kDa. Time course analysis of the expression of the cloned product from pC6.3 in
E. coli
showed that about 70% of the endoglucanase activity was found extracellularly. Analysis of active products from three deletion clones showed that the expression pattern of the endoglucanase was not affected by removal of the transcription termination signal and that neither expression nor secretion was substantially altered by removal of a region coding for up to 163 residues of the carboxyl terminus.
Production of α-Amylase by the Ruminal Anaerobic Fungus
Neocallimastix frontalis
Authors: Mountfort Douglas O. , Asher Rodney A.
Published: January 2020

α-Amylase production was examined in the ruminal anaerobic fungus
Neocallimastix frontalis
. The enzyme was released mainly into the culture fluid and had temperature and pH optima of 55°C and 5.5, respectively, and the apparent
K

m

for starch was 0.8 mg ml
−1
. The products of α-amylase action were mainly maltotriose, maltotetraose, and longer-chain oligosaccharides. No activity of the enzyme was observed towards these compounds or pullulan, but activity on amylose was similar to starch. Evidence for the endo action of α-amylase was also obtained from experiments which showed that the reduction in iodine-staining capacity and release in reducing power by action on amylose was similar to that for commercial α-amylase. Activities of α-amylase up to 4.4 U ml
−1
(1 U represents 1 μmol of glucose equivalents released per min) were obtained for cultures grown on 2.5 mg of starch ml
−1
in shaken cultures. No growth occurred in unshaken cultures. With elevated concentrations of starch (>2.5 mg ml
−1
), α-amylase production declined and glucose accumulated in the cultures. Addition of glucose to cultures grown on low levels of starch, in which little glucose accumulated, suppressed α-amylase production, and in bisubstrate growth studies, active production of the enzyme only occurred during growth on starch after glucose had been preferentially utilized. When cellulose, cellobiose, glucose, xylan, and xylose were tested as growth substrates for the production of α-amylase (initial concentration, 2.5 mg ml
−1
), they were found to be less effective than starch, but maltose was almost as effective. The fungal α-amylase was found to be stable at 60°C in the presence of low concentrations of starch (≤5%), suggesting that it may be suitable for industrial application.
Classification and distribution of large intestinal bacteria in nonhibernating and hibernating leopard frogs (Rana pipiens)
Authors: Banas J A , Loesche W J , Nace G W
Published: January 2020

The large intestinal flora of the leopard frog, Rana pipiens, was examined to determine whether differences existed between the nonhibernating and hibernating states of the animal and to determine the relative concentrations and proportions of potential frog pathogens. Hibernators had a logarithmic decrease of bacteria per milligram of intestine averaging one, and significantly greater proportions of facultative bacteria and psychrophiles relative to nonhibernators. The predominant anaerobic bacteria were gram-positive Clostridium species and gram-negative Bacteroides and Fusobacterium species. The predominant facultative bacteria were enterobacteria in nonhibernators but Pseudomonas species in hibernators. Many species of Pseudomonas are pathogenic for frogs, and thus the intestinal flora in hibernators may be a potential source of infectious disease.
Toxicity of Bacillus sphaericus crystal toxin to adult mosquitoes
Authors: Stray J E , Klowden M J , Hurlbert R E
Published: January 2020

Adult Culex quinquefasciatus mosquitoes were killed by alkaline-solubilized Bacillus sphaericus toxin when it was introduced by enema into the midgut of the insect but not when it was administered orally. Adult Aedes aegypti mosquitoes were not affected by the toxin.