bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation of 1,2-dichlorobenzene by a Pseudomonas sp
Authors: Haigler B E , Nishino S F , Spain J C
Published: January 2020

A Pseudomonas sp. that was capable of growth on 1,2-dichlorobenzene (o-DCB) or chlorobenzene as a sole source of carbon and energy was isolated by selective enrichment from activated sludge. The initial steps involved in the degradation of o-DCB were investigated by isolation of metabolites, respirometry, and assay of enzymes in cell extracts. Extracts of o-DCB-grown cells converted radiolabeled o-DCB to 3,4-dichloro-cis-1,2-dihydroxycyclohexa-3,5-diene (o-DCB dihydrodiol). 3,4-Dichlorocatechol and o-DCB dihydrodiol accumulated in culture fluids of cells exposed to o-DCB. The results suggest that o-DCB is initially converted by a dioxygenase to a dihydrodiol, which is converted to 3,4-dichlorocatechol by an NAD+-dependent dehydrogenase. Ring cleavage of 3,4-dichlorocatechol is by a catechol 1,2-oxygenase to form 2,3-dichloro-cis,cis-muconate. Preliminary results indicate that chloride is eliminated during subsequent lactonization of the 2,3-dichloro-cis,cis-muconate, followed by hydrolysis to form 5-chloromaleylacetic acid.
Production of Biodispersan by
Acinetobacter calcoaceticus
A2
Authors: Rosenberg E. , Rubinovitz C. , Gottlieb A. , Rosenhak S. , Ron E. Z.
Published: January 2020

Bacterial strains A2 and HE5, isolated by enrichment culture techniques, were shown to produce extracellular, nondialyzable materials which disperse limestone powders in water. These materials are referred to as biodispersans. Strains A2 and HE5 were classified as
Acinetobacter calcoaceticus
by physiological and genetic tests. An assay for limestone-dispersing activity was developed which is based on the settling time of a standard 10% limestone-in-water mixture. The assay was proportional to biodispersan concentration between 40 and 100 μg/ml. Dispersion was optimum between pH 9 and 12. Phosphate (2 mM) and magnesium (8 mM) ions caused a 50% inhibition of activity. An optimized medium for the production of biodispersan was developed with ethanol as the substrate. Biodispersan was produced only after the bacteria completed their exponential growth phase and continued during the stationary phase, reaching over 4 g of crude biodispersan per liter.
Predictive model of conjugative plasmid transfer in the rhizosphere and phyllosphere
Authors: Knudsen G R , Walter M V , Porteous L A , Prince V J , Armstrong J L , Seidler R J
Published: January 2020

A computer simulation model was used to predict the dynamics of survival and conjugation of Pseudomonas cepacia (carrying the transmissible recombinant plasmid R388:Tn1721) with a nonrecombinant recipient strain in simple rhizosphere and phyllosphere microcosms. Plasmid transfer rates were derived for a mass action model, and donor and recipient survival were modeled as exponential growth and decay processes or both. Rate parameters were derived from laboratory studies in which donor and recipient strains were incubated in test tubes with a peat-vermiculite solution or on excised radish or bean leaves in petri dishes. The model predicted donor, recipient, and transconjugant populations in hourly time steps. It was tested in a microcosm planted with radish seeds and inoculated with donor and recipient strains and on leaf surfaces of radish and bean plants also growing in microcosms. Bacteria were periodically enumerated on selective media over 7 to 14 days. When donor and recipient populations were 10(6) to 10(8) CFU/g (wet weight) of plant or soil, transconjugant populations of about 10(1) to 10(4) were observed after 1 day. An initial rapid increase and a subsequent decline in numbers of transconjugants in the rhizosphere and on leaf surfaces were correctly predicted.
Thermal inactivation of Listeria monocytogenes within bovine milk phagocytes
Authors: Bunning V K , Donnelly C W , Peeler J T , Briggs E H , Bradshaw J G , Crawford R G , Beliveau C M , Tierney J T
Published: January 2020

Thermal resistance of intracellular and freely suspended Listeria monocytogenes that was associated with a milkborne outbreak of listeriosis was studied by using the sealed tube and slug flow heat exchanger methods. Test temperatures for the former method were 57.8, 62.8, 66.1, and 68.9 degrees C (136, 145, 151, and 156 degrees F, respectively); whereas those for the latter method were 66.1, 68.9, 71.7, and 74.4 degrees C (151, 156, 161, and 166 degrees F, respectively). The heating menstruum was sterile, whole milk. The intracellular inoculum was generated from an in vitro phagocytosis reaction by using endotoxin-induced bovine milk phagocytes. The phagocyte population consisted of 88% neutrophils, 8% macrophages, and 4% lymphocytes. Neutrophils harbored the majority of intracellular L. monocytogenes. The mean level of infectivity in the phagocyte population was 43%, and there were 26.1 +/- 19.3 bacteria per cell (10(4) viable cells per ml of test milk). Initial bacterial counts for the freely suspended and intracellular experiments (the latter was based on a sonically disrupted sample) were 10(6) L. monocytogenes cells per ml. Heat-stressed bacteria were recovered by direct plating in parallel with recovery from an enrichment broth; both methods gave comparable results. The predicted D62.8 degrees C (145 degrees F) value for intracellular sealed tube studies was 53.8 s (ZD = 5.6 degrees C [10.0 degrees F]), indicating a safe 33.4 D margin of inactivation for vat pasteurization (62.8 degrees C for 30 min).(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of Phosphate on the Corrosion of Carbon Steel and on the Composition of Corrosion Products in Two-Stage Continuous Cultures of
Desulfovibrio desulfuricans
Authors: Weimer Paul J. , Van Kavelaar Margaret J. , Michel Charles B. , Ng Thomas K.
Published: January 2020

A field isolate of
Desulfovibrio desulfuricans
was grown in defined medium in a two-stage continuous culture apparatus with different concentrations of phosphate in the feed medium. The first state (V1) was operated as a conventional chemostat (
D
= 0.045 h
−1
) that was limited in energy source (lactate) or phosphate. The second stage (V2) received effluent from V1 but no additional nutrients, and contained a healthy population of transiently starved or resting cells. An increase in the concentration of phosphate in the medium fed to V1 resulted in increased corrosion rates of carbon steel in both V1 and V2. Despite the more rapid corrosion observed in growing cultures relative to that in resting cultures, corrosion products that were isolated under strictly anaerobic conditions from the two culture modes had similar bulk compositions which varied with the phosphate content of the medium. Crystalline mackinawite (Fe
9
S
8
), vivianite [Fe
3
(PO
4
)
2
· 8H
2
O], and goethite [FeO(OH)] were detected in amounts which varied with the culture conditions. Chemical analyses indicated that the S in the corrosion product was almost exclusively in the form of sulfides, while the P was present both as phosphate and as unidentified components, possibly reduced P species. Some differential localization of S and P was observed in intact corrosion products. Cells from lactate-limited, but not from phosphate-limited, cultures contained intracellular granules that were enriched in P and Fe. The results are discussed in terms of several proposed mechanisms of microbiologically influenced corrosion.
Isolation of a DNA Probe for
Lactobacillus curvatus
Authors: Petrick Hendrik A. R. , Ambrosio Riccardo E. , Holzapfel Wilhelm H.
Published: January 2020

A genomic library of
Lactobacillus curvatus
DSM 20019 was constructed in bacteriophage λ gt11. A 1.2-kilobase DNA probe specific for
L. curvatus
was isolated from this library. When this probe was hybridized to DNA from
Lactobacillus
isolates from different sources classified by conventional techniques, differing degrees of hybridization were obtained. This could imply that these isolates may have been incorrectly classified.
Animal viruses, coliphages, and bacteria in aerosols and wastewater at a spray irrigation site
Authors: Brenner K P , Scarpino P V , Clark C S
Published: January 2020

Aerosol samples collected at the Muskegon County Wastewater Management System Number 1 spray irrigation site in Michigan by using the Army prototype XM2 Biological Sampler/Collector were examined for the presence of animal viruses, coliphages, and bacteria. Air samples, collected in Earle lactalbumen hydrolysate, and wastewater samples were filtered through a 0.45- and 1.2-micron membrane filter sandwich, pretreated with 10% beef extract (pH 7.0), and assayed for animal viruses by the plaque method on Buffalo green monkey kidney cells. Untreated air and wastewater samples were assayed for coliphages by the soft agar overlay method with three Escherichia coli hosts (ATCC 13706, 15597, and 11303) and for bacteria by the heterotrophic plate count method. Filtered air samples were assayed for coliphages by the most-probable-number method with the same three hosts. Although no animal viruses were detected in the aerosol samples, coliphages and bacteria were recovered. E. coli ATCC 13706 coliphage were recovered more often and in greater numbers than either of the other two types of coliphages. Concentrations of animal viruses, coliphages, and bacteria detected in the raw influent decreased as the wastewater was aerated and stored in the lagoons. No animal viruses were detected in the wastewater at the pump station just before distribution to the spray irrigation rigs. The most-probable-number method was more sensitive and consistent than the overlay procedure in detecting low levels of coliphages in air samples.
Genetic transformation in Lactobacillus sp. strain 100-33 of the capacity to colonize the nonsecreting gastric epithelium in mice
Authors: McCarthy D M , Lin J H , Rinckel L A , Savage D C
Published: January 2020

Lactobacillus isolates able to colonize the surfaces of the nonsecreting epithelia in the stomachs of monoassociated ex-germfree mice were derived from Lactobacillus acidophilus 100-33. Strain 100-33 was originally isolated from pig feces and is unable to colonize the murine gastric epithelium. In experiments involving attempts genetically to transform the capacity to colonize the epithelium, cells of strain 100-33 were treated with muralytic enzymes and mixed with polyethylene glycol and genomic or plasmid DNA extracted from Lactobacillus fermentum RI. Strain RI was originally isolated from a conventional mouse and has the capacity to colonize the nonsecreting gastric epithelium. The mixtures containing cells, polyethylene glycol, and DNA were plated on a regeneration medium. After overnight incubation, the cells were washed from the plates and introduced by gastric gavage into germfree mice. Only mice that received regenerated 100-33 cells previously mixed with genomic DNA from strain RI had layers of gram-positive bacteria on the keratinized epithelia of their stomachs. Six isolates cultured from the washed gastric tissues of these animals were characterized. When a culture of each or a pool of cultures of the six were orally administered to germfree mice, layers of gram-positive bacterial cells were visible on the keratinized gastric epithelia of the animals within 1 to 3 weeks. Cells of all six, but not of strain 100-33, reacted with antibody made in rabbits to L. fermentum RI cells, as determined by an enzyme-linked immunosorbent assay. Nevertheless, all six had fermentation profiles identical to that of strain 100-33.(ABSTRACT TRUNCATED AT 250 WORDS)
Induction of Symbiotically Defective Auxotrophic Mutants of
Rhizobium fredii
HH303 by Transposon Mutagenesis
Authors: Kim Choong-Hyun , Kuykendall L. David , Shah Ketan S. , Keister Donald L.
Published: January 2020

Symbiotically defective auxotrophic mutants were isolated by transposon Tn
5
mutagenesis of
Rhizobium fredii
HH303, a fast-growing microsymbiont of North American commercial soybean cultivars such as
Glycine max
cv. Williams. Three different Tn
5
-carrying suicide vectors, pBLK1-2, pSUP1011, and pGS9, were used for mutagenesis with transposition frequencies of 4 × 10
−5
, 3 × 10
−6
, and 1 × 10
−6
, respectively, while the frequency of background mutation resistant to 500 μg of kanamycin per ml was 1 × 10
−8
. From 2,600 Tn
5
-induced mutants, 14 auxotrophic mutants were isolated and classified in seven groups including adenosine (four), aspartate (two), cysteine or methionine (two), isoleucine and valine (two), nicotinic acid (one), pantothenic acid (one), and uracil (two). All the auxotrophs induced nodulation on soybean, but the symbiotic effectiveness of each mutant was different. Three auxotrophs (two cysteine or methionine and one pantothenic acid) formed effective nodules similar to those of the wild type. Three auxotrophs (one nicotinic acid and two aspartate) produced mature nodules like those of the wild type, but the nodules lacked the characteristic pink color inside and were unable to fix nitrogen. Four auxotrophs (two adenosine and two uracil) induced pseudonodules unable to fix nitrogen. The other four auxotrophs repeatedly induced both effective and ineffective nodules, but bacteroids isolated from the effective nodules were prototrophic revertants. The symbiotic phenotype and the degree of effectiveness of the auxotrophic mutants varied with the type of mutation.
Metabolism of 2,6-dimethylnaphthalene by flavobacteria
Authors: Barnsley E A
Published: January 2020

Flavobacteria that were able to grow on 2,6-dimethylnaphthalene (2,6-DMN) were isolated from soil. Most were able to oxidize a broad range of aromatic hydrocarbons after growth on 2,6-DMN at rates comparable to that of the oxidation of 2,6-DMN itself. One small group was neither able to grow on naphthalene nor able to oxidize this compound after growth on 2,6-DMN, but metabolized 2,6-DMN by a pathway which converged with that previously described for naphthalene metabolism in pseudomonads. These organisms could also grow on salicylate or methylsalicylate, and in so doing, early enzymes for 2,6-DMN metabolism were induced.
Fermentative degradation of nonionic surfactants and polyethylene glycol by enrichment cultures and by pure cultures of homoacetogenic and propionate-forming bacteria
Authors: Wagener S , Schink B
Published: January 2020

Linear alkyl ethoxylates (polyethylene glycol alkyl ethers) were fermented completely to methane and CO2 in enrichment cultures inoculated with anoxic sewage sludge. Long-chain fatty acids were released as intermediates. No degradation was found with polypropylene glycol and polypropylene glycol-containing surfactants. Two types of primary ethoxylate-degrading bacteria were isolated and characterized. Both degraded polyethylene glycols with molecular weights of 1,000 completely. Strain KoB35 fermented polyethylene glycol, ethoxyethanol, and lactate to acetate and propionate and was assigned to the described species Pelobacter propionicus. Strain KoB58 converted polyethylene glycol and many other substrates to acetate only and was assigned to the genus Acetobacterium. The pathways of anaerobic degradation of nonionic surfactants are discussed with respect to their limitations and the various groups of bacteria involved.
Changes in Endoglucanase Patterns during Growth of
Thermomonospora curvata
on Cellulose
Authors: Lupo Davis , Stutzenberger Fred
Published: January 2020

The endoglucanases of the thermophilic actinomycete
Thermomonospora curvata
were characterized. Early-exponential-phase culture fluid contained at least three endoglucanases, with molecular weights of 23,000, 46,000, and 146,000 and

K
m

values of 1.54, 3.60, and 1.32% carboxymethyl cellulose, respectively. The stationary-phase pattern was altered to include three enzymes with molecular weights of 52,000, 114,000, and 106,000, with respective

K
m

values of 1.77, 8.30, and 1.91%.
Influence of pH on microbial hydrogen metabolism in diverse sedimentary ecosystems
Authors: Goodwin S , Conrad R , Zeikus J G
Published: January 2020

Hydrogen transformation kinetic parameters were measured in sediments from anaerobic systems covering a wide range of environmental pH values to assess the influence of pH on hydrogen metabolism. The concentrations of dissolved hydrogen were measured and hydrogen transformation kinetics of the sediments were monitored in the laboratory by monitoring hydrogen consumption progress curves. The hydrogen turnover rate constants (kt) decreased directly as a function of decreasing sediment pH, and the maximum hydrogen uptake velocities (Vmax) varied as a function of pH within each of the trophic states. Conversely, the half-saturation concentrations (Km) were independent of pH. The steady-state hydrogen concentrations were at least 2 orders of magnitude lower than the half-saturation constants for hydrogen uptake. Dissolved hydrogen concentrations were at least fivefold higher in sediments from eutrophic systems than from oligotrophic and dystrophic systems. The rates of hydrogen production determined from the assumption of steady state decreased with sediment pH. These data indicate that progressively lower pH values inhibit microbial hydrogen-producing and -consuming processes within sedimentary ecosystems.
Resistance of
Thermus
spp. to Potassium Tellurite
Authors: Chiong Mario , Barra Ricardo , González Enrique , Vásquez Claudio
Published: January 2020

Two members of the genus
Thermus
were examined for their resistance to toxic inorganic compounds. They both proved to be fairly resistant to tellurite and selenite and to many other heavy metal salts. Cell extracts of
Thermus thermophilus
HB8 and of
T. flavus
AT-62 catalyze the reduction of K
2
TeO
3
in a reaction which is dependent on NADH oxidation.
Aggregated and Free Bacteria as Food Sources for Heterotrophic Microflagellates
Authors: Sibbald Mary Jo , Albright Lawrence J.
Published: January 2020

Laboratory evidence for the selective grazing of aggregated bacteria by a
Bodo
sp. and free bacteria by a
Paraphysomonas
sp. is presented. The relevance of different microflagellate feeding mechanisms with respect to prey distribution in the natural environment is discussed.
Evaluation of four methods for enumeration of Vibrio parahaemolyticus
Authors: DePaola A , Hopkins L H , McPhearson R M
Published: January 2020

Two membrane filter (MF) and two most-probable-number methods for enumerating Vibrio parahaemolyticus were compared. The MF methods used elevated-temperature incubations (41 and 42 degrees C) and were more specific than the most-probable-number methods (conducted at 35 degrees C). The MF method with a hydrophobic grid and a repair step was most effective.
Enumeration of Thermophilic Heterotrophs in Geothermally Heated Soils from Mount Erebus, Ross Island, Antarctica
Authors: Hudson J. Andrew , Daniel Roy M.
Published: January 2020

Soil samples with temperatures up to 64°C were collected from Mount Erebus, an active volcano located on Ross Island, Antarctica. Acridine orange direct counts and most probable number counts of soil samples stored at 4°C for 2 months showed a wide variation in the number of thermophilic microorganisms in different soils. Organisms similar to
Clostridium thermohydrosulfuricum, Bacillus schlegelii
, and
Bacillus acidocaldarius
, as well as neutrophilic
Bacillus
strains, were isolated.
Nutritional requirements of Methanomicrobium mobile
Authors: Tanner R S , Wolfe R S
Published: January 2020

A defined medium was developed for Methanomicrobium mobile BP. M. mobile required acetate for growth; the optimal concentration was 30 mM. Other requirements and their optimal concentrations included isobutyrate (0.65 mM), isovalerate (0.73 mM), and 2-methylbutyrate (1.5 mM). The appropriate branched-chain amino acids did not substitute for these branched-chain fatty acids. M. mobile required tryptophan at an optimal concentration of 24 microM. Indole substituted for tryptophan, but the possible precursor compounds shikimic acid and anthranilic acid and the degradation compound skatole did not. Vitamin requirements and their optimal concentrations included pyridoxine (0.49 microM), thiamine (0.15 microM), biotin (0.04 microM), and vitamin B12 (0.04 microM); p-aminobenzoic acid (0.18 microM) was required for optimal growth, but folic acid did not replace p-aminobenzoic acid. M. mobile required an unidentified growth factor found in ruminal fluid or extracts of Methanobacterium thermoautotrophicum for growth. M. mobile has a complex nutrition compared with that of other methanogens, but not an unusual nutrition in the context of organisms from the ruminal ecosystem.
Chemotaxis by
Pseudomonas syringae
pv.
tomato
Authors: Cuppels Diane A.
Published: January 2020

Optimal laboratory conditions for studying chemotaxis by
Pseudomonas syringae
pv.
tomato
were determined by using the Adler capillary tube assay. Although they are not an absolute requirement for chemotaxis, the presence of 0.1 mM EDTA and 1 mM MgCl
2
in the chemotaxis buffer (10 mM potassium phosphate [pH 7.2]) significantly enhanced the response to attractant. The addition of mannitol as an energy source had little effect. The optimal temperature for chemotaxis was 23°C, which is 5°C below the optimal growth temperature for this pathogen. The best response occurred when the bacteria were exposed to attractant for 60 min at a concentration of approximately 5 × 10
6
CFU/ml.
P. syringae
pv.
tomato
was strongly attracted to citric and malic acids, which are the predominant organic acids in tomato fruit. With the exception of asparagine, the major amino acids of tomatoes were weak to moderate attractants. Glucose and fructose, which account for approximately 47% of tomato dry matter, also elicited poor responses. In assays with tomato intercellular fluid and leaf surface water, the bacterial speck pathogen could not chemotactically distinguish between a resistant and a susceptible cultivar of tomato.
Evidence for a cytoplasmic pathway of oxalate biosynthesis in Aspergillus niger
Authors: Kubicek C P , Schreferl-Kunar G , Wöhrer W , Röhr M
Published: January 2020

Oxalate accumulation of up to 8 g/liter was induced in Aspergillus niger by shifting the pH from 6 to 8. This required the presence of Pi and a nitrogen source and was inhibited by the protein synthesis inhibitor cycloheximide. Exogenously added 14CO2 was not incorporated into oxalate, but was incorporated into acetate and malate, thus indicating the biosynthesis of oxalate by hydrolytic cleavage of oxaloacetate. Inhibition of mitochondrial citrate metabolism by fluorocitrate did not significantly decrease the oxalate yield. The putative enzyme that was responsible for this was oxaloacetate hydrolase (EC 3.7.1.1), which was induced de novo during the pH shift. Subcellular fractionation of oxalic acid-forming mycelia of A. niger showed that this enzyme is located in the cytoplasm of A. niger. The results are consistent with a cytoplasmic pathway of oxalate formation which does not involve the tricarboxylic acid cycle.
A Simple and Rapid Method for Genetic Transformation of Lactic Streptococci by Electroporation
Authors: Powell Ian B. , Achen Marc G. , Hillier Alan J. , Davidson Barrie E.
Published: January 2020

An electroporation procedure for the plasmid-mediated genetic transformation of intact cells of
Streptococcus cremoris
and
Streptococcus lactis
was performed. Ten different strains were transformed. The method was simple and rapid and yielded transformant colonies in 14 to 24 h. The method was optimized for
S. lactis
LM0230, and transformation frequencies of between 1 × 10
4
and 5 × 10
5
transformants per μg of purified plasmid (pMU1328) were achieved routinely. The optimized procedure involved lysozyme treatment of cells. Transformation of LM0230 occurred at comparable frequencies with pLS1 (4.4 kilobase pair [kbp]), pMU1328 (7.4 kbp), and pAMβ1 (26.5 kbp). Plasmid DNA isolated from transformants had not undergone detectable deletions or rearrangements. Transformation was possible with plasmid DNA which was religated after restriction endonuclease digestion. Phage DNA-dependent transfection of
S. lactis
LM0230 and
S. lactis
C6 was also achieved.
Adsorption of Lithocholic Acid to
Fusarium equiseti
M41 as an Essential Process in Its Conversion to Ursodeoxycholic Acid
Authors: Nihira Takuya , Nishino Toshiki , Maehara Masao , Kulprecha Songsri , Yoshida Toshiomi , Taguchi Hisaharu
Published: January 2020

Fusarium equiseti
M41 converts lithocholic acid to ursodeoxycholic acid. Adsorption of lithocholic acid particles to mycelia of
F. equiseti
M41 is essential in the conversion of lithocholic acid to ursodeoxycholic acid. Production of ursodeoxycholic acid was negligible when particles of lithocholic acid were absent. As the concentration of lithocholic acid particles increased, both the amount of mycelium-bound lithocholic acid and the production of ursodeoxycholic acid increased hyperbolically (
K
1/2
= 1.9 g/liter and
K

m
apparent

= 1.9 g/liter. A fluorescent lithocholic acid derivative was used to confirm that insoluble particles of lithocholic acid attached to the surface of the mycelia. The hydrophobic nature of this binding was estimated from the close relationship observed between the hydrophobicity of bile acids and their binding capacity to the mycelia. By repeated washing with 30% dimethyl sulfoxide, two binding modes of lithocholic acid were distinguished, i.e., surface binding (59% of bound lithocholic acid) and tight binding (41% of bound lithocholic acid). From the amount of tightly bound lithocholic acid, the intracellular concentration of lithocholic acid was calculated to be 1,433-fold higher than its saturating concentration in the reaction mixture, thus promoting effective conversion to ursodeoxycholic acid in the mycelia. Several lines of evidence indicated that glycoproteins of the cell wall participated in the binding of lithocholic acid.
Effects of three oxidizing biocides on Legionella pneumophila serogroup 1
Authors: Domingue E L , Tyndall R L , Mayberry W R , Pancorbo O C
Published: January 2020

A study was conducted to determine the bactericidal effects of ozone and hydrogen peroxide relative to that of free chlorine on Legionella pneumophila serogroup 1. In laboratory batch-type experiments, organisms seeded at various densities were exposed to different concentrations of these biocides in demand-free buffers. Bactericidal effects were measured by determining the ability of L. pneumophila to grow on buffered charcoal-yeast extract agar supplemented with alpha-ketoglutarate. Ozone was the most potent of the three biocides, with a greater than 99% kill of L. pneumophila occurring during a 5-min exposure to 0.10 to 0.30 micrograms of O3 per ml. The bactericidal action of O3 was not markedly affected by changes in pH or temperature. Concentrations of 0.30 and 0.40 micrograms of free chlorine per ml killed 99% of the L. pneumophila after 30- and 5-min exposures, respectively. A 30-min exposure to 1,000 micrograms of H2O2 per ml was required to effect a 99% reduction of the viable L. pneumophila population. However, no viable L. pneumophila could be detected after a 24-h exposure to 100 or 300 micrograms of H2O2 per ml. Attempts were made to correlate the biocidal effects of O3 and H2O2 with the oxidation of L. pneumophila fatty acids. These tests indicated that certain biocidal concentrations of O3 and H2O2 resulted in a loss or severe reduction of L. pneumophila unsaturated fatty acids.
Application of the Fluorescent-Antibody Technique for the Detection of
Sphaerotilus natans
in Activated Sludge
Authors: Howgrave-Graham Alan R. , Steyn Pieter L.
Published: January 2020

Sphaerotilus natans
, one of the most widely reported causes of bulking in activated sludge, can exist both within and outside of a sheath. It can easily be confused with similar activated sludge bacteria and thus can be overlooked when present in low numbers. Fluorescent antiserum was successfully prepared against the nonfilamentous form and was shown to be highly specific, showing no reaction with either pure cultures of similar filamentous bacteria or entirely unrelated organisms. It did, however, show a lack of strain specificity since it reacted with
S. natans
isolates from the Federal Republic of Germany and the United States and with filamentous bacteria in South African activated sludges. Fluorescent antibody is capable of penetrating the filaments of
S. natans
to stain the cells individually. The use of fluorescent antiserum in the identification of
S. natans
filaments obscured by activated sludge flocs and other suspended matter was simple since the cells stained brightly and could be observed through the less dense matter, while the use of other microscope techniques would be hampered by these obstructions. The use of fluorescent antibody will facilitate ecological studies of
S. natans
in activated sludge and other aqueous environments.
Virulence of Yersinia pseudotuberculosis isolated from pork and from the throats of swine
Authors: Shiozawa K , Hayashi M , Akiyama M , Nishina T , Nakatsugawa S , Fukushima H , Asakawa Y
Published: January 2020

Yersinia pseudotuberculosis was isolated from retail pork and from healthy swine throats. These wild-type strains and their representative cured isogenic strains were tested for the presence of plasmids and several virulence factors, and these characteristics were compared with those of virulent strains from humans. Two pork isolates (serotype IVB) and four swine isolates (serotypes IIB, IIC, III, and IVB) harbored a 42- to 48-megadalton plasmid which had similar fragmentation patterns resulting from digestion with restriction endonuclease. These six strains were lethal for mice via oral challenge and were positive in autoagglutination and calcium dependency tests. They also invaded HeLa cells and induced cytotoxicity. Histopathological examination and indirect fluorescent-antibody staining provided definite evidence of the pathogenicity of these strains when tissue sections from orally infected mice were used. The virulence factors of wild-type pork and swine isolates with the 42- to 48-megadalton plasmid were identical to those of two human isolates (serotypes IVB and VB). Hence, these pork and swine isolates should be considered potentially pathogenic for humans. The finding suggests that retail pork and swine may play an important role in the epidemiology of human infections caused by Y. pseudotuberculosis.
Microbial hydroxylation of quinoline in contaminated groundwater: evidence for incorporation of the oxygen atom of water
Authors: Pereira W E , Rostad C E , Leiker T J , Updegraff D M , Bennett J L
Published: January 2020

Studies conducted in an aquifer contaminated by creosote suggest that quinoline is converted to 2(1H)quinolinone by an indigenous consortium of microorganisms. Laboratory microbial experiments using H218O indicate that water is the source of the oxygen atom for this hydroxylation reaction under aerobic and anaerobic conditions.
Comparison between the adhesion to solid substrata of Streptococcus mitis and that of polystyrene particles
Authors: Uyen H M , van der Mei H C , Weerkamp A H , Busscher H J
Published: January 2020

The adhesion of Streptococcus mitis to solid substrata from phosphate suspensions with various ionic strengths was studied and compared with the adhesion of polystyrene particles. At all ionic strengths, the interfacial free energy of adhesion governed the relative number of bacteria or polystyrene particles adhering at equilibrium, except that in a low-ionic-strength buffer, adhesion occurred less frequently because of increased electrostatic repulsion. Large differences between bacterial and polystyrene particle adhesion were observed, as indicated by the ratio of bacteria to polystyrene particles adhering, which decreased from 30 to 4 with a change from low to high ionic strength.
Low-temperature stability of viruses in sludges
Authors: Berg G , Sullivan G , Venosa A D
Published: January 2020

Enteroviruses survived for up to 38 days without diminishing in numbers in extended-aeration sludges maintained at 5 degrees C. In oxidation ditch sludges similarly maintained, enteroviruses survived for up to 17 days without diminishing in numbers. The pHs of the sludges in this study were well inside the pH 6 to 8 corridor in which destruction of enteroviruses by the detergents and ammonia present in sludges reportedly does not occur. Unexplained, however, was the survival of large numbers of enteroviruses in sludges at pH 3.5, a pH at which some anionic detergents commonly present in sewage are rapidly virucidal. The long survival of enteroviruses in these sludges at 5 degrees C indicates that such sludges can probably be stored under refrigeration in the laboratory for extended periods while awaiting processing without suffering significant losses in enterovirus numbers.
Effect of Naturally Occurring
nif
Reiterations on Symbiotic Effectiveness in
Rhizobium phaseoli
Authors: Romero David , Singleton Paul W. , Segovia Lorenzo , Morett Enrique , Bohlool B. Ben , Palacios Rafael , Dávila Guillermo
Published: January 2020

Most naturally occurring strains of
Rhizobium phaseoli
possess reiteration of the
nif
genes. Three regions contain nitrogenase structural genes in strain CFN42. Two of these regions (a and b) have copies of
nifH, nifD
, and
nifK
, whereas the third region (c) contains only
nifH
. Strains containing mutations in either
nif
region a or
nif
region b had significantly diminished symbiotic effectiveness compared with the wild-type strain on the basis of nodule mass, total nitrogenase activity per plant, nitrogenase specific activity, total nitrogen in the shoot, and percentage of nitrogen. A strain containing mutations in both
nif
region a and
nif
region b was totally ineffective. These data indicate that both
nif
region a and
nif
region b are needed for full symbiotic effectiveness in
R. phaseoli.
Enzyme-Linked Immunosorbent Assays for the Specific and Sensitive Quantification of
Methanosarcina mazei
and
Methanobacterium bryantii
Authors: Kemp Heather A. , Archer David B. , Morgan Michael R. A.
Published: January 2020

Three microtitration plate enzyme-linked immunosorbent assays (ELISAs) have been developed: a competitive ELISA and a two-site (or indirect sandwich) ELISA for
Methanosarcina mazei
S6 and a two-site ELISA for
Methanobacterium bryantii
FR-2. The assays were sensitive, with limits of cell protein detection of 3 ng ml
−1
, 5 ng ml
−1
, and 50 ng ml
−1
, respectively, and showed good precision. The
M. mazei
assays used monoclonal antibodies and were entirely species specific, showing no cross-reaction with methanogens of other genera or with other species of the same genus. The
Methanobacterium bryantii
assay, which used two polyclonal antisera, showed only a slight cross-reaction with one other
Methanobacterium
species but no cross-reaction with methanogens of other genera. The use of the ELISAs for quantitative analysis of mixed cultures and of sewage sludge samples was investigated. Sludge diluted at 1:10
3
or more caused no significant interference in any of the three ELISAs. Various cultures of bacteria, methanogens, and nonmethanogens at a protein concentration of 50 μg ml
−1
showed no significant interference in the
M. mazei
competitive assay and the
Methanobacterium bryantii
two-site assay, although they did cause falsely low results in the
M. mazei
two-site assay.
Comparative Analysis of the Chemical Composition of Mixed and Pure Cultures of Green Algae and Their Decomposed Residues by
13
C Nuclear Magnetic Resonance Spectroscopy
Authors: Zelibor J. L. , Romankiw L. , Hatcher P. G. , Colwell R. R.
Published: January 2020

It is known that macromolecular organic matter in aquatic environments, i.e., humic substances, is highly aliphatic. These aliphatic macromolecules, predominantly paraffinic in structure, are prevalent in marine and lacustrine sediments and are believed to originate from algae or bacteria. A comparative study of mixed and pure cultures of green algae and their decomposed residues was performed by using solid-state
13
C nuclear magnetic resonance spectroscopy as the primary analytical method. Results obtained in this study confirm the presence of components that are chemically refractory and that are defined as alghumin and hydrolyzed alghumin. These were detected in heterogeneous, homogeneous, and axenic biomasses composed of several genera of Chlorophyta. Although the chemical composition of algal biomass varied with culture conditions, the chemical structure of the alghumin and hydrolyzed alghumin, demonstrated by
13
C nuclear magnetic resonance spectroscopy appeared to be constant for members of the Chlorophyta examined in this study. The alghumin was dominated by carbohydrate-carbon, with minor amounts of amide or carboxyl carbon and paraffinic carbon, the latter surviving strong hydrolysis by 6 N HCI (hydrolyzed alghumin). Bacterial decomposition of heterogeneous algal biomass labeled with
13
C was conducted under both aerobic and anaerobic conditions to determine chemical structure and stability of the refractory material. The refractory fraction ranged from 33% in aerobic to 44% in anaerobic cultures. The refractory fraction recovered from either aerobic or anaerobic degradation comprised 40% alghumin, which represented an enrichment by 10% relative to the proportion of alghumin derived from whole cells of algae. The paraffinic component in the hydrolyzed alghumin of whole algal cells was found to be 1.8% and increased to 5.1 and 6.9% after aerobic and anaerobic bacterial degradation, respectively. It is concluded that members of the Chlorophyta contain a common insoluble structure composed of paraffinic carbon that is resistant to chemical and bacterial degradation under conditions used in this study. The paraffinic structure is identical to those constituting humin of aquatic origin. Thus, alga-derived macromolecular compounds deposited in aquatic environments (alghumin) probably contribute to sedimentary humic substances.
Isolation of a New Polysaccharide-Digesting Bacterium from a Salt Marsh
Authors: Andrykovitch George , Marx Irene
Published: January 2020

A new marine bacterium that digested a variety of storage and structural polysaccharides, including agar, was isolated. Strain 2-40 is a nonfermentative gram-negative, polarly flagellated rod that sometimes grew as a filamentous helix and secreted a melaninlike pigment. Its characteristics conform to those of no previously described species.
Plasmid-associated transfer of tetracycline resistance in Bacteroides ruminicola
Authors: Flint H J , Thomson A M , Bisset J
Published: January 2020

Tetracycline resistance was transferred at frequencies between 10(-7) and 10(-6) per recipient cell in anaerobic matings between two strains of the strictly anaerobic rumen bacterium Bacteroides ruminicola. The donor strain, 223/M2/7, was a multiple-plasmid-bearing tetracycline-resistant strain from the ovine rumen, and the recipient, F101, was a rifampin-resistant mutant of B14, a bovine strain belonging to B. ruminicola subsp. brevis. Resistance transfer could occur in the presence of DNase, but not in dummy mating mixtures in which filtrate from a donor culture replaced donor cells. Acquisition of tetracycline resistance by the recipient was accompanied by the appearance of a 19.5-kilobase pair plasmid (designated pRRI4) which was homologous with a plasmid of similar size and restriction pattern present in the donor strain. A transconjugant (F115) carrying pRRI4 was also able to act as a donor of tetracycline resistance and plasmid DNA in matings with another recipient. Derivatives of F115 that had spontaneously lost tetracycline resistance lacked detectable plasmid DNA. It is concluded that pRRI4 mediated the transfer of tetracycline resistance. Transfer of resistance was not detectably enhanced by pregrowth of the donor in medium containing tetracycline. Transfer of tetracycline resistance was not detected from 223/M2/7 to a strain, 23 belonging to B. ruminicola subsp. ruminicola.
Selection of Ethanol-Tolerant Yeast Hybrids in pH-Regulated Continuous Culture
Authors: Jiménez Juan , Benítez Tahía
Published: January 2020

Hybrids between naturally occurring wine yeast strains and laboratory strains were formed as a method of increasing genetic variability to improve the ethanol tolerance of yeast strains. The hybrids were subjected to competition experiments under continuous culture controlled by pH with increasing ethanol concentrations over a wide range to select the fastest-growing strain at any concentration of ethanol. The continuous culture system was obtained by controlling the dilution rate of a chemostat connected to a pH-meter. The nutrient pump of the chemostat was switched on and off in response to the pH of the culture, which was thereby kept near a critical value (pH
c
). Under these conditions, when the medium was supplemented with ethanol, the ethanol concentration of the culture increased with each pulse of dilution. A hybrid strain was selected by this procedure that was more tolerant than any of the highly ethanol-tolerant wine yeast strains at any concentration of ethanol and was able to grow at up to 16% (vol/vol) ethanol. This improvement in ethanol tolerance led to an increase in both the ethanol production rate and the total amount of ethanol produced.
Interaction of Vesicular-Arbuscular Mycorrhizal Fungi with Erosion in an Oxisol
Authors: Habte M. , Fox R. L. , Aziz T. , El-Swaify S. A.
Published: January 2020

The development of vesicular-arbuscular mycorrhizal (VAM) symbiosis was monitored in
Leucaena leucocephala
grown in an Oxisol subjected to incremental simulated erosion. The density of VAM infective propagules in the soil diminished as the level of simulated erosion (removal of surface soil) was increased from 0 to 50 cm. The level of infection on
L. leucocephala
roots observed at harvest was not significantly influenced by simulated erosion unless removal of surface soil exceeded 25 cm. Inoculation of this soil and the uneroded soil with
Glomus aggregatum
enhanced the early onset of infection but did not significantly influence the level of infection observed at the time of harvest. Simulated erosion in excess of 7.5 cm of surface soil removal significantly delayed the development of VAM effectiveness monitored in terms of the P status of
L. leucocephala
subleaflets and also curtailed the level of maximum effectiveness observed. Decreases in VAM effectiveness were significantly correlated with decreases in soil chemical constituents. However, VAM effectiveness in a soil subjected to 30 cm of surface soil removal was not restored to a significant extent unless the soil was amended with P, even though other nutrients were restored to sufficiency levels. Our results demonstrate that the development of VAM effectiveness is the phase of the VAM symbiosis that is most adversely influenced by simulated erosion and that this effect appears to be caused primarily by insufficient P in the soil solution.
Biomass of the cryptoendolithic microbiota from the Antarctic desert
Authors: Vestal J R
Published: January 2020

Extractable lipid phosphate was used to determine the biomass of the cryptoendolithic microbiota that colonizes sandstone rocks in the Ross Desert region of Antarctica. The mean amount of lipid phosphate was 0.053 micromole/cm2 (n = 9), which equals 2.54 g of C per m2 (range, 1.92 to 3.26 g of C per m2) of biomass in the biotic zone of these rocks. The turnover of phospholipids was comparable to that of temperate sediments and soils (t1/2, 6 to 9 days) at 0 degrees C and a light intensity of 305 micromoles of photons per m2 per s, indicating that this was a good method to measure viable biomass. The biomass was 0.3 to 9.6% of the total carbon content of the biotic zone and was about 2 orders of magnitude smaller than the epilithic lichen dry weight at a location some 7 degrees north in latitude. The cryptoendolithic microbiota had a uniform density throughout the biotic zone under the rock surface. The results indicate that the cryptoendolithic microbial biomass is small but viable in this unique, extreme ecosystem.
Production and Purification of
d
-Aminoacylase from
Alcaligenes denitrificans
and Taxonomic Study of the Strain
Authors: Tsai Ying-Chieh , Tseng Ching-Ping , Hsiao Kuang-Ming , Chen Ling-Yun
Published: January 2020

A
d
-aminoacylase-producing microorganism, strain DA181, isolated from soil was identified as
Alcaligenes denitrificans
subsp.
denitrificans
. This strain produced about 29,300 units (micromoles of product formed per hour) of
d
-aminoacylase and 2,300 units of
l
-aminoacylase per gram of cells (wet weight) when cultivated in a medium containing 1%
N
-acetyl-
dl
-leucine as the carbon source. The
d
-aminoacylase was purified 345-fold. The specific activity of the purified enzyme was 108,600 units per mg of protein when
N
-acetyl-
d
-methionine was used as a substrate. The apparent molecular weight was 58,000, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
N
-Acetyl-
d
-methionine was the favored substrate, followed by
N
-acetyl-
d
-phenylalanine. This enzyme had a high stereospecificity, and its hydrolysis of
N
-acetyl-
l
-amino acids was almost negligible.
Citreoviridin levels in Eupenicillium ochrosalmoneum-infested maize kernels at harvest
Authors: Wicklow D T , Stubblefield R D , Horn B W , Shotwell O L
Published: January 2020

Citreoviridin contents were measured in eight bulk samples of maize kernels collected from eight fields immediately following harvest in southern Georgia. Citreoviridin contamination in six of the bulk samples ranged from 19 to 2,790 micrograms/kg. In hand-picked samples the toxin was concentrated in a few kernels (pick-outs), the contents of which were stained a bright lemon yellow (range, 53,800 to 759,900 micrograms/kg). The citreoviridin-producing fungus Eupenicillium ochrosalmoneum Scott & Stolk was isolated from each of these pick-out kernels. Citreoviridin was not detected in bulk samples from two of the fields. Aflatoxins were also present in all of the bulk samples (total aflatoxin B1 and B2; range, 7 to 360 micrograms/kg), including those not containing citreoviridin. In Biotron-grown maize ears that were inoculated with E. ochrosalmoneum through a wound made with a toothpick, citreoviridin was concentrated primarily in the wounded and fungus-rotted kernels (range, 142,000 to 2,780,000 micrograms/kg). Samples of uninjured kernels immediately adjacent to the wounded kernel (first circle) had less than 4,000 micrograms of citreoviridin per kg, while the mean concentration of toxin in kernel samples representing the next row removed (second circle) and all remaining kernels from the ear was less than 45 micrograms/kg. Animal toxicosis has not been linked to citreoviridin-contaminated maize.
Anti-Candida albicans activity of Pichia anomala as determined by a growth rate reduction assay
Authors: Sawant A D , Abdelal A T , Ahearn D G
Published: January 2020

Killer toxin activity of Pichia anomala WC65 appeared fungicidal for P. bimundalis WC38 and fungistatic for Candida albicans RC1. Inhibitory activity against sensitive C. albicans showed a linear relationship between toxin concentrations and the inverse of the reduced growth rates. The plot of toxin concentrations against growth rates was hyperbolic, as is characteristic of saturation kinetics. Sensitivity of C. albicans to the toxin decreased with increased cell age. The measurement of growth rate reduction provided a simple and accurate method for quantitation of toxin.
Regulation of sinefungin biosynthesis by the wild-type strain and mutants of Streptomyces incarnatus
Authors: Malina H , Robert-Gero M
Published: January 2020

Sinefungin, an antifungal and antiparasitic antibiotic, is produced efficiently from ammonium citrate by prototrophic strains of Streptomyces incarnatus. The regulation of the biosynthesis of this nucleoside, composed of adenosine and ornithine, was studied by using auxotrophic mutants and a resting-cell system. Mutants blocked in arginine synthesis were not able to produce sinefungin. A uridine-negative mutant produced sinefungin in the presence of ATP, but this production was strongly inhibited when amino acids of the urea cycle were added. The same mutant produced sinefungin from aspartic acid, and this production was enhanced by ornithine. Our results show that the ornithine part of the molecule originates from arginine, liberated by either anabolic or catabolic processes.