bluuebunny/crossref_metadata_2025 huggingface dataset:
Campylobacter jejuni survival in chicken meat as a function of temperature
Authors: Blankenship L C , Craven S E
Published: January 2020

Recognition of Campylobacter fetus subsp. jejuni (referred to hereafter as C. jejuni) as an important human pathogen and its isolation from meat products indicate the need for knowledge of its survival characteristics in meats. Thermal death times (D-values) for a single strain and a five-strain composite were determined in 1% peptone and autoclaved ground chicken meat at temperatures ranging from 49 to 57 degrees C. Survival was determined for these strains in chicken meat at 4, 23, 37, and 43 degrees C. Survival was also determined on raw chicken drumsticks stored at 4 degrees C in either an ambient or a CO2 atmosphere. D-values were greater in chicken meat than in peptone in all cases. D-values in peptone for strain H-840 at 49, 51, 53, 55, and 57 degrees C were 15.2, 4.90, 1.71, 0,64, and 0.25 min, respectively. The corresponding D-values in ground chicken meat were 20.5, 8.77, 4.85, 2.12, and 0.79 min, respectively. Similar results were obtained with a composite of five strains. When sterile ground chicken meat was inoculated with approximately 10(6) to 10(7) C. jejuni cells per g and stored at 37 degrees C in an ambient atmosphere, a 1-to 2-log count increase occurred during the first 4 days, followed by a gradual decline of about 1 log during the remainder of the 17-day storage period. No growth was observed among similarly inoculated samples that were stored at 4, 23, and 43 degrees C but counts declined by about 1 to 2 logs at 4 degrees C (17 day), by 2.5 to 5 logs at 23 degrees C (17 days), and to undetectable levels at 43 degrees C (between 10 and 16 days). Survival on raw chicken drumsticks stored at 4 degrees C in CO2 and in an ambient atmosphere declined by about 1.5 and 2.0 logs, respectively, during 21 days of storage. The effect of temperature on the survival of C. jejuni in chicken meat was similar to that reported in other natural and laboratory milieus. Ordinary cooking procedures that destroy salmonellae would be expected to destroy C. jejuni.
Survival and growth of Campylobacter fetus subsp. jejuni on meat and in cooked foods
Authors: Gill C O , Harris L M
Published: January 2020

Twelve strains of Campylobacter fetus subsp. jejuni isolated from humans and animals grew at temperatures ranging from 34 to 45 degrees C and pH minima between 5.7 and 5.9. Only one strain grew at pH 5.8 with lactic acid present at a concentration similar to that in meat. All strains had decimal reduction times of less than 1 min at 60 degrees C. Further examination of a typical strain showed that it grew at 37 degrees C on high-pH meat but not at 37 degrees C on normal-pH meat. Bacterial numbers on both high (6.4)-pH and normal (5.8)-pH inoculated meat declined at a similar rate when the meat was stored at 25 degrees C. At -1 degree C, the rate of die-off was somewhat slower on normal-pH meat but was very much slower on high-pH meat. The initial fall in bacterial numbers that occurred when meat was frozen was also greater for normal-pH meat than for high-pH meat. The organism exhibited a long lag phase (1 to 2 days) when grown in cooked-meat medium at 37 degrees C and died in meat pies stored at 37 or 43 degrees C. Evaluation of the risk of Campylobacter contamination of red-meat carcasses to human health must take into account the limited potential of the organism to grow or even survive on fresh meats and in warm prepared foods.
Selection of antibiotic-resistant standard plate count bacteria during water treatment
Authors: Armstrong J L , Calomiris J J , Seidler R J
Published: January 2020

Standard plate count (SPC) bacteria were isolated from a drinking-water treatment facility and from the river supplying the facility. All isolates were identified and tested for their resistance to six antibiotics to determine if drug-resistant bacteria were selected for as a consequence of water treatment. Among the isolates surviving our test procedures, there was a significant selection (P less than 0.05) of gram-negative SPC organisms resistant to two or more of the test antibiotics. These bacteria were isolated from the flash mix tank, where chlorine, alum, and lime are added to the water. Streptomycin resistance in particular was more frequent in this population as compared with bacteria in the untreated river water (P less than 0.01). SPC bacteria from the clear well, which is a tank holding the finished drinking water at the treatment facility, were also more frequently antibiotic resistant than were the respective river water populations. When 15.8 and 18.2% of the river water bacteria were multiply antibiotic resistant, 57.1 and 43.5%, respectively, of the SPC bacteria in the clear well were multiply antibiotic resistant. Selection for bacteria exhibiting resistance to streptomycin was achieved by chlorinating river water in the laboratory. We concluded that the selective factors operating in the aquatic environment of a water treatment facility can act to increase the proportion of antibiotic-resistant members of the SPC bacterial population in treated drinking water.
New process for T-2 toxin production
Authors: Cullen D , Smalley E B , Caldwell R W
Published: January 2020

Strains of Fusarium produced high levels of T-2 toxin when cultured on certain media absorbed into vermiculite. Modified Gregory medium was nutritionally complex (2% soya meal, 0.5% corn steep liquor, 10% glucose) and, when inoculated with the appropriate fungal strain, yielded maximum T-2 toxin within 24 days of incubation at 19 degrees C. On Vogel synthetic medium N (H. J. Vogel, Microb. Genet, Bull. 13:42-43, 1956) supplemented with 5% glucose, optimal toxin levels were synthesized after incubation for 12 to 14 days at 15 degrees C. Fusarium tricinctum T-340 produced 714 and 353 mg/liter on modified Gregory medium and Vogel synthetic medium N plus 5% glucose, respectively. Improved analytical procedures were developed and involved aqueous methanol extraction, purification by liquid-liquid partitions, and gas-chromatographic quantitation.
Statistical analysis of the direct count method for enumerating bacteria
Authors: Kirchman D , Sigda J , Kapuscinski R , Mitchell R
Published: January 2020

The direct count method for enumerating bacteria in natural environments is widely used. This paper analyzes the sources of variation contributed by the various levels of the method: subsamples, filters, and microscope fields. Based on a nested analysis of variance, we show that most of the variance (less than 80%) is caused by the fields and that the filters contributed nearly all of the remaining variance. The replication at each of the levels determines the total cost and error of a measurement. We compared several sampling schemes, including an optimal strategy which gives the lowest possible variance for a given cost. We recommend that preparing one filter from one subsample is adequate only if the samples are closely spaced in time or distance; otherwise, one filter should be prepared from two or preferably three subsamples. This sampling scheme emphasizes the importance of the highest level of replication. Our analysis shows that the accuracy of the direct count method can be substantially improved (by 20 to 50%) without a large increase in cost when the proper degree of replication at each level is performed.
Diurnal variations in bacterial numbers and fluid parameters in ruminal contents of animals fed low- or high-forage diets
Authors: Leedle J A , Bryant M P , Hespell R B
Published: January 2020

Differential carbohydrate media and anaerobic replica plating techniques were used to assess the degrees of diurnal variations in the direct and viable cell counts as well as the carbohydrate-specific subgroups within the mixed rumen bacterial populations in cattle fed maintenance (metabolizable energy) levels of either a high-forage or a high-concentrate diet once daily. The rumen was sampled at 1 h before feeding and 2, 4, 8, 12, and 16 h after feeding, and selected microbiological parameters of the isolated bacterial populations were assessed. Corresponding samples of ruminal fluid were assayed for fermentation acids, carbohydrate, ammonia, and pH changes. The data showed that regardless of diet, total bacterial numbers remained fairly constant throughout the day. The number of viable bacteria declined 40 to 60% after feeding and then increased to a maximum at 16 h postfeeding. Changes occurred in the carbohydrate-specific subgroups within the bacterial populations, and some of the changes were consistent with a predicted scheme of ruminal feedstuff carbohydrate fermentation. Regardless of diet, however, soluble-carbohydrate-utilizing bacteria predominated at all times. Xylan-xylose and pectin subgroups respectively comprised about one-half and one-third of the population when the high-forage diet was given. These subgroups, along with the cellulolytics, constituted lesser proportions of the population when the high-concentrate diet was given. The cellulolytic subgroup was the least numerous of all subgroups regardless of diet but followed a diurnal pattern similar to that predicted for cellulose fermentation. There were few diurnal variations or differences in bacterial cell compositions and ruminal fluid parameters between diets. The observed similarities and dissimilarities of the rumen bacterial populations obtained when the two diets were given are discussed. The data are consistent with the versatility and constancy of the rumen as a stable, mature microbial system under the specific low-level feeding regimens used.
Isolation of
Frankia
Strains from Alder Actinorhizal Root Nodules
Authors: Benson David R.
Published: January 2020

A simple procedure, based on the rapid filtration and washing of
Frankia
vesicle clusters, was devised for the isolation of
Frankia
strains from alder actinorhizal root nodules. Of 46
Alnus incana
subsp.
rugosa
nodules prepared, 42 yielded isolates. A simple medium containing mineral salts, Casamino Acids, and sodium pyruvate proved to be the most effective for isolation. In general, colonies appeared 6 to 20 days after inoculation. On the basis of hyphal morphology, two distinct types of
Frankia
strains were characterized. Randomly selected isolates were tested for infectivity, and all formed root nodules on
A. glutinosa.
Because of its simplicity and efficiency, the procedure is an improved method for the study of
Frankia
diversity in alder root nodules.
Morphological varieties and host ranges of Vibrio parahaemolyticus bacteriophages isolated from seawater
Authors: Koga T , Toyoshima S , Kawata T
Published: January 2020

Eighteen bacteriophages lytic for Vibrio parahaemolyticus were isolated from seawater, and their ultrastructure was examined by electron microscopy. Based on the phage morphology, they were classified in four groups. Group I phages consisted of a hexagonal head and a tail with a contractile sheath. All the phages of the other three groups had a relatively long, noncontractile tail, but there were differences in the head structure among these phages. The phages of groups II and III had a hexagonal head and an elongated polyhedral head, respectively. Group IV phages exhibited a unique hexagonal head with knoblike projections. There appeared to be no correlation between the O and K serotypes of V. parahaemolyticus strains and the host ranges of the phages. The phages had varying sensitivities to heat and organic solvents.
Amoebae from antarctic soil and water
Authors: Brown T J , Cursons R T , Keys E A
Published: January 2020

Samples of soil and water were taken from the McMurdo Sound-Dry Valley region of Antarctica. Of the 70 samples cultured, 22 yielded amoebae capable of clonal growth at 30 degrees C. None of the isolates was pathogenic for mice. Acanthamoeba isolates appeared to show better survival potential than Naegleria isolates.
Minimal Medium for Isolation of Auxotrophic
Zymomonas
Mutants
Authors: Goodman Amanda E. , Rogers Peter L. , Skotnicki Mary L.
Published: January 2020

A minimal medium which allowed the sustained, rapid growth of
Zymomonas mobilis
and the isolation of a range of auxotrophic mutants was developed.
Biodegradation of 2,4,5-trichlorophenoxyacetic acid in soil by a pure culture of Pseudomonas cepacia
Authors: Chatterjee D K , Kilbane J J , Chakrabarty A M
Published: January 2020

A pure culture of Pseudomonas cepacia AC1100 was able to degrade and grow in presence of 2,4,5-trichlorophenoxyacetic acid in soil. At optimum temperature (30 degrees C) and moisture content (15 to 50% [wt/vol]) strain AC1100 could degrade as much as 95% of 2,4,5-trichlorophenoxyacetic acid at high concentration (1 mg/g of soil) within 1 week.
Thermal inactivation of Yersinia enterocolitica in milk
Authors: Lovett J , Bradshaw J G , Peeler J T
Published: January 2020

Three strains of Yersinia enterocolitica isolated from milk had D values at 62.8 degrees C from 0.24 to 0.96 min and z values of 5.11 to 5.78 degrees C. Since the pasteurization processes for dairy products recommended by the Food and Drug Administration are adequate to destroy large concentrations of these organisms, Y. enterocolitica in pasteurized milk probably results from substandard processing or recontamination after pasteurization.
Antimicrobial properties of diacetyl
Authors: Jay J M
Published: January 2020

Diacetyl preparations from three commercial sources were found to be essentially similar when tested primarily against a set of 40 cultures, including 10 of lactic acid bacteria, 4 of yeasts, 12 of gram-positive non-lactic acid bacteria, and 14 of gram-negative bacteria. The compound was effective at pH less than or equal to 7.0 and progressively ineffective at pH greater than 7.0. The lactic acid bacteria were essentially unaffected by concentrations between 100 and 350 micrograms/ml over the pH range of 5.0 to 7.0. Of the 12 gram-positive non-lactic acid bacteria, 11 were inhibited by 300 micrograms/ml at pH less than or equal to 7.0. The three yeasts and the 13 gram-negative bacteria that grew at pH 5.5 were inhibited by 200 micrograms/ml. Diacetyl was ineffective against four clostridia under anaerobic conditions. It was lethal for gram-negative bacteria and generally inhibitory for gram-positive bacteria. Nongrowing cells were not affected. The effectiveness of diacetyl was considerably less in brain heart infusion broth, Trypticase soy agar, and cooked-meat medium than in nutrient broth or plate count agar. The antimicrobial activity was antagonized by glucose, acetate, and Tween 80 but not by gluconic acid. As an antimicrobial agent, diacetyl was clearly more effective against gram-negative bacteria, yeasts, and molds than against gram-positive bacteria.
Protamine precipitation of two reovirus particle types from polluted waters
Authors: Adams D J , Ridinger D N , Spendlove R S , Barnett B B
Published: January 2020

Two forms of virus particle are released from reovirus-infected cell cultures, infectious reovirus and potentially infectious reovirus (PIV). PIV particle forms have a complete outer coat and are not infectious until the outer coat is altered or removed. The PIV concentration in polluted waters, however, has not been determined. Protamine sulfate precipitation, using 0.25% fetal bovine serum and 0.005% protamine sulfate for the first precipitation of the sample and 0.0025% for the second, was employed to concentrate infectious reovirus and PIV from water and sewage. Infectious reovirus and PIV particles were concentrated over 500-fold from river water inoculated with virus, and virus recoveries of between 80 and 100% were achieved. Virus precipitates stored at -20 degrees C as a protamine-virus concentrate showed a 5% loss of PIV after 14 days. Virus preparations were assayed, before and after treatment, with 200 micrograms of chymotrypsin per ml, using a fluorescent-antibody procedure. Protamine sulfate precipitation and fluorescent-antibody detection are effective ways to recover and assay reoviruses present in raw sewage.
Microbiological quality of some spices and herbs in retail markets
Authors: Schwab A H , Harpestad A D , Swartzentruber A , Lanier J M , Wentz B A , Duran A P , Barnard R J , Read R B
Published: January 2020

The microbiological quality of 10 spices or herbs was determined by a national survey at the retail level. Aerobic plate count values for the 10 products ranged from less than 100 to 3.1 X 10(8) per g; mean values of the individual spices or herbs ranged from 1,400 to 820,000 per g. Coliform counts ranged from less than 3 to 1.1 X 10(6) per g; however, mean values were less than 20 per g for all products. Escherichia coli counts ranged from less than 3 to 2,300 per g. Except for celery seed, which had a mean value of 7 per g, all mean values were less than 3 per g. Yeast and mold counts were made for 5 of the 10 products. Mean values were generally low; the highest mean (290 per g) was obtained for cinnamon.
Lognormal Distribution of Epiphytic Bacterial Populations on Leaf Surfaces
Authors: Hirano Susan S. , Nordheim Erik V. , Arny Deane C. , Upper Christen D.
Published: January 2020

Total populations of epiphytic bacteria and selected components thereof were determined on sets of 24 to 36 individual leaves (corn, rye) or leaflets (snap bean, soybean, tomato) of field-grown plants by washing and dilution plating. In general, levels of component populations (e.g., bacteria that are ice nucleation active) were quantitatively more variable from leaf to leaf within a set than were total epiphytic bacterial populations. Populations of a given component frequently varied by a factor of 100 to 1,000 within a set of leaves. Total bacterial populations usually varied by a factor of about 10. For each set of leaves, total and component epiphytic bacterial populations were found to approximate a lognormal distribution by the Shapiro-Wilk test for normality. Due to the lognormal distribution of epiphytic bacterial populations, estimates of population size based on the common practice of using bulked samples (wherein several leaves are washed together) will overestimate the population median by a factor of approximately 1.15σ
2
. From the known probability distribution of bacterial populations, the frequency with which a given bacterial population size is met or exceeded on individual leaves can be estimated. If the bacterial component is phytopathogenic, the frequency estimates could be used to relate quantitatively pathogen populations and disease incidence.
Ultrastructural Localization of Hydrogen Peroxide Production in Ligninolytic
Phanerochaete chrysosporium
Cells
Authors: Forney Larry J. , Reddy C. A. , Pankratz H. Stuart
Published: January 2020

Previous studies have shown that the hydroxyl radical derived from hydrogen peroxide (H
2
O
2
) is involved in lignin degradation by
Phanerochaete chrysosporium.
In the present study, the ultrastructural sites of H
2
O
2
production in ligninolytic cells of
P. chrysosporium
were demonstrated by cytochemically staining cells with 3,3′-diaminobenzidine (DAB). Hydrogen peroxide production, as evidenced by the presence of oxidized DAB deposits, appeared to be localized in the periplasmic space of cells from ligninolytic cultures grown for 14 days in nitrogen-limited medium. When identical cells were treated with DAB in the presence of aminotriazole, periplasmic deposits of oxidized DAB were not observed, suggesting that the deposits resulted from the H
2
O
2
-dependent peroxidatic oxidation of DAB by catalase. Cells from cultures grown for 3 or 6 days in nitrogen-limited medium or for 14 days in nitrogen-sufficient medium had little ligninolytic activity and low specific activity for H
2
O
2
production and did not contain periplasmic oxidized DAB deposits. The results suggest that in cultures grown in nitrogen-limited medium, there is a positive correlation between the occurrence of oxidized DAB deposits, the specific activity for H
2
O
2
production in cell extracts, and ligninolytic activity.
Improved Method for Detection of Starch Hydrolysis
Authors: Dhawale Motiram R. , Wilson J. Jeffrey , Khachatourians George G. , Ingledew W. Mike
Published: January 2020

A new starch hydrolysis detection method which does not rely on iodine staining or the use of color-complexed starch is described. A linear relationship was obtained with agar-starch plates when net clearing zones around colonies of yeasts were plotted against enzyme levels (semilogarithm scale) produced by the same yeast strains in liquid medium. A similar relationship between starch clearing zones and α-amylase levels from three different sources was observed. These observations suggest that the method is useful in mutant isolations, strain improvement programs, and the prediction of α-amylase activities in culture filtrates or column effluents.
Secalonic acid D: natural contaminant of corn dust
Authors: Ehrlich K C , Lee L S , Ciegler A , Palmgren M S
Published: January 2020

The mycotoxin secalonic acid D was detected for the first time as a natural contaminant of corn dust obtained from grain storage elevators. Secalonic acid D amounts ranged from 0.3 to 4.5 ppm (0.3 to 4.5 micrograms/g), as determined by reversed-phase high-performance liquid chromatography.
Hemagglutinating activity in extracts of mycelia from submerged mushroom cultures
Authors: Banerjee P C , Ghosh A K , Sengupta S
Published: January 2020

Extracts from mycelia of seven different mushrooms agglutinated erythrocytes of several species. More than one agglutinating factor was identified in the extracts of three different mycelia. Agglutination was partially inhibited nonspecifically by high concentrations of glucose, galactose, mannose, fucose, and rhamnose.
Effect of antecedent growth conditions on sensitivity of Escherichia coli to chlorine dioxide
Authors: Berg J D , Matin A , Roberts P V
Published: January 2020

Bacterial resistance to inactivation by antibacterial agents that is induced by the growth environment was studied. Escherichia coli was grown in batch culture and in a chemostat, and the following parameters were varied: type of substrate, growth rate, temperature, and cell density during growth. Low doses (0.75 mg/liter) of chlorine dioxide were used to inactivate the cultures. The results demonstrated that populations grown under conditions that more closely approximated natural aquatic environments were more resistant than those grown under commonly employed batch culture conditions. In particular, bacteria grown at submaximal rates were more resistant than their counterparts grown at mumax. The most resistant populations encountered in this study were those grown at D values of 0.02 h-1 and 0.06 h-1 at 25 degrees C. Growth at 15 degrees C led to greater resistance than did growth at 37 degrees C. The conditions that produced relatively resistant phenotypes were much closer to those found in most natural environments than are the typical conditions of batch culture methods. The importance of major physiological changes that can be induced by the antecedent growth environment is discussed in light of the possible modes of action of several disinfectants.
Accessory replicons of species of Salmonella and Shigella
Authors: Dhillon T S , Hui Y W , Teoh-Chan C H , Dhillon E K
Published: January 2020

Shigella and Salmonella strains isolated from clinical samples were examined. Out of 42 Shigella strains tested, 17 (40%) were found to be colicinogenic and another 3 were lysogenic. All three lysogens yielded a phage antigenically homologous to coliphage P2. Out of 30 strains tested, only 1 was found to be resistant to both neomycin and sulfamethoxazole. Out of 48 strains of Salmonella tested for drug resistance, only 2 showed multiple drug resistance. In contrast to Shigella isolates, the Salmonella isolates were infrequently (approximately 5%) bacteriocinogenic. The frequency of lysogeny in Salmonella strains was found to be 6% when tested on Salmonella typhimurium LT2, but by using a set of five indicators belonging to species Salmonella potsdam, Salmonella mbadanka, Salmonella dublin, Salmonella london, and Salmonella wandsworth, 50% of the strains were shown to be lysogenic. Salmonella phages related to P22 were recoverable from Salmonella saintpaul, Salmonella indiana, and Salmonella heidelberg. Some isolates of S. typhimurium yielded a temperature-sensitive and P22-heterologous phage which was found to be a more efficient transducer of bacterial genetic markers than P22. EcoRI-generated fragments of the DNA of some phages permitted the establishment of a clonal descent for some of the wild-type lysogenic bacterial strains. This last observation points out the potential usefulness of prophages as epidemiological markers.
Adsorption of reovirus by minerals and soils
Authors: Moore R S , Taylor D H , Reddy M M , Sturman L S
Published: January 2020

Adsorption of [35S]methionine-labeled reovirus by 30 dry soils, minerals, and finely ground rocks suspended in synthetic freshwater at pH 7 was investigated to determine the conditions necessary for optimum virus removal during land application of wastewaters. All of the minerals and soils studied were excellent adsorbents of reovirus, with greater than 99% of the virus adsorbed after 1 h at 4 degrees C. Thereafter, virus remaining in suspension was significantly inactivated, and within 24 h a three to five log10 reduction in titer occurred. The presence of divalent cations, i.e., Ca2+ and Mg2+, in synthetic freshwater enhanced removal, whereas soluble organic matter decreased the amount of virus adsorbed in secondary effluent. The amount of virus adsorbed by these substrates was inversely correlated with the amount of organic matter, capacity to adsorb cationic polyelectrolyte, and electrophoretic mobility. Adsorption increased with increasing available surface area, as suspended infectivity was reduced further by the more finely divided substrates. However, the organic content of the soils reduced the level of infectious virus adsorbed below that expected from surface area measurements alone. The inverse correlation between virus adsorption and substrate capacity for cationic polyelectrolyte indicates that the adsorption of infectious reovirus particles is predominately a charged colloidal particle-charged surface interaction. Thus, adsorption of polyelectrolyte may be useful in predicting the fate of viruses during land application of sewage effluents and sludges.
Removal of Sulfur Compounds from Coal by the Thermophilic Organism
Sulfolobus acidocaldarius
Authors: Kargi Fikret , Robinson James M.
Published: January 2020

The thermophilic, reduced-sulfur, iron-oxidizing bacterium
Sulfolobus acidocaldarius
was used for the removal of sulfur compounds from coal. The inclusion of complex nutrients such as yeast extract and peptone, and chemical oxidizing agents, 0.01 M FeCl
3
into leaching medium, reduced the rate and the extent of sulfur removal from coal. The rate of sulfur removal by
S. acidocaldarius
was strongly dependent on the sulfur content of the coal and on the total external surface area of coal particles. Approximately 96% of inorganic sulfur was removed from a 5% slurry of coal which had an initial total sulfur content of 4% and an inorganic (pyritic S and sulfate) sulfur content of 2.1%. This resulted in removal of 50% of initial total sulfur present in coal.
Effect of Salinity on
Rhizobium
Growth and Survival
Authors: Singleton P. W. , El Swaify S. A. , Bohlool B. B.
Published: January 2020

This study examines the effect of salinity on the growth and survival of
Rhizobium
spp. in culture media and soil. Eleven isolates from saline and nonsaline environments were compared. The growth (mean doubling time) of all strains and species tested decreased when the electrical conductivity of the culture medium (yeast extract-mannitol) was raised from 1.2 mS cm
−1
to 6.7 mS cm
−1
(15% seawater equivalent) or to 13.1 mS cm
−1
(28% seawater equivalent). Three of eleven strains failed to grow at 13.1 mS cm
−1
. Although growth was affected by salinity, four strains selected from the growth rate study could survive in extremely high concentrations of salt. Two strains with growth rates sensitive to salt and two strains with growth rates relatively unaffected by salt were inoculated into solutions with electrical conductivities of up to 43.0 mS cm
−1
(92% seawater equivalent). Not only did all four strains survive the initial osmotic shock (at 5 h after inoculation), but it was not until 27 days after inoculation that the sensitive strains exhibited a significant reduction in viable numbers. The salt-tolerant strains survived for more than 65 days with no reduction in viable counts. The interaction between soil moisture tension and soil salinity in relation to
Rhizobium
survival in gamma-irradiated soil was also examined. Six treatment combinations were used, ranging from −0.1 bars and 0.2 mS cm
−1
to −15 bars and 12 mS cm
−1
. Sensitive strains declined from 10
7
to 10
5
organisms per g of soil after 84 days of incubation at −15 bars and 12 mS cm
−1
. Tolerant strains survived for the same period with no loss in viable numbers. The results of these experiments indicate that many strains of
Rhizobium
can grow and survive at salt concentrations which are inhibitory to most agricultural legumes. The emphasis of research concerning the effects of salinity on symbiotic nitrogen fixation should, therefore, be directed to aspects of the symbiosis other than the survival of the
Rhizobium
spp.
Selected Nucleic Acid Precursors in Studies of Aquatic Microbial Ecology
Authors: Karl David M.
Published: January 2020

The use of radiolabeled nucleosides and nucleic acid bases to estimate the rates of RNA and DNA synthesis in naturally occurring microbial assemblages requires numerous assumptions, several of which are evaluated herein. Comparative time series analyses of the uptake and incorporation, labeling specificity, and extent of catabolism of [2-
3
H]adenine, [
methyl
-
3
H]thymidine, and [5-
3
H]uridine were performed with pure bacterial and algal cultures, as well as with environmental samples. [
3
H]thymidine yielded the most variable results, especially with regard to the extent of nonspecific macromolecular labeling. The pathways of [
3
H]thymidine and [
3
H]adenine metabolism were further evaluated by isotope dilution methods and by comparing incorporation patterns of thymidine labeled at different sites of the molecule. The advantages, uncertainties, and limitations of the use of radiolabeled nucleic acid precursors in studies of aquatic microbial ecology are discussed and a prospectus for future studies presented.
Changes in Viability, Cell Composition, and Enzyme Levels During Starvation of Continuously Cultured (Ammonia-Limited)
Selenomonas ruminantium
Authors: Mink Ronald W. , Patterson John A. , Hespell Robert B.
Published: January 2020

Under nitrogen (ammonia)-limited continuous culture conditions, the ruminal anaerobe
Selenomonas ruminantium
was grown at various dilution rates (D). The proportion of the population that was viable increased with D, being 91% at D = 0.5 h
−1
. Washed cell suspensions were subjected to long-term nutrient starvation at 39°C. All populations exhibited logarithmic linear declines in viability that were related to the growth rate. Cells grown at D = 0.05, 0.20, and 0.50 lost about 50% viability after 8.1, 4.6, and 3.6 h, respectively. The linear rates of decline in total cell numbers were dramatically less and constant regardless of dilution rate. All major cell constituents declined during starvation, with the rates of decline being greatest with RNA, followed by DNA, carbohydrate, cell dry weight, and protein. The rates of RNA loss increased with cells grown at higher D values, whereas the opposite was observed for rates of carbohydrate losses. The majority of the degraded RNA was not catabolized but was excreted into the suspending buffer. At all D values,
S. ruminantium
produced mainly lactate and lesser amounts of acetate, propionate, and succinate during growth. With starvation, only small amounts of acetate were produced. Addition of glucose, vitamins, or both to the suspending buffer or starvation in the spent culture medium resulted in greater losses of viability than in buffer alone. Examination of extracts made from starving cells indicated that fructose diphosphate aldolase and lactate dehydrogenase activities remained relatively constant. Both urease and glutamate dehydrogenase activities declined gradually during starvation, whereas glutamine synthetase activity increased slightly. The data indicate that nitrogen (ammonia)-limited
S. ruminantium
cells have limited survival capacity, but this capacity is greater than that found previously with energy (glucose)-limited cells. Apparently no one cellular constituent serves as a catabolic substrate for endogenous metabolism. Relative to losses in viability, cellular enzymes are stable, indicating that nonviable cells maintain potential metabolic activity and that generalized, nonspecific enzyme degradation is not a major factor contributing to viability loss.
Microwave sterilization of plastic tissue culture vessels for reuse
Authors: Sanborn M R , Wan S K , Bulard R
Published: January 2020

A simple protocol has been developed for recycling plastic tissue culture vessels. The killing properties of microwaves were used to decontaminate plastic tissue culture vessels for reuse. Nine bacterial cultures, four gram-negative and five gram-positive genera, including two Bacillus species, were used to artificially contaminate tissue culture vessels. The microwaves produced by a "home-type" microwave oven (2.45 gHz) were able to decontaminate the vessels with a 3-min exposure. The same exposure time was also used to completely inactivate the following three test viruses: polio type 1, parainfluenza type 1 (Sendai), and bacteriophage T4. The recycling procedure did not reduce the attachment and proliferation of the following cell types: primary chicken and turkey embryo, HEp-2, Vero, BGMK, and MK-2.
Isolation and Complementation Studies of Auxotrophic Mutants of the Lignin-Degrading Basidiomycete
Phanerochaete chrysosporium
Authors: Gold Michael H. , Cheng Therese M. , Mayfield Mary B.
Published: January 2020

A variety of auxotrophic strains of
Phanerochaete chrysosporium
were isolated after treatment of conidia with UV and X rays. Complementation studies with these strains demonstrated heterokaryotic mycelia and conidia in this organism. Nuclear staining also showed that conidia can be mono-, di-, or multinucleate. Complementation tests allowed the separation of each auxotrophic class with the same phenotype into complementation groups.
Competitiveness of
Rhizobium trifolii
Strains Associated with Red Clover (
Trifolium pratense
L.) in Mississippi Soils
Authors: Materon L. A. , Hagedorn C.
Published: January 2020

Five strains of
Rhizobium trifolii
were evaluated in competition with indigenous populations in nodulating red clover (
Trifolium pratense
L.) cv. Kenland in two different soils in Mississippi. Double antibiotic resistance acquisition was used to measure the proportion of nodules occupied by the introduced mutant strains. In vertisol soil, strains RP113-7, 162BB1, LM1, and 162P17 were recovered in at least 94% of the assayed nodules, whereas TA1 was found in 83.8% of the nodules. At an ultisol location, significant differences were detected within the introduced rhizobia. Strain RP113-7 was recovered at very high rates (99.2% of the assayed nodules), whereas strains 162BB1, LM1, 162P17, and TA1 were all found in 84.9 to 96.0% of the nodules sampled. Forage yield and percent crude protein levels were lower with the less effective but competitive strain (TA1) at both locations. Results indicated that more effective strains of
R. trifolii
can increase red clover production and symbiotic nitrogen fixation under different environmental conditions in Mississippi.
Membrane lipid alterations and thermal stress in Salmonella typhimurium 7136
Authors: Tomlins R I , Watkins T R , Gray R J
Published: January 2020

Salmonella typhimurium ATCC 7136 exhibited major changes in lipid composition when grown in the presence of either 0.15% sodium deoxycholate or 0.15% sodium benzoate. These lipophilic compounds had directly opposing effects on the lipid profile of the organism. The saturated/unsaturated ratio was markedly elevated in benzoate-grown cells. On the other hand, it was depressed by an even greater margin from the control after growth in the presence of deoxycholate. Adjustments in the phospholipid content of the cells were also recorded. Phosphatidylethanolamines decreased by 28 and 50% in the deoxycholate- and benzoate-grown cells, respectively. Compensatory increases in phosphatidylglycerols of 87.5 and 175% occurred, along with increases in cardiolipins of 12- and 22-fold, respectively. Deoxycholate or benzoate supplementation also altered the relative distribution of neutral lipids; again, benzoate stimulated the greater change. Compositional changes were accompanied in the organism by increased heat sensitivity, but the effect on the susceptibility of S. typhimurium to injury varied with the physical properties of the supplement used.
Microbial Oxidation of Hydrocarbons: Properties of a Soluble Methane Monooxygenase from a Facultative Methane-Utilizing Organism,
Methylobacterium
sp. Strain CRL-26
Authors: Patel Ramesh N. , Hou Ching T. , Laskin Allen I. , Felix Andre
Published: January 2020

Methylobacterium
sp. strain CRL-26 grown in a fermentor contained methane monooxygenase activity in soluble fractions. Soluble methane monooxygenase catalyzed the epoxidation/hydroxylation of a variety of hydrocarbons, including terminal alkenes, internal alkenes, substituted alkenes, branched-chain alkenes, alkanes (C
1
to C
8
), substituted alkanes, branched-chain alkanes, carbon monoxide, ethers, and cyclic and aromatic compounds. The optimum pH and temperature for the epoxidation of propylene by soluble methane monooxygenase were found to be 7.0 and 40°C, respectively. Among various compounds tested, only NADH
2
or NADPH
2
could act as an electron donor. Formate and NAD
+
(in the presence of formate dehydrogenase contained in the soluble fraction) or 2-butanol in the presence of NAD
+
and secondary alcohol dehydrogenase generated the NADH
2
required for the methane monooxygenase. Epoxidation of propylene catalyzed by methane monooxygenase was not inhibited by a range of potential inhibitors, including metal-chelating compounds and potassium cyanide. Sulfhydryl agents and acriflavin inhibited monooxygenase activity. Soluble methane monooxygenase was resolved into three components by ion-exchange chromatography. All three compounds are required for the epoxidation and hydroxylation reactions.
Survival rates of parasite eggs in sludge during aerobic and anaerobic digestion
Authors: Black M I , Scarpino P V , O'Donnell C J , Meyer K B , Jones J V , Kaneshiro E S
Published: January 2020

The effects of mesothermic anaerobic or aerobic sludge digestion on survival of eggs from the roundworms Ascaris suum, toxocara canis, Trichuris vulpis, and Trichuris suis and from the rat tapeworm Hymenolepis diminuta were studied. Destruction of eggs throughout a 15-day treatment period, as well as their viabilities after reisolation, was analyzed. The laboratory model digesters used in this study were maintained at a 15-day retention schedule, partially simulating a continuously operating system. Ascaris eggs were destroyed in the anaerobic (23%) or aerobic (38%) digesters, and 11% Trichuris eggs were destroyed in the aerobic digesters. Trichuris eggs in anaerobic digesters and Toxocara eggs in either anaerobic or aerobic digesters were not destroyed. Destruction of eggs in digesters was correlated with the state of the eggs before subjection to the treatment processes; i.e., some Ascaris and Trichuris eggs were already embryonated in host intestinal contents or feces and hence past their most resistant stage. The viabilities of Ascaris and Toxocara eggs that survived the digestion processes were greater in anaerobically treated than in aerobically treated material. Eggs from Hymenolepis were nonviable before use in the experiments. However, they were more effectively destroyed in aerobic digesters than in anaerobic digesters.
Barophilic Bacteria Associated with Digestive Tracts of Abyssal Holothurians
Authors: Deming Jody W. , Colwell Rita R.
Published: January 2020

Abyssal holothurians and sediment samples were collected at depths of 4,430 to 4,850 m in the Demerara abyssal plain. Bacterial concentrations in progressive sections of the holothurian digestive tract, as well as in surrounding surface sediments, were determined by epifluorescence microscopy. Total bacterial counts in sediments recently ingested by the animals were 1.5- to 3-fold higher than in surrounding sediments at the deepest station. Lowest counts were observed consistently in the foregut, where the digestive processes of the holothurian are believed to occur. In most animals, counts increased 3- to 10-fold in the hindgut. Microbial activity at 3°C and in situ and atmospheric pressure were determined for gut and sediment samples by measuring the utilization of [
14
C]glutamic acid, the doubling time of the mixed-population of culturable bacteria, and the percentage of the total bacterial count responsive to yeast extract in the presence of nalidixic acid, using epifluorescence microscopy. A barophilic microbial population, showing elevated activity under deep-sea pressure, was detected by all three methods in sediments removed from the hindgut. Transmission electron micrographs revealed intact bacteria directly associated with the intestinal lining only in the hindgut. The bacteria are believed to be carried as an actively metabolizing, commensal gut flora that transforms organic matter present in abyssal sediments ingested by the holothurian. Using data obtained in this study, it was calculated that sediment containing organic matter altered by microbial activity cleared the holothurian gut every 16 h, suggesting that abyssal holothurians and their associated gut flora are important participants in nutrient cycles of the abyssal benthic ocean.
Strain-Specific Differences in Surface Antigens of Symbiotic Algae
Authors: Kinzie R. A. , Chee G. S.
Published: January 2020

Intracellular symbiotic dinoflagellates (zooxanthellae) isolated from different invertebrate hosts are morphologically similar but could be differentiated by the fluorescent-antibody technique.
Ammonium Production by Dissimilatory Nitrate Reducers Isolated from Baltic Sea Water, as Indicated by
15
N Study
Authors: Samuelsson Matts-Ola , Rönner Ulf
Published: January 2020

Bacteria able to perform dissimilatory nitrate reduction to ammonium were isolated from low-oxygen masses in the Baltic Sea. In liquid media enriched with
15
NO
3
−
and incubated anaerobically, the NH
4
+
-producing isolates transformed 25 to 72% of the
15
NO
3
−
to
15
NH
4
+
.
Microbial Production of Ursodeoxycholic Acid from Lithocholic Acid by
Fusarium equiseti
M41
Authors: Sawada Haruji , Kulprecha Songsri , Nilubol Naline , Yoshida Toshiomi , Kinoshita Shinichi , Taguchi Hisaharu
Published: January 2020

A fungus identified as
Fusarium equiseti
was isolated from soil and found to carry out 7β-hydroxylation of lithocholic acid to ursodeoxycholic acid (35% yield; 350 mg/liter) in 112 h.
Autolytic Activity and Butanol Tolerance of
Clostridium acetobutylicum
Authors: Van Der Westhuizen Andre , Jones David T. , Woods David R.
Published: January 2020

The effects of acetone and butanol on the growth of vegetative cells and the stability of swollen-phase bright-stationary-phase cells (clostridial forms) of
Clostridium acetobutylicum
P262 and an autolytic deficient mutant (
lyt-1
) were investigated. There was little difference in the sensitivity of strain P262 and the
lyt-1
mutant vegetative cells and clostridial forms to acetone. The stability of the different morphological stages was unaffected by acetone concentrations far in excess of those encountered in factory fermentations. Butanol concentrations between 7 and 16 g/liter, which are within the range obtained in industrial fermentations, increased the degeneration of strain P262 clostridial forms but had no effect on the stability of
lyt-1
clostridial forms which never underwent autolysis. Vegetative cells of the
lyt-1
mutant were able to grow in higher concentrations of butanol than strain P262 vegetative cells. It was concluded that there is a relationship between butanol tolerance and autolytic activity.
Purification and Properties of β-Glucosidase from
Aspergillus terreus
Authors: Workman Wesley E. , Day Donal F.
Published: January 2020

A β-glucosidase (EC 3.2.1.21) from the fungus
Aspergillus terreus
was purified to homogeneity as indicated by disc acrylamide gel electrophoresis. Optimal activity was observed at pH 4.8 and 50°C. The β-glucosidase had

K
m

values of 0.78 and 0.40 mM for
p
-nitrophenyl-β-
d
-glucopyranoside and cellobiose, respectively. Glucose was a competitive inhibitor, with a

K
i

of 3.5 mM when
p
-nitrophenyl-β-
d
-glucopyranoside was used as the substrate. The specific activity of the enzyme was found to be 210 IU and 215 U per mg of protein on
p
-nitrophenyl-β-
d
-glucopyranoside and cellobiose substrates, respectively. Cations, proteases, and enzyme inhibitors had little or no effect on the enzyme activity. The β-glucosidase was found to be a glycoprotein containing 65% carbohydrate by weight. It had a Stokes radius of 5.9 nm and an approximate molecular weight of 275,000. The affinity and specific activity that the isolated β-glucosidase exhibited for cellobiose compared favorably with the values obtained for β-glucosidases from other organisms being studied for use in industrial cellulose saccharification.
Glucose Metabolism in Sediments of a Eutrophic Lake: Tracer Analysis of Uptake and Product Formation
Authors: King Gary M. , Klug M. J.
Published: January 2020

The uptake of glucose and the formation of end products from glucose catabolism have been measured for sediments of eutrophic Wintergreen Lake with a combination of tritiated and
14
C-labeled tracers. Time course analyses of the loss of [
3
H]glucose from sediments were used to establish rate constants for glucose uptake at natural substrate concentrations. Turnover times from these analyses were about 1 min for littoral and profundal sediments. No seasonal or site differences were noted in turnover times. Time course analyses of [
U
-
14
C]glucose uptake and
14
C-labeled end product formation indicated that glucose mass flow could not be calculated from end product formation since the specific activity of added [
14
C]glucose was significantly diluted by pools of intracellular glucose and glucose metabolites. Mass flow could only be accurately estimated by use of rates of uptake from tracer studies. Intermediate fermentation end products included acetate (71%), propionate (15%), lactate (9%), and only minor amounts of butyrates or valerates. Addition of H
2
to sediments resulted in greater production of lactate (28%) and decreased formation of acetate (50%), but did not affect glucose turnover. Depth profiles of glucose uptake indicated that rates of uptake decreased with depth over the 0- to 18-cm interval and that glucose uptake accounted for 30 to 40% of methanogenesis in profundal sediments.