bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of water activity and pH on growth and toxin production by Clostridium botulinum type G
Authors: Briozzo J , de Lagarde E A , Chirife J , Parada J L
Published: January 2020

The combined effect of water activity (aw) and pH on growth and toxin production by Clostridium botulinum type G strain 89 was investigated. The minimum aw at which growth and toxin formation occurred was 0.965, for media in which the pH was adjusted with either sodium chloride or sucrose. The minimum pH (at the optimum aw) for growth and toxin production of C. botulinum type G was found to be 5.6. Optimum conditions for toxin activation were a trypsin concentration of 0.1%, a pH of the medium of 6.5, and an incubation for 45 min at 37 degrees C. These data did not show evidence of heat-labile spores, since a heat shock of 75 degrees C for 10 min did not significantly decrease the spore count of strain 89G in media at pH 7.0 or 5.6. It was frequently observed that cells grown at reduced aw or pH experienced severe morphological changes.
Comparison of Two
Cellulomonas
Strains and Their Interaction with
Azospirillum brasilense
in Degradation of Wheat Straw and Associated Nitrogen Fixation
Authors: Halsall Dorothy M. , Gibson Alan H.
Published: January 2020

A mutant strain of
Cellulomonas
sp. CS1-17 was compared with
Cellulomonas gelida
2480 as the cellulolytic component of a mixed culture which was responsible for the breakdown of wheat straw to support asymbiotic nitrogen fixation by
Azospirillum brasilense
Sp7 (ATCC 29145).
Cellulomonas
sp. strain CSI-17 was more efficient than was
C. gelida
in cellulose breakdown at lower oxygen concentrations and, in mixed culture with
A. brasilense
, it supported higher nitrogenase activity (C
2
H
2
reduction) and nitrogen fixation with straw as the carbon source. Based on gravimetric determinations of straw breakdown and total N determinations, the efficiency of nitrogen fixation was 72 and 63 mg of N per g of straw utilized for the mixtures containing
Cellulomonas
sp. and
C. gelida
, respectively. Both
Cellulomonas
spp. and
Azospirillum
spp. exhibited a wide range of pH tolerance. When introduced into sterilized soil, the
Cellulomonas
sp.-
Azospirillum brasilense
association was more effective in nitrogen fixation at a pH of 7.0 than at the native soil pH (5.6). This was also true of the indigenous diazotrophic microflora of this soil. The potential implications of this work to the field situation are discussed.
Asymbiotic Acetylene Reduction by a Fast-Growing Cowpea
Rhizobium
Strain with Nitrogenase Structural Genes Located on a Symbiotic Plasmid
Authors: Bender Gregory L. , Plazinski Jacek , Rolfe Barry G.
Published: January 2020

A procedure was designed which enabled the detection of ex planta nitrogenase activity in the fast-growing cowpea
Rhizobium
strain IHP100. Nitrogenase activity in agar culture under air occurred at a rate similar to that found for
Bradyrhizobium
strain CB756 but lower than that for
Rhizobium
strain ORS571. Hybridization studies showed that both
nod
and
nif
genes were located on a 410-kilobase Sym plasmid in strain IHP100.
Inoculation Response of Legumes in Relation to the Number and Effectiveness of Indigenous Rhizobium Populations
Authors: Singleton P. W. , Tavares J. W.
Published: January 2020

The response of legumes to inoculation with rhizobia can be affected by many factors. Little work has been undertaken to examine how indigenous populations or rhizobia affect this response. We conducted a series of inoculation trials in four Hawaiian soils with six legume species (
Glycine max, Vigna unguiculata, Phaseolus lunatus, Leucaena leucocephala, Arachis hypogaea
, and
Phaseolus vulgaris
) and characterized the native rhizobial populations for each species in terms of the number and effectiveness of the population for a particular host. Inoculated plants had, on average, 76% of the nodules formed by the inoculum strain, which effectively eliminated competition from native strains as a variable between soils. Rhizobia populations ranged from less than 6 × 10
0
/g of soil to 1 × 10
4
/g of soil. The concentration of nitrogen in shoots of inoculated plants was not higher than that in uninoculated controls when the most probable number MPN counts of rhizobia were at or above 2 × 10
1
/g of soil unless the native population was completely ineffective. Tests of random isolates from nodules of uninoculated plants revealed that within most soil populations there was a wide range of effectiveness for N
2
fixation. All populations had isolates that were ineffective in fixing N
2
. The inoculum strains generally did not fix more N
2
than the average isolate from the soil population in single-isolate tests. Even when the inoculum strain proved to be a better symbiont than the soil rhizobia, there was no response to inoculation. Enhanced N
2
fixation after inoculation was related to increased nodule dry weights. Although inoculation generally increased nodule number when there were less than 1 × 10
2
rhizobia per g of soil, there was no corresponding increase in nodule dry weight when native populations were effective. Most species compensated for reduced nodulation in soils with few rhizobia by increasing the size of nodules and therefore maintaining a nodule dry weight similar to that of inoculated plants with more nodules. Even when competition by native soil strains was overcome with a selected inoculum strain, it was not always possible to enhance N
2
fixation when soil populations were above a threshold number and had some effective strains.
Growth of Methanogenic Bacteria in Pure Culture with 2-Propanol and Other Alcohols as Hydrogen Donors
Authors: Widdel Friedrich
Published: January 2020

Two types of mesophilic, methanogenic bacteria were isolated in pure culture from anaerobic freshwater and marine mud with 2-propanol as the hydrogen donor. The freshwater strain (SK) was a
Methanospirillum
species, the marine, salt-requiring strain (CV), which had irregular coccoid cells, resembled
Methanogenium
sp. Stoichiometric measurements revealed formation of 1 mol of CH
4
by CO
2
reduction, with 4 mol of 2-propanol being converted to acetone. In addition to 2-propanol, the isolates used 2-butanol, H
2
, or formate but not methanol or polyols. Acetate did not serve as an energy substrate but was necessary as a carbon source. Strain CV also oxidized ethanol or 1-propanol to acetate or propionate, respectively; growth on the latter alcohols was slower, but final cell densities were about threefold higher than on 2-propanol. Both strains grew well in defined, bicarbonate-buffered, sulfide-reduced media. For cultivation of strain CV, additions of biotin, vitamin B
12
, and tungstate were necessary. The newly isolated strains are the first methanogens that were shown to grow in pure culture with alcohols other than methanol. Bioenergetic aspects of secondary and primary alcohol utilization by methanogens are discussed.
Aerobic Hydrogen Accumulation by a Nitrogen-Fixing Cyanobacterium,
Anabaena
sp
Authors: Asada Yasuo , Kawamura Sugio
Published: January 2020

Hydrogen evolution by a nitrogen-fixing cyanobacterium,
Anabaena
sp. strain N-7363, was tested in order to develop a water biophotolysis system under aerobic conditions. A culture of the strain supplemented with carbon dioxide under an air atmosphere evolved hydrogen and oxygen gas, which reached final concentrations of 9.7 and 69.8%, respectively, after 12 days of incubation. Hydrogen uptake activity was not observed during incubation, and nitrogenase was thought to be the sole enzyme responsible for the hydrogen evolution.
Influence of Location, Host Cultivar, and Inoculation on the Composition of Naturalized Populations of
Rhizobium meliloti
in
Medicago sativa
Nodules
Authors: Bromfield E. S. P. , Sinha Indu B. , Wolynetz M. S.
Published: January 2020

A phage typing system was used to evaluate the composition of indigenous populations of
Rhizobium meliloti
inhabiting nodules of
Medicago sativa
cultivars grown with and without inoculation at two field sites during 1983 and 1984. Soil at both locations contained established populations of
R. meliloti
at planting. Analysis of 1,920 nodule isolates revealed 55 unique phage types of indigenous
R. meliloti
at one site and 65 indigenous types at the other location. The distributions of phage types differed markedly between locations. At one site, the nodule population was dominated by two phage types; seven others occurred consistently but at lower frequency, and the remainder were encountered infrequently. No indigenous types predominated at the other location, although nine occurred more frequently than the remaining types. Indigenous
R. meliloti
predominated in nodules from inoculated plots at both sites, with inoculant recovery varying between 10 and 38% in each of two years. The frequency of occurrence of particular phage types at one location was significantly influenced by both
M. sativa
cultivar and inoculation. At this location, the interaction of cultivar and inoculation on the incidence of phage types suggests that the presence of an inoculant strain differentially affected nodule occupancy of
M. sativa
cultivars by members of the indigenous
R. meliloti
population. At both sites, the frequency of specific phage types differed between years. The data emphasize the importance of understanding the ecology and characteristics of indigenous
Rhizobium
populations as a prerequisite for elucidating problems of inoculant establishment and persistence in competitive situations.
Improved Agar Bottle Plate for Isolation of Methanogens or Other Anaerobes in a Defined Gas Atmosphere
Authors: Hermann Monique , Noll Kenneth M. , Wolfe Ralph S.
Published: January 2020

A bottle plate for the cultivation of methanogens or other organisms in a defined pressurized-gas atmosphere was developed. The bottle provides the convenience of an agar streak plate, solves the problem of the water exudate from agar medium, and provides a convenient way of adding or sampling a defined gas atmosphere.
Binding of Germanium to
Pseudomonas putida
Cells
Authors: Kłapcińska Barbara , Chmielowski Jerzy
Published: January 2020

The binding of germanium to
Pseudomonas putida
ATCC 33015 was investigated by using whole intact cells grown in a medium supplemented with GeO
2
and catechol or acetate. Electron-microscopic examination of the control and metal-loaded samples revealed that germanium was bound within the cell envelope. A certain number of small electron-dense deposits of the bound element were found in the cytoplasm when the cells were grown in the presence of GeO
2
and catechol. The study of germanium distribution in cellular fractions revealed that catechol facilitated the intracellular accumulation of this element.
Identification of a plasmid-borne parathion hydrolase gene from Flavobacterium sp. by southern hybridization with opd from Pseudomonas diminuta
Authors: Mulbry W W , Karns J S , Kearney P C , Nelson J O , McDaniel C S , Wild J R
Published: January 2020

Parathion hydrolases have been previously described for an American isolate of Pseudomonas diminuta and a Philippine isolate of Flavobacterium sp. (ATCC 27551). The gene which encodes the broad-spectrum organophosphate phosphotriesterase in P. diminuta has been shown by other investigators to be located on a 66-kilobase (kb) plasmid. The intact gene (opd, organophosphate-degrading gene) from this degradative plasmid was cloned into M13mp10 and found to express parathion hydrolase under control of the lac promoter in Escherichia coli. In Flavobacterium sp. strain ATCC 27551, a 43-kb plasmid was associated with the production of parathion hydrolase by curing experiments. The M13mp10-cloned fragment of the opd gene from P. diminuta was used to identify a homologous genetic region from Flavobacterium sp. strain ATCC 27551. Southern hybridization experiments demonstrated that a genetic region from the 43-kb Flavobacterium sp. plasmid possessed significant homology to the opd sequence. Similar hybridization did not occur with three other native Flavobacterium sp. plasmids (approximately 23, 27, and 51 kb) present within this strain or with genomic DNA from cured strains. Restriction mapping of various recombinant DNA molecules containing subcloned fragments of both opd plasmids revealed that the restriction maps of the two opd regions were similar, if not identical, for all restriction endonucleases tested thus far. In contrast, the restriction maps of the cloned plasmid sequences outside the opd regions were not similar. Thus, it appears that the two discrete bacterial plasmids from parathion-hydrolyzing soil bacteria possess a common but limited region of sequence homology within potentially nonhomologous plasmid structures.
Variables Affecting Two Electron Transport System Assays
Authors: Burton G. Allen , Lanza Guy R.
Published: January 2020

Several methodological variables were critical in two commonly used electron transport activity assays. The dehydrogenase assay based on triphenyl formazan production exhibited a nonlinear relationship between formazan production (dehydrogenase activity) and sediment dilution, and linear formazan production occurred for 1 h in sediment slurries. Activity decreased with increased time of sediment storage at 4°C. Extraction efficiencies of formazan from sediment varied with alcohol type; methanol was unsatisfactory. Phosphate buffer (0.06 M) produced higher activity than did either U.S. Environmental Protection Agency reconstituted hard water or Tris buffer sediment diluents. Intracellular formazan crystals were dissolved within minutes when in contact with immersion oil. Greater crystal production (respiration) detected by a tetrazolium salt assay occurred at increased substrate concentrations. Test diluents containing macrophyte exudates produced greater activity than did phosphate buffer, U.S. Environmental Protection Agency water, or ultrapure water diluents. Both assays showed decreases in sediment or bacterial activity through time.
Relative Rates of Nitric Oxide and Nitrous Oxide Production by Nitrifiers, Denitrifiers, and Nitrate Respirers
Authors: Anderson Iris Cofman , Levine Joel S.
Published: January 2020

Biogenic emissions of nitric and nitrous oxides have important impacts on the photochemistry and chemistry of the atmosphere. Although biogenic production appears to be the overwhelming source of N
2
O, the magnitude of the biogenic emission of NO is very uncertain. In soils, possible sources of NO and N
2
O include nitrification by autotrophic and heterotrophic nitrifiers, denitrification by nitrifiers and denitrifiers, nitrate respiration by fermenters, and chemodenitrification. The availability of oxygen determines to a large extent the relative activities of these various groups of organisms. To better understand this influence, we investigated the effect of the partial pressure of oxygen (pO
2
) on the production of NO and N
2
O by a wide variety of common soil nitrifying, denitrifying, and nitrate-respiring bacteria under laboratory conditions. The production of NO per cell was highest by autotrophic nitrifiers and was independent of pO
2
in the range tested (0.5 to 10%), whereas N
2
O production was inversely proportional to pO
2
. Nitrous oxide production was highest in the denitrifier
Pseudomonas fluorescens
, but only under anaerobic conditions. The molar ratio of NO/N
2
O produced was usually greater than unity for nitrifiers and much less than unity for denitrifiers. Chemodenitrification was the major source of both the NO and N
2
O produced by the nitrate respirer
Serratia marcescens
. Chemodenitrification was also a possible source of NO and N
2
O in nitrifier cultures but only when high concentrations of nitrite had accumulated or were added to the medium. Although most of the denitrifiers produced NO and N
2
O only under anaerobic conditions, chemostat cultures of
Alcaligenes faecalis
continued to emit these gases even when the cultures were sparged with air. Based upon these results, we predict that aerobic soils are primary sources of NO and that N
2
O is produced only when there is sufficient soil moisture to provide the anaerobic microsites necessary for denitrification by either denitrifiers or nitrifiers.
Degradation of Pyridine by
Micrococcus luteus
Isolated from Soil
Authors: Sims Gerald K. , Sommers Lee E. , Konopka Allan
Published: January 2020

An organism capable of growth on pyridine was isolated from soil by enrichment culture techniques and identified as
Micrococcus luteus.
The organism oxidized pyridine for energy and released N contained in the pyridine ring as ammonium. The organism could not grow on mono- or disubstituted pyridinecarboxylic acids or hydroxy-, chloro-, amino-, or methylpyridines. Cell extracts of
M. luteus
could not degrade pyridine, 2-, 3-, or 4-hydroxypyridines or 2,3-dihydroxypyridine, regardless of added cofactors or cell particulate fraction. The organism had a NAD-linked succinate-semialdehyde dehydrogenase which was induced by pyridine. Cell extracts of
M. luteus
had constitutive amidase activity, and washed cells degraded formate and formamide without a lag. These data are consistent with a previously reported pathway for pyridine metabolism by species of
Bacillus, Brevibacterium
, and
Corynebacterium.
Cells of
M. luteus
were permeable to pyridinecarboxylic acids, monohydroxypyridines, 2,3-dihydroxypyridine, and monoamino- and methylpyridines. The results provide new evidence that the metabolism of pyridine by microorganisms does not require initial hydroxylation of the ring and that permeability barriers do not account for the extremely limited range of substrate isomers used by pyridine degraders.
Intergeneric hybrids of Saccharomyces cerevisiae and Zygosaccharomyces fermentati obtained by protoplast fusion
Authors: Pina A , Calderón I L , Benítez T
Published: January 2020

To obtain strains that are able to efficiently produce ethanol from different carbohydrates, mainly cellulose hydrolysates, several species of the genus Candida and a Zygosaccharomyces fermentati strain were examined for their ability to utilize cellobiose and produce ethanol, as well as for their thermotolerance and the possibility of genetic manipulation. Candida obtusa and Zygosaccharomyces fermentati tolerated the maximal temperature for growth, possessed the highest cellobiase activity, and offered the possibility of genetic manipulation, although neither of them proved to be a good producer of ethanol. Intergeneric hybrids of Saccharomyces cerevisiae and Z. fermentati were obtained after protoplast fusion. They were selected as prototrophic strains, after isolation of auxotrophic mutants from Z. fermentati and fusion with an S. cerevisiae strain which was also auxotrophic. The hybrids, which appeared at a frequency of 2 X 10(-7), presented characteristics of both parents, such as resistance to certain drugs and the ability to grow with either cellobiose or lactic acid as the sole carbon source; they were very stable, even under nonselective conditions. These hybrids may have important industrial applications as good fermenting strains.
Common Components of Industrial Metal-Working Fluids as Sources of Carbon for Bacterial Growth
Authors: Foxall-VanAken S. , Brown J. A. , Young W. , Salmeen I. , McClure T. , Napier S. , Olsen R. H.
Published: January 2020

Water-based metal-working fluids used in large-scale industrial operations consist of many components, but in the most commonly used formulations only three classes of components are present in high enough concentrations that they could, in principle, provide enough carbon to support the high bacterial densities (10
9
CFU/ml) often observed in contaminated factory fluids. These components are petroleum oil (1 to 5%), petroleum sulfonates (0.1 to 0.5%), and fatty acids (less than 0.1%, mainly linoleic and oleic acids supplied as tall oils). We isolated pure strains of predominating bacteria from contaminated reservoirs of two metal-working systems and randomly selected 12 strains which we tested in liquid culture for growth with each of the metal-working fluid components as the sole source of carbon. Of the 12 strains, 7 reached high density (10
9
CFU/ml from an initial inoculum of less than 2 × 10
3
) in 24 h, and 1 strain did the same in 48 h with 0.05% oleic or linoleic acid as the carbon source. These same strains also grew on 1% naphthenic petroleum oil but required up to 72 h to reach densities near 10
8
CFU/ml. One strain grew slightly and the others not at all on the petroleum sulfonates. The four remaining strains did not grow on any of the components, even though they were among the predominating bacteria in the contaminated system. Of the seven strains that grew best on the fatty acids and on the naphthenic petroleum oil, five were tentatively identified as
Acinetobacter
species and two were identified as
Pseudomonas
species. Four of the bacteria that did not grow were tentatively identified as species of
Pseudomonas
, and one could not be identified.
Characterization of Leucine Auxotrophs of the White Rot Basidiomycete
Phanerochaete chrysosporium
Authors: Molskness Theodore A. , Alic Margaret , Gold Michael H.
Published: January 2020

Six leucine auxotrophic strains of the white rot basidiomycete
Phanerochaete chrysosporium
were characterized genetically and biochemically. Complementation studies involving the use of heterokaryons identified three leucine complementation groups. Since all of the leucine auxotrophs grew on minimal medium supplemented with α-ketoisocaproate as well as with leucine, the transaminase catalyzing the last step in the leucine pathway was apparently normal in all strains. Therefore, the wild-type, auxotrophic, and several heterokaryotic strains were assayed for the activities of the other enzymes specific to leucine biosynthesis. Leu2 and Leu4 strains (complementation group I) lacked only α-isopropylmalate synthase activity; Leu3 and Leu6 strains (group III) lacked isopropylmalate isomerase activity; and Leu1 and Leu5 strains (group II) lacked β-isopropylmalate dehydrogenase. Heterokaryons formed from leucine auxotrophs of different complementation groups had levels of activity for all three enzymes similar to those found in the wild-type strain.
Effect of Nitrate on Biogenic Sulfide Production
Authors: Jenneman Gary E. , McInerney M. J. , Knapp Roy M.
Published: January 2020

The addition of 59 mM nitrate inhibited biogenic sulfide production in dilute sewage sludge (10% [vol/vol]) amended with 20 mM sulfate and either acetate, glucose, or hydrogen as electron donors. Similar results were found when pond sediment or oil field brines served as the inoculum. Sulfide production was inhibited for periods of at least 6 months and was accompanied by the oxidation of resazurin from its colorless reduced state to its pink oxidized state. Lower amounts of nitrate (6 or 20 mM) and increased amounts of sewage sludge resulted in only transient inhibition of sulfide production. The addition of 156 mM sulfate to bottles with 59 mM nitrate and 10% (vol/vol) sewage sludge or pond sediment resulted in sulfide production. Nitrate, nitrite, and nitrous oxide were detected during periods where sulfide production was inhibited, whereas nitrate, nitrite, and nitrous oxide were below detectable levels at the time sulfide production began. The oxidation of resazurin was attributed to an increase in nitrous oxide which persisted in concentration of about 1.0 mM for up to 5 months. The numbers of sulfate-reducing organisms decreased from 10
6
CFU ml
−1
sludge to less than detectable levels after prolonged incubation of oxidized bottles. The addition of 10 mM glucose to oxidized bottles after 14.5 weeks of incubation resulted in rereduction of the resazurin and subsequent sulfide production. The prolonged inhibition of sulfide production was attributed to an increase in oxidation-reduction potential due to biogenic production of nitrous oxide, which appeared to have a cytotoxic effect on sulfate-reducing populations.
Slow rehydration for detection of Salmonella spp. in feeds and feed ingredients
Authors: D'Aoust J Y , Sewell A M
Published: January 2020

Rehydration and equilibration (4 h) of feeds and feed ingredients at water/sample ratios (vol/wt) of 1.4 to 3.2 did not markedly increase recovery of Salmonella spp. in the slurry when analyzed by standard cultural and direct enrichment methods. Of 143 naturally contaminated samples examined, equilibration increased levels of detection from 106 to 109 positive samples by the standard cultural method and from 103 to 112 by direct enrichment. Results suggest that nonhomogeneous distribution of low incident numbers of salmonellae in test samples rather than an equilibration-dependent response provided for the observed heterogeneity in recovery patterns. The novel equilibration approach is of limited application and requires validation on an individual food basis.
High-Efficiency Carbohydrate Fermentation to Ethanol at Temperatures above 40°C by
Kluyveromyces marxianus
var.
marxianus
Isolated from Sugar Mills
Authors: Anderson P. J. , McNeil K. , Watson K.
Published: January 2020

A number of yeast strains, isolated from sugar cane mills and identified as strains of
Kluyveromyces marxianus
var.
marxianus
, were examined for their ability to ferment glucose and cane syrup to ethanol at high temperatures. Several strains were capable of rapid fermentation at temperatures up to 47°C. At 43°C, >6% (wt/vol) ethanol was produced after 12 to 14 h of fermentation, concurrent with retention of high cell viability (>80%). Although the type strain (CBS 712) of
K. marxianus
var.
marxianus
produced up to 6% (wt/vol) ethanol at 43°C, cell viability was low, 30 to 50%, and the fermentation time was 24 to 30 h. On the basis of currently available strains, we suggest that it may be possible by genetic engineering to construct yeasts capable of fermenting carbohydrates at temperatures close to 50°C to produce 10 to 15% (wt/vol) ethanol in 12 to 18 h with retention of cell viability.
Influence of substratum hydration and adsorbed macromolecules on bacterial attachment to surfaces
Authors: Pringle J H , Fletcher M
Published: January 2020

The attachment of Pseudomonas fluorescens and an Acinetobacter sp. to hydrogel and polystyrene surfaces was investigated to evaluate the influence of adsorbed water and macromolecules on adhesion. With both organisms, there was a decrease in attachment numbers with increasing water content of the hydrogels. There was also a decrease in attachment with a decrease in water contact angle on untreated, tissue culture and sulfonated polystyrene surfaces; however, the attachment numbers were higher than would be expected on the basis of the hydrogel data. With P. fluorescens, attachment to untreated and tissue culture polystyrene was inhibited by bovine serum albumin, Escherichia coli lipopolysaccharide, and the supernatant from spent medium, both when the conditioning substances were added to the suspension of attaching cells and when they were preadsorbed onto the surfaces. Dextran inhibited attachment only when added to the bacterial suspension. Supernatants from centrifuged natural freshwater samples had no effect. Thus, hydration of a surface and the adsorption of macromolecules can reduce bacterial attachment; however, additional factors relating to the chemical composition of the substratum and polymeric stabilization of suspended cells can affect the adhesion interaction and resultant numbers of attached cells.
Recovery of viruses from water by a modified flocculation procedure for second-step concentration
Authors: Dahling D R , Wright B A
Published: January 2020

A reduction in virus recovery efficiencies stemming from a change in the commercial processing of powdered beef extract was reversed by the addition of Celite analytical filter aid. Supplementing beef extract with this silicate is recommended as a modification to the organic flocculation procedure for second-step concentration in monitoring for waterborne viruses. Considerable differences in virus recovery were found among lots of beef extract and Celite preparations; this indicates that the performance of each lot of these substances should be checked before use.
Chemical Composition of the Edible Mushroom
Pleurotus ostreatus
Produced by Fermentation
Authors: Hadar Yitzhak , Cohen-Arazi Ephraim
Published: January 2020

Pleurotus ostreatus
`Florida' was grown in submerged liquid culture. The biomass yield of the fungus, grown for 3 days in 2-liter fermentors, where the mycelial pellets measuring 5 mm in diameter were formed, was 11.7 g (dry weight)/liter. Comparing the chemical constituents of fruiting bodies produced on cotton straw and mycelial pellets revealed several similarities in total nitrogen, protein, glycogen, fatty acids, RNA, and ash content. Differences were observed in the contents of six amino acids. Although the total fatty acid content was similar, there were more saturated fatty acids in the mycelium. Cell wall composition, typical for basidiomycetes, was observed in both mycelium and fruiting bodies, with laminarin as the main polymer.
Resistance to In Vitro Restriction of DNA from Lactic Streptococcal Bacteriophage c6A
Authors: Powell Ian B. , Davidson Barrie E.
Published: January 2020

DNA isolated from streptococcal bacteriophage c6A was cut only infrequently by many restriction endonucleases. Fragments of c6A DNA cloned in
Escherichia coli
plasmids were similarly resistant to cleavage. We conclude that the low frequency of cleavage is due to an unusually low number of restriction enzyme recognition sequences in c6A DNA.
Effects of pentachlorophenol and some of its known and possible metabolites on fungi
Authors: Ruckdeschel G , Renner G
Published: January 2020

The fungicidal activity of pentachlorophenol and its derivatives against 16 species of fungi representing 14 genera was tested. In relation to pentachlorophenol, no increase in fungistatic activity was found for pentachloroanisole, pentachloronitrobenzene, hexachlorobenzene, pentachlorophenyl acetate, o- and p-chloranil, the three isomeric chlorophenols, 2,6-dichlorophenol, the three isomeric tetrachlorobenzenediols, the three isomeric tetrachlorodimethoxybenzenes, the three isomeric tetrachlorobenzenediol diacetates, and all of the isomeric mono-, di-, tri-, and tetrachloroanisoles, except for 2,3,5-trichloroanisole with Geotrichum candidadum PC 67 and for 2,3,5,6-tetrachloroanisole with Mucor circinelloides PC 1. Increasing fungistatic activities were seen with 3,5-dichlorophenol, four trichlorophenols, and 2,3,4,5-tetrachlorophenol for all of the strains, with four dichlorophenols, 2,4,6-trichlorophenol, and two tetrachlorophenols for some strains, and with 2,3,6-trichlorophenol for only one strain (M. circinelloides PC 1).
Bacterial Inhibitors in Lake Water
Authors: Klein Theodore M. , Alexander Martin
Published: January 2020

The populations of six bacterial genera fell rapidly after their addition to sterile lake water but not after their addition to buffer. The decline in numbers of two species that were studied further,
Klebsiella pneumoniae
and
Micrococcus flavus
, occurred even when the buffer was added to sterile lake water. The inhibition of
K. pneumoniae
by substances in lake water varied with the season of the year, and the rate and extent of decline of both species were different in sterile samples of different lakes. The extent of reduction in the density of
K. pneumoniae
was independent of initial population size and was diminished by the addition of 10 μg of glucose per ml of lake water. The toxin was removed from lake water by dialysis and by a cation-exchange resin but not by an anion-exchange resin, and it was destroyed by heating. The inhibition of
K. pneumoniae
was not evident in lake water buffered at a pH value above 8.0. We suggest that toxins may be important in determining the composition of the bacterial community of lakes.
Enhanced emulsan production in mutants of Acinetobacter calcoaceticus RAG-1 selected for resistance to cetyltrimethylammonium bromide
Authors: Shabtai Y , Gutnick D L
Published: January 2020

Mutants of Acinetobacter calcoaceticus RAG-1 that produced elevated levels of the polymeric bioemulsifier emulsan were isolated on the basis of their resistance to the cationic surfactant cetyltrimethylammonium bromide (CTAB). Such mutants showed maximum enhancement in both overall yield and specific productivity of some two- to threefold over that of the wild type. In addition, the effect was also observed in a resting cell system in the presence of chloramphenicol, indicating that the mutation is not simply the result of faster growth. When CTAB-tolerant mutants were subjected together with the sensitive parent to the detergent under growing conditions, only the mutants were found to grow. The results suggest that the mutation for CTAB resistance leads to enhanced capsule production. This was confirmed quantitatively by a specific enzyme-linked immunosorbent assay for the cell-bound emulsan minicapsule.
Life Cycles in the Methanogenic Archaebacterium
Methanosarcina mazei
Authors: Robinson Ralph W.
Published: January 2020

Methanosarcina mazei
S6 and LYC were used to study the structure and differentiation of the aggregating methanogens. Cultures harvested under various conditions are described at the ultrastructural level. Cells of strain S6 are enclosed by a layer 12 nm thick in contact with the plasma membrane. In sarcinal colonies, cells are held in close association by a fibrous matrix up to 60 nm thick. Colony maturation was examined in strain S6 over a period of 1 year. Changes occurred in the shape and staining of individual cells. Also, various inclusion bodies were observed that either persist throughout colony maturation or are only found at certain growth stages. Two types of cores that are composed of double membranes in
M. mazei
S6 are described. One has a 90-nm diameter and contains electron-dense granules similar to those found in the cytoplasm. The other core type does not contain granules, is more numerous, and is found in older cultures. Two life cycles are described for
M. mazei
based on electron microscope examinations. A complex life cycle involving the release of single cells is described with two variations for strains S6 and LYC. When released cells of strain S6 are placed in fresh medium they can repeat the cycle. In addition, a limited cycle is described for both strains of
M. mazei.
This limited cycle contains the only sarcinal morphotypes observed in
M. barkeri.
When
M. mazei
S6 remains in the limited cycle and does not disaggregate in stationary phase, several types of possible resting forms are found.
Characterization, Biosynthesis, and Regulation of Granulose in
Clostridium acetobutylicum
Authors: Reysenbach A. L. , Ravenscroft N. , Long S. , Jones D. T. , Woods D. R.
Published: January 2020

Synthesis of granulose was investigated in 15 solvent-producing
Clostridium
strains. Only one of the strains did not produce granulose. The structure of granulose in
Clostridium acetobutylicum
P262 consisted of a high-molecular-weight polyglucan containing only (1→4) linked
d
-glucopyranose units. Biosynthesis of granulose in
C. acetobutylicum
P262 was dependent on ADPglucose pyrophosphorylase, and granulose synthase and mutants defective in granulose accumulation lacked either one or both enzyme activities. Granulose-positive revertants exhibited both enzyme activities. ADPglucose pyrophosphorylase and granulose synthase were not subject to allosteric control by metabolites. Granulose accumulation and the biosynthetic enzyme activities were initiated immediately before the pH breakpoint and were detected in cells only at the end of the exponential growth phase. Granulose accumulation did not occur under conditions of nitrogen limitation, excess carbon, or excess energy.
Model system for studies of microbial dynamics at exuding surfaces such as the rhizosphere
Authors: Odham G , Tunlid A , Valeur A , Sundin P , White D C
Published: January 2020

An autoclavable all-glass system for studying microbial dynamics at permeable surfaces is described. Standard hydrophobic or hydrophilic membranes (46-mm diameter) of various pore sizes were supported on a glass frit through which nutrient solutions were pumped by a peristaltic pump. The pump provided a precisely controlled flow at speeds of 0.5 to 500 ml of defined or natural cell exudates per h, which passed through the membrane into a receiving vessel. The construction allowed a choice of membranes, which could be modified. The system was tested with a bacterium, isolated from rape plant roots (Brassica napus L.), that was inoculated on a hydrophilic membrane filter and allowed to develop into a biofilm. A defined medium with a composition resembling that of natural rape root exudate was pumped through the membrane at 0.5 ml/h. Scanning electron microscopic examinations indicated that the inoculum formed microcolonies embedded in exopolymers evenly distributed over the membrane surface. The lipid composition and content of poly-beta-hydroxybutyrate in free-living and adhered cells were determined by gas chromatography. The bacterial consumption of amino acids in the exudate was also studied.
Avirulent isolates of Corynebacterium fascians that are unable to utilize agmatine and proline
Authors: Sabart P R , Gakovich D , Hanson R S
Published: January 2020

Growth of a highly virulent strain of the phytopathogen Corynebacterium fascians on rich media at 37 degrees C resulted in a loss of virulence in a majority of the population within 10 generations. Strains retained virulence during cultivation at 30 degrees C on a minimal medium with ammonia as a nitrogen source. Populations of avirulent strains on the surfaces of pea seedlings decreased, whereas the number of cells of the virulent strain increased 1,000-fold during a 3-week period. All avirulent mutants isolated by growth on rich media at 37 degrees C were unable to grow on media containing agmatine or proline as sole sources of nitrogen. The ability of the mutants to grow on pea seedlings and cause fasciation disease appeared to be related to their ability to utilize nitrogen sources available on plant surfaces.
Red pigment in Bacillus megaterium spores
Authors: Mitchell C , Iyer S , Skomurski J F , Vary J C
Published: January 2020

Bacillus megaterium QM B1551 spores contained a unique red pigment in their membranes that was not found in other species. This red pigment, presumably a carotenoid, was synthesized about the time of dipicolinic acid synthesis during sporulation and was associated with the forespores. A yellow pigment was synthesized during sporulation in rich medium and was found in the mother cell compartment. Although the yellow pigment was also associated with spores, it could be removed by two different extraction procedures without impairing germination; it was absent when sporulation occurred in a minimal medium. Although the yellow pigment of the mother cell appeared to be dispensable, the red pigment may serve a more critical function, such as membrane stabilization.
Characterization of a Mannitol-Utilizing, Nitrogen-Fixing
Bradyrhizobium japonicum
USDA 110 Derivative
Authors: Mathis James N. , Barbour W. Mark , Miller Terrence B. , Israel Daniel W. , Elkan Gerald H.
Published: January 2020

We have isolated a colonial derivative of
Bradyrhizobium japonicum
USDA 110 (designated MN-110) that is both mannitol utilizing and N
2
fixing. Derivative MN-110 showed growth on mannitol and glucose similar to that of non-N
2
-fixing, mannitol-utilizing L2-110. Derivative MN-110 showed high constitutive and induced
d
-mannitol dehydrogenase activity (similar to L2-110) relative to N
2
-fixing, non-mannitol-utilizing I-110. Hybridization to
Eco
RI and
Hin
dIII total DNA digests with cloned USDA 110
nif
DK and
nif
H genes revealed similar patterns for non-N
2
-fixing mannitol-utilizing derivative L1-110 and derivative MN-110. Symbiotic tests with soybean cultivars Ransom and Lee indicate MN-110 to be a superior N
2
-fixing derivative compared with derivative I-110 and the parent strain USDA 110. However, these differences were not revealed when comparing 28-day-old soybean-
B. japonicum
associations but were apparent in 49-day-old associations. It was apparent from this work that mannitol utilization was not necessarily correlated to symbiotic effectiveness in
B. japonicum
and that gene rearrangements were not responsible for differences in N
2
fixation between L1-110 or L2-110 and MN-110.
Growth Pattern and Yield of a Chemoautotrophic
Beggiatoa
sp. in Oxygen-Sulfide Microgradients
Authors: Nelson Douglas C. , Jørgensen Bo Barker , Revsbech Niels Peter
Published: January 2020

Recently developed techniques involving opposed, gel-stabilized gradients of O
2
and H
2
S permit cultivation of a marine
Beggiatoa
strain as a chemolithoautotroph which uses gliding motility to precisely track the interface between H
2
S and O
2
. In the current study with microelectrodes, vertical profiles of H
2
, O
2
, and pH were measured in replicate cultures grown for various intervals. After an initial period of exponential biomass increase (doubling time, 11 h), linear growth prevailed throughout much of the time course. This H
2
S-limited growth was followed by a transition to stationary phase when the declining H
2
S flux was sufficient only to supply maintenance energy. During late-exponential and linear growth phases, the
Beggiatoa
sp. consumed a constant 0.6 mol of H
2
S for each 1.0 mol of O
2
, the ratio anticipated for balanced lithoautotrophic growth at the expense of complete oxidation of H
2
S to SO
4
2−
. Over the entire range of conditions studied, this consumption ratio varied by approximately twofold. By measuring the extent to which the presence of the bacterial plate diminished the overlap of O
2
and H
2
S, we demonstrated that oxidation of H
2
S by
Beggiatoa
sp. is approximately 3 orders of magnitude faster than spontaneous chemical oxidation. By integrating sulfide profiles and comparing sulfide consumed with biomass produced, a growth yield of 8.4 g (dry weight) mol
−1
of H
2
S was computed. This is higher than that found for sulfide-grown thiobacilli, indicating very efficient growth of
Beggiatoa
sp. as a chemoautotroph. The methods used here offer a unique opportunity to determine the yield of H
2
S-oxidizing chemolithoautotrophs while avoiding several problems inherent in the use of homogeneous liquid culture. Finally, by monitoring time-dependent formation of H
2
S profiles under anoxic conditions, we demonstrate a method for calculating the molecular diffusion coefficient of soluble substrates in gel-stabilized media.
Development of high-level streptomycin resistance affected by a plasmid in lactic streptococci
Authors: Sinha R P
Published: January 2020

Some lactose-negative (Lac-) mutants of Streptococcus lactis C2 and ML3 exhibited development of very high level streptomycin resistance after incubation with subinhibitory concentrations of the drug for 18 to 22 h. These drug-resistant mutants showed no loss of resistance even after 6 months of subculturing in broth without any drug. The parental Lac+ strains did not show mutation to high-level streptomycin resistance. The Lac+ characteristic of the parental strain was conjugally transferred to Lac- derivatives of C2 and ML3, showing the ability to mutate to high-level resistance. When transconjugants were analyzed for this characteristic, they showed both mutable and nonmutable Lac+ types. The results suggested that genetic information for mutation to high-level streptomycin resistance in lactic streptococci resides on the chromosome, and its expression is affected by a plasmid. The plasmid profiles of strains C2, ML3, C2 Lac-, ML3 Lac-, and two kinds of transconjugants confirmed the presence of a plasmid of approximately 5.5 megadaltons in strains showing no mutation to high-level streptomycin resistance, while strains missing such a plasmid exhibited high-level streptomycin resistance after incubation with subinhibitory concentrations of the drug.
Nitrogen Limitation in Natural Populations of Cyanobacteria (
Spirulina
and
Oscillatoria
spp.) and Its Effect on Macromolecular Synthesis
Authors: van Rijn Jaap , Shilo Moshe
Published: January 2020

Natural populations of the cyanobacteria
Spirulina
species and
Oscillatoria
species obtained from Israeli fishponds were limited in growth by nitrogen availability in summer. Physiological indicators for nitrogen limitation, such as phycocyanin, chlorophyll
a
, and carbohydrate content, did not show clear evidence for nitrogen limited growth, since these organisms are capable of vertical migration from and to the nitrogen-rich bottom. By means of
14
C labeling of the cells under simulated pond conditions followed by cell fractionation into macromolecular compounds, we found that carbohydrates synthesized at the lighted surface were partially utilized for dark protein synthesis at the bottom of these ponds.
Kinetics of Phenol Biodegradation by an Immobilized Methanogenic Consortium
Authors: Dwyer Daryl F. , Krumme Mary Lou , Boyd Stephen A. , Tiedje James M.
Published: January 2020

A phenol-degrading methanogenic enrichment was successfully immobilized in agar as shown by the stoichiometric conversion of phenol to CH
4
and CO
2
. The enrichment contained members of three physiological groups necessary for the syntrophic mineralization of phenol: a phenol-oxidizing bacterium, a
Methanothrix
-like bacterium, and an H
2
-utilizing methanogen. The immobilization technique resulted in the cells being embedded in a long, thin agar strand (1 mm in diameter by 2 to 50 cm in length) that resembled spaghetti. Immobilization had three effects as shown by a comparative kinetic analysis of phenol degradation by free versus immobilized cells. (i) The maximum rate of degradation was reduced from 14.8 to 10.0 μg of phenol per h; (ii) the apparent

K
m

for the overall reaction was reduced from 90 to 46 μg of phenol per ml, probably because of the retention of acetate, H
2
and CO
2
in the proximity of immobilized methanogens; and (iii) the cells were protected from substrate inhibition caused by high concentrations of phenol, which increased the apparent

K
i

value from 900 to 1,725 μg of phenol per ml. Estimates for the kinetic parameters

K
m

,

K
i

, and

V
max

were used in a modified substrate inhibition model that simulated rates of phenol degradation for given phenol concentrations. The simulated rates were in close agreement with experimentally derived rates for both stimulatory and inhibitory concentrations of phenol.
Utilization of Lactate Isomers by
Propionibacterium freudenreichii
subsp.
shermanii
: Regulatory Role for Intracellular Pyruvate
Authors: Crow Vaughan L.
Published: January 2020

Five strains of
Propionibacterium freudenreichii
subsp.
shermanii
utilized the
l
-(+) isomer of lactate at a faster rate than they did the
d
-(−) isomer when grown with a mixture of lactate isomers under a variety of conditions. ATCC 9614, grown anaerobically in defined medium containing 160 mM
dl
-lactate, utilized only 4 and 15% of the
d
-(−)-lactate by the time 50 and 90%, respectively, of the
l
-(+)-lactate was used. The intracellular pyruvate concentration was high (>100 mM) in the initial stages of lactate utilization, when either
dl
-lactate or the
l
-(+) isomer was the starting substrate. The concentration of this intermediate dropped during
dl
-lactate fermentation such that when only
d
-(−)-lactate remained, the concentration was <20 mM. When only the
d
-(−) isomer was initially present, a similar relatively low concentration of intracellular pyruvate was present, even at the start of lactate utilization. The NAD
+
-independent lactate dehydrogenase activities in extracts showed different kinetic properties with regard to pyruvate inhibition, depending upon the lactate isomer present. Pyruvate gave a competitive inhibitor pattern with
l
-(+)-lactate and a mixed-type inhibitor pattern with
d
-(−)-lactate. It is suggested that these properties of the lactate dehydrogenases and the intracellular pyruvate concentrations explain the preferential use of the
l
-(+) isomer.