bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolism of Aspartate by
Propionibacterium freudenreichii
subsp.
shermanii
: Effect on Lactate Fermentation
Authors: Crow Vaughan L.
Published: January 2020

More than 90% of the aspartate in a defined medium was metabolized after lactate exhaustion such that 3 mol of aspartate and 1 mol of propionate were converted to 3 mol of succinate, 3 mol of ammonia, 1 mol of acetate, and 1 mol of CO
2
. This pathway was also evident when propionate and aspartate were the substrates in complex medium in the absence of lactate. In complex medium with lactate present, about 70% of the aspartate was metabolized to succinate and ammonia during lactate fermentation, and as a consequence of aspartate metabolism, more lactate was fermented to acetate and CO
2
than was fermented to propionate. The conversion of aspartate to fumarate and ammonia by the enzyme aspartase and subsequent reduction of fumarate to succinate occurred in the five strains of
Propionibacterium freudenreichii
subsp.
shermanii
studied. The ability to metabolize aspartate in the presence of lactate appeared to be related to aspartase activity. The specific activity of aspartase increased during and after lactate utilization, and the levels of this enzyme were lower in cells grown in defined medium than levels in those cells grown in complex medium. Under the conditions used, no other amino acids were readily metabolized in the presence of lactate. The possibility that aspartate metabolism by propionibacteria in Swiss cheese has an influence on CO
2
production is discussed.
Host-Symbiont Specificity Expressed during Early Adsorption of
Rhizobium meliloti
to the Root Surface of Alfalfa
Authors: Anollés Gustavo Caetano , Favelukes Gabriel
Published: January 2020

Early (4 h) adsorption of
Rhizobium meliloti
L5-30 in low numbers to alfalfa roots in mineral solution was examined for competition with other bacterial strains. All tested competitor strains decreased the adsorption of L5-30 by extents which depended on the strain and its concentration. The decrease of adsorption by
R. meliloti
competitors (all of them infective in alfalfa) was nearly complete at saturation (97 to 99% decrease). All other heterologous rhizobia and
Agrobacterium tumefaciens
at saturating concentrations (10
6
to 10
7
per ml) decreased adsorption of L5-30 only partially, less than 60%. The differential effects of homologous and heterologous competitors indicate that initial adsorption of
R. meliloti
to the root surface of its host occurs in symbiont-specific as well as nonspecific modes and suggest the existence of binding sites on roots which are highly selective for the specific microsymbiont in the presence of other heterologous bacteria even in very unfavorable (less than 10
−4
) symbiont-competitor concentration ratios.
Protoplast fusion of Lactobacillus fermentum
Authors: Iwata M , Mada M , Ishiwa H
Published: January 2020

Tetracycline-resistant (Tetr) erythromycin-resistant (Eryr) fusants of Lactobacillus fermentum 604 carrying a 10-megadalton Tetr plasmid and L. fermentum 605 carrying a 38-megadalton Eryr plasmid were obtained by means of polyethylene glycol-induced protoplast fusion.
Susceptibility of members of the family Legionellaceae to thermal stress: implications for heat eradication methods in water distribution systems
Authors: Stout J E , Best M G , Yu V L
Published: January 2020

To ascertain the feasibility of heat inactivation as an eradication method applicable to all members of the family Legionellaceae, we tested the heat resistance of 75 isolates which represented 19 members of this family of organisms. The ranges of thermal death times at 60, 70, and 80 degrees C were 1.3 to 10.6, 0.7 to 2.6, and 0.3 to 0.7 min, respectively. These data suggest that the method of heat eradication will be effective against all members of the family Legionellaceae.
Phenotypic and genotypic adaptation of aerobic heterotrophic sediment bacterial communities to mercury stress
Authors: Barkay T , Olson B H
Published: January 2020

The effects of mercury contamination of lake sediments on the phenotypic and genotypic mercury resistance of the indigenous heterotrophic aerobic bacterial communities were investigated. Strong positive correlations between mercury sediment concentration and the frequency of the gene coding for mercury volatilization (mer) (r = 0.96) or the phenotypic mercury resistance (r = 0.86) of the studied communities suggested that the inheritance via selection or genetic exchange of the mer gene had promoted bacterial adaptation to mercury. Failure to detect the mer gene in one mercury-contaminated sediment where phenotypic expression was low suggested that other mechanisms of resistance may partially determine the presence of mercury-resistant organisms in mercury-contaminated sediment or that the mercury in this particular sediment was very chemically limited in its availability to the microorganisms.
Yersinia enterocolitica and related species isolated from wildlife in New York State
Authors: Shayegani M , Stone W B , DeForge I , Root T , Parsons L M , Maupin P
Published: January 2020

Fecal specimens for Yersinia screening were obtained from a variety of wild mammals, birds, reptiles, fish, and invertebrates throughout New York State. One specimen from each of 1,426 animals was examined. A total of 148 isolates of Yersinia enterocolitica and related species were obtained from 133 (9.3%) of the animals. Y. enterocolitica was isolated from 100 (7%) of the animals tested, including 81 (10%) of 812 mammals and 19 (3.3%) of 573 birds. Y. intermedia, Y. frederiksenii, and Y. kristensenii were isolated from 39 (2.7%), 5 (0.35%), and 4 (0.28%) animals, respectively. The 81 Y. enterocolitica isolates from mammals belonged to 15 serogroups and included three pathogens: two isolates of typical serogroup 0:8, the "American strain," one from a gray fox (Urocyon cinereoargenteus) and one from a porcupine (Erethizon dorsatum); and one isolate of serogroup 0:3, bacteriophage type IXb, the "Canadian strain," from a gray fox. The most prevalent serogroups recovered from mammals were 0:6,31 (16 isolates) and 0:5,27 (6 isolates). The 19 isolates of Y. enterocolitica from birds belonged to nine serogroups and included one serogroup 0:6,31 isolate from a common grackle (Quiscalus quiscula) and two serogroup 0:5,27 isolates from great horned owls (Bubo virginianus).
Comparison of Clark's presence-absence test and the membrane filter method for coliform detection in potable water samples
Authors: Pipes W O , Minnigh H A , Moyer B , Troy M A
Published: January 2020

A total of 2,601 water samples from six different water systems were tested for coliform bacteria by Clark's presence-absence (P-A) test and by the membrane filter (MF) method. There was no significant difference in the fraction of samples positive for coliform bacteria for any of the systems tested. It was concluded that the two tests are equivalent for monitoring purposes. However, 152 samples were positive for coliform bacteria by the MF method but negative by the P-A test, and 132 samples were positive by the P-A test but negative by the MF method. Many of these differences for individual samples can be explained by random dispersion of bacteria in subsamples when the coliform density is low. However, 15 samples had MF counts greater than 3 and gave negative P-A results. The only apparent explanation for most of these results is that coliform bacteria were present in the P-A test bottles but did not produce acid and gas. Two other studies have reported more samples positive by Clark's P-A test than by the MF method.
Method for determining virus inactivation during sludge treatment processes
Authors: Traub F , Spillmann S K , Wyler R
Published: January 2020

A simple and reliable method is described which allows determination of virus inactivation rates during sludge treatment processes in situ. Bacteriophage f2 was adsorbed onto an electropositive membrane filter which was then sandwiched between two polycarbonate membranes with pores smaller than the virus diameter. The resulting sandwich was fixed in an open filter holder, and several such devices were connected before being exposed in sludge-digesting tanks. The device described prevented uncontrolled virus escape, but allowed direct contact of the various inactivating or stabilizing substances present in the environment tested with the virus adsorbed to the carrier membrane. After exposure to an environment, the surviving fraction of virus was eluted from the inner filter and determined by plaque counting. By using polycarbonate membranes without pores for sandwiching, the influence of temperature alone on virus inactivation could be measured. Thermophilic fermentation at 60 degrees C and at 65 kPa pressure led to a bacteriophage f2 titer reduction of 3.5 log10 units per h, whereas during thermophilic digestion at 54.5 degrees C titers decreased 1.2 log10 units per h. During mesophilic digestion an inactivation rate of only 0.04 log10 units per h was observed. Under these latter conditions, temperature had only a minor effect (19%) on virus inactivation, whereas at 54.5 degrees C during thermophilic digestion heat accounted for 32% of the total inactivation, and during thermophilic fermentation at 60 degrees C temperature and pressure were 100% responsible for virus denaturation.
Establishment of beta-hydroxy fatty acids as chemical marker molecules for bacterial endotoxin by gas chromatography-mass spectrometry
Authors: Maitra S K , Nachum R , Pearson F C
Published: January 2020

Selected ion-monitoring gas chromatography-mass spectrometry was used for detection of beta-hydroxy fatty acids as an independent assay for the presence or absence of endotoxin in materials claimed to induce nonspecific activation of Limulus amoebocyte lysate. To this end, suspensions of gram-negative and -positive bacteria, one fungal species, cerebrospinal fluid, and hollow-fiber hemodialyzer rinses were assayed for endotoxin by gas chromatography-mass spectrometry and the Limulus amoebocyte lysate assay. Good qualitative agreement was shown for both methods when suspensions of test organisms were assayed. Two false-negative results were obtained by gas chromatography-mass spectrometry assays of cerebrospinal fluid and were shown to be a result of insufficient endotoxin in the cerebrospinal fluid specimens for detection by gas chromatography-mass spectrometry. Hemodialyzer rinses were Limulus assay positive; however, no beta-hydroxy fatty acids were detected by gas chromatography-mass spectrometry. These data were compared with data obtained from USP rabbit pyrogen tests of the rinse materials (nonpyrogenic) and chemical characterization of the Limulus assay-reactive rinses, which showed the rinses to be cellulosic in nature. It is suggested that beta-hydroxy fatty acids, as assayed by selected ion-monitoring gas chromatography-mass spectrometry, be used as chemical marker molecules for the presence or absence of endotoxin in materials reported to cause nonspecific activation of Limulus amoebocyte lysate.
Microcetus lappus gen. nov., sp. nov.: new species of ciliated protozoon from the bovine rumen
Authors: Orpin C G , Mathiesen S D
Published: January 2020

A new species of small, ciliated protozoon, Microcetus lappus gen. nov., sp. nov., from the rumen of Norwegian Red cattle is described. M. lappus possesses a novel cytopharyngeal apparatus of two rod-shaped structures, one situated on the dorsal side of the buccal cavity and one on the ventral side, suggesting that it belongs to a previously undescribed taxon.
Antagonism of Lactic Acid Bacteria against Phytopathogenic Bacteria
Authors: Visser Ronèl , Holzapfel Wilhelm H. , Bezuidenhout Johannes J. , Kotzé Johannes M.
Published: January 2020

A variety of lactic acid bacteria, isolated from plant surfaces and plant-associated products, were found to be antagonistic to test strains of the phytopathogens
Xanthomonas campestris, Erwinia carotovora
, and
Pseudomonas syringae
. Effective “in vitro” inhibition was found both on agar plates and in broth cultures. In pot trials, treatment of bean plants with a
Lactobacillus plantarum
strain before inoculation with
P. syringae
caused a significant reduction of the disease incidence.
Colonization of the gut of the blue crab (Callinectes sapidus) by Vibrio cholerae
Authors: Huq A , Huq S A , Grimes D J , O'Brien M , Chu K H , Capuzzo J M , Colwell R R
Published: January 2020

Attachment of Vibrio cholerae to the mucosal surface of the intestine is considered to be an important virulence characteristic. Vibrio cholerae, an autochthonous member of brackish water and estuarine bacterial communities, also attaches to crustacea, a significant factor in multiplication and survival of V. cholerae in nature. The ability of V. cholerae to attach to the gut wall of the blue crab (Callinectes sapidus) was examined, and attachment was observed only in the hindgut and not the midgut of crabs, confirming a requirement for chitin in the attachment of V. cholerae to invertebrate and zooplankton surfaces. The new finding of attachment of V. cholerae to the hindgut of crabs may be correlated with the epidemiology and transmission of cholera in the aquatic environment. The crab model may also prove useful in elucidating the mechanism(s) of ion transport in crustacea.
Rapid Assay for In Situ Identification of Coagulase-Positive Staphylococci Recovered by Membrane Filtration from Swimming Pool Water
Authors: Klapes N. Arlene , Vesley Donald
Published: January 2020

A rapid, in situ thermonuclease test that identifies colonies of
Staphylococcus aureus
among staphylococci isolated from swimming pool water by membrane filtration recovery on various selective and differential media is described.
Biogenesis of some antibiotics in the presence of 2-chloroethylphosphonic acid
Authors: Sharma A , Padwal-Desai S R
Published: January 2020

2-Chloroethylphosphonic acid (CEPA) affected both the growth of and antibiotic production in Streptomyces aureofaciens, S. griseus, S. antibioticus, and Penicillium citrinum. Streptomyces strains seemed to be more sensitive to the presence of CEPA in the medium than did the fungus. A decrease in both growth and antibiotic production was observed with a concomitant increase in the concentration of the ethylene-releasing compound in the medium. Higher concentrations of CEPA completely inhibited the growth of the above microorganisms.
Protoplast formation and regeneration of dehydrodivanillin-degrading strains of Fusobacterium varium and Enterococcus faecium
Authors: Chen W , Ohmiya K , Shimizu S
Published: January 2020

Two strains of rumen anaerobes isolated from dehydrodivanillin-degrading cultures were identified as Fusobacterium varium and Enterococcus faecium. These organisms degraded dehydrodivanillin synergistically to 5-carboxymethylvanillin and vanillic acid. Specific conditions for protoplast formation and cell wall regeneration for both bacteria were determined, under strictly anaerobic conditions, to be as follows. The cell wall of each bacterium in yeast extract medium was loosened by adding penicillin G during early log-phase growth. The cell wall of F. varium was lysed by lysozyme (1 mg/ml) in glycerol (0.2 M)-phosphate buffer (0.05 M; pH 7.0). The addition of NaCl (0.08 M) with lysozyme was necessary for lysis of E. faecium in this solution. Almost all cells were converted to protoplasts after 2 h of incubation at 37 degrees C. Regeneration of both protoplasts was 20 to 30% on an agar-containing yeast extract medium.
Effect of Sulfur-Containing Compounds on Growth of
Methanosarcina barkeri
in Defined Medium
Authors: Mazumder Tapan K. , Nishio Naomichi , Fukuzaki Satoshi , Nagai Shiro
Published: January 2020

Methanosarcina barkeri
Fusaro (DSM 804) could grow on methanol in a mineral medium containing cysteine or thiosulfate as the sole sulfur source. Optimum growth occurred at cysteine concentrations of 1 to 2.8 mM and at thiosulfate concentrations of 2.5 to 5 mM. No inhibition of growth was observed even when these concentrations were doubled in the culture medium. Under the optimum cysteine and thiosulfate concentrations, the generation times of the organism were about 8 to 10 and 10 to 12 h, respectively, giving a cell yield of about 0.14 to 0.17 and 0.08 to 0.11 g (dry weight)/g of methanol consumed. The organism metabolized cysteine and thiosulfate during growth, giving rise to sulfide in the culture medium. H
2
S evolution from cysteine and thiosulfate was catalyzed by two enzymes, namely cysteine desulfhydrase and thiosulfate reductase, respectively, as revealed by enzyme assay in the crude cell-free extract of the organism.
Production of
l
-Phenylalanine from Starch by Analog-Resistant Mutants of
Bacillus polymyxa
Authors: Shetty Kalidas , Crawford Don L. , Pometto Anthony L.
Published: January 2020

p
-Fluorophenylalanine-resistant mutants of starch-degrading
Bacillus polymyxa
ATCC 842, generated by ethyl methanesulfonate mutagenesis followed by incubation with caffeine, overproduced small amounts of
l
-phenylalanine (
l
-phe) from starch. A β-2-thienylalanine-resistant mutant (BT
R
-7) derived from
p
-fluorophenylalanine mutant (C-4000 FP
R
-4) and resistant to both
p
-fluorophenylalanine and β-2-thienylalanine produced 0.5 g of
l
-phe and 0.15 g of
l
-tyrosine per liter from 10 g of starch per liter when growing in a minimal medium.
trans
-Cinnamic acid (CA) was also excreted by both mutants, indicating the possibility of
l
-phenylalanine ammonia-lyase-induced deamination of
l
-phe to CA. The amount of
l
-phe-derived CA detected in BT
R
-7 was less compared with mutant C-4000 FP
R
-4. CA production was induced in the parent only when
l
-phe was used as a sole nitrogen source. Time of CA production in the two mutants could be delayed by addition of other nitrogen sources, an indication of possible
l
-phenylalanine ammonia-lyase inhibition or repression. The presence of
l
-phenylalanine ammonia-lyase in
B. polymyxa
mutant C-4000 FP
R
-4 was confirmed by assays of cell-free extracts from cells grown in starch minimal medium containing
l
-phe as the sole nitrogen source. Preliminary studies of the regulation of deoxy-
d
-arabino-heptulosonate-7-phosphate synthase and prephenate dehydratase in the wild-type strain showed that deoxy-
d
-arabino-heptulosonate-7-phosphate synthase was subject to feedback inhibition by
l
-phe,
l
-tyrosine, and
l
-tryptophan. Inhibition by each amino acid was to a similar extent singly or in combination at a 0.5 mM level of each amino acid. Prephenate dehydratase was feedback inhibited by
l
-phe, but not by
l
-tyrosine or
l
-tryptophan or both. In the double analog-resistant mutant BT
R
-7, deoxy-
d
-arabino-heptulosonate-7-phosphate synthase had specific activity similar to that in the wild type, and the enzyme was still subject to feedback inhibition. However, prephenate dehydratase had increased specific activity and it was also insensitive to feedback inhibition by
l
-phe. The overproduction of aromatic amino acids by BT
R
-7 was thought to be due, at least in part, to deregulation of feedback inhibition of prephenate dehydratase. Chorismate mutase was not subject to feedback inhibition in the wild type and was unaffected in the mutant.
Immunological relationships among proteins making up the Bacillus thuringiensis subsp. israelensis crystalline toxin
Authors: Pfannenstiel M A , Couche G A , Ross E J , Nickerson K W
Published: January 2020

The immunological relationships among the proteins of the mosquito larvicidal toxin produced by Bacillus thuringiensis subsp. israelensis have been investigated by using polyclonal antisera specific for the 28-, 70-, and 135-kilodalton proteins. Each of these proteins was immunologically distinct. There was no cross-reaction among the three proteins and the two non-homologous antisera. Treatment of toxin proteins with larval gut enzymes for 20 h identified protease-resistant domains at approximately 65, 38, and 22 kilodaltons. Similar domains were generated by treatment with trypsin and chymotrypsin. Our immunological and kinetic data indicate that the 28-kilodalton protein is degraded successively to protein bands at 26, 25, 23, and 22 kilodaltons, the 70-kilodalton protein is degraded to a protein at 38 kilodaltons, and the 135-kilodalton protein is degraded successively to protein bands at 94, 72, and, probably, 65 kilodaltons. Solubilized toxin possesses two biological activities, larvicidal and general cytolytic (hemolytic). We used nondenaturing gel electrophoresis to show that the hemolytic activity resides in the 28-kilodalton protein. However, higher-molecular-weight proteins are required to achieve the level of toxicity observed in intact toxin.
Affinity Purifications of Aldose Reductase and Xylitol Dehydrogenase from the Xylose-Fermenting Yeast
Pachysolen tannophilus
Authors: Bolen Paul L. , Roth Kelly A. , Freer Shelby N.
Published: January 2020

Although xylose is a major product of hydrolysis of lignocellulosic materials, few yeasts are able to convert it to ethanol. In
Pachysolen tannophilus
, one of the few xylose-fermenting yeasts found, aldose reductase and xylitol dehydrogenase were found to be key enzymes in the metabolic pathway for xylose fermentation. This paper presents a method for the rapid and simultaneous purification of both aldose reductase and xylitol dehydrogenase from
P. tannophilus.
Preliminary studies indicate that this method may be easily adapted to purify similar enzymes from other xylose-fermenting yeasts.
Mutagenicity of the Alternaria metabolites altertoxins I, II, and III
Authors: Stack M E , Prival M J
Published: January 2020

The Ames Salmonella typhimurium assay was used to demonstrate that an extract of the mold Alternaria alternata was mutagenic. The mutagenic extract was fractionated, and the Ames test was used to determine which fractions were mutagenic. Subsequently, altertoxins I and II and a new compound referred to as altertoxin III were isolated by liquid chromatography and shown to be hydroxyperylenequinone compounds by mass spectrometry and infrared, ultraviolet, and proton magnetic resonance spectroscopy. Altertoxins I, II, and III were mutagenic to S. typhimurium TA98, TA100, and TA1537 with and without metabolic activation.
Residual effect of storage in an elevated carbon dioxide atmosphere on the microbial flora of rock cod (Sebastes spp.)
Authors: Wang M Y , Ogrydziak D M
Published: January 2020

A residual inhibitory effect on microbial growth due to modified-atmosphere (MA) storage (MA, 80% CO2-20% air) was demonstrated for rock cod fillets stored in MA and transferred to air at 4 degrees C. Results of measurements of CO2 concentrations of the fillets suggested that the residual effect after transfer from MA to air was not due to retention of CO2 at the surface of the fillets but was probably due to the microbial ecology of the system. Lactobacillus spp. and tan Alteromonas spp. (TAN) predominated after 7 and 14 days of storage in MA. During storage in MA, Pseudomonas spp. were inhibited or killed. Following transfer from MA to air, the percentage of the total flora represented by Lactobacillus spp. and TAN bacteria decreased, and 6 days after transfer Pseudomonas spp. were again dominant.
Anaerobic Fermentation of Woody Biomass Pretreated with Supercritical Ammonia
Authors: Weimer P. J. , Chou Y.-C. T.
Published: January 2020

The degradability of ground hardwood by thermophilic anaerobic bacteria (
Clostridium thermocellum
with or without
Thermoanaerobacter
strain B6A) was greatly enhanced by pretreatment of the substrate with supercritical ammonia. Relative to
C. thermocellum
monocultures, cocultures of
C. thermocellum
and
Thermoanaerobacter
strain B6A degraded 1.5-fold more pretreated soft maple but produced 2- to 5-fold more fermentation endproducts because
Thermoanaerobacter
sp. removed reducing sugars produced by
C. thermocellum
during the fermentation. Dry weight losses were not totally accounted for in end products, due to formation of partially degraded material (<0.4 μm diameter wood particles) during the fermentation. One pretreated hardwood, Southern red oak, was fermented poorly because it released soluble inhibitors at the 60°C incubation temperature. Considerable (6- to 11-fold) increases in substrate degradability were also noted for supercritical ammonia-pretreated wood materials fermented in an in vitro rumen digestibility assay. Degradation of pretreated softwoods by either thermophilic or mesophilic fermentation was not measurable under the conditions tested.
Overproduction from a cellulase gene with a high guanosine-plus-cytosine content in Escherichia coli
Authors: O'Neill G P , Kilburn D G , Warren R A , Miller R C
Published: January 2020

A recombinant exoglucanase was expressed in Escherichia coli to a level that exceeded 20% of total cellular protein. To obtain this level of overproduction, the exoglucanase gene coding sequence was fused to a synthetic ribosome-binding site, an initiating ATG, and placed under the control of the leftward promoter of bacteriophage lambda contained on the runaway replication plasmid vector pCP3 (E. Remaut, H. Tsao, and W. Fiers, Gene 22:103-113, 1983). With the exception of an inserted asparagine adjacent to the initiating ATG, the highly expressed exoglucanase is identical to the native exoglucanase. The overproduced exoglucanase can be isolated easily in an enriched form as insoluble aggregates, and exoglucanase activity can be recovered by solubilization of the aggregates in 6 M urea or 5 M guanidine hydrochloride. Since the codon usage of the exoglucanase gene is so markedly different from that of E. coli genes, the overproduction of the exoglucanase in E. coli indicates that codon usage may not be a major barrier to heterospecific gene expression in this organism.
Palladium-Mediated Hydrogenation of Unsaturated Hydrocarbons with Hydrogen Gas Released during Anaerobic Cellulose Degradation
Authors: Mountfort Douglas O. , Kaspar Heinrich F.
Published: January 2020

Among five hydrogenation catalysts, palladium on charcoal was the most reactive one when suspended in anaerobic culture medium, and Lindlar catalyst (Pd on CaCO
3
) was the most reactive one when suspended in the gas phase of culture tubes. Palladium on charcoal in the culture medium (40 to 200 mg 10 ml
−1
) completely inhibited growth of
Neocallimastix frontalis
and partly inhibited
Ruminococcus albus
. Lindlar catalyst (40 to 200 mg per tube) suspended in a glass pouch above the culture medium did not affect the rate of cellulose degradation or the ratio of fermentation products by these organisms. Acetylene added to tubes containing Lindlar catalyst in pouches, and either of the two organisms in monoculture or coculture with
Methanospirillum hungatei
, was reduced to ethylene and then ethane, followed by hydrogen production. Similar results were obtained with 1-pentene. Neither acetylene nor 1-pentene affected cellulose degradation but both inhibited methanogenesis. In the presence of Lindlar catalyst and propylene or 1-butene, fermenter-methanogen cocultures continued to produce methane at the same rate as controls and no olefin reduction occurred. Upon addition of bromoethanesulfonic acid, methanogenesis stopped and olefin reduction took place followed by hydrogen evolution. In a gas mixture consisting of propylene, 1-butene, and 1-pentene, the olefins were reduced at rates which decreased with increasing molecular size. These results demonstrate the technical feasibility of combining in one reactor the volatile fatty acid production by anaerobic digestion with chemical catalyst-mediated reductions, using the valuable by-product hydrogen.
Availability of Ferric Iron for Microbial Reduction in Bottom Sediments of the Freshwater Tidal Potomac River
Authors: Lovley Derek R. , Phillips Elizabeth J. P.
Published: January 2020

The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in the 0- to 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe
3
O
4
and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced, suggesting that mixed Fe(III)-Fe(II) compounds might account for the persistence of oxalate-extractable Fe(III) in the sediments. The availability of microbially reducible Fe(III) in surficial sediments demonstrates that microbial Fe(III) reduction can be important to organic matter decomposition and iron geochemistry. However, the overall extent of microbial Fe(III) reduction is governed by the inability of microorganisms to reduce most of the Fe(III) in the sediment.
Sporulation-associated activation of Bacillus sphaericus larvicide
Authors: Broadwell A H , Baumann P
Published: January 2020

Preparations of the larvicidal crystal from 46-h cultures of Bacillus sphaericus 2362 contain 125-, 110-, 63-, and 43-kilodalton (kDa) proteins (P. Baumann, B. M. Unterman, L. Baumann, A.H. Broadwell, S.J. Abbene, and R.D. Bowditch, J. Bacteriol. 163:738-747, 1985). The 63- and 43-kDa proteins, which have been purified, are not immunologically cross-reactive, and only the 43-kDa protein is toxic to mosquito larvae. Since antigenic determinants of the two smaller proteins have been detected in the higher-molecular-weight proteins (125 and 110 kDa), it has been suggested that the latter are precursors of the 43- and 63-kDa peptides. In the present study, purified 110-kDa protein was found to be toxic to the larvae of Culex pipiens (50% lethal concentration = 115 ng/ml). A luciferase-luciferin assay for intracellular ATP as well as an assay based on the exclusion of Trypan Blue by live cells indicated that the 110-kDa protein had no effect on tissue-culture-grown cells of C. quinquefasciatus, while cells exposed to the 43-kDa protein rapidly lost viability (50% lethal concentration = 54 microgram(s)/ml by the intracellular ATP assay). These findings suggested that the 110-kDa protein and, by extension, the 125-kDa protein are protoxins which are activated during sporulation by cleavage to a 43-kDa toxin. To further investigate the origins and relationships of the crystal proteins of B. sphaericus, we analyzed samples during the growth and sporulation of the culture. Synthesis of crystal proteins was initiated at the end of exponential growth and was completed after about 7 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Ultrastructure and Host Specificity of Bacteriophages of
Streptococcus cremoris, Streptococcus lactis
subsp.
diacetylactis
, and
Leuconostoc cremoris
from Finnish Fermented Milk “Viili”
Authors: Saxelin Maija-Liisa , Nurmiaho-Lassila Eeva-Liisa , Meriläinen Veijo T. , Forsén Raili I.
Published: January 2020

“Viili,” a fermented milk product, has a firm but viscous consistency. It is produced with traditional mesophilic mixed-strain starters, which have various stabilities in dairy practice. Thirteen morphologically different types of phages were found in 90 viili samples studied by electron microscopy. Ten of the phage types had isometric heads with long, noncontractile tails, two had elongated heads with long, noncontractile tails, and one had a unique, very long elongated head with a short tail. Further morphological differences were found in the tail size and in the presence or absence of a collar, a baseplate, and a tail fiber. To find hosts for the industrially significant phages, we examined the sensitivities of 500 bacterial isolates from starters of the viili. Seven of the phages attacked
Streptococcus cremoris
strains, three attacked
S. lactis
subsp.
diacetylactis
strains, and four attacked
Leuconostoc cremoris
strains. Some phages differed only in their host specificity. Hosts were not found for 4 of the 13 morphological types of phages.
Bacterial Growth Rates and Competition Affect Nodulation and Root Colonization by
Rhizobium meliloti
Authors: Li De-Ming , Alexander Martin
Published: January 2020

The addition of streptomycin to nonsterile soil suppressed the numbers of bacterial cells in the rhizosphere of alfalfa (
Medicago sativa
L.) for several days, resulted in the enhanced growth of a streptomycin-resistant strain of
Rhizobium meliloti
, and increased the numbers of nodules on the alfalfa roots. A bacterial mixture inoculated into sterile soil inhibited the colonization of alfalfa roots by
R. meliloti
, caused a diminution in the number of nodules, and reduced plant growth.
Enterobacter aerogenes, Pseudomonas marginalis, Acinetobacter
sp., and
Klebsiella pneumoniae
suppressed the colonization by
R. meliloti
of roots grown on agar and reduced nodulation by
R. meliloti
, the suppression of nodulation being statistically significant for the first three species.
Bradyrhizobium
sp. and “
Sarcina lutea
” did not suppress root colonization nor nodulation by
R. meliloti.
The doubling times in the rhizosphere for
E. aerogenes, P. marginalis, Acinetobacter
sp., and
K. pneumoniae
were less and the doubling times for
Bradyrhizobium
sp. and “
S. lutea
” were greater than the doubling time of
R. meliloti.
Under the same conditions,
Arthrobacter citreus
injured alfalfa roots. We suggest that competition by soil bacteria reduces nodulation by rhizobia in soil and that the extent of inhibition is related to the growth rates of the rhizosphere bacteria.
Metabolism of polyethylene glycol by two anaerobic bacteria, Desulfovibrio desulfuricans and a Bacteroides sp
Authors: Dwyer D F , Tiedje J M
Published: January 2020

Two anaerobic bacteria were isolated from polyethylene glycol (PEG)-degrading, methanogenic, enrichment cultures obtained from a municipal sludge digester. One isolate, identified as Desulfovibrio desulfuricans (strain DG2), metabolized oligomers ranging from ethylene glycol (EG) to tetraethylene glycol. The other isolate, identified as a Bacteroides sp. (strain PG1), metabolized diethylene glycol and polymers of PEG up to an average molecular mass of 20,000 g/mol [PEG 20000; HO-(CH2-CH2-O-)nH]. Both strains produced acetaldehyde as an intermediate, with acetate, ethanol, and hydrogen as end products. In coculture with a Methanobacterium sp., the end products were acetate and methane. Polypropylene glycol [HO-(CH2-CH2-CH2-O-)nH] was not metabolized by either bacterium, and methanogenic enrichments could not be obtained on this substrate. Cell extracts of both bacteria dehydrogenated EG, PEGs up to PEG 400 in size, acetaldehyde, and other mono- and dihydroxylated compounds. Extracts of Bacteroides strain PG1 could not dehydrogenate long polymers of PEG (greater than or equal to 1,000 g/mol), but the bacterium grew with PEG 1000 or PEG 20000 as a substrate and therefore possesses a mechanism for PEG depolymerization not present in cell extracts. In contrast, extracts of D. desulfuricans DG2 dehydrogenated long polymers of PEG, but whole cells did not grow with these polymers as substrates. This indicated that the bacterium could not convert PEG to a product suitable for uptake.
Complete reductive dechlorination and mineralization of pentachlorophenol by anaerobic microorganisms
Authors: Mikesell M D , Boyd S A
Published: January 2020

Anaerobically digested municipal sewage sludge which had been acclimated to monochlorophenol degradation for more than 2 years was shown to degrade pentachlorophenol (PCP). Di-, tri-, and tetrachlorophenols accumulated when PCP was added to the individual acclimated sludges. When the 2-chlorophenol- (2-CP), 3-CP-, and 4-CP-acclimated sludges were mixed in equal volumes, PCP was completely dechlorinated. The same results were obtained in sludge acclimated to the three monochlorophenol isomers simultaneously. With repeated PCP additions, 3,4,5,-trichlorophenol, 3,5-dichlorophenol, and 3-CP accumulated in less than stoichiometric amounts. All chlorinated compounds disappeared after PCP additions were stopped. All chlorinated compounds disappeared after PCP additions were stopped. Incubations with [14C]PCP resulted in 66% of the added 14C being mineralized to 14CO2 and 14CH4. Technical-grade PCP was found to be degraded initially at a rate very similar to that of reagent-grade PCP, but after repeated additions, the technical PCP was degraded more slowly. Pentabromophenol was also rapidly degraded by the mixture of acclimated sludges. These results clearly show the complete reductive dechlorination of PCP by the combined activities of three chlorophenol-degrading populations.
In Vitro Growth of
Acremonium coenophialum
, an Endophyte of Toxic Tall Fescue Grass
Authors: Davis N. D. , Clark E. M. , Schrey K. A. , Diener U. L.
Published: January 2020

Acremonium coenophialum
, an endophytic fungus present in toxic tall fescue grass and seed, grew very slowly or not at all with conventional media and cultural practices. However, a considerable increase in growth was achieved in a relatively dilute medium consisting solely of glucose and yeast extract. The optimal levels of glucose and yeast extract were 3 to 6% and 0.35% (wt/vol), respectively. The addition of salts which lowered the pH suppressed growth. Even when the pH was controlled, the addition of KH
2
PO
4
at a level of 3.2% or more greatly inhibited growth.
A. coenophialum
grew better in shake culture than in stationary culture. The optimal temperature was 23°C, and the optimal pH was 6.5.
Combined Determination of Poly-β-Hydroxyalkanoic and Cellular Fatty Acids in Starved Marine Bacteria and Sewage Sludge by Gas Chromatography with Flame Ionization or Mass Spectrometry Detection
Authors: Odham Göran , Tunlid Anders , Westerdahl Gunilla , Mårdén Per
Published: January 2020

Extraction of lipids from bacterial cells or sewage sludge samples followed by simple and rapid extraction procedures and room temperature esterification with pentafluorobenzylbromide allowed combined determinations of poly-β-hydroxyalkanoate constituents and fatty acids. Capillary gas chromatography and flame ionization or mass spectrometric detection was used. Flame ionization permitted determination with a coefficient of variation ranging from 10 to 27% at the picomolar level, whereas quantitative chemical ionization mass spectrometry afforded sensitivities for poly-β-hydroxyalkanoate constituuents in the attomolar range. The latter technique suggests the possibility of measuring such components in bacterial assemblies with as few as 10
2
cells. With the described technique using flame ionization detection, it was possible to study the rapid formation of poly-β-hydroxyalkanoate during feeding of a starved marine bacterium isolate with a complex medium or glucose and correlate the findings to changes in cell volumes. Mass spectrometric detection of short β-hydroxy acids in activated sewage sludge revealed the presence of 3-hydroxybutyric, 3-hydroxyhexanoic, and 3-hydroxyoctanoic acids in the relative proportions of 56, 5 and 39%, respectively. No odd-chain β-hydroxy acids were found.
Effects of Flow Cytometric Analysis and Cell Sorting on Photosynthetic Carbon Uptake by Phytoplankton in Cultures and from Natural Populations
Authors: Rivkin Richard B. , Phinney David A. , Yentsch Clarice M.
Published: January 2020

Photosynthetic rates of phytoplankton were significantly lower after analysis by flow cytometry (FCM) than before. Exposure to the laser beam during the sorting process caused significant physiological damage. The cellular content of a radiolabel accumulated prior to FCM was not affected by FCM. Although it may not be possible to use FCM to preconcentrate cells for further physiological studies, samples may be incubated with stable or radioactive isotopes and then analyzed by FCM.
Semienclosed Tube Cultures of Bean Plants (
Phaseolus vulgaris
L.) for Enumeration of
Rhizobium phaseoli
by the Most-Probable-Number Technique
Authors: Araujo Ricardo S. , Maya-Flores Jaime , Barnes-McConnell Deborah , Yokoyama Charles , Dazzo Frank B. , Bliss Fredrick A.
Published: January 2020

The semienclosed tube culture technique of Gibson was modified to permit growth of common bean (
Phaseolus vulgaris
L.) roots in humid air, enabling enumeration of the homologous (nodule forming) symbiont,
Rhizobium phaseoli
, by the most-probable-number plant infection method. A bean genotype with improved nodulation characteristics was used as the plant host. This method of enumeration was accurate when tubes were scored 3 weeks after inoculation with several
R. phaseoli
strains diluted from aqueous suspensions, peat-based inoculants, or soil. A comparison of population sizes obtained by most-probable-number tube cultures and plate counts indicated that 1 to 3 viable cells of
R. phaseoli
were a sufficient inoculant to induce nodule formation.
Presence of Aspergillus flavus in developing cotton bolls and its relation to contamination of mature seeds
Authors: Klich M A
Published: January 2020

Aspergillus flavus spores were dusted onto the involucral nectaries of cotton flowers. The fungus was present in 20 to 58% of the immature bolls harvested 25 or 35 days after anthesis. Among similarly inoculated bolls fully matured either in the field or under sterile conditions at ambient temperatures after excision from the plants, only 3 to 14% contained A. flavus in the seeds. There was no significant difference in the numbers of contaminated bolls between the excised and field-matured treatments. It is concluded that A. flavus is present in developing cotton bolls before dehiscence, but its presence does not ensure infection of mature seeds, and that excision does not reduce A. flavus contamination if the bolls are maintained at ambient temperatures.
Enrichment for Hydrogen-Oxidizing
Acinetobacter
spp. in the Rhizosphere of Hydrogen-Evolving Soybean Root Nodules
Authors: Wong Tit-Yee , Graham Lennox , O'Hara Eileen , Maier Robert J.
Published: January 2020

Field soybean plants were inoculated with Hup
+
wild-type or H
2
uptake-negative (Hup
−
) mutants of
Bradyrhizobium japonicum
. For two consecutive summers we found an enrichment for acinetobacters associated with the surfaces of the H
2
-evolving nodules. Soybean root nodules that evolved H
2
had up to 12 times more
Acinetobacter
spp. bacteria associated with their surfaces than did nodules incapable of evolving H
2
. All of the newly isolated strains identified as
Acinetobacter
obtained from the surfaces of root nodules, as well as known established
Acinetobacter
strains, were capable of oxidizing H
2
, a property not previously described for this alkane-degrading soil bacterium.
Autecology in Rhizospheres and Nodulating Behavior of Indigenous
Rhizobium trifolii
Authors: Demezas David H. , Bottomley Peter J.
Published: January 2020

Indigenous serotype 1-01 of
Rhizobium trifolii
occupied significantly fewer nodules (6%) on plants of soil-grown noninoculated subterranean clover (
Trifolium subterraneum
L.) cv. Woogenellup than on cv. Mt. Barker (36%) sampled at the flowering stage of growth. Occupancy by indigenous serotype 2-01, was not significantly different on the two cultivars (16 and 26%). Serotype-specific, fluorescent-antibody conjugates were synthesized and used to enumerate the indigenous serotypes in host (clovers) and nonhost (annual rye-grass,
Lolium multiflorum
L.) rhizospheres and in nonplanted soil. The form and concentration of Ca
2+
in the flocculating mixture and the presence of phosphate anions in the extracting solution were both critical for enumerating
R. trifolii
in Whobrey soil. The two serotypes were present in similar numbers in nonplanted soil (ca. 10
6
per g of soil) and each represented ca. 10% of the total
R. trifolii
population. Although host rhizospheres did not preferentially stimulate either serotype, the mean population densities of serotype 2-01 were significantly greater (
P
= 0.05) than those of serotype 1-01 in clover rhizospheres on 8 of 14 samplings made between the time of seeding and the appearance of nodules (day 12). In this experiment, and in contrast to our earlier findings, serotype 1-01 occupied significantly fewer (
P
≤ 0.05) of the nodules (7 to 16%) on both cultivars than serotype 2-01 (51%) when sampled at 4 weeks. Differences between cultivars became apparent as the plants matured. There was a threefold increase (7 to 21%) in nodules occupied by serotype 1-01 on cv. Mt. Barker between 4 and 16 weeks. This was accompanied by increases in nodules coinhabited by both nonidentifiable occupants and either serotype 1-01 (0 to 20%) or 2-01 (11 to 51%). No increases in either of these parameters were observed on cv. Woogenellup.
Interstrain Competition between Representatives of Indigenous Serotypes of
Rhizobium trifolii
Authors: Demezas David H. , Bottomley Peter J.
Published: January 2020

The symbiotic characteristics of
Rhizobium trifolii
strains 1-01 and 2-01 were evaluated both individually and in various combinations on two cultivars (Mt. Barker and Woogenellup) of subterranean clover (
Trifolium subterraneum
L.). Nodules were observed on day 8 independent of cultivar or strain. Cultivar differences were measured in nodulating efficiency by 1-01 since 54% of the primary nodules were formed on cv. Mt. Barker and only 15% were formed on cv. Woogenellup in the zone above, or 1 cm below, the root tip location at the time of inoculation. The percentage of nodules formed in this zone by 2-01 was similar on both cultivars (31 to 32%). When mixtures of strains 1-01 and 2-01 (230:1 and 1:20) were used to inoculate plants, >90% of the nodules on both cultivars were occupied by the more abundant strain in the inoculum regardless of sampling date (4 or 8 weeks). In contrast, large percentages of nodules on 4-week-old plants of both cultivars exposed to a 5:1 inoculum mixture were doubly occupied (64 and 74%). By week 8 these values had decreased significantly (
P
≤ 0.01) and were accompanied by large increases in the percentage of nodules occupied by either strain 1-01 alone (1 to 65%) on cv. Mt. Barker or 2-01 alone (4 to 49%) on cv. Woogenellup. The superior (cv. Mt. Barker) and inferior (cv. Woogenellup) symbiotic performance of plants inoculated with the 5:1 mixture correlated more closely with the 8-week than the 4-week nodule occupancy data. Primary nodule occupancy by 1-01 and 2-01 was significantly influenced by changes in the inoculum ratios of 1-01/2-01 from 5.7:1 to 0.67:1 on cv. Mt. Barker and from 1.9:1 to 0.67:1 on cv. Woogenellup. Despite evidence for extensive proliferation of the inoculant strains on the rhizoplanes, no evidence was obtained for either interstrain antagonism or selective proliferation as a valid reason to explain the outcome of primary nodulation.