bluuebunny/crossref_metadata_2025 huggingface dataset:
Kraft Pulp Bleaching and Delignification by Dikaryons and Monokaryons of
Trametes versicolor
Authors: Addleman Katherine , Archibald Frederick
Published: January 2020

The ability of 10 dikaryotic and 20 monokaryotic strains of
Trametes
(
Coriolus
)
versicolor
to bleach and delignify hardwood and softwood kraft pulps was assessed. A dikaryon (52P) and two of its mating-compatible monokaryons (52J and 52D) derived via protoplasting were compared. All three regularly bleached hardwood kraft pulp more than 20 brightness points (International Standards Organization) in 5 days and softwood kraft pulp the same amount in 12 days. Delignification (kappa number reduction) by the dikaryon and the monokaryons was similar, but the growth of the monokaryons was slower. Insoluble dark pigments were commonly found in the mycelium, medium, and pulp of the dikaryon only. Laccase and manganese peroxidase (MnP) but not lignin peroxidase activities were secreted during bleaching by all three strains. Their laccase and MnP isozyme patterns were compared on native gels. No segregation of isozyme bands between the monokaryons was found. Hardwood kraft pulp appeared to adsorb several laccase isozyme bands. One MnP isozyme (pI, 3.2) was secreted in the presence of pulp by all three strains, but a second (pI, 4.9) was produced only by 52P. A lower level of soluble MnP activity in one monokaryon (52D) was associated with reduced bleaching ability and a lower level of methanol production. Since monokaryon 52J bleached pulp better than its parent dikaryon 52P, especially per unit of biomass, this genetically simpler monokaryon will be the preferred subject for further genetic manipulation and improvement of fungal pulp biological bleaching.
Stereospecificity of Microbial Hydrations of Oleic Acid to 10-Hydroxystearic Acid
Authors: Yang Wei , Dostal Larry , Rosazza John P. N.
Published: January 2020

We recently described a simple method for ascertaining the stereochemical purities of hydroxy fatty acids (S. H. El-Sharkawy, W. Yang, L. Dostal, and J. P. N. Rosazza, Appl. Environ. Microbiol. 58:2116-2122, 1992) based on the
1
H-nuclear magnetic resonance spectral analysis of diastereomeric
S
-(+)-
O
-acetylmandelate esters of hydroxystearates. This report describes the stereochemistries of microbial hydrations of oleic acid to 10-hydroxystearic acid by
Nocardia aurantia
(also known as
Rhodococcus rhodochrous
) ATCC 12674,
Nocardia restrictus
ATCC 14887,
Mycobacterium fortuitum
UI-53387,
Pseudomonas
species strain NRRL-2994,
Pseudomonas
species strain NRRL B-3266, and baker's yeast. 10(
R
)-hydroxystearic acid isolated from
Pseudomonas
species strain NRRL-2994 was the standard for use in the
1
H-nuclear magnetic resonance spectral technique to permit simple assignments of the absolute configurations of 10-hydroxystearic acid produced by different microorganisms. While the
R. rhodochrous
ATCC 12674-mediated hydration of oleic acid gave mixtures of enantiomers 10(
R
)-hydroxystearic acid and 10(
S
)-hydroxystearic acid,
Pseudomonas
species strain NRRL-B-3266 produced optically pure 10(
R
)-hydroxystearic acid. The remaining microorganisms stereoselectively hydrated oleic acid to 10(
R
)-hydroxystearic acid containing between 2 and 18% of the contaminating 10(
S
)-hydroxystearic acid.
Biosynthesis of the lantibiotic subtilin is regulated by a histidine kinase/response regulator system
Authors: Klein C , Kaletta C , Entian K D
Published: January 2020

Subtilin is a lanthionine-containing peptide antibiotic (lantibiotic) which is produced by Bacillus subtilis ATCC 6633. Upstream from the structural gene of subtilin, spaS, three genes (spaB, spaT, and spaC) which are involved in the biosynthesis of subtilin have been identified (C. Klein, C. Kaletta, N. Schnell, and K.-D. Entian, Appl. Environ. Microbiol. 58:132-142, 1992). By using a hybridization probe specific for these genes, the DNA region downstream from spaS was isolated. Further subcloning revealed a 5.2-kb KpnI-HindIII fragment on which two open reading frames, spaR and spaK, were identified approximately 3 kb downstream from spaS. The spaR gene encodes an open reading frame of 220 amino acids with a predicted molecular mass of 25.6 kDa. SpaR shows 35% similarity to positive regulatory factors OmpR and PhoB. The spaK gene encodes an open reading frame of 387 amino acids with a predicted molecular mass of 44.6 kDa and was highly similar to histidine kinases previously described (PhoM, PhoR, and NtrB). Hydrophobicity blots suggested two membrane-spanning regions. Thus, spaR and spaK belong to a recently identified family of environmentally responsive regulators. These results indicated a regulatory function of spaR and spaK in subtilin biosynthesis. Indeed, batch culture experiments confirmed the regulation of subtilin biosynthesis starting in the mid-logarithmic growth phase and reaching its maximum in the early stationary growth phase. Gene deletions within spaR and spaK yielded subtilin-negative mutants, which confirms that subtilin biosynthesis is under the control of a two-component regulatory system.(ABSTRACT TRUNCATED AT 250 WORDS)
Biological Control of
Agrobacterium tumefaciens
, Colonization, and pAgK84 Transfer with
Agrobacterium radiobacter
K84 and the Tra
-
Mutant Strain K1026
Authors: Vicedo Begonya , Peñalver Ramón , Asins María José , López María M.
Published: January 2020

The efficacies of
Agrobacterium radiobacter
K84 and K1026 in root colonization, crown gall control, and plasmid transfer were compared. Levels of root colonization by K84 and K1026 of Montclar and Nemaguard peach seedlings were similar during the 21 days of the experiment. Four strains of
A. tumefaciens
bv. 1 were used for soil inoculations in biological control experiments on GF677 and Adafuel peach × almond rootstocks; two were sensitive and two were resistant to agrocin 84. Both strains K84 and K1026 were very efficient in controlling the sensitive strains, but some tumors appeared with both treatments. In the biocontrol of resistant strains, no galls were observed in K1026-treated plants, but some K84-treated plants had galls. Recovery of agrobacteria from galls in experiments with sensitive and resistant strains showed that all of the isolates from the controls or K1026-treated plants and most of the isolates from K84-treated plants had the same characteristics as the inoculated strains. Nine isolates from the K84-treated plants growing in soil inoculated with one resistant strain were virulent and produced agrocin 84. These isolates had a plasmid that hybridized with a probe prepared with the
Bam
HI C fragment from pAgK84. These results show the efficiency of K1026 in biocontrol of agrocin 84-sensitive and -resistant strains of
A. tumefaciens
and suggest the use of K1026 as a safer organism than K84 for biological control of crown gall.
Strains of
Corynebacterium glutamicum
with Different Lysine Productivities May Have Different Lysine Excretion Systems
Authors: Bröer Stefan , Eggeling Lothar , Krämer Reinhard
Published: January 2020

The lysine excretion systems of three different lysine-producing strains of
Corynebacterium glutamicum
were characterized in intact cells. Two strains (DG 52-5 and MH 20-22B) are lysine producers of different efficiency. They were bred by classical mutagenesis and have a feedback-resistant aspartate kinase. The third strain (KK 25) was constructed from the wild type by introducing the feedback-resistant aspartate kinase gene of strain MH 20-22B into its genome. The three strains were shown to possess different excretion systems. Export in strain KK 25 is much slower than in the two mutants. The differences between the two lysine-producing strains are more subtle.

K
m

and

V
max

are similar, but pH dependence and membrane potential dependence reveal differences in the intrinsic properties of the carrier system.
Quantitative observations of heterogeneities in Pseudomonas aeruginosa biofilms
Authors: Stewart P S , Peyton B M , Drury W J , Murga R
Published: January 2020

Heterogeneity in a Pseudomonas aeruginosa biofilm was quantified by measuring distributions of thickness in biofilm samples and a distribution of particle sizes in effluent samples. The mean steady-state thickness was approximately 33 microns, but individual measurements ranged from 13.3 to 60.0 microns. Particles exceeding 100 microns3 were observed in the reactor effluent. The results reveal a rough biofilm surface and indicate that most biomass detaches in the form of multicellular particles.
Cloning and sequencing of pepC, a cysteine aminopeptidase gene from Lactococcus lactis subsp. cremoris AM2
Authors: Chapot-Chartier M P , Nardi M , Chopin M C , Chopin A , Gripon J C
Published: January 2020

A gene coding for an aminopeptidase (PepC) from Lactococcus lactis subsp. cremoris AM2 was cloned by complementation of an Escherichia coli mutant lacking aminopeptidase activity. The nucleotide sequence was determined. A portion of the predicted amino acid sequence of PepC (436 amino acids) showed strong homology to the active site of cysteine proteases. No signal sequence was found, indicating an intracellular location of the enzyme.
Evidence for catabolite inhibition in regulation of pentose utilization and transport in the ruminal bacterium Selenomonas ruminantium
Authors: Strobel H J
Published: January 2020

Pentose sugars can be an important energy source for ruminal bacteria, but there has been relatively little study regarding the regulation of pentose utilization and transport by these organisms. Selenomonas ruminantium, a prevalent ruminal bacterium, actively metabolizes xylose and arabinose. When strain D was incubated with a combination of glucose and xylose or arabinose, the hexose was preferentially utilized over pentoses, and similar preferences were observed for sucrose and maltose. However, there was simultaneous utilization of cellobiose and pentoses. Continuous-culture studies indicated that at a low dilution rate (0.10 h-1) the organism was able to co-utilize glucose and xylose. This co-utilization was associated with growth rate-dependent decreases in glucose phosphotransferase activity, and it appeared that inhibition of pentose utilization was due to catabolite inhibition by the glucose phosphotransferase transport system. Xylose transport activity in strain D required induction, while arabinose permease synthesis did not require inducer but was subject to repression by glucose. Since an electrical potential or a chemical gradient of protons drove xylose and arabinose uptake, pentose-proton symport systems apparently contributed to transport.
Isolation and purification of propionicin PLG-1, a bacteriocin produced by a strain of Propionibacterium thoenii
Authors: Lyon W J , Glatz B A
Published: January 2020

Production of propionicin PLG-1 by Propionibacterium thoenii P127 was pH dependent, with maximal activity detected in supernatants of cultures grown at pH 7.0 Propionicin PLG-1 was purified by ion-exchange chromatography and isoelectric focusing. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of propionicin PLG-1 purified through isoelectric focusing resolved a protein band with a molecular weight of 10,000. Propionicin PLG-1 was bactericidal to sensitive cells, demonstrating single-hit kinetics. The producing strain harbored a single plasmid (pLG1) with an approximate size of 250 kb. Preliminary data indicate that both propionicin PLG-1 and immunity to the bacteriocin are encoded on the chromosome. Exposure of strain P127 to acriflavine or to N-methyl-N'-nitro-N-nitrosoguanidine yielded isolates that no longer produced bacteriocin activity and isolates that were cured of the plasmid. However, loss of bacteriocin production was not correlated with loss of the plasmid. Isolates cured of the plasmid were phenotypically identical to plasmid-bearing cells in fermentation patterns, pigment production, and growth characteristics.
In Vitro Stimulation of Forage Fiber Degradation by Ruminal Microorganisms with
Aspergillus oryzae
Fermentation Extract
Authors: Varel Vincent H. , Kreikemeier Kelly K. , Jung Hans-Joachim G. , Hatfield Ronald D.
Published: January 2020

Aspergillus oryzae
fermentation extract (Amaferm) was evaluated for its ability to influence degradation of brome grass and switchgrass fiber fractions by mixed ruminal microorganisms in vitro. Addition of Amaferm at a concentration of 0.067 mg/ml, which is approximately the concentration found in the rumen ecosystem (0.06 mg/ml), increased the degradation of brome grass neutral detergent fiber (NDF) by 28% after fermentation for 12 h (
P
< 0.01), but had no effect after fermentation for 24 or 48 h. The levels of degradation of both the cellulose and hemicellulose fractions were increased after fermentation for 12 h (
P
< 0.01). Additions of 0.08 and 8% (vol/vol) Amaferm filtrate (12.5 g/100 ml) stimulated degradation of switchgrass NDF by 12 and 24% (
P
< 0.01), respectively, after fermentation for 12 h; when 80% filtrate was added, degradation was decreased by 38%. The concentrations of total anaerobes in culture tubes containing 80% filtrate were 5 times greater than the concentrations in the controls; however, the concentrations of cellulolytic organisms were 3.5 times lower than the concentrations in the controls (
P
< 0.05). These results suggested that the filtrate contained high concentrations of soluble substrate which did not allow the cellulolytic organisms to compete well with other populations. The remaining concentrations of esterified
p
-coumaric and ferulic acids were lower at 12 h in NDF residues obtained from fermentation mixtures supplemented with Amaferm. Because the total anaerobes were not inhibited in fermentation mixtures containing Amaferm, antibiotics are unlikely to be involved as a mode of action for increasing NDF degradation. The possibility that Amaferm contains enzymes (possibly esterases) that may play a role in stimulating the rate of fiber degradation by mixed ruminal microorganisms by removal of plant cell wall phenolic acid esters is discussed.
Molecular breeding of a biotin-hyperproducing Serratia marcescens strain
Authors: Sakurai N , Imai Y , Masuda M , Komatsubara S , Tosa T
Published: January 2020

We previously reported that an acidomycin-resistant mutant of Serratia marcescens Sr41, SB304, and a mutant that was derived from SB304 and was resistant to a higher concentration of acidomycin, SB412, produced 5 and 20 mg of D-biotin, respectively, per liter of a medium containing sucrose and urea (N. Sakurai, Y. Imai, M. Masuda, S. Komatsubara, and T. Tosa, Appl. Environ. Microbiol. 59:2857-2863, 1993). In order to increase the productivity of D-biotin, the biotin (bio) operons were cloned from strains SB412, SB304, and 8000 (wild-type strain), and pLGM412, pLGM304, and pLGW101, respectively, were obtained through subcloning. These plasmids harbored 7.2-kb DNA fragments coding for the bioABFCD genes on a low-copy-number vector and were introduced into SB304, SB412, and 8000. Among the resulting recombinant strains, SB412(pLGM304) exhibited the highest D-biotin production (200 mg/liter) in the production medium. The plasmid was stably maintained in cells. Unexpectedly, SB412(pLGM412) grew very slowly, and the D-biotin productivity of this recombinant strain was not evaluated because pLGM412 was unstable.
Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in soils
Authors: Mergaert J , Webb A , Anderson C , Wouters A , Swings J
Published: January 2020

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or a copolymer of 90% 3-hydroxybutyric acid and 10% 3-hydroxyvaleric acid was studied in soils incubated at a constant temperature of 15, 28, or 40 degrees C for up to 200 days. In addition, hydrolytic degradation in sterile buffer at temperatures ranging from 4 to 55 degrees C was monitored for 98 days. Degradation was measured through loss of weight (surface erosion), molecular weight, and mechanical strength. While no weight loss was recorded in sterile buffer, samples incubated in soils were degraded at an erosion rate of 0.03 to 0.64% weight loss per day, depending on the polymer, the soil, and the incubation temperature. The erosion rate was enhanced by incubation at higher temperatures, and in most cases the copolymer lost weight at a higher rate than the homopolymer. The molecular weights of samples incubated at 40 degrees C in soils and those incubated at 40 degrees C in sterile buffer decreased at similar rates, while the molecular weights of samples incubated at lower temperatures remained almost unaffected, indicating that molecular weight decrease is due to simple hydrolysis and not to the action of biodegrading microorganisms. The degradation resulted in loss of mechanical properties. From the samples used in the biodegradation studies, 295 dominant microbial strains capable of degrading P (3HB) and the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer in vitro were isolated and identified.(ABSTRACT TRUNCATED AT 250 WORDS)
Cytochrome Oxidase: Subcellular Distribution and Relationship to Nitrogenase Expression in the Nonheterocystous Marine Cyanobacterium
Trichodesmium thiebautii
Authors: Bergman B. , Siddiqui P. J. A. , Carpenter E. J. , Peschek G. A.
Published: January 2020

Immunochemical labeling was used to study the subcellular distribution of cytochrome oxidase, a respiratory protein, in
Trichodesmium thiebautii
. The protein was found associated with both cytoplasmic and thylakoid membranes. About a sixfold variation in the protein content (gold particle count) was found among
Trichodesmium
cells within a single colony. Double labeling was performed with cytochrome oxidase and nitrogenase antisera. Regression analysis of gold particle counts per unit of cell area of cytochrome oxidase and nitrogenase showed a positive correlation (
r
2
= 0.911); cells with higher nitrogenase levels also had higher levels of cytochrome oxidase. The parallel expression of two proteins suggests that respiratory oxygen uptake may be involved in nitrogenase protection (respiratory protection) in
Trichodesmium
spp.
Stimulatory effect of cooling tower biocides on amoebae
Authors: Srikanth S , Berk S G
Published: January 2020

Two species of amoebae were isolated from the cooling tower of an air-conditioning system and examined for effects of exposure to four cooling tower biocides, a thiocarbamate compound, tributyltin neodecanoate mixed with quaternary ammonium compounds, another quaternary ammonium compound alone, and an isothiazolin derivative. The amoebae isolated were Acanthamoeba hatchetti and a Cochliopodium species. Two other amoeba cultures, an A. hatchetti culture and Cochliopodium bilimbosum, were obtained from the American Type Culture Collection (ATCC) and were also tested. The cooling tower isolates were more resistant to most of the biocides than the ATCC isolates were. The isothiazolin derivative was the least inhibitory to all four amoeba isolates, and tributyltin neodecanoate mixed with quaternary ammonium compounds was the most inhibitory to three of the four isolates. After exposure to lower concentrations of the biocides, including for one strain the manufacturer's recommended concentration of one biocide, the cooling tower amoeba populations increased significantly compared with unexposed controls, whereas the ATCC isolates were not stimulated at any of the concentrations tested. In some cases, concentrations which stimulated cooling tower amoebae inhibited the growth of the ATCC isolates. These results suggest that cooling tower amoebae may adapt to biocides, underscoring the need to use freshly isolated cooling tower organisms rather than organisms from culture collections for testing the efficacy of such biocides. The stimulatory effect of biocides on amoeba populations is an alarming observation, since these organisms may be reservoirs for legionellae. Biocides used to control microbial growth may actually enhance populations of host organisms for pathogenic bacteria.
Reductive dehalogenation of chlorinated benzenes and toluenes under methanogenic conditions
Authors: Ramanand K , Balba M T , Duffy J
Published: January 2020

The anaerobic metabolism of chlorinated benzenes and toluenes was evaluated in soil slurry microcosms under methanogenic conditions. A mixture of hexachlorobenzene, pentachlorobenzene, and 1,2,4-trichlorobenzene (TCB) in soil slurries was biotransformed through sequential reductive dechlorination to chlorobenzene (CB). The metabolic pathway for hexachlorobenzene and pentachlorobenzene decay proceeded via 1,2,3,4-tetrachlorobenzene (TTCB)-->1,2,3-TCB + 1,2,4-TCB-->1,2-dichlorobenzene (DCB) + 1,4-DCB-->CB. In a mineral salts medium, the CB-adapted soil microorganisms dehalogenated individual 1,2,4,5-TTCB, 1,2,3,4-TTCB, 1,2,3-TCB, and 1,2,4-TCB but not 1,2,3,5-TTCB or 1,3,5-TCB. Similarly, a mixture of 2,3,6-trichlorotoluene (TCT), 2,5-dichlorotoluene (DCT), and 3,4-DCT was reductively dechlorinated in soil slurries to predominantly toluene and small amounts of 2-, 3-, and 4-chlorotoluene (CT). Toluene was further degraded. When tested individually in a mineral salts medium, the CT-adapted soil microorganisms dechlorinated several TCT and DCT isomers. Key metabolic routes for TCTs followed: 2,3,6-TCT-->2,5-DCT-->2-CT-->toluene; 2,4,5-TCT-->2,5-DCT + 3,4-DCT-->3-CT + 4-CT-->toluene. Among DCTs tested, 2,4-DCT and 3,4-DCT were dechlorinated via the removal of o- and m-chlorine, respectively, to 4-CT and subsequently to toluene via p-chlorine removal. Likewise, 2,5-DCT was dechlorinated via 2-CT to toluene. Evidently, microorganisms capable of removing o-, m-, and p-chlorines are present in the soil system, as reflected by the dechlorination of different isomers of CBs and CTs to CB and toluene, respectively. These findings help clarify the metabolic fate of chlorinated benzenes and toluenes in anaerobic environments.
Microscale Distribution of Nitrification Activity in Sediment Determined with a Shielded Microsensor for Nitrate
Authors: Jensen Kim , Revsbech Niels Peter , Nielsen Lars Peter
Published: January 2020

Microprofiles of O
2
and NO
3
-
were measured simultaneously in freshwater sediment with microsensors which were completely free from electrical interference because of coaxial designs. Depth profiles of nitrification (NO
3
-
production) and denitrification (NO
3
-
consumption) were subsequently determined by computer simulation of the measured microprofiles. The nitrifying bacterial community responded very quickly to changes in environmental conditions, and new steady-state microprofiles of O
2
and NO
3
-
were usually approached within a few hours after perturbation. Nitrification started quickly after introduction of O
2
in previously anoxic layers, suggesting prolonged survival of the nitrifiers during anaerobiosis. Changes in the availability of O
2
and NH
4
+
greatly affected the nitrification profile, and there was a high rate of coupled nitrification-denitrification under conditions in which nitrification occurred right above the oxic-anoxic interface. Addition of C
2
H
2
rapidly removed the NO
3
-
peaks, indicating that NO
3
-
production was due mainly to autotrophic nitrification.
Mobile bacteria and transport of polynuclear aromatic hydrocarbons in porous media
Authors: Jenkins M B , Lion L W
Published: January 2020

Sorption of hydrophobic pollutants such as polynuclear aromatic hydrocarbons (PAHs) to soil and aquifer materials can severely retard their mobility and the time course of their removal. Because mobile colloids may enhance the mobility of hydrophobic pollutants in porous media and indigenous bacteria are generally colloidal in size, bacterial isolates from soil and subsurface environments were tested for their ability to enhance the transport of phenanthrene, a model PAH, in aquifer sand. Batch isotherm experiments were performed to measure the ability of selected bacteria, including 14 isolates from a manufactured gas plant waste site, to sorb 14C-phenanthrene and to determine whether the presence of the suspended cells would reduce the distribution coefficient (Kd) for phenanthrene with the sand. Column experiments were then used to test the mobility of isolates that reduced the Kd for phenanthrene and to test the most mobile isolate for its ability to enhance the transport of phenanthrene. All of the isolates tested passively sorbed phenanthrene, and most but not all of the isolates reduced the Kd for phenanthrene. Some, but not all, of those isolates were mobile in column experiments. The most mobile isolate significantly enhanced the transport of phenanthrene in aquifer sand, reducing its retardation coefficient by 25% at a cell concentration of approximately 5 x 10(7) ml-1. The experimental results demonstrated that mobile bacteria may enhance the transport of PAHs in the subsurface.
Nutritional requirements for synthesis of heat-stable enterotoxin by Yersinia enterocolitica
Authors: Amirmozafari N , Robertson D C
Published: January 2020

A defined medium that supported the growth of and synthesis of heat-stable enterotoxin (YST) by clinical isolates of Yersinia enterocolitica at levels equivalent to those observed in a complex Trypticase soy broth-0.6% yeast extract medium was developed. The defined medium contained four amino acids (L-methionine, L-glutamic acid, glycine, and L-histidine), inorganic salts, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer, and potassium gluconate as the carbon source. Methionine was required for growth by most strains of Y. enterocolitica used in this study; thus, it was not possible to determine whether it was also required for the synthesis of YST. The other 17 amino acids commonly found in proteins did not stimulate the synthesis of YST when added to the defined medium. The yield of YST observed with other carbon sources fermented by Y. enterocolitica ranged from 4- to 26-fold lower than that obtained with potassium gluconate. The divalent cations Ca2+ and Mn2+ had no effect on the synthesis of YST; however, concentrations of Fe2+ above 10 microM inhibited the synthesis of the enterotoxin. The addition of a mixture of pyrimidines containing thymine, cytosine, and uracil, each at a concentration of 2.0 mM, stimulated the synthesis of YST by 10 to 15%, whereas a mixture of adenine and guanine, each at a similar concentration, inhibited the synthesis of YST. Vitamins had no effect on the amounts of YST produced by Y. enterocolitica strains grown in the defined medium.(ABSTRACT TRUNCATED AT 250 WORDS)
Growth and enrichment of pentachlorophenol-degrading microorganisms in the nutristat, a substrate concentration-controlled continuous culture
Authors: Rutgers M , Bogte J J , Breure A M , van Andel J G
Published: January 2020

The nutristat, a substrate concentration-controlled continuous culture, was used to grow pentachlorophenol (PCP)-degrading microorganisms. The PCP concentration control system consisted of on-line measurement of the PCP concentration in the culture vessel with a tangential filter and a flowthrough spectrophotometer. With PCP concentrations between 45 and 77 microM, a stable situation was established in the nutristat, with an average dilution rate of 0.035 +/- 0.003 h-1. Compared with those of fed-batch cultures and chemostat cultures, the growth rates of microorganisms in the PCP nutristat were significantly higher, leading to considerable time savings in the enrichment procedure. In addition, PCP accumulation to severe inhibitory levels in the culture is prevented because the set point determines the (maximum) PCP concentration in the culture. The use of the nutristat as a tool for the growth of bacteria that degrade toxic compounds is discussed.
Influence of organic nutrients and cocultures on the competitive behavior of 1,2-dichloroethane-degrading bacteria
Authors: van den Wijngaard A J , van der Kleij R G , Doornweerd R E , Janssen D B
Published: January 2020

The effects of organic nutrients and cocultures on substrate removal by and competitive behavior of 1,2-dichloroethane-degrading bacteria were investigated. Xanthobacter autotrophicus GJ10 needed biotin for optimal growth on 1,2-dichloroethane. In continuous culture, dilution of biotin to a concentration below 0.2 nM resulted in washout. Growth could be restored by inoculation with the 2-chloroethanol utilizer Pseudomonas sp. strain GJ1, leading to a new steady state in which about 1% of the mixed culture consisted of cells of strain GJ1. This indicates that strain GJ1 excreted biotin or a precursor for its synthesis. Inoculation of the mixed culture with Ancylobacter aquaticus AD25 did not result in washout of strain GJ10, although strain AD25 has a 10-fold-lower Ks for growth on 1,2-dichloroethane. Strain AD25 did not become dominant because of the lack of vitamins, which are necessary for its optimal growth. The results indicate that medium composition and the presence of other species strongly influence the effect of substrate limitation on the composition of a bacterial population that degrades a xenobiotic compound in a continuous culture.
Modeling the growth of Enterococcus faecium in bologna sausage
Authors: Zanoni B , Garzaroli C , Anselmi S , Rondinini G
Published: January 2020

A study to set up mathematical models which allow the prediction of Enterococcus faecium growth in bologna sausage (mortadella) was carried out. Growth curves were obtained at different temperatures (5, 6, 12, 15, 25, 32, 35, 37, 42, 46, 50, 52, and 55 degrees C). The Gompertz and logistic models, modified by Zwietering, were found to fit with the representation of experimental curves. The variations of the parameters A (i.e., the asymptotic value reached by the relative population during the stationary growth phase), mu m (i.e., the maximum specific growth rate during the exponential growth phase), and lambda (i.e., the lag time) with temperature were then modeled. The variation of A with temperature can be described by an empirical polynomial model, whereas the variation of mu m and lambda can be described by the Ratkowsky model modified by Zwietering and the Adair model, respectively. Data processing of these models has shown that the minimum growth temperature for E. faecium is 0.1 degrees C, the maximum growth temperature is 53.4 degrees C, and the optimal growth temperature is 42 to 45 degrees C.
New high-toxicity mosquitocidal strains of Bacillus sphaericus lacking a 100-kilodalton-toxin gene
Authors: Liu J W , Hindley J , Porter A G , Priest F G
Published: January 2020

Five new high-toxicity mosquitocidal strains of Bacillus sphaericus were isolated in Singapore. They all belong to phage group 8 and have binary toxin (51.4- plus 41.9-kDa) genes located on the chromosome but lack a 100-kDa-toxin gene. These strains of B. sphaericus constitute a new subgroup, as only two weakly toxic strains in phage group 8 have previously been described and all the known high-toxicity strains have both binary toxin and 100-kDa-toxin genes.
Possible initial steps in the catabolism of 1,2-diphenylethanone (deoxybenzoin) by Pseudomonas fluorescens DB-5
Authors: Hinrichsen P , Vicuña R
Published: January 2020

A natural bacterial strain, identified as Pseudomonas fluorescens DB-5, was isolated in enrichment cultures containing 1,2-diphenylethanone as the only source of carbon and energy. On the basis of characteristic features observed in the mass spectra of degradation intermediates, it is proposed that metabolism of 1,2-diphenylethanone is initiated by two hydroxylations on the benzyl ring. Phenol, presumably arising from the benzoyl ring, was transiently detected as a catabolic intermediate.
Fine regulation of cI857-controlled gene expression in continuous culture of recombinant Escherichia coli by temperature
Authors: Villaverde A , Benito A , Viaplana E , Cubarsi R
Published: January 2020

The expression at different temperatures of the lacZ gene, which is controlled by the lambda pL and pR tandem promoters and the cI857 temperature-sensitive repressor, was studied in Escherichia coli continuous cultures. At temperatures between 30 and 42 degrees C, beta-galactosidase activity behaved according to an exponential equation. By inducing a culture at a temperature within this range, predefined, nearly constant submaximal levels of gene expression and recombinant product yield can be obtained.
Identification of the gene encoding the major cellobiohydrolase of the white rot fungus Phanerochaete chrysosporium
Authors: Vanden Wymelenberg A , Covert S , Cullen D
Published: January 2020

Previous studies have shown that the cellobiohydrolases of the white rot basidiomycete Phanerochaete chrysosporium are encoded by a family of structurally related genes. In this investigation, we identified and sequenced the most highly transcribed gene, cbh1-4. Evidence suggests that in this fungus the dominant isozyme, CBH1, is encoded by chb1-4.
Degradation and induction specificity in actinomycetes that degrade p-nitrophenol
Authors: Hanne L F , Kirk L L , Appel S M , Narayan A D , Bains K K
Published: January 2020

We have isolated two soil bacteria (identified as Arthrobacter aurescens TW17 and Nocardia sp. strain TW2) capable of degrading p-nitrophenol (PNP) and numerous other phenolic compounds. A. aurescens TW17 contains a large plasmid which correlated with the PNP degradation phenotype. Degradation of PNP by A. aurescens TW17 was induced by preexposure to PNP, 4-nitrocatechol, 3-methyl-4-nitrophenol, or m-nitrophenol, whereas PNP degradation by Nocardia sp. strain TW2 was induced by PNP, 4-nitrocatechol, phenol, p-cresol, or m-nitrophenol. A. aurescens TW17 initially degraded PNP to hydroquinone and nitrite. Nocardia sp. strain TW2 initially converted PNP to hydroquinone or 4-nitrocatechol, depending upon the inducing compound.
Comparison of methods for specific depletion of ATP in Salmonella typhimurium
Authors: Johnson M S , Taylor B L
Published: January 2020

Three methods of ATP depletion in Salmonella typhimurium were compared. ATP concentrations were lowest after arsenate treatment. Arsenate or alpha-methylglucoside-plus-azide treatment nonspecifically lowered all nucleotide triphosphate levels. Histidine starvation in a hisF mutant was relatively specific for ATP depletion and therefore has potential in distinguishing ATP-dependent processes from processes dependent on other nucleotides.
Cloning and characterization of a cDNA from Aspergillus parasiticus encoding an O-methyltransferase involved in aflatoxin biosynthesis
Authors: Yu J , Cary J W , Bhatnagar D , Cleveland T E , Keller N P , Chu F S
Published: January 2020

Aflatoxins are polyketide-derived secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Among the catalytic steps in the aflatoxin biosynthetic pathway, the conversion of sterigmatocystin to O-methylsterigmatocystin and the conversion of dihydrosterigmatocystin to dihydro-O-methylsterigmatocystin are catalyzed by an S-adenosylmethionine-dependent O-methyltransferase. A cDNA library was constructed by using RNA isolated from a 24-h-old culture of wild-type A. parasiticus SRRC 143 and was screened by using polyclonal antiserum raised against a purified 40-kDa O-methyltransferase protein. A clone that harbored a full-length cDNA insert (1,460 bp) containing the 1,254-bp coding region of the gene omt-1 was identified by the antiserum and isolated. The complete cDNA sequence was determined, and the corresponding 418-amino-acid sequence of the native enzyme with a molecular weight of 46,000 was deduced. This 46-kDa native enzyme has a leader sequence of 41 amino acids, and the mature form of the enzyme apparently consists of 377 amino acids and has a molecular weight of 42,000. Direct sequencing of the purified mature enzyme from A. parasiticus SRRC 163 showed that 19 of 22 amino acid residues were identical to the amino acid residues in an internal region of the deduced amino acid sequence of the mature protein. The 1,460-bp omt-1 cDNA was cloned into an Escherichia coli expression system; a Western blot (immunoblot) analysis of crude extracts from this expression system revealed a 51-kDa fusion protein (fused with a 5-kDa beta-galactosidase N-terminal fragment).(ABSTRACT TRUNCATED AT 250 WORDS)
Phospholipid Fatty Acid Composition, Biomass, and Activity of Microbial Communities from Two Soil Types Experimentally Exposed to Different Heavy Metals
Authors: Frostegård Å. , Tunlid A. , Bååth E.
Published: January 2020

The phospholipid fatty acid (PLFA) pattern was analyzed in a forest humus and in an arable soil experimentally polluted with Cd, Cu, Ni, Pb, or Zn at different concentrations. In both soil types, there were gradual changes in the PLFA patterns for the different levels of metal contamination. The changes in the forest soil were similar irrespective of which metal was used, while in the arable soil the changes due to Cu contamination differed from those due to the other metals. Several PLFAs reacted similarly to the metal amendments in the two soil types, while others showed different responses. In both soils, the metal pollution resulted in a decrease in the iso-branched PLFAs i15:0 and i17:0 and in the monounsaturated 16:1ω5 and 16:1ω7
c
fatty acids, while increases were found for i16:0, the branched br17:0 and br18:0, and the cyclopropane cy17:0 fatty acids. In the forest soil, the methyl branched PLFAs 10Me16:0, 10Me17:0, and 10Me18:0 increased in metal-polluted soils, indicating an increase in actinomycetes, while in the arable soil a decrease was found for 10Me16:0 and 10Me18:0 in response to most metals. The bacterial PLFAs 15:0 and 17:0 increased in all metal-contaminated samples in the arable soil, while they were unaffected in the forest soil. Fatty acid 18:2ω6, which is considered to be predominantly of fungal origin, increased in the arable soil, except in the Cu-amended samples, in which it decreased instead. Effects on the PLFA patterns were found at levels of metal contamination similar to or lower than those at which effects on ATP content, soil respiration, or total amount of PLFAs had occurred.
Extra- and Intracellular Laccases of the Chestnut Blight Fungus,
Cryphonectria parasitica
Authors: Rigling Daniel , Van Alfen Neal K.
Published: January 2020

A double-stranded RNA virus of the chestnut blight pathogen,
Cryphonectria parasitica
, has been shown previously to reduce accumulation of mRNAs of extracellular laccase (laccase A) produced by this fungus. Both extra- and intracellular laccases have been detected after growth of the fungus in liquid culture. In addition to cellular localization, the two laccases are distinguishable by time of appearance during growth and electrophoretic mobility. Laccase A was purified from the culture filtrate by standard protein purification procedures. The enzyme was characterized as a glycoprotein with a molecular mass of approximately 77 kDa. Both laccase A and laccase B activities were significantly reduced in the hypovirulent (double-stranded RNA-infected) strain UEP1 compared with the isogenic virulent (double-stranded RNA-free) strain EP155/2.
Dose response of Cryptosporidium parvum in outbred neonatal CD-1 mice
Authors: Finch G R , Daniels C W , Black E K , Schaefer F W , Belosevic M
Published: January 2020

Cryptosporidium parvum infectivity in a neonatal CD-1 mouse model was used to determine the dose needed to infect 50% of the population. The 50% infective dose was estimated to be 79 oocysts. It was observed that a mean oral inoculum of 23 oocysts produced infection in 2 of 25 neonatal mice 7 days postinoculation. All animals became infected when the mean oral dose exceeded 310 oocysts per animal. The dose response of C. parvum was modeled with a logit dose-response model suitable for use in water disinfection studies.
Molecular cloning and expression of two alpha-amylase genes from Streptococcus bovis 148 in Escherichia coli
Authors: Satoh E , Niimura Y , Uchimura T , Kozaki M , Komagata K
Published: January 2020

The alpha-amylase genes of Streptococcus bovis 148 were cloned in Escherichia coli MC1061, using pBR322. The recombinant plasmids were classified into two groups on the basis of their restriction maps. Southern blot analysis did not show homology between the two types of alpha-amylase genes, and the two alpha-amylase genes existed on the chromosomal DNA of S. bovis 148. The enzymatic properties and N-terminal amino acid sequences of the two purified enzymes produced by the cloned E. coli strains were quite different from each other. Particularly, one alpha-amylase (Amy I) was adsorbed on raw corn starch and hydrolyzed raw corn starch, and another (Amy II) was not adsorbed on raw corn starch and did not hydrolyze raw corn starch. Amy I was considered to be the same as the extracellular alpha-amylase of S. bovis 148 in raw starch absorbability, ability to hydrolyze raw corn starch, enzymatic characteristics, N-terminal amino acid sequence, and mode of action on soluble starch. Amy II showed a unique pattern of oligosaccharide production from soluble starch compared with the extracellular alpha-amylase of S. bovis 148. Amy II was suggested to be an intracellular alpha-amylase of S. bovis 148.
In situ growth and activity and modes of penetration of Escherichia coli in unconsolidated porous materials
Authors: Sharma P K , McInerney M J , Knapp R M
Published: January 2020

Statistically reliable data on the in situ rates of growth, substrate consumption, and product formation are required to test the validity of the mathematical models developed for microbially enhanced oil recovery and in situ bioremediation processes. A simple, replicable porous-core system that could be aseptically divided into sections at various times was developed to follow the kinetics of microbial growth and metabolism in situ. This core system was used to study the kinetics of growth and the mode of penetration of strains of Escherichia coli through anaerobic, nutrient-saturated, fine Ottawa sand (permeability of 7.0 microns2 and porosity of 37%) under static conditions. The in situ rate of growth of a wild-type, motile, chemotactic strain, RW262, was two times slower inside cores than it was in liquid cultures. The mode of metabolism of galactose by strain RW262 was not altered inside cores, as acetate was the only product detected either inside the cores or in liquid cultures. Without applied advective force, strain RW262 grew exponentially and moved through cores at a rate of about 0.1 m/day. The cell population moved through cores in a band-like fashion, as the front of the moving cells consisted of high cell concentrations (greater than 10(5) cells per ml). Until the breakthrough of the cells occurred, galactose consumption and acetate production were observed only in the proximal sections of the core, showing that the cell propagation preceded the complete depletion of the substrate or the accumulation of large amounts of products.(ABSTRACT TRUNCATED AT 250 WORDS)
Aminopeptidase Activity in Marine Chroococcoid Cyanobacteria
Authors: Martinez Josefina , Azam Farooq
Published: January 2020

Synechococci are important primary producers in the ocean and can also utilize some components of the dissolved organic matter (DOM). The readily utilizable DOM in seawater is mainly polymeric (e.g., protein, polysaccharide) or phosphorylated and requires hydrolysis prior to uptake. We examined whether synechococci express ectoenzymes to hydrolyze DOM components and considered the possible significance of ectohydrolases for
Synechococcus
ecology and organic matter cycling in the sea. Five strains of non-nitrogen-fixing synechococci in axenic cultures were tested for enzyme activities with fluorogenic substrates. All strains show ectocellular aminopeptidase activity, but other enzymes were undetectable. The aminopeptidase level was in the range determined for five marine heterotrophic bacterial isolates tested for comparison. Aminopeptidase was not secreted into the medium; the majority (74%; tested in WH 7803) was cell surface bound, and a small fraction was periplasmic. The periplasmic activity was not released by cold osmotic shock of WH 7803. Phenylmethylsulfonyl fluoride and EDTA, inhibitors of serine and metalloproteases, strongly or completely inhibited WH 7803 aminopeptidase. The enzyme seemed constitutive; per-cell activity did not change during incubations in unenriched seawater, bovine serum albumin, or nitrate-replete mineral medium. In natural planktonic assemblages in the Southern California Bight, aminopeptidase activity was correlated with
Synechococcus
abundance as well as the abundance of other bacteria. Ectocellular aminopeptidase may be common in marine synechococci and play roles in their nitrogen nutrition, particularly in low-nitrate and low-light environments. Since synechococci are much less abundant than heterotrophic bacteria in seawater, the impact of
Synechococcus
aminopeptidase on proteolysis in the sea is likely to be episodic and restricted to specialized microenvironments.
Temporally Regulated Transcriptional Expression of the Genomes of Lactococcal Bacteriophages c2 and sk1
Authors: Beresford Tom P. J. , Ward Lawrence J. H. , Jarvis Audrey W.
Published: January 2020

Transcription maps of the
Lactococcus lactis
subsp.
lactis
prolate phage c2 and small isometric phage sk1 were constructed. Early and late transcripts were demonstrated in phage c2. Early transcription was localized to within a 7.5-kb
Eco
RV fragment, and late transcription included the region which encodes the phage structural proteins and a lysin gene. Early, middle, and late transcripts were demonstrated in phage sk1. Transcription was confined to an 11.3-kb region defined by the three
Eco
RV restriction fragments of 6.2, 4.7, and 0.46 kb during the early part of the sk1 life cycle. Middle gene transcripts extended from the
Eco
RV site (defining the left-hand limit of early gene expression) through the
cos
site and included the 4.3-kb
Pvu
II-
cos
fragment. Late transcription was detected over the remainder of the phage genome. These results indicated that gene expression was temporally regulated at the level of transcription in these two lactococcal phages and that two regions of time-dependent transcription exist in phage c2 and three in phage sk1.
Inhibition of Ammonia Oxidation in
Nitrosomonas europaea
by Sulfur Compounds: Thioethers Are Oxidized to Sulfoxides by Ammonia Monooxygenase
Authors: Juliette Lisa Y. , Hyman Michael R. , Arp Daniel J.
Published: January 2020

Organic sulfur compounds are well-known nitrification inhibitors. The inhibitory effects of dimethylsulfide, dimethyldisulfide, and ethanethiol on ammonia oxidation by
Nitrosomonas europaea
were examined. Both dimethylsulfide and dimethyldisulfide were weak inhibitors of ammonia oxidation and exhibited inhibitory characteristics typical of substrates for ammonia monooxygenase (AMO). Depletion of dimethylsulfide required O
2
and was prevented with either acetylene or allylthiourea, two inhibitors of AMO. The inhibition of ammonia oxidation by dimethylsulfide was examined in detail. Cell suspensions incubated in the presence of ammonia oxidized dimethylsulfide to dimethyl sulfoxide. Depletion of six other thioethers was also prevented by treating cell suspensions with either allylthiourea or acetylene. The oxidative products of three thioethers were identified as the corresponding sulfoxides. The amount of sulfoxide formed accounted for a majority of the amount of sulfide depleted. By using gas chromatography coupled with mass spectrometry, allylmethylsulfide was shown to be oxidized to allylmethylsulfoxide by
N. europaea
with the incorporation of a single atom of
18
O derived from
18
O
2
into the sulfide. This result supported our conclusion that a monooxygenase was involved in the oxidation of allylmethylsulfide. The thioethers are concluded to be a new class of substrates for AMO. This is the first report of the oxidation of the sulfur atom by AMO in whole cells of
N. europaea
. The ability of
N. europaea
to oxidize dimethylsulfide is not unique among the ammonia-oxidizing bacteria.
Nitrosococcus oceanus
, a marine nitrifier, was also demonstrated to oxidize dimethylsulfide to dimethyl sulfoxide.