bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbohydrate Storage in the Entomopathogenic Fungus
Beauveria bassiana
Authors: Bidochka Michael J. , Low Nicholas H. , Khachatourians George G.
Published: January 2020

The entomopathogenic fungus
Beauveria bassiana
was grown in 1% (wt/vol) gelatin-liquid media singly supplemented with a monosaccharide (glucose or fructose), a disaccharide (maltose or trehalose), a polyol (glycerol, mannitol, or sorbitol), or the amino sugar
N
-acetyl-
d
-glucosamine. The relative contributions of the carbohydrate, protein, and water contents in the fungal biomass were determined. Carbohydrates composed 18 to 42% of the mycelial dry weight, and this value was lowest in unsupplemented medium and highest in medium supplemented with glucose, glycerol, or trehalose. Biomass production was highest in liquid cultures supplemented with trehalose. When liquid cultures were grown in medium supplemented with 0 to 1% (wt/vol) glucose, trehalose, or
N
-acetyl-
d
-glucosamine, there was an increase in the biomass production and the contribution of carbohydrate to mycelial dry weight. Regardless of the glucose concentration in the culture, water content of the mycelia remained about 77.5% (wt/wt). Mycelial storage carbohydrates were determined by capillary gas chromatography. In gelatin-liquid medium supplemented with 1% (wt/vol) glucose,
B. bassiana
stored glycogen (12.0%, wt/dry wt) and the polyols mannitol (2.2%), erythritol (1.6%), glycerol (0.4%), and arabitol (0.1%). Without glucose,
B. bassiana
stored glycogen (5.4%), mannitol (0.8%), glycerol (0.6%), and erythritol (0.6%) but not arabitol. To our knowledge, this is the first report of carbohydrate storage in an entomopathogenic fungus, and the results are discussed in relation to other fungi and the potential implications to commercial formulation and insect-fungus interactions.
Nutritional Features of
Syntrophomonas wolfei
Authors: Beaty P. Shawn , McInerney Michael J.
Published: January 2020

Syntrophomonas wolfei
subsp.
wolfei
grew poorly in a defined medium with crotonate as the energy source in the absence of rumen fluid. Thiamine, lipoic acid, biotin, cyanocobalamin, and
para
-aminobenzoic acid were required for growth comparable to that obtained with the rumen fluid-based medium. Iron and cobalt were also required for the growth of
S. wolfei
in the chemically defined medium.
Evidence that Cellulolysis by an Anaerobic Ruminal Fungus Is Catabolite Regulated by Glucose, Cellobiose, and Soluble Starch
Authors: Morrison Mark , Mackie Roderick I. , Kistner Albrecht
Published: January 2020

A
Piromyces
-like ruminal fungus was used to study preferential carbohydrate utilization of [U-
14
C]cellulose, both alone and in combination with several soluble sugars. For cells grown on cellulose alone, cellulolytic activity was immediate and, initially, greater than that observed in the presence of added carbohydrate. Cellulolytic activity remained minimal in cultures containing cellulose plus glucose or cellobiose until the soluble sugar was depleted. Soluble starch also regulated cellulose activity but to a lesser extent. The results presented suggest that some fungal cellulases are susceptible to catabolite regulatory mechanisms.
Effects of Partial O
2
Pressure, Partial CO
2
Pressure, and Agitation on Growth Kinetics of
Azospirillum lipoferum
under Fermentor Conditions
Authors: Paul Etienne , Mulard Daniel , Blanc Philippe , Fages Jacques , Goma Gerard , Pareilleux Alain
Published: January 2020

Azospirillum lipoferum
crt1 was grown in batch cultures under standard conditions at 85% saturation of dissolved oxygen (DO) and 30-g/liter glucose concentrations. Kinetic studies revealed nutritional limitations of growth and the presence of an initial lag phase prior to consumption of glucose. The influences of various gaseous environments and shear stress on growth, i.e., various conditions of agitation-aeration, were characterized. Faster growth in the first stages of the culture and shorter duration of the lag phase were observed at DO concentrations of <30% saturation. The possible influences of dissolved CO
2
concentration or shear stress or both were discounted, and we confirmed the detrimental effect of high DO levels (up to 80% saturation) and the favorable influence of low DO concentrations (lower than 30% saturation) on growth. It was concluded that the gaseous environment, i.e., the DO concentration, needs to be considered as an operating parameter and be accurately controlled to ensure optimal growth of
Azospirillum
cells.
Effects of Hg
2+
, CH
3
-Hg
+
, and Temperature on the Expression of Mercury Resistance Genes in Environmental Bacteria
Authors: Tsai Yu-Li , Olson Betty H.
Published: January 2020

Twenty different bacterial isolates obtained from a mercury-contaminated site in Oak Ridge, Tenn., were grown on plate count agar amended with 25 μg of Hg
2+
or 3 μg of CH
3
-Hg
+
(R-Hg
+
) per ml. The total cellular RNA was extracted from each isolate by an acid-guanidine-thiocyanate-phenol-chloroform method. The transcripts of
merA
and
merB
were detected and quantitated by Northern (RNA) hybridization. A qualitative assay of mercuric reductase was used to confirm the enzyme activity. Low temperature (4°C) with the presence of Hg
2+
(25 μg/ml) significantly increased the net
merA
transcripts of mid-log-phase cells of six environmental isolates. The net
merA
transcript production by 18 of the isolates increased when they were grown on 50% plate count broth with 15 μg of Hg
2+
per ml, but only 8 isolates showed increased production of
merB
transcripts. The MICs of Hg
2+
and R-Hg
+
for 10 methyl mercury-resistant isolates ranged from 45 to 110 μg of Hg
2+
and 0.6 to 4.5 μg of R-Hg
+
per ml. R-Hg
+
was able to induce the expression of
merB
in 70% of methyl mercury-resistant strains.
Isolation and Characterization of
Pichia heedii
Mutants Defective in Xylose Uptake
Authors: Does Amy L. , Bisson Linda F.
Published: January 2020

To investigate the role of xylose uptake in xylose metabolism in yeasts, we isolated a series of mutated strains of the yeast
Pichia heedii
which are defective in xylose utilization. Four of these demonstrated defects in xylose uptake. Overlaps between the functional or regulatory mechanisms for glucose and xylose uptake may exist in this yeast since some of the mutants defective in xylose uptake were also defective in glucose transport. None of the mutants were defective in xylose reductase or xylitol dehydrogenase activities.
Localization of inulinase and invertase in Kluyveromyces species
Authors: Rouwenhorst R J , Ritmeester W S , Scheffers W A , Van Dijken J P
Published: January 2020

In vivo hydrolysis of inulin and sucrose was examined in selected yeasts of the genus Kluyveromyces. Cells, grown in sucrose-limited chemostat cultures, were subjected to treatments for the removal of inulinase, the enzyme responsible for the hydrolysis of both inulin and sucrose. The effects of these treatments were studied by measurement of inulin-dependent and sucrose-dependent oxygen consumption by cell suspensions. In Kluyveromyces marxianus var. marxianus, inulinase was partially secreted into the culture fluid. Removal of culture fluid inulinase by washing had no effect on sucrose-dependent oxygen consumption by this yeast. However, this treatment drastically reduced inulin-dependent oxygen consumption. Treatment of washed cells with sulfhydryls removed part of the cell wall-retained inulinase and reduced inulin-dependent oxygen consumption by another 80%. Sucrose-dependent oxygen consumption was less affected, decreasing by 40%. Cell suspensions of K. marxianus var. drosophilarum, K. marxianus var. vanudenii, and Saccharomyces kluyveri rapidly utilized sucrose but not inulin. This is in accordance with the classification of these yeasts as inulin negative. Supernatants of cultures grown at pH 5.5 did not catalyze the hydrolysis of inulin and sucrose. This suggested that these yeasts contained a strictly cell-bound invertase, an enzyme not capable of inulin hydrolysis. However, upon washing, cells became able to utilize inulin. The inulin-dependent oxygen consumption further increased after treatment of the cells with sulfhydryls. These treatments did not affect the sucrose-dependent oxygen consumption of the cells. Apparently, these treatments removed a permeability barrier for inulin that does not exist for sucrose.(ABSTRACT TRUNCATED AT 250 WORDS)
Structure and properties of the extracellular inulinase of Kluyveromyces marxianus CBS 6556
Authors: Rouwenhorst R J , Hensing M , Verbakel J , Scheffers W A , van Duken J P
Published: January 2020

In the yeast Kluyveromyces marxianus two forms of inulinase were present, namely, an inulinase secreted into the culture fluid and an inulinase retained in the cell wall. Both forms were purified and analyzed by denaturing and nondenaturing polyacrylamide gel electrophoresis. With the use of endo-beta-N-acetyl-glucosaminidase H, it was established that the enzyme retained in the cell wall and the enzyme secreted into the culture fluid have similar subunits consisting of a 64-kDa polypeptide with varying amounts of carbohydrate (26 to 37% of the molecular mass). The two forms of inulinase differed in size because of their differences in subunit aggregation. The enzyme present in the culture fluid was a dimer, and the enzyme retained in the cell wall was a tetramer. The differences in oligomerization did not affect the apparent Km values towards the substrates sucrose and raffinose. These findings support the hypothesis that the retention of glycoproteins in the yeast cell wall may be caused by a permeability barrier towards larger glycoproteins. The amino-terminal end of inulinase was determined and compared with the amino terminus of the closely related invertase. The kinetic and structural evidence indicates that in yeasts two distinct beta-fructosidases exist, namely, invertase and inulinase.
Luminescence-based nonextractive technique for in situ detection of Escherichia coli in soil
Authors: Rattray E A , Prosser J I , Killham K , Glover L A
Published: January 2020

Measurement of light output by luminometry was used to estimate quantitatively the cell concentrations of luminescent strains of Escherichia coli in liquid culture and inoculated into soil. Strains were constructed in which luciferase production was autoinducible or constitutive. In the former, light output per cell varied considerably during growth but was constant in constitutive strains. In liquid culture, the lower detection limit was in the order of 10(2) cells ml-1. Sensitivity was reduced by approximately 1 order of magnitude for cells inoculated into soil, when 2 x 10(2) to 6 x 10(3) cells g of soil-1 could be detected. Light output measurements were obtained within 5 min of sampling, and luminometry therefore potentially offers a rapid and sensitive detection technique for genetically engineered microorganisms.
Fast-Growing, Aerobic, Heterotrophic Bacteria from the Rhizosphere of Young Sugar Beet Plants
Authors: Lambert Bart , Meire Patrick , Joos Henk , Lens Pierre , Swings Jean
Published: January 2020

Fast-growing, aerobic, heterotrophic bacteria from the root surface of young sugar beet plants were inventoried. Isolation of the most abundant bacteria from the root surface of each of 1,100 plants between the second and tenth leaf stage yielded 5,600 isolates. These plants originated from different fields in Belgium and Spain. All isolates were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total cellular proteins. Comparison of protein fingerprints allowed us to inventory the bacteria of individual plants of different fields or leaf stages and to analyze the composition and variability of the rhizobacterial population of young sugar beet plants. Each field harbored a specific population of bacteria which showed a highly hierarchic structure. A small number of bacteria occurring frequently at high densities dominated in each field. The major bacteria were identified as
Pseudomonas fluorescens, Xanthomonas maltophilia, Pseudomonas paucimobilis
, and
Phyllobacterium
sp. The former three species showed a high genetic variability as they were represented by different protein fingerprint types on the same or different fields or leaf stages. Twinspan analysis and relative abundance plots showed that the structure and composition of the bacterial populations varied strongly over time. Pseudomonads were typically early colonizers which were later replaced by
X. maltophilia
or
Phyllobacterium
sp.
Evidence for a Plasmid-Linked Restriction-Modification System in
Lactobacillus helveticus
Authors: de los Reyes-Gavilán Clara G. , Limsowtin Gaëtan K. Y. , Séchaud Laurent , Veaux Monique , Accolas Jean-Pierre
Published: January 2020

The presence of a restriction-modification (R/M) system against two bacteriophages, 328-B1 and hv, was demonstrated in three
Lactobacillus helveticus
strains, CNRZ 1094, CNRZ 1095, and CNRZ 1096. In addition, the burst size of phage 328-B1 in the three restrictive strains CNRZ 1094, CNRZ 1095, and CNRZ 1096 was reduced with respect to the values obtained in its propagating strain, CNRZ 328. Heating at 60°C did not inactivate the R/M system. Nonrestrictive variants from CNRZ 1094 were easily obtained under several culture conditions, but treatment with novobiocin at 42°C followed by storage at −20°C resulted in drastic elimination of the R
+
/M
+
phenotype from all clones tested. Electrophoretic analysis of CNRZ 1094 nonrestrictive variants revealed the concomitant loss of a 34-kb plasmid. Four
Eco
RI fragments from the 34-kb plasmid were cloned in the
Escherichia coli
vector pACYC184. The use of one or several of these fragments as probes confirmed the plasmidic location of the genes responsible for the R/M system. These probes also showed the presence of R/M plasmids in the two other restrictive strains, CNRZ 1095 and CNRZ 1096. Lactose-fermenting ability and/or proteolytic capacity was not linked to the 34-kb plasmid.
Natural plasmid transformation in a high-frequency-of-transformation marine Vibrio strain
Authors: Frischer M E , Thurmond J M , Paul J H
Published: January 2020

The estuarine bacterium Vibrio strain DI-9 has been shown to be naturally transformable with both broad host range plasmid multimers and homologous chromosomal DNA at average frequencies of 3.5 X 10(-9) and 3.4 X 10(-7) transformants per recipient, respectively. Growth of plasmid transformants in nonselective medium resulted in cured strains that transformed 6 to 42, 857 times more frequently than the parental strain, depending on the type of transforming DNA. These high-frequency-of-transformation (HfT) strains were transformed at frequencies ranging from 1.1 X 10(-8) to 1.3 X 10(-4) transformants per recipient with plasmid DNA and at an average frequency of 8.3 X 10(-5) transformants per recipient with homologous chromosomal DNA. The highest transformation frequencies were observed by using multimers of an R1162 derivative carrying the transposon Tn5 (pQSR50). Probing of total DNA preparations from one of the cured strains demonstrated that no plasmid DNA remained in the cured strains which may have provided homology to the transforming DNA. All transformants and cured strains could be differentiated from the parental strains by colony morphology. DNA binding studies indicated that late-log-phase HfT strains bound [3H]bacteriophage lambda DNA 2.1 times more rapidly than the parental strain. These results suggest that the original plasmid transformation event of strain DI-9 was the result of uptake and expression of plasmid DNA by a competent mutant (HfT strain). Additionally, it was found that a strain of Vibrio parahaemolyticus, USFS 3420, could be naturally transformed with plasmid DNA. Natural plasmid transformation by high-transforming mutants may be a means of plasmid acquisition by natural aquatic bacterial populations.
Purification and characterization of thermostable beta-mannanase and alpha-galactosidase from Bacillus stearothermophilus
Authors: Talbot G , Sygusch J
Published: January 2020

Bacillus stearothermophilus secretes beta-mannanase and alpha-galactosidase enzymatic activities capable of hydrolyzing galactomannan substrates. Expression of the hemicellulase activities in the presence of locust bean gum was sequential, with mannanase activity preceding expression of alpha-galactosidase activity. The hemicellulase activities were purified to homogeneity by a combination of ammonium sulfate fractionation, gel filtration, hydrophobic interaction chromatography, and ion-exchange and chromatofocusing techniques. The purified beta-D-mannanase is a dimeric enzyme (162 kilodaltons) composed of subunits having identical molecular weight (73,000). Maximal activity did not vary between pH 5.5 and 7.5. The beta-D-mannanase activity exhibited thermostability, retaining nearly full activity after incubation for 24 h at 70 degrees C and pH 6.5. The enzyme displayed high specificity for galactomannan substrates, with no-secondary xylanase or cellulase activity detected. Hydrolysis of locust bean gum yielded short oligosaccharides compatible with an endo mode of substrate depolymerization. Initial rate velocities of the mannanase activity displayed substrate inhibition and yielded estimates for Vmax and Km of 455 +/- 60 U/mg and 1.5 +/- 0.3 mg/ml, respectively, at 70 degrees C and pH 6.5. The alpha-galactosidase activity corresponded to a trimeric enzyme (247 kilodaltons) having subunits of identical molecular weight (82,000). The alpha-galactosidase had maximal activity at pH 7 to 7.5 and retained full activity after 24 h of incubation at 60 degrees C. The enzyme had only limited activity on galactomannan substrates as compared with hydrolysis of p-nitrophenyl alpha-D-galactose. Kinetics of p-nitrophenyl alpha-D-galactose hydrolysis yielded linear reciprocal plots corresponding to Vmax and Km of 195 +/- 10 U/mg and 0.25 +/- 0.02 mM, respectively, at 60 degrees C and pH 7. The characterization of the mannanase activity is consistent with its potential use in enzymatic bleaching of softwood pulps.
Basis for Diel Variation in Nitrogenase Activity in the Marine Planktonic Cyanobacterium
Trichodesmium thiebautii
Authors: Capone Douglas G. , O'Neil Judith M. , Zehr Jonathan , Carpenter Edward J.
Published: January 2020

Natural populations of the nonheterocystous marine cyanobacterium
Trichodesmium thiebautii
exhibit a diel periodicity in nitrogenase activity (NA). NA “turns on” near dawn and “turns off” near dusk, independent of photic conditions. Chloramphenicol (CAP) and ammonium prevented turn on of NA in
T. thiebautii
when added to samples collected before dawn but were progressively less effective in inhibiting NA in samples collected later in the morning. In samples collected after turn on, activities declined with time with both CAP and ammonium treatments, with ammonium having a stronger effect. In contrast, CAP added to samples collected in late afternoon prolonged NA, compared with controls, which turned off. Direct analysis of the presence of the Fe protein of nitrogenase in
T. thiebautii
by using a Western immunoblot procedure found a strong protein band present in samples collected after 0800 h through the late evening but little or no Fe protein in samples collected within the 2 to 4 h preceding dawn. We conclude that the diel cycle of NA in
T. thiebautii
results from de novo synthesis of nitrogenase each morning and from the inactivation and degradation of nitrogenase in the late afternoon and night.
Catalase and Superoxide Dismutase of Root-Colonizing Saprophytic Fluorescent Pseudomonads
Authors: Katsuwon Jirasak , Anderson Anne J.
Published: January 2020

Root-colonizing, saprophytic fluorescent pseudomonads of the
Pseudomonas putida-P. fluorescens
group express similar levels of catalase and superoxide dismutase activities during growth on a sucrose- and amino acid-rich medium. Increased specific activities of catalase but not superoxide dismutase were observed during growth of these bacteria on components washed from root surfaces. The specific activities of both enzymes were also regulated during contact of these bacteria with intact bean roots. Increased superoxide dismutase and decreased catalase activities were observed rapidly, by 10 min upon inoculation of cells onto intact bean roots. Catalase specific activity increased with time to peak at 12 h before declining. By 48 h, the cells displayed this low catalase but maintained high superoxide dismutase specific activities. Catalase with a low specific activity and a high superoxide dismutase activity also were present in extracts of cells obtained from 7-day-old roots colonized from inoculum applied to seed. This specific activity of superoxide dismutase of root-contacted cells was about fourfold-higher in comparison to cells grown on rich medium, whereas the specific activity for catalase was reduced about fivefold. A single catalase isozyme, isozyme A, and one isozyme of superoxide dismutase, isozyme 1, were detected during growth of the bacteria on root surface components and during exposure of cells to intact bean roots for 1 h. An additional catalase, isozyme B, was detected from bacteria after exposure to the intact bean roots for 12 h. Catalase isozyme A and superoxide dismutase isozyme 1 were located in the cytoplasm and catalase band B was located in the membrane of
P. putida.
Stereospecific Reduction of Ethyl 2′ -Ketopantothenate to Ethyl D-(+)-Pantothenate with Microbial Cells as a Catalyst
Authors: Kataoka Michihiko , Shimizu Sakayu , Doi Yukiko , Yamada Hideaki
Published: January 2020

A novel enzymatic process for the synthesis of D-(+)-pantothenic acid through the asymmetric reduction of the 2′ -ketopantothenate ester is described.
Candida macedoniensis
AKU 4588 was found to convert ethyl 2′ -ketopantothenate (80 mg/ml) almost specifically to ethyl D-(+)-pantothenate (>98% enantiomeric excess), with a molar yield of 97.2%.
Binding of Dissolved Strontium by
Micrococcus luteus
Authors: Faison Brendlyn D. , Cancel Carmen A. , Lewis Susan N. , Adler Howard I.
Published: January 2020

Resting cells of
Micrococcus luteus
have been shown to remove strontium (Sr) from dilute aqueous solutions of SrCl
2
at pH 7. Loadings of 25 mg of Sr per g of cell dry weight were achieved by cells exposed to a solution containing 50 ppm (mg/liter) of Sr. Sr binding occurred in the absence of nutrients and did not require metabolic activity. Initial binding was quite rapid (<0.5 h), although a slow, spontaneous release of Sr was observed over time. Sr binding was inhibited in the presence of polyvalent cations but not monovalent cations. Ca and Sr were bound preferentially over all other cations tested. Sr-binding activity was localized on the cell envelope and was sensitive to various chemical and physical pretreatments. Bound Sr was displaced by divalent ions or by H
+
. Other monovalent ions were less effective. Bound Sr was also removed by various chelating agents. It was concluded that Sr binding by
M. luteus
is a reversible equilibrium process. Both ion exchange mediated by acidic cell surface components and intracellular uptake may be involved in this activity.
Metal-Binding Characteristics of the Gamma-Glutamyl Capsular Polymer of
Bacillus licheniformis
ATCC 9945
Authors: McLean Robert J. C. , Beauchemin Diane , Clapham Lynann , Beveridge Terry J.
Published: January 2020

The metal-binding affinity of the anionic poly-γ-
d
-glutamyl capsule of
Bacillus licheniformis
was investigated by using Na
+
, Mg
2+
, Al
3+
, Ca
2+
, Cr
3+
, Mn
2+
, Fe
3+
, Ni
2+
, and Cu
2+
. Purified capsule was suspended in various concentrations of the chloride salts of the various metals, and after dialysis the bound metals were analyzed either by graphite furnace atomic absorption spectroscopy or by inductively coupled plasma-mass spectrometry. Exposure of purified capsule to excess concentrations of Na
+
revealed it to contain 8.2 μmol of anionic sites per mg on the basis of Na binding. This was confirmed by titration of the capsule with HCl and NaOH. Other metal ions were then added in ionic concentrations equivalent to 25, 50, 75, 100, 200, and 400% of the available anionic sites. The binding characteristics varied with the metal being investigated. Addition of Cu
2+
, Al
3+
, Cr
3+
, or Fe
3+
induced flocculation. These metal ions showed the greatest affinity for
B. licheniformis
capsule in competitive-binding experiments. Flocculation was not seen with the addition of other metal ions. With the exception of Ni
2+
and Fe
3+
all capsule-metal-binding sites readily saturated. Ni
2+
had low affinity for the polymer, and its binding was increased at high metal concentrations. Fe
3+
binding resulted in the development of rust-colored ferrihydrite which itself could bind additional metal. Metal-binding characteristics of
B. licheniformis
capsule appear to be influenced by the chemical and physical properties of both the capsule and the metal ions.
Mechanism by which ammonium bicarbonate and ammonium sulfate inhibit mycotoxigenic fungi
Authors: DePasquale D A , Montville T J
Published: January 2020

In this study we examined the mechanism by which ammonium bicarbonate inhibits mycotoxigenic fungi. Elevated extracellular pH, alone, was not responsible for the antifungal activity. Although conidia of Penicillium griseofulvum and Fusarium graminearum had internal pH (pHi) values as high as 8.0 in buffer at an external pH (pHo) of 9.5, their viability was not markedly affected. The pHi values from conidia equilibrated in glycine-NaOH-buffered treatments without ammonium bicarbonate or ammonium sulfate were similar to values obtained from buffered treatments containing the ammonium salts. Thus, inhibition did not appear to be directly related to increased pHi. Ammonium sulfate in buffered media at pH greater than or equal to 8.7 was as inhibitory as ammonium bicarbonate, but was completely ineffective at pH less than or equal to 7.8. The hypothesis that free ammonia caused the fungal inhibition was tested by using ammonium sulfate as a model for ammonium bicarbonate. Viability, expressed as log CFU/ml, and percent germination of P. griseofulvum and F. graminearum decreased dramatically as the free ammonia concentration increased. Germination rate ratios (the germination rate in buffered ammonium sulfate divided by the germination rate in buffer alone) decreased linearly as the free ammonia concentration increased, further establishing NH3 as the toxic agent. Ammonium bicarbonate inhibits fungi because the bicarbonate anion supplies the alkalinity necessary to establish an antifungal concentration of free ammonia.
Adhesion of Macroconidia to the Plant Surface and Virulence of
Nectria haematococca
Authors: Jones Margaret J. , Epstein Lynn
Published: January 2020

To study spore attachment of the cucurbit pathogen
Nectria haematococca
(anamorph,
Fusarium solani
f. sp.
cucurbitae
), mutants with adhesion-deficient macroconidia were isolated. The adhesion-deficient mutants were selected after treatment with
N
-methyl-
N′
-nitro-
N
-nitrosoguanidine followed by repeated enrichment for macroconidia which did not attach to polystyrene. Two independently derived mutants produced macroconidia with an approximately 50% reduction in attachment to polystyrene and to zucchini fruits. When macroconidia were inoculated into wounded zucchini fruits, the adhesion-deficient mutants were as virulent as the wild-type strain. However, in disease assays in which macroconidia were deposited onto the surface of unwounded zucchini, the mutants were less virulent than the wild type. Thus, adhesion of
N. haematococca
macroconidia to its host surface appears to be a virulence factor.
Assessment of the bacteriological activity associated with granular activated carbon treatment of drinking water
Authors: Stewart M H , Wolfe R L , Means E G
Published: January 2020

Bacteriological analyses were performed on the effluent from a conventional water treatment pilot plant in which granular activated carbon (GAC) had been used as the final process to assess the impact of GAC on the microbial quality of the water produced. Samples were collected twice weekly for 160 days from the effluents of six GAC columns, each of which used one of four different empty-bed contact times (7.5, 15, 30, and 60 min). The samples were analyzed for heterotrophic plate counts and total coliforms. Effluent samples were also exposed to chloramines and free chlorine for 60 min (pH 8.2, 23 degrees C). Bacterial identifications were performed on the disinfected and nondisinfected effluents. Additional studies were conducted to assess the bacteriological activity associated with released GAC particles. The results indicated that heterotrophic plate counts in the effluents from all columns increased to 10(5) CFU/ml within 5 days and subsequently stabilized at 10(4) CFU/ml. The heterotrophic plate counts did not differ at different empty-bed contact times. Coliforms (identified as Enterobacter spp.) were recovered from the nondisinfected effluent on only two occasions. The disinfection results indicated that 1.5 mg of chloramines per liter inactivated approximately 50% more bacteria than did 1.0 mg of free chlorine per liter after 1 h of contact time. Chloramines and chlorine selected for the development of different bacterial species--Pseudomonas spp. and Flavobacterium spp., respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Phenotypic Switching Affecting Chemotaxis, Xanthan Production, and Virulence in
Xanthomonas campestris
Authors: Kamoun Sophien , Kado Clarence I.
Published: January 2020

The chemotaxis towards sucrose and yeast extract of nine strains of
Xanthomonas campestris
representing pathovars campestris, armoraciae, translucens, vesicatoria, and pelargonii was analyzed by using swarm plates. Unexpectedly, each of these strains formed small or reduced swarms typical of nonmotile or nonchemotactic bacteria. With time, however, chemotactic cells appeared on the swarm plates as blebs of bacteria. These cells were strongly chemotactic and were concomitantly deficient in exopolysaccharide production. The switch from the wild type (exopolysaccharide producing and nonchemotactic) to the swarmer type (exopolysaccharide deficient and chemotactic) appeared irreversible ex planta in bacteriological medium. However, in radish leaves swarmer-type strains of
X. campestris
pv. campestris were able to revert to the wild type. Swarmer-type derivatives of two
X. campestris
pv. campestris wild-type isolates showed reduced virulence and growth in the host plants cauliflower and radish. However, exocellular complementation of
X. campestris
pv. campestris Hrp (nonpathogenic) mutant was achieved by coinoculation with a swarmer-type strain.
Thiobacillus cuprinus
sp. nov., a Novel Facultatively Organotrophic Metal-Mobilizing Bacterium
Authors: Huber Harald , Stetter Karl O.
Published: January 2020

Five strains of mesophilic, facultatively organotrophic, ore-leaching eubacteria were isolated from solfatara fields in Iceland and a uranium mine in the Federal Republic of Germany. The new organisms are aerobic gram-negative rods. They can use sulfidic ores or elemental sulfur as sole energy source, indicating that they belong to the genus
Thiobacillus.
Alternatively, they grow on organic substrates such as yeast extract, peptone, and pyruvate. In contrast to the other leaching bacteria known so far, the new isolates are unable to oxidize ferrous iron. They consist of extreme and moderate acidophiles growing optimally at pH 3 and 4, respectively. The extreme acidophiles showed leaching characteristics similar to those shown by
Thiobacillus ferrooxidans
, while the moderate acidophiles exhibited a pronounced preference for copper leaching on some chalcopyrite ores. The G+C content of the DNA is between 66 and 69 mol%, depending on the isolate. In DNA-DNA hybridization experiments, the new strains showed homologies among each other of >70%, indicating that they belong to the same species. No significant DNA homology to
Thiobacillus
reference strains was detectable. Therefore, the new isolates represent a new species of
Thiobacillus
, which we name
Thiobacillus cuprinus
. Isolate H�5 is designated as the type strain (DSM 5495).
Efficacy of a variety of disinfectants against Listeria spp
Authors: Best M , Kennedy M E , Coates F
Published: January 2020

The efficacy of 14 disinfectants against Listeria innocua and two strains of Listeria monocytogenes in the presence of organic matter was studied. Quantitative efficacy tests were used. Many of the disinfectants tested were not as effective on Listeria spp. when the test organisms were dried onto the surface of steel disks (carrier tests) as they were when the organisms were placed in suspension (suspension test). The presence of whole serum and milk (2% fat) further reduced the disinfectant capacities of most of the formulations studied. Only three disinfectants (povidone-iodine, chlorhexidine gluconate, and glutaraldehyde) were effective in the carrier test in the presence of serum; however, all three were ineffective when challenged with milk (2% fat). Only one solution, sodium dichloroisocyanurate, was effective in the presence of milk. All but four formulations (chloramine-T, phosphoric acid, an iodophor, and formaldehyde) were effective in the suspension tests, regardless of the organic load. L. monocytogenes was observed to be slightly more resistant to disinfection than L. innocua was. There was no difference in disinfectant susceptibility between the two strains of L. monocytogenes. These findings emphasize the need for caution in selecting an appropriate disinfectant for use on contaminated surfaces, particularly in the presence of organic material.
Effect of Environmental Conditions on Extracellular Protease Activity in Lignolytic Cultures of
Phanerochaete chrysosporium
Authors: Dosoretz Carlos G. , Chen Hsin-Chih , Grethlein Hans E.
Published: January 2020

Two different types of extracellular protease activity were identified in the culture fluid of
Phanerochaete chrysosporium
wild-type BKM-F grown in submerged batch culture on N-limited media. The first activity, which appears to be inherent to the active growth phase, displayed a maximum on day 2 and decreased to a very low level on day 4. The second activity, which appeared at day 8 following the peak of ligninase activity, seems to be characteristic of late secondary metabolism and is stimulated by carbon starvation. Cultures started with half the amount of glucose of other cultures showed a remarkably earlier development of secondary activity. In contrast, the fed-batch addition of glucose started when ligninase activity was at a maximum (day 6) completely repressed secondary protease activity and enhanced ligninase production. The addition of exogenous veratryl alcohol increased the level of secondary protease activity, whereas the oxygen supply pattern significantly affected both the time course and the level of overall proteolytic activity. The addition of phenylmethylsulfonyl fluoride to growing cultures (0, 1, or 6 days) diminished overall protease activity, while it significantly enhanced ligninase activity. In all cases, the time courses of protease and ligninase activities were negatively correlated, indicating that protease activity promotes the decline of ligninase activity in batch culture.
Monoclonal Antibodies to Ferric Pseudobactin, the Siderophore of Plant Growth-Promoting
Pseudomonas putida
B10
Authors: Buyer Jeffrey S. , Sikora Lawrence J. , Kratzke Marian G.
Published: January 2020

Monoclonal antibodies to ferric pseudobactin, the siderophore (microbial iron transport agent) of plant growth-promoting
Pseudomonas putida
B10, have been developed. Three immunoglobulin G subclass 1-type monoclonal antibodies have been characterized. Each antibody appears to be unique on the basis of their reactions with ferric pseudobactin and with culture supernatants from other pseudomonads. None of the three cross-reacts with ferric pseudobactin-type siderophores produced by seven other pseudomonads. However,
P. aeruginosa
ATCC 15692 and
P. fluorescens
ATCC 17400 produced relatively high-molecular-mass compounds (mass greater than approximately 30,000 daltons) that did react with the antibodies. The compound from
P. aeruginosa
was not iron regulated, while the compound from
P. fluorescens
was produced only under iron-limiting conditions. A competitive assay using these antibodies has a detection limit of 5 � 10
−12
mol of ferric pseudobactin. This is, to our knowledge, the first report of monoclonal antibodies reactive with siderophores.
Copper Resistance Gene Homologs in Pathogenic and Saprophytic Bacterial Species from Tomato
Authors: Cooksey Donald A. , Azad Hamid R. , Cha Jae-Soon , Lim Chun-Keun
Published: January 2020

Copper-resistant strains of
Xanthomonas campestris
pv.
vesicatoria, Pseudomonas cichorii, Pseudomonas putida, Pseudomonas fluorescens
, and a yellow
Pseudomonas
sp. were isolated from tomato plants or seeds. In Southern hybridizations, DNA from each strain showed homology with the copper resistance (
cop
) operon previously cloned from
Pseudomonas syringae
pv.
tomato
PT23. Homology was associated with plasmid and chromosomal DNA in
X. compestris
pv.
vesicatoria, P. putida
, and the yellow
Pseudomonas
sp. Homology was detected only in the chromosomal DNA of
P. cichorii
and
P. fluorescens.
Homology with
cop
was also detected in chromosomal DNA from copper-sensitive strains of
P. cichorii, P. fluorescens
, and
P. syringae
pv.
tomato
, suggesting that the
cop
homolog may be indigenous to certain
Pseudomonas
species and have some function other than copper resistance. No homology was detected in DNA from a copper-sensitive
X. campestris
pv. vesicatoria strain. Copper-inducible protein products were detected in each copper-resistant bacterium by immunoblot analysis with antibodies raised to the CopB protein from the
cop
operon. The role of the homologous DNA in copper resistance was confirmed for the
X. campestris
pv.
vesicatoria
strain by cloning and transferring the
cop
homolog to a copper-sensitive strain of
X. campestris
pv.
vesicatoria
. The possibility and implications of copper resistance gene exchange between different species and genera of pathogenic and saprophytic bacteria on tomato plants are discussed.
Ammonia-oxidizing bacteria in a chloraminated distribution system: seasonal occurrence, distribution and disinfection resistance
Authors: Wolfe R L , Lieu N I , Izaguirre G , Means E G
Published: January 2020

Nitrification in chloraminated drinking water can have a number of adverse effects on water quality, including a loss of total chlorine and ammonia-N and an increase in the concentration of heterotrophic plate count bacteria and nitrite. To understand how nitrification develops, a study was conducted to examine the factors that influence the occurrence of ammonia-oxidizing bacteria (AOB) in a chloraminated distribution system. Samples were collected over an 18-month period from a raw-water source, a conventional treatment plant effluent, and two covered, finished-water reservoirs that previously experienced nitrification episodes. Sediment and biofilm samples were collected from the interior wall surfaces of two finished-water pipelines and one of the covered reservoirs. The AOB were enumerated by a most-probable-number technique, and isolates were isolated and identified. The resistance of naturally occurring AOB to chloramines and free chlorine was also examined. The results of the monitoring program indicated that the levels of AOB, identified as members of the genus Nitrosomonas, were seasonally dependent in both source and finished waters, with the highest levels observed in the warm summer months. The concentrations of AOB in the two reservoirs, both of which have floating covers made of synthetic rubber (Hypalon; E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.), had most probable numbers that ranged from less than 0.2 to greater than 300/ml and correlated significantly with temperature and levels of heterotrophic plate count bacteria. No AOB were detected in the chloraminated reservoirs when the water temperature was below 16 to 18 degrees C. The study indicated that nitrifiers occur throughout the chloraminated distribution system. Higher concentrations of AOB were found in the reservoir and pipe sediment materials than in the pipe biofilm samples. The AOB were approximately 13 times more resistant to monochloramine than to free chlorine. After 33 min of exposure to 1.0 mg of monochloramine per liter (pH 8.2, 23 degrees C), 99% of an AOB culture was inactivated. The amounts of this disinfectant that are currently used (1.5 mg/liter at a 3:1 ratio of chlorine to ammonia-N) may be inadequate to control the growth of these organisms in the distribution system.
CO
2
Incorporation and 4-Hydroxy-2-Methylbenzoic Acid Formation during Anaerobic Metabolism of
m
-Cresol by a Methanogenic Consortium
Authors: Roberts Deborah J. , Fedorak Phillip M. , Hrudey Steve E.
Published: January 2020

The metabolism of
m
-cresol by methanogenic cultures enriched from domestic sewage sludge was investigated. In the initial studies, bromoethanesulfonic acid was used to inhibit methane production. This led to the accumulation of 4.0 � 0.8 mol of acetate per mol of
m
-cresol metabolized. These results suggested that CO
2
incorporation occurred because each molecule of
m
-cresol contained seven carbon atoms, whereas four molecules of acetate product contained a total of eight carbon atoms. To verify this, [
14
C]bicarbonate was added to bromoethanesulfonic acid-inhibited cultures, and those cultures yielded [
14
C]acetate. Of the label recovered as acetate, 89% was found in the carboxyl position. Similar cultures fed [
methyl
-
14
C]
m
-cresol yielded methyl-labeled acetate. A
14
C-labeled transient intermediate was detected in cultures given either
m
-cresol and [
14
C]bicarbonate or bicarbonate and [
methyl
-
14
C]
m
-cresol. The intermediate was identified as 4-hydroxy-2-methylbenzoic acid. In addition, another metabolite was detected and identified as 2-methylbenzoic acid. This compound appeared to be produced only sporadically, and it accumulated in the medium, suggesting that the dehydroxylation of 4-hydroxy-2-methylbenzoic acid led to an apparent dead-end product.
Osmoregulation in
Rhizobium meliloti
: Production of Glutamic Acid in Response to Osmotic Stress
Authors: Botsford James L. , Lewis Thomas A.
Published: January 2020

Rhizobium meliloti
, like many other bacteria, accumulates high levels of glutamic acid when osmotically stressed. The effect was found to be proportional to the osmolarity of the growth medium. NaCl, KCI, sucrose, and polyethylene glycol elicited this response. The intracellular levels of glutamate and K
+
began to increase immediately when cells were shifted to high-osmolarity medium. Antibiotics that inhibit protein synthesis did not affect this increase in glutamate production. Cells growing in conventional media at any stage in the growth cycle could be suspended in medium causing osmotic stress and excess glutamate accumulated. The excess glutamate did not appear to be excreted, and the intracellular level eventually returned to normal when osmotically stressed cells were suspended in low-osmolarity medium. A
glt
mutant lacking glutamate synthase and auxotrophic for glutamate accumulated excess glutamate in response to osmotic stress. Addition of isoleucine, glutamine, proline, or arginine stimulated glutamate accumulation to wild-type levels when the mutant cells were suspended in minimal medium with NaCl to cause osmotic stress. In both wild-type and mutant cells, inhibitors of transaminase activity, including azaserine and aminooxyacetate, reduced glutamate levels. The results suggest that the excess glutamate made in response to osmotic stress is derived from degradation of amino acids and transamination of 2-ketoglutarate.
Purification and Characterization of an Aminopeptidase from
Lactococcus lactis
subsp.
cremoris
Wg2
Authors: Tan P. S. T. , Konings W. N.
Published: January 2020

An aminopeptidase was purified to homogeneity from a crude cell extract of
Lactococcus lactis
subsp.
cremoris
Wg2 by a procedure that included diethyl-aminoethane-Sephacel chromatography, phenyl-Sepharose chromatography, gel filtration, and high-performance liquid chromatography over an anion-exchange column. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band with a molecular weight of 95,000. The aminopeptidase was capable of degrading several peptides by hydrolysis of the N-terminal amino acid. The peptidase had no endopeptidase or carboxypeptidase activity. The aminopeptidase activity was optimal at pH 7 and 40�C. The enzyme was completely inactivated by the
p
-chloromecuribenzoate mersalyl, chelating agents, and the divalent cations Cu
2+
and Cd
2+
. The activity that was lost by treatment with the sulfhydryl-blocking reagents was restored with dithiothreitol or β-mercapto-ethanol, while Zn
2+
or Co
2+
restored the activity of the 1,10-phenantroline-treated enzyme. Kinetic studies indicated that the enzyme has a relatively low affinity for lysyl-
p
-nitroanilide (

K
m

, 0.55 mM) but that it can hydrolyze this substrate at a high rate (
V
max
, 30 μmol/min per mg of protein).
Detection of the osmoregulator betaine in methanogens
Authors: Robertson D E , Noll D , Roberts M F , Menaia J A , Boone D R
Published: January 2020

Trimethyl glycine (glycine betaine) was detected by 13C nuclear magnetic resonance spectroscopy at high intracellular concentrations in several methanogens (Methanogenium cariaci, "Methanogenium anulus" AN9, Methanohalophilus zhilinae, Methanohalophilus mahii, and Methanococcus voltae) grown on marine media containing yeast extract. 13C labeling studies with Methanogenium cariaci suggested that the betaine which accumulated inside the cells was not synthesized de novo but was transported in from the medium. Proof of such a transport system was provided by growing Methanogenium cariaci on yeast-free medium supplemented with betaine. Under these conditions, betaine was the dominant osmoregulator.
Pathovar-Specific Antigens of
Xanthomonas campestris
pv.
begoniae
and
X. campestris
pv.
pelargonii
Detected with Monoclonal Antibodies
Authors: Benedict Albert A. , Alvarez Anne M. , Pollard Leonard W.
Published: January 2020

Two monoclonal antibodies specific for lipopolysaccharide antigens of
Xanthomonas campestris
pv.
begoniae
and pv.
pelargonii
reacted with all of their respective pathovar strains and not with 130 strains of other xanthomonads or 89 nonxanthomonads tested. These results, as well as previous results, indicate that pathovar-specific monoclonal antibodies were readily generated to strains of
X. campestris
pathovars that generally infect single hosts.
Purine Auxotrophic Mutants with Altered Spore Color in
Streptomyces azureus
. ATCC 14921
Authors: Yamada Sadako , Hayashida Shinsaku , Ogata Seiya
Published: January 2020

A purine auxotroph with pale purple spores and a derivative with yellowish orange spores were obtained from the wild-type strain of
Streptomyces azureus
ATCC 14921, which has bluish green spores. The changed color or pigmentation in the mutants was limited to the spores. They accumulated AIR (5′-phosphoribosyl-5-aminoimidazole) due to the lack of AIR carboxylase activity.
Gram staining apparatus for space station applications
Authors: Molina T C , Brown H D , Irbe R M , Pierson D L
Published: January 2020

A self-contained, portable Gram staining apparatus (GSA) has been developed for use in the microgravity environment on board the Space Station Freedom. Accuracy and reproducibility of this apparatus compared with the conventional Gram staining method were evaluated by using gram-negative and gram-positive controls and different species of bacteria grown in pure cultures. A subsequent study was designed to assess the performance of the GSA with actual specimens. A set of 60 human and environmental specimens was evaluated with the GSA and the conventional Gram staining procedure. Data obtained from these studies indicated that the GSA will provide the Gram staining capability needed for the microgravity environment of space.