bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and biological parameters that determine the fate of p-chlorophenol in laboratory test systems
Authors: Pritchard P H , O'Neill E J , Spain C M , Ahearn D G
Published: January 2020

Shake-flask and microcosm studies were conducted to determine the fate of para-chlorophenol (p-CP) in water and sediment systems and the role of sediment and nonsediment surfaces in the biodegradation process. Biodegradation of p-CP in estuarine water samples in shake flasks was slow over incubation periods of 300 h. The addition of detrital sediment resulted in immediate and rapid degradation evidenced by the production of 14CO2 from [14C]p-CP. The addition of sterile sediment, glass beads, or sand resulted in approximately four to six times more CO2 evolution than observed in the water alone. Densities of p-CP-degrading bacteria associated with the detrital sediment were 100 times greater than those enumerated in water. Bacteria in the water and associated with the sediment after preexposure of both water and sediment of p-CP demonstrated enhanced biodegradation. In some microcosms, p-CP was degraded completely in the top 1.0 cm of intact sediment beds. Sediment reworking activities by benthic invertebrates from one site were sufficient to mix p-CP deep into the sediment bed faster than biodegradation or molecular diffusion. p-CP was persistent at lower depths of the sediment, possibly a result of reduced oxygen conditions preventing aerobic biodegradation.
Growth kinetics of Pseudomonas alcaligenes C-0 relative to inoculation and 3-chlorobenzoate metabolism in soil
Authors: Focht D D , Shelton D
Published: January 2020

Pseudomonas alcaligenes C-0 was isolated from activated sewage sludge by enrichment with 3-chlorobenzoate (3CB) as the sole carbon source. The carbon balance from [14C]3CB in pure culture could be accounted for in substrate, biomass, and CO2 from all sampling periods and inoculum densities (0.012, 0.092, 0.20, and 0.92 micrograms of dry cells X ml-1), and inorganic chloride was produced stoichiometrically. Monod parameters as determined in culture were compared with the kinetics of 3CB metabolism in soil with decreasing inoculum densities (1.9 X 10(-1), 1.9 X 10(-3), and 1.9 X 10(-5) micrograms of cells X g-1). 3CB was refractile to attack in soil by indigenous microflora, but it was completely metabolized upon inoculation with P. alcaligenes C-0. The saturation constant KS was much higher in soil than in culture, but the yield coefficient Y and the growth rate constant were the same in both systems: mu max = 0.32 h-1; Y = 34 micrograms cells X mumol-1; KS = 0.18 mM in culture and 6.0 mM in soil solution (1.1 mumol X g-1 of soil). The parameter estimates obtained from the highest inoculum density could be used for the lower inoculum densities with reasonable agreement between predicted and observed 3CB concentrations in soil, although the residual sum of squares was progressively higher. Since the growth rate of P. alcaligenes C-0 in soil was comparable to its growth rate in culture, inoculation should be a viable strategy for biodegradation of 3CB in soil if indigenous microflora are unable to exploit this metabolic niche.
Carbon monoxide-dependent chemolithotrophic growth of Clostridium thermoautotrophicum
Authors: Savage M D , Wu Z G , Daniel S L , Lundie L L , Drake H L
Published: January 2020

The acetogen Clostridium thermoautotrophicum was cultivated under CO-dependent chemolithotrophic conditions. CO-dependent growth profiles and energetics indicated that supplemental CO2 was fundamental to efficient growth at the expense of CO. Overall product stoichiometry approximated 6.5CO----CH3CO2H + 3.5CO2 + 0.6 cell C + 0.5 unrecovered C. Initial CO/CO2 ratios of 2 to 4 yielded optimal doubling times and cell yields. Maximal YCO values approximated 2.5 g of cell dry weight per mol of CO consumed; YH2 was considerably lower than YCO. Cross-transfer growth experiments and protein profiles indicated differential expression of genes between CO and methanol cultures.
Hyphal Elongation of
Glomus fasciculatus
in Response to Root Exudates
Authors: Elias Karol S. , Safir Gene R.
Published: January 2020

The spore germination rates on water agar of the vesicular-arbuscular mycorrhizal fungus
Glomus fasciculatus
were highest at water potentials of −4 to −6 bars. Root exudates from plants grown in a sterile nutrient solution, with or without phosphorus, did not affect germination. Root exudates collected from 2-, 4-, and 6-week-old
Trifolium repens
cv. `Ladino' seedlings that were deprived of P enabled hyphal growth from germinated
Glomus fasciculatus
spores of 21.4, 14.7, and 7.6 mm, respectively. Hyphal elongation in the presence of exudates from plants grown with P, or in the absence of exudates, was negligible (<1 mm). Root P at 2 weeks was not significantly different between plants grown with and without P. There were no significant differences between the quantities of exudates from plants grown with or without P at 2, 4, and 6 weeks. The data suggest that it is the quality of exudates from plants experiencing P deprivation that is important in stimulating vesicular-arbuscular mycorrhizal hyphal elongation.
Relationship between Sodium Influx and Salt Tolerance of Nitrogen-Fixing Cyanobacteria
Authors: Apte Shree Kumar , Reddy Bontha Rajasekhar , Thomas Joseph
Published: January 2020

The relationship between sodium uptake and cyanobacterial salt (NaCl) tolerance has been examined in two filamentous, heterocystous, nitrogen-fixing species of
Anabaena.
During diazotrophic growth at neutral pH of the growth medium,
Anabaena
sp. strain L-31, a freshwater strain, showed threefold higher uptake of Na
+
than
Anabaena torulosa
, a brackish-water strain, and was considerably less salt tolerant (50% lethal dose of NaCl, 55 mM) than the latter (50% lethal dose of NaCl, 170 mM). Alkaline pH or excess K
+
(>25 mM) in the medium causes membrane depolarization and inhibits Na
+
influx in both cyanobacteria (S. K. Apte and J. Thomas, Eur. J. Biochem. 154:395-401, 1986). The presence of nitrate or ammonium in the medium caused inhibition of Na
+
influx accompanied by membrane depolarization. These experimental manipulations affecting Na
+
uptake demonstrated a good negative correlation between Na
+
influx and salt tolerance. All treatments which inhibited Na
+
influx (such as alkaline pH, K
+
above 25 mM, NO
3
−
, and NH
4
+
), enhanced salt tolerance of not only the brackish-water but also the freshwater cyanobacterium. The results indicate that curtailment of Na
+
influx, whether inherent or effected by certain environmental factors (e.g., combined nitrogen, alkaline pH), is a major mechanism of salt tolerance in cyanobacteria.
The action of sodium deoxycholate on Escherichia coli
Authors: D'Mello A , Yotis W W
Published: January 2020

Sodium deoxycholate is used in a number of bacteriological media for the isolation and classification of gram-negative bacteria from food and the environment. Initial experiments to study the effect of deoxycholate on the growth parameters of Escherichia coli showed an increase in the lag time constant and generation time and a decrease in the growth rate constant and total cell yield of this microorganism. Cell fractionation studies indicated that sodium deoxycholate at levels used in bacteriological media interferes with the incorporation of [U-14C]glucose into the cold-trichloroacetic acid-soluble, ethanol-soluble, and trypsin-soluble cellular fractions of E. coli. Finally, sodium deoxycholate interfered with the flagellation and motility of Proteus mirabilis and E. coli. It would appear then that further improvement of the deoxycholate medium may be in order.
Determining [
3
H]Thymidine Incorporation into Bacterioplankton DNA: Improvement of the Method by DNase Treatment
Authors: Servais P. , Martinez J. , Billen G. , Vives-Rego J.
Published: January 2020

Determination of [
3
H] thymidine incorporation into bacterial DNA versus other macromolecules is usually achieved by NaOH and hot trichloroacetic acid hydrolysis. This procedure was found not to be specific enough. An alternative method founded on DNase treatment is proposed. Under the new method, the fraction of thymidine incorporated into DNA ranged from 10 to 83%.
Expression of the Escherichia coli xylose isomerase gene in Saccharomyces cerevisiae
Authors: Sarthy A V , McConaughy B L , Lobo Z , Sundstrom J A , Furlong C E , Hall B D
Published: January 2020

Transformation of Saccharomyces cerevisiae by yeast expression plasmids bearing the Escherichia coli xylose isomerase gene leads to production of the protein. Western blotting (immunoblotting) experiments show that immunoreactive protein chains which comigrate with the E. coli enzyme are made in the transformant strains and that the amount produced parallels the copy number of the plasmid. When comparable amounts of immunologically cross-reactive xylose isomerase protein made in E. coli or S. cerevisiae were assayed for enzymatic activity, however, the yeast protein was at least 10(3)-fold less active.
Fermentation of
d
-Xylose to Ethanol by Genetically Modified
Klebsiella planticola
Authors: Tolan Jeffrey S. , Finn R. K.
Published: January 2020

d
-Xylose is a plentiful pentose sugar derived from agricultural or forest residues. Enteric bacteria such as
Klebsiella
spp. ferment
d
-xylose to form mixed acids and butanediol in addition to ethanol. Thus the ethanol yield is normally low.
Zymomonas
spp. and most yeasts are unable to ferment xylose, but they do ferment hexose sugars to ethanol in high yield because they contain pyruvate decarboxylase (EC 4.1.1.1), a key enzyme that is absent from enteric bacteria. This report describes the fermentation of
d
-xylose by
Klebsiella planticola
ATCC 33531 bearing multicopy plasmids containing the
pdc
gene inserted from
Zymomonas mobilis
. Expression of the gene markedly increased the yield of ethanol to 1.3 mol/mol of xylose, or 25.1 g/liter. Concurrently, there were significant decreases in the yields of formate, acetate, lactate, and butanediol. Transconjugant
Klebsiella
spp. grew almost as fast as the wild type and tolerated up to 4% ethanol. The plasmid was retained by the cells during at least one batch culture, even in the absence of selective pressure by antibiotics to maintain the plasmid. Ethanol production was 31.6 g/liter from 79.6 g of mixed substrate per liter chosen to simulate hydrolyzed hemicellulose. The physiology of the wild-type of
K. planticola
is described in more detail than in the original report of its isolation.
Survival and transport of bacteria in egg washwater
Authors: Pearson J , Southam G G , Holley R A
Published: January 2020

An evaluation of methods for monitoring the quality of water used to wash eggs at grading stations was undertaken to improve maintenance of bacterial viability during overnight sample transport. Bacterial content of samples at analysis would then better reflect conditions at the time eggs were washed. The interactive effects of temperature and the highly alkaline water conditions upon viability were the subjects of this study. Nine transport methods were examined for their efficacy in recovering total and coliform bacteria from recycled water used to wash eggs, and these were compared with samples analyzed at two commercial egg grading stations. Samples were shipped under test to the laboratory for analysis the following day. The survival of Staphylococcus aureus and Escherichia coli was also examined, but in a synthetic washwater matrix under various combinations of temperature (6 to 32 degrees C) and pH (9.5 to 10.5) to determine whether there was likely to be a different response to variations in transport treatment among gram-positive and -negative bacteria. S. aureus was much more resistant to the lethal effects of high pH and moderate temperature than E. coli. These results indicated that samples of high pH should be held (transported) at less than or equal to 13 degrees C to optimize bacterial survival. Considering cost, ease of manipulation, and the ability to protect both coliforms and the bacterial population as a whole, the method of choice for transport of industrial samples was the direct addition of washwater to containers in which powdered KH2PO4 and Na2S2O3 had been placed to yield final concentrations, when dissolved, of 0.2 and 0.05% (wt/vol), respectively.
Bactericidal activities of selected organic N-halamines
Authors: Williams D E , Worley S D , Barnela S B , Swango L J
Published: January 2020

The bactericidal efficacies of three organic N,N'-dihalamine disinfectants in the class of compounds termed imidazolidinones were determined for combinations of pH, temperature, and water quality treatments by using Staphylococcus aureus and Shigella boydii as test organisms. The compound 1,3-dibromo-4,4,5,5-tetramethyl-2-imidazolidinone was found to be the most rapidly acting bactericide, especially under halogen-demand-free conditions. The mixed N,N'-dihalamine 1-bromo-3-chloro-4,4,5,5-tetramethyl-2-imidazolidinone was found to be intermediate in terms of rate of disinfection, while the compound 1,3-dichloro-4,4,5,5-tetramethyl-2-imidazolidinone was observed to be the slowest acting bactericide. When overall effectiveness was judged on the basis of stability of the disinfectants along with rates of disinfection, the mixed halamine was considered to exhibit great potential for use as a disinfectant in an aqueous solution.
Mechanism of microwave sterilization in the dry state
Authors: Jeng D K , Kaczmarek K A , Woodworth A G , Balasky G
Published: January 2020

With an automated computerized temperature control and a specialized temperature measurement system, dry spores of Bacillus subtilis subsp. niger were treated with heat simultaneously in a convection dry-heat oven and a microwave oven. The temperature of the microwave oven was monitored such that the temperature profiles of the spore samples in both heat sources were nearly identical. Under these experimental conditions, we unequivocally demonstrated that the mechanism of sporicidal action of the microwaves was caused solely by thermal effects. Nonthermal effects were not significant in a dry microwave sterilization process. Both heating systems showed that a dwelling time of more than 45 min was required to sterilize 10(5) inoculated spores in dry glass vials at 137 degrees C. The D values of both heating systems were 88, 14, and 7 min at 117, 130, and 137 degrees C, respectively. The Z value was estimated to be 18 degrees C.
Production of Bacterial Inoculants by Direct Fermentation on Nutrient-Supplemented Vermiculite
Authors: Graham-Weiss Lori , Bennett Mari Lynn , Paau Alan S.
Published: January 2020

When supplemented with a nutrient source and moisture, sterile finely ground vermiculite can be used to directly ferment bacterial cultures to prepare bacterial inoculants. All tested bacterial species, including
Rhizobium japonicum, R. phaseoli, R. meliloti, R. leguminosarum, Bacillus megaterium
, and several
Pseudomonas
strains, grew at least 10,000-fold in 1 week at room temperature. The final product was stable and had no special storage or handling requirements. Due to the unique properties of vermiculite, direct fermentation of bacteria on nutrient-supplemented vermiculite offers a reliable process for manufacturing bacterial inoculants.
Toluene Induction and Uptake Kinetics and Their Inclusion in the Specific-Affinity Relationship for Describing Rates of Hydrocarbon Metabolism
Authors: Robertson B. R. , Button D. K.
Published: January 2020

The kinetics of concentration-dependent toluene metabolism were examined by evaluating each term in the second-order rate equation. Marine and freshwater pseudomonads were used. Uptake for
Pseudomonas
sp. strain T2 was characterized by a completely saturatable system with small transport constant (

K
t

= 44 μg/liter) and large specific affinity. Kinetics for
Pseudomonas putida
PpF1 were similar. Induction had little effect on

K
t

, but it caused the specific affinity to increase from about 0.03 to 320 liters/g of cells per h. The level of induction depended on the time of exposure, the concentration of inducer, and the initial level of induction. If loss of the inducible system was not severe, toluene caused a linear increase in specific affinity with time, and the maximal value achieved at intermediate times (1 to 3 days) was hyperbolic with concentration when
K
ind
was 96 μg/liter (A. T. Law and D. K. Button, Appl. Environ. Microbiol. 51:469-476, 1986). As repression became complete, specific affinities were greatly reduced. Then induction required higher toluene concentrations and longer times, and the shape of the specific-affinity curve became sigmoidal with concentration. Cell yields (0.10 to 0.17 g of cells per g of toluene used) were low owing to liberation of organic products: 2-hydroxy-6-oxohepta-2,4-dienoic acid, toluene dihydrodiol, 3-methylcatechol, acetate, formate, and possibly pyruvate, which in turn caused lower rates of growth. Michaelis constants for the reaccumulation of products exceeded those for toluene, but specific affinities were lower and maximal velocities were higher, so that recycling was favored in cultures with high toluene concentration. Although these kinetics predict deviation from the linear relationship between uptake rate and biomass, we could detect none. Effects of saturation and induction were incorporated into the basic specific-affinity relationship. The result appears to be an improvement in the equation used for describing the kinetics of uptake and growth.
Identification of a Vesicular-Arbuscular Mycorrhizal Fungus by Using Monoclonal Antibodies in an Enzyme-Linked Immunosorbent Assay
Authors: Wright Sara F. , Morton Joseph B. , Sworobuk Janis E.
Published: January 2020

Spore morphology is currently used to identify species of vesicular-arbuscular mycorrhizal fungi. We report the first use of a highly specific immunological method for identification of a vesicular-arbuscular mycorrhizal fungus. Two monoclonal antibodies were produced against
Glomus occultum.
Monoclonal antibodies reacted strongly with both spores and hyphae in an indirect enzyme-linked immunosorbent assay. All other mycorrhizal (29 species) and nonmycorrhizal (5 species) fungi tested were nonreactive with the monoclonal antibodies. A single spore of
G. occultum
was detectable in the presence of high numbers of spores of other vesicular-arbuscular mycorrhizal fungi. Variation in the reaction of
G. occultum
isolates from West Virginia, Florida, and Colombia suggests that monoclonal antibodies may differentiate strains.
Characterization of Macromolecular Flocculants Produced by
Phormidium
sp. Strain J-1 and by
Anabaenopsis circularis
PCC 6720
Authors: Bar-Or Y. , Shilo M.
Published: January 2020

Several benthic cyanobacteria were found to produce significant amounts of extracellular flocculants. The macromolecular flocculants produced by
Phormidium
sp. strain J-1 and
Anabaenopsis circularis
PCC 6720 were characterized. The
Phormidium
flocculant is a sulfated heteropolysaccharide to which fatty acids and protein are bound. The polysaccharide backbone is composed of uronic acids, rhamnose, mannose, and galactose. The
A. circularis
flocculant is also an acidic polysaccharide containing keto acid residues and neutral sugars, but to which no fatty acids, proteins, or sulfates are linked. Both flocculants could be recovered from growth medium by precipitation with cetyltrimethylammonium bromide and were found to bind the cationic dye Alcian-blue in a linear proportion to their concentration in solution. The latter property was used to quantify flocculant concentrations in culture supernatants and natural water samples and to compute their anion densities.
Abundance and distribution of Legionellaceae in Puerto Rican waters
Authors: Ortiz-Roque C M , Hazen T C
Published: January 2020

Waters in marine and freshwater areas of Puerto Rico were analyzed for the presence of Legionella spp. by direct fluorescent antibody assay with guinea pig confirmation. Several species, including L. bozemanii, L. dumoffii, L. gormanii, L. longbeachae, L. micdadei, and L. pneumophila, were widely distributed among all sites. Legionellaceae, including L. pneumophila, were found in high densities in water collected in the rain forest from epiphytes in trees 30 ft. (about 9.25 m) above the ground. Both interspecific and intersite variations were significant. L. pneumophila was the most abundant species at all sites, with average densities of 10(4) cells ml-1, very close to the range which is potentially pathogenic for humans. Densities of L. pneumophila were highest in sewage-contaminated coastal waters. These are the highest densities of Legionella spp. ever reported for marine habitats. Densities of L. pneumophila were positively correlated with concentrations of sulfates, phosphates, and pH. A survey of 88 fatal atypical pneumonia cases at a Puerto Rico hospital showed that 15% of the patients had L. pneumophila infections. This study establishes L. pneumophila as a relatively common cause of atypical pneumonia in Puerto Rico and suggests natural aquatic habitats as possible sources or reservoirs of pathogenic Legionella spp. in the tropics.
Influence of Molecular Size and Ligninase Pretreatment on Degradation of Lignins by
Xanthomonas
sp. Strain 99
Authors: Kern Hartmut W. , Kirk T. Kent
Published: January 2020

The purpose of this study was to examine the relationship between the molecular size of lignin in several preparations and extent of degradation (mineralization) by
Xanthomonas
sp. strain 99. The influence of ligninase pretreatment was also examined. Five synthetic lignins and one
14
C-methylated spruce lignin were used. The extent of mineralization to
14
CO
2
was greatest for the samples containing the most low-molecular-weight material, and the low-molecular-weight portions were preferentially (or perhaps solely) degraded. Pretreatment of the five synthetic lignins with crude ligninase increased their molecular size and decreased their degradability by the xanthomonad. Pretreatment of the methylated spruce lignin with crude ligninase caused both polymerization and depolymerization but resulted in a net decrease in bacterial degradability. Our results suggest that the xanthomonad can degrade lignins only up to a molecular weight of 600 to 1,000.
Mapping of a
Bradyrhizobium japonicum
DNA Region Carrying Genes for Symbiosis and an Asymmetric Accumulation of Reiterated Sequences
Authors: Hahn Matthias , Hennecke Hauke
Published: January 2020

Spontaneous kanamycin-sensitive derivatives were obtained from
Bradyrhizobium japonicum
(strain 110) carrying Tn
5
insertions in symbiotic gene cluster I; the derivatives were shown to have deletions of cluster I plus flanking DNA which was indicated by the absence of different copies of the repeated sequences RSα and RSβ. The deletion endpoints were mapped using cloned wild-type DNA fragments containing RSα copies which also served as origins for overlapped cosmid cloning. The majority of the deletions resulted from recombinational fusion of two remote RSα copies. Novel types of repeated sequences (RSγ, RSδ, and RSε) occurring in 12, 10, and 4 copies per genome were detected. Seven, nine, and three copies of RSγ, RSδ, and RSε, respectively, were located near cluster I. It is concluded that the
B. japonicum
genome has an unusual DNA segment of >230 kilobase pairs characterized by the presence of repeated sequences and genes for symbiotic N
2
fixation.
Detection of hemolytic Listeria monocytogenes by using DNA colony hybridization
Authors: Datta A R , Wentz B A , Hill W E
Published: January 2020

A fragment of about 500 base pairs of the beta-hemolysin gene from Listeria monocytogenes was used to screen different bacterial strains by DNA colony hybridization. The cells in the colonies were lysed by microwaves in the presence of sodium hydroxide. Of 52 different strains of Listeria species screened, only the DNA from beta-hemolytic (CAMP-positive) strains of L. monocytogenes hybridized with this probe.
Control of Interspecies Electron Flow during Anaerobic Digestion: Significance of Formate Transfer versus Hydrogen Transfer during Syntrophic Methanogenesis in Flocs
Authors: Thiele Jurgen H. , Zeikus J. Gregory
Published: January 2020

Microbial formate production and consumption during syntrophic conversion of ethanol or lactate to methane was examined in purified flocs and digestor contents obtained from a whey-processing digestor. Formate production by digestor contents or purified digestor flocs was dependent on CO
2
and either ethanol or lactate but not H
2
gas as an electron donor. During syntrophic methanogenesis, flocs were the primary site for formate production via ethanol-dependent CO
2
reduction, with a formate production rate and methanogenic turnover constant of 660 μM/h and 0.044/min, respectively. Floc preparations accumulated fourfold-higher levels of formate (40 μM) than digestor contents, and the free flora was the primary site for formate cleavage to CO
2
and H
2
(90 μM formate per h). Inhibition of methanogenesis by CHCl
3
resulted in formate accumulation and suppression of syntrophic ethanol oxidation. H
2
gas was an insignificant intermediary metabolite of syntrophic ethanol conversion by flocs, and its exogenous addition neither stimulated methanogenesis nor inhibited the initial rate of ethanol oxidation. These results demonstrated that >90% of the syntrophic ethanol conversion to methane by mixed cultures containing primarily
Desulfovibrio vulgaris
and
Methanobacterium formicicum
was mediated via interspecies formate transfer and that <10% was mediated via interspecies H
2
transfer. The results are discussed in relation to biochemical thermodynamics. A model is presented which describes the dynamics of a bicarbonate-formate electron shuttle mechanism for control of carbon and electron flow during syntrophic methanogenesis and provides a novel mechanism for energy conservation by syntrophic acetogens.
Influence of inorganic and organic nutrients on aerobic biodegradation and on the adaptation response of subsurface microbial communities
Authors: Swindoll C M , Aelion C M , Pfaender F K
Published: January 2020

The influence of inorganic and organic amendments on the mineralization of ethylene dibromide, p-nitrophenol, phenol, and toluene was examined in subsurface soil samples from a pristine aquifer near Lula, Okla. The responses indicate that the metabolic abilities and nutrient requirements of groundwater microorganisms vary substantially within an aquifer. In some samples, additions of inorganic nutrients resulted in a more rapid adaptation to the test substrate and a higher rate of metabolism, indicating that metabolism may have been limited by these nutrients. In other samples from the same aquifer layer, inorganic amendments had little or no influence on mineralization. In general, the addition of multiple inorganic nutrients resulted in a greater enhancement of degradation than did the addition of single substances. Additions of alternate carbon sources, such as glucose or amino acids, inhibited the mineralization of the xenobiotic substrates. This inhibition appears to be the result of the preferential utilization of the more easily degradable carbon amendments.
Deletion analysis of the proteinase gene of Streptococcus cremoris Wg2
Authors: Kok J , Hill D , Haandrikman A J , de Reuver M J , Laan H , Venema G
Published: January 2020

The Streptococcus cremoris Wg2 proteinase gene, cloned in S. lactis, specified a proteinase which exhibited the same specificity toward casein as did the proteinase isolated from the original host. Although the cloned gene lacked the last 130 codons, the proteinase still specifically degraded beta-casein. Deletion of the C-terminal 343 amino acids from the proteinase did not influence this specificity. Cell-free transcription-translation studies of plasmids carrying deletion derivatives of the proteinase gene showed that the 100-kilodalton C-terminally truncated proteinase still exhibited proteolytic activity. Crossed immunoelectrophoresis revealed that proteins A and B identified in the proteolytic system of S. cremoris Wg2 are both encoded by the proteinase gene. A working model based on integration of available genetic, immunological, and biochemical data is presented to explain this result.
Simple fluorescence method for rapid estimation of aflatoxin levels in a solid culture medium
Authors: Cotty P J
Published: January 2020

Aflatoxin concentrations in agar media were estimated with a direct technique that quantifies the fluorescence of agar containing aflatoxins. Tubes containing 5 ml of an agar medium inoculated with spores of aflatoxin-producing Aspergillus isolates were incubated for 3 days at 30 degrees C and set in a carriage specifically designed to carry culture tubes in a scanning densitometer. Fluorescence (450 nm and above) was elicited in the agar by UV light (365 nm) and photometrically measured. Agar fluorescence directly correlated (r2 = 0.89 +/- 0.05, P less than 0.001) with the concentration of aflatoxin within the range 0 to 18.7 micrograms/g. The lowest aflatoxin concentration detected was 50 ng/g. The technique successfully differentiated the aflatoxigenic potentials of Aspergillus isolates.
Induction of Xylose Reductase and Xylitol Dehydrogenase Activities in
Pachysolen tannophilus
and
Pichia stipitis
on Mixed Sugars
Authors: Bicho Paul A. , Runnals P. Lynn , Cunningham J. Douglas , Lee Hung
Published: January 2020

The induction of xylose reductase and xylitol dehydrogenase activities on mixed sugars was investigated in the yeasts
Pachysolen tannophilus
and
Pichia stipitis
. Enzyme activities induced on
d
-xylose served as the controls. In both yeasts,
d
-glucose,
d
-mannose, and 2-deoxyglucose inhibited enzyme induction by
d
-xylose to various degrees. Cellobiose,
l
-arabinose, and
d
-galactose were not inhibitory. In liquid batch culture,
P. tannophilus
utilized
d
-glucose and
d
-mannose rapidly and preferentially over
d
-xylose, while
d
-galactose consumption was poor and lagged behind that of the pentose sugar. In
P. stipitis
, all three hexoses were used preferentially over
d
-xylose. The results showed that the repressibility of xylose reductase and xylitol dehydrogenase may limit the potential of yeast fermentation of pentose sugars in hydrolysates of lignocellulosic substrates.
Nodulation, Nitrogen Fixation, and Hydrogen Oxidation by Pigeon Pea
Bradyrhizobium
spp. in Symbiotic Association with Pigeon Pea, Cowpea, and Soybean
Authors: Nautiyal C. S. , Hegde S. V. , van Berkum P.
Published: January 2020

The pigeon pea strains of
Bradyrhizobium
CC-1, CC-8, UASGR(S), and F4 were evaluated for nodulation, effectiveness for N
2
fixation, and H
2
oxidation with homologous and nonhomologous host plants. Strain CC-1 nodulated
Macroptilium atropurpureum, Vigna unguiculata, Glycine max
, and
G. soja
but did not nodulate
Pisum sativum, Phaseolus vulgaris, Trigonella foenum-graecum
, and
Trifolium repens
. Strain F4 nodulated
G. max
cv. Peking and PI 434937 (Malayan), but the symbioses formed were poor. Similarly,
G. max
cv. Peking, cv. Bragg, PI 434937, PR 13-28-2-8-7, and HM-1 were nodulated by strain CC-1, and symbioses were also poor.
G. max
cv. Williams and cv. Clark were not nodulated. H
2
uptake activity was expressed with pigeon pea and cowpea, but not with soybean.
G. max
cv. Bragg grown in Bangalore, India, in local soil not previously exposed to
Bradyrhizobium japonicum
formed nodules with indigenous
Bradyrhizobium
spp. Six randomly chosen isolates, each originating from a different nodule, formed effective symbioses with pigeon pea host ICPL-407, nodulated PR 13-28-2-8-7 soybean forming moderately effective symbioses, and did not nodulate Williams soybean. These results indicate the six isolates to be pigeon pea strains although they originated from soybean nodules. Host-determined nodulation of soybean by pigeon pea
Bradyrhizobium
spp. may depend upon the ancestral backgrounds of the cultivars. The poor symbioses formed by the pigeon pea strains with soybean indicate that this crop should be inoculated with
B. japonicum
for its cultivation in soils containing only pigeon pea
Bradyrhizobium
spp.
Legionella spp. in Puerto Rico cooling towers
Authors: Negrón-Alvíra A , Pérez-Suarez I , Hazen T C
Published: January 2020

Water samples from air conditioning cooling towers receiving different treatment protocols on five large municipal buildings in San Juan, P.R., were assayed for various Legionella spp. and serogroups by using direct immunofluorescence. Several water quality parameters were also measured for each sample. Guinea pigs were inoculated with water samples to confirm pathogenicity and recover viable organisms. Legionella pneumophila serogroups 1 to 6, L. bozemanii, L. micdadei, L. dumoffii, and L. gormanii were observed in at least one of the cooling towers. L. pneumophila was the most abundant species; its density reached 10(5) cells per ml, which is within the range that is considered potentially pathogenic to humans. A significantly higher density of L. pneumophila was observed in the cooling tower water that was not being treated with biocides. Percent respiration (INT) and total cell activity (acridine orange direct count) were inversely correlated with bacterial density. This study demonstrates that Legionella spp. are present in tropical air-conditioning cooling systems and that, without continuous biocide treatment, they may reach densities that present a health risk.
New Amylolytic Yeast Strains for Starch and Dextrin Fermentation
Authors: Laluce Cecília , Bertolini Maria Célia , Ernandes José Roberto , Martini Ann Vaughan , Martini Alessandro
Published: January 2020

Yeast strains capable of fermenting starch and dextrin to ethanol were isolated from samples collected from Brazilian factories in which cassava flour is produced. Considerable alcohol production was observed for all the strains selected. One strain (DI-10) fermented starch rapidly and secreted 5 times as much amylolytic enzyme than that observed for
Schwanniomyces alluvius
UCD 54-83. This strain and three other similar isolates were classified as
Saccharomyces cerevisiae
var.
diastaticus
by morphological and physiological characteristics and molecular taxonomy.
Product inhibition of immobilized Escherichia coli arising from mass transfer limitation
Authors: Stewart P S , Robertson C R
Published: January 2020

Mass transfer-limited removal of metabolic products led to product-inhibited growth of Escherichia coli that was immobilized in a model system. Comparison of the growth kinetics of immobilized and free-living cells revealed no further physiological differences between cells in these two modes of existence beyond those manifested in the local concentrations of substrate and product. Bacteria were retained on a microporous membrane in a dense, planar aggregate and were grown anaerobically on a glucose-based minimal medium. Radioisotope labeling of the immobilized cell mass with 35S was used to determine growth kinetic parameters. Growth rates in the immobilized cell layer were measured by an autoradiographic technique which allowed comparison of the size of the growing region with the rate of cell convection caused by growth. Immobilized cell growth rates and growth yields ranged from near maximal (0.56 h-1 and 39 g of dry cell weight/mol of glucose, respectively) to substantially reduced (0.15 h-1 and 15 g/mol). The depression of these kinetic parameters was attributed to product inhibition arising from mass transfer-limited removal of acidic waste products from the cell mass. A simple one-dimensional reaction-diffusion model, which incorporated data on the product-inhibited growth kinetics of free-living cells collected in a product-limited chemostat, satisfactorily predicted product inhibition of immobilized cell growth.
New naphthalene-degrading marine Pseudomonas strains
Authors: García-Valdés E , Cozar E , Rotger R , Lalucat J , Ursing J
Published: January 2020

Over 100 strains that utilized naphthalene as the only carbon and energy source were isolated from samples of marine sediments taken from a heavily polluted area. The isolates were characterized taxonomically and physiologically. Most of these strains belonged to the genus Pseudomonas, and seven of them did not fit any previous taxonomic description. They differed from type strains in a few biochemical characteristics and in the utilization of aromatic compounds. None had catechol 1,2-dioxygenase activity, and catechol 2,3-dioxygenase was responsible for the aromatic ring cleavage. DNA hybridization demonstrated a close relationship between two isolates and the Pseudomonas stutzeri type strain, and between five isolates and the Pseudomonas testosteroni type strain. On the basis of nutritional and enzymatic characteristics, it was assumed that the seven isolates represent new biovars belonging to the species P. testosteroni and P. stutzeri that are able to degrade aromatic hydrocarbons.
Identification of
Frankia
Strains by Direct DNA Hybridization of Crushed Nodules
Authors: Simonet Pascal , Le Nguyen Thi , Du Cros Eric Teissier , Bardin Rene
Published: January 2020

A hybridization procedure was developed to identify
Frankia
strains inside actinorhizae by direct probing of crushed root nodules. The probe consisted of an indigenous cryptic plasmid. This well-conserved, 8-kilobase plasmid was detected in
Frankia
isolates that were very close taxonomically (they possessed a very high DNA sequence homology). The probe did not hybridize to the DNA of
Frankia
isolates which did not carry the plasmid. Endophyte DNA was extracted by a modification of a technique originally developed for the detection of plasmids in
Frankia
isolates. The hybridization procedure applied to nodules collected in a stand of alder permitted determination of a distribution map of the plasmid-bearing
Frankia
strains.
Microbial metabolism of polycyclic aromatic hydrocarbons: isolation and characterization of a pyrene-degrading bacterium
Authors: Heitkamp M A , Franklin W , Cerniglia C E
Published: January 2020

Microbiological analyses of sediments located near a point source for petrogenic chemicals resulted in the isolation of a pyrene-mineralizing bacterium. This isolate was identified as a Mycobacterium sp. on the basis of its cellular and colony morphology, gram-positive and strong acid-fast reactions, diagnostic biochemical tests, 66.6% G + C content of the DNA, and high-molecular-weight mycolic acids (C58 to C64). The mycobacterium mineralized pyrene when grown in a mineral salts medium supplemented with nutrients but was unable to utilize pyrene as a sole source of carbon and energy. The mycobacterium grew well at 24 and 30 degrees C and minimally at 35 degrees C. No growth was observed at 5 or 42 degrees C. The mycobacterium grew well at salt concentrations up to 4%. Pyrene-induced Mycobacterium cultures mineralized 5% of the pyrene after 6 h and reached a maximum of 48% mineralization within 72 h. Treatment of induced and noninduced cultures with chloramphenicol showed that pyrene-degrading enzymes were inducible in this Mycobacterium sp. This bacterium could also mineralize other polycyclic aromatic hydrocarbons and alkyl- and nitro-substituted polycyclic aromatic hydrocarbons including naphthalene, phenanthrene, fluoranthene, 3-methylcholanthrene, 1-nitropyrene, and 6-nitrochrysene. This is the first report of a bacterium able to extensively mineralize pyrene and other polycyclic aromatic hydrocarbons containing four aromatic rings.
In situ survival of plasmid-bearing and plasmidless Pseudomonas aeruginosa in pristine tropical waters
Authors: Cruz-Cruz N E , Toranzos G A , Ahearn D G , Hazen T C
Published: January 2020

Two rare wild-type strains of Pseudomonas aeruginosa were mixed in membrane diffusion chambers and then introduced into a natural freshwater environment for 72 h. The plasmid-containing strain (R serotype 15) and the plasmidless strain (H serotype 5) had initial bacterial densities of 2 x 10(5) cells per ml. Samples collected from the chambers were analyzed for viable and direct counts and for acquired-resistance frequencies. Suspected transconjugant-to-donor ratios ranged from 0.5 to 1.3; transfer percentages ranged from 13 to 70%. [3H]thymidine uptake indicated DNA synthesis in both strains as well as in transconjugants. These studies indicate that rare wild-type bacterial strains with large plasmid loads can survive as well as can bacteria with low plasmid loads when exposed to the in situ conditions of a tropical freshwater habitat. These results also suggest that genetic modification of indigenous microbiota through conjugation or transformation is feasible when rare wild-type strains or genetically engineered microorganisms are released in large numbers in tropical aquatic ecosystems.
Inactivation of Giardia lamblia and Giardia canis cysts by combined and free chlorine
Authors: Kong L I , Swango L J , Blagburn B L , Hendrix C M , Williams D E , Worley S D
Published: January 2020

Free chlorine and a combined organic N-chloramine (3-chloro-4,4-dimethyl-2-oxazolidinone, compound 1) were compared for efficacy as disinfectants against an admixture of cysts of Giardia lamblia and Giardia canis in water solution under a variety of test conditions; variables were pH, temperature, and water quality. In general, compound 1 was found to reduce the giardial excystation in the solutions at lower concentration or shorter contact time at a given total chlorine concentration than did free chlorine.
Sensitivity of ruminal microorganisms to pentachlorophenol
Authors: Yokoyama M T , Johnson K A , Gierzak J
Published: January 2020

Pentachlorophenol (PCP) is used extensively as a biocidal agent, and there is considerable concern about the adverse effects of this compound in biological ecosystems. The effects of PCP on the growth and fermentative activity of cultures of mixed ruminal microorganisms and the sensitivity of 14 ruminal bacterial species to PCP in pure culture were examined in this study. Increasing concentrations of PCP (9.4 to 375.4 microM) depressed growth and propionate concentrations in cultures of mixed ruminal microorganisms. Wide differences in the sensitivities of ruminal bacterial strains to various concentrations of PCP were observed. Cellulolytic strains were highly sensitive to PCP, while amylolytic, sugar-utilizing, and intermediate acid-utilizing strains were more resistant. Growth of major succinate-producing strains was depressed by PCP. Strains which depend on substrate level phosphorylation appeared to be more resistant. The data suggest that the adverse effects of PCP on ruminal microorganisms may be the result of its role as both an uncoupler of electron transport and a protonophore.
Zn
2+
Increases Siderophore Production in
Azotobacter vinelandii
Authors: Huyer Marianne , Page William J.
Published: January 2020

When
Azotobacter vinelandii
was grown in the presence of low levels of iron, the addition of 20 or 40 μM ZnSO
4
caused earlier production of the catechol siderophores and a dramatic increase in the amount of azotobactin. The level of cellular iron was not significantly lowered in Zn
2+
-grown cells, which suggested that Zn
2+
was not causing more severe, or earlier, iron limitation. Also, Zn
2+
did not appear to affect production of the high-molecular-weight outer membrane iron-repressible proteins that presumably function as ferrisiderophore receptors. Spectrophotometric examination of ion binding to the siderophores revealed that while the siderophores appeared to bind Zn
2+
, only in the case of azotochelin was iron unable to completely overcome any Zn
2+
-induced changes in the absorption spectra. This appeared to rule out direct competition of Zn
2+
with iron for binding to the siderophores.
55
Fe uptake was depressed both in Zn
2+
-grown cells and in Zn
2+
-free cells to which Zn
2+
was added during the uptake assay, except with azotobactin, with which the level of
55
Fe uptake by Zn
2+
-grown cells was close to control levels. These results suggested two possible sites where Zn
2+
could be acting, one involving the biosynthesis of siderophores and possibly the genetic regulation of the iron assimilation system and the other involving an internal point common to iron assimilation by both high- and low-affinity iron uptake.
Production of 5′ Nucleotide by Using Halophilic Nuclease H Preferentially Adsorbed on Flocculated Cells of the Halophile
Micrococcus varians
subsp.
halophilus
Authors: Onishi Hiroshi , Kamekura Masahiro , Yokoi Haruhiko , Kobayashi Takekazu
Published: January 2020

A bioreactor with a column of flocculated cells of the moderate halophile
Micrococcus varians
subsp.
halophilus
which adsorbed the halophilic nuclease H was designed to be used in the production of 5′ nucleotides from RNA. A remarkable characteristic of the flocculated cells was that they preferentially adsorbed much exogenous nuclease, excluding adsorbed 5′ nucleotidase. Furthermore, desalting treatment of the flocculated cells in the presence of 2% MgSO
4
· 7H
2
O gave rise to selective inactivation of 5′ nucleotidase without the loss of nuclease H activity, and 5′-guanylic acid was produced with the bioreactor.
Methods for improved recovery of Listeria monocytogenes from cheese
Authors: Yousef A E , Ryser E T , Marth E H
Published: January 2020

Method of homogenization (Waring blender versus stomacher), type of diluent (tryptose broth [TB] versus aqueous 2% trisodium citrate), and temperature of diluent (20 versus 40 degrees C) were compared for recovery of Listeria monocytogenes from freshly made and ripened Colby cheese. By using direct plating on McBride listeria agar, significantly higher numbers of L. monocytogenes were recovered when cheese samples were (i) homogenized for 2 min with the blender rather than the stomacher (P less than 0.01), (ii) diluted in trisodium citrate rather than TB (P less than 0.01), and (iii) diluted in diluents at 40 rather than 20 degrees C (P less than 0.05). Based on these results, a new diluent/enrichment medium was developed by adding 2% trisodium citrate to TB (TBC). Despite superior results with the blender, biosafety concerns led to use of the stomacher for homogenization of cheese samples; hence, the stomaching time was increased to 3 min. Results obtained by direct plating indicated that recovery of L. monocytogenes from Colby cheese and from curd samples taken during manufacture of brick cheese increased when samples were diluted 1:10 in TBC at 45 degrees C and stomached for 3 min, as compared with similarly treated samples diluted in TB at 25 degrees C. A similar comparison of both diluents for recovery of L. monocytogenes from cold-pack cheese food yielded bacterial counts which were not significantly different. Recovery of L. monocytogenes from cold-enriched (at 4 degrees C for up to 8 weeks) samples of Colby cheese and cold-pack cheese food was generally similar for samples homogenized in TBC or TB.
Kinetics of Insoluble Cellulose Fermentation by Continuous Cultures of
Ruminococcus albus
Authors: Pavlostathis Spyros G. , Miller Terry L. , Wolin Meyer J.
Published: January 2020

Data from analyses of continuous culture fermentation of insoluble cellulose by
Ruminococcus albus
7 were used to derive constants for the rate of cellulose hydrolysis and fermentation, growth yield, and maintenance. Cellulose concentration was 1% in the nutrient reservoir, and hydraulic retention times of 0.5, 1.0, 1.5, 1.75, and 2.0 days were used. Concentrations of reducing sugars in the cultures were negligible (less than 1%) compared with the amount of hydrolyzed cellulose, indicating that cellulose hydrolysis was the rate-limiting step of the fermentation. The rate of utilization of cellulose depended on the steady-state concentration of cellulose and was first order with a rate constant (
k
) of 1.18 day
−1
. The true microbial growth yield (
Y
) was 0.11 g g
−1
, the maintenance coefficient (
m
) was 0.10 g g
−1
h
−1
, and the maximum
Y
ATP
was 7.7 g of biomass (dry weight) mol of ATP
−1
.