bluuebunny/crossref_metadata_2025 huggingface dataset:
Marking the rhizopseudomonas strain 7NSK2 with a Mu d(lac) element for ecological studies
Authors: Höfte M , Mergeay M , Verstraete W
Published: January 2020

The mini Mu element Mu dII1681, which contains the lac operon genes and a kanamycin resistance gene, was inserted in the chromosome of plant growth-beneficial Pseudomonas aeruginosa 7NSK2 to construct a marked strain (MPB1). In MPB1, beta-galactosidase is permanently expressed under the culture conditions used. The MPB1 strain could be recovered with an efficiency of about 100% from a sandy loam soil on 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside medium containing sebacic acid and kanamycin. The limit of detection is about 10 CFU/g of soil. A detailed comparison was made between the wild-type strain 7NSK2 and the Mu dII1681-containing MPB1 strain. The results showed that no genes essential for growth, siderophore production, survival in sterile and nonsterile conditions, plant growth stimulation, or root colonization had been damaged in the MPB1 strain, which means that MPB1 can reliably be used for ecological studies in soil. MPB1 survived well at 4 or 28 degrees C but died off relatively rapidly in air-dried soil or at subzero temperatures. In these conditions, however, the MPB1 strain did not completely disappear from the soil but survived at a very low level of about 100 CFU/g of soil for more than 3 months. This observation stresses the need for very sensitive counting methods for ecological studies and for the evaluation of released microorganisms. Maize was inoculated with MPB1 via seed inoculation or soil inoculation. Upon seed inoculation, only the upper root parts were effectively colonized, while soil inoculation resulted in a complete colonization of the root system.
Direct detection of Salmonella spp. in estuaries by using a DNA probe
Authors: Knight I T , Shults S , Kaspar C W , Colwell R R
Published: January 2020

A method for direct detection of Salmonella spp. in water was developed by using a commercially available DNA probe. Particulate DNA was extracted from 500- to 1,500-ml water samples collected from New York Harbor and Chesapeake Bay and used as a substrate for a salmonella-specific DNA probe in dot blot assays. The method detected salmonellae in water samples from 12 of 16 sites, including 6 sites where salmonellae could not be cultured. The specificity of the probe was evaluated, and cross-hybridization, although negligible, was used to set detection limits for the assay. Salmonella DNA bound the probe quantitatively, and from these results Salmonella DNA in the total particulate DNA in environmental samples could be estimated. The data obtained in this study indicate that Salmonella spp. often are not detected in water samples by culture methods, even when they are present in significant numbers.
Enumeration of Anaerobic Chytridiomycetes as Thallus-Forming Units: Novel Method for Quantification of Fibrolytic Fungal Populations from the Digestive Tract Ecosystem
Authors: Theodorou Michael K. , Gill Margaret , King-Spooner Catherine , Beever David E.
Published: January 2020

An endpoint dilution procedure, based on the technique of most probable numbers, was developed to enumerate anaerobic chytridiomycetes as thallus-forming units. The method does not distinguish between zoospores and thalli, but does permit enumeration of fungal populations with respect to their ability to digest plant cell walls. Fibrolytic populations in batch culture, ruminal contents, and feces were compared by relating viable counts to the dry matter content of enumerated samples (i.e., thallus-forming units per gram of dry matter). Batch cultures of
Neocallimastix
sp. strain R1 grown on wheat straw were used to assess the enumeration procedure and to demonstrate the potential of the technique for quantification of anaerobic fungi in vivo. Determination of total ruminal contents from steers enabled the quantification of the entire population of fiber-degrading anaerobic fungi in the reticulorumen. The enumeration procedure revealed substantial populations of fibrolytic anaerobic fungi in fresh and air-dried feces. Populations in fresh feces were equivalent to those in ruminal contents, but declined exponentially with time in dry feces. Minimum values were obtained from dry feces 90 days after drying, and anaerobic fungi were detectable for up to 210 days thereafter.
Isolation of
Rhizobium leguminosarum
(biovar
trifolii
) Strains from Ethiopian Soils and Symbiotic Effectiveness on African Annual Clover Species
Authors: Friedericks J. B. , Hagedorn C. , Vanscoyoc S. W.
Published: January 2020

Strains of
Rhizobium leguminosarum
(biovar
trifolii
) isolated from two Ethiopian soils or obtained from a commercial source were evaluated for symbiotic effectiveness on five African annual clover species. Numerous
Rhizobium trifolii
strains that exhibited varying levels of symbiotic effectiveness were isolated from both soils (a nitosol and a vertisol), and it was possible to identify strains that were highly effective for each clover species. The soil isolates were, as a group, superior to the strains from the commercial source. Several
R. trifolii
strains were found to be effective on more than one clover species, and there appeared to be at least two and possibly three distinct cross-inoculation effectiveness groups.
Cross-reactive and specific monoclonal antibodies against cellobiohydrolases I and II and endoglucanases I and II of Trichoderma reesei
Authors: Nieves R A , Himmel M E , Todd R J , Ellis R P
Published: January 2020

Splenocytes derived from mice inoculated with a commercial cellulase preparation or purified cellulases were fused with a stable myeloma cell line (SP2/0). Specific monoclonal antibodies to cellobiohydrolases I and II and endoglucanases I and II were established. In addition to specific monoclonal antibodies, we were also able to establish stable hybridoma cell lines which produced monoclonal antibodies that recognized similar epitopes possessed by two or more of the above cellulases. By obtaining monospecific antibodies for all four individual cellulases, the role and function of the individual cellulases can thus be studied in greater detail.
Shiga-like-toxin-producing Escherichia coli in retail meats and cattle in Thailand
Authors: Suthienkul O , Brown J E , Seriwatana J , Tienthongdee S , Sastravaha S , Echeverria P
Published: January 2020

Specific DNA probes were used to identify Shiga-like toxin I (SLT I)- and SLT II-producing Escherichia coli in vegetables, meats, cattle, and farm animals in Thailand. SLT-producing E. coli was isolated from 9% of market beef specimens, from 8 to 28% of fresh beef specimens at slaughterhouses, and from 11 to 84% of fecal specimens from cattle. Animals were frequently infected with several different SLT-producing E. coli types that hybridized with either the SLT I, SLT II, or both SLT probes. Of 119 SLT-producing E. coli isolates, 24% hybridized with the SLT I probe, 31% hybridized with the SLT II probe, and 44% hybridized with both SLT probes. The enterohemorrhagic E. coli plasmid probe hybridized with 64% (68 of 106) of SLT-producing E. coli isolates from food and cattle and with 8% (17 of 201) of E. coli isolates from pigs. No SLT-producing E. coli was detected in pigs. Seventy-six percent (26 of 34) of E. coli isolates that hybridized with the SLT II probe were cytotoxic to Vero but not to HeLa cells, suggesting that they produced the variant of SLT II. The high prevalence of SLT-producing E. coli in beef-producing animals suggests that exposure to animals and eating beef may pose a health risk for acquiring enterohemorrhagic E. coli infections in Thailand.
Metabolism of Dibenzofuran by
Pseudomonas
sp. Strain HH69 and the Mixed Culture HH27
Authors: Fortnagel Peter , Harms Hauke , Wittich Rolf-Michael , Krohn Sabine , Meyer Holger , Sinnwell Volker , Wilkes Heinz , Francke Wittko
Published: January 2020

A
Pseudomonas
sp. strain, HH69, and a mixed culture, designated HH27, were isolated by selective enrichment from soil samples. The pure strain and the mixed culture grew aerobically on dibenzofuran as the sole source of carbon and energy. Degradation proceeded via salicylic acid which was branched into the gentisic acid and the catechol pathway. Both salicylic acid and gentisic acid accumulated in the culture medium of strain HH69. The acids were slowly metabolized after growth ceased. The enzymes responsible for their metabolism showed relatively low activities. Besides the above-mentioned acids, 2-hydroxyacetophenone, benzopyran-4-one (chromone), several 2-substituted chroman-4-ones, and traces of the four isomeric monohydroxydiben-zofurans were identified in the culture medium. 2,2′,3-Trihydroxybiphenyl was isolated from the medium of a dibenzofuran-converting mutant derived from parent strain HH69, which can no longer grow on dibenzofuran. This gives evidence for a novel type of dioxygenases responsible for the attack on the biarylether structure of the dibenzofuran molecule. A
meta
-fission mechanism for cleavage of the dihydroxylated aromatic nucleus of 2,2′,3-trihydroxybiphenyl is suggested as the next enzymatic step in the degradative pathway.
Screening of symbiotic frankiae for host specificity by restriction fragment length polymorphism analysis
Authors: Nittayajarn A , Mullin B C , Baker D D
Published: January 2020

Restriction fragment length polymorphism analysis of numerous Frankia strains, using a nifDH probe, separated the strains into three distinct groups based on hybridization patterns. The groups identified in this study were well correlated with host specificity groups identified in earlier cross-inoculation studies.
Purification and properties of an endo-1,4-beta-glucanase translated from a Clostridium josui gene in Escherichia coli
Authors: Fujino T , Sasaki T , Ohmiya K , Shimizu S
Published: January 2020

An endoglucanase encoded by a gene of Clostridium josui was expressed in Escherichia coli and purified. The homogeneous enzyme, with a molecular weight of 39,000, revealed maximum endoglucanase activity at pH 7.2 to 7.5 and a temperature of 65 to 70 degrees C. The enzyme was stable at a temperature lower than 45 degrees C (the growth temperature of the bacterium) in the range of pH 4.5 to 9.0. The amino acid sequence of the enzyme at the N terminus was Val-Glu-Glu-Asp-Ser-Ser-His-Leu-Ile-Thr-Asn-Gln-Ala-Lys-Lys----. The enzyme hydrolyzed cellotetraose to cellobiose and then transferred cellobiose to the residual cellotetraose. The resulting cellohexaose was cleaved to cellotriose.
Direct Determination of Nitrification in Marine Waters by Using the Short-Lived Radioisotope of Nitrogen,
13
N
Authors: Capone Douglas G. , Horrigan Sarah G. , Dunham Susan E. , Fowler Joanna
Published: January 2020

Biological oxidation of radiolabeled
13
NH
4
+
(half-life = 10 min) was observed within minutes in assays of an estuarine ammonium oxidizer and in natural populations of nitrifiers in coastal waters. Our estimates of turnover of the ammonium pool and rates of nitrification based on experiments using
13
N are consistent with previous values in the literature based on longer-term
15
N tracer experiments or on indirect methods and thus provide corroboration for the estimates by other researchers.
Chromium(VI)-resistant yeast isolated from a sewage treatment plant receiving tannery wastes
Authors: Baldi F , Vaughan A M , Olson G J
Published: January 2020

A Cr(VI)-resistant yeast, designated strain DBVPG 6502, was isolated from a sewage treatment plant receiving wastes from tannery industries in Italy. The strain was tentatively identified as a species of Candida based on morphological and physiological analyses. This strain was highly resistant to Cr(VI) when compared with eight other yeast species, growing at Cr(VI) concentrations of up to 500 micrograms/ml (10 mM). This resistance was constitutive. The Cr(VI)-resistant yeast did not reduce Cr(VI) to Cr(III) species under aerobic conditions. The yeast showed very little accumulation of Cr(VI). Consequently, the mechanism of resistance of the yeast to Cr(VI) appears to involve reduced accumulation of Cr, as has been shown in Cr(VI)-resistant bacteria.
Microcosm for assessing survival of genetically engineered microorganisms in aquatic environments
Authors: Awong J , Bitton G , Chaudhry G R
Published: January 2020

Laboratory-contained microcosms are important for studying the fate and survival of genetically engineered microorganisms. In this study, we describe a simple aquatic microcosm that utilizes survival chambers in a flowthrough or static renewal system. The model was used to study the survival of genetically engineered and wild-type strains of Escherichia coli and Pseudomonas putida in the lake water environment. Temperature-dependent studies indicated that the genetically engineered microorganisms survived better or at least as well as their wild-type counterparts at 15, 25, and 30 degrees C. The genetic determinants of the genetically engineered microorganisms also remained fairly stable within the host cell under the tested conditions. In the presence of organisms indigenous to lake water, E. coli was eliminated after 20 days, whereas P. putida showed an initial decline but was able to stabilize its population after 5 days. A herbicide, Hydrothol-191, caused a significant decline in numbers of P. putida, but no significant difference was observed between the genetically engineered microorganisms and the wild-type strain. The microcosm described is simple, can be easily adapted to study a variety of environmental variables, and has the advantage that the organisms tested are constantly exposed to test waters that are continuously renewed.
Antigenic nature of the chloride-stimulated cellobiosidase and other cellulases of Fibrobacter succinogenes subsp. succinogenes S85 and related fresh isolates
Authors: Huang L , McGavin M , Forsberg C W , Lam J S , Cheng K J
Published: January 2020

Polyclonal and monoclonal antibodies to the Cl-stimulated cellobiosidase of Fibrobacter succinogenes subsp. succinogenes S85 reacted with numerous proteins of both higher and lower molecular weights from F. succinogenes subsp. succinogenes S85, but not with Escherichia coli proteins, and only one protein each from Butyrivibrio fibrisolvens and Ruminococcus albus. Different profiles were observed for Western blots (immunoblots) of peptide digests of both the purified enzyme from F. succinogenes and immunoreactive proteins of higher and lower molecular weights, demonstrating that they were different proteins. Therefore, F. succinogenes appeared to produce numerous proteins with one or more common antigenic determinants. However, with the exception of Cl-stimulated cellobiosidase, none were cellulases that have been characterized. An affinity-purified polyclonal antibody to Cl-stimulated cellobiosidase reacted with numerous proteins in cells of each of three fresh isolates of F. succinogenes subsp. succinogenes and one of F. succinogenes subsp. elongata when analyzed by Western blotting. Antibodies to periplasmic cellodextrinase, endoglucanase 2 (EG2), and EG3, when reacted in Western blots with the various cellulases, including Cl-stimulated cellobiosidase, revealed limited antigenic similarity among the different proteins and none with either B. fibrisolvens or R. albus proteins. The periplasmic cellodextrinase antibody reacted with an antigen with a size corresponding to cellodextrinase in each of the three F. succinogenes subsp. succinogenes isolates but not with any antigens from the F. succinogenes subsp. elongata isolate. The anti-EG2 antibody reacted with single antigens in each of the four isolates, while the anti-EG3 antibody reacted with only one of the four isolates.(ABSTRACT TRUNCATED AT 250 WORDS)
Comparison of the limulus amebocyte lysate test and gas chromatography-mass spectrometry for measuring lipopolysaccharides (endotoxins) in airborne dust from poultry-processing industries
Authors: Sonesson A , Larsson L , Schütz A , Hagmar L , Hallberg T
Published: January 2020

The lipopolysaccharide (endotoxin) content in airborne dust samples from three different poultry slaughterhouses was determined with both the chromogenic Limulus amebocyte lysate assay and gas chromatography-mass spectrometry analysis of lipopolysaccharide-derived 3-hydroxy fatty acids. Gram-negative cell walls were also measured by using two-dimensional gas chromatography/electron-capture analysis of diaminopimelic acid originating from the peptidoglycan. The correlation between the results of the Limulus assay and those of gas chromatography-mass spectrometry for determination of the lipopolysaccharide content in the dust samples was poor, whereas a good correlation was obtained between lipopolysaccharide and diaminopimelic acid concentrations with the gas chromatographic methods. The results suggest that it is predominantly cell-wall-dissociated lipopolysaccharides that are measured with the Limulus assay, whereas the gas chromatographic methods allow determination of total concentrations of lipopolysaccharide, including Limulus-inactive lipopolysaccharide, gram-negative cells, and cellular debris.
Improved expression of human interleukin-2 in high-cell-density fermentor cultures of Escherichia coli K-12 by a phosphotransacetylase mutant
Authors: Bauer K A , Ben-Bassat A , Dawson M , de la Puente V T , Neway J O
Published: January 2020

A fluoroacetate-resistant mutant of Escherichia coli K-12 (MM-294) accumulated less acetate in the medium during growth to high cell density in fermentor cultures and was shown to be defective in its phosphotransacetylase activity. The mutant had an improved ability to continue growing during induction of interleukin-2 (IL-2) synthesis, and in fermentor cultures it gave a higher level of specific IL-2 accumulation than its parent during expression under control of the temperature-sensitive pL promoter. In flask cultures at lower cell density, the mutant again produced less acetate than the parent, although both showed a much lower level of acetate accumulation than that seen in fermentors at high cell density. Both showed a higher specific expression level of IL-2 in flask cultures, and there was a greater difference between the mutant and its parent in the final extent of specific IL-2 accumulation in fermentor cultures compared with flask cultures. Thus, the concentration of acetate in the medium, which was much higher in fermentor cultures (greater than or equal to 300 mM after 5 h of induction) than in flask cultures (less than or equal to mM) of the parent organism, was a significant factor in limiting expression of the heterologous protein product, IL-2. The acetate kinase-phosphotransacetylase pathway was therefore a major source of acetate formation in these cultures. Blocking this pathway improved accumulation of IL-2 and did not slow growth.
Strain-Specific Inhibition of
nod
Gene Induction in
Bradyrhizobium japonicum
by Flavonoid Compounds
Authors: Kosslak Renee M. , Joshi Rita S. , Bowen Benjamin A. , Paaren Herbert E. , Appelbaum Edward R.
Published: January 2020

A broad-host-range plasmid, pEA2-21, containing a
Bradyrhizobium japonicum nodABC'-'lacZ
translational fusion was used to identify strain-specific inhibitors of the genes required for soybean nodulation, the common
nod
genes. The responses of type strains of
B. japonicum
serogroups USDA 110, USDA 123, USDA 127, USDA 129, USDA 122, and USDA 138 to
nod
gene inhibitors were compared. Few compounds inhibited
nod
gene expression in
B. japonicum
USDA 110. In contrast,
nod
gene expression in strains belonging to several other serogroups was inhibited by most of the flavonoids tested. However, the application of two of these strain-specific compounds, chrysin and naringenin, had little effect on the pattern of competition between indigenous and inoculum strains of
B. japonicum
in greenhouse and field trials. Preliminary studies with radiolabeled chrysin and naringenin suggest that the different responses to
nod
gene inhibitors may be partly due to the degree to which plant flavonoids can be metabolized by each strain.
Parasitic hazard with sewage sludge applied to land
Authors: Barbier D , Perrine D , Duhamel C , Doublet R , Georges P
Published: January 2020

A modification of the FAUST technique allowed a highly regular recovery of Taenia saginata eggs from sewage sludge, as well as their quantification. Despite the low viability (8%) noted, the viable T. saginata egg level remains high (20.10(6)/ha) and offers a serious risk for cattle even after a 3-week "no-grazing" period.
Particulate DNA in Smoker Fluids: Evidence for Existence of Microbial Populations in Hot Hydrothermal Systems
Authors: Straube W. L. , Deming J. W. , Somerville C. C. , Colwell R. R. , Baross J. A.
Published: January 2020

As part of an interdisciplinary study of hydrothermal vents on the Endeavour Segment of the Juan de Fuca Ridge, we used the submersible
ALVIN
to collect 57 fluid samples in titanium syringes and Go Flo Niskin bottles from 17 different hot vents (smokers and flanges) and their environs for the purpose of extracting particulate DNA. The relative purity of the vent fluids collected was determined by Mg content as an indicator of seawater entrainment. Particulate material concentrated from these samples was lysed enzymatically (enz) and by a combination of enzyme and French press treatment (fp). Concentrations of partially purified DNA recovered from these lysates were determined spectrofluorometrically by using the dye Hoechst 33258. Ambient seawater surrounding the vents was found to contain low DNA concentrations, 0.18 to 0.32 ng of DNA per ml (
n
= 4; mean
enz
= 0.23 ± 0.05; mean
fp
= 0.26 ± 0.05), while low-temperature vent samples yielded significantly higher concentrations of 0.37 to 2.12 ng of DNA per ml (
n
= 4; mean
enz
= 0.97 ± 0.68; mean
fp
= 1.05 ± 0.54). Although DNA recovery values from superheated (210 to 345°C) flange samples (mean
enz
= 0.14 ± 0.10; mean
fp
= 0.12 ± 0.14) were not significantly different from ambient seawater values, most of the superheated (174 to 357°C) smoker fluid samples contained particulate DNA in concentrations too high to be attributable to entrained seawater. Detailed sampling at one smoker site demonstrated not only the existence of significant levels of particulate DNA in the superheated smoker fluids but also the presence of an elevated microbial population in the buoyant plume 20 to 100 m above the smoker. These results underscore the heterogeneity of smoker environments within a given hydrothermal vent field and indicate that microorganisms exist in some superheated fluids.
Fluorescent-antibody method useful for detecting viable but nonculturable Salmonella spp. in chlorinated wastewater
Authors: Desmonts C , Minet J , Colwell R , Cormier M
Published: January 2020

An indirect fluorescent-antibody (IFA) technique, which employed adsorbed Behring polyvalent I O antiserum, was used to detect Salmonella spp. in environmental water systems. The IFA method used in this study detected 95% of Salmonella serotypes encountered in human infections in France, with a sensitivity threshold of 7.5 x 10(3) bacteria per ml of wastewater. Specificity was assessed by testing IFA against Salmonella-free seawater and a variety of bacteria other than Salmonella spp. When used to examine raw and chlorinated wastewater over a 2-month period, the IFA method was successful in detecting Salmonella spp. in all 12 of the samples examined, with total numbers determined to be 4.5 x 10(5) to 3.3 x 10(7) salmonellae per 100 ml. In comparison, for the same samples, enumeration by culture, using the most-probable-number technique, was effective in detecting Salmonella spp. in only four of eight raw-water samples and one of four chlorinated water samples tested. Three samples were further tested by using the direct viable count procedure combined with IFA and results showed that 5 to 31.5% of the Salmonella spp. enumerated by this method in chlorinated water were substrate responsive.
Specificity of Octopine Uptake by
Rhizobium
and
Pseudomonas
Strains
Authors: Bergeron Janique , MacLeod Robert A. , Dion Patrice
Published: January 2020

The octopine-utilizing strain
Agrobacterium tumefaciens
B6S3 and three nonagrobacteria which had the capacity to utilize this opine were compared for octopine uptake. The characteristics of uptake by
Rhizobium meliloti
A3 and strain B6S3 were similar. In both bacteria, uptake activity was inducible by octopine and by the related opine octopinic acid, and competition assays showed that these two opine substrates were accepted by the same uptake system with an equivalent affinity. Cells of
Pseudomonas putida
203 accumulated octopine against a concentration gradient, and this activity was induced specifically by octopine. While strain 203 did not utilize octopinic acid, a spontaneous mutant with a combined capacity for octopine and octopinic acid utilization was obtained. Both opines induced octopine uptake by this mutant, but octopinic acid was not a substrate for the induced system. Thus, the
Pseudomonas
uptake system exhibited a different specificity for octopine than the corresponding
Agrobacterium
system. The nonfluorescent pseudomonad GU187j, which utilized the three related opines octopine, octopinic acid, and nopaline, was constitutive for octopine uptake. Strain GU187j possessed a system which accepted these three opines, but not arginine or ornithine, with a similar affinity.
Transconjugation between Bacteria in the Digestive Tract of the Cutworm
Peridroma saucia
Authors: Armstrong John L. , Wood Nathan D. , Porteous L. Arlene
Published: January 2020

Transconjugants arising from transfer of plasmid R388::Tn
1721
between donor and recipient strains of
Enterobacter cloacae
were detected in samples from the digestive tracts and fecal pellets of variegated cutworms (
Peridroma saucia
).
Hydrocarbon Mineralization in Sediments and Plasmid Incidence in Sediment Bacteria from the Campeche Bank
Authors: Leahy Joseph G. , Somerville Charles C. , Cunningham Kelly A. , Adamantiades Grammenos A. , Byrd Jeffrey J. , Colwell Rita R.
Published: January 2020

Rates of degradation of radiolabeled hydrocarbons and incidence of bacterial plasmid DNA were investigated in sediment samples collected from the Campeche Bank, Gulf of Mexico, site of an offshore oil field containing several petroleum platforms. Overall rates of mineralization of [
14
C]hexadecane and [
14
C]phenanthrene measured for sediments were negligible; <1% of the substrate was converted to CO
2
in all cases. Low mineralization rates are ascribed to nutrient limitations and to lack of adaptation by microbial communities to hydrocarbon contaminants. Plasmid frequency data for sediment bacteria similarly showed no correlation with proximity to the oil field, but, instead, showed correlation with water column depth at each sampling site. Significant differences between sites were observed for proportion of isolates carrying single or multiple plasmids and mean number of plasmids per isolate, each of which increased as a function of depth.
Liquid-to-Gas Mass Transfer in Anaerobic Processes: Inevitable Transfer Limitations of Methane and Hydrogen in the Biomethanation Process
Authors: Pauss André , Andre Gérald , Perrier Michel , Guiot Serge R.
Published: January 2020

Liquid-to-gas mass transfer in anaerobic processes was investigated theoretically and experimentally. By using the classical definition of

k
L
a

, the global volumetric mass transfer coefficient, theoretical development of mass balances in such processes demonstrates that the mass transfer of highly soluble gases is not limited in the usual conditions occurring in anaerobic fermentors (low-intensity mixing). Conversely, the limitation is important for poorly soluble gases, such as methane and hydrogen. The latter could be overconcentrated to as much as 80 times the value at thermodynamic equilibrium. Such overconcentrations bring into question the biological interpretations that have been deduced solely from gaseous measurements. Experimental results obtained in three different methanogenic reactors for a wide range of conditions of mixing and gas production confirmed the general existence of low mass transfer coefficients and consequently of large overconcentrations of dissolved methane and hydrogen (up to 12 and 70 times the equilibrium values, respectively). Hydrogen mass transfer coefficients were obtained from the direct measurements of dissolved and gaseous concentrations, while carbon dioxide coefficients were calculated from gas phase composition and calculation of related dissolved concentration. Methane transfer coefficients were based on calculations from the carbon dioxide coefficients. From mass balances performed on a gas bubble during its simulated growth and ascent to the surface of the liquid, the methane and carbon dioxide contents in the gas bubble appeared to be controlled by the bubble growth process, while the bubble ascent was largely responsible for a slight enrichment in hydrogen.
Properties of 2,3-Butanediol Dehydrogenases from
Lactococcus lactis
subsp.
lactis
in Relation to Citrate Fermentation
Authors: Crow Vaughan L.
Published: January 2020

Two 2,3-butanediol dehydrogenases (enzymes 1 and 2; molecular weight of each, 170,000) have been partially purified from
Lactococcus lactis
subsp.
lactis
(
Streptococcus diacetylactis
) D10 and shown to have reductase activity with either diacetyl or acetoin as the substrate. However, the reductase activity with 10 mM diacetyl was far greater for both enzymes (7.0- and 4.7-fold for enzymes 1 and 2, respectively) than with 10 mM acetoin as the substrate. In contrast, when acetoin and diacetyl were present together, acetoin was the preferred substrate for both enzymes, with enzyme 1 showing the more marked preference for acetoin.
meso
-2,3-Butanediol was the only isomeric product, with enzyme 1 independent of the substrate combinations. For enzyme 2, both the
meso
and optical isomers of 2,3-butanediol were formed with acetoin as the substrate, but only the optical isomers were produced with diacetyl as the substrate. With batch cultures of strain D10 at or near the point of citrate exhaustion, the main isomers of 2,3-butanediol present were the optical forms. If the pH was sufficiently high (>pH 5), acetoin reduction occurred over time and was followed by diacetyl reduction, and
meso
-2,3-butanediol became the predominant isomer. Interconversion of the optical isomers into the
meso
isomer did occur. The properties of 2,3-butanediol dehydrogenases are consistent with diacetyl and acetoin removal and the appearance of the isomers of 2,3-butanediol.
Bacterioplankton Growth on Fractions of Dissolved Organic Carbon of Different Molecular Weights from Humic and Clear Waters
Authors: Tranvik Lars J.
Published: January 2020

The ability of fractions of dissolved organic carbon (DOC) of different molecular weights (MW) to support bacterial growth was studied in batch culture experiments. Natural pelagic bacteria were inoculated into particle-free (0.2-μm filtered) water, taken from 10 oligotrophic lakes of differing humic content, and either used without further treatments or ultrafiltered to remove DOC of >10,000 MW or >1,000 MW. Stationaryphase abundance of bacteria in the cultures was used as an estimate of bacterial carrying capacity. High-MW DOC (>10,000) comprised an increasing fraction of total DOC with increasing total DOC and humic content of the lakes. High-MW DOC was generally more available to bacteria (i.e., more bacteria were produced per unit of organic carbon initially present) than low-MW (<10,000) DOC. The availability to bacteria of this high-MW DOC decreased with increasing humic content. However, although less available in humic lakes than in clearwater lakes, the higher abundance of high-MW DOC made it quantitatively more important as a bacterial substrate; i.e., a larger fraction of the total bacterial yield of the cultures was due to high-MW DOC compounds in humic lakes than in clearwater lakes. On the average, 48% of bacterial growth occurred at the expense of DOC of <10,000 MW. DOC of <1,000 MW was responsible for an average of 22% of bacterial growth, with no significant correlation to humic content and DOC concentration of lakes. The DOC which supports bacterial growth, as well as the total DOC, is of different quality in humic and clearwater lakes.
Effect of Cetylpyridinium Chloride on Microbial Adhesion to Hexadecane and Polystyrene
Authors: Goldberg Sarit , Konis Yoel , Rosenberg Mel
Published: January 2020

Microbial adhesion at the oil-water interface is a subject of both basic interest (e.g., as a technique for the measurement of hydrophobicity) and applied interest (e.g., for use in two-phase oil-water mouthwashes for the desorption of oral microorganisms). In general, surfactants inhibit microbial adhesion to oils and other hydrophobic surfaces. In the present study, we demonstrated that the cationic surfactant cetylpyridinium chloride (CPC) significantly enhanced microbial adhesion to hexadecane and various oils, as well as to the solid hydrophobic surface polystyrene. CPC increased adhesion to hexadecane of
Escherichia coli, Candida albicans
and
Acinetobacter calcoaceticus
MR-481 and of expectorated oral bacteria from near 0% to over 90%. The CPC concentration required for optimal enhancement of adhesion was a function of the initial cell density. This phenomenon was inhibited by high salt concentrations and, in the case of
E. coli
, by a low pH. CPC-pretreated cells were able to bind to hexadecane, but CPC-pretreated hexadecane was unable to bind untreated cells. Another cationic, surface-active antimicrobial agent, chlorhexidine gluconate, was similarly able to promote microbial adhesion to hexadecane. The results suggest that (i) CPC enhances microbial adhesion to hexadecane by binding via electrostatic interactions at the cell surface, thus diminishing surface charge and increasing cell surface hydrophobicity, and (ii) this phenomenon may have applications in oral formulations and in the use of hydrocarbon droplets as a support for cell immobilization.
Genes encoding mercuric reductases from selected gram-negative aquatic bacteria have a low degree of homology with merA of transposon Tn501
Authors: Barkay T , Gillman M , Liebert C
Published: January 2020

An investigation of the Hg2+ resistance mechanism of four freshwater and four coastal marine bacteria that did not hybridize with a mer operonic probe was conducted (T. Barkay, C. Liebert, and M. Gillman, Appl. Environ. Microbiol. 55:1196-1202, 1989). Hybridization with a merA probe, the gene encoding the mercuric reductase polypeptide, at a stringency of hybridization permitting hybrid formation between evolutionarily distant merA genes (as exists between gram-positive and -negative bacteria), detected merA sequences in the genomes of all tested strains. Inducible Hg2+ volatilization was demonstrated for all eight organisms, and NADPH-dependent mercuric reductase activities were detected in crude cell extracts of six of the strains. Because these strains represented random selections of bacteria from three aquatic environments, it is concluded that merA encodes a common molecular mechanism for Hg2+ resistance and volatilization in aerobic heterotrophic aquatic communities.
Growth of Agrobacterium tumefaciens under octopine limitation in chemostats
Authors: Bell C R
Published: January 2020

Agrobacterium tumefaciens B6 and ATCC 15955 were grown under octopine or glutamate limitation in chemostats. Examination of the maximum specific growth rate (mu max) and substrate affinity (KS) for each strain indicated that strain B6 was highly inefficient in its use of octopine as either a nitrogen or carbon source compared with strain ATCC 15955. Examination of the yield coefficients showed that in both strains octopine was used more efficiently as a nitrogen source than as a carbon source. The data permitted predictions to be made concerning the outcome of competition for a single limiting substrate. Under octopine limitation, strain ATCC 15955 should dominate; under glutamate limitation, strain B6 should dominate. The results of an observed competition with glutamate as the limiting substrate confirmed the latter prediction, although B6 did dominate at a rate faster than was predicted from simple competition theory. B6 displayed higher growth rates and substrate affinities than ATCC 15955 on all concentrations of glutamate. The yield of B6 on octopine was also considerably higher. This latter attribute could provide an ecological advantage to B6 because of the importance of yield in the fate of competitions under multisubstrate regimens. These will be the most prevalent regimens in the area around the tumor (tumorosphere) or the rhizosphere. The increased performance on glutamate could provide an advantage in an opine-free environment when B6 is growing as a saprophyte.
Use of Ti Plasmid DNA Probes for Determining Tumorigenicity of
Agrobacterium
Strains
Authors: Burr Thomas J. , Norelli John L. , Katz Barbara H. , Bishop Andrew L.
Published: January 2020

Probes consisting of T-DNA genes from the Ti plasmid of
Agrobacterium tumefaciens
were used for determining tumorigenicity of strains. Two
32
P-labeled probes hybridized with 28 of 28 tumorigenic strains of the pathogen but not with 20 of 22 nontumorigenic strains. One probe, pTHE17, consists of all but the far left portion of the T-DNA of strain C58. Probe
Sma
I7 consists of
Sma
I fragment 7 of pTiC58, including
onc
genes 1, 4, and 6a and most of 2. Another probe, pAL4044, consisting of the
vir
region of strain Ach-5, hybridized with several nontumorigenic as well as tumorigenic strains. Colony hybridizations were done with 28 tumorigenic and 22 nontumorigenic
Agrobacterium
strains. About 10
6
CFU of the different tumorigenic strains were detectable with this method. Southern analyses confirmed the presence or absence of Ti plasmids in strains for which tumorigenicity was questioned. Colony hybridization with the T-DNA probes provides a rapid and sensitive means for determining the tumorigenic nature of
Agrobacterium
strains.
Neutral sugar composition and gravimetric yield of plant and bacterial fractions of feces
Authors: Cabotaje L M , López-Guisa J M , Shinnick F L , Marlett J A
Published: January 2020

Separating dietary fiber from other polysaccharides in digesta and feces is necessary to understand its mechanisms of action. A gravimetric method that separates fecal plant and bacterial matter based on size and density was evaluated and modified to determine the plant and bacterial mass of lyophilized whole and blended rat and human feces. Three screen mech combinations (150 and 75 microns, 150 and 35 microns, 35 microns) were used with rat feces. Filtration of a homogenized rat fecal slurry sequentially through 150- and 35-microns-mesh screens versus 150- and 75-microns-mesh screens decreased the gravimetric recovery of bacteria from congruent to 35 to congruent to 25% of fecal dry weight and increased the plant fraction weight. Neutral sugar composition, determined by gas chromatography of alditol acetates, and bacterial counts of the fractions suggested that the decreased yield of bacterial fraction represented removal of plant material and not a loss of bacteria. Rat excreta contained 29.5% (dry weight) total neutral sugar, 88% of which was recovered in the plant material. Human feces containing wheat bran, fractionated with the 150- and 35-microns-mesh screens, was 21% neutral sugar, congruent to 65% of which was in the plant fraction. The plant fractions had more xylose and arabinose and less glucose than the bacterial fractions. Processing samples in a Waring blender had no adverse effect on the rat or human fecal bacterial counts. The use of this gravimetric method in combination with the sugar analysis of the fractions provided a better measure of plant and bacteria than only gravimetric yield.
Effect of Postemergence, Supplemental Inoculation on Nodulation and Symbiotic Performance of Soybean (
Glycine max
(L.) Merrill) at Three Levels of Soil Nitrogen
Authors: Danso S. K. A. , Zapata F. , Awonaike K. O.
Published: January 2020

The influence of a supplementary bradyrhizobial inoculation after an initial seed slurry inoculation with the same strain on nodulation and N
2
fixation in soybeans was examined in the greenhouse. The plants were grown in a Typic Eutrocrepts soil: sand mixture containing 25, 65, or 83 mg of N per kg (i.e., native soil N plus
15
N-labeled ammonium sulfate). Harvests were made at early flowering and physiological maturity. The supplementary inoculations which were made 14 or 21 days after planting (DAP) caused formation of substantially more nodules than the single slurry inoculation did. Autoregulation was therefore not completely successful in preventing subsequent infections. For the slurry-inoculated plants, at both harvests the proportion of N derived from fixation was greatest in the soil containing the least N, and only slight increases in N
2
fixation resulted from a second inoculation. The inhibition of N
2
fixation at the higher N levels was significantly reduced by a second inoculation at 21 DAP; this treatment resulted in at least a doubling of both the percentage and total amount of N
2
fixed by the single slurry inoculation at physiological maturity. The N
2
fixation increases resulting from the supplementary inoculation at 14 DAP were less pronounced and not significant. Greater N
2
fixation was frequently not reflected by increased total N or dry matter yield, suggesting that the major benefit of the increased fixation was a decreased dependence of plants on soil N for growth.
Anaerobic Biodegradation of 2,4,5-Trichlorophenoxyacetic Acid in Samples from a Methanogenic Aquifer: Stimulation by Short-Chain Organic Acids and Alcohols
Authors: Gibson Susan A. , Suflita Joseph M.
Published: January 2020

The herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was dehalogenated in samples from a methanogenic aquifer to form 2,4- and 2,5-dichlorophenoxyacetic acids as the first detected intermediates. Further incubation of the aquifer slurries resulted in the formation of several intermediates including monochlorophenoxyacetic acids, di- and monochlorophenols, as well as phenol. No transformation of the parent substrate or production of intermediates was detected in autoclaved controls. The pattern of intermediate formation suggested that the anaerobic degradation of 2,4,5-T proceeded by a series of sequential dehalogenation steps with side-chain cleavage reactions occurring at some point before ring cleavage. The addition of short-chain organic acids or alcohols stimulated the onset and rate of 2,4,5-T dehalogenation and decreased the amount of parent substrate still detectable as halogenated intermediates at the end of the experiment. Sulfate addition had the opposite effect on dehalogenation regardless of whether supplemental carbon was added to the aquifer slurries. The inhibitory effect of sulfate on dehalogenation could sometimes be relieved with molybdate, although this effect seemed to be related to the supplemental carbon compound that was used.
Fermentation studies of the secretion of Serratia marcescens nuclease by Escherichia coli
Authors: Biedermann K , Fiedler H , Larsen B S , Riise E , Emborg C , Jepsen P K
Published: January 2020

The secretion of a Serratia marcescens nuclease was followed by fermentation with Escherichia coli. A plasmid, p403-SD2, carrying a 1.3-kilobase-pair insert with a 0.4-kilobase-pair region upstream of the nuclease gene caused a growth-phase-regulated expression of nuclease in E. coli in the same way as that seen in S. marcescens. Deletion of the regulatory gene generating plasmid p403-Rsa1 resulted in a constitutive expression of the nuclease. Anaerobiosis stimulated the expression from p403-SD2 in stationary growth phase by a factor of 10 compared with expression stimulated by cultivation in aerobic conditions; no such effect was found for plasmid p403-Rsa1. Different nutritional factors caused the expression level and the amount of extracellular nuclease to vary more when nuclease was expressed from plasmid p403-SD2 than when it was expressed from plasmid p403-Rsa1. A correlation between the regulatory gene and the extracellular secretion of nuclease is proposed.
Differential Rates of Digestion of Bacteria by Freshwater and Marine Phagotrophic Protozoa
Authors: González Juan M. , Iriberri Juan , Egea Luis , Barcina Isabel
Published: January 2020

Differential decreases over time of two bacterial species,
Escherichia coli
and
Enterococcus faecalis
, in a freshwater and a marine ecosystem were observed and explained by a differential rate of digestion of these bacteria by phagotrophic flagellates and ciliates. For this purpose, fluorescence-labeled bacteria (FLB) were used and prepared from the two species cited above. The number of FLB was observed for 5 days in fresh and marine waters in the presence or absence (0.2-μm-pore-size-filtered water) of natural microbiota. These experiments showed a longer persistence of
Enterococcus faecalis
FLB as opposed to
Escherichia coli
FLB in the presence of natural microbiota. Removal of FLB was due to protozoan grazing because no decrease of FLB number was observed in the absence of natural microbiota. In short-term (about 40 min) ingestion experiments, we found similar clearance rates of
Escherichia coli
and
Enterococcus faecalis
FLB by assemblages of flagellates from the freshwater and the marine ecosystem and by cultured assemblages of ciliates from the marine ecosystem. Clearance rates of
Enterococcus faecalis
FLB were greater than those of
Escherichia coli
FLB for assemblages of ciliates from the freshwater ecosystem. Comparison of rates of ingestion and digestion of FLB by protozoa showed that
Escherichia coli
FLB were digested and ingested at similar rates. However,
Enterococcus faecalis
FLB were digested slower than they were ingested. These results suggest that a longer persistence of
Enterococcus faecalis
as opposed to
Escherichia coli
can be explained by a differential digestion by flagellates and ciliates in aquatic ecosystems. Moreover, rates of ingestion and digestion were strongly correlated for both FLB types.
Nickel accumulation and storage in Bradyrhizobium japonicum
Authors: Maier R J , Pihl T D , Stults L , Sray W
Published: January 2020

Hydrogenase-derepressed (chemolithotrophic growth conditions) and heterotrophically grown cultures of Bradyrhizobium japonicum accumulated nickel about equally over a 3-h period. Both types of cultures accumulated nickel primarily in a form that was not exchangeable with NiCl2, and they accumulated much more Ni than would be needed for the Ni-containing hydrogenase. The nickel accumulated by heterotrophically incubated cultures could later be mobilized to allow active hydrogenase synthesis during derepression in the absence of nickel, while cells both grown and derepressed without nickel had low hydrogenase activities. The level of activity in cells grown with Ni and then derepressed without nickel was about the same as that in cultures derepressed in the presence of nickel. The Ni accumulated by heterotrophically grown cultures was associated principally with soluble proteins rather than particulate material, and this Ni was not lost upon dialyzing an extract containing the soluble proteins against either Ni-containing or EDTA-containing buffer. However, this Ni was lost upon pronase or low pH treatments. The soluble Ni-binding proteins were partially purified by gel filtration and DEAE chromatography. They were not antigenically related to hydrogenase peptides. Much of the 63Ni eluted as a single peak of 48 kilodaltons. Experiments involving immunoprecipitation of 63Ni-containing hydrogenase suggested that the stored source of Ni in heterotrophic cultures that could later be mobilized into hydrogenase resided in the nonexchangeable Ni-containing fraction rather than in loosely bound or ionic forms.
Mannanase Components from
Bacillus pumilus
Authors: Araujo Alberto , Ward Owen P.
Published: January 2020

β-
d
-Mannanase from
Bacillus pumilus
was purified into two components, A and B, which exhibited homogeneity on polyacrylamide gel electrophoresis. These components had molecular weights of 55,000 (A) and 37,000 (B); carbohydrate contents of 15.3% (A) and 7.2% (B); specific activities of 78 (A) and 1,616 (B) U/mg; pH optima of 5.5 to 6.9 (A) and 6.0 (B); and half-lives of 60 (A) and 21 (B) min at 70°C.