bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced control of Listeria monocytogenes by in situ-produced pediocin during dry fermented sausage production
Authors: Foegeding P M , Thomas A B , Pilkington D H , Klaenhammer T R
Published: January 2020

To determine whether pediocin is produced and has effective antilisterial activity during food fermentation, six sausage fermentation trials were conducted with antibiotic-resistant, pediocin-producing (Bac+) Pediococcus acidilactici PAC 1.0 (Strr Rifr) and an isogenic pediocin-negative (Bac-) derivative used as a control. Meat was inoculated (ca. 10(5) CFU/g) with a composite of five Listeria monocytogenes strains, each electrotransformed with pGK12 (Cmr Emr). P. acidilactici and L. monocytogenes populations were selectively enumerated by plating on media with antibiotics. This study indicated that the dry sausage fermentation process can reduce L. monocytogenes populations. Effective inactivation of L. monocytogenes was observed when the pH at the end of the fermentation portion of the process was less than 4.9. Pediocin was responsible for part of the antilisterial activity during the fermentation in each of the six trials. Furthermore, inhibition of L. monocytogenes during drying was enhanced in the presence of pediocin in the three trials in which L. monocytogenes could be detected throughout the drying process. Thus, pediocin production contributed to an increase in safety during both the fermentation and drying portions of sausage manufacturing.
Conversion of Pyruvate to Acetoin Helps To Maintain pH Homeostasis in
Lactobacillus plantarum
Authors: Tsau Jya-Li , Guffanti Arthur A. , Montville Thomas J.
Published: January 2020

Pyruvate is the substrate for diacetyl and acetoin synthesis by lactobacilli. Exogenous pyruvate stimulates acetoin production when glucose is present as an energy source. In
Lactobacillus plantarum
ATCC 8014, the energy derived from glucose via glycolysis generated a constant proton motive force of about -120 mV. At a low external pH, energized cells rapidly transported and accumulated pyruvate but did not do so when they were deenergized by nigericin. When large amounts of pyruvate were transported and subsequently accumulated internally, the cotransported protons rapidly lowered the internal pH. The conversion of pyruvate to acetoin instead of acidic end products contributed to the maintenance of pH homeostasis. This is the first report showing that the conversion of pyruvate to acetoin serves as a mechanism of pH homeostasis.
Survival of toxigenic Pasteurella multocida in aerosols and aqueous liquids
Authors: Thomson C M , Chanter N , Wathes C M
Published: January 2020

The survival of toxigenic Pasteurella multocida in air and liquids was studied to identify possible risk factors in the etiology of atrophic rhinitis. In aerosols, at low relative humidity (28%), the viability of toxigenic P. multocida 5 min after aerosolization was at least 22% of its initial value. Viability at low relative humidity declined to 8% after 45 min. Viability at high relative humidity (79%) was 69% after 5 min and declined to 2% after 45 min. Survival of toxigenic P. multocida in liquids depended on storage and constituents in the liquid. Toxigenic P. multocida became nonculturable 1 to 14 days after inoculation in water and artificial seawater, depending on the storage temperature. Toxigenic P. multocida stored at 37 degrees C could be detected for up to 6 days in pig slurry and more than 36 days in Bacto Tryptose broth and nasal lavages. However, in Bacto Tryptose broth and nasal lavages stored at 4 degrees C, P. multocida was detected for up to 14 days whereas at 15 and 37 degrees C it was detected for more than 49 days. These results suggest that aerosols and fomites can play a role in the transmission of atrophic rhinitis.
Detection of the Light Organ Symbiont,
Vibrio fischeri
, in Hawaiian Seawater by Using
lux
Gene Probes
Authors: Lee Kyu-Ho , Ruby Edward G.
Published: January 2020

Symbiotic bacteria that inhabit the light-emitting organ of the Hawaiian squid
Euprymna scolopes
are distinctive from typical
Vibrio fischeri
organisms in that they are not visibly luminous when grown in laboratory culture. Therefore, the abundance of these bacteria in seawater samples cannot be estimated simply by identifying them among luminous colonies that arise on nutrient agar plates. Instead, we have used
luxR
and polymerase chain reaction generated
luxA
gene probes to identify both luminous and non-visibly luminous
V. fischeri
colonies by DNA-DNA hybridization. The probes were specific, hybridizing at least 50 to 100 times more strongly to immobilized DNAs from
V. fischeri
strains than to those of pure cultures of other related species. Thus, even non-visibly luminous
V. fischeri
colonies could be identified among colonies obtained from natural seawater samples by their probe-positive reaction. Bacteria in seawater samples, obtained either within or distant from squid habitats, were collected on membrane filters and incubated until colonies appeared. The filters were then observed for visibly luminous
V. fischeri
colonies and hybridized with the
lux
gene probes to determine the number of total
V. fischeri
colonies (both luminous and non-visibly luminous). We detected no significant differences in the abundance of luminous
V. fischeri
CFU in any of the water samples observed (≤1 to 3 CFU/100 ml). However, probe-positive colonies of
V. fischeri
(up to 900 CFU/100 ml) were found only in seawater collected from within the natural habitats of the squids. A number of criteria were used to confirm that these probe-positive strains were indistinguishable from symbiotic
V. fischeri.
Therefore, the
luxA
and
luxR
gene probes were species specific and gave a reliable estimate of the number of culturable
V. fischeri
colonies in natural water samples.
Conversion of xylan to ethanol by ethanologenic strains of Escherichia coli and Klebsiella oxytoca
Authors: Burchhardt G , Ingram L O
Published: January 2020

A two-stage process was evaluated for the fermentation of polymeric feedstocks to ethanol by a single, genetically engineered microorganism. The truncated xylanase gene (xynZ) from the thermophilic bacterium Clostridium thermocellum was fused with the N terminus of lacZ to eliminate secretory signals. This hybrid gene was expressed at high levels in ethanologenic strains of Escherichia coli KO11 and Klebsiella oxytoca M5A1(pLOI555). Large amounts of xylanase (25 to 93 mU/mg of cell protein) accumulated as intracellular products during ethanol production. Cells containing xylanase were harvested at the end of fermentation and added to a xylan solution at 60 degrees C, thereby releasing xylanase for saccharification. After cooling, the hydrolysate was fermented to ethanol with the same organism (30 degrees C), thereby replenishing the supply of xylanase for a subsequent saccharification. Recombinant E. coli metabolized only xylose, while recombinant K. oxytoca M5A1 metabolized xylose, xylobiose, and xylotriose but not xylotetrose. Derivatives of this latter organism produced large amounts of intracellular xylosidase, and the organism is presumed to transport both xylobiose and xylotriose for intracellular hydrolysis. By using recombinant M5A1, approximately 34% of the maximal theoretical yield of ethanol was obtained from xylan by this two-stage process. The yield appeared to be limited by the digestibility of commercial xylan rather than by a lack of sufficient xylanase or by ethanol toxicity. In general form, this two-stage process, which uses a single, genetically engineered microorganism, should be applicable for the production of useful chemicals from a wide range of biomass polymers.
Influence of Polyethylene Glycol on the Size of
Schizosaccharomyces pombe
Electropores
Authors: Hood Mark T. , Stachow Chester
Published: January 2020

The role of polyethylene glycol (PEG) in the transformation of
Schizosaccharomyces pombe
by electroporation is investigated by fluorescein isothiocyanate-dextran uptake and transformation studies. It is shown that when
S. pombe
cells are electroporated in the presence of PEG, the permeability state created is sustained until removal of PEG. In addition, the permeability of electroporated
S. pombe
envelopes is further increased with longer incubation times in PEG. The increased permeability is apparently a result of enlarged pores (electropores) due to the presence of PEG. Comparison of a heat pulse transformation protocol with electroporation suggests a second role for PEG in the uptake of macromolecules. Since pores are not thought to be created during a heat pulse, the PEG may be facilitating the uptake of plasmid DNA. This facilitation of uptake would also be expected to affect DNA uptake by electroporated cells.
Efficacy of burning, tillage, and biocides in controlling bacteria released at field sites and effects on indigenous bacteria and fungi
Authors: Donegan K , Fieland V , Fowles N , Ganio L , Seidler R
Published: January 2020

Decontamination treatments of burning and biocide application, alone and in combination with tillage, were evaluated for their ability to reduce populations of bacteria applied to the leaves of plants in field plots. In addition, the effects of these control methods on indigenous leaf and soil bacteria and fungi were assessed. Field plots of bush beans (Phaseolus vulgaris), sprayed with the bacterium Pseudomonas syringae, Pseudomonas fluorescens, or Erwinia herbicola, received the following treatments: (i) control, (ii) tillage, (iii) burning, (iv) burning plus tillage (burn-tillage), (v) Kocide (cupric hydroxide), (vi) Kocide plus tillage, (vii) Agri-Strep (streptomycin sulfate), and (viii) Agri-Strep plus tillage. Leaves and soil from the plots were sampled at 1 day before and at 1, 3, 7, 10, 14, 21, and 30 days after application of the decontamination treatments. The burn and burn-tillage treatments produced the most significant reductions in bacterial populations. The Agri-Strep treatment was more effective than the Kocide treatment in eliminating applied bacteria, but neither biocide produced consistent or persistent control. In contrast, the tillage treatment, alone or in combination with the Agri-Strep or Kocide treatments, had a short-term stimulatory effect and increased populations of applied bacteria and also levels of indigenous fungi and bacteria. Agri-Strep and Kocide treatments caused significant reductions in indigenous bacterial populations up to 14 days after application and in indigenous fungal populations on day 7 after application. Our results suggest that conventional plant disease control methods may not provide satisfactory control of genetically engineered microorganisms and indicate a need for further development of effective and selective methods to control release microorganisms at field sites.
Efficacies of Novel
N
-Halamine Disinfectants against
Salmonella
and
Pseudomonas
Species
Authors: Lauten S. D. , Sarvis H. , Wheatley W. B. , Williams D. E. , Mora E. C. , Worley S. D.
Published: January 2020

Six novel
N
-halamine compounds of potential importance as disinfectants to the food-processing industry were tested against
Salmonella enteritidis, Salmonella gallinarum, Salmonella typhimurium
, and
Pseudomonas fluorescens
in aqueous solution. Inactivation times for 10
6
-fold reductions were determined as a function of water quality at pH 6.5 and 25°C. Phenol coefficients for the efficacies of the compounds against
S. enteritidis
have been reported also. When both stability and efficacy data are considered, as well as cost of production, two compounds, 1,3-dichloro-2,2,5,5-tetramethylimidazolidin-4-one and 1-chloro-2,2,5,5-tetramethylimidazolidin-4-one, offer the greatest potential as biocides for the food-processing industry.
Immunomagnetically Captured Thermophilic Sulfate-Reducing Bacteria from North Sea Oil Field Waters
Authors: Christensen Bjørn , Torsvik Terje , Lien Torleiv
Published: January 2020

Immunomagnetic beads (IMB) were used to recover thermophilic sulfate-reducing bacteria from oil field waters from oil production platforms in the Norwegian sector of the North Sea. IMB coated with polyclonal antibodies against whole-cell antigens of the thermophilic
Thermodesulfobacterium mobile
captured strains GFA1, GFA2, and GFA3. GFA1 was serologically and morphologically identical to
T. mobile.
GFA2 and GFA3 were spore forming and similar to the
Desulfotomaculum
strains T90A and T93B previously isolated from North Sea oil field waters by a classical enrichment procedure. Western blots (immunoblots) of whole cells showed that GFA2, GFA3, T90A, and T93B are different serotypes of the same
Desulfotomaculum
species. Monoclonal antibodies (MAb) against
T. mobile
type strain cells were produced and used as capture agents on IMB. These MAb, named A4F4, were immunoglobulin M; they were specific to
T. mobile
and directed against lipopolysaccharides. The prevailing cells immunocaptured with MAb A4F4 were morphologically and serologically similar to
T. mobile
type strain cells.
T. mobile
was not detected in these oil field waters by classical enrichment procedures. Furthermore, extraction with antibody-coated IMB allowed pure strains to be isolated directly from primary enrichment cultures without prior time-consuming subculturing and consecutive transfers to selective media.
Evaluation of aquatic sediment microcosms and their use in assessing possible effects of introduced microorganisms on ecosystem parameters
Authors: Wagner-Döbler I , Pipke R , Timmis K N , Dwyer D F
Published: January 2020

In this paper we describe a sediment microcosm system consisting of 20 undisturbed, layered sediment cores with overlying site water which are incubated under identical conditions of temperature, light, stirring rate of overlying water, and water exchange rate. Ecosystem parameters (nutrient level, photosynthetic potential, community structure of heterotrophic bacteria, thymidine incorporation rate, and oxygen microgradients) of the laboratory microcosms and the source ecosystem were compared and shown to be indistinguishable for the first 2 weeks. In weeks 3 and 4, small differences were detectable in the nutrient level, community structure of heterotrophic bacteria, and thymidine incorporation rate. However, the photosynthetic potential, depth profiles of heterotrophic bacterial community structure, and oxygen microgradients were maintained throughout the incubation period and did not differ between laboratory microcosms and the source ecosystem. The microcosm system described here would thus appear to be a valid model of aquatic sediments for up to 4 weeks; the actual period would depend on the sediment source and incubation temperature. The validated systems were used with Rhine river sediment to assess possible effects on ecosystem parameters of Pseudomonas sp. strain B13 FR1(pFRC20P), a genetically engineered microorganism (GEM) that had been constructed to degrade mixtures of halo- and alkylbenzoates and -phenols. The GEM survived in the surface sediment at densities of 5 x 10(4) to 5 x 10(5)/g (dry weight) for 4 weeks and degraded added chloro- and methylaromatics. The GEM did not measurably influence ecosystem parameters such as photosynthesis, densities of selected heterotrophic bacteria, thymidine incorporation rate, and oxygen microgradients. Thus, the microcosm system described here would seem to be useful for the study of the ecology of biodegradation and the fate and effect of microorganisms introduced into the environment.
Changes in Molecular Size Distribution of Cellulose during Attack by White Rot and Brown Rot Fungi
Authors: Kleman-Leyer Karen , Agosin Eduardo , Conner Anthony H. , Kirk T. Kent
Published: January 2020

The kinetics of cotton cellulose depolymerization by the brown rot fungus
Postia placenta
and the white rot fungus
Phanerochaete chrysosporium
were investigated with solid-state cultures. The degree of polymerization (DP; the average number of glucosyl residues per cellulose molecule) of cellulose removed from soil-block cultures during degradation by
P. placenta
was first determined viscosimetrically. Changes in molecular size distribution of cellulose attacked by either fungus were then determined by size exclusion chromatography as the tricarbanilate derivative. The first study with
P. placenta
revealed two phases of depolymerization: a rapid decrease to a DP of approximately 800 and then a slower decrease to a DP of approximately 250. Almost all depolymerization occurred before weight loss. Determination of the molecular size distribution of cellulose during attack by the brown rot fungus revealed single major peaks centered over progressively lower DPs. Cellulose attacked by
P. chrysosporium
was continuously consumed and showed a different pattern of change in molecular size distribution than cellulose attacked by
P. placenta.
At first, a broad peak which shifted at a slightly lower average DP appeared, but as attack progressed the peak narrowed and the average DP increased slightly. From these results, it is apparent that the mechanism of cellulose degradation differs fundamentally between brown and white rot fungi, as represented by the species studied here. We conclude that the brown rot fungus cleaved completely through the amorphous regions of the cellulose microfibrils, whereas the white rot fungus attacked the surfaces of the microfibrils, resulting in a progressive erosion.
Evidence for natural transfer of a tetracycline resistance gene between bacteria from the human colon and bacteria from the bovine rumen
Authors: Shoemaker N B , Wang G R , Salyers A A
Published: January 2020

Previously, we demonstrated conjugal transfer of a specially constructed shuttle vector, pRDB5, from the human colonic anaerobe Bacteroides uniformis to the ruminal anaerobe Prevotella (Bacteroides) ruminicola B(1)4. We have now shown that naturally occurring gene transfer elements in Bacteroides species and Prevotella ruminicola can also be transferred between these two genera. A self-transmissible chromosomal element originally found in a clinical isolate of Bacteroides fragilis (Tcr Emr 12256) was transferred from B. uniformis 0061 to P. ruminicola B(1)4 and from P. ruminicola B(1)4 back to B. uniformis or to another human colonic species, Bacteroides thetaiotaomicron. Similarly, a conjugative plasmid (pRRI4) originally found in P. ruminicola 223 was transferred from P. ruminicola B(1)4 to B. uniformis or B. thetaiotaomicron. pRRI4 could be transferred from the colonic Bacteroides species only if the donor strain contained the Tcr Emr 12256 element in its chromosome. These results show that transfer of naturally occurring elements can be demonstrated under laboratory conditions. Evidence that such transfers may actually have occurred in nature came from our finding that the tetracycline resistance (Tcr) gene on the P. ruminicola plasmid pRRI4 hybridized on high-stringency Southern blots with the Tcr gene found on the Bacteroides Tcr elements. The presence of the same gene in such distantly related genera of bacteria is most likely to have occurred as a result of horizontal transfer.
Distribution, Frequency, and Diversity of
Bacillus thuringiensis
in an Animal Feed Mill
Authors: Meadows Martin P. , Ellis Deborah J. , Butt Joe , Jarrett Paul , Burges H. Denis
Published: January 2020

Bacillus thuringiensis
was isolated from 36 of 50 residue samples obtained from an animal feed mill (a stored-product environment). Of 710 selected colonies having
Bacillus cereus-B. thuringiensis
morphology isolated from the samples, 477 were classified as
B. thuringiensis
because of production of parasporal δ-endotoxin crystals. There was a diverse population of
B. thuringiensis
, as revealed by differentiation of the isolates into 36 subgroups by using (i) their spectra of toxicity to the lepidopterans
Heliothis virescens, Pieris brassicae
, and
Spodoptera littoralis
and the dipteran
Aedes aegypti
and (ii) their parasporal crystal morphology. A total of 55% of the isolates were not toxic to any of these insects at the concentrations used in the bioassays; 40% of all isolates were toxic to one or more of the Lepidoptera; and 20, 1, and 1% of the isolates were toxic to only
P. brassicae, H. virescens
, and
S. littoralis
, respectively. The most frequent toxicity was toxicity to
P. brassicae
(36% of all isolates); 18% of the isolates were toxic to
A. aegypti
(5% exclusively), 10% were toxic to
H. virescens
, and 4% were toxic to
S. littoralis
. Toxicity to
P. brassicae
was more often linked with toxicity to
H. virescens
than with toxicity to
S. littoralis
. The frequency of toxicity was significantly greater in isolates that produced bipyramidal crystals than in isolates that produced irregular pointed, irregular spherical, rectangular, or spherical crystals.
Metabolism of phenanthrene by the marine cyanobacterium Agmenellum quadruplicatum PR-6
Authors: Narro M L , Cerniglia C E , Van Baalen C , Gibson D T
Published: January 2020

Under photoautotrophic growth conditions, the marine cyanobacterium Agmenellum quadruplicatum PR-6 metabolized phenanthrene to form trans-9,10-dihydroxy-9,10-dihydrophenanthrene (phenanthrene trans-9,10-dihydrodiol) and 1-methoxyphenanthrene as the major ethyl acetate-extractable metabolites. Small amounts of phenanthrols were also formed. The metabolites were purified by high-pressure liquid chromatography and identified from their UV, infrared, mass, and proton magnetic resonance spectral properties. A. quadruplicatum PR-6 formed phenanthrene trans-9,10-dihydrodiol with a 22% enantiomeric excess of the (-)-9S,10S-enantiomer. Incorporation experiments with 18O2 showed that one atom of oxygen from O2 was incorporated into the dihydrodiol. Toxicity studies, using an algal lawn bioassay, indicated that 9-phenanthrol and 9,10-phenanthrenequinone inhibit the growth of A. quadruplicatum PR-6.
Reductive dehalogenation of chlorophenols by Desulfomonile tiedjei DCB-1
Authors: Mohn W W , Kennedy K J
Published: January 2020

Reductive dehalogenation of chlorophenols has been reported in undefined anaerobic cultures but never before in an anaerobic pure culture. We found that the sulfate-reducing bacterium Desulfomonile tiedjei DCB-1 reductively dehalogenates pentachlorophenol (PCP) and other chlorophenols. The maximum rate of PCP dechlorination observed was 54 mu mol of Cl- h-1 g of protein-1. 3-Chlorobenzoate appeared to serve as a required inducer for PCP dehalogenation; however, neither PCP nor 3-chlorophenol induced dehalogenation. Dehalogenation was catalyzed by living cells, and formate served as a required electron donor. D. tiedjei dehalogenated meta-chlorine substituents of chlorophenols (i.e., PCP was degraded to 2,4,6-trichlorophenol). Generally, more highly chlorinated phenol congeners were more readily dechlorinated, and 3-chlorophenol was not dehalogenated. Growing cultures dehalogenated PCP, but greater than 10 microM PCP (approximately 1.7 mmol g of protein-1) reversibly inhibited growth.
Survival and replication of male-specific bacteriophages in molluscan shellfish
Authors: Burkhardt W , Watkins W D , Rippey S R
Published: January 2020

The survival and replication of male-specific bacteriophages in hard-shelled clams (Mercenaria mercenaria) and their homogenates were examined to further assess their potential utility as indicator organisms. Trials were conducted in the presence and absence of a suitable bacterial host, Escherichia coli HS[pFamp]R. Results of this study demonstrated that male-specific bacteriophages were unable to replicate in hard-shelled clams, with or without added host cells. In addition, the densities of these bacteriophages were stable for up to 7 days in shellfish held at ambient seawater temperatures (less than 25 degrees C). Evidence of replication, although not observed in live shellfish, was found to occur in temperature-abused shellfish homogenates and supernatants, but only when a suitable bacterial host was present.
Methanogenic Degradation of Poly(3-Hydroxyalkanoates)
Authors: Budwill Karen , Fedorak Phillip M. , Page William J.
Published: January 2020

Poly(3-hydroxybutyrate) and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) were fermented to methane and carbon dioxide within 16 days by an anaerobic sewage sludge consortium. The cultures adapted quickly to metabolize these polymeric compounds, and between 83 and 96% of the substrate carbon was transformed to methane and carbon dioxide.
Bdellovibrios in
Callinectus sapidus
, the Blue Crab
Authors: Kelley Jacqueline I. , Williams Henry N.
Published: January 2020

Bdellovibrios were recovered from the gill tissue of all of 31 crabs sampled and from all samples of epibiota obtained from the ventral shell surface of 15 crabs. The results suggest that the blue crab is a reservoir for bdellovibrios. The association with crabs may be an important factor in the ecology of the bdellovibrios.
Isolation and characterization of an acidophilic, heterotrophic bacterium capable of oxidizing ferrous iron
Authors: Johnson D B , Ghauri M A , Said M F
Published: January 2020

A heterotrophic bacterium, isolated from an acidic stream in a disused pyrite mine which contained copious growths of "acid streamers," displayed characteristics which differentiated it from previously described mesophilic acidophiles. The isolate was obligately acidophilic, with a pH range of 2.0 to 4.4 and an optimum pH of 3.0. The bacterium was unable to fix carbon dioxide but oxidized ferrous iron, although at a slower rate than either Thiobacillus ferrooxidans or Leptospirillum ferrooxidans. Elemental sulfur and manganese(II) were not oxidized. In liquid media, the isolate produced macroscopic streamerlike growths. Microscopic examination revealed that the bacterium formed long (greater than 100 microns) filaments which tended to disintegrate during later growth stages, producing single, motile cells and small filaments. The isolate did not appear to utilize the energy from ferrous iron oxidation. Both iron (ferrous or ferric) and an organic substrate were necessary to promote growth. The isolate displayed a lower tolerance to heavy metals than other iron-oxidizing acidophiles, and growth was inhibited by exposure to light. There was evidence of extracellular sheath production by the isolate. In this and some other respects, the isolate resembles members of the Sphaerotilus-Leptothrix group of filamentous bacteria. The guanine-plus-cytosine content of the isolate was 62 mol%, which is less than that recorded for Sphaerotilus-Leptothrix spp. and greater than those of L. ferrooxidans and most T. ferrooxidans isolates.
Reciprocal Isomerization of Butyrate and Isobutyrate by the Strictly Anaerobic Bacterium Strain WoG13 and Methanogenic Isobutyrate Degradation by a Defined Triculture
Authors: Matthies Carola , Schink Bernhard
Published: January 2020

Isomerization of butyrate and isobutyrate was investigated with the recently isolated strictly anaerobic bacterium strain WoG13 which ferments glutarate to butyrate, isobutyrate, CO
2
, and small amounts of acetate. Dense cell suspensions converted butyrate to isobutyrate and isobutyrate to butyrate.
13
C-nuclear magnetic resonance experiments proved that this isomerization was accomplished by migration of the carboxyl group to the adjacent carbon atom. In cell extracts, both butyrate and isobutyrate were activated to their coenzyme A (CoA) esters by acyl-CoA:acetate CoA-transferases. The reciprocal rearrangement of butyryl-CoA and isobutyryl-CoA was catalyzed by a butyryl-CoA:isobutyryl-CoA mutase which depended strictly on the presence of coenzyme B
12
. Isobutyrate was completely degraded via butyrate to acetate and methane by a defined triculture of strain WoG13,
Syntrophomonas wolfei
, and
Methanospirillum hungatei.
Production of citric and oxalic acids and solubilization of calcium phosphate by Penicillium bilaii
Authors: Cunningham J E , Kuiack C
Published: January 2020

An isolate of Penicillium bilaii previously reported to solubilize mineral phosphates and enhance plant uptake of phosphate was studied. Using agar media with calcium phosphate and the pH indicator alizarin red S, the influence of the medium composition on phosphate solubility and medium acidification was recorded. The major acidic metabolites produced by P. bilaii in a sucrose nitrate liquid medium were found to be oxalic acid and citric acid. Citric acid production was promoted under nitrogen-limited conditions, while oxalic acid production was promoted under carbon-limited conditions. Citric acid was produced in both growth and stationary phases, but oxalic acid production occurred only in stationary phase. When submerged cultures which normally produce acid were induced to sporulate, the culture medium shifted toward alkaline rather than acid reaction with growth.
Effect of inoculant strain and organic matter content on kinetics of 2,4-dichlorophenoxyacetic acid degradation in soil
Authors: Greer L E , Shelton D R
Published: January 2020

We monitored rates of degradation of soluble and sorbed 2,4-dichlorophenoxyacetic acid (2,4-D) in low-organic-matter soil at field capacity amended with 1, 10, or 100 micrograms of 2,4-D per g of wet soil and inoculated with one of two bacterial strains (MI and 155) with similar maximum growth rates (mu max) but significantly different half-saturation growth constants (Ks). Concentrations of soluble 2,4-D were determined by analyzing samples of pore water pressed from soil, and concentrations of sorbed 2,4-D were determined by solvent extraction. Between 65 and 75% of the total 2,4-D was present in the soluble phase at equilibrium, resulting in soil solution concentrations of ca. 8, 60, and 600 micrograms of 2,4-D per ml, respectively. Soluble 2,4-D was metabolized preferentially; this was followed by degradation of both sorbed (after desorption) and soluble 2,4-D. Rates of degradation were comparable for the two strains at soil concentrations of 10 and 100 micrograms of 2,4-D per g; however, at 1 microgram/g of soil, 2,4-D was metabolized more rapidly by the strain with the lower Ks value (strain MI). We also monitored rates of biodegradation of soluble and sorbed 2,4-D in high-organic-matter soil at field capacity amended with 100 micrograms of 2,4-D per g of wet soil and inoculated with the low-Ks strain (strain MI). Ten percent of total 2,4-D was present in the soluble phase, resulting in a soil solution concentration of ca. 30 micrograms of 2,4-D per ml.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of two nisin-producing Lactococcus lactis subsp. lactis strains isolated from a commercial sauerkraut fermentation
Authors: Harris L J , Fleming H P , Klaenhammer T R
Published: January 2020

Two Lactococcus lactis subsp. lactis strains, NCK400 and LJH80, isolated from a commercial sauerkraut fermentation were shown to produce nisin. LJH80 was morphologically unstable and gave rise to two stable, nisin-producing (Nip+) derivatives, NCK318-2 and NCK318-3. NCK400 and derivatives of LJH80 exhibited identical morphological and metabolic characteristics, but could be distinguished on the basis of plasmid profiles and genomic hybridization patterns to a DNA probe specific for the iso-ISS1 element, IS946. NCK318-2 and NCK318-3 harbored two and three plasmids, respectively, which hybridized with IS946. Plasmid DNA was not detected in NCK400, and DNA from this strain failed to hybridize with IS946. Despite the absence of detectable plasmid DNA in NCK400, nisin-negative derivatives (NCK402 and NCK403) were isolated after repeated transfer in broth at 37 degrees C. Nisin-negative derivatives concurrently lost the ability to ferment sucrose and became sensitive to nisin. A 4-kbp HindIII fragment containing the structural gene for nisin (spaN), cloned from L. lactis subsp. lactis ATCC 11454, was used to probe genomic DNA of NCK318-2, NCK318-3, NCK400, and NCK402 digested with EcoRI or HindIII. The spaN probe hybridized to an 8.8-kbp EcoRI fragment and a 10-kbp HindIII fragment in the Nip+ sauerkraut isolates, but did not hybridize to the Nip- derivative, NCK402. A different hybridization pattern was observed when the same probe was used against Nip+ L. lactis subsp. lactis ATCC 11454 and ATCC 7962. These phenotypic and genetic data confirmed that unique Nip+ L. lactis subsp. lactis strains were isolated from fermenting sauerkraut.
Novel paired starter culture system for sauerkraut, consisting of a nisin-resistant Leuconostoc mesenteroides strain and a nisin-producing Lactococcus lactis strain
Authors: Harris L J , Fleming H P , Klaenhammer T R
Published: January 2020

Nisin-resistant Leuconostoc mesenteroides NCK293 and nisin-producing Lactococcus lactis subsp. lactis NCK401 were evaluated separately and in combination for growth and nisin production in a model sauerkraut fermentation. Strains were genetically marked and selectively enumerated by using antibiotic-containing media. The growth and survival of L. mesenteroides were similar in the presence and absence of Lactococcus lactis subsp. lactis. The growth of Lactococcus lactis subsp. lactis was not inhibited, although the maximum cell density was reduced and the population decline was more pronounced in the presence of L. mesenteroides. Nisin was detected within 24 h, and levels were relatively constant over the 12-day test period. The maximum cell populations and nisin level achieved could be altered by changing the initial cell ratios of L. mesenteroides and lactococcus lactis subsp. lactis. Isogenic nisin-producing and nisin-negative Lactococcus lactis subsp. lactis derivatives were used in combination with nisin-resistant L. mesenteroides to demonstrate that nisin levels produced in mixed culture were sufficient to retard the onset of the growth of nisin-sensitive, homofermentative Lactobacillus plantarum ATCC 14917.
Persistence of Vibrio vulnificus in tissues of Gulf Coast oysters, Crassostrea virginica, exposed to seawater disinfected with UV light
Authors: Tamplin M L , Capers G M
Published: January 2020

Vibrio vulnificus is an estuarine bacterium which can cause opportunistic infections in humans consuming raw Gulf Coast oysters, Crassostrea virginica. Although V. vulnificus is known as a ubiquitous organism in the Gulf of Mexico, its ecological relationship with C. virginica has not been adequately defined. The objective of the present study was to test the hypothesis that V. vulnificus is a persistent microbial flora of oysters and unamenable to traditional methods of controlled purification, such as UV light depuration. Experimental depuration systems consisted of aquaria containing temperature-controlled seawater treated with UV light and 0.2-microns-pore-size filtration. V. vulnificus was enumerated in seawater, oyster shell biofilms, homogenates of whole oyster meats, and tissues including the hemolymph, digestive region, gills, mantle, and adductor muscle. Results showed that depuration systems conducted at temperatures greater than 23 degrees C caused V. vulnificus counts to increase in oysters, especially in the hemolymph, adductor muscle, and mantle. Throughout the process, depuration water contained high concentrations of V. vulnificus, indicating that the disinfection properties of UV radiation and 0.2-microns-pore-size filtration were less than the rate at which V. vulnificus was released into seawater. Approximately 10(5) to 10(6) V. vulnificus organisms were released from each oyster per hour, with 0.05 to 35% originating from shell surfaces. These surfaces contained greater than 10(3) V. vulnificus organisms per cm2. In contrast, when depuration seawater was maintained at 15 degrees C, V. vulnificus was not detected in seawater and multiplication in oyster tissues was inhibited.
Enhanced heterologous gene expression in novel rpoH mutants of Escherichia coli
Authors: Obukowicz M G , Staten N R , Krivi G G
Published: January 2020

Extragenic temperature-resistant suppressor mutants of an rpoD800 derivative of Escherichia coli W3110 were selected at 43.5 degrees C. Two of the mutants were shown to have a phenotype of enhanced accumulation of heterologous proteins. Genetic mapping of the two mutants showed that the mutation conferring temperature resistance resided in the rpoH gene. P1-mediated transduction of the rpoD+ gene into both of the rpoD800 rpoH double mutants resulted in viable rpoH mutants, MON102 and MON105, that retained temperature resistance at 46 degrees C, the maximum growth temperature of W3110. The complete rpoH gene, including the regulatory region, from MON102, MON105, and the parental W3110 was cloned and sequenced. Sequencing results showed that a single C----T transition at nucleotide 802 was present in both MON102 and MON105, resulting in an Arg(CGC)----Cys(TGC) substitution at amino acid residue 268 (R-268-C; this gene was designated rpoH358). Heterologous protein accumulation levels in both MON102 and MON105, as well as in rpoH358 mutants constructed in previously unmanipulated W3110 and JM101, were assessed and compared with parental W3110 and JM101 levels. Expression studies utilizing the recA or araBAD promoter and the phage T7 gene 10L ribosome-binding site (g10L) showed that increased accumulation levels of a number of representative heterologous proteins (i.e., human or bovine insulin-like growth factor-1, bovine insulin-like growth factor-2, prohormone of human atrial natriuretic factor, bovine placental lactogen, and/or bovine prolactin) were obtained in the rpoH358 mutants compared with the levels in the parental W3110 and JM101. The mechanism of enhanced heterologous protein accumulation in MON102 and MON105 was unique compared with those of previously described rpoH mutants. Pulse-chase and Northern (RNA) blot analyses showed that the enhanced accumulation of heterologous proteins was not due to decreased proteolysis but was instead due to increased levels of the respective heterologous mRNAs accompanied by increased synthesis of the respective heterologous proteins. The plasmid copy number remained unaltered.
Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals
Authors: Collins Y E , Stotzky G
Published: January 2020

The electrokinetic patterns of four bacterial species (Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae and Candida albicans), and two clay minerals (montmorillonite and kaolinite) in the presence of the chloride salts of the heavy metals, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, and of Na and Mg were determined by microelectrophoresis. The cells and kaolinite were net negatively charged at pH values above their isoelectric points (pI) in the presence of Na, Mg, Hg, and Pb at an ionic strength (mu) of 3 x 10(-4); montmorillonite has no pI and was net negatively charged at all pH values in the presence of these metals. However, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn at pH values above 5.0 (the pH at which charge reversal occurred differed with the metal) and then, at higher pH values, again became negative. The charge of the bacteria and S. cerevisiae also reversed in solutions of Cu and Ni with a mu of greater than 3 x 10(-4), whereas there was no reversal in solutions with a mu of less than 3 x 10(-4). The clays became net positively charged when the mu of Cu was greater than 3 x 10(-4) and that of Ni was greater than 1.5 x 10(-4). The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite) (mu = 3 x 10(-4)). The pIs of the cells in the presence of the heavy metals were at either higher or lower pH values than in the presence of Na and Mg. Exposure of the cells to the various metals at pH values from 2 to 9 for the short times (ca. 10 min) required to measure the electrophoretic mobility did not affect their viability. The specific adsorption on the cells and clays of the hydrolyzed species of some of the heavy metals that formed at higher pH values was probably responsible for the charge reversal. These results suggest that the toxicity of some heavy metals to microorganisms varies with pH because the hydrolyzed speciation forms of these metals, which occur at higher pH values, bind on the cell surface and alter the net charge of the cell.(ABSTRACT TRUNCATED AT 400 WORDS)
Effect of acetylene on nitrous oxide reduction and sulfide oxidation in batch and gradient cultures of Thiobacillus denitrificans
Authors: Dalsgaard T , Bak F
Published: January 2020

Anaerobic enrichment cultures with H2S and N2O as substrates which were inoculated with a biofilm sample showed rapid growth and gas formation after 2 to 3 days at 27 degrees C. By using the deep-agar dilution technique, a pure culture was obtained. The strain was tentatively identified as Thiobacillus denitrificans. The isolate was used for batch and gradient culture studies under denitrifying conditions, oxidizing H2S with concomitant reduction of N2O to N2. In batch culture, oxidation of H2S was stepwise, with transient accumulation of elemental sulfur; the final oxidation product was SO4(2-). In gradient culture, there was no notable accumulation of elemental sulfur and microsensor measurements of H2S and N2O showed that H2S was oxidized directly to SO4(2-). In the presence of C2H2, however, oxidation of H2S stopped at the level of elemental sulfur and no SO4(2-) was produced in either batch or gradient cultures. This is a hitherto unknown inhibitory effect of C2H2. The inhibition is suggested to occur at the level of sulfite reductase, which catalyzes the oxidation of elemental sulfur to SO3(2-) in T. denitrificans. However, reduction of N2O in this strain was, surprisingly, not affected by C2H2. The isolate is the first chemolithoautotrophic organism shown to reduce N2O in the presence of C2H2. Denitrification in natural ecosystems is often quantified as N2O accumulation after C2H2 addition. However, the presence of large numbers of similar organisms with C2H2-insensitive N2O reduction could lead to underestimation of in situ rates.
Long-term starvation survival of Yersinia ruckeri at different salinities studied by microscopical and flow cytometric methods
Authors: Thorsen B K , Enger O , Norland S , Hoff K A
Published: January 2020

Cultures of three strains of the fish pathogenic bacterium Yersinia ruckeri survived starvation in unsupplemented water for at least 4 months. At salinities of 0 to 20/1000 there were no detectable changes in CFU during the first 3 days of starvation and only a small decrease during the following 4 months, whereas at 35/1000 salinity, the survival potential of the cultures was markedly reduced. These results suggest that Y. ruckeri may survive for long periods in freshwater and brackish environments after an outbreak of enteric redmouth disease. Survival was also examined by use of the direct viable count method, and we show that this method can be combined with flow cytometry for automatic counting of viable bacteria. By flow cytometry, it was shown that genome replication initiated before the onset of starvation was completed, during the initial phase of starvation, and that starved cells could contain up to six genomes per cell.
Enrichment and properties of an anaerobic mixed culture reductively dechlorinating 1,2,3-trichlorobenzene to 1,3-dichlorobenzene
Authors: Holliger C , Schraa G , Stams A J , Zehnder A J
Published: January 2020

Hexachlorobenzene (HCB), pentachlorobenzene (QCB), all three isomers of tetrachlorobenzene (TeCB), 1,2,3-trichlorobenzene (1,2,3-TCB), and 1,2,4-TCB were reductively dechlorinated by enrichment cultures in the presence of lactate, glucose, ethanol, or isopropanol as the electron donor. The enrichment cultures originated from percolation columns filled with Rhine River sediment in which dechlorination of TCBs and dichlorobenzenes (DCBs) occurred. A stable consortium obtained by transfer on lactate as the energy and carbon source in the presence of 1,2,3-TCB dechlorinated this isomer stoichiometrically to 1,3-DCB. Dechlorinating activity could only be maintained when an electron donor was added. Lactate, ethanol, and hydrogen appeared to be the best substrates. Optimal temperature and pH for dechlorination were 30 degrees C and 7.2, respectively. The specificity of the enrichment on lactate and 1,2,3-TCB was tested after approximately 60 transfers (after 2.5 years). HCB and QCB were stoichiometrically dechlorinated to 1,3,5-TCB and minor amounts of 1,2,4-TCB. 1,3,5-TCB was the sole product formed from 1,2,3,5-TeCB, while 1,2,3,4-TeCB and 1,2,4,5-TeCB were converted to 1,2,4-TCB. 1,2,4-TCB, 1,3,5-TCB, and the three isomers of DCB were not dechlorinated during 4 weeks of incubation. For further enrichment of the 1,2,3-TCB-dechlorinating bacteria, a two-liquid-phase (hexadecane-water) system was used with hydrogen as the electron donor and 1,2,3-TCB or CO2 as the electron acceptor. Methanogens and acetogens were the major substrate-competing (H2-CO2) microorganisms in the two-liquid-phase system. Inhibition of methanogenesis by 2-bromoethanesulfonic acid did not influence dechlorination, and acetogens which were isolated from the enrichment culture did not have dechlorinating activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Characteristics of a new cellulolytic Clostridium sp. isolated from pig intestinal tract
Authors: Varel V H , Pond W G
Published: January 2020

Gram-positive, spore-forming, motile, cellulolytic rods were isolated from 10(7) dilutions of pig fecal samples. The pigs had previously been fed pure cultures of the ruminal cellulolytic organism Clostridium longisporum. Isolates formed terminal to subterminal spores, and a fermentable carbohydrate was required for growth. Besides cellulose, the isolates utilized cellobiose, glycogen, maltose, and starch. However, glucose, fructose, sucrose, pectin, and xylose were not used as energy sources. Major fermentation products included formate and butyrate. The isolates did not digest proteins from gelatin or milk. Unlike C. longisporum, which has limited ability to degrade cell wall components from grasses (switchgrass, bromegrass, and ryegrass), the swine isolates were equally effective in degrading these components from both alfalfa and grasses. The extent of degradation was equal to or better than that observed with the predominant ruminal cellulolytic organisms. On the basis of morphology, motility, spore formation, fermentation products, and the ability to hydrolyze cellulose, the isolates are considered to be a new species of the genus Clostridium. It is unclear whether C. longisporum played a role in the establishment or occurrence of this newly described cellulolytic species. This is the first report of a cellulolytic Clostridium sp. isolated from the pig intestinal tract.
Effect of Growth Temperature on Fatty Acid Composition of Ten
Thermus
Strains
Authors: Nordström Katrina M. , Laakso Simo V.
Published: January 2020

The fatty acid composition of
Thermus
spp., including
T. aquaticus
ATCC 25104,
T. thermophilus
DSM 579,
T. flavus
DSM 674, and seven wild strains was examined. Organisms were tested at a minimum of either 35, 40, or 45°C and at an optimum of 60 or 70°C. Total fatty acid content per dry weight of cells varied between 1.2 and 3.7%, and the quantity of fatty acids was higher at the high temperature range in the majority of strains. At the optimum temperature, strains could be assigned to three chemotaxonomic groups with reference to the ratio of iso C
15:0
/iso C
17:0
. In six of the strains the ratio of iso C
15:0
/iso C
17:0
remained unchanged at the minimum temperature, whereas in four strains the ratio was reversed. The proportion of the C
15:0
and C
17:0
isobranched acids was decreased and the proportion of anteisobranched fatty acids, namely anteiso C
15:0
, anteiso C
17:0
, and anteiso C
17:1
, was increased at the lower temperature range. Some changes were seen in the levels of the n-C
16:0
and iso C
16:0
acids, but these were strain specific.