bluuebunny/crossref_metadata_2025 huggingface dataset:
Geobacter sulfurreducens sp. nov., a hydrogen- and acetate-oxidizing dissimilatory metal-reducing microorganism
Authors: Caccavo F , Lonergan D J , Lovley D R , Davis M , Stolz J F , McInerney M J
Published: January 2020

A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Okla. The isolate, which was designated strain PCA, was an obligately anaerobic, nonfermentative nonmotile, gram-negative rod. PCA grew in a defined medium with acetate as an electron donor and ferric PPi, ferric oxyhydroxide, ferric citrate, elemental sulfur, Co(III)-EDTA, fumarate, or malate as the sole electron acceptor. PCA also coupled the oxidation of hydrogen to the reduction of Fe(III) but did not reduce Fe(III) with sulfur, glucose, lactate, fumarate, propionate, butyrate, isobutyrate, isovalerate, succinate, yeast extract, phenol, benzoate, ethanol, propanol, or butanol as an electron donor. PCA did not reduce oxygen, Mn(IV), U(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PCA exhibited dithionite-reduced minus air-oxidized difference spectra which were characteristic of c-type cytochromes. Phylogenetic analysis of the 16S rRNA sequence placed PCA in the delta subgroup of the proteobacteria. Its closest known relative is Geobacter metallireducens. The ability to utilize either hydrogen or acetate as the sole electron donor for Fe(III) reduction makes strain PCA a unique addition to the relatively small group of respiratory metal-reducing microorganisms available in pure culture. A new species name, Geobacter sulfurreducens, is proposed.
Ribotyping of
Erwinia chrysanthemi
Strains in Relation to Their Pathogenic and Geographic Distribution
Authors: Nassar Atef , Bertheau Yves , Dervin Catherine , Narcy Jean-Paul , Lemattre Monique
Published: January 2020

16S and 23S rRNAs from
Escherichia coli
were used to study the relationship among a representative collection of strains of
Erwinia chrysanthemi
differing in their original host and geographical origin. Phenetic analysis of restriction fragment length polymorphisms allowed the distribution of the studied strains into seven clusters. These clusters were similar to those obtained by cladistic methods and appeared to correlate well with the established pathovars and biovars but to a lesser extent with geographical distribution. Except for two groups of strains defined as tropical and temperate isolates (clusters 3 and 4, respectively), our clustering correlated well with botanical classifications of host plants. However, the rRNA groupings were shown to be more discriminative than biovar analysis. To assess the relationship between rRNA clusters and pathogenicity, 12 representative strains from different clusters were tested for pathogenicity on different plants. The two typical symptoms, maceration and wilting, were observed for these strains. The occurrence of the tobacco hypersensitivity reaction for a subset of these strains is discussed in light of recent results concerning the presence of an
hrp
gene. Considering symptom expression only, rather than the capacity for plant infection, strains from the same cluster were shown to induce similar symptoms in test plants. Thus, since host specificity is still quite controversial, rRNA patterns may constitute a useful tool in taxonomic and epidemiological studies of
Erwinia chrysanthemi
species.
Construction of a Novel Polychlorinated Biphenyl-Degrading Bacterium: Utilization of 3,4′-Dichlorobiphenyl by
Pseudomonas acidovorans
M3GY
Authors: McCullar M. V. , Brenner Vladimir , Adams Randy H. , Focht D. D.
Published: January 2020

Pseudomonas acidovorans
M3GY is a recombinant bacterium with the novel capacity to utilize a biphenyl congener chlorinated on both rings, 3,4′-dichlorobiphenyl (3,4′-DCBP), as a sole carbon and energy source. Strain M3GY was constructed with a continuous amalgamated culture apparatus (L. Kröckel and D. D. Focht, Appl. Environ. Microbiol. 53:2470-2475, 1987) with
P. acidovorans
CC1(19), a chloroacetate and biphenyl degrader, and
Pseudomonas
sp. strain CB15(1), a biphenyl and 3-chlorobenzoate degrader. Genetic and phenotypic data showed the recipient parental strain to be
P. acidovorans
CC1 and the donor parental strain to be
Pseudomonas
sp. strain CB15. In growth experiments with 3,4′-DCBP as a sole source of carbon, cultures of strain M3GY increased in absorbance from 0.07 to 0.39 in 29 days while reaching a protein concentration of 58 μg ml
-1
and 67% substrate dehalogenation. 4-Chlorobenzoate was identified from culture supernatants of strain M3GY by gas chromatography-infrared spectrometry-mass spectrometry; this would be consistent with the oxidation of the
m
-chlorinated ring through the standard biphenyl pathway. 4-Chlorobenzoate was converted to 4-chlorocatechol, which was metabolized through the
meta
-fission pathway. The construction of
P. acidovorans
M3GY, with the novel capability to utilize 3,4′-DCBP, thus involves the complete use of
meta
-fission pathways for sequential rupture of the biphenyl and chlorobenzoate rings.
Comparison of Disulfide Contents and Solubility at Alkaline pH of Insecticidal and Noninsecticidal
Bacillus thuringiensis
Protein Crystals
Authors: Du Cheng , Martin Phyllis A. W. , Nickerson Kenneth W.
Published: January 2020

We compared two insecticidal and eight noninsecticidal soil isolates of
Bacillus thuringiensis
with regard to the solubility of their proteinaceous crystals at alkaline pH values. The protein disulfide contents of the insecticidal and noninsecticidal crystals were equivalent. However, six of the noninsecticidal crystals were soluble only at pH values of ≥12. This lack of solubility contributed to their lack of toxicity. One crystal type which was soluble only at pH ≥12 (strain SHP 1-12) did exhibit significant toxicity to tobacco hornworm larvae when the crystals were presolubilized. In contrast, freshly prepared crystals from the highly insecticidal strain HD-1 were solubilized at pH 9.5 to 10.5, but when these crystals were denatured, by either 8 M urea or autoclave temperatures, they became nontoxic and were soluble only at pH values of ≥12. These changes in toxicity and solubility occurred even though the denatured HD-1 crystals were morphologically indistinguishable from native crystals. Our data are consistent with the view that insecticidal crystals contain distorted, destabilized disulfide bonds which allow them to be solubilized at pH values (9.5 to 10.5) characteristic of lepidopteran and dipteran larval midguts.
Characterization of a Protease from a Psychrotroph,
Pseudomonas fluorescens
114
Authors: Hamamoto Tetsuo , Kaneda Motohiro , Horikoshi Koki , Kudo Toshiaki
Published: January 2020

A psychrotrophic bacterium isolated from river sediment was identified as
Pseudomonas fluorescens
114. It grew at 0°C and optimally at 20°C. The bacterium produced a protease with a molecular weight of 47,000, which was stable in the pH range of 5 to 9 and worked optimally between pH 6.5 and 10. Activity was optimal at 35°C and was lost immediately at 50°C and after 5 min at 45°C. At 0, 10, and 20°C, 24, 38, and 57% of optimal activity were observed, respectively.
Organic-Solvent-Tolerant Bacterium Which Secretes Organic-Solvent-Stable Lipolytic Enzyme
Authors: Ogino Hiroyasu , Miyamoto Kazuhiro , Ishikawa Haruo
Published: January 2020

A bacterial strain which could be grown in a medium containing organic solvents and which could secrete lipolytic enzyme was isolated. The stability of the lipolytic activity of the supernatant of the culture increased significantly in the presence of organic solvents such as toluene, cyclohexane, ethanol, and acetone.
A novel strictly anaerobic recovery and enrichment system incorporating lithium for detection of heat-injured Listeria monocytogenes in pasteurized milk containing background microflora
Authors: Mendonca A F , Knabel S J
Published: January 2020

Heat-injured cells of Listeria monocytogenes were recovered from heated raw milk containing noninjured Enterococcus faecium by combining a simple method for obtaining strict anaerobiosis with a novel enrichment broth, Penn State University broth (PSU broth). Strictly anaerobic conditions were rapidly achieved by adding 0.5 g of filter-sterilized cysteine per liter to PSU broth and then purging the preparation with N2 gas. Little resuscitation or growth occurred in strictly anaerobic PSU broth without lithium chloride because of overgrowth by E. faecium. The growth of E. faecium decreased dramatically with increasing LiCl concentration; LiCl concentrations of 8 and 10 g/liter were completely bacteriostatic. The mechanism of inhibition by LiCl appeared to involve competition with the divalent cations Ca2+ and Mg2+. Heat-injured L. monocytogenes consistently recovered and grew rapidly in strictly anaerobic PSU broth containing 4, 6, or 7 g of LiCl per liter. The use of strictly anaerobic PSU broth containing 7 g of LiCl per liter permitted detection of severely heat-injured L. monocytogenes in one simple recovery-enrichment step by eliminating oxygen toxicity and inhibiting the growth of background microflora, without preventing the resuscitation and subsequent growth of heat-injured L. monocytogenes. L. monocytogenes heated in raw milk at 62.8 degrees C for 10, 15, and 20 min could be consistently recovered from strictly anaerobic PSU broth enrichment cultures at 30 degrees C after 48, 96, and 144 h, respectively, and hence, use of PSU broth may result in better recovery of both injured and noninjured cells from foods than currently used U.S. Department of Agriculture and Food and Drug Administration preenrichment procedures.
Transfer of multiple drug resistance plasmids between bacteria of diverse origins in natural microenvironments
Authors: Kruse H , Sørum H
Published: January 2020

Plasmids harboring multiple antimicrobial-resistance determinants (R plasmids) were transferred in simulated natural microenvironments from various bacterial pathogens of human, animal, or fish origin to susceptible strains isolated from a different ecological niche. R plasmids in a strain of the human pathogen Vibrio cholerae O1 E1 Tor and a bovine Escherichia coli strain were conjugated to a susceptible strain of the fish pathogenic bacterium Aeromonas salmonicida subsp. salmonicida in marine water. Conjugations of R plasmids between a resistant bovine pathogenic E. coli strain and a susceptible E. coli strain of human origin were performed on a hand towel contaminated with milk from a cow with mastitis. A similar conjugation event between a resistant porcine pathogenic E. coli strain of human origin was studied in minced meat on a cutting board. Conjugation of R plasmids between a resistant strain of the fish pathogenic bacterium A. salmonicida subsp. salmonicida and a susceptible E. coli strain of human origin was performed in raw salmon on a cutting board. R plasmids in a strain of A. salmonicida subsp. salmonicida and a human pathogenic E. coli strain were conjugated to a susceptible porcine E. coli strain in porcine feces. Transfer of the different R plasmids was confirmed by plasmid profile analyses and determination of the resistance pattern of the transconjugants. The different R plasmids were transferred equally well under simulated natural conditions and under controlled laboratory conditions, with median conjugation frequencies ranging from 3 x 10(-6) to 8 x 10(-3). The present study demonstrates that conjugation and transfer of R plasmids is a phenomenon that belongs to the environment and can occur between bacterial strains of human, animal, and fish origins that are unrelated either evolutionarily or ecologically even in the absence of antibiotics. Consequently, the contamination of the environment with bacterial pathogens resistant to antimicrobial agents is a real threat not only as a source of disease but also as a source from which R plasmids can easily spread to other pathogens of diverse origins.
Molecular characterization of races and vegetative compatibility groups in Fusarium oxysporum f. sp. vasinfectum
Authors: Fernandez D , Assigbese K , Dubois M P , Geiger J P
Published: January 2020

Restriction fragment length polymorphism (RFLP) and vegetative compatibility analyses were undertaken to assess genetic relationships among 52 isolates of Fusarium oxysporum f. sp. vasinfectum of worldwide origin and representing race A, 3, or 4 on cotton plants. Ten distinct vegetative compatibility groups (VCGs) were obtained, and isolates belonging to distinct races were never in the same VCG. Race A isolates were separated into eight VCGs, whereas isolates of race 3 were classified into a single VCG (0113), as were those of race 4 (0114). Ribosomal and mitochondrial DNA (rDNA and mtDNA) RFLPs separated four rDNA haplotypes and seven mtDNA haplotypes. Race A isolates displayed the most polymorphism, with three rDNA haplotypes and four mtDNA haplotypes; race 4 isolates formed a single rDNA group but exhibited three mtDNA haplotypes, while race 3 isolates had unique rDNA and mtDNA haplotypes. Two mtDNA molecules with distinct sizes were identified; the first (45-kb mtDNA) was found in all race A isolates and seven race 4 isolates, and the second (55-kb mtDNA) was found in all race 3 isolates and in two isolates of race 4. These two mtDNA molecules were closely related to mtDNAs of F. oxysporum isolates belonging to other formae speciales (conglutinans, lycopersici, matthioli, and raphani). Isolates within a VCG shared the same rDNA and mtDNA haplotypes, with the exception of VCG0114, in which three distinct mtDNA haplotypes were observed. Genetic relationships among isolates inferred from rDNA or mtDNA site restriction data were different, and there was not a strict correlation between race and RFLPs.(ABSTRACT TRUNCATED AT 250 WORDS)
merA gene expression in aquatic environments measured by mRNA production and Hg(II) volatilization
Authors: Nazaret S , Jeffrey W H , Saouter E , Von Haven R , Barkay T
Published: January 2020

The relationship of merA gene expression (specifying the enzyme mercuric reductase) to mercury volatilization in aquatic microbial communities was investigated with samples collected at a mercury-contaminated freshwater pond, Reality Lake, in Oak Ridge, Tenn. Levels of merA mRNA transcripts and the rate of inorganic mercury [Hg(II)] volatilization were related to the concentration of mercury in the water and to heterotrophic activity in field samples and laboratory incubations of pond water in which microbial heterotrophic activity and Hg(II) concentration were manipulated. Levels of merA-specific mRNA and Hg(II) volatilization were influenced more by microbial metabolic activity than by the concentration of mercury. merA-specific transcripts were detected in some samples which did not reduce Hg(II), suggesting that rates of mercury volatilization in environmental samples may not always be proportional to merA expression.
Utilization of Dissolved Nitrogen by Heterotrophic Bacterioplankton: a Comparison of Three Ecosystems
Authors: Kroer Niels , Jørgensen Niels O. G. , Coffin Richard B.
Published: January 2020

The contributions of different organic and inorganic nitrogen and organic carbon sources to heterotrophic bacterioplankton in batch cultures of oceanic, estuarine, and eutrophic riverine environments were compared. The importance of the studied compounds was surprisingly similar among the three ecosystems. Dissolved combined amino acids (DCAA) were most significant, sustaining from 10 to 45% of the bacterial carbon demands and from 42 to 112% of the bacterial nitrogen demands. Dissolved free amino acids (DFAA) supplied 2 to 7% of the carbon and 6 to 24% of the nitrogen incorporated into the bacterial biomass, while dissolved DNA (D-DNA) sustained less than 5 and 12% of the carbon and nitrogen requirements, respectively. Ammonium was the second most important source of nitrogen, meeting from 13 to 45% of the bacterial demand in the oceanic and estuarine cultures and up to 270% of the demand in riverine cultures. Nitrate was taken up in the oceanic cultures (uptake equaled up to 46% of the nitrogen demand) but was released in the two others. Assimilation of DCAA, DFAA, and D-DNA combined supplied 43% of the carbon demand of the bacteria in the oceanic cultures, while approximately 25% of the carbon requirements were met by the three substrates at the two other sites. Assimilation of nitrogen from DCAA, DFAA, D-DNA, NH
4
+
, and NO
3
-
, on the other hand, exceeded production of particulate organic nitrogen in one culture at 27 h and in all cultures over the entire incubation period (50 h). These results suggest that the studied nutrient sources may fully support the nitrogen needs but only partially support the carbon needs of microbial communities of geographically different ecosystems. Furthermore, a comparison of the initial concentrations of the different substrates indicated that relative pool sizes of the substrates seemed to influence which substrates were primarily being utilized by the bacteria.
Expression of tfx and sensitivity to the rhizobial peptide antibiotic trifolitoxin in a taxonomically distinct group of alpha-proteobacteria including the animal pathogen Brucella abortus
Authors: Triplett E W , Breil B T , Splitter G A
Published: January 2020

Three phylogenetically distinct groups within the alpha-proteobacteria which differ in trifolitoxin sensitivity are described. Trifolitoxin sensitivity was found in strains of Agrobacterium, Brucella, Mycoplana, Ochrobactrum, Phyllobacterium, Rhodobacter, Rhodopseudomonas, Rhodospirillum, and Rhizobium. Strains of Agrobacterium, Brucella, Phyllobacterium, Rhizobium, and Rhodospirillum were capable of producing trifolitoxin upon conjugal transfer of tfxABCDEFG.
Formaldehyde Solution Effectively Inactivates Spores of
Bacillus anthracis
on the Scottish Island of Gruinard
Authors: Manchee Richard J. , Broster Malcolm G. , Stagg Anthony J. , Hibbs Stephen E.
Published: January 2020

Gruinard Island was heavily contaminated with the spores of virulent
Bacillus anthracis
during biological weapons trials in World War II. However, an extensive survey in 1979 showed that most of the island was not contaminated. In the early 1980s, a more intensive survey revealed that the contamination was largely confined to the top 8 cm of the soil in a 2.6-ha area of the 211-ha island. Small-scale tests showed that the spores could be inactivated by drenching the soil with fluid biocides. A solution of 5% formaldehyde in seawater applied by surface spray to each square meter of ground was shown to be the most effective treatment and was utilized for large-scale decontamination of the affected areas. Following this treatment, extensive sampling revealed that most of the spores of
B. anthracis
had been inactivated. Isolated pockets of surviving spores were treated further. A flock of sheep was then allowed to graze over the entire island for 5 months; none contracted anthrax.
Efficacy of Nucleic Acid Probes for Detection of Poliovirus in Water Disinfected by Chlorine, Chlorine Dioxide, Ozone, and UV Radiation
Authors: Moore Norman J. , Margolin Aaron B.
Published: January 2020

MilliQ water was inoculated with poliovirus type 1 strain LSc-1 and was treated with disinfectants, including chlorine, chlorine dioxide, ozone, and UV light. No relationship between probes and plaque assays were seen, demonstrating that viral nucleic acids were not destroyed. These findings suggest that nucleic acid probes cannot distinguish between infectious and noninfectious viruses and cannot be used in the evaluation of treated waters.
Expression of mosquitocidal toxin genes in a gas-vacuolated strain of Ancylobacter aquaticus
Authors: Yap W H , Thanabalu T , Porter A G
Published: January 2020

A series of plasmids bearing the binary toxin genes of Bacillus sphaericus 2297 or 2317.3, the 100-kDa toxin gene of B. sphaericus SSII-1, or the 130-kDa (cryIVB) toxin gene of Bacillus thuringiensis subsp. israelensis were constructed and introduced into Ancylobacter aquaticus by electroporation. The transformed A. aquaticus cells exhibited significant toxicity towards mosquito larvae, demonstrating a potential use of recombinant A. aquaticus for biological control of mosquitoes.
Duplication of the lantibiotic structural gene in M-type 49 group A streptococcus strains producing streptococcin A-M49
Authors: Hynes W L , Friend V L , Ferretti J J
Published: January 2020

Streptococcin A-M49 is produced by certain strains of M-type 49 group A streptococci. The structural gene for streptococcin A-M49 was cloned after hybridization with a probe containing the scnA lantibiotic structural gene. Sequence analysis revealed a duplication of the scnA gene; each gene (scnA' and scnA") encoded a 51-amino-acid prepeptide.
Cloning of Frankia species putative tRNA(Pro) genes and their efficacy for pSAM2 site-specific integration in Streptomyces lividans
Authors: Alegre M T , Cournoyer B , Mesas J M , Guérineau M , Normand P , Pernodet J L
Published: January 2020

pSAM2 is a conjugative Streptomyces ambofaciens mobile genetic element that can transfer and integrate site specifically in the genome. The chromosomal attachment site (attB) for pSAM2 site-specific recombination for two Frankia species was analyzed. It overlaps putative proline tRNA genes having a 3'-terminal CCA sequence, an uncommon feature among actinomycetes. pSAM2 is able to integrate into a cloned Frankia attB site harbored in Streptomyces lividans. The integration event removes the 3'-terminal CCA sequence and introduces a single nucleotide difference in the T psi C loop of the putative Frankia tRNA(Pro) gene. Major differences between the attP sequence from pSAM2 and the Frankia attB sequence restrict the identity segment to a 43-bp-long region. Only one mismatch is found between these well-conserved att segments. This nucleotide substitution makes a BstBI recognition site in Frankia attB and was used to localize the recombination site in a 25-bp region going from the anticodon to the T psi C loop of the tRNA(Pro) sequence. Integration of pSAM2 into the Frankia attB site is the first step toward introduction of pSAM2 derivatives into Frankia spp.
Biotransformations of Aroclor 1242 in Hudson River test tube microcosms
Authors: Fish K M , Principe J M
Published: January 2020

A microcosm system to physically model the fate of Aroclor 1242 in Hudson River sediment was developed. In the dark at 22 to 25 degrees C with no amendments (nutrients, organisms, or mixing) and with overlying water being the only source of oxygen, the microcosms developed visibly distinct aerobic and anaerobic compartments in 2 to 4 weeks. Extensive polychlorinated biphenyl (PCB) biodegradation was observed in 140 days. Autoclaved controls were unchanged throughout the experiments. In the surface sediments of these microcosms, the PCBs were biologically altered by both aerobic biodegrading and reductive dechlorinating microorganisms, decreasing the total concentration from 64.8 to 18.0 micromol/kg of sediment in 1140 days. This is the first laboratory demonstration of meta dechlorination plus aerobic biodegradation in stationary sediments. In contrast, the primary mechanism of microbiological attack on PCBs in aerobic subsurface sediments was reductive dechlorination. The concentration of PCBs remained constant at 64.8 micromol/kg of sediment, but the average number of chlorines per biphenyl decreased from 3.11 to 1.84 in 140 days. The selectivities of microorganisms in these sediments were characterized by meta and para dechlorination. Our results provide persuasive evidence that naturally occurring microorganisms in the Hudson River have the potential to attack the PCBs from Aroclor 1242 releases both aerobically and anaerobically at rapid rates. These unamended microcosms represent a unique method for determining the fate of released PCBs in river sediments.
Mineralization of the herbicide atrazine as a carbon source by a Pseudomonas strain
Authors: Yanze-Kontchou C , Gschwind N
Published: January 2020

Strain YAYA6 was isolated from a mixed microbial community that was growing on atrazine as a sole carbon source and formed quantitative amounts of chloride and nitrate. This strain was identified as a member of the true pseudomonad group (RNA group I) and was given the designation DMS 93-99. The growth yield when atrazine was the sole carbon and nitrogen source was 80 g (dry weight) of cells per mol of atrazine, and the cell doubling time was around 11 h. Approximately 20% of [U-ring 14C]atrazine was mineralized during primary degradation of atrazine. After atrazine disappeared from the culture supernatant, mineralization continued until the level of mineralization was more than 50%. Under different experimental conditions 10% of the atrazine supplied initially was converted to cyanuric acid and < 1% was converted to other s-triazines after prolonged incubation. Degradation proceeded via dechlorination and N-dealkylation. Atrazine was degraded until the concentration was circa 0.1 milligrams/liter. We obtained evidence showing that strain YAYA6 has specific uptake mechanisms for atrazine but less specific degradation mechanisms for s-triazines.
Construction of an expression system for engineering of the lantibiotic Pep5
Authors: Bierbaum G , Reis M , Szekat C , Sahl H G
Published: January 2020

Pep5 is a lanthionine-containing antimicrobial peptide which is produced by Staphylococcus epidermidis 5. Its structural gene, pepA, is located on the 20-kb plasmid pED503. A 6.2-kb fragment of pED503 containing pepA, the immunity gene pepI, and 5.4 kb of downstream sequence was able to direct biosynthesis of biologically active Pep5 in a nonproducing variant of the producer strain which is devoid of pED503. In addition to producing wild-type Pep5 with a molecular mass of 3,488 Da, the clone produced a peptide with an eightfold-lower bactericidal activity and a mass of 3,506 Da, indicative of incomplete dehydration of one hydroxyamino acid. For construction of the expression system, this 6.2-kb fragment was cut into a 1.39-kb fragment containing pepA and pepI and a 4.8-kb fragment covering the remaining downstream region. This 4.8-kb fragment was directly cloned into an Escherichia coli-Staphylococcus shuttle vector, yielding a new plasmid (pGB9) into which mutated pepA genes generated on the 1.39-kb fragment can be reinserted to yield a functional Pep5 biosynthesis gene cluster. To test the expression system, two mutants were constructed. Lys-18-Pro Pep5 was produced in its dehydrated form and a partially hydrated form in amounts comparable to those of the wild-type peptide. In contrast, only small amounts of Phe-23-Asp Pep5 were excreted, indicating that some residues in the propeptide part of the prelantibiotic may be crucial for certain steps in the biosynthetic pathway of lantibiotics.
Flow cytometric analysis of the cellular DNA content of Salmonella typhimurium and Alteromonas haloplanktis during starvation and recovery in seawater
Authors: Lebaron P , Joux F
Published: January 2020

Flow cytometry was used to investigate the heterogeneity of the DNA content of Salmonella typhimurium and Alteromonas haloplanktis cells that were starved and allowed to recover in seawater. Hoechst 33342 (bisbenzimide) was used as a DNA-specific dye to discriminate between DNA subpopulations. The DNA contents of both strains were heterogeneous during starvation. S. typhimurium cells contained one or two genomes, and A. haloplanktis cells contained up to six genomes. S. typhimurium genomes were fully replicated at the onset of starvation. Each replication cycle was completed in the early stage of starvation for A. haloplanktis by stopping cells in the partition step of the cell cycle prior to division. Multigenomic marine cells can undergo rapid cell division without DNA synthesis upon recovery, resulting in large fluctuations in the DNA contents of individual cells. In contrast, the heterogeneity of the DNA distribution of S. typhimurium cells was preserved during recovery. The fluctuations in the DNA fluorescence of this strain seem to be due to topological changes in DNA. Flow cytometry may provide a new approach to understanding dynamic and physiological changes in bacteria by detecting cellular heterogeneity in response to different growth conditions.
Parallel formation and synergism of hydrolytic enzymes and peptaibol antibiotics, molecular mechanisms involved in the antagonistic action of Trichoderma harzianum against phytopathogenic fungi
Authors: Schirmböck M , Lorito M , Wang Y L , Hayes C K , Arisan-Atac I , Scala F , Harman G E , Kubicek C P
Published: January 2020

Chitinase, beta-1,3-glucanase, and protease activities were formed when Trichoderma harzianum mycelia, grown on glucose as the sole carbon source, were transferred to fresh medium containing cell walls of Botrytis cinerea. Chitobiohydrolase, endochitinase, and beta-1,3-glucanase activities were immunologically detected in culture supernatants by Western blotting (immunoblotting), and the first two were quantified by enzyme-linked immunosorbent assay. Under the same conditions, exogenously added [U-14C]valine was incorporated in acetone-soluble compounds with an apparent M(r) of < 2,000. These compounds comigrated with the peptaibols trichorzianines A1 and B1 in thin-layer chromatography and released [U-14C]valine after incubation in 6N HCl. Incorporation of radioactive valine into this material was stimulated by the exogenous supply of alpha-aminoisobutyric acid, a rare amino acid which is a major constituent of peptaibols. The obtained culture supernatants inhibited spore germination as well as hyphal elongation of B. cinerea. Culture supernatants from mycelia placed in fresh medium without cell walls of B. cinerea did not show hydrolase activities, incorporation of [U-14C]valine into peptaibol-like compounds, and inhibition of fungal growth. Purified trichorzianines A1 and B1 as well as purified chitobiohydrolase, endochitinase, or beta-1,3-glucanase inhibited spore germination and hyphal elongation, but at concentrations higher than those observed in the culture supernatants. However, when the enzymes and the peptaibols were tested together, an antifungal synergistic interaction was observed and the 50% effective dose values obtained were in the range of those determined in the culture supernatants. Therefore, the parallel formation and synergism of hydrolytic enzymes and antibiotics may have an important role in the antagonistic action of T. harzianum against fungal phytopathogens.
Sambutoxin, a new mycotoxin produced by toxic Fusarium isolates obtained from rotted potato tubers
Authors: Kim J C , Lee Y W
Published: January 2020

Ninety-nine isolates of Fusarium species were obtained from rotted potato tubers from various parts of Korea. Of these isolates, 80 were identified as Fusarium oxysporum, F. solani, or F. sambucinum. The isolates of these species were grown on autoclaved wheat grains and examined for toxicity in a rat-feeding test. A total of 8 of 57 F. oxysporum isolates, 3 of 14 F. solani isolates, and 5 of 9 F. sambucinum isolates caused the death of the rats. Of the 16 toxic isolates, 1 isolate of F. oxysporum produced a substantial amount of moniliformin, which could account for its toxicity. None of the other 15 isolates produced trichothecenes, moniliformin, fusarochromanone, fumonisin B1, or wortmannin. F. sambucinum PZF-4 produced an unknown toxin in wheat culture. This new toxin, given the trivial name sambutoxin, caused toxic effects in rats, including body weight loss, feed refusal, hemorrhage in the stomach and intestines, and, finally, death when rats were fed diets supplemented with 0.05 and 0.1% sambutoxin. The toxin was also toxic to chicken embryos, and the 50% lethal concentration was 29.6 micrograms per egg. Sambutoxin formed as white crystals that turned purple when combined with reagents such as sulfuric acid and p-anisaldehyde. It exhibited a green color immediately after treatment with potassium ferricyanide-ferric chloride. Its UV spectrum had absorption maxima at 213, 233, and 254 nm, and its infrared spectrum showed an amide group at 1,650 and 1,560 cm-1 and a hydroxy group at 3,185 cm-1. Mass spectrometry showed that the molecular weight of the toxin was 453 and the molecular formula was C28H39NO4.(ABSTRACT TRUNCATED AT 250 WORDS)
Adaptation of Pseudomonas putida S12 to ethanol and toluene at the level of fatty acid composition of membranes
Authors: Heipieper H J , de Bont J A
Published: January 2020

Pseudomonas putida S12 was more tolerant to ethanol when preadapted to supersaturating concentrations of toluene. Cellular reactions at the membrane level to the toxicities of both compounds were different. In growing cells of P. putida S12, sublethal concentrations of toluene resulted in an increase in the degree of saturation of the membrane fatty acids, whereas toxically equivalent concentrations of ethanol led to a decrease in this value. Contrary to this, cells also reacted to both substances with a strong increase of the trans unsaturated fatty acids and a corresponding decrease of the cis unsaturated fatty acids under conditions where growth and other cellular membrane reactions were totally inhibited. While the isomerization of cis to trans unsaturated fatty acids compensates for the fluidizing effect caused by ethanol, a decrease in the degree of saturation is antagonistic with respect to the chemo-physical properties of the membrane. Consequently, the results support the hypothesis that the decrease in the degree of saturation induced by ethanol is not an adaptation mechanism but is caused by an inhibitory effect of the compound on the biosynthesis of saturated fatty acids.
Coexistence among Epiphytic Bacterial Populations Mediated through Nutritional Resource Partitioning
Authors: Wilson Mark , Lindow Steven E.
Published: January 2020

The levels of coexistence between
Pseudomonas syringae
and various nonpathogenic epiphytic species in the phyllosphere of beans (
Phaseolus vulgaris
) were assessed by using replacement series. The epiphytic species
Pseudomonas fluorescens, Pantoea agglomerans, Stenotrophomonas maltophilia,
and
Methylobacterium organophilum
were all capable of exhibiting higher levels of coexistence with
P. syringae
than was observed with a near-isogenic
P. syringae
strain pair. The ecological similarity of the epiphytes was estimated with niche overlap indices derived from in vitro carbon source utilization profiles. The level of coexistence of the epiphytes was inversely correlated with the ecological similarity of the strains. Hence, the level of coexistence between the epiphytes was proportional to the degree of niche differentiation, defined as the ability to utilize carbon sources not utilized by a competing strain. Comparisons of utilization profiles for groups of carbon sources (amino acids, organic acids, and carbohydrates) indicated the types of carbon sources for which the strains likely competed in the bean phyllosphere.
P. fluorescens
and
P. syringae
strains probably competed for most carbon sources.
S. maltophilia
and
M. organophilum
strains probably competed with
P. syringae
for most organic acids but few amino acids or carbohydrates.
P. agglomerans
strains probably competed with
P. syringae
for most amino acids and organic acids but few carbohydrates. A variable level of coexistence observed between
P. agglomerans
and
P. syringae
probably reflected the variability in abundance in the bean phyllosphere of the carbohydrates that
P. agglomerans
utilized exclusively.
Pathological and Molecular Characterization of
Xanthomonas campestris
Strains Causing Diseases of Cassava (
Manihot esculenta
)
Authors: Verdier Valérie , Boher Bernard , Maraite Henri , Geiger Jean-Paul
Published: January 2020

Fifty-one strains representing
Xanthomonas campestris
pv. manihotis and cassavae and different pathovars occurring on plants of the family Euphorbiaceae were characterized by ribotyping with a 16S+23S rRNA probe of
Escherichia coli
and by restriction fragment length polymorphism analysis with a plasmid probe from
X. campestris
pv. manihotis. Pathogenicity tests were performed on cassava (
Manihot esculenta
). Histological comparative studies were conducted on strains of two pathovars of
X. campestris
(vascular and mesophyllic) that attack cassava. Our results indicated that
X. campestris
pv. manihotis and cassavae have different modes of action in the host and supplemented the taxonomic data on restriction fragment length polymorphism that clearly separate the two pathovars. The plasmid probe could detect multiple restriction fragment length polymorphisms among strains of the pathovar studied. Ribotyping provides a useful tool for rapid identification of
X. campestris
pathovars on cassava.
Molecular analysis of mercury-resistant Bacillus isolates from sediment of Minamata Bay, Japan
Authors: Nakamura K , Silver S
Published: January 2020

Bacillus isolates from Minamata Bay sediment were selected for the ability to volatilize mercury from a range of organomercurials (including methylmercury). Chromosomal DNA from 74 of 78 such strains hybridized with the mer mercury resistance operon DNA from marine Bacillus sp. strain RC607 (Y. Wang, M. Moore, H. S. Levinson, S. Silver, C. Walsh, and I. Mahler, J. Bacteriol. 171:83-92, 1989). The most frequent classes with regard to restriction nuclease site maps of the mer operon for the new isolates were identical to or closely related to the mer determinant of strain RC607. PCR amplification analysis with primers designed from the strain RC607 mer operon gave products of precisely the predicted size with the 74 Minamata Bay isolates.
Trichloroethylene removal and oxidation toxicity mediated by toluene dioxygenase of Pseudomonas putida
Authors: Heald S , Jenkins R O
Published: January 2020

Whole cells of Pseudomonas putida containing toluene dioxygenase were able to remove all detectable trichloroethylene (TCE) from assay mixtures. The capacity of cells to remove TCE was 77 microM/mg of protein with an initial rate of removal of 5.2 nmol/min/ng of protein. TCE oxidation resulted in a decrease in the growth rate of cultures and caused rapid cell death. Addition of dithiothreitol to assay mixtures increased the TCE removal capacity of cells by up to 67% but did not prevent TCE-mediated cell death. TCE induced toluene degradation by whole cells to a rate approximately 40% of that induced by toluene itself.
Use of fluorescein-di-beta-D-galactopyranoside (FDG) and C12-FDG as substrates for beta-galactosidase detection by flow cytometry in animal, bacterial, and yeast cells
Authors: Plovins A , Alvarez A M , Ibañez M , Molina M , Nombela C
Published: January 2020

Fluorescein-di-beta-D-galactopyranoside (FDG) was found to be a useful substrate for beta-galactosidase detection by flow cytometry in gram-negative bacteria, since it entered viable cells and gave a fluorescence emission proportional to the enzymatic activity. C12-FDG, a more lipophilic derivative, gave a very poor signal because of the lack of penetration. On the contrary, C12-FDG was more sensitive than FDG for beta-galactosidase activity determinations in animal cells. In contrast to previous reports, C12-FDG did not enter viable yeast cells, so that the use of the substrate required cell permeabilization. Without this treatment, C12-FDG penetrates only nonviable yeast cells that may occur in populations expressing beta-galactosidase.
Production and Secretion of the Polysaccharide Biodispersan of
Acinetobacter calcoaceticus
A2 in Protein Secretion Mutants
Authors: Elkeles Adi , Rosenberg Eugene , Ron Eliora Z.
Published: January 2020

Biodispersan is an extracellular anionic polysaccharide produced by
Acinetobacter calcoaceticus
A2 that changes the surface properties of limestone and acts both as a dispersant and as a grinding aid (E. Rosenberg, C. Rubinovitz, A. Gottlieb, S. Rosenhak, and E. Z. Ron, Appl. Environ. Microbiol. 54:317-322, 1988; E. Rosenberg, C. Rubinovitz, R. Legmann, and E. Z. Ron, Appl. Environ. Microbiol. 54:323-326, 1988; E. Rosenberg, Z. Schwartz, A. Tenenbaum, C. Rubinovitz, R. Legmann, and E. Z. Ron, J. Dispersion Sci. Technol. 10:241-250, 1989). Extracellular fluid also contains a high concentration of secreted proteins that create problems in the purification and application of biodispersan. In order to obtain preparations of biodispersan that contained smaller amounts of protein, we selected mutants of strain A2 that were defective in protein secretion. These mutants produced equal, or even higher, levels of total biodispersan compared with those of the parental strain. Moreover, although there was a significant drop in the concentration of extracellular proteins in the medium, the secretion of biodispersan was unaffected. These results suggest that secretion mutants are potentially useful for the production of extracellular polysaccharides.
Effects of DNA Polymer Length on Its Adsorption to Soils
Authors: Ogram Andrew V. , Mathot Mark L. , Harsh James B. , Boyle Jeffrey , Pettigrew Charles A.
Published: January 2020

Three different DNA fragments ranging size from 2.69 kbp (1.75 MDa) to 23 kbp (14.95 MDa) were used as tracers to study the adsorption of polydisperse solutions of calf thymus DNA to eight model soils. The adsorption of the three tracers to all soils was described by the Freundlich adsorption model, with adsorption coefficients (
K
) ranging from 1.1 for acid-washed sand to over 300 for one soil. An inverse relationship between tracer size and
K
was observed with six of the eight soils, indicating that smaller fragments are sorbed preferentially versus larger fragments in these soils. No significant correlation between
K
and the organic carbon contents, clay contents, pHs, or cation exchange capacities of the model soils was observed.
Sphinganase, a new endoglycanase that cleaves specific members of the gellan family of polysaccharides
Authors: Mikolajczak M J , Thorne L , Pollock T J , Armentrout R W
Published: January 2020

A sporeforming gram-positive aerobic bacterium was isolated from soil and shown to secrete an endoglycanase that cleaves the tetrasaccharide backbone structure of specific members within the gellan family of related bacterial exopolysaccharides. We refer to these polysaccharides as sphingans. The structures of the sphingans differ by the type and position of side groups that are attached to the backbone. The new enzyme named sphinganase degrades welan, gellan, deacylated gellan, and polysaccharides S-88, S-7, and S-198. However, the enzyme does not attack rhamsan or polysaccharide NW11. Methods for growing the bacteria, isolating the enzyme, and assaying sphinganase activity are presented, and uses for the enzyme are proposed.
Genotypic and Phenotypic Comparisons of Chromosomal Types within an Indigenous Soil Population of
Rhizobium leguminosarum
bv. trifolii
Authors: Leung Kamtin , Strain Steven R. , de Bruijn Frans J. , Bottomley Peter J.
Published: January 2020

The relative genetic similarities of 200 isolates of
Rhizobium leguminosarum
bv. trifolii recovered from an Oregon soil were determined at 13 enzyme loci by multilocus enzyme electrophoresis (MLEE). These isolates represented 13 antigenically distinct serotypes recovered from nodules formed on various clover species. The MLEE-derived levels of relatedness among isolates of
R. leguminosarum
bv. trifolii were found to be in good agreement with the levels of relatedness established by using repetitive (repetitive extragenic palindromic and enterobacterial repetitive intergeneric consensus) sequences and the PCR technique and with levels of relatedness from previously published DNA reassociation studies. BIOLOG substrate utilization patterns showed that isolates within an electrophoretic type (ET) were phenotypically more similar to each other than to isolates of other ETs. The soil isolates were represented by 53 ETs which could be clustered into seven groups (groups B, E, G, H1, H2, I, and J). Evidence for multilocus structure within the population was obtained, and group B was identified as the primary creator of the disequilibrium. Of 75 isolates belonging to the nodule-dominant serotype AS6 complex, 72 were found in group B. Isolates WS2-01 and WS2-02 representing nodule-dominant serotypes recovered from subclover grown at another Oregon site were also found in group B. Isolates representing the most numerous ETs in group B (ETs 2 and 3) were either suboptimally effective or completely ineffective at fixing nitrogen on six different clover species. Another four groups of isolates (groups A, C, D, and F) were identified when 32 strains of diverse origins were analyzed by MLEE and incorporated into the cluster analysis. Group A was most dissimilar in comparisons with other groups and contained strain USDA 2124 (T24), which produces trifolitoxin and has unique symbiotic characteristics.
Nucleation of Celestite and Strontianite on a Cyanobacterial S-Layer
Authors: Schultze-Lam Susanne , Beveridge Terry J.
Published: January 2020

Synechococcus
strain GL24 is a unicellular cyanobacterium that was isolated from Fayetteville Green Lake, New York, a meromictic lake which has high Ca
2+
and SO
4
2-
concentrations. Epicellular mineralization of
Synechococcus
cells in the lake is the mechanism by which extensive calcitic bioherms (or microbial reefs) have been formed on the lake's shore and a marl sediment has been built on the lake bottom. Previous studies have shown that calcium carbonate (calcite) formation on the
Synechococcus
surface is dependent upon an alkaline pH, which is produced in the cellular microenvironment by the cells as their activity increases with seasonal warming of the lake water. At the circumneutral pH of bulk lake water, calcium sulfate (gypsum) is formed. In this study, we show that
Synechococcus
mediates a similar sulfate-to-carbonate transformation when Sr
2+
is the major divalent cation present, forming celestite and strontianite. In experimental systems to which equimolar amounts of Ca
2+
and Sr
2+
, Ca
2+
or Sr
2+
and Mg
2+
, or all three ions together were added to artificial lake water, Ca
2+
and Sr
2+
were incorporated equally into mineral formation to form CaSr(CO
3
)
2
. No Mg
2+
-containing carbonates were formed when either or both of the other two ions were present. Mineral formation takes place on a hexagonally arranged proteinaceous template (an S-layer) which forms the outermost surface of the
Synechococcus
cell. Our results provide evidence that the S-layer exhibits selectivity with respect to the ions bound and subsequently incorporated into carbonate minerals and that celestite and strontianite, previously thought to be purely evaporitic minerals, can be biogenically formed.
Ecology of Thermophilic Fungi in Mushroom Compost, with Emphasis on
Scytalidium thermophilum
and Growth Stimulation of
Agaricus bisporus
Mycelium
Authors: Straatsma Gerben , Samson Robert A. , Olijnsma Tineke W. , Op Den Camp Huub J. M. , Gerrits Jan P. G. , Van Griensven Leo J. L. D.
Published: January 2020

Twenty-two species of thermophilic fungi were isolated from mushroom compost.
Scytalidium thermophilum
was present in the compost ingredients, fresh straw, horse droppings, and drainage from compost and dominated the fungal biota of compost after preparation. Of 34 species of thermophilic fungi tested, 9 promoted mycelial growth of
Agaricus bisporus
on sterilized compost:
Chaetomium thermophilum
, an unidentified
Chaetomium
sp.,
Malbranchea sulfurea, Myriococcum thermophilum, S. thermophilum, Stilbella thermophila, Thielavia terrestris
, and two unidentified basidiomycetes. These species will be considered for future experiments on inoculation and more controlled preparation of compost.