Methylobacterium bullatum sp. nov., a methylotrophic bacterium isolated from Funaria hygrometrica

A novel, pink-pigmented aerobic, facultatively methylotrophic bacterial strain (F3.2^T) isolated from the phyllosphere of Funaria hygrometrica, was analyzed using a polyphasic approach. Cells were Gram-negative, motile rods, strictly aerobic and non-spore-forming and exhibited surface structures varying in quantity, distribution and morphology. The isolate grew at 10–33 °C over a pH range of 5.5–8.0 and in the presence of less than 1.0% NaCl. Strain F3.2^T shared less than 70% DNA–DNA binding to the next type strain of the genus Methylobacterium (M. adhaesivum DSM 17169^T). In addition to the major cellular fatty acid C_18:1ω7c (81.7%), present in all Methylobacterium species (and also members of the genus Alphaproteobacteria), a high value (11.7%) of the fatty acids (summed feature) C_16:1ω7c and/or iso-C_15:02OH was determined. Phylogenetic analyses based on 16S rDNA and methanol dehydrogenase gene sequences, DNA–DNA hybridization values, chemotaxonomic and phenotypic characteristics indicate that the strain F3.2^T represents a novel species within the genus Methylobacterium. We propose the name Methylobacterium bullatum sp. nov. for this species. The type strain is the strain F3.2^T (DSM 21893^T = LMG 24788^T).     

Synthesis,characterization and antimicrobial activities of some mixed ligand complexes of Co(II) with thiosemicarbazones and N-protected amino acids

The reaction of cobalt(II) chloride with a new class of thiosemicarbazones viz; cis-3,7-dimethyl-2,6-octadienthiosemicarbazone(CDOTSC; L₁H) and 3,7-dimethyl-6-octenethiosemicarbazone (DOTSC; L₂H) and N-phthaloyl derivative of DL-glycine(A₁H), L-alanine(A₂H) or L-valine(A₃H) in 1:1:1 molar ratio in dry refluxing ethanol have been studied. All the isolated complexes have the general composition [Co(L)(A)]. Tentative structures are proposed for these complexes based upon elemental analysis, electrical conductances, magnetic moment, molecular weight determination and spectral (IR, electronic) studies.The ligands and Co(II) complexes have been tested for their antibacterial and antifungal activities against three bacterial strains S. aureus, B. subtilis, E. coli and two fungal strains F. moniliformae and M. phaseolina. Attempts have been made to establish a correlation between the antibacterial and antifungal activity and the structures of products.     

Rhizobacteria and their potential to control <Emphasis Type="Italic">Fusarium verticillioides</Emphasis>: effect of maize bacterisation and inoculum density

Fusarium verticillioides is the most important seed transmitted pathogen that infects maize. It produces fumonisins, toxins that have potential toxicity for humans and animals. Control of F. verticillioides colonisation and systemic contamination of maize has become a priority area in food safety research. The aims of this research were (1) to characterise the maize endorhizosphere and rhizoplane inhabitant bacteria and Fusarium spp., (2) to select bacterial strains with impact on F. verticillioides growth and fumonisin B₁ production in vitro, (3) to examine the effects of bacterial inoculum levels on F. verticillioides root colonisation under greenhouse conditions. Arthrobacter spp. and Azotobacter spp. were the predominant genera isolated from maize endorhizosphere and rhizoplane at the first sampling period, whilst F. verticillioides strains showed the greatest counts at the same isolation period. All F. verticillioides strains were able to produce fumonisin B₁ in maize cultures. Arthrobacter globiformis RC5 and Azotobacter armeniacus RC2, used alone or in a mix, demonstrated important effects on F. verticillioides growth and fumonisin B₁ suppression in vitro. Only Azotobacter armeniacus RC2 significantly reduced the F. verticillioides root colonisation at 10⁶ and 10⁷ CFU g^–1 levels under greenhouse conditions.     

Genetic and physical mapping of xa13, a recessive bacterial blight resistance gene in rice

 The recessive gene, xa13, confers resistance to Philippine race 6 (PXO99) of the bacterial blight pathogen Xanthomonas oryzae pv oryzae. Fine genetic mapping and physical mapping were conducted as initial steps in an effort to isolate the gene. Using nine selected DNA markers and two F₂ populations of 132 and 230 plants, xa13 was fine-mapped to a genomic region <4 cM on the long arm of rice chromosome 8, flanked by two RFLP markers, RG136 and R2027. Four DNA markers, RG136, R2027, S14003, and G1149, in the target region were used to identify bacterial artificial chromosome (BAC) clones potentially harboring the xa13 locus from a rice BAC library. A total of 11 BACs were identified, forming four separate contigs including a single-clone contig, 29I3, associated with the RG136 STS marker, the S14003 contig consisting of four clones (44F8, 41O2, 12A16, and 12F20), the G1149 contig with two clones, 23D11 and 21H18, and the R2027 contig consisting of four overlapping clones, 42C23, 30B5, 6B7 and 21H14. Genetic mapping indicated that the xa13 locus was contained in the R2027 contig. Chromosomal walking on the R2027 contig resulted in two more clones, 33C7 and 14L3. DNA fingerprinting showed that the six clones of the R2027 contig were overlapping. Clone 44F8 hybridized with a single fragment from the clone 14L3, integrating the R2027 and S14003 contigs into a single contig consisting of ten BAC clones with a total size of approximately 330 kb. The physical presence of the xa13 locus in the contig was determined by mapping the ends of the BAC inserts generated by TAIL-PCR. In an F₂ population of 230 plants, the BAC-end markers 42C23R and 6B7F flanked the xa13 locus. The probes 21H14F and 21H14R derived from BAC clone 21H14 were found to flank xa13 at a distance of 0.5 cM on either side, using a second F₂ population of 132 plants. Thus, genetic mapping indicated that the contig and the 96-kb clone, 21H14, contained the xa13 locus. Received: 15 August 1998 / Accepted: 29 September 1998     

Three QTLs from Lycopersicon peruvianum confer a high level of resistance to Clavibactermichiganensis ssp. michiganensis

Lycopersicon peruvianum LA2157 originates from 1650 m above sea level and harbours several beneficial traits for cultivated tomatoes such as cold tolerance, nematode resistance and resistance to bacterial canker (Clavibacter michiganensis ssp. michiganensis). In order to identify quantitative trait loci (QTLs) for bacterial canker resistance, a QTL mapping approach was carried out in an F₂ population derived from the interspecific F₁ between Lycopersicon esculentum cv Solentos and L. peruvianum LA2157. Three QTLs for resistance mapped to chromosomes 5, 7 and 9 respectively. The resistance loci were additive and co-dominant with the QTL on chromosome 7 explaining the largest part of the variation for resistance in the F₂ population. The combination of this QTL with either of the other two QTLs conferred a resistance similar to the level in the resistant parent L. peruvianum. Some RFLP markers flanking this QTL on chromosome 7 were converted into SCAR markers allowing efficient marker-assisted selection of plants with high resistance to bacterial canker. Received: 26 February 1999 / Accepted: 12 March 1999     

The degradation and utilization of wheat-straw cell-wall monosaccharide components by defined ruminal cellulolytic bacteria

Cell walls (CW) of untreated wheat straw and sulphur-dioxide (SO₂)-treated wheat straw were used as model substrates for the hydrolysis and utilization of CW carbohydrates by pure cultures or pair-combinations of defined rumen bacterial strains. Fibrobacter succinogenes S85 and BL2 strains and their co-cultures with D1 were the best degraders of CW among ruminal cultures, solubilizing 37.2–39.6% of CW carbohydrates of untreated straw and 62.2–74.5% of SO₂-treated straw. Complementary action between Butyrivibrio fibrisolvens D1 and the F. succinogenes strains was identified with respect to co-culture growth and carbohydrate utilization. However, the extent of CW solubilization was determined mainly by the F. succinogenes strains. In both substrates, utilization of solubilized cellulose by F. succinogenes S85 and BL2 monocultures was higher than that of xylan and hemicellulose: 96.5–98.3%, 34.4–40.5% and 33.5–36.2%, respectively. Under scanning electron microscopy visualization, S85 and BL2 cells of the co-cultures comprised the most dense layer of bacterial cell mass attached to and colonized on straw stems and leaves, whereas D1 cells were always nearby. Stems and leaves of the untreated straw were less crowded by attached bacteria than that of the SO₂-treated straw. In both materials, the cell surface topography of S85 and BL2 bacteria attached to CW particles was specified by a coat of characteristic protuberant structures, polycellulosome complexes.     

Biodefluorination and biotransformation of fluorotelomer alcohols by two alkane‐degrading Pseudomonas strains

Fluorotelomer alcohols [FTOHs, F(CF₂)_nCH₂CH₂OH, n = 4, 6, and 8] are emerging environmental contaminants. Biotransformation of FTOHs by mixed bacterial cultures has been reported; however, little is known about the microorganisms responsible for the biotransformation. Here we reported biotransformation of FTOHs by two well‐studied Pseudomonas strains: Pseudomonas butanovora (butane oxidizer) and Pseudomonas oleovorans (octane oxidizer). Both strains could defluorinate 4:2, 6:2, and 8:2 FTOHs, with a higher degree of defluorination for 4:2 FTOH. According to the identified metabolites, P. oleovorans transformed FTOHs via two pathways I and II. The pathway I led to the production of x:2 ketone [dominant metabolite, F(CF₂)_xC(O)CH₃; x = n ? 1, n = 6 or 8], x:2 sFTOH [F(CF₂)_xCH(OH)CH₃], and perfluorinated carboxylic acids (PFCAs, perfluorohexanoic, or perfluorooctanoic acid). The pathway II resulted in the formation of x:3 polyfluorinated acid [F(CF₂)_xCH₂CH₂COOH] and relatively minor shorter‐chain PFCAs (perfluorobutyric or perfluorohexanoic acid). Conversely, P. butanovora transformed FTOHs by using the pathway I, leading to the production of x:2 ketone, x:2 sFTOH, and PFCAs. This is the first study to show that individual bacterium can bio‐transform FTOHs via different or preferred transformation pathways to remove multiple ? CF₂? groups from FTOHs to form shorter‐chain PFCAs. Biotechnol. Bioeng. 2012; 109: 3041–3048. © 2012 Wiley Periodicals, Inc.     

Optimization of the production of bacterial cellulose using multivariable linear regression analysis

The biosynthesis of bacterial cellulose by Acetobacter xylinum was optimized by numerically finding the maximum of an arbitrarily chosen second order polynomial model function of several variables (describing the dependence of the cellulose production on the concentrations of the medium components), using multivariable linear regression analysis. The chosen function appeared to describe the analyzed correlation sufficiently well. Consequently, three to six stages of optimization made the determination of the optimum medium compositions possible for 16 days of fermentation at 30°C in a medium based on fructose (wt%: fructose, 3.68; yeast extract, 5.02; (NH₄)₂NO₃, 0.001; KH₂PO₄, 0.3; MgSO₄ × 7 H₂O, 0.05; resulting in a cellulose production equal to 0.505 wt.% – namely 5.6 times higher than before the optimization) and for 7 days fermentations at 30°C in a medium based on sucrose and ethanol (wt.%: sucrose, 5.0; ethanol, 1.36; yeast extract, 1.27; (NH₄)₂SO₄, 0.5; KH₂PO₄, 0.3; MgSO₄ × 7 H₂O, 0.05; resulting in a cellulose production equal to 0.251 wt.% – namely 1.5 times higher than before the optimization).     

The crystal structure of rice (Oryza sativa L.) Os4BGlu12, an oligosaccharide and tuberonic acid glucoside-hydrolyzing β-glucosidase with significant thioglucohydrolase activity

Rice Os4BGlu12, a glycoside hydrolase family 1 (GH1) β-glucosidase, hydrolyzes β-(1,4)-linked oligosaccharides of 3–6 glucosyl residues and the β-(1,3)-linked disaccharide laminaribiose, as well as certain glycosides. The crystal structures of apo Os4BGlu12, and its complexes with 2,4-dinitrophenyl-2-deoxyl-2-fluoroglucoside (DNP2FG) and 2-deoxy-2-fluoroglucose (G2F) were solved at 2.50, 2.45 and 2.40 Å resolution, respectively. The overall structure of rice Os4BGlu12 is typical of GH1 enzymes, but it contains an extra disulfide bridge in the loop B region. The glucose ring of the G2F in the covalent intermediate was found in a ⁴C₁ chair conformation, while that of the noncovalently bound DNP2FG had a ¹S₃ skew boat, consistent with hydrolysis via a ⁴H₃ half-chair transition state. The position of the catalytic nucleophile (Glu393) in the G2F structure was more similar to that of the Sinapsis alba myrosinase G2F complex than to that in covalent intermediates of other O-glucosidases, such as rice Os3BGlu6 and Os3BGlu7 β-glucosidases. This correlated with a significant thioglucosidase activity for Os4BGlu12, although with 200- to 1200-fold lower k_cat/K_m values for S-glucosides than the comparable O-glucosides, while hydrolysis of S-glucosides was undetectable for Os3BGlu6 and Os3BGlu7.     

Variability and characterization of mycotoxin-producing Fusarium spp isolates by PCR-RFLP analysis of the IGS-rDNA region

In the present report, a total of 75 Fusarium spp isolates (35 of the Gibberella fujikuroi species complex, 26 of F. oxysporum, 7 of F. graminearum, 5 of F. culmorum, 1 of F. cerealis, and 1 of F. poae) from different hosts were characterized morphologically, physiologically and genetically. Morphological characterization was performed according to macroscopic and microscopic aspects. Physiological characterization was based on their ability to produce fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), zearalenone (ZEA) and type B trichothecenes (deoxynivalenol, nivalenol and 3-acetyldeoxynivalenol). FB₁, FB₂, and ZEA were determined by liquid chromatography and trichothecenes by gas chromatography. Molecular characterization of isolates was carried out using an optimized and simple method for isolation of DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the intergenic spacer region (IGS) of the rDNA. The results indicated that G. fujikuroi complex isolates can be␣divided into low and high fumonisin producers. The haplotypes obtained with HhaI, EcoRI, AluI, PstI and XhoI enzymes provided very characteristic groupings of G. fujikuroi isolates as a function of host type and fumonisin producing capacity. F. graminearum, F. culmorum and F. cerealis isolates were high ZEA␣and type B trichothecene producers, while F. oxysporum and the G. fujikuroi complex isolates did not show this ability. The haplotypes obtained with CfoI, AluI, HapII, XhoI, EcoRI and PstI enzymes permitted to discern these five Fusarium species and G. fujikuroi complex isolates but the restriction patterns of the IGS region did not show any relationship with the geographic origin of isolates.     

Effects of biocontrol agents on Fusarium verticillioides count and fumonisin content in the maize agroecosystem: Impact on rhizospheric bacterial and fungal groups

The present study tested the ability of Bacillus amyloliquefaciens and Microbacterium oleovorans to reduce Fusarium verticillioides populations and fumonisin accumulation in the maize agroecosystem. The impact of releasing these biocontrol agents on rhizospheric bacterial and fungal groups was also evaluated through isolation and identification of culturable microorganisms. When applied as seed coatings at a concentration of 10⁷ CFU ml⁻¹ both agents were effective in reducing F. verticillioides counts and fumonisin B₁ and B₂ content from maize grains. Rhizospheric counts of the pathogen were also decreased by use of B. amyloliquefaciens at 10⁷ CFU ml⁻¹. Richness and diversity indexes calculated for bacteria and fungi inhabiting the rhizosphere of maize remained unchanged following the addition of both biocontrol agents to seeds. Our research is being continued to further characterize the bacterial and fungal isolates with additional field assays.     

A Monogenic Dominant Resistance of Tomato to Bacterial Wilt in Hawaii 7996 is Associated with Plant Colonization by Pseudomonas solanacearum

Hawaii 7996, a tomato cultivar resistant to bacterial wilt caused by P. solanacearum was crossed with Floradel, a susceptible cultivar and the F1 and F2 seeds were obtained. Inoculated plants were tested in the field for bacterial wilt resistance and colonization by P. solanacearum. The F1 did not wilt and a significant 3:1 segregation for non wilting: wilting was observed in the F2, indicating a monogenic dominant resistance in Hawaii 7996. In the F2 and in Hawaii 7996, resistance was, associated to the limitation of bacterial spread in the stem. The degree of resistance of Floradel, the F2 and Hawaï 7996 was correlated to colonization at midstem. The usefulness of plant colonization criteria for breeding programs is discussed.     

Determination of flunitrazepam and its metabolites in blood by high-performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry

A selective assay of flunitrazepam (F) and its metabolites 7-aminoflunitrazepam (7-AF), N-desmethylflunitrazepam (N-DF) and 3-hydroxyflunitrazepam (3-OHF) with liquid chromatography–atmospheric pressure chemical ionization mass spectrometry (LC–APCI-MS, positive ions) is described. The drugs were isolated from serum, blood or urine using a solid-phase extraction procedure previously applied to various drugs of abuse. F-d₃ and 7-AF-d₃ were used as internal standards. The drugs were separated on ODS column in acetonitrile–50 mM ammonium formate buffer, pH 3.0 (45:55, v/v). After analysis of mass spectra taken in full scan mode, a selected-ion monitoring detection was applied with following ions: m/z 284 (7-AF and F), 287 (7-AF-d₃ and F-d₃), 314 (F), 300 (N-DF and 3-OHF), 317 (F-d₃), 330 (3-OHF). The limits of detection were: 0.2 μg/l for F and 7-AF, 1 μg/l for N-DF and 3-OHF. The method was linear in the range 1–500 μg/l, the recoveries ranged from 92 to 99%. The method was applied for determination of F and metabolites in clinical and forensic samples. LC–APCI-MS seems to be a method of choice for these compounds.     

Structural analysis of nested neutralizing and non‐neutralizing B cell epitopes on ricin toxin's enzymatic subunit

In this report, we describe the X‐ray crystal structures of two single domain camelid antibodies (V_HH), F5 and F8, each in complex with ricin toxin's enzymatic subunit (RTA). F5 has potent toxin‐neutralizing activity, while F8 has weak neutralizing activity. F5 buried a total of 1760 Ų in complex with RTA and made contact with three prominent secondary structural elements: α‐helix B (Residues 98–106), β‐strand h (Residues 113–117), and the C‐terminus of α‐helix D (Residues 154–156). F8 buried 1103 Ų in complex with RTA that was centered primarily on β‐strand h. As such, the structural epitope of F8 is essentially nested within that of F5. All three of the F5 complementarity determining regions CDRs were involved in RTA contact, whereas F8 interactions were almost entirely mediated by CDR3, which essentially formed a seventh β‐strand within RTA's centrally located β‐sheet. A comparison of the two structures reported here to several previously reported (RTA‐V_HH) structures identifies putative contact sites on RTA, particularly α‐helix B, associated with potent toxin‐neutralizing activity. This information has implications for rational design of RTA‐based subunit vaccines for biodefense. Proteins 2016; 84:1162–1172. © 2016 Wiley Periodicals, Inc.     

Variation of acharan sulfate and monosaccharide composition and analysis of neutral <Emphasis Type="Italic">N</Emphasis>-glycans in African giant snail (<Emphasis Type="Italic">Achatina fulica</Emphasis>)

Acharan sulfate content from African giant snail (Achatina fulica) was compared in eggs and snails of different ages. Acharan sulfate was not found in egg. Acharan sulfate disaccharide →4)-α-d-GlcNpAc (1→4)-α-l-IdoAp2S(1→, analyzed by SAX (strong-anion exchange)–HPLC was observed soon after hatching and increases as the snails grow. Monosaccharide compositional analysis showed that mole % of glucosamine, a major monosaccharide of acharan sulfate, increased with age while mole % of galactose decreased with age. These results suggest that galactans represent a major energy source during development, while acharan sulfate appearing immediately after hatching, is essential for the snail growth. The structures of neutral N-glycans released from eggs by peptide N-glycosidase F (PNGase F), were next elucidated using ESI-MS/MS, MALDI-MS/MS, enzyme digestion, and monosaccharide composition analysis. Three types of neutral N-glycan structures were observed, truncated (Hex_2–4-HexNAc₂), high mannose (Hex_5–9-HexNAc₂), and complex (Hex₃-HexNAc_2–10) types. None showed core fucosylation.     

Calculation of protonation patterns in proteins with structural relaxation and molecular ensembles – application to the photosynthetic reaction center

The conventional method to determine protonation patterns of proteins was extended by explicit consideration of structural relaxation. The inclusion of structural relaxation was achieved by alternating energy minimization with the calculation of protonation pattern in an iterative manner until consistency of minimized structure and protonation pattern was reached. We applied this method to the bacterial photosynthetic reaction center (bRC) of Rps. viridis and could show that the relaxation procedure accounts for the nuclear polarization and therefore allows one to lower the dielectric constant for the protein from the typically chosen value of ɛ _p = 4 to a value of ɛ _p = 2 without fundamentally changing the results. Owing to the lower dielectric shielding at ɛ _p = 2, the charges of the titratable groups interact more strongly, which leads to sampling problems during Monte Carlo titration. We solved this problem by introducing triple moves in addition to the conventional single and double moves. We also present a new method that considers ensembles of protein conformations for the calculation of protonation patterns. Our method was successfully applied to calculate the redox potential differences of the quinones in the bRC using the relaxed structures for the different redox states of the quinones. Received: 30 October 1997 / Revised version: 2 March 1998 / Accepted: 7 March 1998     

Expression of C4-like photosynthesis in several species of Flaveria

Abstract Photosynthetic metabolism was investigated in leaves of five species of Flaveria (Asteraceac), all previously considered to be C₄ plants. Leaves were exposed to ¹⁴CO₂ for different intervals up to 16s. Extrapolation of ¹⁴C-product curves to zero time indicated that only F. trinervia and F.bidentis assimilated atmospheric CO₂ exclusively through phosphoenolpyruvate carboxylase. The proportion of direct fixation of ¹⁴CO₂ by ribulose-I, 5-bisphosphate carboxylase/oxygenase (Rubisco) ranged from 5 to 10% in leaves of F. australasica. F. palmeri and F. vaginata. Protoplasts of leaf mesophyll and bundle sheath cells were utilized to examine the intercellular compartmentation of principal photosynthetic enzymes. Leaves of F. australasica, F. palmeri and F. vaginata contained 5 to 7% of the leaf's Rubisco activity in the mesophyll cells, while leaves of F. trinervia and F. bidentis contained at most 0.2 to 0.8% of such activity in their mesophyll cells. Thus, F. trinervia and F. bidentis have the complete C₄ syndrome, while F. australasica, F. palmeri and F. vaginata are less advanced, C₄-like species.     

Site-specific solvent exposure analysis of a membrane protein using unnatural amino acids and F nuclear magnetic resonance

Membrane proteins play an essential role in cellular metabolism, transportation and signal transduction across cell membranes. The scarcity of membrane protein structures has thus far prevented a full understanding of their molecular mechanisms. Preliminary topology studies and residue solvent exposure analysis have the potential to provide valuable information on membrane proteins of unknown structure. Here, a ¹⁹F-containing unnatural amino acid (trimethylfluoro-phenylalanine, tfmF) was applied to accomplish site-specific ¹⁹F spin incorporation at different sites in diacylglycerol kinase (DAGK, an Escherichia coli membrane protein) for site-specific solvent exposure analysis. Due to isotope effect on ¹⁹F spins, a standard curve for ¹⁹F-tfmF chemical shifts was drawn for varying solvent H₂O/D₂O ratios. Further site-specific ¹⁹F solvent isotope shift analysis was conducted for DAGK to distinguish residues in water-soluble loops, interfacial areas or hydrophobic membrane regions. This site-specific solvent exposure analysis method could be applied for further topological analysis of other membrane proteins.     

Fumonisin production by <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from freshly harvested corn in Iran

Fifty-one strains of Fusarium verticillioides and F. proliferatum isolated from corn collected from four different geographic areas in Iran, namely Fars, Khuzestan, Kermanshah and Mazandaran (an endemic oesophageal cancer (OC) area) were evaluated for their ability to produce fumonisins B₁ (FB₁), B₂ (FB₂) and B₃ (FB₃) in corn culture. Fumonisin levels were determined by high-performance liquid chromatography. All tested strains of F. verticillioides and F. proliferatumproduced fumonisins within a wide range of concentrations, 197–9661 g/g, 18–1974 g/g, and 21–1725 g/g for FB₁, FB₂, and FB₃, respectively. The highest mean concentrations of FB₁, FB₂, and FB₃ were 3897, 806 and 827 g/g, respectively. Overall, 61% of the F. verticillioides and F. proliferatum strains produced higher levels of FB₃ than FB₂. The mean ratios of FB₁:FB₂, FB₁:FB₃ and FB₁:total fumonisins were 8, 7 and 0.7 for F. verticillioides and 5.7, 10.7 and 0.7 for F. proliferatum, respectively. Significant differences in some of the meteorological data (rainfall, relative humidity and minimum temperature) from the four provinces were observed. Fumonisin levels produced by F. verticillioides strains isolated from Khuzestan province (tropical zone) were significantly (P < 0.01) higher than the other three provinces. This is the first report of the fumonisin-producing ability of F.verticillioides and F. proliferatum strains isolated from corn harvested from different geographic areas in Iran.     

Digestion of structural polysaccharides of Panicum and vetch hays by the rumen bacterial strains Fibrobacter succinogenes BL2 and Butyrivibrio fibrisolvens D1

The rumen bacterial strains Fibrobacter succinogenes BL2 and Butyrivibrio fibrisolvens D1, were grown in monocultures and pair combination on cell walls (CW) of two tropical hays: Panicum (grass) and vetch (legume), and their ability to solubilize and utilize CW structural carbohydrate was determined. With respect to both substrates, F. succinogenes BL2 was a better solubilizer of CW carbohydrate than B. fibrisolvens D1. However, the solubilization of Panicum constituents by any bacterial monoculture and co-culture was higher than that of vetch. Complementary interaction between B. fibrisolvens D1 and F. succinogenes BL2 was identified only with respect to carbohydrate utilization, but not with the extent of CW solubilization, which was determined mainly by the F. succinogenes strain. In both substrates, utilization of solubilized cellulose by BL2 monocultures was high (86.4–97.5%), whereas that of solubilized xylan and hemicellulose was much lower (35.2–41.6%). Under scanning electron microscopy visualization, the BL2 bacterial cell mass attached to and colonized on CW particles was characterized by the appearance of protuberant structures known as polycellulosome complexes on their surface topology. Correspondence to: J. Miron