Phleichrome; A New Phytotoxic Compound Produced by Cladosporium phlei

Bottle choice tests using liquid diets were done with Sprague-Dawley (SD) rats. SD rats ingested more oil-and-sucrose-enriched milk (hi-fat) and less oil-enriched milk (hi-fat-no-carb) than sucrose-enriched (hi-carb) milk by two-bottle choice tests after they were habituated to liquid diets for 4 days. Chronic food restriction didn't increase hi-fat ingestion but hi-fat-no-carb. Rats ingested less without habituation, and overnight food deprivation increased intake. This increment was maintained after rats were free-fed. The difference in fat content of the maintenance diet had little effect on fat preference. These results showed SD rats prefer a sweet and fatty liquid diet than a sweet and lean liquid diet. Habituation and food restriction were more important than the composition of the maintenance diet to demonstrate a clear preference for the fatty liquid diet.     

Biological Activity of a Phytotoxic Glycopeptide Produced by Corynebacterium sepedonicum

A purified toxic glycopeptide from Corynebacterium sepedonicum (Speick.) Dows., possesses the capacity to wilt plant cuttings. The toxin induces a rapid general flaccidity in stem tissues followed by a leaf wilt making its effects significantly different from that induced by high molecular weight substances (dextrans). In the latter case, the initial effect of a dextran induced wilt is a leaf wilt presumably caused by the plugging of xylem elements. However, physiological experiments including dye transport studies, plasmolytic studies, measurements on electrolytes, studies on the movement of ³H₂O through tomato cuttings, and toxin binding studies all strongly suggest that the primary effect of the toxin is to destroy the integrity of cellular membranes resulting in the net loss of water from the cell. Membrane damage in toxin treated plants was confirmed by electron microscopic observations. Evidence of damage were seen in chloroplasts, mitochondria, the plasma membrane, and the structural integrity of the cell wall. These effects appeared to be a direct cause and not a secondary result of the toxin as shown by autoradiographic studies using ³H-toxin.     

Purification and Properties of a Phytotoxic Polysaccharide Produced by Corynebacterium sepedonicum

A polysaccharide possessing a capacity to wilt plant cuttings has been isolated and purified from cultures of Corynebacterium sepedonicum. The molecular weight, based on the average of molecular weights determined by 3 physical methods, is 21,450. The empirical formula of the polysaccharide is C₄₈H₉₆O₄₈N. It is antigenic and the borate complex migrates in an electric field. It has an intrinsic viscosity of 0.125 and an S_20w of 0.76. A hydrolysate of the compound yields glucose, mannose, 2 unidentified reducing compounds and 1 unidentified non-reducing compound. The nitrogen in the toxin can be accounted for in 6 amino acids. Although the toxin is primarily polysaccharide it might more aptly be termed a glycopeptide.     

Isolation and Structure of Phytotoxic Compounds Produced by Phyllosticta sp.

In the course of phytopathological studies, it has been observed that phyllosticta sp. produces a toxic compound causing wilting and simultaneous dark coloration of the clover leaf. A toxin, herein refered to as phyllosinol (mp 76~77°C) was isolated in a crystalline state from the pure culture and it was proved to be the principal toxic metabolite of the fungus. Although the melting point of phyllosinol differed significantly from that reported for epoxydon (40~45°C), the structural evidence deduced from spectrometric and chemical methods indicates that phyllosinol is substantially identical with epoxydon even in stereo-isomeric considerations. In the red clover leaf test 10 ppm phyllosinol showed the wilting effect.     

Characteristics of Pseudomonas solanacearum

Summary: A collection of 185 isolates of Pseudomonas solanacearum has been classified into 4 biotypes according to their capacity to oxidize 3 disaccharides (lactose, maltose and cellobiose) and 3 hexose alcohols (mannitol, sorbitol and dulcitol). Biotype 2 which oxidized the disaccharides but not the hexose alcohols appears to have a restricted host range; it was obtained solely from two plant hosts, potato and tomato, whereas biotype 1, which oxidized neither group of carbohydrates, and biotype 3 which oxidized both, were obtained from a diversity of plant hosts. A bacteriophage isolated from material infected with biotype 2 showed a high degree of specificity for isolates of biotype 2. The present known distribution of the 4 biotypes is given and their relationship to host range is discussed. A neotype culture for Ps. solanacearum is proposed.     

Lipopolysaccharide of Pseudomonas solanacearum

A novel monoterpene, 2(E)-(4-methyl-3-pentenyl)butenedial (α-acaridial (1) for the trivial name), was isolated from the secretion of the acarid mite Tyrophagus perniciosus. The structure was clarified in the light of spectral data, and the geometry of the double bond in the butenedial moiety was assigned based on the γ-deshielding effect on a methylene and on an aldehyde group. Coupling the Grignard reagent (CH₃)₂C =CHCH₂CH₂MgBr to THP-OCH₂(C = O)CH₂CH₂O-THP, and dehydration and deprotection of the OH groups gave α-(E)- and α-(Z)-acaridiol, which were fully assigned byMS and NMR. Matching the spectral data of the synthetic alcohols with those of the alcohol derived from the natural product, or of natural acaridial with those of synthetic α-(E)- and α-(Z)-acaridial, corroborated beyond all doubt the structure of this new monoterpene dial.     

Phyllostine,a New Phytotoxic Compound Produced by Phyllosticta sp.

Ethionine-resistant mutants derived from Corynebacterium glutamicum KY 9276 (Thr^?) were found to accumulate l-methionine in culture media. One of the mutants, ER-107-4, which produced 250 μg/ml of l-methionine was subjected to further mutagenesis to obtain better l-methionine producers. l-Methionine production increased stepwise by successive endowing such markers as selenomethionine, 1,2,4-triazole, trifluoromethionine and methionine hydroxamate resistance. Thus, a mutant multi-resistant to ethionine, selenomethionine and methionine hydroxamate, ESLMR-724, produced 2 mg/ml of l-methionine in a medium containing 10% glucose.

Increase of l-methionine production was accompanied by increased levels and reduced repressibility of methionine-forming enzymes. The levels of methionine enzymes in ESLMR-724 increased to 2.5~4.2 fold of those in KY9276, In addition, homoserine-O-trans-acetylase and cystathionine γ-synthase which were strongly repressed by l-methionine in KY 9276 were stimulated by exogenous l-methionine in ESLMR-724. Implications of these results were discussed in relation to the productivity of l-methionine and the regulation of l-methionine biosynthesis.     

The Flagella of Pseudomonas solanacearum

Summary: Electron microscopic examination of 5 strains of Pseudomonas solanacearum , including the proposed neotype, NCPPB 325, showed that the cells of these organisms possess polar flagella.     

The lipopolysaccharides of Pseudomonas solanacearum i Pseudomonas cichorii

Structure analysis by the methods of methylation, 1H- and 13C-n. m. r. spectroscopy has shown that O-specific polysaccharides of typical strains of Pseudomonas solanacearum (biovar I) and P. cichorii are identical by their structure and constructed of branched pentasaccharide repeating links which include three residues of rhamnose (one of them is in the branching node), one residue of beta-xylose (it occupies terminal position) and one reside of N-acetyl-beta-glucosamine. The other strain of P. solanacearum of biovar I and two strains belonging to biovars III and IV also produce structure-similar O-specific polysaccharides, constructed of linear tetrasaccharide repeating links which include three residues of alpha-L-rhamnose and one residue of N-acetyl-alpha-D-glucosamine.     

Stress compounds in tobacco callus infiltrated by Pseudomonas solanacearum

Two sesquiterpenoids, phytuberin and phytuberol, have been identified in tobacco callus infiltrated by Pseudomonas solanacearum.     

Comparative Zone Electrophoresis of Enzymes of Pseudomonas solanacearum and Pseudomonas cepacia

The technique of starch-gel electrophoresis with specific staining for a series of enzymes was used to compare 21 Pseudomonas strains representing both P. cepacia and P. solanacearum. These experiments produced no evidence for close similarity of the two species. Twelve strains of P. solanacearum were compared by means of data obtained from nine different enzymes, and the data indicate that these strains belong in two biotypes. Except for the assignment of two strains, these groups are the same as the two major groups previously derived from nutritional properties and from deoxyribonucleic acid hybridization experiments. Eleven enzymes were available for comparisons of the P. cepacia strains. Eight of these strains form a homogeneous group, but the last strain, number 249, differs considerably from the other representatives of the species.     

Chemical Characterization of the Lipopolysaccharide of Pseudomonas solanacearum

The carbohydrates present in lipopolysaccharide (LPS) from Pseudomonas solanacearum are rhamnose, xylose, 2-amino-2-deoxyglucose, glucose, heptose, and 2-keto-3-deoxyoctonate. LPS extracted from cultures grown on either glycerol or glucose (as the major source of carbon) and extracted after various incubation periods had similar compositions. The LPS from several strains of the bacterium contained the same component sugars, but the amounts of each sugar varied considerably. It was observed, however, that xylose and 2-amino-2-deoxyglucose increased proportionately with rhamnose, the major component. Phenol-water-extracted LPS contained measurable amounts of nucleic acid, protein, and arabinan, but none of these polymers were detected in LPS extracted with phenol-chloroform-petroleum ether. Polysaccharides liberated from LPS by mild acid hydrolysis were purified by gel filtration. Carbohydrate analysis of the LPS from a virulent, fluidal strain (K60) showed that the O-specific antigen consisted of rhamnose, xylose, and 2-amino-2-deoxyglucose in the proportions 4:1:1. The LPS of an avirulent, afluidal strain (B1) lacked the O-specific antigen; the R-core region consisted of rhamnose, glucose, heptose, and 2-keto-3-deoxyoctonate. Methylation analysis indicated that the K60 O-specific antigen was composed of a hexasaccharide repeating unit containing 3-, 2-, and 3,4-substituted rhamnopyranosyl residues, 3-substituted 2-amino-2-deoxyglucose, and terminal xylopyranose in the molar ratios 2:1:1:1:1.     

Lipopolysaccharide-Defective Mutants of the Wilt Pathogen Pseudomonas solanacearum

Lipopolysaccharide (LPS)-defective mutants of Pseudomonas solanacearum were used to test the hypothesis that differences in LPS structure are associated with the ability or inability of different strains to induce a hypersensitive response (HR) in tobacco. To obtain these mutants, LPS-specific bacteriophage of P. solanacearum were isolated and used to select phage-resistant mutants of the virulent, non-HR-inducing strain K60. The LPS of 24 of these mutants was purified and compared with that of K60 and its HR-inducing variant, B1. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, LPS from K60 and other smooth strains separated into many evenly spaced bands that migrated slowly, whereas LPS from B1 and most phage-resistant strains separated into one to three bands that migrated rapidly. Carbohydrate analysis showed that the LPS of the phage-resistant strains lacked O-antigen sugars (rhamnose, xylose, and N-acetylglucosamine) and could be grouped into (i) those that had all core sugars (rhamnose, glucose, heptose, and 2-keto-3-deoxyoctonate), (ii) those that had no core rhamnose, and (iii) those that lacked all core sugars except for 2-keto-3-deoxyoctonate. The LPS composition of 10 of the rough, phage-resistant mutants was similar to that of the HR-inducing strain, B1, yet none of them induced the HR. Only 2 of 13 mutant strains tested caused wilting of tobacco, and these had rough LPS but produced large amounts of extracellular polysaccharide, unlike most LPS-defective mutants. The evidence did not support the hypothesis that the initial interaction between rough LPS and tobacco cell walls is the determining factor in HR initiation.     

Plasmid-encoded dissimilation of condensed tannin in Pseudomonas solanacearum

Pseudomonas solanacearum degrades catechin to phloroglucinolcarboxylic acid, protocatechuic acid, catechol, phloroglucinol, resorcinol and hydroxyquinol, which is plasmid-encoded. This dissimilatory plasmid, designated as pAMB1, was effectively cured by mitomycin C treatment and was transferred to a Pseudomonas sp., with a transfer frequency of 2.2 × 10⁻⁵ transconjugants/donor cell. The cured strains did not utilize catechin or its intermediates, and lacked the plasmid.     

Nigrosporins A and B,New Phytotoxic and Antibacterial Metabolites Produced by a Fungus Nigrospora oryzae

Nigrosporin A and B, two new phytotoxic and antibacterial metabolites were isolated from a culture filtrate of Nigrospora oryzae.

The active principles were absorbed on XAD-2 resin and purified by successive ODS-HPLC. The structures were identified by spectroscopic and derivatization analysis as naphthoquinone derivatives. The substances showed phytotoxic activities, such as root elongation inhibition, necrotic effects, oxygen evolution inhibition, starch synthesis inhibition, and CO₂ fixation inhibition at concentrations of 10–100 ppm. They also showed growth inhibition activity against Bacillus subtilis in a disc diffusion assay as well as when compared with streptomycin.     

Genetic diversity of Burkholderia solanacearum (synonym Pseudomonas solanacearum) race 3 in Kenya.

Genetic diversity among isolates of the bacterial plant pathogen Burkholderia solanacearum (synonym Pseudomonas solanacearum) race 3 biovar II of Kenya was determined by PCR with repetitive sequences (ERIC and BOX repetitive primer sets) and pulsed-field gel electrophoresis of genomic DNA digested by rare-cutting restriction endonucleases (RC-PFGE). The study comprised 46 isolates collected during 1992 from the major potato-growing regions of Kenya (45 were identified as race 3 biovar II, and 1 belonged to race 3 biovar N2) and 39 reference isolates from 19 other countries. RC-PFGE identified 10 distinct profile types among the Kenyan race 3 biovar II isolates (29 of the isolates exhibited identical profiles) and a further 27 distinct profile types among the reference isolates. ERIC and BOX primer sets were unable to differentiate race 3 biovar II isolates within the Kenyan population but differentiated a further two distinct profile types among the reference isolates. The race 3 biovar N2 isolate had a highly distinct RC-PFGE and repetitive sequence PCR profile. Statistical analysis of the data identified biogeographic trends consistent with conclusions drawn from previous studies on the origin and worldwide dissemination of race 3 biovar II isolates; however, genomic fingerprinting by RC-PFGE revealed a level of genetic diversity previously unrealized.     

Technique for the Determination of the Rate of Ethylene Production by Pseudomonas solanacearum

A tube culture system was designed for measurement of ethylene evolved by the phytopathogenic bacterium, Pseudomonas solanacearum. The system consisted of 10 glass tubes joined together in series and coated on the inside surface with a dextrose-peptone-casamino acids agar medium. The system provided a large surface for bacterial growth in relation to the volume of air. The system was seeded with a bacterial suspension (7 × 10⁸ cells/ml) drawn through all the tubes by vacuum applied at one end and was then placed in a water bath at 30 C. Air was pumped through the system at 3 ml/min; the outlet was connected directly to the inlet port of a gas sampling loop and ethylene in the sample was determined by gas chromatography.