Effects of Carrier and Temperature on Survival of Rhizobium spp. in Legume Inocula: Development of an Improved Type of Inoculant

The effects of inoculant carrier, temperature, and storage period on the survival of Rhizobium strains were determined by plate count and most-probable-number analyses. Preliminary experiments showed that survival of rhizobia was affected by each of these factors and their interactions. Results of further studies indicated that six strains of rhizobia survived better at high temperatures when lyophilized and suspended in an oil carrier as compared to finely ground peat. The oil base inocula contained ca. 10⁵ viable rhizobia per g after 56 days of incubation at 60°C, whereas peat base inocula contained ≤10 rhizobia per g. These results suggest that an oil carrier will protect rhizobia from rapid death at usually lethal high temperatures.     

Comparison of the Pour, Spread, and Drop Plate Methods for Enumeration of Rhizobium spp. in Inoculants Made from Presterilized Peat

Inoculants prepared with presterilized peat were enumerated by the pour, spread, and drop plate techniques. Results indicated that the three plating methods were interchangeable. The drop plate method was preferred because of its economy in materials and labor.     

Trypanosoma spp., Leishmania spp. and Leptomonas spp.: enzymes of ornithine-arginine metabolism

Eight species of trypanosomatid flagellates, Trypanosoma cruzi, T. mega, T. conorhini, Leishmania donovani, L. braziliensis, Leptomonas seymouri, L. collosoma, and L. samueli, were examined for the presence of enzymes of the arginine-ornithine metabolism. Arginase was found in species of the genera Leishmania and Leptomonas. Citrulline hydrolase was found only in species of Leptomonas. Trypanosoma spp. did not present any of the mentioned enzymes. Ornithine carbamoyltransferase and argininosuccinate lyase were found only in Leptomonas samueli, which also possessed arginine deiminase. With the sole exception of L. samueli the other species seem to present a uniform enzyme constitution, peculiar to their genera and different from the enzyme patterns of other genera of trypanosomatids already known. The potential usefulness of these findings for taxonomical purposes is discussed.     

Fingerprinting bacterial chromosomal DNA with restriction endonuclease EcoRI: comparison of Rhizobium spp. and identification of mutants.

Total cellular DNA from Rhizobium trifolii, R. melitoti, and R. japonicum strains 110 and 117 were prepared. DNA fragments generated with restriction endonuclease EcoRI from these DNA samples were compared in agarose gels after electrophoresis. DNA cleavage patterns generated from R. japonicum strain 110, R. trifolii, and R. meliloti were clearly distinguishable from each other. Restriction endonuclease cleavage patterns of DNA from R. japonicum strain 110 and presumptive R. trifolii mutant strains that nodulate soybean were found to be similar. Rhizobium trifolii mutant strains were also lysed by a phage specific for R. japonicum strain 110. These results show that "R. trifolii mutant strains" are indeed derivatives of R. japonicum strain 110 and not R. trifolii.     

Incidence of allergenic pollen of Acer spp., Fraxinus spp. and Platanus spp. in the city of La Plata, Argentina: preliminary results

This work studies the airborne pollenconcentrations of Acer spp.,Fraxinus spp. and Platanus spp. sincethe pollen of these three taxa has beencharacterized as etiological agents ofpollinosis. These tree species are present inlarge amounts in the streets of La Plata city.The aeropalynological monitoring was performedwith a Hirst-type spore trap (Lanzoni VPPS,2000). The emission period of the three taxaextends from approximately late August to October.The maximum cumulative totalof arboreal pollen was found to be 30824.7from September 12 to 18. This period coincideswith the peak of total pollen concentration.Pollen grains trapped were analysed andexpressed as daily averages of 5-hour bandsper day during the whole year. Maximum pollenconcentration was registered between 10 a.m.and 2 p.m. During the studied period, 67 patients examinedat the Allergy Service of ``Hospital Interzonalde Agudos R. Rossi' (La Plata) showed allergicdisease. These allergenic episodes may beproduced by the large amount of pollen trees inthe city area.     

Structural characterization of the K antigens from Rhizobium fredii USDA257: evidence for a common structural motif, with strain-specific variation, in the capsular polysaccharides of Rhizobium spp.

Rhizobium fredii participates in a nitrogen-fixing symbiosis with soybeans, in a strain-cultivar-specific interaction, and past studies have shown that the cell surface and extracellular polysaccharides of rhizobia function in the infection process that leads to symbiosis. The structural analysis of the capsular polysaccharides (K antigens) from strain USDA257 was performed in this study. The K antigens were extracted from cultured cells with hot phenol-water and purified by size exclusion chromatography. We isolated two structurally distinct K antigens, both containing a high proportion of 3-deoxy-D-manno-2-octulosonic acid (Kdo). The polysaccharides were characterized by matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry, nuclear magnetic resonance spectrometry, and gas chromatography-mass spectrometry analyses. The primary polysaccharide, which constituted about 60% of the K-antigen preparation, consisted of repeating units of mannose (Man) and Kdo, [-->)3-beta-D-Manp-(1-->5)-beta-D-Kdop-(2-->], and a second polysaccharide consisted of 2-O-MeMan and Kdo, [-->)3-beta-D-2-O-MeManp-(1-->5)-beta-D-Kdop-(2-->]. These structures are similar to yet distinct from those of other strains of R. fredii and R. meliloti, and this finding provides further evidence that the K antigens of rhizobia are strain-specific antigens which are produced within a conserved motif.     

Avian wildlife reservoir of Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. in Norway

Cloacal swabs from 540 wild-living birds were cultured for Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. The carrier rates detected were as follows: C. fetus subsp. jejuni, 28.4%; Yersinia spp., 1.2%; and Salmonella spp., 0.8%. All birds were apparently healthy when captured. C. fetus subsp. jejuni was isolated from 11 of the 40 bird species examined. Among birds inhabiting the city of Oslo, the highest isolation rate was found in crows (Corvus corone cornix) (89.8%), followed by gulls (Larus spp.) (50.0%) and domestic pigeons (Columba livia domesticus) (4.2%). The gulls and crows scavenge on refuse dumps. High carrier rates were also detected among the following birds from nonurban, coastal areas: puffin (Fratercula arctica) (51.3%), common tern (Sterna hirundo) (5.6%), common gull (Larus canus) (18.9%), black-headed gull (Larus ridibundus) (13.2%), and herring gull (Larus argentatus) (4.2%). The list of species harboring C. fetus subsp. jejuni also includes the Ural owl (Strix uralensis), goldeneye (Bucephala clangula), and reed bunting (Emberiza schoeniclus). The following five Yersinia strains were isolated: Y. kristensenii (two strains), Y. intermedia (two strains), and "Yersinia X2" (one strain). Four strains belonging to the genus Salmonella were isolated from three different species of gulls. These isolates were identified as S. typhimurium, S. indiana, and S. djugu. The results indicate that campylobacters are a normal component of the intestinal flora in several bird species, whereas Salmonella and Yersinia carriers are more sporadic.     

The Effects of Plant Growth Substances and Mixed Cultures on Growth and Metabolite Production of Green Algae Chlorella sp.: A Review

Recent interest in the use of microalgae for the production of biofuels and bioproducts has stimulated an interest in methods to enhance the growth rate of microalgae. This review examines past work involving the stimulation of Chlorella sp. growth and metabolite production by plant growth substances as well as by mixed cultures of Chlorella sp. with bacteria. Plant growth substances known to regulate Chlorella sp. growth and metabolite production include auxins, cytokinins, abscisic acid, polyamines, brassinosteroids, jasmonic acid, salicylic acid, and combinations of two or three of the aforementioned substances. Mixed cultures of bacteria are examined, including both natural bacteria–algae consortia and artificially induced symbioses. For natural consortia, commonly occurring bacterial species, including the genera Brevundimonas and Sphingomonas, are discussed. For artificially induced symbioses, the use of the nitrogen-fixing bacterium Azospirillum is examined in detail. In particular, a variety of studies have involved the coimmobilization of Chlorella sp. with Azospirillum sp. in alginate beads, with the goal of using the mixed culture to treat wastewater. In summary, the use of plant growth substances and mixed cultures provides two methods to increase the growth of Chlorella sp., whether for the production of lipids for biofuels, the production of bioproducts, the treatment of wastewater, or a variety of other reasons.     

Studies on the Production of Digitalis Cardenolides by Plant Tissue Culture III. Effects of Nutrients on Digitoxin Formation by Shoot-Forming Cultures of Digitalis purpurea L. Grown in Liquid Media

Shoot-forming cultures of Digitalis purpurea L. were grown invarious modifications of Murashige-Skoog medium. The effectsof vitamins, natural extracts, plant growth substances, carbonand nitrogen sources and phosphate on their growth and digitoxinformation were investigated. Sucrose, glucose and raffinosewere suitable carbon sources for both growth and digitoxin formation.The optimum concentration of sucrose was 3%. Reduction of thebasal nitrogen concentration by one-third increased the digitoxincontent per unit weight without suppression of growth. The optimalratio of nitrate-nitrogen to ammonium-nitrogen was 2, as providedin the basal medium. A threefold increase in the phosphate concentrationimproved both growth and digitoxin content. Thiamine.HCl andmyo-inositol were required for digitoxin formation, whereasglycine, nicotinic acid and pyridoxine.HCl, usual componentsof the medium, were not required for either growth or digitoxinformation during the three passages examined. Coconut milk improvedgrowth with no reduction in the digitoxin content per unit weight.Gibberellic and abscisic acids at 0.01 to 0.1 mg per liter slightlyimproved digitoxin formation. Kinetin had no clear positiveeffect on either growth or digitoxin formation. (Received March 12, 1982; Accepted August 5, 1982)     

Trichothecene Production in Liquid Stationary Cultures of Fusarium tricinctum NRRL 3299 (Synonym: F. sporotrichioides): Comparison of Quantitative Brine Shrimp Assay with Physicochemical Analysis

Stationary liquid cultures of Fusarium tricinctum NRRL 3299 (synonym: F. sporotrichioides) produce T-2 toxin, neosolaniol, diacetoxyscirpenol, and HT-2 toxin when cultured on peptone-enriched Czapek Dox medium. At 15 and 27°C, maximum T-2 toxin yield (265 and 50 μg/ml) was found after 10 to 14 and 7 days, respectively. The T-2 toxin in the culture medium was metabolized rapidly at 27°C and slowly at 15°C. Addition of 0.025% (wt/vol) sorbic acid to the medium resulted in an increased production of trichothecenes at 15°C (400 μg of T-2 per ml after 14 days). Trichothecenes in the culture liquid were determined by the brine shrimp bioassay and physicochemical analysis. The brine shrimp assay was improved by using modern bioassay equipment, including tissue culture trays and multipipettes, and by a standardized approach with positive and negative controls. The physicochemical analysis was based on adsorption of the trichothecenes onto Amberlite XAD-2 columns, derivatization with trifluoroacetic anhydride followed by capillary gas chromatography, and identification by mass spectrometry (as many as 17 trichothecenes were detected in the culture medium). The brine shrimp assay offers an interesting monitoring system for the quantitation of T-2 toxin and should be useful for studies on production of this toxin in culture. Specific information on less toxic trichothecenes, however, requires a more time-consuming chemical analysis.