摘要:

This review presents a critical and comprehensive analysis of the developments in environmental and physiological studies related toAzospirilluminteractions with plants based on information published between 1990 and 1996. It was designed as an update of a previous review with a similar scope. Apart from an update, this review emphasizes the central issues ofAzospirillumresearch today, such as coinoculation with other microorganisms and hormonal studies, shows the less researched areas, and proposes possible avenues for the exploitation of this bacterium in areas other than agriculture.Key words:Azospirillum, bacterial inoculation, plant–bacteria interaction, plant growth promoting rhizobacteria, rhizosphere bacteria.

ISSN:0008-4166    

DOI:10.1139/m97-015

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Lipopeptides are antifungal agents that inhibit cell wall β-(1, 3)-glucan biosynthesis in fungal organisms. A mutant resistant to lipopeptides was generated by UV mutagenesis and characterized. TheCandida albicansmutant (LP3-1) was stable and showed resistance specificity to a broad range of lipopeptides and certain glycolipid inhibitors. Other antifungal agents with diverse modes of action had a normal minimum inhibitory concentration profile for LP3-1 compared with the wild-type strain (CCH 442). In the in vitro β-(1, 3)-glucan synthase assay, both the lipopeptides and papulacandin-related agents had considerably higher 50% inhibitory concentration values in the LP3-1 strain than in the wild-type strain. In reconstitution assays, the resistance factor was associated with the integral membrane pellet rather than the peripheral GTP-binding protein. The LP3-1 strain had a membrane lipid profile similar to that of the parent strain and was virulent in a murine model of systemic candidiasis. Taken together, these results indicate that the resistance factor is associated with the integral membrane component of β-(1, 3)-glucan synthase. Lipopeptides are common antifungal agents encountered during screening of natural products. The LP3-1 strain was resistant to natural product extracts known to contain various lipopeptides. Thus, LP3-1 can be used in a dereplication assay.Key words:Candida albicans, β-(1, 3)-glucan synthase, lipopeptides, drug resistance.

ISSN:0008-4166    

DOI:10.1139/m97-016

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

An endospore-forming rod-shaped filamentous bacterium was taken from boiled intestines of common sow bugs (Porcellio scaber, isopod crustaceans). The bacteria were grown on peptone – yeast extract medium. As many as 180 cells per filament were counted in culture; filament length was a function of time after germination and oxic conditions. Cultures continued to grow filamentously after 10 successive transfers. The development of spores was inhibited by strict anaerobiosis for 3 months. Spore-forming filaments over 100 μm long in fresh intestinal material were observed only in guts taken from sow bugs cultivated in darkness. Phenotypic tests presented here show this isolate to be a member of the genusBacillus, most closely resemblingB.cereus.Key words:Arthromitus, motile bacilli, isopod, sow bug, intestinal filaments.

ISSN:0008-4166    

DOI:10.1139/m97-017

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Fungal fimbriae are long (0.5–20 μm), narrow (7 nm) surface appendages that have been observed on most members of the Mycota. Biochemical analyses have determined that fimbriae fromMicrobotryum violaceumare composed of 74-kDa glycoproteinaceous subunits in which the protein moiety is fungal collagen. We present evidence for the localization of fimbrial subunits prior to their exportation from the cell. We term these internal, likely nonpolymerized fimbriae "pro-fimbriae" and demonstrate the location of the reserves within the peripheral cytoplasm. Also, we show that fimbriae may not traverse the cell wall as previously believed, but may instead originate from within the outer lamella of the cell wall, possibly being anchored to the cell wall via other molecules. This model is analogous to the animal extracellular matrix arrangement in which collagens are anchored to plasma membranes via other proteins such as fibronectin.Key words: fungus, immunolocalization, fimbriae,Microbotryum,Ustilago.

ISSN:0008-4166    

DOI:10.1139/m97-018

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Acid-adaptive responses could be induced readily in oral lactic-acid bacteria by growing them in batch cultures with excess sugar or more conveniently and rapidly by transferring cells to acidified growth media for the time required for biomass doubling. The response ofStreptococcus mutansGS-5 was induced in a progressive rather than all-or-nothing way, and the extent of acid tolerance was inversely related to the pH of the inducing medium over a range from 8.5 to 5. The weak acids fluoride, acetate, or lactate did not measurably enhance acid adaptation, and so the response did not appear to depend primarily on changes in ΔpH or the proton motive force across the cell membrane. Transcription and translation to form new proteins did appear to be necessary, as indicated by inhibition of adaptation by rifampin or chloramphenicol and by lack of adaptation by cells suspended in phosphate buffer at pH 5.Streptococcus salivariusandLactobacillus caseiwere acid adapted by the rapid method, and the method appeared to be generally useful for oral lactic-acid bacteria. The rapid induction of the response in multiple oral lactic-acid bacteria suggests that it is of general importance for maintaining a diversity of organisms in the oral microbiota, which is regularly subjected to acid stresses.Key words: acid adaptation, oral lactic-acid bacteria,Streptococcus mutans.

ISSN:0008-4166    

DOI:10.1139/m97-019

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Three different exopolymers were purified from cultures ofAgrobacteriumsp. strain ATCC 31749 grown in a mineral salts medium containing 2% glucose at 30 °C for 5 days under aerobic culture conditions. These exopolymers were curdlan (extracellular, homo-β-(1-3)-glucan, water insoluble at neutral pH), a water-soluble noncurdlan-type exopolymer A (WSNCE-A), and a water-soluble noncurdlan-type exopolymer B (WSNCE-B). Curdlan, WSNCE-A, and WSNCE-B composed by weight 61, 27, and 12%, respectively, of the exopolymer produced from glucose. Compositions of all polymers were confirmed by gas chromatography (GC) and gas chromatography – mass spectrometry (GC–MS). The WSNCE-A is composed of glucose and galactose with lower contents of rhamnose. The WSNCE-B consists of glucose and mannose. To biosynthesize modified biopolymers, glucose-related sugars including 3-O-methyl-D-glucose, 2-amino-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine) were fed separately as the sole carbon source. Using 3-O-methyl-D-glucose, 8 – 12 mol% of the curdlan repeats were 3-O-methyl-D-glucose based on GC and1H-nuclear magnetic resonance spectrometry.N-Acetylglucosamine was incorporated into WSNCE-A at 10 mol% based on the GC–MS but was not found in curdlan or WSNCE-B.Key words:Agrobacteriumsp., curdlan, exopolymer, 3-O-methyl-D-glucose, 2-acetamido-2-deoxy-D-glucose.

ISSN:0008-4166    

DOI:10.1139/m97-020

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A polymerase chain reaction (PCR) method was developed for the rapid detection of the beer-spoilage heterofermentative lactic acid bacteriumLactobacillus lindneri. Three strains, the Chinese brewery isolate DA1, the Japanese commercial beer isolate BG2, and the Japanese brewery isolate SE3, which were serologically classified as belonging toL.lindneri, were used in this study. After sequencing the 16S rDNA of the isolates DA1 and BG2 and the typical beer-spoilage heterofermentativeLactobacillus brevisL63, these sequences were compared with published data. AL.lindnerispecific PCR primer, DA-40, was then constructed based on the V1 variable region of 16S rDNA. The specificity of PCR using theL.lindnerispecific primer DA-40 and the universal primer 907r was examined using fiveL.lindneristrains: the three isolates described above and two strains from culture collection, DSM 20690 and DSM 20692. A variety of beer-spoilage lactic acid bacteria, including 71Lactobacillusstrains and 13Pediococcusstrains, were also included in this examination. No PCR product was obtained from any DNA with the exception of the fiveL.lindneristrains, indicating that theL.lindnerispecific primer DA-40 was highly specific. The detection limit forL.lindneriin beer was 63 CFU/100 mL of beer.Key words:Lactobacillus lindneri, oligonucleotide probe, sequence analysis, 16S rDNA.

ISSN:0008-4166    

DOI:10.1139/m97-021

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A hundred strains of non-nodulating, Gram-negative, rod-shaped bacteria were isolated from clover–ryegrass pastures on three different soil types and from a sandy loam under lupins. When crossed withEscherichia coliPN200 containing the cointegrate plasmid pPN1, 11 transconjugants gained the ability to form nodules on the roots of white clover (Trifolium repenscv. Grasslands Huia). AnodAprobe indicated that they had gained nodulation genes. The identities of these 11 strains and 4 others derived from earlier work on non-nodulating root nodule bacteria, were determined by ribotyping, DNA – DNA hybridization, and partial 16S rRNA sequencing. Good agreement was obtained between the three methods, and 11 of the strains were identified asRhizobium leguminosarum(6),Rhizobium loti(2),Rhizobium etli(1),Rhizobium tropici(1), andSinorhizobium meliloti(1). DNA –DNA hybridization indicated that the remaining four strains were related to theRhizobium leguminosarumreference strains. The existence of several species of non-nodulating rhizobia in pasture soil, including species for which the normal host plant was absent, is discussed in relation to the fate of symbiotic plasmids fromRhizobiumseed inoculants. It is also suggested that new species should be named for the geographical region from which they are first isolated rather than the host plant.Key words:Rhizobium, non-nodulating, nonsymbiotic, isolation, identification.

ISSN:0008-4166    

DOI:10.1139/m97-022

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Selected polished thin sections were used as model substrata to investigate the influence of geochemical and electrochemical factors on bacterial colonization and weathering of mixed sulfide minerals. Naturally occurring sulfide assemblages including combinations of pyrite, chalcopyrite, sphalerite, galena, and pyrrhotite were studied. The distribution ofThiobacillus ferrooxidanswas mapped using viable negative and positive staining techniques in combination with scanning confocal laser microscopy. The minerals were characterized using scanning electron microscopy and microprobe analyses. Inter- and intra-granular electrode potentials were monitored using microelectrodes. Results of the experiments indicated that theT.ferrooxidansstrain preferentially colonized sulfide minerals that were the most electrochemically active. For example, when pyrite, chalcopyrite, and pyrrhotite were in combination, bacteria preferentially colonized the pyrrhotite. In each case it was shown that the mineral colonized was also the anode in a galvanic cell and the site of preferential weathering. Microelectrode measurements confirmed the existence of intergranular potentials. In addition, trace and minor element composition appeared to influence the electrochemical property of the mineral, thus its colonization and weathering pattern. Information of this nature should facilitate prediction of the fate of sulfide minerals in natural and mining environments.Key words: image analysis, confocal microscopy, sulfide minerals, microelectrodes, electrode potential.

ISSN:0008-4166    

DOI:10.1139/m97-023

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Ammonium ions and alanine influence production of the macrolide avermectin inStreptomyces avermitilis.L-Alanine dehydrogenase and alanine aminotransferase are the primary enzymes responsible for regulating the intracellular concentration of alanine and also of ammonium ions. In cultures ofS.avermitilisin a chemically defined medium with ammonia orL-alanine as the only nitrogen source, specific activities of both enzymes increased during growth. The alanine dehydrogenase specific activity increased more than 86-fold after the culture was supplemented with 0.2%L-alanine and 5-fold after addition of 0.5% ammonium sulfate, whereas alanine aminotransferase specific activity increased 3- to 4-fold with either substrate. Five isoenzymes of alanine dehydrogenase were detected histochemically inS.avermitilisafter native gel electrophoresis. Isoenzyme 1 was induced by alanine and temporarily repressed by high concentrations of ammonium sulfate. The presence of isoenzyme 1 was also related to changes in the kinetic properties of the alanine dehydrogenase reaction measured in crude desalted extracts. A nonlinear double-reciprocal plot was obtained in initial velocity studies usingL-alanine as a substrate in the sample induced withL-alanine. The nonlinearity was caused by both substrate inhibition and allosteric regulation (positive cooperativity) byL-alanine. In contrast, the sample induced by ammonium sulfate showed a linear double-reciprocal plot.Key words: isoenzymes,L-alanine dehydrogenase,Streptomyces avermitilis, avermectin.

ISSN:0008-4166    

DOI:10.1139/m97-024

出版商:NRC Research Press    

年代:1997

数据来源: NRC