摘要:

Tributyltin (TBT) resistance of aerobic and anaerobic bacteria isolated from TBT-contaminated coastal sediments in Arcachon Bay, France, was determined and compared with taxonomically similar bacteria originating from diverse non-TBT-contaminated environments. The minimum inhibitory concentrations (MICs) showed that TBT was toxic to most of the bacteria studied at concentrations above 2.1 μM (0.7 mg/L) for clostridia, 76 μM (25 mg/L) for pseudomonads, and 3 mM (1000 mg/L) for enterobacteria. The aerobic or facultative anaerobic Gram-negative bacteria (pseudomonads and enterobacteria) presented the highest TBT tolerance. No difference in TBT resistance was observed between strains originating from the polluted site and strains originating from non-TBT-polluted environments (thermal muds, Hospital of Bordeaux, etc.), suggesting that a TBT-polluted environment did not select for more specific resistant bacteria. It should be noted that the bacteria tested were found to be tolerant to TBT concentrations 1000 times higher than those found in the polluted site. Further, all strains presented the same pattern of metal and pharmaceutical antibiotic sensitivity despite the origin of the environment (TBT-polluted or non-TBT-polluted sediments). Six strains ofPseudomonas stutzeriisolated from Arcachon Harbor and one strain ofPseudomonas aeruginosaoriginating from the bacterial collection of Bordeaux Hospital have been selected for their TBT resistance. As antibiotic resistance, metal or organometal resistance can be plasmid mediated. However, among these TBT-resistant strains no plasmid was detected.Key words: TBT resistance, coastal environment, clostridia, pseudomonads, enterobacteria.

ISSN:0008-4166    

DOI:10.1139/m96-071

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A biocontrol rhizobacterial strain ofBacillus subtilisAF 1 grown for 6 h was coinoculated withAspergillus nigerat different time intervals and microscopic observations revealed adherence of bacterial cells to the fungal mycelium. Bacterial cells multiplied in situ and colonized the mycelial surface. Growth of AF 1 resulted in damage to the cell wall, followed by lysis. AF 1 inoculation into media containingA.nigerat 0, 6, and 12 h suppressed >90% fungal growth, while in 18- and 24-h cultures fungal growth inhibition was 70 and 56%, respectively, in terms of dry weight. In dual culture the fungal growth was not accompanied by formation of spores. The mycelial preparation ofA.nigeras principal carbon source supported the growth ofB.subtilis, as much as chitin. Extracellular protein precipitate fromB.subtilisculture filtrate had a significant growth-retarding effect onA.niger. Groundnut seeds bacterized withB.subtilisshowed a reduced incidence of crown rot inA.nigerinfested soil, suggesting a possible role ofB.subtilisin biological control ofA.niger.Key words: mycolytic bacteria,Bacillus subtilis,Aspergillus niger, biological control.

ISSN:0008-4166    

DOI:10.1139/m96-072

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Flocculation onset, the time during the fermentative cycle at which the strains ofSaccharomyces cerevisiaebecome flocculent, is an important factor in the brewing industry. The flocculation ability of Flo1 phenotype (strain NCYC 869) remained practically unchanged throughout the growth and seems to be insensitive to the presence of nutrients of the culture medium. On the contrary, the flocculation of NewFlo phenotype (strain NCYC 1195) exhibited a cyclic behaviour. It was found that the loss of flocculation in the early growth was the result of two combined effects: the dismantling of the flocculation mechanism of the cells coming from the inoculum and the nonflocculent state of the new cells produced after growth has started. The onset of flocculation of strain NCYC 1195 in the cultural conditions used in this work coincided with the end of the exponential growth, when the minimum glucose level in the culture medium was attained. It was demonstrated that it is possible to manipulate the flocculation onset by changing the initial glucose concentration in the culture medium.Key words: yeast, flocculation inhibition, glucose limitation, flocculation onset, genealogical age.

ISSN:0008-4166    

DOI:10.1139/m96-073

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The surface chemical composition, the physicochemical properties, and the adhesiveness ofAzospirillum brasilensehave been investigated during growth in Luria–Bertani* rich medium. The surface elemental composition obtained by X-ray photoelectron spectroscopy was converted into a molecular composition in terms of model constituents: proteins, polysaccharides, and hydrocarbon-like compounds. The protein content increased during growth, from 30 (exponential phase cells) to 50% (stationary phase cells), concomitantly with a decrease in the polysaccharide content, from 60 to 35%. These modifications were related to a change in cell surface hydrophobicity, i.e., to an increase of the water contact angle from 20 to 60°. No difference of electrophoretic mobility was detected between cells harvested in the exponential phase and cells harvested in the stationary phase. The increase of both cell surface protein concentration and cell surface hydrophobicity during growth was correlated with an increase of cell adhesiveness to model supports. This points to the involvement of cell surface proteins and cell surface hydrophobicity in the adhesion process.Key words:Azospirillum brasilense, surface composition, hydrophobicity, adhesiveness, X-ray photoelectron spectroscopy.

ISSN:0008-4166    

DOI:10.1139/m96-074

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Secreted endo-(1,4)-β-glucanases ("cellulases") ofAchlya ambisexualiswere analyzed by a technique that permits visualization of enzyme activity in situ after electrophoresis in gels containing sodium dodecyl sulfate. Catalytic polypeptides with molecular masses of about 97, 74, 36, 29, and 25 kDa were observed in media from young cultures, though progressively fewer bands were observed as cultures aged. Based on size estimations of native enzymes with gel exclusion chromatography, the 97- and 36-kDa polypeptides were concluded to be subunits of a 245-kDa holoenzyme and the 25-kDa polypeptides were concluded to be subunits of a second holoenzyme of about 92 kDa. The data were insufficient to allow similar assignments for the more ephemeral 74- and 29-kDa polypeptides. The endoglucanases secreted during branch induction by antheridiol or 0.2% peptone comigrated in electrophoretic gels with enzymes secreted during normal assimilative growth. No endoglucanases specific to induced branching were observed.Key words: oomycetes, cell walls, endoglucanases, cellulases, antheridiol.

ISSN:0008-4166    

DOI:10.1139/m96-075

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

InStreptomyces ambofaciensATCC23877, 0.7% of pigment-defective mutants (Pig−) can be observed in the progeny of wild-type colonies. A mutator (Mut−) strain was isolated from the offspring of the wild-type strain. The Mut−strain produced colonies that sported nonpigmented papillae. Furthermore, the frequency of Pig−colonies obtained in the progeny of this strain was fivefold higher than in the wild-type strain. This strain showed the same level of sensitivity to ultraviolet light and mitomycin C as the wild-type strain. This Mut−phenotype was found to be reversible at high frequency (3 × 10−3). Genomic analysis using pulsed-field gel electrophoresis (PFGE) showed that the Pig−mutants arisen from the Mut−strain were less frequently rearranged (32% were deleted) compared with the mutants arising from the wild type (59% were deleted). Moreover, the Pig−papillae mutants possessed no visible rearrangement as revealed by PFGE analyses.Key words:Streptomyces, genetic instability, mutator strain, papillae.

ISSN:0008-4166    

DOI:10.1139/m96-076

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Sixty-three bacterial isolates from antarctic sandstone samples (Linnaeus Terrace, Asgard Range, McMurdo Dry Valleys) were screened for the presence of plasmid DNA. Twenty-seven percent of all the isolates (mainly Gram-positives) harbored one or more plasmids of low molecular mass (1.1–16.3 kb). Strain AA-341 contained plasmid pAA-1 (2.9 kb), as demonstrated by agarose gel electrophoresis and restriction endonuclease digests. This plasmid conferred resistance to chromium and ampicillin. It was not conjugative, but it could be transferred by electroporation to chromium- and ampicillin-sensitive strains AA-330, AA-338, andE.coliHB101. A restriction map of pAA-1 was constructed withHindIII,SalI,ScaI,AvaII,EcoRI,PvuII,BamHI, andDraI. Electrotransfer of this plasmid fromE.coliHB101(pAA-1) to strain AA-330 was demonstrated. By natural genetic transformation, plasmid pAA-1 could be transferred into the sensitive strain AA-334, which thereby became resistant to chromium and ampicillin. The importance of such processes for the colonization of stressed environments is discussed.Key words: Antarctica, cryptoendolithic bacteria, plasmids, resistance to chromium, natural transformation.

ISSN:0008-4166    

DOI:10.1139/m96-077

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The heat-shock response of five strains of the entomopathogenic fungusBeauveria brongniartiiwas studied using two-dimensional (2D) gel electrophoresis. The fungal cells were heat shocked at 45 °C for 1 h and the total cellular protein was subjected to 2D gel electrophoresis. Proteins were separated in the first dimension using isoelectric focusing (pH range of 3.0–10) and in the second dimension by sodium dodecyl sulphate – polyacrylamide gel electrophoresis. More than 150 polypeptides for each strain were visualized by silver staining and have been assigned individual numbers as polypeptide coordinates. Analysis of the polypeptide map obtained by 2D gels indicated three patterns; several unique heat-shock proteins (HSPs) were (i) induced, (ii) enhanced, or (iii) repressed. Some of the HSPs induced by 45 °C were unique for each of the strains tested. Identification of heat-inducible protein synthesis or repression has ramifications for field survival and performance of entomopathogenic fungi. As well, the HSPs can be used as "signature proteins" for identification pruposes and this raises the possibility of using HSPs as a diagnostic tool applicable to other pest control fungi.Key words: heat-shock proteins, heat-shock response, two-dimensional electrophoresis, entomopathogenic fungi,Beauveria brongniartii.

ISSN:0008-4166    

DOI:10.1139/m96-078

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

An epiphytic strain ofErwinia herbicola(strain 299R) synthesized indole-3-acetic acid (IAA) from indole-3-pyruvic acid and indole-3-acetaldehyde, but not from indole-3-acetamide and other intermediates of various IAA biosynthetic pathways in enzyme assays. TLC, HPLC, and GC–MS analyses revealed the presence of indole-3-pyruvic acid, indole-3-ethanol, and IAA in culture supernatants of strain 299R. Indole-3-acetaldehyde was detected in enzyme assays. Furthermore, strain 299R genomic DNA shared no homology with theiaaMandiaaHgenes fromPseudomonas syringaepv.savastanoi, even in Southern hybridizations performed under low-stringency conditions. These observations strongly suggest that unlike gall-forming bacteria which can synthesize IAA by indole-3-acetamide, the indole-3-pyruvic acid pathway is the primary route for IAA biosynthesis in this plant-associated strain. IAA synthesis in tryptophan-supplemented cultures of strain 299R was over 10-fold higher under nitrogen-limiting conditions, indicating a possible role for IAA production by bacterial epiphytes in the acquisition of nutrients during growth in their natural habitat.Key words: indole-3-acetic acid,Erwinia, tryptophan, indole-3-pyruvic acid, nitrogen.

ISSN:0008-4166    

DOI:10.1139/m96-079

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Heavy metal pollution is a principle source of environmental contamination. We analyzed heavy metal impacted soil microbial communities and found that, in general, although lead adversely affected biomass, metabolic activity, and diversity, autochthonous lead- and cadmium-resistant isolates were found. In several metal-stressed soils, the microbial community consisted of two populations, either resistant or sensitive to lead. Additionally, a lead-resistant isolate was isolated from a control soil with no known previous exposure to lead, suggesting widespread lead resistance. Lead-resistant genera isolated includedPseudomonas,Bacillus,Corynebacterium, andEnterobacterspecies. Plasmids, ranging from 5 to 260 kb, were not detected through standard purifications from lead-resistant isolates. Positive correlations existed between antibiotic resistance and isolation habitat for lead-resistant strains, microbial metabolic activity and soil type, soluble lead concentration and microbial diversity, and arsenic concentration and total or viable cell concentrations.Key words: heavy metal, lead, cadmium, soil bacteria, stress, remediation.

ISSN:0008-4166    

DOI:10.1139/m96-080

出版商:NRC Research Press    

年代:1996

数据来源: NRC