摘要:

A total of 99 Gram-positive aerobic endospore-forming halotolerant rods were isolated from different hypersaline sources in Spain (salterns as well as saline soils). They were characterized taxonomically for a total of 178 features, including the utilization of 95 different substrates determined by the Biolog microbial identification system. These results were analysed by numerical techniques using the Jaccard (SJ) coefficient and clustering was achieved using the unweighted pair group method with averages algorithm. At 60% similarity level, the majority of the isolates were clustered in seven phenons. The guanine plus cytosine (G + C) content of some representative strains selected from each phenon ranged from 36.0 to 50.4 mol%. The isolates were identified as members of the genusBacillus, and were assigned to the speciesB. pantothenticus,B. firmus,B. alcalophilus,B. megaterium, andB. laterosporus. They were extremely halotolerant, most were able to grow in media with up to 20 or 25% salt. The diversity of groups and characteristics of the halotolerantBacillusisolated in this study indicate that they may play an important ecological role and contribute to the microbial diversity of hypersaline environments.Key words: halotolerant bacteria,Bacillus, taxonomy, hypersaline environments.

ISSN:0008-4166    

DOI:10.1139/w97-125

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A collection of 983Aeromonasisolates from environmental and clinical sources have been identified to the genomospecies level. A phenotypic method identified 93% of the strains. The use of citrate and the production of acid from sorbitol enabled the members of theAeromonas hydrophilacomplex to be separated. The most common genomospecies from intestinal sources wereAeromonas veroniibiotypesobriaandAeromonas caviae. The former, together withA. hydrophila,was the most frequently isolated species of extraintestinal origin. Most pathogenic species were very prevalent in environmental samples, withA. veroniibiotypesobriabeing the most common in lakes and reservoirs (41.5%) and in treated drinking water (25.0%), andA. caviaewas the most common in sea water (26.0%) and milk products (35.5%).Aeromonas hydrophila(18.1%) was the second most prevalent species isolated in untreated drinking water. SinceAeromonasinfections are generally regarded as a water- and food-borne diseases, the high environmental prevalence of these pathogenic genomospecies should be regarded as an important threat to public health.Key words:Aeromonas, food, water, clinical, Spain.

ISSN:0008-4166    

DOI:10.1139/w97-135

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Miso, a widely used Japanese fermented food was analysed for its lactic acid bacterial count on bromocresol purple agar. The binding of eight different foodborne carcinogenic heterocyclic amines to 25 bacterial isolates from miso were investigated. The heterocyclic amines used were 3-amino-1,4-dimethyl[5H]pyrido(4,3-b)indole (Trp-P-1), 3-amino-1-methyl[5H]pyrido(4,3-b)indole (Trp-P-2), 2-amino-6-methyldipyrido(1,2-a:3'2'-d)imidazole (Glu-P-1), 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), 2-amino-dimethylimidazo(4,5f)quinoline (IQ), 2-amino-3,4-dimethylimidazo(4,5-f) quinoline (MeIQ), 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx), and 2-amino-3-methyl-9H-pyrido(2,3)indole (MeA&agr;C). The lyophilized cells of all of the isolates exhibited high binding activity towards Trp-P-1, Trp-P-2, MeA&agr;C, and PhIP, while Glu-P-1 and IQ were not effectively bound. Of the isolates tested, the strongest and weakest binders were identified asPediococcus acidilactici1 and 2, respectively. Lyophilized cell wall fractions, heat-treated cells, and the cytoplasmic contents ofP. acidilactici1 and 2 were analysed for their ability to bind to different mutagens. Pure cell wall and peptidoglycan showed greater binding activity than the bacterial cells. Cytoplasmic content also showed some binding, but it was much less effective. The impact of enzymes (amylase, protease, cellulase, chitinase, muraminase, and peptidase) and acetylation of Trp-P-1 and IQ on the binding action of bacteria and cell wall material were also analysed to understand the possible processes involved in the binding of lactic acid bacteria to carcinogenic heterocyclic amines.Key words: mutagen, heterocyclic amines, lactic acid bacteria, binding, miso.

ISSN:0008-4166    

DOI:10.1139/w97-133

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The methylotrophic yeastCandida boidiniiis able to utilize pectic substances as the only carbon source. The primary utilization of methanol released from pectin is followed by adaptation to pectate medium. The duration of activation of a secondary pathway was critical for survival of yeast in the absence of other carbon sources. The utilization of pectin-containing media is associated with the production of pectic enzymes. The main polygalacturonase activities were found within the upper layer of the cell wall as shown by the method of gradual ultrasonication.Key words: pectic substances, pectic enzymes, pectin utilization,Candida boidinii, ultrasound.

ISSN:0008-4166    

DOI:10.1139/w97-142

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Chitinolytic bacteria are used as biocontrol agents of plant pathogenic fungi. They might also potentially inhibit growth of molds, e.g.,Aspergillusspp. andPenicilliumspp., in stored plant material. We isolated chitinolytic bacteria from airtight stored cereal grain and evaluated their antifungal capacity. Between 0.01 and 0.5% of the total aerobic counts were chitinolytic bacteria. Gram-negative bacteria, mainlyPseudomonadaceae, constituted approximately 80% of the chitinolytic population. Gram-positive isolates belonged predominantly to theCorynebacterium-Arthrobactergroup,Streptomyces, andBacillus. Chitinolytic activity was evaluated using culture filtrates from chitin-grown isolates as the release ofp-nitrophenol fromp-nitrophenylN,N'-diacetylchitobiose and as the formation of clearing zones on chitin agar. No correlation between chitinolytic activity and antifungal effects was found when challengingPenicillium roquefortiDierckx with bacterial isolates on chitin agar in a dual culture bioassay. Fungal hyphae frequently grew seemingly unaffected through the bacterial colony of a high chitinase producer on colloidal chitin. Only 4% of the chitinolytic isolates had strong effects on fungal growth. Among these,Streptomyces halstedii(K122) andStreptomyces coelicolor(K139) inhibited growth of a broad range of fungi.Streptomyces halstediiaffected hyphal morphology and decreased the radial growth rate of all fungi investigated. These effects were not caused by volatile metabolites, polyenes, orN-carbamoyl-D-glucosamine.Key words: antifungal, chitinase,Streptomyces halstedii,Streptomyces coelicolor.

ISSN:0008-4166    

DOI:10.1139/w97-141

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Calothrixis a filamentous cyanobacterium that has a single terminal heterocyst and a tapering morphology. It exists in two forms: mature filaments as described and motile hormogonia, which have a distinct morphology and serve as a dispersal mechanism for the organism. These cyanobacteria are common inhabitants of freshwater environments, where they are subjected to a variety of fluctuating conditions, including levels of dissolved metal ions. The present study represented an initial investigation of the effects of increasing metal ion concentrations onCalothrixas assessed ultrastructurally by transmission electron microscopy and through alterations observable by light microscopy and growth studies. Exposure of filaments to various levels of the alkaline earth cations Ca2+, Mg2+, Sr2+, and Ba2+led to various changes in structure, indicating effects on the organism's physiology. These included perturbation of cell envelope layers, such that the formation of outer membrane vesicles was enhanced, alteration to the patterns and abundance of sheath material formed, alteration of thylakoid (photosynthetic) membrane structure, and inhibition of hormogonium formation and release. It was interesting to note that even cations that are not typically thought of as toxic (Ca2+and Mg2+) could have profound effects on the cells to the extent of inhibiting growth at the maximum levels used in this study (5 mM), which are below these often found in natural environments. These results give an indication that the presence of metal ions in natural environments can have an important influence on the structural and growth characteristics of commonly found cyanobacteria to the extent of making them appear, on a macroscopic basis, as different organisms entirely. This puts a note of caution on future field observations and interpretations of the effects of pollutants on natural microbial communities.Key words: cyanobacteria, metals, ultrastructure.

ISSN:0008-4166    

DOI:10.1139/w97-132

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Attempts to isolate the N2-fixing endophyte ofCeanothus caeruleus(Rhamnaceae) root nodules, led to the isolation of nine actinomycetous strains. Owing to their inability to fix nitrogen (Fix-) and nodulate (Nod-), they could not be regarded as the effective endophyte. Characterization was done based on morphological and physiological features and 16S rDNA sequence analysis. The effectiveFrankiaendophyte was characterized without cultivation by amplification, cloning, and sequencing of nearly full length 16S rDNA and partialnifHgenes. Phylogenetic analysis based on 16S rDNA revealed that both the effective endophyte and the isolated actinomycetes belong to two different but well-defined lineages within the familyFrankiaceae. One lineage is formed mainly by uncultured endophytes that so far have resisted isolation, and the other includes only Fix-/Nod-isolates. Application of temperature gradient gel electrophoresis techniques to actinorhizal nodules allowed us to detect and identify 16S rDNA sequences from both the Fix+and the Fix-nodule inhabitants. Interestingly, these same two sequences were detected onHippophae rhamnoidesnodules obtained after inoculation withCeanothus caeruleusnodule suspensions. The isolates were located in the outer layers of the nodule.Key words:Frankia,Ceanothus, 16S rDNA,nifH, temperature gradient gel electrophoresis (TGGE), Fix-/Nod-strains.

ISSN:0008-4166    

DOI:10.1139/w97-138

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A DNA fragment containing therecAgene ofGluconobacter oxydanswas isolated and further characterized for its nucleotide sequence and ability to functionally complement variousrecAmutations. When expressed in anEscherichia coli recAhost, theG. oxydans recAprotein could efficiently function in homologous recombination and DNA damage repair. TherecAgene's nucleotide sequence analysis revealed a protein of 344 amino acids with a molecular mass of 38 kDa. We observed anE. coli-like LexA repressor-binding site in theG. oxydans recAgene promoter region, suggesting that a LexA-like mediated response system may exist inG. oxydans. The expression ofG. oxydans recAinE. coliRR1, arecA+strain, surprisingly caused a remarkable reduction of the host wild-typerecAgene function, whereas the expression of bothSerratia marcescens recAandPseudomonas aeruginosa recAgene caused only a slight inhibitory effect on function of the host wild-typerecAgene product. Compared with theE. coliRecA protein, the identity of the amino acid sequence ofG. oxydansRecA protein is much lower than those RecA proteins of bothS. marcescensandPseudomonas aeruginosa. This result suggests that the expression of another wild-type RecA could interfere with host wild-typerecAgene's function, and the extent of such an interference is possibly correlated to the identity of the amino acid sequence between the two classes of RecA protein.Key words:Gluconobacter oxydans,recAgene, recombination, SOS function, interference.

ISSN:0008-4166    

DOI:10.1139/w97-140

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The production of proteolytic enzymes by 10Clostridium difficileisolates of varying toxigenicity and clinical origin was studied to determine if all isolates secreted proteases. Different protease substrates were studied: gelatin, collagen, phenylazobenzyloxycarbonyl-leucyl-glycyl-L-prolyl-D-arginine (Pz-peptide), casein, azocasein, and azocoll. All isolates degraded gelatin, collagen, and azocoll. The supernatants of all isolates contained an enzyme capable of attacking gelatin incorporated in a polyacrylamide gel (zymograms) and forming two closely spaced lytic bands with an estimated molecular mass of 35→40 kDa. Polyclonal antibodies, produced against theC. difficilegelatinase, revealed in Western blots a 35-kDa protein in the culture supernatants of allC. difficileisolates. In the same manner,Clostridium perfringenscollagenase polyclonal antibodies detected a 120-kDa protein in the culture supernatants of all isolates; this suggests that at least two proteases may exist inC. difficile. The protease activities of the 10 strains examined did not seem strikingly different quantitatively but were in general weak and their role in pathogenicity is suspect.Key words:Clostridium difficile, proteolytic enzymes.

ISSN:0008-4166    

DOI:10.1139/w97-145

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Clover and potatoes, in a crop rotation, were found to share specific associations of bacterial endophytes. Twenty-five bacterial species from 18 genera were common to both clover and potatoes and represented 73% of all the bacteria recovered from clover root tissues and 73% of all the bacteria recovered from potato tubers. Endophytic bacteria tested in potato plant bioassays were predominantly plant growth neutral (56%). The remainder were either plant growth promoting (21%) or plant growth inhibiting (24%)(P< 0.05). Of the plant growth promoting bacteria, 63% increased shoot height, 66% increased shoot wet weight, and 55% increased root wet weight. The effects of plant growth inhibiting bacteria were restricted to reductions in plant height (86%) and shoot wet weight (36%); root weight was not affected. Of the bacteria tested, 74% showed some degree of in vitro antibiosis to the clover and potato pathogenRhizoctonia solani. Such endophytic intercrop bacterial associations appear to be complementary in nature and support the view that there are microbial benefits to be gained from clover in crop sequences with potatoes, beyond those of the residual nitrogen left in the soil and the organic matter added.Key words:Trifolium, allelopathy, endophytic, plant growth promoting, antifungal, crop rotation,Solanum.

ISSN:0008-4166    

DOI:10.1139/w97-146

出版商:NRC Research Press    

年代:1998

数据来源: NRC