ISSN:0008-4166    

DOI:10.1139/m92-001

出版商:NRC Research Press    

年代:1992

数据来源: NRC

ISSN:0008-4166    

DOI:10.1139/m92-002

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The purple, nonsulfur phototrophic bacteriumRhodobacter capsulatushas recently been found to contain several pigment biosynthetic operons that exhibit marked transcription read through into downstream operons that encode polypeptide components of photosynthetic pigment-protein complexes. This phenomenon has been found to be phenotypically significant for adaptation to changes in environmental conditions, and the term superoperon has been proposed to describe this sort of coupled transcriptional arrangement. We summarize the data that led to recognition of this novel transcriptional arrangement and suggest that superoperons might be more prevalent in prokaryotes than has heretofore been recognized.Key words: superoperons, overlapping transcription units, photosynthesis genes.

ISSN:0008-4166    

DOI:10.1139/m92-003

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Monochloramine preparedin situby first adding chlorine to a suspension of microorganisms, followed by subsequent addition of ammonia, inactivated the MS2 coliphage more rapidly than did exposure of phage to monochloramine prepared either by adding chlorine to ammonia or by adding chlorine and ammonia simultaneously. The rapid viral inactivation was apparently due to the exposure of MS2 to free chlorine before the addition of ammonia. The average 99% CT value of MS2 when exposed to free chlorine was 1.3 and 1.1 at 5 and 15 °C, respectively. The average 99% CT values of MS2 briefly exposed to the combined action of free chlorine followed by the addition of ammonia to form monochloraminein situwere 19.3 and 1.5 at 5 and 15 °C, respectively. No 99% CT values were calculated for the inactivation of MS2 with preformed monochloramine because less than 1 log (90%) of inactivation occurred during a 4-h contact time. Inactivation of MS2 by monochloramine was more rapid at 15 than at 5 °C and when the chlorine to nitrogen weight ratio was 5:1 compared with 3:1. Monochloramine was a more efficient inactivating agent for the coliformsEscherichia coliandKlebsiella pneumoniaethan it was for the MS2 coliphage.Key words: chlorine, monochloramine, virus, bacteria, disinfection.

ISSN:0008-4166    

DOI:10.1139/m92-004

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Two Gram-positive coryneform bacteria that degradedp-chlorophenol isolated from a continuous culture system are characterized. Isolate B (probably anArthrobactersp.) completely removed thep-chlorophenol from a medium with a concomitant increase in cell density within 16 h. Isolate F similarly removed thep-chlorophenol within 28 h but without an increase in cell density. Isolates B and F also removed thep-chlorophenol from a medium withp-chlorophenol as the sole carbon source within 32 and 48 h, respectively. The optimal temperature forp-chlorophenol degradation by both organisms was 25 to 30 °C. The optimal pH range forp-chlorophenol degradation was pH 7–9 for isolate B and pH 8–9 for isolate F. Since these native environmental bacteria can degradep-chlorophenol, they may have an important application in waste water treatment processes.Key words: biodegradation, bioremediation, xenobiotics.

ISSN:0008-4166    

DOI:10.1139/m92-005

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Spores of the strain NCIB 8122 ofBacillus cereushave been depleted of coats by treatment with 0.1% sodium dodecyl sulfate – 200 mM 2-mercaptoethanol – 0.5 M NaCl (pH 9.6). The coat-depleted spores did not show any decrease in viability, heat resistance, refractility, dipicolinic acid content, or specific activities of several protoplastic enzymes. The germinative response of the coat-depleted spores to adenosine and several analogues thereof was found qualitatively similar to that obtained with intact spores. However, germination kinetics appeared to be affected by coat removal, since germination rate measured as loss of refractility was eight times slower even at inducer concentrations 10-fold higher than those required to promote optimal germination response of intact spores. Loss of heat resistance, on the other hand, was hardly affected by coat removal. These results suggest that, even though spore coats are not essential for the triggering reaction, they are required for a rapid evolution of the later events in the germination process.Key words: adenosine analogues, germination-triggering reaction, spore coats, coat-depleted spores,Bacillus cereus.

ISSN:0008-4166    

DOI:10.1139/m92-006

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The compatibility of a select group of plant growth promoting rhizobacterial strains with chemicals commonly used as seed treatments was investigated. Strains in several genera (Serratia,Pseudomonas, and coryneform-like bacteria) were found to be tolerant to Vitavax RS (containing lindane, carboxin, and thiram), Epic (iprodione), and (or) captan testedin vitroat commercial rates. Six of 10 strains survived equally, and exhibited similar root colonization, on Vitavax RS treated and nontreated seed. Four of seven strains tested (Serratiaspp. andP.fluorescens) were likewise found to be compatible with a captan seed treatment on supersweet corn, using the same criteria. Ability of bacteria to grow on pesticide-amended media did not always indicate compatibility with chemical seed treatmentsin vivo. A greenhouse study demonstrated that enhanced emergence occurred with the coryneform-like strain 44-9 on Vitavax RS treated canola seed grown under conditions favoring disease due toRhizoctonia solani. The ability to combine plant growth promoting rhizobacterial strains with current agrichemicals for plant growth stimulation and disease control is indicated.Key words: pesticide compatibility,Pseudomonas, agrichemicals,Serratia, damping-off, plant growth promoting rhizobacteria.

ISSN:0008-4166    

DOI:10.1139/m92-007

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

We have characterized two mutants ofRhizobium melilotiL5-30 obtained by random mutagenesis usingMu–lacZthat were defective in transport of C4-dicarboxylic acids. These mutants induced ineffective nodules on alfalfa. Mutations in the two strains appeared to be located in adctAgene. Levels ofdctAgene expression were determined under different environmental conditions usingdctA–lacZfusions, and β-galactosidase activities increased in response to osmotic stress and also when the cells were incubated in medium low in calcium. The transcriptional induction of thedctAgene by environmental signals was decreased by DNA gyrase inhibitors such as novobiocin and coumermycin.Key words:Rhizobium meliloti, nitrogen fixation, dicarboxylate transport.

ISSN:0008-4166    

DOI:10.1139/m92-008

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Bacterial abundance and biomass were studied in April, July, and October 1989 at 13 stations along 300 km of the course of the river Seine, including Paris and its suburbs. Monthly investigations were carried out at five stations downstream from Paris where the river receives the effluent of an important waste water treatment plant (Achères). As a result of an input of allochthonous bacteria from the effluent of the plant, an increase in bacterial abundance and biomass was observed below Achères (from about 5 × 109to 15 × 109cells L−1and from 100 to 750 μg C L−1). This was followed by a rapid decrease. The allochthonous bacteria comprised a high proportion of large bacteria, which disappeared at a much higher rate than the small bacteria (0.0366 vs. 0.0125 h−1). Paradoxically, these large bacteria grew at a rate twice that of the smaller cells in culture experiments (0.129 vs. 0.065 h−1in June and 0.118 vs. 0.071 h−1in October). These large bacteria must therefore be subjected to intense losses (grazing, sedimentation, etc.). Higher rates of discharge of the river, i.e., a shorter residence time of the water masses, appeared to transmit the Achères signal farther, leading to faster transport of the bacterial populations.Key words: bacterioplankton ecology, size fractions, river ecosystem.

ISSN:0008-4166    

DOI:10.1139/m92-009

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

High molecular weight DNA was readily isolated from all methanogens treated, as well as from thermophilic anaerobic eubacteria, by grinding cells frozen in liquid N2, prior to lysis with SDS. DNA can subsequently be purified by the usual phenol–chloroform extractions. The procedure yields DNA readily cut by restriction enzymes and suitable for oligonucleotide probing, as well as for mole percent G + C content determination by thermal denaturation. The method routinely yields DNA of high molecular weight and is an improvement over DNA isolation methods for many methanogens, which often involve an initial breakage of the cells in a French pressure cell.Key words: methanogens, archaebacteria, archaea, DNA isolation.

ISSN:0008-4166    

DOI:10.1139/m92-010

出版商:NRC Research Press    

年代:1992

数据来源: NRC