摘要:

Condensed thiophenes comprise a significant portion of the organosulfur compounds in petroleum and in other products from fossil fuels. Dibenzothiophene (DBT) has served as a model compound in biodegradation studies for over two decades.However, until quite recently, few other organosulfur compounds were studied, and their fates in petroleum-contaminatedenvironments are largely unknown. This paper presents a review of the types of organosulfur compounds found in petroleum and summarizes the scant literature on toxicity studies with condensed thiophenes. Reports on the biodegradation ofbenzothiophene, alkylbenzothiophenes, DBT, alkylDBTs, and naphthothiophenes are reviewed with a focus on the identification of metabolites detected in laboratory cultures. In addition, recent reports on quantitative studies with DBT andnaphtho[2,1-b]thiophene indicate the existence of polar sulfur-containing metabolites that have escaped detection andidentification.Key words: biodegradation, condensed thiophenes, dibenzothiophene, microbial metabolism, toxicity.

ISSN:0008-4166    

DOI:10.1139/w98-045

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The locomotory and feeding responses of aEuplotessp. to attached populations ofVibrio natriegensandPseudomonas fluorescensin a continuous flow system were analyzed by computer image analysis of videomicroscopy recordings. Upon entry into the chamber, the ciliates moved in long continuous arcs 300 µm in length during whichtime no bacteria were consumed. As feeding began, the average path length shortened, the arcs became tighter, and the ciliates changed direction more frequently. The feeding activity of theEuplotesappeared to be gregarious, being concentrated in patches within the biofilm of attached bacteria. It was also noted that the feeding effort targeted patches previously visited by otherEuplotes, despite reduced bacterial density relative to the surrounding field of attached bacteria. This focused and intense feeding activity resulted in localized zones of nearly complete clearance within the attached bacterial populations. Loss of bacteria and averaged ciliate presence within feeding patches were determined from digitized time series images and discrimination thresholds for particle size. These data were used to determine grazing rates indicating thatEuplotessp. removed 120V. natriegenscells·ciliate–1·h–1and up to 882P. fluorescenscells·ciliate–1·h–1. However, surface clearance rates forEuplotessp. grazing onV. natriegensandP. fluorescenswere 0.02 and 0.03 mm2·ciliate–1·h–1, respectively, indicating that surface grazing pressure was fairlyconsistent within the patches of intense feeding activity. The effect of such intense localized feeding behaviour on attached orbiofilm bacteria would be to increase spatial and temporal heterogeneity within biofilms.Key words: digital image analysis,Euplotes, grazing, bi

ISSN:0008-4166    

DOI:10.1139/w98-057

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

We investigated the effects of root colonization by soil microbes on the subsequent colonization by a bacterial inoculant,Pseudomonas fluorescensMelRC2Rif. When a soil bacterial community was introduced onto tomato roots,subsequent colonization by MelRC2Rif was significantly lowered. However, soil fungi had no suppressive effects, suggesting that bacteria may be involved in the suppression. When individual bacterial strains were examined, most strains except forP. fluorescensshowed no significant suppressive effect on subsequent colonization by MelRC2Rif. In contrast, four out of sixP. fluorescensstrains significantly suppressed subsequent colonization by MelRC2Rif. Gram-negative bacteria,which had little suppressive effect on colonization by MelRC2Rif with individual inoculation, elicited suppression in somecombination treatments. Simultaneous inoculation of individual bacterial strains with MelRC2Rif indicated that suppressiveeffect by these strains occurred only when MelRC2Rif was inoculated later to tomato roots. These results suggest that aless competitive bacterial strain may interfere with the colonization of a competitive strain on tomato rhizospheres.Key words: ecological niche, bacterial colonization, rhizosphere, competition.

ISSN:0008-4166    

DOI:10.1139/w98-047

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Five strains of facultatively anaerobic moderately thermophilic bacteria were isolated from two hot springs in the intertidal zone of Lutao, Taiwan. They produced extracellular agarase on agar medium, yielding reducing sugars and organic acids as the end products under either aerobic or anaerobic conditions. The growth temperature range was approximately 38–58°C with an optimal temperature of about 48°C. The five strains tolerated a relatively narrow pH range from 7.0 to 8.5. They were Gram-negative halophiles growing optimally at 2.0–2.5% NaCl (ca. 0.34–0.43 M). They were capable of anaerobic growth by fermenting glucose and producing various organic acids such as butyrate, propionate, formate, lactate, and acetate. Cells grown in liquid medium were motile monotrichous cocci, normally 0.8–0.9 µm in diameter. They possessed saturated anteiso-15-carbon acid (anteiso-C15:0) as the most abundant cellular fatty acid (46.0–51.3 mo1%) and had G+Ccontents ranging from 65.5 to 67.0 mo1%. They are the first thermophiles found to degrade agar and also the first halophilicthermophilic bacteria known to be capable of both aerobic and anaerobic fermentative growth. These bacteria are considered to represent a new genus that we namedAlterococcus,andAlterococcus agarolyticusis the type species.Key words:Alterococcus agarolyticus, thermophilic bacteria, halophilic bacteria, agar-degrading bacteria, fermentative b

ISSN:0008-4166    

DOI:10.1139/w98-051

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Chitinase (EC 3.2.1.14) was isolated from the culture filtrate ofFusarium chlamydosporumand purified by ion-exchange chromatography and gel filtration. The molecular mass of purified chitinase was 40 kDa as estimated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. Chitinase was optimally active at a pH of 5 and stable from pH 4 to 6 and up to 40°C. Among the metals and inhibitors tested, mercuric chloride completely inhibited the enzyme activity. The activity of chitinase was high on colloidal and pure chitin. The purified chitinase inhibited the germination of uredospores ofPuccinia arachidisand also lysed the walls of uredospores and germ tubes. The results from these experiments indicated that chitinase ofF. chlamydosporumplays an important role in the biocontrol of groundnut rust.Key words:Fusariumchlamydosporum, chitinase, purification,Puccinia arachidis, uredospore

ISSN:0008-4166    

DOI:10.1139/w98-043

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The cofactor specificity of serine hydroxymethyltransferase (SHMT) activities was tested in extracts of several methanogens using tetrahydromethanopterin (H4MPt) fromMethanobacterium thermoautotrophicumMarburg, tetrahydrosarcinapterin (H4SPt) fromMethanosarcina barkeri, and tetrahydrofolate (H4folate) as the potential C1carrier. InMethanosphaera stadtmanaeandMethanococcus thermolithotrophicus, the activities were H4MPt dependent. InMethanospirillum hungateiGP1,Methanosaeta concilii,Methanolobus tindarius, andMethanosarcina barkeriFusaro, the activities werestrictly H4folate dependent. H4SPt was reactive with the SHMT ofMethanosphaera stadtmanaebut not with that ofMethanosarcina barkeri. In bothMethanosarcina barkeriandMethanospirillum hungatei, pyridoxal phosphate stimulated SHMT activity. The apparentKmvalues for H4folate andL-serine were 0.086 and 0.29 mM inMethanosarcina barkeriand 0.065 and 0.31 mM inMethanospirillum hungatei, respectively.Key words: tetrahydromethanopterin,tetrahydrofolate, Archaea, serine hydroxymethyltransferase, methanogen.

ISSN:0008-4166    

DOI:10.1139/w98-050

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In a genomic library ofErwinia amylovora, a locus has been identified that can suppress anErwinia stewartiircsAmutant. In addition, the locus induced a mucoid sticky phenotype of colonies in a wild-type strain ofErwinia stewartiiand increased exopolysaccharide synthesis in several species of bacteria belonging to the genusErwinia. An open reading frame was identified at this locus encoding a 225 amino acid protein that contained a helix-turn-helix motif typical of transcriptional regulators. The corresponding gene was subsequently namedrcsV(regulator of capsular synthesis affecting viscosity). A mutant ofrcsVin wild-typeErwinia amylovorahad no detectable phenotype and produced typical levels of amylovoran under laboratory conditions. ThercsVgene on a high copy number plasmid under the control of its own promoter did not alter amylovoran production, in contrast to in-frame fusions of the structural gene in expression vectors. Since even thelacpromoter was inert in the expression ofrcsV, a DNA-binding protein could inhibit transcription of the gene inErwinia amylovora. On the other hand, anErwinia amylovorarcsA mutant was suppressed byrcsVwhen its promoter was replaced and the structural gene fused in-frame withlacZ' ormalE. Northern blots, with total RNA fromErwinia amylovora,or promoter analysis using the GUS reporter gene did not show expression ofrcsVinErwinia amylovora, although primer extension analysis did. RcsV could be a component involved in the regulation of amylovoran synthesis, and gene expression may require an unknown external signal during the life cycle or pathogenesis ofErwinia amylovora.Key words: amylovoran, fire blight,rcsA-like activator, fusion protein.

ISSN:0008-4166    

DOI:10.1139/w98-052

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Bacteria isolated from a pentachlorophenol (PCP) contaminated site grew in the presence of 50 µg PCP/mL but were not able to degrade it in either liquid medium or the presence of 1% sterile potting soil as a solid support. Probes developed using the gene sequence of PCP-4-monooxygenase(pcpB)fromSphingomonas chlorophenolicasp.nov hybridized to twoseparate isolates. Identification based on fatty acid methyl ester profiles (Sherlock™), substrate utilization (BIOLOG™), and16S rRNA showed that the two strains were different from each other and fromSphingomonas chlorophenolica. Sequences from these isolates, amplified by polymerase chain reaction, confirmed the homology withpcpB. The presence ofpcpBsequences in these nondegraders indicated that growth and hybridization data alone were insufficient for predicting degradation capability.Key words: pentachlorophenol, Sphingomonas chlorophenolica,pcpBgene, pentachlorophenol-4-monooxygena

ISSN:0008-4166    

DOI:10.1139/w98-055

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The white rot fungusPleurotus ostreatuswas grown in a chemically defined solid state fermentation system amended with cotton stalk extract (CSE).Treated cultures exhibited increased laccase activity as well as enhanced lignin mineralization. Mineralization of [14C]lignin initialized 4 days earlier in CSE-supplemented cultures than in control cultures. Total mineralization in the first 16 days was 15% in the CSE-treated cultures, compared with only 7% in the controls. Cotton stalk extract also contained compounds that serve as substrates for laccase purified fromP. ostreatusas shown by oxygen consumption, as well as changes in the UV–visible spectrum.Key words: cotton,Pleurotusostreatus, white rot, laccase, lignin biodegradation

ISSN:0008-4166    

DOI:10.1139/w98-054

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Uptake of octadecane byAcinetobacter calcoaceticusS19 was found to be 70% during growth (doubling time of 4 h), of which 60% was incorporated into the cells and 40% was oxidized to14CO2. The ratio of [14C]octadecane uptake to its mineralization by whole cells was similar to that found during the growth ofA. calcoaceticusS19. After 4 h of incubation of cells with [14C]octadecane, 44% was mineralized to14CO2, while the rest remained associated with the cells. Octadecane uptake was not observed under anaerobic conditions, indicating an absolute requirement for oxygen.Acinetobacter calcoaceticusS19 converted octadecane to the corresponding octadecanol and octadecanoic acid; the corresponding aldehyde was not detected, however. Octadecanoic acid was partially degraded through &bgr;-oxidation to CO2and partly assimilated as cell biomass.Key words:Acinetobacter calcoaceticus, octadecane uptake, mineralization.

ISSN:0008-4166    

DOI:10.1139/w98-049

出版商:NRC Research Press    

年代:1998

数据来源: NRC