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1.
Two strains of Alcaligenes denitrificans, designated BRI 3010 and BRI 6011, were isolated from polychlorinated biphenyl (PCB)-contaminated soil using 2,5-dichlorobenzoic acid (2,5-DCBA) and 2,4-DCBA, respectively, as sole carbon and energy sources. Both strains degraded 2-chlorobenzoic acid (2-CBA), 2,3-DCBA, and 2,5-DCBA, and were unable to degrade 2,6-DCBA. BRI 6011 alone degraded 2,4-DCBA. Growth of BRI 6011 in yeast extract and 2,6-DCBA induced pyrocatechase activity, but 2,6-DCBA was not degraded, suggesting the importance of an unsubstituted carbon six of the aromatic ring. Metabolism of the chlorinated substrates resulted in the stoichiometric release of chloride, and degradation proceeded by intradiol cleavage of the aromatic ring. Growth of both strains on 2,5-DCBA induced pyrocatechase activities with catechol and chlorocatechols as substrates. In contrast to dichlorobenzoic acids, growth on 2-CBA, benzoic acid, mono- and dihydroxybenzoic acids induced a pyrocatechase activity against catechol only. Although 2,4-DCBA was a more potent inducer of both pyrocatechase activities, its utilization by BRI 6011 was inhibited by 2,5-DCBA. Specific uptake rates using resting cells were highest with 2-CBA, except when the resting cells had been previously grown on 2,5-DCBA, in which case 2,5-DCBA was the preferred substrate. The higher rates of 2,5-DCBA uptake obtained by growth on that substrate, suggested the existence of a separately induced uptake system for 2,5-DCBA. 相似文献
2.
Summary
Acinetobacter calcoaceticus, strain Bs 5, oxidized 3-chlorobenzoate only in the presence of a readily available energy source such as succinate or pyruvate. Cultures of the organism growing in the presence of 3-chlorobenzoate at concentrations greater than 250 M turned darkbrown on prolonged incubation. After centrifugation and acidificition of the supernatants to pH 2, a dark pigment could be precipitated. It was shown to contain bound chlorine and probably originated from 3-chlorocatechol and 4-chlorocatechol, which accumulated in cultures growing in the presence of 3-chlorobenzoate.3-Chlorobenzoate induced the ability to oxidize benzoate and catechol in the bacteria, the latter by orthofission. In the presence of an energy source, 3-chlorobenzoate-induced cells oxidized 3-chlorobenzoate at a rate, which was about 25% of the turnover rate for benzoate.In a continuous culture of the organism, growing in the presence of 1 mM 3-chlorobenzoate at a dilution rat of 0.025 h –1, all culture parameters including the ability of the cells to oxidize benzoate, were oscillating. This oscillation was attributed to the transient build-up of toxic concentrations of chlorocatechols. 4-chlorocatechol was shown to be about six times more toxic than 3-chlorobenzoate. In another series of continuous culture experiments, 3-chlorobenzoate induced the synthesis of the benzoate oxidizing enzyme system of A. calcoaceticus strain Bs 5 at a concentration of 2.5 M, but appeared to lose its inducing potential towards this enzyme system at about 0.5 M. 相似文献
3.
A strain of Pseudomonas fluorescens was capable of co-metabolizing 3-chlorobenzoic acid with the production of a chlorinated catechol black pigment. A peroxidase and another enzymatic activity referred to as a polyphenol oxidase were found to be involved in the oxidation of 4-chlorocatechol to 4-chloro-1,2-benzoquinone, i.e. in the production of highly reactive substrates for pigment formation. Therefore, P. fluorescens cells were seen to take an active part not only in 3-chlorobenzoate mineralization but also in overall pigment production. pH was found to be a key parameter in the regulation of the activity of P. fluorescens oxidoreductive enzymes. Ultrastructural investigations showed that electron dense granules of pigment were distributed throughout the cytoplasm of Pseudomonas fluorescens cells grown in presence of 3-chlorobenzoate, as confirmed also by Thiéry cytochemical investigations.In these cells, an extensive contraction of the cytoplasm as well as a significant damage to the cell wall after two days of incubation, suggested that pigment production caused a premature death of the cells accompanied by the leakage of the cell content. Pigment production seemed to occur mostly in the cytoplasmic context where the electron dense material accumulates until it is released in the medium after the cell lysis.Abbreviations 3-CBA
3-chlorobenzoic acid
- BA
benzoic acid
- 4-CC
4-chlorocatechol
- 3-CC
3-chlorocatechol
- MBTH
3-methyl-2-benzothiazolinone hydrazone
-
l-DOPA
l-3,4-dihydroxyphenyl-alanine
- SPB
sodium phosphate buffer 相似文献
4.
Dimethylbenzothiophenes are among the sulfur heterocycles in petroleum that are known to be degraded by microbial activity. Six of the 15 possible isomers of dimethylbenzothiophene were synthesized and used in biotransformation studies with three Pseudomonas isolates that oxidize a variety of condensed thiophenes including methylbenzothiophenes and methyldibenzothiophenes. The isomers of dimethylbenzothiophene were chosen to have a variety of substitution patterns: both methyl groups on the thiophene ring (the 2,3- isomer); a methyl group on each of the rings (the 2,7-, 3,5- and 3,7-isomers); and both methyl groups on the benzene ring (the 4,6- and 4,7- isomers). Each isolate was grown on 1-methylnaphthalene or glucose in the presence of one of the dimethylbenzothiophenes and culture extracts were analyzed to identify nearly 30 sulfur-containing metabolites in total. Sulfoxides and sulfones were commonly found metabolites in culture extracts from the 2,3-, 2,7- and 3,7-isomers, whereas 2,3-diones, 3(2H)-ones and 2(3H)-ones were formed from the 4,6- and 4,7-isomers. High-molecular-weight products, some of which were tentatively identified as tetramethylbenzo[ b]naphtho[1,2- d]thiophenes, were detected in the extracts of cultures incubated with 4,6- or 4,7-dimethylbenzothiophene. The methyl groups of all of the isomers, except 4,6-, were oxidized to give hydroxymethyl-methylbenzothiophenes and methylbenzothiophene-carboxylic acids, and these were the only products detected from the oxidation of 3,5-dimethylbenzothiophene. 相似文献
5.
The initial reactions possibly involved in the acrobic and anaerobic metabolism of aromatic acids by a denitrifying Pseudomonas strain were studied. Several acyl CoA synthetases were found supporting the view that activation of several aromatic acids preceeds degradation. A benzoyl CoA synthetase activity (AMP forming) (apparent K
m values of the enzyme from nitrate grown cells: 0.01 mM benzoate, 0.2 mM ATP, 0.2 mM coenzyme A) was present in aerobically grown and anaerobically, nitrate grown cells when benzoate or other aromatic acids were present. In addition to benzoate and fluorobenzoates, also 2-amino-benzoate was activated, albeit with unfavorable K
m (0.5 mM 2-aminobenzoate). A 2-aminobenzoyl CoA synthetase (AMP forming) was induced both aerobically and anaerobically with 2-aminobenzoate as growth substrate which had a similar substrate spectrum but a low K
m for 2-aminobenzoate (<0.02 mM). Anaerobic growth on 4-hydroxybenzoate induced a 4-hydroxybenzoyl CoA synthetase, and cyclohexanecarboxylate induced another synthetase. In contrast, 3-hydroxybenzoate and phenyl-acetate grown anaerobic cells appeared not to activate the respective substrates at sufficient rates. Contrary to an earlier report extracts from aerobic and anaerobic 2-aminobenzoate grown cells catalysed a 2-aminobenzoyl CoA-dependent NADH oxidation. This activity was 10–20 times higher in aerobic cells and appeared to be induced by 2-aminobenzoate and oxygen. In vitro, 2-aminobenzoyl CoA reduction was dependent on 2-aminobenzoyl CoA NAD(P)H, and oxygen. A novel mechanism of aerobic 2-aminobenzoate degradation is suggested, which proceeds via 2-aminobenzoyl CoA. 相似文献
6.
A mixed culture of a chlorobenzoate-(3-CBA)-degrading Pseudomonas aeruginosa, strain 3mT, and a phenol/cresols-degrading Pseudomonas sp., strain CP4, simultaneously and efficiently degraded mixtures of 3-CBA and phenol/cresols. However, strains 3mT and CP4 used ortho- and meta-ring cleavage pathways, respectively. Degradation of 3-CBA was complete when the 3-CBA was equal in amount to or less than that of phenol. CP4/3mT inoculum ratios (w/w) of 1:1 or 1:2 gave the most effective degradation of both the substrates in the mixture. The mixed culture degraded equimolar mixtures of 3-CBA/phenol up to 10 mm. Equimolar mixtures of 3-CBA and o-, m- or p-cresol were also degraded by the mixed culture.The authors are with the Microbiology and Bioengineering Department, Central Food Technological Research Institute, Mysore-570013, India; 相似文献
7.
A natural mixed aerobic bacterial culture, designated MIXE1, was found to be capable of degrading several low-chlorinated biphenyls when 4-chlorobiphenyl was used as a co-substrate. MIXE1 was capable of using all the three monochlorobenzoate (CBA) isomers tested as well as 2,5-, 3,4- and 3,5-dichlorobenzoate (dCBA) as the sole carbon and energy source. During MIXE1 growth on these substrates, a nearly stoichiometric amount of chloride was released: 0.5 g/l of each chlorobenzoate was completely mineralized by MIXE1 after 2 or 3 days of culture incubation. Two strains, namely CPE2 and CPE3, were selected from MIXE1: CPE2, referred to the Pseudomonas genus, was found to be capable of totally degrading both 2-CBA and 2,5-dCBA, whereas Alcaligenes strain CPE3 was capable of mineralizing 3-, 4-CBA and 3,4-dCBA. Substrate uptake studies carried out with whole cells of strain CPE2 suggested that 2-CBA was metabolized through catechol, while 2,5-dCBA was degraded via 4-chlorocatechol. 3-CBA, 4-CBA, and 3,4-dCBA appeared to be degraded through 3,4-dihydroxybenzoate by the CPE3 strain. MIXE1, which is capable of degrading several chlorobenzoates, should therefore be able to mineralize a number of low-chlorinated congeners of simple and complex polychlorinated biphenyl mixtures.
Correspondence to: F. Fava 相似文献
8.
A bacterial isolate, Pseudomonas aeruginosa 3mT, exhibited the ability to degrade high concentrations of 3-chlorobenzoate (3-CBA, 8 g l -1) and 4-chlorobenzoate (4-CBA 12 g l -1) (Ajithkumar 1998). In this study, by delineating the initial biochemical steps involved in the degradation of these compounds, we investigated how this strain can do so well. Resting cells, permeabilised cells as well as cell-free extracts failed to dechlorinate both 3-CBA and 4-CBA under anaerobic conditions, whereas the former two readily degraded both compounds under aerobic conditions. Accumulation of any intermediary metabolite was not observed during growth as well as reaction with resting cells under highly aerated conditions. However, on modification of reaction conditions, 3-chlorocatechol (3-CC) and 4-chlorocatechol (4-CC) accumulated in 3-CBA and 4-CBA flasks, respectively. Fairly high titres of pyrocatechase II (chlorocatechol 1,2-dioxygenase) activity were obtained in extracts of cells grown on 3-CBA and 4-CBA. Meta-pyrocatechase (catechol 2,3-dioxygenase) activity against4-CC and catechol, but not against 3-CC, was also detected in low titres. Accumulation of small amounts of 2-chloro-5-hydroxy muconic semialdehyde, the meta-cleavage product of 4-CC, was detected in the medium, when 4-CBA concentration was 4 mM or greater, indicating the presence of a minor meta-pathway in strain 3mT. However, 3-CBA exclusively, and more than 99% of 4-CBA were degraded through the formation of the respective chlorocatechol, via a modified ortho-pathway. This defies the traditional view that the microbes that follow chlorocatechol pathways are not very good degraders of chlorobenzoates. 4-Hydroxybenzoatewas readily (and 3-hydroxybenzoate to a lesser extent) degraded by the strain, through the formation of protocatechuate and gentisate, respectively, as intermediary dihydroxy metabolites. 相似文献
9.
Summary
Pseudomonas and Vibrionaceae strains with the capacity to produce biosurfactants when growing on sucrose were isolated from the environment by a simple screening procedure. Agargrown colonies were randomly selected; each colony was suspended in a water droplet on a microscope slide. The tested strain was regarded as positive if the droplet spread over the surface.1779 Pseudomonas and 660 Vibrionaceae isolates were tested; 1% and 0.8% of the isolates, respectively, were positive for biosurfactant production. No production was detected amongst the isolates of a control group of 538 Gram-positive and 1063 Gram-negative strains.Four biosurfactant producing strains were grown in fermenter cultures on a semisynthetic medium using sucrose as carbon and energy source. The terminal concentrations of biosurfactants were in the range of a factor 40 times the critical micelle dilution. One P. fluorescens strain was grown in a carbon limited chemostat (succinate). The biosurfactant production was successively decreasing until it stopped after less than ten generation times. 相似文献
10.
Summary Three strains, RHO1, R3 and B1, tentatively identified as a Pseudomonas sp., an Alcaligenes sp. and a Pseudomonas sp. which were able to use 1,4-dichlorobenzene as the sole carbon and energy source were isolated from water of the Rhine river and from the sewage plant at Leverkusen-Bürrig. A hybrid strain, WR1313, which uses chlorobenzene as the growth substrate, was obtained by mating the benzene-growing Pseudomonas putida strain F1 with strain B13, a Pseudomonas sp. degrading chlorocatechols. Further selection of this strain for growth on 1,4-dichlorobenzene allowed the isolation of strain WR1323. During growth on 1,4-dichlorobenzene the strains released stoichiometric amounts of chloride. The affinity of the organisms to 1,4-dichlorobenzene was measured with strain R3 showing a K s value of 1.2 mg/l. Respiration data and enzyme activities in cell extracts as well as the isolation of 3,6-dichlorocatechol from the culture fluid are consistent with the degradation of 1,4-dichlorobenzene via 3,6-dichlorocatechol, 2,5-dichloro- cis,cis-muconate, 2-chloro-4-carboxymethylenebut-2-en-4-olide. 相似文献
11.
Peripheral metabolism was studied in the Pseudomonas putida 37cc transconjugant. In the strain grown on benzoate, pyrocatechase (PC) I with a low activity to chlorocatechols was induced, whereas PCII actively decomposing chlorocatechols was induced during its growth on 3-chlorobenzoic acid. The P. putida 37cc transconjugant grown on alpha-methylstyrene (MS) exerted the activity of both metapyrocatechase (MPC) and PC, whereas in the parent strain P. putida R-1 only MPC was involved in the degradation of alpha-MS. The substrate specificity of the enzymes involved in the ring cleavage by P. putida 37cc was compared to show that, apparently, MPC of the transconjugant was similar to this enzyme in the strain R-1 while PC decomposing chlorocatechols was similar to PC of the P. putida 87 donor. The regulation of the enzymes mediating the ring cleavage was studied in the parent strains and transconjugants. 相似文献
12.
Summary 3-Chlorobenzoate grown cells of Pseudomonas sp. strain B13 or Alcaligenes sp. strain A7-2 converted 3-fluorobenzoate to 2-fluoro-cis,cis-muconate with 87% yield. The latter strain produced 1.6 g/l. The type II muconate cycloisomerases of neither strain exhibit acitivity for 2-fluoro-cis,cis-muconate. Succinate grown cells of Pseudomonas sp. strain B13 converted benzoate to cis,cis-muconate (91% yield; 7.4 g/l). Enzyme tests confirmed that no muconate cycloisomerising enzyme was induced within 24 h. 相似文献
13.
The dehydrogenation of substituted 3,5-cyclohexadiene-1,2-diol-1-carboxylic acids by dihydrodihydroxybenzoic acid dehydrogenases from benzoate grown cells of Alcaligenes eutrophus and Pseudomonas sp. B 13 and 3 -chlorobenzoate grown cells of the latter organism was examined. No significant differences ( Km and Vrel values) were detected for the enzymes from both organisms. The same dihydrodihydroxybenzoic acid dehydrogenase is formed in Pseudomonas sp. B13 during growth on benzoate as well as on 3-chlorobenzoate. The lower turnover rates of 3- and 5-chlorodihydrodihydroxybenzoic acid compared to dihydrodihydroxybenzoic acid are counterbalanced by an increase in specific activity. With the exception of 4-substituted dihydrodihydroxybenzoic acids exhibiting relative high Km values, only slight sterical and electronic substituent effects are evident. Reaction rates were never reduced to a critical level. 相似文献
14.
The compatibility and efficiency of two ortho-cleavage pathway-following pseudomonads viz . the 3-chlorobenzoate (3-CBA)-degrader, Pseudomonas aeruginosa 3mT (3mT) and the phenol-degrader, P. stutzeri SPC-2 (SPC-2) in a mixed culture for the degradation of these substrates singly and simultaneously in mixtures was studied.
Another phenol-degrading strain, Pseudomonas sp. SoPC-5 (SoPC-5) that utilizes a meta-cleavage mode also was tried in co-culture with 3mT. The former combination was
found to be a better degrader of both the substrates when present alone. But, with inoculum levels of 0.15 mg cell dry wt
each of 3mT/SPC-2 or 3mT/SoPC-5 growth with 2 mM each of 3-CBA and phenol was slow with a lag of 24 h and degradation being
incomplete. However, with higher inocula in the ratios 1:1, 1:2, and 2:1, i.e., 0.3 + 0.3, 0.3 + 0.6, and 0.6 + 0.3 mg cell dry wt
of 3mT and SPC-2, respectively complete degradation of both the substrates occurred. Degradation of 3-CBA was complete with
the release of stoichiometric amounts of chloride (Cl −) when concentrations of phenol/3-CBA were varied as 2:2, 2:4, and 4:2 mM, i.e., even when the concentration of the more toxic
co-substrate 3-CBA was higher than phenol effective simultaneous degradation occurred at the inoculums ratio of 1:1 (0.3 mg
dry cell wt. of each strain). These studies clearly indicated the better suitability of ortho-cleavage-utilizing strains as
partners in a mixed culture than those follow different modes. 相似文献
15.
In the research, the single-and dual effects of phosphate-solubilizing bacteria (PSB) (B0, Pseudomonas sp. FA1, and Bacillus simplex UT1) and silicon (Si) (0, 150, 300, and 600 mg kg−1 used as silicic acid) on P uptake by sorghum (Sorghum bicolor L.) plant fertilized with soluble or insoluble P (rock phosphate—RP) were studied via a perlite-potted experiment. Moreover, the effects of various treatments on morphological (shoot and root dry weight), nutritional (the uptake of Si and K) and physiological parameters (activity of catalase, superoxide dismutase, and peroxidase enzymes) of this plant were also measured. When grown in RP-fertilized medium compared with those grown in soluble P-fertilized medium, both shoot biomass and root biomass of sorghum plants were noticeably diminished. The PSB strains and Si levels independently improved all the aforementioned parameters. Use of Si and PSB strains to sorghum plants grown in soluble P or insoluble P medium significantly augmented P use efficiency. Silicon not only augmented the uptake of P from sparingly soluble-P source (RP), but also augmented uptake of P from water-soluble P source. Both B. simplex UT1 and Pseudomonas sp. FA1 indicated a meaningful betterment in sorghum plant dry matter and uptake of P (and K and Si) under both soluble and insoluble P fertilization conditions with Pseudomonas sp. FA1 being more efficacious than B. simplex UT1. But, the dual use of the PSB with Si resulted in the greatest increase in sorghum plant P uptake and other measured growth indices. Application of 600 mg Si kg−1 and Pseudomonas sp. FA1 significantly augmented the P shoot concentration of sorghum plant fertilized with RP to an sufficient level (> 0.3%) in the range of P-fertilized sorghum plants. Therefore, in addition to PSB utilization, Si should be considered as soil amendment in agricultural soils inadequate in plant-available Si as a means of sustainable agriculture with respect to possible savings of scarce P resources. 相似文献
16.
Monofluoro- and monochlorobenzoates did not support the growth of Pseudomonas PN-1, either aerobically or anaerobically (nitrate respiration), when supplied as sole sources of carbon and energy. Anaerobic growth yields on nonfluorinated substrates were increased by p-fluorobenzoate (pFBz) with a utilization of pFBz and release of F -. Cell suspensions grown on p-hydroxybenzoate (pOHBz), either aerobically or anaerobically, only degraded o-fluorobenzoate (oFBz) and pFBz of the monohalogenated benzoates tested. Both compounds were catabolized anaerobically, but not aerobically, with a release of F -. oFBz was immediately attacked, by cells grown anaerobically on pOHBz, whereas pFBz was only degraded after a lag phase; chloramphenicol inhibited the breakdown of pFBz, but not oFBz, thereby indicating the need for additional enzyme(s) to attack pFBz. o-Chlorobenzoate (oClBz) inhibited the anaerobic, but not aerobic, oxidation of pOHBz and stopped anaerobic growth on pOHBz. A mutant was isolated which metabolized pOHBz in the presence of oClBz but it was defective in its anaerobic metabolism of benzoate (Bz). Comparative studies, of the mutant and Pseudomonas PN-1, indicated that the mutation involved a metabolic site common to Bz, oClBz and the monofluorobenzoates. The dependence of the oxidation rate of Bz and oFBz on their concentrations at a millimolar level, in the mutant but not Pseudomonas PN-1, suggested a defect at the permease level: the uptake of 14C-labelled Bz by the mutant was also concentration-dependent. The response of the organism to the inhibitory effect of oClBz on pOHBz catabolism is discussed with respect to its significance in the perturbation of natural degradative processes by unnatural chemicals in the environment.Non-common abbreviations Bz
benzoate
- pOHBz
p-hydroxybenzoate
- oFBz
o-fluorobenzoate
- mFBz
m-fluorobenzoate
- pFBz
p-fluorobenzoate
- oClBz
o-chlorobenzoate 相似文献
17.
Pseudomonas sp. A33 and other isolates of aerobic bacteria accumulated a complex copolyester containing 3-hydroxybutyric acid (3HB) and various medium-chain-length 3-hydroxyalkanoic acids (3HA MCL) from 3-hydroxybutyric acid or from 1,3-butanediol under nitrogen-limitated culture conditions. 3HB contributed to 15.1 mol/100 mol of the constituents of the polyester depending on the strain and on the cultivation conditions. The accumulated polymer was a copolyester of 3HB and 3HA MCL rather than a blend of poly(3HB) and poly(3HA MCL) on the basis of multiple evidence. 3-Hydroxyhexadecenoic acid and 3-hydroxyhexadecanoic acid were detected as constituents of polyhydroxyalkanoates, which have hitherto not been described, by 13C nuclear magnetic resonance or by gas chromatography/mass spectrometric analysis. In total, ten different constituents were detected in the polymer synthesized from 1,3-butanediol by Pseudomonas sp. A33:besides seven saturated (3HB, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, and 3-hydrohexadecanoate) three unsaturated (3-hydroxydodecenoate, 3-hydroxytetradecenoate and 3-hydrohexadecanoate) hydroxyalkanoic acid constituents occured. The polyhydroxyalkanoate synthase of Pseudomonas sp. A33 was cloned, and its substrate specificity was evaluated by heterologous expression in various strains of P. putida, P. oleovorans and Alcaligenes eutrophus. 相似文献
18.
Cell-free extracts of Pseudomonas sp. strains KB 740 and K 172 both contained high levels of glutaryl-CoA dehydrogenase when grown anaerobically on benzoate or other aromatic compounds and with nitrate as electron acceptor. These aromatic compounds have in common benzoyl-CoA as the central aromatic intermediate of anerobic metabolism. The enzymatic activity was almost absent in cells grown aerobically on benzoate regardless whether nitrate was present. Glutaryl-CoA dehydrogenase activity was also detected in cell-free extracts of Rhodopseudomonas, Rhodomicrobium and Rhodocyclus after phototrophic growth on benzoate. Parallel to the induction of glutaryl-CoA dehydrogenase as measured with ferricenium ion as electron acceptor, an about equally high glutaconyl-CoA decarboxylase activity was detected in cell-free extracts. The latter activity was measured with the NAD-dependent assay, as described for the biotin-containing sodium ion pump glutaconyl-CoA decarboxylase from glutamate fermenting bacteria. Glutaryl-CoA dehydrogenase was purified to homogeneity from both Pseudomonas strains. The enzymes catalyse the decarboxylation of glutaconyl-CoA at about the same rate as the oxidative decarboxylation of glutaryl-CoA. The green enzymes are homotetramers ( m=170 kDa) and contain 1 mol FAD per subunit. No inhibition was observed with avidin indicating the absence of biotin. The N-terminal sequences of the enzymes from both strains are similar (65%). 相似文献
19.
Biosorption of copper by Pseudomonas cepacia was found to be dependent on added copper concentration. Copper uptake by the cells was rapid over the range of copper concentrations tested and complete within the first 10 min of incubation time. The effect of pH on copper uptake by P. cepacia was determined using overlapping buffers over the pH range 3–8, and copper biosorption from a 10 mM copper solution was greatest at pH 7. Copper uptake (measured by analysis of cell digests) was unaffected by cyanide and azide (up to 30 mM) and by incubation of cells with a 10 mM copper solution at 4 °C. Evidence from these results suggested that copper uptake by P. cepacia cells involves surface binding and not intracellular accumulation by active transport. Biosorption of copper by various Pseudomonas isolates from metal-contaminated environments agreed well with copper biosorption by Pseudomonas strains from the National Collection of Type Cultures (NCTC). 相似文献
20.
Bacterial isolates from sludge samples collected at a local municipal sewage treatment plant were screened for bacteria producing
polyhydroxyalkanoates (PHA). Initially Sudan black B staining was performed to detect lipid cellular inclusions. Lipid-positive
isolates were then grown in a nitrogen limitation E2 medium containing 2% (w/v) glucose to promote accumulation of PHA before
the subsequent staining with Nile blue A. The positive isolates were quantified initially with a u.v. spectrophotometer, for
a very large number of isolates (105) and among them high PHA-producing isolates (15) were selected and were confirmed by
gas chromatographic analysis. The GC analysis showed the polymers produced by 13 of the selected isolates to be polyhydroxybutyrate
(PHB), and the remaining two isolates produced polyhydroxybutyrate-co-hydroxyvalerate (PHB-co-HV) copolymer. The proportion
of the PHA-positive bacterial isolates showed variability in the number of PHA accumulators during various months. The correlation
of PHB production with the cell dry weight (CDW) was found to be statistically significant. The metabolism of PHB in these
selected 15 isolates was studied using the Nile blue A staining, which showed an initial increase in the fluorescence followed
by a decline, on further incubation. All the selected 15 isolates were classified to genus level by studying their morphological
and biochemical characteristics. There were seven Bacillus species, three Pseudomonas species, two Alcaligenes species, two Aeromonas species, and one Chromobacterium species. 相似文献
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