共查询到20条相似文献,搜索用时 15 毫秒
1.
Desimone MF De Marzi MC Copello GJ Fernández MM Malchiodi EL Diaz LE 《Applied microbiology and biotechnology》2005,68(6):747-752
The aim of this work was to study the use of silicon oxide matrices for the immobilization and preservation of recombinant-protein-producing
bacteria. We immobilized Escherichia coli BL21 transformants containing different expression plasmids. One contained DNA coding for a T-cell receptor β chain, which
was expressed as inclusion bodies in the cytoplasm. The other two encoded bacterial superantigens Staphylococcal Enterotoxin
G and Streptococcal Superantigen, which were expressed as soluble proteins in the periplasm. The properties of immobilization
and storage stability in inorganic matrices prepared from two precursors, silicon dioxide and tetraethoxysilane, were studied.
Immobilized E. coli was stored in sealed tubes at 4 and 20°C and the number of viable cells and level of recombinant protein production were
analyzed weekly. Different tests showed that the biochemical characteristics of immobilized E. coli remained intact. At both temperatures selected, we found that the number of bacteria in silicon dioxide-derived matrix was
of the same order of magnitude (109 cfu ml−1) as before immobilization, for 2 months. After 2 weeks, cells immobilized in an alkoxide-derived matrix decreased to 104 cfu ml−1 at 4°C, and no viable cells were detected at 20°C. We found that immobilized bacteria could be used as a starter to produce
recombinant proteins with yields comparable to those obtained from glycerol stocks: 15 mg l−1 for superantigens and 2 mg l−1 for T-cell receptor β chain. These results contribute to the development of methods for microbial cell preservation under
field conditions.
Martín F. Desimone and Mauricio C. De Marzi contributed equally to this work 相似文献
2.
Lipopolysaccharide of Escherichia coli, polyamines, and acetic acid stimulate cell proliferation in intestinal epithelial cells 总被引:1,自引:0,他引:1
Jaime Olaya Vadim Neopikhanov Andrés Uribe 《In vitro cellular & developmental biology. Animal》1999,35(1):43-48
Summary Our aim was to examine whether lipopolysaccharide of Escherichia coli, polyamines of dietetic and/or bacterial origin, and products of the bacterial metabolism influence cell proliferation in
epithelial cells from the colon and small intestine. Lipopolysaccharide of Escherichia coli 0111:B4 was incubated with cultures from human colonic mucosa. The mitoses were arrested with Vincristine and the total number
of metaphases per crypt was counted. In addition, lipopolysaccharide was incubated with a human colonic epithelial cell line
from adenocarcinoma (LS-123 cells) and with a nontransformed small intestinal cell line from germ-free rats (IEC-6 cells)
for 24 h. In the last 4 h, the cells were labeled with tritiated thymidine. The cells were incubated with putrescine, cadaverine,
and spermidine at 10−11–10−3
M and with acetic acid (10−5–10−1
M), acetaldehyde (10−10–10−4
M) and ammonium chloride (1–20 mM). Lipopolysaccharide of Escherichia coli increased the number of arrested metaphases in human colonic crypts and DNA synthesis in L-123 and IEC-6 cells (P<0.001). All polyamines increased DNA synthesis in the colonic and small intestinal cell lines, the effects being more marked
for putrescine (P<0.001). The higher concentrations of acetic acid increased DNA synthesis in both epithelial cell lines (P<0.001). Acetaldehyde slightly decreased DNA synthesis in LS-123 cells at cytotoxic concentrations. Ammonium chloride did
not significantly affect DNA synthesis. The final concentration of nonionized ammonia was less than 3%. It is concluded that
lipopolysaccharides of Escherichia coli and intraluminal factors derived from microorganisms increase cell proliferation in human colonic crypts and intestinal epithelial
cell lines. 相似文献
3.
Farzana Ashrafi Neela L. Nonaka M. H. Rahman S. Suzuki 《World journal of microbiology & biotechnology》2009,25(6):1095-1101
The transferability of the tetracycline (TC) resistance gene tet(M) from marine bacteria to human enteric bacteria was examined by a filter-mating method. Vibrio spp., Lactococcus garvieae, Bacillus spp., Lactobacillus sp., and Paenibacillus sp. were used as donors, and Escherichia coli JM109 and Enterococcus faecalis JH2-2 were used as recipients. The combination of Vibrio spp. and E. coli resulted in 5/68 positive transconjugants with a transfer rate of 10−7 to 10−3; however, no transfer was observed with E. faecalis. In case of L. garvieae and E. faecalis, 6/6 positive transconjugants were obtained with a transfer rate of 10−6 to 10−5; however, no transfer was observed with E. coli. The tet(M) gene of Bacillus, Lactobacillus, and Paenibacillus were not transferred to either E. coli or E. faecalis. tet(M) transfer was confirmed in positive E. coli and E. faecalis transconjugants by polymerase chain reaction (PCR) and Southern hybridization. All the donor strains did not harbor plasmids,
while they all harbored transposon Tn916. In the transconjugants, the transposon was not detected by PCR, suggesting the possible transfer of tet(M) from the marine bacterial chromosome to the recipient chromosome. This is the first report to show that tet(M) can be transferred from marine bacteria to human enteric bacteria in a species-specific manner. 相似文献
4.
Kenji Kato Su-wan Oh Hiroyuki Yamamoto Takayuki Hanazato Ikuko Yasuda Akira Otuki Masayuki Takahashi 《Ecological Research》1992,7(3):267-276
In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted
in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the
different enclosures ranged from 1.2 to 2.7×107 cells mL−1 throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was
6.3×105 cells mL−1 h−1. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed
a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures
then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not
less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria
shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already
stocked in the water column, though it is not known whether the dominant bacteria were the same. 相似文献
5.
The bacteriostatic potency of the cerium-humic acid complex was evaluated by experimental measurement of this complex interaction
with E. coli, Bacillus pyocyaneus, Staphylococcus aureus, Leuconostoc and Streptococcus faecalis, and by comparison bacteriostatic effects with the cerium-citrate complex. The experimental results indicated that the cerium-humic
acid complex strongly inhibited growth of all five bacterial strains, and its diameter of bacteriostatic circles were more
than 30 mm. The minimal bacteria-inhibiting concentration were 1×10−3, 2×10−3 and 1×10−2 mol/L for E. coli and Bacillus pyocyaneus, Staphylococcus aureus, and Leuconostoc and Streptococcus faecalis individually, and the measured minimal bactericidal concentrations were 2×10−3 and 1×10−2 mol/L for Bacillus pyocyaneus, E. coli, and Leuconostoc. To kill Staphylococcus aureus and Streptococcus faecalis, the concentration had to be more than 1×10−2 mol/L. On the contrary, we found that cerium-citrate complex did not inhibit the growth of the above five bacteria, but stimulated
bacterial growth. The completely different bacteriostatic results of two cerium complexes may hint that the association and
chemical properties of the two complexes were different. 相似文献
6.
Various measurements of microbial productivity in streambed pebble biofilms were analyzed almost monthly for 1 year to quantify the importance of primary production as an autochthonous source of organic matter utilized to support heterotrophic bacterial production in the dynamic food web within this natural microbial habitat. Bacterial density varied from 0.3 × 108 to 1.4 × 108 cells cm−2, and chlorophyll a concentration ranged from 0.7 to 25.9 μg cm−2, with no coupled oscillation between seasonal changes in these two parameters. In bottle incubation experiments, the instantaneous bacterial growth rate of bacteria was significantly correlated with their production rate [measured by frequency of dividing cells (FDC)] as follows: ln μ = 0.138FDC − 3.003 (n = 15, r
2 = 0.445, p < 0.001). FDC values in the pebble biofilms increased with fluctuations during the study period, ranging from 3.6% to 9.2%. Bacterial production rates largely fluctuated between 0.15 to 0.92 μg C cm−2 h−1, and its seasonal pattern was similar to that of bacterial density. Net primary production measured between May 2002 to November 2002 attained minimum level (0.5 μg C cm−2 h−1) in June and maximum level (1.9 μg C cm−2 h−1) in August. Percentages of bacterial production to net primary production ranged between 21% and 120%. Because this ratio extends both below and above 100% for these parameters, it is likely that both autochthonous and allochthonous supplies of organic matter are important for production of bacteria in the pebble biofilms that develop in rapidly flowing fresh water streams. 相似文献
7.
Mineralization of diuron has not been previously demonstrated despite the availability of some bacteria to degrade diuron
into 3,4-dichloroaniline (3,4-DCA) and others that can mineralize 3,4-DCA. A bacterial co-culture of Arthrobacter sp. N4 and Delftia acidovorans W34, which respectively degraded diuron (20 mg l−1) to 3,4-DCA and mineralized 3,4-DCA, were able to mineralize diuron. Total diuron mineralization (20 mg l−1) was achieved with free cells in co-culture. When the bacteria were immobilized (either one bacteria or both), the degradation
rate was higher. Best results were obtained with free Arthrobacter sp. N4 cells co-cultivated with immobilized cells of D. acidovorans W34 (mineralization of diuron in 96 h, i.e., 0.21 mg l−1 h−1 vs. 0.06 mg l−1 h−1 with free cells in co-culture). 相似文献
8.
Abstract
The investigation of the bacterial community in the Kühw?rter Wasser, a macrophyte-dominated arm of the River Danube backwater
system near Vienna, revealed that variation in microbial densities and biomass could be related to a characteristic sequence
in morphotype composition over the seasons. Maximal bacterial cell numbers and biomass occured in early summer, with values
of up to 9 × 109 cells l−1 and 122 μg C l−1, respectively, caused by a massive increase of vibrio-shaped cells. On the other hand, in early spring, filamentous bacteria
were responsible for a marked increase in bacterial biomass, making up 40% of the total bacterial biomass. Over the year,
rod-shaped cells were the dominating morphotype, while the biomass of cocci was rather negligible. In winter, cell numbers
and biomass showed minimal values with 2.0 × 109 cells l−1 and 28 μg C l−1, respectively, and bacteria were considered to be substrate and temperature limited during this period. Saturation values
of the incorporation of 3H-thymidine into DNA, for the estimation of bacterial secondary production, varied seasonally, ranging from 5 nm to 40 nm. Thus, saturation experiments needed to be conducted on a regular basis. Also, the amount of labeled thymidine in the DNA,
as a percentage of labeled thymidine in the TCA precipitate, varied over the year. Minimum values of 45% were recorded during
the cold season, while maximum values of 75–80% at the beginning of June coincided with high chlorophyll a values and minimal K
m-values derived from saturation experiments. The potential role of the nitrogen-rich nucleoside thymidine as a readily utilizable
substrate for bacteria during labeling experiments, under varying conditions of substrate availability, is discussed. Bacterial
secondary production rates ranged from 0.3 μg C l−1 h−1 in winter to values of 10 μg C l−1 h−1 in August, where phytoplanktonic biomass reached the summer maximum, and bacterial biomass was calculated to be renewed 3
times per day. An estimation of the bacterial carbon demand showed that for the major part of the year, with the exception
of early spring, the bacterioplankton community in the Kühw?rter Wasser was dependent on carbon sources other than phytoplanktonic
primary production.
Received: 22 March 1996; Revised: 1 August 1996 相似文献
9.
Abstract
Bacterial abundance and bacterivorous protist abundance and activity were examined in ice-brine and water column communities
of a cold temperate Japanese lagoon (Saroma-Ko Lagoon, Hokkaido, 44°N, 144°E), during the late winter phase of ice community
development (February–March 1992). Bacterial abundance averaged 6 and 1 × 105 cells ml−1 in the ice-brine and plankton samples, respectively, and generally decreased during the sampling period. Bacterivorous protists,
identified based on direct observation of short-term (<1 h) ingested fluorescently labeled bacteria (FLB) in their food vacuoles,
were largely dominated by flagellates, mainly cryothecomonad-type and chrysomonad-like cells and small dinoflagellates of
the genus Gymnodinium. Bacterivorous ciliates included mainly the prostomatid Urotricha sp., the scuticociliates Uronema and Cyclidium, the choreotrichs Lohmaniella oviformis and Strobilidium, and the hypotrich Euplotes sp. Protist abundance averaged 4 × 103 and 8.1 cells ml−1 in the ice-brine and 0.3 × 103 and 1.2 cells ml−1 in the plankton, for flagellates and ciliates, respectively. In contrast to bacteria, the abundance of protists generally
increased throughout the sampling period, indicating predator–prey interactions. Protistan bacterivory, measured from the
rate of FLB disappearance over 24 h, averaged 36% (ice) and 24% (plankton) of bacterial standing stock and exhibited the same
seasonal pattern as for protist abundance. The calculated specific clearance (range, 2–67 nl protozoa−1 h−1) and ingestion (<1–26 particles protozoa−1 h−1) rates were likely to be minimal estimates and grazing impact may have been higher on occasion. Indications for the dependence
of ``bacterivorous protists' on nonbacterial food items were also provided. Although alternative sources of bacterial loss
are likely to be of importance, this study provides evidence for the potential of protozoan assemblages as bacterial grazers
in both sea ice-brine biota and water column at the southern limit of sea ice in the northern hemisphere.
Received: 30 July 1998; Accepted: 18 November 1998 相似文献
10.
Huang Shan Chen Chen Wu Yanyang Wu Qunhe Zhang Renduo 《World journal of microbiology & biotechnology》2011,27(11):2655-2664
To better understand the bacterial processes in river sediments, it is necessary to investigate the depth-related bacterial
communities in the whole sediment profile. Sediment samples were collected to a depth of 25 cm from the Pearl River. Bacterial
abundance, activity, cell-specific respiration rate, and diversity were measured, respectively, by 4′, 6-diamidino-2-phenylindole
direct count, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining, electron transport system by CTC reduction, and denaturing
gradient gel electrophoresis analysis of 16S rRNA amplification fragments. Results showed that the bacterial metabolism activities
decreased with the sediment depth. The total bacterial abundance was highest in the surface sediment with 65.1 × 107 cells g−1, and decreased to 11.1 × 107 cells g−1 below 20 cm in the sample location that suffered from heavy sewage inputs. The active bacteria accounted for 7.50–46.7% of
the total bacterial number and decreased with the sediment depth. Electron transport system by the CTC reduction showed that
bacterial respiration rate declined from 1.093 μmol CTC-formazan h−1 g−1 in the surface sediment to a half in the bottom sediment, while the cell-specific respiration increased significantly with
the depth from 3.56 to 93.75 fmol CTC-formazan cell−1. The bacterial diversity also changed with the depth. Beta-Proteobacteria were the dominant species in the surface sediment,
whereas Delta-Proteobacteria were the main species below 10 cm. Results of canonical correspondence analysis (CCA) indicated
that the distribution of bacteria was affected by the combined effect of various dissolved inorganic matter, while the respiration
rate was independent of the nutrient conditions. The specific bacterial distribution contributed to not only the nutrient
cycle but also enhanced pollutant decomposition in sediment of the Pearl River. The results showed that some specific bacterial
species had a strong activity in the deeper layers. Therefore, the metabolic functions of the deeper bacterial species should
not be neglected. 相似文献
11.
Filipa Antunes Mariana Hinzmann Manuel Lopes-Lima Jorge Machado Paulo Martins da Costa 《Microbial ecology》2010,60(2):304-309
Bivalves filter and accumulate large numbers of microorganisms present in the harvesting water. A complete understanding of
the balance between Anodonta cygnea and the microbiota present in their surrounding environment remains incomplete. Therefore, the aim of this study was to quantify
and identify the indigenous bacteria in the biological fluids of A. cygnea collected from Mira Lagoon in northern Portugal. The results showed Vibrio metschnikovii and Aeromonas sobria as the dominant groups. The median for total bacteria from mucus was 3.1 × 103 CFU g−1, whereas the range in means from fluids was 1.5 × 102 to 6.5 × 102 CFU ml−1. During the experimental work, Escherichia coli and enterococci were not detected in healthy A. cygnea. However, the periodic detection of E. coli and enterococci in Mira lagoon revealed its presence in the water. Our observations suggest that A. cygnea has the ability to filter and eliminate E. coli, present in the surrounding environment, through an active phagocytic process conducted by hemolymph circulating cells, the
hemocytes. 相似文献
12.
Anna Vacheva Ralitsa Georgieva Svetla Danova Radka Mihova Mariana Marhova Sonia Kostadinova Krasimira Vasileva Maria Bivolarska Stoyanka R. Stoitsova 《Central European Journal of Biology》2012,7(2):219-229
E. coli biofilms cause serious problems in medical practice by contaminating surfaces and indwelling catheters. Due to the rapid
development of antibiotic resistance, alternative approaches to biofilm suppression are needed. This study addresses whether
products released by antagonistic bacteria — Lactobacillus isolates from vaginal and dairy-product samples could be useful for controlling E. coli biofilms. The effects of diluted cell-free supernatants (CFS) from late-exponential Lactobacillus cultures on the growth and biofilm production of Escherichia coli were tested. Most of the CFS applied as 10−2 had no impact on bacterial growth, biofilm development however was influenced even by 10−4 of CFS. Initial screening by crystal violet assay showed that biofilm modulation varied between different CFS and E. coli combinations from inhibition to activation; however three of the tested CFS showed consistency in biofilm suppression. This
was not due to antibacterial activity since Live/Dead fluorescence labeling showed insignificant differences in the amount
of dead cells in control and treated samples. Some E. coli strain-specific mechanisms of response to the three CFS included reduction in hydrophobicity and motility. Released exoploysaccharides
isolated from the three CFS stimulated sessile growth, but proteinase K reduced their inhibitory activities implying participation
of protein or peptide biofilm suppression factor(s). 相似文献
13.
14.
Influence of the Hydrological Cycle on the Bacterioplankton of an Impacted Clear Water Amazonian Lake 总被引:4,自引:0,他引:4
Abstract
Free-living and attached bacterial population sizes were determined fortnightly from December 1991 to December 1992 in natural
and disturbed areas of an Amazonian clear water lake (Batata Lake, Pará, Brazil) impacted by bauxite tailings. The bacterioplankton
showed distinct patterns during different phases of the hydrological cycle. Total bacterial population size and rates of thymidine
incorporation (measured during high and low water phases) were high during low water, with values ranging from 3.3 × 105 to 1.1 × 106 cells ml−1, and from 0.28 to 4.01 μg C l−1 h−1, respectively. The population size of free-living bacteria was larger at the natural station, while no differences were observed
between attached bacterial populations at both stations. However, production and turnover rate of attached bacteria were high
at the disturbed area. During low water, bacterial growth appeared to be driven mainly by the input of dissolved organic carbon
(DOC) from phytoplankton origin. During high water, bacterial abundance was reduced, probably as the result of dilution and
the input of less labile DOC from floodplains. The presence of bauxite tailings seems to influence bacterial dynamics in an
indirect way, probably due to shading of phytoplankton cells and, hence, reducing the DOC supply for bacterial growth. This
study, the first on the microbial ecology of an Amazonian clear water lake, demonstrated that water level variations exert
a strong influence on the bacterioplankton dynamics.
Received: 9 January 1996; Accepted 6 November 1996 相似文献
15.
Phylogenetic and Physiological Diversity of Bacteria Isolated from Puruogangri Ice Core 总被引:2,自引:0,他引:2
The microbial abundance, the percentage of viable bacteria, and the diversity of bacterial isolates from different regions
of a 83.45-m ice core from the Puruogangri glacier on the Tibetan Plateau (China) have been investigated. Small subunit 16S
rRNA sequences and phylogenetic relationships have been studied for 108 bacterial isolates recovered under aerobic growth
conditions from different regions of the ice core. The genomic fingerprints based on ERIC (enterobacterial repetitive intergenic
consensus)-polymerase chain reaction and physiological heterogeneity of the closely evolutionary related bacterial strains
isolated from different ice core depths were analyzed as well. The results showed that the total microbial cell, percentages
of live cells, and the bacterial CFU ranged from 104 to 105 cell ml−1 (Mean, 9.47 × 104; SD, 5.7 × 104, n = 20), 25–81%, and 0–760 cfu ml−1, respectively. The majority of the isolates had 16S rRNA sequences similar to previously determined sequences, ranging from
92 to 99% identical to database sequences. Based on their 16S rRNA sequences, 42.6% of the isolates were high-G + C-content
(HGC) gram-positive bacteria, 35.2% were low-G + C (LGC) gram-positive bacteria, 16.6% were Proteobacteria, and 5.6% were CFB group. There were clear differences in the depth distribution of the bacterial isolates. The isolates
tested exhibited unique phenotypic properties and high genetic heterogeneity, which showed no clear correlation with depths
of bacterial isolation. This layered distribution and high heterogeneity of bacterial isolates presumably reflect the diverse
bacterial sources and the differences in bacteria inhabiting the glacier’s surface under different past climate conditions. 相似文献
16.
G. I. Karavaiko T. F. Kondrat’eva E. E. Savari N. V. Grigor’eva Z. A. Avakyan 《Microbiology》2000,69(2):167-173
The role played by a bacterial community composed ofPseudomonas putida, strain 21;Pseudomonas stutzeri, strain 18; andPseudomonas sp., strain 5, and by physical and chemical factors in the degradation of CN− and SCN− was studied. It was shown that the degradation of CN− is determined both by the action of bacteria and by abiotic physical and chemical factors (pH, O2, temperature, the medium agitation rate, etc.). The contribution of chemical degradation was found to increase drastically
at pH below 9.0; when air was blown through the medium (irrespective of the pH value); under active agitation of the medium;
and when the medium surface interfacing air was increased. Even at elevated pH values (9.0-9.2), suboptimal for bacterial
growth, the microbial degradation could account for at most 20–25 mg/1 of CN−, regardless of its initial concentration. When CN− and SCN− were concurrently present in the medium, the former compound was the first to be degraded by microorganisms. The rate of
bacterial degradation of SCN− under continuous cultivation in a chain of reactors was found to depend on its concentration, the medium flow rate, agitation
rate, and the pattern of carbon source supply and could exceed 1 g/(l day). CN− and SCN− are utilized by bacteria solely as nitrogen sources. The mechanism of CN− and SCN− degradation by the microbial community is discussed.
Deceased. 相似文献
17.
Olesja Bondarenko Pattanathu K. S. M. Rahman Thahira J. Rahman Anne Kahru Angela Ivask 《Microbial ecology》2010,59(3):588-600
In this study, the mixture of mono- and di-rhamnolipids produced by Pseudomonas aeruginosa DS10-129 was characterized for its toxicity and modulatory effects on Cd availability to different bacteria. Gram-negative
naturally bioluminescent Vibrio fischeri and recombinant bioluminescent Pseudomonas fluorescens, P. aeruginosa, Escherichia coli, and Gram-positive Bacillus subtilis were used as model organisms. Rhamnolipids reduced the bioluminescence of these bacteria in less than a second of exposure
even in relatively low concentrations (30-min EC50 45–167 mg l−1). Toxicity of Cd to Gram-negative bacteria (30-min EC50 values 0.16 mg l−1 for E. coli, 0.96 mg l−1 for P. fluorescens, and 4.4 mg l−1 for V. fischeri) was remarkably (up to 10-fold) reduced in the presence of 50 mg l−1 rhamnolipids. Interestingly, the toxicity of Cd to Gram-positive B. subtilis (30-min EC50 value 0.49 mg l−1) was not affected by rhamnolipids. Rhamnolipids had an effect on desorption of Cd from soil: 40 mg l−1 rhamnolipids increased the water-extracted fraction of Cd twice compared with untreated control. However, this additionally
desorbed fraction of Cd remained bound with rhamnolipids and was not available to bacteria. Hence, in carefully chosen concentrations
(still effectively complexing heavy metals but not yet toxic to soil bacteria), rhamnolipids could be applied in remediation
of polluted areas. 相似文献
18.
Biodegradation of nonylphenol in a continuous bioreactor at low temperatures and effects on the microbial population 总被引:6,自引:0,他引:6
A packed-bed bioreactor inoculated with a mixed culture obtained from a contaminated site was used to continuously treat a
saturated solution of nonylphenol. The reactor was operated at feeding rates of 13–112 ml h−1 and temperatures of 5.5, 10, and 15°C. Optimal bioreactor performance was achieved at 10°C and at a feeding rate of 84 ml
h−1 (with a removal rate of 43 mg l−1 day−1 of nonylphenol). No endocrine activity was observed in the effluent of the bioreactor at any of the temperatures tested,
and the only metabolic products found were branched carboxylic acids and alkanes (lacking an aromatic ring). The study of
the microbial populations in the biofilm at the three temperatures tested using fluorescence in situ hybridization showed
that all the bacterial species that could be identified belonged to the phylum Proteobacteria. The most abundant class identified at all three temperatures was β-Proteobacteria. The proportions of bacteria that bound to the specific probes among the total population, identified with the bacterial
probe EUB338MIX, were 60, 43, and 24% at 15, 10, and 5.5°C, respectively. 相似文献
19.
Alves E Carvalho CM Tomé JP Faustino MA Neves MG Tomé AC Cavaleiro JA Cunha A Mendo S Almeida A 《Journal of industrial microbiology & biotechnology》2008,35(11):1447-1454
A faster and simpler method to monitor the photoinactivation process of Escherichia coli involving the use of recombinant bioluminescent bacteria is described here. Escherichia coli cells were transformed with luxCDABE genes from the marine bioluminescent bacterium Vibrio fischeri and the recombinant bioluminescent indicator strain was used to assess, in real time, the effect of three cationic meso-substituted porphyrin derivatives on their metabolic activity, under artificial (40 W m−2) and solar irradiation (≈620 W m−2). The photoinactivation of bioluminescent E. coli is effective (>4 log bioluminescence decrease) with the three porphyrins used, the tricationic porphyrin Tri-Py+-Me-PF being the most efficient compound. The photoinactivation process is efficient both with solar and artificial light,
for the three porphyrins tested. The results show that bioluminescence analysis is an efficient and sensitive approach being,
in addition, more affordable, faster, cheaper and much less laborious than conventional methods. This approach can be used
as a screening method for bacterial photoinactivation studies in vitro and also for the monitoring of the efficiency of novel
photosensitizer molecules. As far as we know, this is the first study involving the use of bioluminescent bacteria to monitor
the antibacterial activity of porphyrins under environmental conditions. 相似文献
20.
Abstract
If predators select for or against contaminant-degrading bacteria, it will affect bacterial survival and has important implications
for bioremediation. Protozoa are important predators of bacteria. In order to determine whether protozoa preyed differentially
on bacteria with different degradation abilities, two ciliates (Euplotes sp. and Cyclidium sp.) and three strains of PAH-degrading bacteria (Vibrio spp., degrading naphthalene, anthracene, or phenanthrene) were isolated from sediment from New York/New Jersey Harbor. By
manipulating growth conditions, bacterial strains with different PAH-degradation abilities and different cell properties were
produced. Stepwise regression models were used to analyze how clearance rates on suspended bacteria and grazing rates on bacteria
attached to particles were affected by bacterial size, hydrophobicity, C:N ratio, protein content, and PAH-degradation ability.
Clearance rates ranged from 0 to 49 nl ciliate−1 h−1 for Euplotes sp. and from 0 to 1.7 nl ciliate−1 h−1 for Cyclidium sp. Clearance rates of both ciliates were positively correlated with bacterial size, hydrophobicity, and protein content,
and negatively correlated with C:N ratio. PAH degradation ability had no (for Euplotes sp.) or small (for Cyclidium sp.) effects on clearance rates. The models accounted for 63–75% of the variation in clearance rates on different bacteria.
Only Euplotes sp. grazed on attached bacteria, at rates from 3 to 176 bacteria ciliate−1 h−1. A regression model with only C:N ratio and protein content explained 45% of the variation in grazing rates. These models
indicate that multiple properties of bacteria affect their susceptibility to predation by ciliates, but PAH-degradation ability
per se has little effect.
Received: 5 May 1998; Accepted: 14 September 1998 相似文献