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1.
This study was undertaken to explore the role of Trichoderma sp. in phosphate (P) solubilization and antagonism against fungal phytopathogens. All fungal isolates (SE6, KT6, KT28, and BRT11) and a standard culture of T. harzianum (Th-std) were able to antagonize two fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea (Cicer arietinum L.) wilt complex. Transmission electron microscopic studies (TEM) further confirmed ultra-cytological changes in the sclerotia
of S. rolfsii parasitized by Trichoderma sp. All fungal cultures exhibited production of NH3 and siderophore, but only BRT11, SE6, and Th-std could produce HCN. Among all the cultures tested, isolate KT6 was found to be most effective for solubilization of ferric phosphate releasing 398.4 μg ml−1 phosphate while isolates BRT11 and SE6 showed more potential for tricalcium phosphate (TCP) solubilization releasing 449.05 and 412.64 μg ml−1 phosphate, respectively, in their culture filtrates. Part of this study focused on the influence of abiotic stress conditions
such as pH, temperature, and heavy metal (cadmium) on phosphate (TCP) solubilizing efficiency. Two selected cultures KT6 and T. harzianum retained their P solubilizing potential at varying concentrations of cadmium (0–1000 μg ml−1). Isolate KT6 and standard culture of T. harzianum released 278.4 and 287.6 μg ml−1 phosphate, respectively, at 1000 μg ml−1cadmium. Maximum solubilization of TCP was obtained at alkaline pH and at 28°C temperature. Isolate BRT11 was found most alkalo-tolerant releasing 448.0 μg ml−1 phosphate at pH 9. 相似文献
2.
N. J. Silk S. Denby G. Lewis M. Kuiper D. Hatton R. Field F. Baganz Gary J. Lye 《Biotechnology letters》2010,32(1):73-78
Recently we have demonstrated batch suspension culture of mammalian cells in microwell plates. Here we describe a method for
fed-batch culture of an industrially relevant GS-CHO (Glutamine Synthetase-Chinese Hamster Ovary) cell line in shaken 24-standard
round well (24-SRW) plates. Use of a commercially available ‘sandwich lid’ and appropriate dilution of the bolus feeds counteracted
liquid evaporation from the wells resulting in similar cell growth and antibody formation kinetics in both 24-SRW plates (800 μl)
and shaken flasks (50 ml). Peak viable cell densities obtained were 8 ± 0.5 × 106 and 9 ± 1.3 × 106 ml−1, respectively, while comparable final titres of a whole IgG of approximately 1.5 g l−1 were recorded. Use of microwells provides at least a 50-fold reduction in medium requirements compared to shake-flask and
other culture devices currently used in early stage cell culture process development. The ability to run multiple wells in
parallel and to automate culture operation also offers considerable enhancements in experimental throughput. 相似文献
3.
The in vitro cytotoxicity of the antimicrobial peptide P40 was investigated. The food grade bacteriocin nisin was also analyzed
for comparison. VERO cells were treated with different concentrations (0.02–2.5 μg ml−1) of nisin and P40, and cell viability and plasma membrane integrity were checked by MTT, neutral red uptake (NRU), and lactate
dehydrogenase (LDH) assays. In MTT and NRU assays the EC50 to the purified peptide P40 were 0.30 and 0.51 μg ml−1, while values found to nisin were 0.35 and 0.79 μg ml−1, respectively. In the LDH assay, the EC50 was 0.57 and 0.62 μg ml−1 for P40 and nisin, respectively. The peptide P40 revealed higher hemolytical activity (19%) when compared to nisin (4.9%)
at the highest concentration tested (2.5 μg ml−1). Relatively few studies about the cytotoxicity of antimicrobial peptides are available. The determination of the cytotoxicity
of antimicrobial peptides is an essential step to warrant their safe use. 相似文献
4.
Mukunda Goswami Wazir S. Lakra T. Rajaswaminathan Gourav Rathore 《Molecular biology reports》2010,37(4):2043-2048
A new cell culture system (MRH) was developed for the first time from 2 months old freshwater prawn, Macrobrachium rosenbergii. Primary cultures were developed from heart tissues by explant culture technique. Cell outgrowth was obtained from the heart
explant after 14 days of explant culture. The culture medium used was Leibovitz-15 supplemented with 20% Fetal Bovine Serum
along with 1% prawn hemolymph serum, 0.1% glucose, 0.5% NaCl and antibiotics (Penicillin 10,000 Units ml−1, Streptomycin 10,000 μg ml−1, Amphotericin B 500 mg ml−1) with a final osmomolality of 470–550 mmol kg−1. The pH of the growth medium found suitable for the growth of the cells was 7.20. The viability of cells was found to be
60% when revived after a month of storage in liquid nitrogen. 相似文献
5.
Plant gum as an elicitor for guggulsterone production in cell cultures of Commiphora wightii is reported for the first time. Guggulsterone production increased 2.4 fold in the cell cultures by gum Arabic (100 mg l−1), while mesquite gum elicited 2 fold. The cells treated with gum Arabic at 7th and 9th day accumulated enhanced guggulsterones
within 24 h, which increased further up to 48 h and then declined. The cells treated at 9th day accumulated higher amount
(218 μg l−1) of guggulsterones after 48 h of elicitation as compared to cells treated at 7th day (164 μg l−1). The optimized elicitation conditions were used in vessels of varying capacity where maximum yield of 285 μg l−1 of guggulsterones was recorded in 3 l shake flasks. These experiments enabled highest guggulsterones yield in a short duration
of 11 days in cell cultures of C. wightii. 相似文献
6.
C. K. Deepa Syed G. Dastager Ashok Pandey 《World journal of microbiology & biotechnology》2010,26(12):2277-2283
A Gram-positive rod-shaped bacterium isolated on nutrient agar plates incubated at 28 ± 2°C. The identity of the bacterium
was confirmed by sequencing of the 16S rRNA gene and it reveals that it shares highest similarity with Bacillus thioparus CECT 7196T (99.08%). It was capable of growing at temperatures ranging from 4 to 40°C, but optimum growth was observed at 28 ± 2°C.
Strain NII-0902 is endowed with multiple plant growth promotion attributes such as phosphate solubilization, Indole acetic
acid (IAA), siderophore and HCN production, which were expressed differentially at sub-optimal temperatures (5–40°C). It was
able to solubilize phosphate (17.7 μg ml−1), and produce IAA (139.7 μg ml−1) at 28 ± 2°C. Qualitative detection of siderophore production and HCN were also observed. At 5°C it was found to express
all the plant growth promotion attributes except HCN production. The ability to colonize roots is a sine qua non condition
for a rhizobacteria to be considered a true plant growth-promoting rhizobacteria (PGPR). Bacillus sp. NII-0902 has a potential ability to colonize roots visualized by transparency, bacterial growth (turbid, milky and narrow
zone) along and around roots and truly supported by scanning electron micrograph. Hence, it is proposed that, Bacillus thioparus sp. NII-0902 could be deployed as an inoculant to attain the desired results of bacterization. 相似文献
7.
The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and
in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates
dominated the algal biomass (226 ± 154 μg ww l−1) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l−1). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25
and 21 ± 14 μg ww l−1, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical
cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest
chlorophyll-a concentrations (6.6–22.2 μg l−1) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional
peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a
−1 h−1) (μE m−2 s−1)−1] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a
−1 h−1)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced
the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients
and possibly habitable space, which seemed to have favored centric diatoms in our study. 相似文献
8.
Sachin Kumar Surendra P. Singh Indra M. Mishra Dilip K. Adhikari 《Journal of industrial microbiology & biotechnology》2009,36(12):1483-1489
A yeast strain Kluyveromyces sp. IIPE453 (MTCC 5314), isolated from soil samples collected from dumping sites of crushed sugarcane bagasse in Sugar Mill,
showed growth and fermentation efficiency at high temperatures ranging from 45°C to 50°C. The yeast strain was able to use
a wide range of substrates, such as glucose, xylose, mannose, galactose, arabinose, sucrose, and cellobiose, either for growth
or fermentation to ethanol. The strain also showed xylitol production from xylose. In batch fermentation, the strain showed
maximum ethanol concentration of 82 ± 0.5 g l−1 (10.4% v/v) on initial glucose concentration of 200 g l−1, and ethanol concentration of 1.75 ± 0.05 g l−1 as well as xylitol concentration of 11.5 ± 0.4 g l−1 on initial xylose concentration of 20 g l−1 at 50°C. The strain was capable of simultaneously using glucose and xylose in a mixture of glucose concentration of 75 g l−1 and xylose concentration of 25 g l−1, achieving maximum ethanol concentration of 38 ± 0.5 g l−1 and xylitol concentration of 14.5 ± 0.2 g l−1 in batch fermentation. High stability of the strain was observed in a continuous fermentation by feeding the mixture of glucose
concentration of 75 g l−1 and xylose concentration of 25 g l−1 by recycling the cells, achieving maximum ethanol concentration of 30.8 ± 6.2 g l−1 and xylitol concentration of 7.35 ± 3.3 g l−1 with ethanol productivity of 3.1 ± 0.6 g l−1 h−1 and xylitol productivity of 0.75 ± 0.35 g l−1 h−1, respectively. 相似文献
9.
Hari Datta Bhattarai Viswanadh Sarma Ganti Babita Paudel Yoo Kyung Lee Hong Kum Lee Yong-Ki Hong Hyun Woung Shin 《World journal of microbiology & biotechnology》2007,23(2):243-249
Two compounds, 2-hydroxymyristic acid (HMA) and cis-9-oleic acid (COA), were isolated from a chloroform extract of the marine
bacterium, Shewanella oneidensis SCH0402. In a spectrophotometer-based chemotaxis assay, HMA completely eliminated the optical density (OD) of Alteromonas marina SCH0401 and Bacillus atrophaeus SCH0408, motile, fouling bacteria, at 100 and 1000 μg ml−1, respectively. COA similarly decreased the OD of A. marina and B. atrophaeus by 100% at 1000 μg ml−1. The commercially available, highly toxic anti-fouling compound, tributyltin oxide (TBTO) never reduced the OD of the target
bacteria by 100% even at higher concentration. Instead, all the test bacterial cells were killed at higher than 1000 μg ml−1 of concentration. Both HMA and COA inhibited germination of Ulva pertusa spores completely at 10 and 100 μg ml−1, respectively, while TBTO inhibited germination at 0.01 μg ml−1. However, in field assays, both HMA and COA showed anti-fouling activities as potent as TBTO against a wide range of fouling
organisms, including micro- and macro-algae, barnacles, and mussels. The average fouling coverage on the surface of the control
panel was 93 ± 6% after 1.5 years but no fouling was observed on the surface of the test panel onto which each compound was
applied separately. Thus, bacterial repellent compounds can be used as substitutes for potent toxic anti-fouling compounds,
resulting in higher standards of environmental safety without loss of anti-fouling performance. 相似文献
10.
Plant regeneration through somatic embryogenesis was achieved using immature zygotic embryos (ZE) of Sorbus pohuashanensis as explants. Over 50% of immature ZEs from immature seed collected at 30 days after pollination produced direct somatic embryos
(SEs) on Murashige and Skoog (MS) medium supplemented with 0–0.44 μM 6-benzyladenine (BA) in combination with 5.73 μM naphthaleneacetic
acid (NAA) or with 0.91–2.26 μM 2,4-dichlorophenoxyacetic acid (2,4-D) alone. Fourteen to 23 SEs per explant were regenerated
on MS medium supplemented with BA 0.44 μM in combination with NAA 5.73 μM. SE formation decreased when sucrose concentrations
were higher than 40 g L−1. Repetitive embryogenesis occurred following culture on solid MS medium containing 12 μM abscisic acid, 75 g L−1 polyethylene glycol, and 20 g L−1 sucrose at 25 ± 1°C under a 16-h photoperiod with a light intensity of 40 μmol m−2 s−1. Over 40% of the mature SEs germinated on solid MS medium under light condition described previously. Up to 40% of the regenerated
plantlets were successfully acclimatized under greenhouse conditions. Plantlets derived from SEs grew vigorously with similar
morphology as those germinated from ZEs. Histological studies of explants at various developmental stages of somatic embryogenesis
revealed that SEs passed through globular, heart, torpedo, and mature stages. Similar to ZE suspensors, similar structures
of SE degenerated in later stages of embryo development. ZE and SE are a effective means of regenerating tissue culture plantlets
for S. pohuashanesis. 相似文献
11.
Xianqing Huang Yufen Wang Yanhong Cui Xie Hua 《International journal of peptide research and therapeutics》2010,16(2):63-69
In the paper, the sensitivity of Penicillium notatum to surfactin and iturin was determined, and the optimization of the antifungal of surfactin and iturin to Penicillium notatum in syrup of peach by a response surface methodology (RSM) was researched. Results demonstrated that Penicillium notatum was sensitive to them, whose minimal inhibitory concentration (MIC) was 62.5 and 31.25 μg ml−1 respectively. In the optimization experiment, when the temperature was 2.37°C, the action time was 25.21 h, and the concentration
(surfactin/iturin weight ratio 1:1) was 40.26 μg ml−1, Penicillium notatum could be sterilized by 5 orders of magnitude. All the results in the experiment indicated surfactin and iturin could kill
remarkably Penicillium notatum in syrup of peach. 相似文献
12.
The changes in foliar concentrations of volatile terpenes in response to water stress, fertilization and temperature were
analyzed in Pinus halepensis and Quercus ilex. The most abundant terpenes found in both species were α-pinene and Δ3-carene. β-Pinene and myrcene were also abundant in both species. P. halepensis concentrations were much greater than those of Q. ilex in agreement with the lack of storage in the latter species (15205.60 ± 1140.04 vs. 0.54 ± 0.08 μg g−1 [d.m.]). The drought treatment (reduction to 1/3 of full watering) significantly increased the total terpene concentrations
in both species (54% in P. halepensis and 119% in Q. ilex). The fertilization treatment (addition of either 250 kg N ha−1 or 250 kg P ha−1 or both) had no significant effects on terpene foliar concentrations. The terpene concentrations increased from 0.25 μg g−1 [d.m.] at 30°C to 0.70 μg g−1 [d.m.] at 40°C in Q. ilex (the non-storing species) and from 2,240 μg g−1 [d.m.] at 30°C to 15,621 μg g−1 [d.m.] at 40°C in P. halepensis (the storing species). Both species presented negative relationship between terpene concentrations and relative water contents
(RWC). The results of this study show that higher terpene concentrations can be expected in the warmer and drier conditions
predicted for the next decades in the Mediterranean region. 相似文献
13.
Buatong Jirayu Phongpaichit Souwalak Rukachaisirikul Vatcharin Sakayaroj Jariya 《World journal of microbiology & biotechnology》2011,27(12):3005-3008
The aim of this work was to select endophytic fungi from mangrove plants that produced antimicrobial substances. Minimal inhibitory
concentrations (MIC) and minimal bactericidal concentrations (MBC) or minimal fungicidal concentrations (MFC) of crude extracts
from 150 isolates were determined against potential human pathogens by a colorimetric microdilution method. Ninety-two isolates
(61.3%) produced inhibitory compounds. Most of the extracts (28–32%) inhibited Staphylococcus aureus (MIC/MBC 4–200/64–200 μg ml−1). Only two extracts inhibited Pseudomonas aeruginosa (MIC/MBC 200/>200 μg ml−1). 25.5 and 11.7% inhibited Microsporum gypseum and Cryptococcus neoformans (MIC/MFC 4–200/8–200 μg ml−1 and 8–200/8–200 μg ml−1, respectively), while 7.5% were active against Candida albicans (MIC/MFC 32–200/32–200 μg ml−1). None of the extracts inhibited Escherichia coli. The most active fungal extracts were from six genera, Acremonium, Diaporthe, Hypoxylon, Pestalotiopsis, Phomopsis, and Xylaria as identified using morphological and molecular methods. Phomopsis sp. MA194 (GU592007, GU592018) isolated from Rhizophora apiculata showed the broadest antimicrobial spectrum with low MIC values of 8–32 μg ml−1against Gram-positive bacteria, yeasts and M. gypseum. It was concluded that endophytic fungi from mangrove plants are diverse, many produce compounds with antimicrobial activity
and could be suitable sources of new antimicrobial natural products. 相似文献
14.
Abhishek Tripathi Neeta Sharma Vinay Sharma 《World journal of microbiology & biotechnology》2009,25(3):503-512
Hyptis
suaveolens L. (Poit.) essential oil was tested in vitro on the growth and morphogenesis of Fusarium oxysporum f.sp. gladioli (Massey) Snyder & Hansen, which causes Fusarium corm rot and yellows in various susceptible cultivars of gladiolus. The fungitoxicity of the oil was measured by percentage radial growth inhibition using the poisoned food technique (PF)
and volatile activity assay (VA). The mycelial growth of the test fungus was completely inhibited at 0.998 and 0.748 μg ml−1 concentration of oil in PF and VA, respectively. Essential oil was found to be fungicidal in nature at 1.247 and 0.998 μg ml−1 concentration of oil in PF and VA, respectively. Determination of conidial germination in the presence of oil was also carried
out and it was found that the oil exhibited 100% inhibition of conidial germination at 0.450 μg ml−1 concentration. The effect of essential oil on the yield of mycelial weight was observed and it was found that at 0.873 μg ml−1 concentration no mycelium was recorded and 100% inhibition was observed. The fungitoxicity of oil did not change even on
exposure to 100°C temperature or to autoclaving, and the oil also retained its fungicidal nature even after storage of 24 months.
The main changes observed under light microscopy after oil treatment were a decrease and loss of conidiation and anomalies
in the hyphae such as a decrease in the diameter of hyphae and granulation of cytoplasm. The treatment of the oil also showed
highly reduced cytoplasm in the hyphae, showing clear retraction of the cytoplasm from the hyphae and ultimately in some areas
hyphae without cytoplasm were also found. GC-MS studies of the essential oil revealed that the oil consisted of 24 compounds
with 1,8-cineole as major component accounting for 44.4% of the total constituents. 相似文献
15.
C. Sivapathasekaran Palashpriya Das Soumen Mukherjee J. Saravanakumar Mahitosh Mandal Ramkrishna Sen 《International journal of peptide research and therapeutics》2010,16(4):215-222
A marine Bacillus circulans DMS-2 was able to grow and produce biosurfactant on glucose mineral salts medium (GMSM) with a reduction in the surface tension
up to 27 mN m−1. The microorganism produced 1.64 ± 0.1 g l−1 of crude biosurfactant. The lipopeptide nature of the produced biosurfactant was confirmed by primulin and ninhydrin assays
using High Performance Thin Layer Chromatography (HPTLC). Preparative thin layer chromatography (TLC) was performed to purify
the lipopeptides from the crude biosurfactant. The critical micelle concentrations (CMC) of the crude and purified products
were found to be 90 and 40 mg l−1 respectively. Fourier transform infrared spectrophotometer (FTIR) and matrix assisted laser desorption/ionization time of
flight (MALDI-ToF) mass spectral analysis revealed the identity of the produced lipopeptides as surfactin (m/z 1,023 Da) and fengycin (m/z 1,495 Da) isoforms. The purified marine lipopeptides displayed a significant antiproliferative activity against the human
colon cancer cell lines HCT-15 (IC50 80 μg ml−1) and HT-29 (IC50 120 μg ml−1). 相似文献
16.
Syed G. Dastager C. K. Deepa Ashok Pandey 《World journal of microbiology & biotechnology》2011,27(2):259-265
A potential bacterial strain designated as NII-0928 isolated from Western ghat forest soil with multiple plant growth promoting attributes, and it has been identified and characterized. Plant growth promoting
traits were analyzed by determining the P-solubilization efficiency, Indole acetic acid production, HCN, siderophore production
and growth in nitrogen free medium. It was able to solubilize phosphate (76.6 μg ml−1), and produce indole acetic acid (58.9 μg ml−1) at 28 ± 2°C. Qualitative detection of siderophore production and HCN were also observed. At 5°C it was found to express
all the plant growth promotion attributes except HCN production. The ability to colonize roots is a sine qua non condition
for a rhizobacteria to be considered a true plant growth-promoting rhizobacteria (PGPR). 16S rRNA gene sequencing reveals
the identity of the isolate as Serratia nematodiphila with which it shares highest sequence similarity (99.4%). Seed bacterization with black pepper cuttings in greenhouse trials
using Sand: Soil: FYM with three individual experimental sets with their respective control showed clearly the growth promoting
activity. Hence, Serratia nematodiphila NII-0928 is a promising plant growth promoting isolate showing multiple PGPR attributes that can significantly influence
black pepper cuttings. The result of this study provides a strong basis for further development of this strain as a bioinoculants
to attain the desired plant growth promoting activity in black pepper growing fields. 相似文献
17.
Isolation and characterization of dihydromonacolin-MV from <Emphasis Type="Italic">Monascus purpureus</Emphasis> for antioxidant properties 总被引:4,自引:0,他引:4
Dhale MA Divakar S Kumar SU Vijayalakshmi G 《Applied microbiology and biotechnology》2007,73(5):1197-1202
The methanolic extract of Monascus purpureus cultivated by solid-state fermentation on rice showed strong 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity
and better yield as compared to other polarity based extracted fractions. It was selected for further purification of the
antioxidant. The activity-guided repeated fractionation of methanolic extract on a silica gel column chromatography yielded
a compound that exhibited strong antioxidant activity. Based on the spectroscopic analysis by UV, IR, 1H NMR, 13C NMR, 2D-HSQCT NMR, and MS, the antioxidant isolated was elucidated as a derivative of dihydromonacolin-K, where the ester
group is 2-methyl propionate, designated as dihydromonacolin-MV. The DPPH radical was significantly scavenged by the dihydromonacolin-MV
(IC50 20±1 μg ml−1). The dihydromonacolin-MV showed strong inhibition of lipid peroxidation in a liposome model with an IC50 value of 5.71±0.38 μg ml−1 and superoxide radical scavenging activity with an IC50 value of 163.97±2.68 μg ml−1. 相似文献
18.
Yuichi Uno Shigeyuki Nakao Yumiko Yamai Ryohei Koyama Michio Kanechi Noboru Inagaki 《Plant Cell, Tissue and Organ Culture》2009,98(3):303-309
An in vitro regeneration and transient expression systems were developed for the halophyte sea aster (Aster tripolium L.), an important genetic resource for salt tolerance. Adventitious shoots were formed from both leaf explants and suspension-cultured
cells in a Murashige and Skoog (MS) (Physiol Plant 15:473–497, 1962) basal salts containing 500 mg l−1 casamino acids, and supplemented with 5.4 μM a-naphthaleneacetic acid (NAA) and 4.7 μM kinetin to the culture medium. Hyperhydricity of shoots was avoided by increasing
the ventilation of the culture vessel. Root formation from shoots was promoted in the presence of 26.9 μM NAA. A high yield
of protoplasts was isolated using 1% cellulase and 0.25% pectinase from both leaf mesophyll and suspension-cultured cells,
and these were used for transient expression. The highest level of transient expression of the green fluorescent protein was
obtained with 1 × 105 protoplasts ml−1, 25 μg batch−1 of plasmid vector, and 30% polyethylene glycol 4,000. 相似文献
19.
Ciliate and bacterial densities and their link with eutrophication were studied in fourteen shallow lakes in northwest Spain.
Total phosphorus (TP) in these lakes varied between 30 μg l−1 and 925 μg l−1 and chlorophyll a concentration (chla) between 0.5 μg l−1 and 107 μg l−1. Bacterial abundance ranged from 1 × 106 to 14 × 106 cells ml−1, while ciliate abundance ranged from 0.6 cells ml−1 to 229 cells ml−1. Lakes were classified into three trophic types from their TP and chla concentrations. Bacterial abundance was significantly
correlated with trophic type, as well as with TP and with chla separately, whereas ciliate abundance was only correlated with
chla. No significant relationship could be established between bacterial and ciliate abundance across the trophic gradient.
A general pattern was observed in the ratios of bacterial abundance to TP and chla concentrations, of decreasing ratios with
increases in the nutrient loading. This pattern was not found for ciliates. The dominant zooplankton group in 13 of the 14
lakes studied was Rotifera, which accounted for a mean of 71% of total zooplankton abundance (41% of zooplankton biomass).
The positive correlation between bacteria and ciliates with this group, and the absence of any relationship with Cladocera
suggest that top down control by cladocerans was weaker in our lakes than previously shown in northern European shallow lakes.
Rotifers could be important predators of bacteria in the high-nutrient lakes of our study. Higher slopes of regressions on
bacterial abundance towards the hypertrophic range indicate that top-down control was weaker in our lakes than in northern
European shallow lakes. 相似文献
20.
Guggulsterone, a hypolipidemic natural agent, is produced in resin canals of the plant Commiphora wightii. In this study, the stimulatory effects of growth retardants [ALAR (N,N-dimethylaminosuccinamic acid) and CCC (chlormequat chloride)] and fungal elicitor on guggulsterone accumulation in cell cultures
of C. wightii are reported. CCC at 1 mg l−1 enhanced guggulsterone content (~123 μg l−1) when added on the fifth day after inoculation, while ALAR at 2.5 mg l−1 increased guggulsterone content (~116 μg l−1) when added on the tenth day. In a two-stage fed-batch process, combined treatment with fungal elicitor and growth retardant
caused a significant increase (~353 μg l−1) in guggulsterone content in cell cultures after 17 days of growth. This represents an approximately fivefold increase over
the guggulsterone contents in initial cultures of this plant. 相似文献