共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Gabig M. Obuchowski S. Srutkowska G. Wegrzyn 《Molecular & general genetics : MGG》1998,258(5):494-502
It was previously demonstrated that while lysogenic development of bacteriophage λ in Escherichia coli proceeds normally at low temperature (20–25° C), lytic development is blocked under these conditions owing to the increased
stability of the phage CII protein. This effect was proposed to be responsible for the increased stimulation of the p
E promoter, which interferes with expression of the replication genes, leading to inhibition of phage DNA synthesis. Here we
demonstrate that the burst size of phage λcIb2, which is incapable of lysogenic development, increases gradually over the temperature range from 20 to 37° C, while no phage
progeny are observed at 20° C. Contrary to previous reports, it is possible to demonstrate that p
E promoter activation by CII may be more efficient at lower temperature. Using density-shift experiments, we found that phage
DNA replication is completely blocked at 20° C. Phage growth was also inhibited in cells overexpressing cII, which confirms that CII is responsible for inhibition of phage DNA replication. Unexpectedly, we found that replication
of plasmids derived from bacteriophage λ is neither inhibited at 20° C nor in cells overexpressing cII. We propose a model to explanation the differences in replication observed between λ phage and λ plasmid DNA at low temperature.
Received: 30 December 1997 / Accepted: 25 February 1998 相似文献
2.
3.
A C S Rizzatti J A Jorge H F Terenzi C G V Rechia M L T M Polizeli 《Journal of industrial microbiology & biotechnology》2001,26(3):156-160
A β-D-xylosidase was purified from cultures of a thermotolerant strain of Aspergillus phoenicis grown on xylan at 45°C. The enzyme was purified to homogeneity by chromatography on DEAE-cellulose and Sephadex G-100. The
purified enzyme was a monomer of molecular mass 132 kDa by gel filtration and SDS-PAGE. Treatment with endoglycosidase H resulted
in a protein with a molecular mass of 104 kDa. The enzyme was a glycoprotein with 43.5% carbohydrate content and exhibited
a pI of 3.7. Optima of temperature and pH were 75°C and 4.0–4.5, respectively. The activity was stable at 60°C and had a K
m of 2.36 mM for p-nitrophenyl-β-D-xylopiranoside. The enzyme did not exhibit xylanase, cellulase, galactosidase or arabinosidase activities. The purified enzyme
was active against natural substrates, such as xylobiose and xylotriose. Journal of Industrial Microbiology & Biotechnology (2001) 26, 156–160.
Received 23 June 2000/ Accepted in revised form 29 September 2000 相似文献
4.
The expression of the Arabidopsis heat shock protein (HSP) 18.2 promoter-β-d-glucuronidase (GUS) chimera gene was investigated in transgenic Nicotiana plumbaginifolia plants during the recovery phase at normal temperatures (20–22 °C) after a heat shock (HS) treatment. GUS activity increased
during the recovery phase after HS at 42 °C for 2 h, and maximal GUS activity was observed after 12 h at normal temperatures,
at levels 50–100 times higher than the activity immediately after HS. After HS at 44 °C, little GUS activity was observed
during the first 20–24 h at normal temperatures, but the activity increased gradually thereafter, to reach a maximum at 40–50 h.
After HS at 45 °C, no GUS activity was observed throughout the experimental period. RT-PCR analysis showed that GUS mRNA
remained for 10 h after a 2-h HS at 42 °C and for 40 h after a 2-h HS at 44 °C. These findings demonstrate that brief HS
treatment, especially at a sublethal temperature, induces a long-term accumulation of HSP-GUS mRNA during the recovery phase.
Received: 31 July 1998 / Revision received: 4 November 1998 / Accepted: 19 February 1999 相似文献
5.
Hayashi S Ohno T Ito M Yokoi H 《Journal of industrial microbiology & biotechnology》2001,26(5):276-279
β-Xylosidase was extracted from Aureobasidium sp. ATCC 20524 and purified to homogeneity. The molecular mass was estimated at 411 kDa. The enzyme contained 15.3% (w/w)
carbohydrate. The optimum pH and temperature were pH 3.5 and 80°C, respectively. The enzyme was stable at pH 3.5–9 after 3
h and at 80°C after 15 min. The Michaelis constant (K
m) and maximum velocity (V
max) toward p-nitrophenyl-β-D-xyloside were 2.0 mmol l−1 and 0.94 mmol min−1 mg−1 protein, respectively. The enzyme was inhibited strongly by mercury, lead, and copper ions. Journal of Industrial Microbiology & Biotechnology (2001) 26, 276–279.
Received 02 August 2000/ Accepted in revised form 15 December 2000 相似文献
6.
A Kademi L Fakhreddine N Aït-Abdelkader J C Baratti 《Journal of industrial microbiology & biotechnology》1999,23(3):188-193
Growth and esterase production (activity on p-nitrophenyl caprylate) by the newly isolated Bacillus circulans MAS2 bacterial strain were studied. The growth rate at 50°C was high (0.9 h-1) on LB medium with glucose added. Esterase production followed growth with the majority of activity being intracellular during
exponential growth phase. During stationary phase, the esterase activity was released in the culture medium. The strain was
able to grow at 35– 55°C with maximum growth rate at 50°C, showing a pattern typical of a moderate thermophile. Growth occurred
at pH 6–9 with a maximum at 8, with a similar pattern for the esterase production. Addition of glucose, fructose, sucrose
or sodium acetate greatly promoted both growth and esterase production while starch, inulin, tributyrin or glycerol showed
no effect. Complex nitrogen sources such as tryptone or yeast extract increased growth and esterase production while mineral
sources (ammonium chloride or sulfate), glycine or glutamate showed no effect. An increase of tryptone plus yeast extract
and glucose concentrations stimulated growth and esterase production which reached 160 U L−1.
Received 17 March 1999/ Accepted in revised form 25 June 1999 相似文献
7.
R Rech C F Cassini A Secchi M A Z Ayub 《Journal of industrial microbiology & biotechnology》1999,23(2):91-96
We studied the utilization of protein-hydrolyzed sweet cheese whey as a medium for the production of β-galactosidase by the
yeasts Kluyveromyces marxianus CBS 712 and CBS 6556. The conditions for growth were determined in shake cultures. The best growth occurred at pH 5.5 and
37°C. Strain CBS 6556 grew in cheese whey in natura, while strain CBS 712 needed cheese whey supplemented with yeast extract. Each yeast was grown in a bioreactor under these
conditions. The strains produced equivalent amounts of β-galactosidase. To optimize the process, strain CBS 6556 was grown
in concentrated cheese whey, resulting in a higher β-galactosidase production. The β-galactosidase produced by strain CBS
6556 produced maximum activity at 37°C, and had low stability at room temperature (30°C) as well as at a storage temperature
of 4°C. At −4°C and −18°C, the enzyme maintained its activity for over 9 weeks.
Received 20 January 1999/ Accepted in revised form 30 April 1999 相似文献
8.
Dr. Erich Kessler 《Plant Systematics and Evolution》1985,151(1-2):67-71
The upper limit of temperature for growth is a species-specific character in the genusChlorella. The limits of 14Chlorella species range from 26–30°C (C. saccharophila) to 38–42°C (C. sorokiniana), withC. fusca var.vacuolata (34°C) andC. kessleri (34–36°C) assuming an intermediate position. Thus, there is no wide gap in the temperature limits between the normal (“low-temperature”)
species ofChlorella and the “high-temperature” species,C. sorokiniana. 相似文献
9.
A detailed temperature dependence study of a well-defined plant ion channel, the Ca2+-activated K+ channel of Chara corallina, was performed over the temperature range of their habitats, 5–36°C, at 1°C resolution. The temperature dependence of the
channel unitary conductance at 50 mV shows discontinuities at 15 and 30°C. These temperatures limit the range within which
ion diffusion is characterized by the lowest activation energy (E
a
= 8.0 ± 1.6 kJ/mol) as compared to the regions below 15°C and above 30°C. Upon reversing membrane voltage polarity from 50
to −50 mV the pattern of temperature dependence switched from discontinuous to linear with E
a
= 13.6 ± 0.5 kJ/mol. The temperature dependence of the effective number of open channels at 50 mV showed a decrease with increasing
temperature, with a local minimum at 28°C. The mean open time exhibited a similar behavior. Changing the sign of membrane
potential from 50 to −50 mV abolished the minima in both temperature dependencies. These data are discussed in the light of
higher order phase transitions of the Characean membrane lipids and corresponding change in the lipid-protein interaction,
and their modulation by transmembrane voltage.
Received: 14 June 2000/Revised: 20 September 2000 相似文献
10.
Bifidobacteria play an important role in human health including the enhancement of resistance against infection in infants.
To develop an inexpensive whey-based medium for Bifidobaterium bifidum, potential growth promoters — yeast extract, casein, bovine casein digest, tryptone, peptone and glucosamine — singly or
in combinations, were evaluated for their bifidus growth-promoting activity. The effect of environmental conditions on growth
in cheese whey was also evaluated. A whey-based medium for B. bifidum was formulated. Cheese whey supplemented with N-acetylglucosamine (1 mg/ml) and yeast extract (10 mg/ml) in the presence of sodium thioglycolate (0.1%) at pH 6.8 promoted
the growth of B. bifidum at 37°C. Journal of Industrial Microbiology & Biotechnology (2000) 25, 177–179.
Received 20 May 2000/ Accepted in revised form 20 July 2000 相似文献
11.
J. T. Kemp M. K. Balasubramanian K. L. Gould 《Molecular & general genetics : MGG》1997,254(2):127-138
The organization of the actin cytoskeleton plays an integral role in cell morphogenesis of all eukaryotes. We have isolated
a temperature-sensitive mutant in Schizosaccharomyces pombe, wat1-1, in which acting patches are delocalized, resulting in an elliptically shaped cell phenotype. Molecular cloning and DNA sequencing
of wat1
+ showed that the gene encodes a 314 residue protein containing WD-40 repeats. Cells lacking wat1
+ are slow growing but viable at 25° C and temperature-sensitive for growth above 33° C. At restrictive temperature, wat1-d strains are phenotypically indistinguishable from wat1-1. When combined with a deletion for the wat1
+ gene, cdc mutants failed to elongate at restrictive temperature and exhibited alterations in actin patch localization. This
analysis suggests that wat1
+ is required directly or indirectly for polarized cell growth in S. pombe. Wat1p and a functional, epitope-tagged, version of Wat1p can be overproduced without inducing alterations in cell morphology.
Received: 18 September 1996 / Accepted: 22 October 1996 相似文献
12.
13.
A marine fungus was isolated from the black tiger prawn Penaeus monodon at Nha Trang, Vietnam, on March 20, 2001 and named isolate NJM 0131. The fungus was identified as Haliphthoros milfordensis from the characteristics of asexual reproduction, and its physiological characteristics were investigated. Although the optimum
temperature for growth of the isolate was 25°–30°C, the fungus grew at a wide range of temperatures (15°–40°C). H. milfordensis grew well in 50%–100% seawater, but poorly in PYG agar containing 1.0%–5.0% NaCl and KCl. The fungus grew at a wide range
of pH (4.0–11.0) with the optimum pH value of 7.0–9.0. The isolate also showed pathogenicity to swimming crab larvae (Portunus trituberculatus) by artificial infection, but mortality was not high. This is the first report of disease in the black tiger prawn P. monodon in Vietnam caused by H. milfordensis.
Received: July 22, 2002 / Accepted: January 21, 2003
Correspondence to:K. Hatai 相似文献
14.
C. Traeholt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):177-184
Five water monitor lizards, Varanus salvator salvator, and four clouded monitor lizards, Varanus bengalensis nebulosus, were caught on Tioman island in Malaysia. A radio-thermistor transmitter was implanted into the buccal cavity of each animal,
and they were released into an enclosure measuring 5.5 × 6.5 metres. The lizards were observed for 9 and 8 days, respectively,
before and after the parietal eye was covered with aluminium foil. With uncovered parietal eye, both species showed a clear
diurnal rhythm, being active only during day time. After covering the parietal eye, the mean locomotor activity of five V. s. salvator decreased from 791 to 107 min · day–1 but remained unchanged around 850 min · day–1 for V. b. nebulosus. The mean duration of locomotor activity decreased in V. s. salvator and V. b. nebulosus after the parietal eye was covered, but V. b. nebulosus maintained its locomotor activity by increasing the number of locomotor bouts. The water monitor spent very little time on
thermoregulation. Its body temperature ranged between 26.3 and 28.4 °C, which decreased after the parietal eye was covered.
The clouded monitor thermoregulated around 28.8–36.0 °C, which remained unchanged after the parietal eye was covered. In both
species, there was a strong correlation between body temperature and ambient temperature. Behavioural abnormalities were recorded
among V. s. salvator with covered parietal eye. They were often observed to be active by night and often slept outside a burrow. The circadian
rhythm of V. b. nebulosus appeared unaffected by shielding of its parietal eye. Captivity combined with shielded parietal eye induced agonistic behaviour
in both species.
Accepted: 11 September 1996 相似文献
15.
InBacillus megaterium, a temperature that suppresses sporulation (43°C) only slightly exceeds both the optimum growth temperature and the temperature
still permitting sporulation (40–41°C). Here we show that, when cells grown at 35°C and transferred to a sporulation medium,
were subjected to shifts between 35°C and the sporulation suppressing temperature (SST, 43°C), their development and proteolytic
activities were deeply affected. During the reversible sporulation phase that took place at 35°C for 2–3 h (T2–T3), the cells developed forespores and their protein turnover was characterized by degradation of short-lived proteins and
proteins made accessible to the proteolytic attack because of starvation. During the following irreversible sporulation phase
refractile heat-resistant spores appeared at T4–T5. Protein turnover rate increased again after T2 and up to T8 60–70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T3 no asymmetric septa were observed and the amount of heat-resistant spores at T8 was by 4–5 orders lower than at 35°C. However, the cells remained viable and were able to sporulate when transferred to a
lower temperature. Protein degradation was increased up to T3 but then its velocity sharply dropped and the amount of degraded protein at T8 corresponded to slightly more than one-half of that found at 35°C. The cytoplasmic proteolytic activity was enhanced but
the activity in the membrane fraction was decreased. When a temperature shift to SST was applied at the beginning of the irreversible
sporulation phase (T2.5), the sporulation process was impaired. A portion of forespores lyzed, the others were able to complete their development
but most spores were not heat-resistant and their coats showed defects. Protein degradation increased again because an effective
proteolytic system was developed during the reversible sporulation phase but the amount of degraded protein was slightly lower
than at 35°C. A later (T4) shift to SST had no effect on the sporulation process. 相似文献
16.
Rosa Margesin 《Extremophiles : life under extreme conditions》2009,13(2):257-262
Three bacterial (Pedobacter heparinus, Pedobacter piscium, Pedobacter cryoconitis) and three yeast strains (Saccharomyces cerevisiae, Leucosporidiella creatinivora, Rhodotorula glacialis) of different thermal classes (mesophiles and psychrophiles) were tested for the effect of temperature on a range of growth
parameters, including optical density, viable cell numbers, and cell dry mass, in order to determine the temperature conditions
under which maximum biomass formation is obtained. Maximum values of growth parameters obtained at the stationary growth phase
of the strains were used for statistical calculation. Temperature had a significant (P ≤ 0.05) effect on all growth parameters for each strain; correlations between the growth parameters were significant (P ≤ 0.05–0.01). The maximum growth temperature or the temperature at which microbial growth was fastest was in no case the temperature
at which the investigated strains produced the highest amount of biomass. All tested psychrophilic bacteria and yeast strains
produced highest amounts of cells (as calculated per mg cell dry mass or per OD600 unit) at 1°C, while cell numbers of mesophiles were highest at 20°C. Thus, cultivation temperatures close to the maximum
growth temperature are not appropriate for studying psychrophiles. 相似文献
17.
Two extremely thermophilic archaebacteria, strains OG-1 and SM-2, were isolated from newly discovered deep-sea hydrothermal
vent areas in the western Pacific ocean. These strains were cocci, obligately anaerobic Archaea about 0.7–2 μm in diameter.
Optimum growth conditions for OG-1 and SM-2 were at 85–90°C (range 60–100°C), pH 6 (range pH 4–8), a NaCl concentration of
3% (range 1–5%), and a nutrient concentration (tryptone plus yeast extract) of 0.2% (range 0.005–5%). Elemental sulfur stimulated
the growth rate fourfold. Ammonium slightly stimulated growth. Both tryptone and yeast extract allowed growth as sole carbon
sources; these isolates were not able to utilize or grow exclusively on sucrose, glucose, maltose, succinate, pyruvate, propionate,
acetate, or free amino acids. OG-1 showed the fastest growth rate within the genus Thermococcus. Growth was inhibited by rifampicin. The DNA G+C content was 52 mol%. Sequencing of their 16S rDNA gene fragment indicated
that these isolates belonged to the genus Thermococcus. OG-1 and SM-2 were different than the described Thermococcus species. We propose that OG-1 belongs to a new species: Thermococcus peptonophilus.
Received: 8 March 1995 / Accepted: 24 May 1995 相似文献
18.
Thermolabile xylanase of the Antarctic yeast Cryptococcus adeliae: production and properties 总被引:4,自引:0,他引:4
Xylanase production by the Antarctic psychrophilic yeast Cryptococcus adeliae was increased 4.3 fold by optimizing the culture medium composition using statistical designs. The optimized medium containing
24.2 g l−1 xylan and 10.2 g l−1 yeast extract and having an initial pH of 7.5 yielded xylanase activity at 400 nkat (nanokatal) ml−1 after 168-h shake culture at 4°C. In addition, very little endoglucanase, β-mannanase, β-xylosidase, β-glucosidase, α-l-arabinofuranosidase, and no filter paper cellulase activities were detected. Among 12 carbon sources tested, maximum xylanase
activity was induced by xylan, followed by lignocelluloses such as steamed wheat straw and alkali-treated bagasse. The level
of enzyme activity produced on other carbon sources appeared to be constitutive. Among the complex organic nitrogen sources
tested, the xylanase activity was most enhanced by yeast extract, followed by soymeal, Pharmamedia (cotton seed protein),
and Alburex (potato protein). A batch culture at 10°C in a 5-l fermenter (3.5-1 working volume) using the optimized medium
gave 385 nkat at 111 h of cultivation. The crude xylanase showed optimal activity at pH 5.0–5.5 and good stability at pH 4–9
(21 h at 4°C). Although the enzyme was maximally active at 45°–50°C, it appeared very thermolabile, showing a half-life of
78 min at 35°C. At 40°–50°C, it lost 71%–95% activity within 5 min. This is the first report on the production as well as
on the properties of thermolabile xylanase produced by an Antarctic yeast.
Received: December 10, 1999 / Accepted: March 23, 2000 相似文献
19.
The gram-negative bacterium Myxobacter sp. AL-1 produces chitosanase-cellulase activity that is maximally excreted during the stationary phase of growth. Carboxymethylcellulase
zymogram analysis revealed that the enzymatic activity was correlated with two bands of 32 and 35 kDa. Ion-exchange-chromatography-enriched
preparations of the 32-kDa enzyme were capable of degrading the cellulose fluorescent derivatives 4-methylumbelliferyl-β-d-cellobioside and 4-methylumbelliferyl-β-d-cellotrioside. These enzymatic preparations also showed a greater capacity at 70° C than at 42° C to degrade chitosan oligomers
of a minimum size of six units. Conversely, the β-1,4 glucanolytic activity was more efficient at attacking carboxymethylcellulose
and methylumbelliferyl-cellotrioside at 42° C than at 70° C. The 32-kDa enzyme was purified more than 800-fold to apparent
homogeneity by a combination of ion-exchange and molecular-exclusion chromatography. Amino-terminal sequencing indicated that
mature chitosanase-cellulase shares more than 70% identity with endocellulases produced by strains DLG, PAP115, and 168 of
the gram-positive microorganism Bacillus subtilis.
Received: 6 January 1997 / Accepted: 29 May 1997 相似文献
20.
Summary. Spore coat-associated alanine racemase of Bacillus subtilis, which converts L-alanine to D-alanine, that is, the germinant to the competitive inhibitor, to regulate spore germination
for survival of the organism under unfavorable growth conditions, was examined. The dormant spores, L-alanine-initiated germination
of which is inhibited by diphenylamine, were used to characterize the enzyme in the native form because of its unextractablility
from dormant spores. The presence of isozymes, Enz-I and Enz-II with Km for L-alanine of about 20 mM and 50 mM and optimum
activity at around 40°C and 65°C, respectively, was proposed. The enzymes were selectively used depending on the L-alanine
concentration and the temperature. The pH profiles of the activity (optimun at pH 9.0) and the stability (stable between pH
6–11 at 60°C) were similar, but Enz-II was more heat-stable than Enz-I and the denaturation curve demonstrated a two-domain
structure for Enz-II. Sensitivity to D-penicillamine, hydroxylamine and HgCl2 was similar between Enz-I and Enz-II, while that to D-cycloserine, L- and D-aminoethylphosphonic acid, monoiodoacetate and
N-ethylmaleimide was different; HgCl2 was the most effective inhibitor among these compounds.
Received December 13, 1999, Accepted January 11, 2000 相似文献