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1.
During enrichments to search for soil bacteria that form the volatile ketones, acetone and butanone, we isolated pure cultures
of Pseudomonas aureofaciens, P. fluorescens, and P. putida that excrete the β-keto-acid, 3-oxopentanoate (3-OPA), when grown on heptanoic acid as carbon source. Analysis of 3-OPA used
enzymatic decarboxylation by acetoacetate decarboxylase to yield butanone, which was detected by headspace gas chromatography.
The formation of 3-OPA was strongly dependent on heptanoic acid concentration, the level of oxygen, and the state of growth,
and was not seen with even-chain or other odd-chain fatty acids. Uptake of 3-OPA during stationary phase of growth is probably
related to polyhydroxyalkanoate (PHA) formation in these isolates. A model for formation and release of 3-OPA is proposed.
Received: 28 August 2000 / Accepted: 2 October 2000 相似文献
2.
The expression of some Saccharomyces cerevisiae genes is induced as cells enter stationary phase. Their mRNAs are translated during a period in the growth cycle when the
translational apparatus is relatively inert, thereby raising the possibility that these mRNAs compete effectively for a limiting
pool of translation factors. To test this idea, the translation of mRNAs carrying different 5′-leaders was compared during
exponential growth and after entry into stationary phase upon glucose starvation. Closely related sets of lacZ mRNAs, carrying 5′-leaders from the PYK1, PGK1, RpL3, Rp29, HSP12, HSP26 or THI4 mRNAs, were studied. These mRNAs displayed differing translational efficiencies during exponential growth, but their relative
translatabilities were not significantly affected by entry into stationary phase, indicating that they compete just as effectively
under these conditions. Polysome analysis revealed that the wild-type PYK1, ACT1 and HSP26 mRNAs are all translated efficiently during stationary phase, when the translational apparatus is relatively inert. Also,
significant levels of the translation initiation factors eIF-2α, eIF-4E and eIF-4A were maintained during the growth cycle.
These data are consistent with the idea that, while translational activity decreases dramatically during entry into stationary
phase, yeast cells maintain excess translational capacity under these conditions.
Received: 31 March 1998 / Accepted: 4 May 1998 相似文献
3.
The effect of some culture variables in the production of β-galactosidase from Escherichia coli in Bacillus subtilis was evaluated. The lacZ gene was expressed in B. subtilis using the regulatory region of the subtilisin gene aprE. The host contained also the hpr2 and degU32 mutations, which are known to overexpress the aprE gene. We found that, when this overproducing B. subtilis strain was grown in mineral medium supplemented with glucose (MMG), β-galactosidase production was partially growth-associated,
as 40%–60% of the maximum enzyme activity was produced before the onset of the stationary phase. In contrast, when a complex
medium was used, β-galactosidase was produced only at low levels during vegetative growth, whereas it accumulated to high
levels during early stationary phase. Compared with the results obtained in complex media, a 20% increase in specific β-galactosidase
activity in MMG supplemented with 11.6 g/l glucose was obtained. On the 1-l fermenter scale, a threefold increase in volumetric
β-galactosidase activity was obtained when the glucose concentration was varied from 11 g/l to 26 g/l. In addition, glucose
feeding during the stationary phase resulted in a twofold increase in volumetric enzyme activity as cellular lysis was prevented.
Finally, we showed that oxygen uptake and carbon dioxide evolution rates can be used for on-line determination of the onset
of stationary phase, glucose depletion and biomass concentration.
Received: 18 April 1996 / Received revision: 27 August 1996 / Accepted: 6 September 1996 相似文献
4.
Kacena MA Merrell GA Manfredi B Smith EE Klaus DM Todd P 《Applied microbiology and biotechnology》1999,51(2):229-234
Previous investigations have reported that bacterial suspension cultures grow to higher stationary concentrations in space
flight than on Earth; however, none of these investigations included extensive ground controls under varied inertial conditions.
This study includes extensive controls and cell-growth data taken at several times during lag phase, log phase, and stationary
phase of Escherichia coli and Bacillus subtilis. The Marquardt-Levenberg, least-squares fitting algorithm was used to calculate kinetic growth parameters from the logistic
bacterial growth equations for space-flight and control growth curves. Space-flight cultures grew to higher stationary-phase
concentrations and had shorter lag-phase durations. Also, evidence was found for increased exponential growth rate in space.
Received: 27 February 1998 / Received revision: 21 August 1998 / Accepted: 3 September 1998 相似文献
5.
Batch cultures of photoautotrophic cell suspensions of Chenopodiumrubrum L., growing in an inorganic medium on CO2 under a daily balanced light–dark regime of 16 : 8 h could be maintained for approximately 100 d without subcultivation.
The long-lived cultures showed an initial cell division phase of 4 weeks, followed by a stationary phase of another 4 weeks,
after which ageing and progressive cell death reduced the number of living cells and the cultures usually expired after another
3–4 weeks. These developmental phases of the cell culture were characterised with respect to photosynthetic performance, dark
respiration, content of phytohormones and capacity of cell division. Cell division of the majority of the cells finished in
the G1- or G0-phase of the cell cycle, caused by a pronounced decline in the endogenous levels of auxin and cytokinins. Supply
of these growth factors to resting cells resulted in resumption of cytokinesis, at least by some of the cells. However, responsiveness
to the phytohomones declined during the stationary phase, and subcultivation was no longer possible beyond day 60 when the
phases of ageing and death commenced. Ageing was characterised by a further decline in the photosynthetic capacity of the
cells, by a climacteric enhancement of dark respiration, but also by a slight increase in the level of IAA and cytokinins
concomitant with a decrease in ethylene. Similarities and differences between the development of batch-cultured photoautotrophic
cells of C. rubrum and that of a leaf are discussed with respect to using the cell culture as a model for a leaf.
Received: 30 April 1999 / Accepted: 21 August 1999 相似文献
6.
Tests of a linear model of visual-vestibular interaction using the technique of parameter estimation
Vallabh E. Das Alfred O. DiScenna Andrew Feltz Stacy Yaniglos R. John Leigh 《Biological cybernetics》1998,78(3):183-195
The goal of this study was to test whether a superposition model of smooth-pursuit and vestibulo-ocular reflex (VOR) eye
movements could account for the stability of gaze that subjects show as they view a stationary target, during head rotations
at frequencies that correspond to natural movements. Horizontal smooth-pursuit and the VOR were tested using sinusoidal stimuli
with frequencies in the range 1.0–3.5 Hz. During head rotation, subjects viewed a stationary target either directly or through
an optical device that required eye movements to be approximately twice the amplitude of head movements in order to maintain
foveal vision of the target. The gain of compensatory eye movements during viewing through the optical device was generally
greater than during direct viewing or during attempted fixation of the remembered target location in darkness. This suggests
that visual factors influence the response, even at high frequencies of head rotation. During viewing through the optical
device, the gain of compensatory eye movements declined as a function of the frequency of head rotation (P < 0.001) but, at any particular frequency, there was no correlation with peak head velocity (P > 0.23), peak head acceleration (P > 0.22) or retinal slip speed (P > 0.22). The optimal values of parameters of smooth-pursuit and VOR components of a simple superposition model were estimated
in the frequency domain, using the measured responses during head rotation, as each subject viewed the stationary target through
the optical device. We then compared the model's prediction of smooth-pursuit gain and phase, at each frequency, with values
obtained experimentally. Each subject's pursuit showed lower gain and greater phase lag than the model predicted. Smooth-pursuit
performance did not improve significantly if the moving target was a 10 deg × 10 deg Amsler grid, or if sinusoidal oscillation
of the target was superimposed on ramp motion. Further, subjects were still able to modulate the gain of compensatory eye
movements during pseudo-random head perturbations, making improved predictor performance during visual-vestibular interactions
unlikely. We conclude that the increase in gain of eye movements that compensate for head rotations when subjects view, rather
than imagine, a stationary target cannot be adequately explained by superposition of VOR and smooth-pursuit signals. Instead,
vision may affect VOR performance by determining the context of the behavior.
Received: 16 June 1997 / Accepted: 5 December 1997 相似文献
7.
Etienne Hollande Marjorie Fanjul Nawal Houti Jean-Charles Faye Philippe Courriere 《In vitro cellular & developmental biology. Animal》1998,34(7):593-599
Summary In steroid target tissues, the presence of the corresponding hormone receptors is indicative of hormone dependence. In an
attempt to assess the possible role of steroid hormones in the mechanism of growth and/or differentiation of cancerous pancreatic
duct cells, the expression of estrogen receptor (ERα) was evaluated in human cancerous pancreatic duct cells (Capan-1) maintained in culture. These cells were selected as they
acquire progressively a high degree of differentiation during growth in culture. In the present study, we showed that Capan-1
cells during growth in steroid-free medium associate spontaneously, become polarized, and form duct-like structures, features
that are indicative of a high degree of differentiation. Capan-1 cells were also found to express ERα and progesterone receptor (PR). Immunoenzymatic assay showed maximal expression of ERα (236 ± 55 fmol/mg protein) on the first day of the exponential growth phase, followed by a marked fall in expression (76.3%).
At the onset of the stationary phase (Day 5), ERα levels were below 10 fmol/mg protein, becoming undetectable by Day 7. A similar time course was observed for PR: 18 ± 0.9
fmol/mg protein at the onset of the exponential growth phase and no expression during the stationary phase. Addition of estradiol
to 1-d-old cultures resulted in a twofold increase in PR expression, suggesting an induction of PR expression by estrogen.
Immunocytochemical analysis with anti-ERα-1D5 antibodies showed nuclear and cytoplasmic localization of ERα in Capan-1 cells in the first 24 h of culture followed by a progressive disappearance thereafter. We also showed that cellular
multiplication was increased by estradiol and progesterone during the exponential growth phase, pointing to the involvement
of steroid hormones in the proliferation of nonpolarized Capan-1 cells. These results indicate that the expression of ERα is linked to the state of differentiation of the cells and make Capan-1 cells a model of choice to study ER regulation in
nontarget tissues. 相似文献
8.
According to the principal control point (PCP) hypothesis, experiments with excised, carbohydrate-starved stationary root
meristems of Vicia faba var. minor have demonstrated that cells which previously divided asynchronously were preferentially blocked in G1 (PCP1) and G2 (PCP2) phases. When stationary phase meristems are supplied with exogenous carbohydrate (2 % sucrose), the G1- and G2-arrested
cells start out DNA replication and mitotic divisions, respectively. The resumption of DNA synthesis and mitosis is not immediate
and the delays of G1- and G2-arrested cells are found different. Using this model, we examined the effects of 4 pulse incubations with okadaic acid (OA),
a specific inhibitor of PP1 and PP2A, on the duration of intervals elapsing between the provision of sucrose and the first
appearance of S- and M-phase cells. We have found that depending on the period during which OA had been applied, the release
from G1 and G2 phase arrest-points becomes prolonged, showing different time-course modifications. The obtained data provide
evidence that activation of PP1 and PP2A is required to allow the cells for both PCP1→S and PCP2→M transitions in root meristems
of V. faba. 相似文献
9.
D. R. Barras 《Antonie van Leeuwenhoek》1972,38(1):65-80
A Β-glucan hydrolase showing a marked specificity for Β-1,3-glucosidic linkages was found to be closely associated with the
cell wall of the fission yeastSchizosaccharomyces pombe. Intact log-phase cells showed 40% of the enzyme activity measured in the cell homogenate. Cellular enzyme activity reached
a maximum during the logarithmic growth phase and decreased sharply in the stationary phase. The possible role of the enzyme
in cell wall extension is discussed.
Issued as NRCC No. 12329
National Research Council of Canada Postdoctorate Fellow, 1968–69.
The author gratefully acknowledges helpful discussions with Dr. B. F. Johnson. 相似文献
10.
Abstract
In many intertidal cohesive—sediment habitats, epipelic diatoms are the dominant microphytobenthic organisms. In such sediments,
concentrations of colloidal carbohydrate [including the exopolymeric substances (EPS) produced by diatoms during motility]
are closely correlated with the biomass (chlorophyll a) of epipelic diatoms. A model describing this relationship (log (conc. coll. carbo. + 1) = 1.40 + 1.02(log (chl. a conc. + 1)) was derived from published data. It was validated against published and unpublished data from 6 different estuaries,
and accounted for 64.6% of the variation in sediment colloidal carbohydrate concentrations. The model was valid for intertidal
habitats with cohesive sediments where epipelic diatoms constituted >50% of the microphytobenthic assemblage. In sites with
noncohesive sediments, or where the microphytobenthic assemblage was dominated by other algal groups, the model was not applicable.
The mean percentage of EPS in colloidal carbohydrate extracts varied between 11 and 37% for axenic cultures of epipelic diatoms
(with higher values obtained during stationary phase), and between 22.7% and 24.3% for natural sediments dominated by epipelic
diatoms. Assuming an EPS percentage of 25% in colloidal extracts yielded an EPS chl. a ratio of 2.62:1. Maximum rates of EPS production in diatom cultures occurred at the beginning of stationary phase (1.6–5.09
μg EPS μg−1 chl a d−1), with Nitzschia sigma having a significantly (P < 0.05) higher rate of production than N. frustulum, Navicula perminuta and Surirella ovata. Similar rates of EPS production were measured in the field. The dynamics of EPS production and loss on mudflats is discussed,
with reference to the model and these production rates.
Received: 25 February 1997; Accepted: 23 May 1997 相似文献
11.
H D Paik S S Bae S H Park J G Pan 《Journal of industrial microbiology & biotechnology》1997,19(4):294-298
Bacillus thuringiensis subsp tochigiensis HD868 was identified as a bacteriocin producer which exhibited a bactericidal effect against closely related species. This
bacteriocin designated as tochicin, was partially purified by 75% ammonium sulfate precipitation followed by subsequent
dialysis. This partially purified tochicin showed a narrow antibacterial spectrum of activity against most of 20 typical
B. thuringiensis strains and a strain of B. cereus, but not against other bacteria and yeasts tested. The antibacterial activity of tochicin on sensitive indicator cells disappeared
completely by proteinase K treatment (1 mg ml−1), which indicates its proteinaceous nature. Tochicin was very stable throughout the range of pH 3.0–9.0 and was relatively
heat-stable at 90°C, but bacteriocin activity was not detected after boiling for 30 min. The relationship between cell growth
and bacteriocin production was studied in a semi-defined medium. Tochicin activity was detected at the mid-log growth phase,
reached the maximum at the early stationary phase, but decreased after the stationary phase. Direct detection of tochicin
activity on sodium dodecyl sulfate-polyacrylamide gel suggested it has an apparent molecular mass of about 10.5 kDa. Tochicin
exhibited a bactericidal activity against B. thuringiensis subsp thompsoni HD522 in phosphate buffer (pH 7.0).
Received 02 December 1996/ Accepted in revised form 25 August 1997 相似文献
12.
13.
M A Jackson J S Frymier B J Wilkinson P Zorner S Evans 《Journal of industrial microbiology & biotechnology》1998,21(4-5):237-241
Xanthomonas campestris MB245, a specific pathogen of the weedy grass Poa annua (annual bluegrass), is being developed as a bioherbicide to control this pest in turf. Nutritional and environmental factors
were evaluated based on their ability to support rapid submerged culture growth and high cell yield. Temperature optima for
the growth of X. campestris cells in submerged culture were between 27 and 30°C. At 30°C, optimal nutritional conditions for X. campestris growth supported generation times of 150–175 min and cell yields after 24 h growth of 1–2 × 1010 cells ml−1. Media containing sucrose or glucose as the carbon source and various organic nitrogen sources supported optimal X. campestris growth and cell yield. The addition of vitamin mixtures to complex and defined media had no significant effect on growth
or cell yield. The age of X. campestris cultures had a significant impact on cell survival after freeze drying. Following freeze drying, log phase cell survival
(44%) was significantly lower than early and late stationary phase cell survival, 62% and 68%, respectively. Cells harvested
in stationary phase, freeze dried and stored under vacuum at 4°C, showed no significant loss in viability after 6 months.
Thus, high cell concentrations of the bioherbicide X. campestris can be rapidly produced in submerged culture and stabilized as freeze-dried preparations.
Received 14 August 1998/ Accepted in revised form 8 October 1998 相似文献
14.
Cells ofBacillus megaterium contain 35–45% of poly(3-hydroxybutyrate) (PHB) at the beginning of the stationary phase. This amount is only slightly affected
by the medium composition. The PHB granules are spherical with the mean diameter of 1.15 μm. 相似文献
15.
An antibiotic produced by the scab disease-suppressive Streptomyces diastatochromogenes strain PonSSII has been isolated and partially characterized. The antibiotic is produced throughout culture growth, with
maximum amounts accumulating in the broth when the culture is in the early stationary phase of growth. The activity declines
within about 30 h after the culture enters stationary phase. Purification techniques included chromatography on Amberlite
XAD-2, DEAE Sephadex and SP Sephadex in addition to C18 HPLC with an average yield of 75%. This antibiotic only inhibits
pathogenic strains of S. scabies that cause scab disease on potato and other tuberous vegetables and does not affect S. griseus, S. venezuelae, Actinomyces bovis, Nocardia asteroides, Clostridium perfringens, Bacillus subtilis, Staphylococcus
aureus, S. epidermidis, Enterococcus faecalis, Micrococcus luteus, Serratia marcescens and Escherichia coli. The antibiotic has a molecular weight of 500 or less, and is stable for weeks at acidic pH but is very labile at alkaline
pH conditions.
Received 18 February 1997/ Accepted in revised form 11 August 1997 相似文献
16.
The DR2356 nudix hydrolase gene from Deinococcus radiodurans has been cloned and the product expressed as an 18 kDa histidine-tagged protein. The enzyme hydrolysed adenosine and diadenosine polyphosphates, always generating ATP as one of the initial products. ATP and other (deoxy)nucleoside triphosphates were also substrates, yielding (d)NDP and Pi as products. The DR2356 protein was most active at pH 8.6–9.0 and showed a strong preference for Mn2+ as activating cation. Mg2+ ions at 15 mM supported only 5% of the activity achieved with 2 mM Mn2+. K
m and k
cat values for diadenosine tetra-, penta- and hexaphosphates were 2.0, 2.4 and 1.1 μM and 11.4, 28.6 and 12.0 s−1, respectively, while for GTP they were 20.3 μM and 1.8 s−1, respectively. The K
m for adenosine 5′-pentaphosphate was <1 μM. Expression analysis showed the DR2356 gene to be induced eight- to ninefold in stationary phase and in cells subjected to slow dehydration plus rehydration. Superoxide (but not peroxide) treatment and rapid dehydration caused a two-to threefold induction. The Mn-requirement and induction in stationary phase suggest that DR2356 may have a specific role in maintenance mode metabolism in stationary phase as Mn2+ accumulates. 相似文献
17.
A flat plate, multi-pass air lift reactor (FPALR) for the culture of photosynthetic organisms was constructed from twin wall
acrylic sheet and its performance characterised. When operated at an air input of 2.01 min−1 the multi-pass system had a Reynolds number of 5200 indicating fully turbulent flow. Chlorella vulgaris 211/11c was found to have a stationary phase biomass of 1.48 g 1−1 when grown in the flat plate air lift reactor (FPALR) at 100 μmol m−2s−1 compared to 1.11 g 1−1 when cultured in the continually stirred tank reactor (CSTR) at the same PFD (photon flux density). The same organism cultured
at 200 μmol m−2s−1 achieved a stationary phase biomass of 1.71 g 1−1 in the FPALR. In contrast, Scenedesmus sp. produced a stationary phase biomass of 2.27 g1−1 and 1.27 g1−1, when cultured at 100 μmol m−2s−1 in the FPALR and the CSTR respectively. The growth rates of both organisms were also higher in the PFALR. 相似文献
18.
The RpoS sigma factor in proteobacteria regulates genes in stationary phase and in response to stress. Although of conserved
function, the RpoS regulon may have different gene composition across species due to high genomic diversity and to known environmental
conditions that select for RpoS mutants. In this study, the distribution of RpoS homologs in prokaryotes and the differential
dependence of regulon members on RpoS for expression in two γ-proteobacteria (Escherichia coli and Pseudomonas aeruginosa) were examined. Using a maximum-likelihood phylogeny and reciprocal best hits analysis, we show that the RpoS sigma factor
is conserved within γ-, β-, and δ-proteobacteria. Annotated RpoS of Borrelia and the enteric RpoS are postulated to have separate evolutionary origins. To determine the conservation of RpoS-dependent
gene expression across species, reciprocal best hits analysis was used to identify orthologs of the E. coli RpoS regulon in the RpoS regulon of P. aeruginosa. Of the 186 RpoS-dependent genes of E. coli, 50 proteins have an ortholog within the P. aeruginosa genome. Twelve genes of the 50 orthologs are RpoS-dependent in both species, and at least four genes are regulated by RpoS
in other γ-proteobacteria. Despite RpoS conservation in γ-, β-, and δ-proteobacteria, RpoS regulon composition is subject
to modification between species. Environmental selection for RpoS mutants likely contributes to the evolutionary divergence
and specialization of the RpoS regulon within different bacterial genomes. 相似文献
19.
O. A. Zhigalskii 《Biology Bulletin》2011,38(6):629-641
The results of long-term studies of two bank vole (Myodes glareolus) populations in stationary sites in the central part and periphery of its species area are described. Four phases of a multiannual
population cycle and two of its structural parts have been detected for both populations. The first part of the cycle is “determined,”
with the “peak” phase passing into a “depression” (population collapse). This transition is mainly determined by intrapopulation
processes and is weakly dependent on the external conditions of each individual year. The second part is “stochastic,” starting
from a stable point in the cycle in the depression phase. The duration of the second part is determined by the state of the
population and its ability to increase its size, as well as by the weather and food factors, predation pressure, and location
of the population within the species area. The transition from the peak phase to the depression phase (the determined part)
for both populations takes place during one fall-winter-spring season and has no effect on the cycle duration. The duration
of the stochastic part in the core of the species area (the period from depression phase to peak phase) is 1–3 years and in
the periphery, 2–4 years. 相似文献