共查询到20条相似文献,搜索用时 62 毫秒
1.
Bacillus anthracis makes highly stable, heat-resistant spores which remain viable for decades. Effect of various stress conditions on sporulation
in B. anthracis was studied in nutrient-deprived and sporulation medium adjusted to various pH and temperatures. The results revealed that
sporulation efficiency was dependent on conditions prevailing during sporulation. Sporulation occurred earlier in culture
sporulating at alkaline pH or in PBS than control. Spores formed in PBS were highly sensitive towards spore denaturants whereas,
those formed at 45°C were highly resistant. The decimal reduction time (D-10 time) of the spores formed at 45°C by wet heat,
2 M HCl, 2 M NaOH and 2 M H 2O 2 was higher than the respective D-10 time for the spores formed in PBS. The dipicolinic acid (DPA) content and germination
efficiency was highest in spores formed at 45°C. Since DPA is related to spore sensitivity towards heat and chemicals, the
increased DPA content of spores prepared at 45°C may be responsible for increased resistance to wet heat and other denaturants.
The size of spores formed at 45°C was smallest amongst all. The study reveals that temperature, pH and nutrient availability
during sporulation affect properties of B. anthracis spores. 相似文献
2.
Thermophilic endospores are widespread in cold marine sediments where the temperature is too low to support growth and activity of thermophiles in situ. These endospores are likely expelled from warm subsurface environments and subsequently dispersed by ocean currents. The endospore upper temperature limit for survival is 140°C, which can be tolerated in repeated short exposures, potentially enabling transit through hot crustal fluids. Longer-term thermal tolerance of endospores, and how long they could persist in an environment hotter than their maximum growth temperature, is less understood. To test whether thermophilic endospores can survive prolonged exposure to high temperatures, sediments were incubated at 80–90°C for 6, 12 or 463 days. Sediments were then cooled by 10–40°C, mimicking the cooling in subsurface oil reservoirs subjected to seawater injection. Cooling the sediments induced sulfate reduction, coinciding with an enrichment of endospore-forming Clostridia. Different Desulfofundulus, Desulfohalotomaculum, Desulfallas, Desulfotomaculum and Desulfofarcimen demonstrated different thermal tolerances, with some Desulfofundulus strains surviving for >1 year at 80°C. In an oil reservoir context, heat-resistant endospore-forming sulfate-reducing bacteria have a survival advantage if they are introduced to, or are resident in, an oil reservoir normally too hot for germination and growth, explaining observations of reservoir souring following cold seawater injection. 相似文献
3.
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 HgCl 2 was similar between Enz-I and Enz-II, while that to D-cycloserine, L- and D-aminoethylphosphonic acid, monoiodoacetate and
N-ethylmaleimide was different; HgCl 2 was the most effective inhibitor among these compounds.
Received December 13, 1999, Accepted January 11, 2000 相似文献
4.
Sporulation in Bacillus megaterium var phosphaticum (PB — 1) was induced using modified nutrient media. This modified medium induced sporulation within 36 h. After spore induction
the spores were kept under refrigerated (5°C) and room temperature (32°C) for five months and survival of spores was studied
at 15 days intervals by plating them in nutrient agar medium. It was observed that there was not much variation in the storage
temperature (5°C & 32°C). The spore cells of Bacillus megaterium var phosphaticum (PB — 1) were observed up to five months of storage under refrigerated (5°C) and room temperature (32°C). Regeneration of
spore cells into vegetative cells was studied in tap water, rice gruel, nutrient broth, sterile lignite and sterile water
at different concentrations of spore inoculum. The multiplication of sporulated Bacillus megaterium var phosphaticum culture was fast and reached its maximum (29.5 × 10 8 cfu ml −1) in nutrient broth containing 5 per cent inoculum level. 相似文献
5.
RNA was extracted from dormant and germinating Bacillus subtilis 168 spores (intact spores and chemically decoated spores) by using rapid rupture followed by acid–phenol extraction. Spore
germination progress was monitored by assaying colony forming ability before and after heat shock and by reading the optical
density at 600 nm. The purity, yield, and composition of the extracted RNA were determined spectrophotometrically from the
ratio of absorption at 260 nm to that at 280 nm; in a 2100 BioAnalyzer, giving the RNA yield/10 8 spores or cells and the distribution pattern of rRNA components. The method reported here for the extraction of RNA from
dormant spores, as well as during different phases of germination and outgrowth, has proven to be fast, efficient and simple
to handle. RNA of a high purity was obtained from dormant spores and during all phases of germination and growth. There was
a significant increase in RNA yield during the transition from dormant spores to germination and subsequent outgrowth. Chemically
decoated spores were retarded in germination and outgrowth compared with intact spores, and less RNA was extracted; however,
the differences were not significant. This method for RNA isolation of dormant, germinating, and outgrowing bacterial endospores
is a valuable prerequisite for gene expression studies, especially in studies on the responses of spores to hostile environmental
conditions. 相似文献
6.
The physicochemical properties of spores were studied in relationship of their structure, which was modulated by chemical
or genetic methods. The Bacillus subtilis spores were equilibrated at different water activities (from 0.113 to ~1) and investigated by differential scanning calorimetry
(DSC). The isothermal sorptions at 25 °C of the native and the modified spores were also used to analyse the DSC results.
As already reported in literature, an endothermic peak in DSC was found at about 70 °C, but a previously unreported baseline
shift, a ∆Cp step, was also observed at −69 °C. The endothermic peak found at 70 °C was assigned to a material relaxation
which corresponded to a structure change from a less mobile state to a more mobile state. The spore cortex material seems
to be mainly implicated in this event. The ∆Cp step observed at −69 °C was identified as a glass transition of the water in
the spore protoplast. These results showed that at room temperature, the physical state of the components within B. subtilis spores equilibrated at water activity levels below 0.3 was different: The cortex material is in a low mobility state whereas
confined structure of protoplast and its internal hydration level allow a certain mobility of water molecules. 相似文献
7.
Bacillus subtilis fmbj can produce a lipopeptide antimicrobial substance, the main components of which are surfactin and fengycin. In this
paper, the sensitivity of Bacillus cereus to antimicrobial lipopeptides from B.
subtilis fmbj was observed, and the effect of the microstructure of antimicrobial lipopeptide on spores of B.
cereus was investigated. At the same time, the optimization of the inactivation of antimicrobial lipopeptides to spores of B.
cereus by a response surface methodology was studied. Results showed that B.
cereus had high sensitivity to it, whose minimal inhibitory concentration was 156.25 μg/ml. It could result in the death of spores
by destroying the structure of resting spores and sprouting spores, as was observed by transmission electron microscopy. The
optimization result indicated that spores of B.
cereus could be inactivated by 2 orders of magnitude when the temperature was 29.6°C, the action time was 7.6 h, and the concentration
was 3.46 mg·ml −1. 相似文献
8.
Bacterial formulations, produced using both Bacillus megaterium and B. pumilus individually with pharmaceutical technology, were formulated using a wet granular method. Viability testing in the laboratory
revealed that bacterial populations rapidly declined during storage at room temperature (26–30 °C) for 6 months. The scanning
electron microscope (SEM) was used to observe bacterial formulations. Both endospores and vegetative cells of B. megaterium and B. pumilus were detected on the formulation surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
In Bacillus 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 (T 2–T 3), 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 T 4–T 5. Protein turnover rate increased again after T 2 and up to T 8 60–70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T 3 no asymmetric septa were observed and the amount of heat-resistant spores at T 8 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 T 3 but then its velocity sharply dropped and the amount of degraded protein at T 8 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 (T 2.5), 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 (T 4) shift to SST had no effect on the sporulation process. 相似文献
10.
In recent years, considerable and growing attention has been given to the application of host-associated microorganisms as a more suitable source of probiotics in aquaculture sector. Herein, we isolated and screened the olive flounder gut microbiota for beneficial bacterial strains that might serve as potential probiotics in a low fishmeal extruded aquafeed. Among the ten identified isolates, Bacillus amyloliquefaciens SK4079 and B. subtilis SK4082 were screened out based on their heat-resistant ability as well as enzymatic and non-hemolytic activities. Although both strains were well able to utilize carboxymethyl cellulose (CMC), xylan, and soybean meal (SBM) as a single carbon source in the minimal nutrient M9 medium, B. subtilis exhibited significantly higher cellulase, xylanase, and protease activities than B. amyloliquefaciens. The two selected strains were well able to degrade the undesirable anti-nutritional component of the SBM, which would limit its utilization as protein source in aquafeed industry. Significantly higher biofilm formation capacity and notably stronger adhesive interactions with the flounder’s skin mucus were detected in B. subtilis than B. amyloliquefaciens. Immobilization of the spores from the selected strains, in a SBM complex carrier, remarkably enhances their thermal resistance at 120 °C for 5 min and different drying conditions. It was also interesting to learn that the B. subtilis spores could survive and remain viable after being sprayed onto extruded low-fish meal feed pellets for as long as 6 months. Overall, the findings of the present study could help the food/feed industries achieve their goal of developing cost-effective yet efficient products. 相似文献
11.
Preservation of algal spores of the green seaweed Ulva fasciata and U. pertusa was enhanced by the addition of ampicillin in f/2 medium at 4°C. The viability of preserved spores was determined by a spore
germination assay at various time intervals. The germination rate of U. fasciata remained at 5% to 38% for the first five days, dropping to 1% to 6% on the 10th day of storage with various preservation
treatments without ampicillin at 4°C during parameter-selecting experiments. In f/2 medium, 53% of U. fasciata spores were still viable on day 5 and 23% on day 10 at 4°C. By adding 100 μg mL −1 ampicillin to f/2 medium, 90% of the spores were viable at day 40 and 61% after 100 days of storage at 4°C. Spores of U. pertusa had lower preservation rates, with viabilities of 70% at day 40 and 32% at day 100. Algal spore preservation was heavily
dependent on the bacterial contamination and subsequent degradation in stock solutions.
Handling editor: L. Naselli-Flores 相似文献
12.
Bacillus subtilis 115 grew in a medium with amino acids and glucose with the maximum specific growth rates μ of 1.20-1.10/h in the temperature
range of 45–48°C. Activity of the extracellular neutral proteinase excreted by 1.3 mg/mL dry mass during 8 h of the postexponential
and stationary growth phases decreased from its maximum value of 0.23 TU/mL at 40°C to 0.13 and 0.06 TU/mL at 45 and 48°C,
respectively. Formation of the extracellular serine proteinase decreased even more—from 0.18 TU/mL at 40°C to 0.06 and 0.03
TU/mL at 45 at 48°C, respectively. Sporulation, expressed as the portion of sporangia rith refractile spores at the 6th h
of the stationary phase decreased from 46% at 40°C to 17 and 3% at 45 and 48°C, respectively. 相似文献
13.
The changes in the state of Bacillus subtilis spores that occur during germination were analyzed using dynamic phase microscopy (DPM). DPM is based on monitoring and analyzing the interference image of a specimen in a coherent laser beam. The optical path difference (the phase thickness of the specimen, PT) depends on the geometrical height of the specimen and its refractive index. We demonstrated that the maximum PT value is a convenient criterion of the physiological state of the organism involved: PT is ≥ 80 nm, ~40–50 nm, and ≤ 20 in dormant, developing (initiated), and heat-killed spores, respectively. We established that (i) heating a spore suspension to 40°C results in a reversible twofold decrease (from 80 to 40 nm) in their PT under conditions that do not promote the development of the bacteria; this decrease is irreversible under growth-promoting conditions; (ii) the PT values of germinating spores oscillate with a considerable fluctuation amplitude (up to 7 nm), in contrast to the limited fluctuation amplitude (within 1 nm) in dormant spores; (iii) activated spores were heterogenous with respect to the PT pattern: a majority of the spores exhibited a usual spatial profile (with a maximum thickness in the center), whereas a minor fraction of them were characterized by an erythrocyte-like profile with a concave center; this implies that the central zone of the spore was more rapidly hydrated (with a decrease in refractive index) than the peripheral zone. 相似文献
14.
Seasonally acclimatized adult and immature parasites of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby, were exposed to high or low temperature extremes for 3 h periods. Death of all summer adults of Encarsia opulenta Silvestri and E. smithi Silvestri occurred between 35° and 40°C. Within CBF hosts, E. opulenta were not able to emerge when temperatures reached between 45° and 50°C. In winter experiments adults of both Encarsia species succumbed between −5° and −10°C. In a comparison of the 2 seasonal tests, a higher percentage of E. smithi adults were able to survive both higher and lower temperatures than E. opulenta, but the main interspecific difference was the ability of E. opulenta within CBF to survive −10° to − 15°C while E. smithi did not. Limited data for Amitus hesperidum Silvestri [ Hym.: Platygasteridae] indicated that the immatures survived better at low, and not as well at high, temperatures as either species of Encarsia.
Florida Agricultural Experiment Station Journal Series # 5549. 相似文献
15.
Lethal heating induces DNA single strand breakage in bacterial endospores as detected by the alkaline sucrose gradient centrifugation technique. Heating of spores of 168 at 90°C for 10, 30, and 60 min induced 6, 15, and 15 single strand breaks, respectively and inactivated 6%, 98.2%, and 99.974% of the spores. This is the first report to our knowledge identifying specifically single strand DNA breakage with lethal heat injury of bacterial spores. 相似文献
16.
In a two-phase operation, E. coli containing λSNNU1 ( Q
−
S
−) in the chromosome is typically cultured at 33°C and cloned gene expression is induced by elevating the temperature. At least
40°C is necessary for complete induction of cloned gene expression; however, temperatures above 40°C have been shown to inhibit
cloned gene expression. This suggests that a three-phase operation, which has an induction phase between the growth and production
phases, may result in higher gene expression. In this study, optimal temperature management strategies were investigated for
the three-phase operation of cloned gene expression in thermally inducible E. coli/bacteriophage systems. The optimal temperature for the induction phase was determined to be 40°C. When the temperature of
the production stage was 33°C, the optimal time period for the induction phase at 40°C was determined to be 60 min. In contrast,
when the temperature of the production phase was 37°C, the optimal period for the induction phase at 40°C was 20∼30 min. When
the three-phase temperature and temporal profile were set at a growth phase of 33°C, an induction phase at 40°C for 30 min,
and a production phase at 37°C, the highest level of cloned gene expression was achieved. 相似文献
17.
A phytase with high activity at neutral pH and typical water temperatures (∼25°C) could effectively hydrolyze phytate in aquaculture.
In this study, a phytase-producing strain, Pedobacter nyackensis MJ11 CGMCC 2503, was isolated from glacier soil, and the relevant gene, PhyP, was cloned using degenerate PCR and thermal asymmetric interlaced PCR. To our knowledge, this is the first report of detection
of phytase activity and cloning of phytase gene from Pedobacter. PhyP belongs to beta-propeller phytase family and shares very low identity (∼28.5%) with Bacillus subtilis phytase. The purified recombinant enzyme (r-PhyP) from Escherichia coli displayed high specific activity for sodium phytate of 24.4 U mg −1. The optimum pH was 7.0, and the optimum temperature was 45°C. The K
m, V
max, and k
cat values were 1.28 mM, 71.9 μmol min −1 mg −1, and 45.1 s −1, respectively. Compared with Bacillus phytases, r-PhyP had higher relative activity at 25°C (r-PhyP (>50%), B. subtilis phytase (<8%)) and hydrolyzed phytate from soybean with greater efficacy at neutral pH. These characteristics suggest that
r-PhyP might be a good candidate for an aquatic feed additive in the aquaculture industry. 相似文献
18.
In this communication, we report the presence of a newly identified serine alkaline protease producing bacteria, Virgibacillus pantothenticus (MTCC 6729) in the fresh chicken meat samples and the factors affecting biosynthesis as well as characterization of protease.
The strain produced only 14.3 U ml −1 protease in the standard medium after 72 h of incubation, while in optimized culture conditions the production of protease
was increased up to 18.2 U ml −1. The strain was able to produce protease at 40°C at pH 9.0. The addition of dextrose and casein improved protease production.
The protease was partially purified and characterized in terms of pH and temperature stability, effect of metal ions and inhibitors.
The protease was found to be thermostable alkaline by retaining its 100% and 85% stability at pH 10.0 and at 50°C respectively.
The protease was compatible with some of the commercial detergents tested, and was effective in removing protein stains from
cotton fabrics. The V. pantothenticus, MTCC 6729 protease appears to be potentially useful as an additive in detergents as a stain remover and other bio-formulations. 相似文献
19.
Nattokinase producing bacterium, B. subtilis YF38, was isolated from douchi, using the fibrin plate method. The gene encoding this enzyme was cloned by polymerase chain reaction (PCR). Cytoplasmic
expression of this enzyme in E. coli resulted in inactive inclusion bodies. But with the help of two different signal peptides, the native signal peptide of nattokinase
and the signal peptide of PelB, active nattokinase was successfully expressed in E. coli with periplasmic secretion, and the nattokinase in culture medium displayed high fibrinolytic activity. The fibrinolytic
activity of the expressed enzyme in the culture was determined to reach 260 urokinase units per micro-liter when the recombinant
strain was induced by 0.7 mmol l −1 isopropyl-β-D- thiogalactopyranoside (IPTG) at 20°C for 20 h, resulting 49.3 mg active enzyme per liter culture. The characteristic
of this recombinant nattokinase is comparable to the native nattokinase from B. subtilis YF38. Secretory expression of nattokinase in E. coli would facilitate the development of this enzyme into a therapeutic product for the control and prevention of thrombosis diseases. 相似文献
20.
Bacterial spores are commonly isolated from a variety of different environments, including extreme habitats. Although it is well established that such ubiquitous distribution reflects the spore resistance properties, it is not clear whether the growing conditions affect the spore structure and function. We used Bacillus subtilis spores of similar age but produced at 25, 37, or 42°C to compare their surface structures and functional properties. Spores produced at the 25°C were more hydrophobic while those produced at 42°C contained more dipicolinic acid, and were more resistant to heat or lysozyme treatments. Electron microscopy analysis showed that while 25°C spores had a coat with a compact outer coat, not tightly attached to the inner coat, 42°C spores had a granular, not compact outer coat, reminiscent of the coat produced at 37°C by mutant spores lacking the protein CotG. Indeed, CotH and a series of CotH-dependent coat proteins including CotG were more abundantly extracted from the coat of 25 or 37°C than 42°C spores. Our data indicated that CotH is a heat-labile protein with a major regulatory role on coat formation when sporulation occurs at low temperatures, suggesting that B. subtilis builds structurally and functionally different spores in response to the external conditions. 相似文献
|