scholarly journals Suppositional measures for harmful microalga Pseudo-nitzschia calliantha control in aquaculture farms

2015 ◽  
Vol 183 (4) ◽  
pp. 236-241
Author(s):  
Nina A. Aizdaicher ◽  
Zh. V. Markina
Keyword(s):  
Exponential Growth ◽  
Laboratory Culture ◽  
Water Circulation ◽  
Lag Phase ◽  
Water Mixing ◽  
Toxic Species ◽  
Cyclic Dynamics ◽  
Vessel Bottom ◽  
Olive Green

Growth of potentially toxic diatom microalga Pseudo-nitzschia calliantha is investigated in laboratory culture under different conditions of cultivation. In the conditions without stirring, the highest abundance of algae was moderate (16131 cells/ml) and observed after 3 days of exposition; many chains of 5-8 cells were formed. Further exposition showed cyclic dynamics of the culture, the chains of 5-12 cells were numerous, chloroplasts looked healthy, their color was olive-green. After stirring, a short lag-phase preceded to the phase of active cells dividing with exponential growth of their number to the peaks of 59828-70566 cells/ml, chains of 2-8 cells were formed but rapidly settled to the vessel bottom, chloroplasts were discrete and bleached that indicated dying of the culture. P. calliantha is potentially toxic species, so the sites with active water circulation or constrained water mixing are recommended for aquaculture farming that protects the environments from its phycotoxins accumulation.

Validation and Analysis of Modeled Predictions of Growth of Bacillus cereus Spores in Boiled Rice

2000 ◽  
Vol 63 (2) ◽  
pp. 268-272 ◽  
Author(s):  
DANA M. McELROY ◽  
LEE-ANN JAYKUS ◽  
PEGGY M. FOEGEDING
Keyword(s):  
Growth Rate ◽  
Bacillus Cereus ◽  
Exponential Growth ◽  
Generation Time ◽  
Time Lag ◽  
Lag Phase ◽  
Exponential Growth Rate ◽  
Phase Duration ◽  
Margin Of Safety ◽  
Fail Safe

The growth of psychrotrophic Bacillus cereus 404 from spores in boiled rice was examined experimentally at 15, 20, and 30°C. Using the Gompertz function, observed growth was modeled, and these kinetic values were compared with kinetic values for the growth of mesophilic vegetative cells as predicted by the U.S. Department of Agriculture's Pathogen Modeling Program, version 5.1. An analysis of variance indicated no statistically significant difference between observed and predicted values. A graphical comparison of kinetic values demonstrated that modeled predictions were “fail safe” for generation time and exponential growth rate at all temperatures. The model also was fail safe for lag-phase duration at 20 and 30°C but not at l5°C. Bias factors of 0.55, 0.82, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, indicated that the model generally was fail safe and hence provided a margin of safety in its growth predictions. Accuracy factors of 1.82, 1.60, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, quantitatively demonstrated the degree of difference between predicted and observed values. Although the Pathogen Modeling Program produced reasonably accurate predictions of the growth of psychrotrophic B. cereus from spores in boiled rice, the margin of safety provided by the model may be more conservative than desired for some applications. It is recommended that if microbial growth modeling is to be applied to any food safety or processing situation, it is best to validate the model before use. Once experimental data are gathered, graphical and quantitative methods of analysis can be useful tools for evaluating specific trends in model prediction and identifying important deviations between predicted and observed data.

Analysis of the lag phase to exponential growth transition by incorporating inoculum characteristics

2011 ◽  
Vol 28 (4) ◽  
pp. 656-666 ◽  
Author(s):  
A.J. Verhulst ◽  
A.M. Cappuyns ◽  
E. Van Derlinden ◽  
K. Bernaerts ◽  
J.F. Van Impe
Keyword(s):  
Exponential Growth ◽  
Lag Phase

scholarly journals Lag Phase Is a Distinct Growth Phase That Prepares Bacteria for Exponential Growth and Involves Transient Metal Accumulation

2011 ◽  
Vol 194 (3) ◽  
pp. 686-701 ◽  
Author(s):  
M. D. Rolfe ◽  
C. J. Rice ◽  
S. Lucchini ◽  
C. Pin ◽  
A. Thompson ◽  
...  
Keyword(s):  
Growth Phase ◽  
Exponential Growth ◽  
Metal Accumulation ◽  
Lag Phase

scholarly journals CHARACTERISTICS OF LACTOBACTERIA STRAINS, HAVING DIAGNOSTIC SIGNIFICANCE IN GYNECOLOGICAL PRACTICE

2019 ◽  
Vol 64 (2) ◽  
pp. 111-116
Author(s):  
A. P. Godovalov ◽  
T. Yu. Danielyan ◽  
T. I. Karpunina
Keyword(s):  
Lactic Acid ◽  
Microscopic Examination ◽  
Exponential Growth ◽  
Functional Activity ◽  
Lactate Production ◽  
Synthetic Activity ◽  
Lag Phase ◽  
Adaptation Period ◽  
Clinical Strains ◽  
Lactobacillus Spp

Nowadays, in the presence of wide diagnostic possibilities, laboratory diagnostics of microecological disorders of vaginal biotope are often limited to clinical data, microscopic examination results and the use of a culture method. However, with such a complex it is impossible to get an answer about the functional activity of microorganisms. The aim of investigation was to evaluate the information content of a combined study of growth parameters and the ability to produce lactic acid by clinical strains of Lactobacillus spp. to characterize the state of the microecology of the cervical-vaginal biotope. Materials and methods. Studied the growth kinetics of strains of lactobacilli isolated from the detachable posterior vaginal fornix. The concentration of lactic acid in the medium was determined using the “Lactic Acid - Olvex” kit (Russia). Samples were taken every 12 hours of cultivation. Statistical analysis of the results was performed using the methods of descriptive statistics, Student’s t-test. Results. It has been shown that 44% of Lactobacillus spp. to 72 hours of cultivation did not reach the phase of exponential growth. The remaining strains from 12-24 hours passed into the phase of exponential growth. In the production of lactic acid, the strains that are in the lag-phase did not differ from each other, since they practically did not synthesize this metabolite. Among the remaining strains that are in the phase of exponential growth, some did not produce lactic acid, others increased their lactate production every hour. Part of the strains reached the peak of acid production by 36 hours and by 72 hours some decrease in synthetic activity was observed. Conclusion. It has been shown that for most vaginal strains of Lactobacillus spp. characteristic variability of the duration of the adaptation period and the level of functional activity. In addition, only a small number of clinical strains produced lactic acid 24 hours after the start of cultivation. Therefore, to adequately assess the microecological status of the vaginal biotope, microscopic examination of both native material and cultures isolated on special nutrient media is not enough. It seems that, along with the use of modern methods of genetic analysis, the determination of in vitro growth characteristics, primarily lag-phase duration, and lactate production by lactic acid bacteria strains can clarify many issues related to the formation of dysbiotic states, in particular, in the vaginal biotope, and will also serve to increase the effectiveness of the prescribed treatment.

scholarly journals Inositol transport in Saccharomyces cerevisiae is regulated by transcriptional and degradative endocytic mechanisms during the growth cycle that are distinct from inositol-induced regulation.

1996 ◽  
Vol 7 (1) ◽  
pp. 81-89 ◽  
Author(s):  
K S Robinson ◽  
K Lai ◽  
T A Cannon ◽  
P McGraw
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Stationary Phase ◽  
Exponential Growth ◽  
Growth Cycle ◽  
Endocytic Pathway ◽  
Negative Regulator ◽  
Lag Phase ◽  
Free Medium ◽  
Uptake Activity ◽  
Inositol Uptake

Regulation of inositol uptake activity in Saccharomyces cerevisiae during the growth cycle was examined. Activity increased as the cell population transited from lag phase to exponential growth, and continued to increase until late exponential phase. The increase in activity was due to increased transcription of the ITR1 gene and synthesis of the Itr1 permease. When the culture reached stationary phase, uptake activity decreased and dropped to a minimum within 4 h. The decrease was due to repression of ITR1 transcription, independent of the negative regulator Opi1p, and degradation of the existing permease. Degradation depended on delivery of the permease to the vacuole through the END3/END4 endocytic pathway. During exponential growth in inositol-containing medium the permease is also rapidly degraded, whereas in inositol-free medium the permease is highly stable. Rapid degradation of the permease at stationary phase occurred in inositol-free medium, indicating that there are two distinct mechanisms that trigger endocytosis and degradation in response to different physiological stimuli. In addition, the level of the enzyme required for inositol biosynthesis, inositol-1-phosphate synthase, encoded by INO1, is not reduced in stationary-phase cells, and this contrast in the regulation of inositol supply is discussed.

Effects and Interactions of Temperature, pH, Atmosphere, Sodium Chloride, and Sodium Nitrite on the Growth of Listeria monocytogenes

1989 ◽  
Vol 52 (12) ◽  
pp. 844-851 ◽  
Author(s):  
ROBERT L. BUCHANAN ◽  
HEIDI G. STAHL ◽  
RICHARD C. WHITING
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Sodium Nitrite ◽  
Exponential Growth ◽  
Chloride Content ◽  
Lag Phase ◽  
Growth Data ◽  
Phase Duration ◽  
Degree Of Protection ◽  
Cured Meats

The effects and interactions of temperature (5, 19, 28, 37°C), initial pH (6.0 and 7.5), atmosphere (aerobic and anaerobic), sodium chloride content (0.5 and 4.5%), and sodium nitrite concentration (0, 50, 100, 200, 1000 μg/ml) on the growth of Listeria monocytogenes Scott A were determined using Tryptose Phosphate Broth. Growth data were analyzed by regression analysis to generate “best-fit” Gompertz equations, which were used subsequently to calculate lag phase duration, exponential growth rate, generation time, and maximum population density values. The data indicated that the growth kinetics of L. monocytogenes was dependent on the interaction of the five variables, particularly in regard to exponential growth rates and lag phase durations. The data suggest that sodium nitrite can have significant bacteriostatic activity against L. monocytogenes and may provide cured meats with a degree of protection against this microorganism, particularly if employed in conjunction with a combination of acidic pH, vacuum packaging, high salt concentrations, and adequate refrigeration.

scholarly journals Modeling the Lag Period and Exponential Growth of Listeria monocytogenes under Conditions of Fluctuating Temperature and Water Activity Values

2010 ◽  
Vol 76 (9) ◽  
pp. 2908-2915 ◽  
Author(s):  
Marina Muñoz-Cuevas ◽  
Pablo S. Fernández ◽  
Susan George ◽  
Carmen Pin
Keyword(s):  
Water Activity ◽  
Environmental Conditions ◽  
Exponential Growth ◽  
Sudden Change ◽  
Growth Conditions ◽  
Lag Phase ◽  
Fluctuating Temperature ◽  
Lag Period ◽  
Work Done ◽  
Good Agreement

ABSTRACT The dynamic model for the growth of a bacterial population described by Baranyi and Roberts (J. Baranyi and T. A. Roberts, Int. J. Food Microbiol. 23:277-294, 1994) was applied to model the lag period and exponential growth of L isteria monocytogenes under conditions of fluctuating temperature and water activity (aw) values. To model the duration of the lag phase, the dependence of the parameter h 0, which quantifies the amount of work done during the lag period, on the previous and current environmental conditions was determined experimentally. This parameter depended not only on the magnitude of the change between the previous and current environmental conditions but also on the current growth conditions. In an exponentially growing population, any change in the environment requiring a certain amount of work to adapt to the new conditions initiated a lag period that lasted until that work was finished. Observations for several scenarios in which exponential growth was halted by a sudden change in the temperature and/or aw were in good agreement with predictions. When a population already in a lag period was subjected to environmental fluctuations, the system was reset with a new lag phase. The work to be done during the new lag phase was estimated to be the workload due to the environmental change plus the unfinished workload from the uncompleted previous lag phase.

Modeling the Physiological State of the Inoculum and CO2 Atmosphere on the Lag Phase and Growth Rate of Listeria monocytogenes

2008 ◽  
Vol 71 (9) ◽  
pp. 1915-1918 ◽  
Author(s):  
ANTONIO J. DE JESÚS ◽  
RICHARD C. WHITING
Keyword(s):  
Stationary Phase ◽  
Growth Phase ◽  
Growth Rates ◽  
Exponential Growth ◽  
Physiological State ◽  
Brain Heart Infusion ◽  
Exponential Growth Phase ◽  
Lag Phase ◽  
Co2 Concentrations ◽  
Co2 Atmosphere

In previous studies, the growth of L. monocytogenes has been modeled under different CO2 headspace concentrations; however, the inoculum cells were always in the stationary phase. In this study, the growth of L. monocytogenes under different CO2 concentrations as affected by the physiological state of the cells was investigated. Exponential-growth-phase, stationary-phase, dried, and starved cells were prepared and inoculated at 5°C into brain heart infusion broths that had been preequilibrated under atmospheres of 0, 20, 40, 60, or 80% CO2 (the balance was N2). Lag-phase duration times (LDTs) and exponential growth rates were determined by enumerating cells at appropriate time intervals and by fitting the data to a three-phase linear function that has a lag period before the initiation of exponential growth. Longer LDTs were observed as the CO2 concentration increased, with no growth observed at 80% CO2. For example, the LDTs for exponential-phase, stationary-phase, starved, and dried cells were 2.21, 8.27, 9.17, and 9.67 days, respectively, under the 40% CO2 atmosphere. In general, exponential-growth-phase cells had the shortest LDT followed by starved cells and stationary-phase cells. Dried cells had the longest LDT. Exponential growth rates decreased as the CO2 concentrations increased. Once exponential growth was attained, no retained differences among the various initial physiological states of the cells for any of the atmospheres were observed in the exponential growth rates. The exponential growth rates under 0, 20, 40, 60, and 80% CO2 averaged 0.39, 0.37, 0.23, 0.23, and 0.0 log CFU/day, respectively. Dimensionless factors were calculated that describe the inhibitory action of CO2 on the LDTs and exponential growth rates for the various physiological states.

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