Toxin Production Rate Research Articles

Toxin Production by Microcystis aeruginosa as a Function of Light in Continuous Cultures and Its Ecological Significance

The effects of light intensity and light quality on toxin production by Microcystis aeruginosa were examined in continuous cultures. Light intensity had a pronounced effect on toxicity and the toxin production rate. Toxicity and the toxin production rate increased with light intensity up to an intensity of about 40 microeinsteins m s and decreased at higher light intensities, while the ratio of toxin to protein was constant at intensities of more than 40 microeinsteins m s. Light quality had only slight effects on toxicity. The results of our laboratory experiments were supported by the results of field work in which we examined toxin production at different depths in a lake. Our observations explain the mixed pattern of high and low toxicity found in a surface bloom of M. aeruginosa. Our findings also indicate that production of the peptide toxin can be uncoupled from general protein synthesis.

Dynamics and physiology of saxitoxin production by the dinoflagellatesAlexandrium spp.

Toxin content (fmol cell−1) and a suite of elemental and macromolecular variables were measured in batch cultures of the dinoflagellatesAlexandrium fundyense, A. tamarense andAlexandrium sp. from the southern New England region, USA. A different perspective was provided by semicontinuous cultures which revealed sustained, steady-state physiological adaptations by cells to N and P limitation. Two types of variability were investigated. In batch culture, changes in nutrient availability with time caused growth stage variability in toxin content, which often peaked in mid-exponential growth. A second type of variability that could be superimposed on growth stage differences is best exemplified by the high toxin content of cells grown at suboptimal temperatures. Calculations of the net rate of toxin production (R tox ; fmol cell−1 d−1) for these different culture treatments and modes made it possible to separate the dynamics of toxin production from cell division. Over a wide range of growth rates, cells produced toxin at rates approximating those needed to replace “losses” to daughter cells during division. The exception to this direct proportionality was with P limitation, which was associated with a dramatic increase in the rate of toxin production as cells stopped dividing due to nutrient limitation in batch culture. Growth stage variability in batch culture thus reflects small imbalances (generally within a factor of two) between the specific rates of toxin production and cell division. N limitation and CO2 depletion both affect pathways involved in toxin synthesis before those needed for cell division; P limitation does the opposite. The patterns of toxin accumulation were the same as for major cellular metabolites or elemental pools. The highest rates of toxin production appear to result from an increased availability of arginine (Arg) within the cell, due to either a lack of competition for this amino acid from pathways involved in cell division or to increased de novo synthesis. There were no significant changes in toxin content with either acclimated growth at elevated salinity, or with short term increases or decreases of salinity. These results demonstrate that toxin production is a complex process which, under some conditions, is closely coupled to growth rate; under other conditions, these processes are completely uncoupled. Explanations for the observed variability probably relate to pool sizes of important metabolites and to the differential response of key biochemical reactions to these pool sizes and to environmental conditions.

Effect of environmental conditions on production of toxic shock syndrome toxin 1 by Staphylococcus aureus

The kinetics of toxic shock syndrome toxin 1 (TSST-1) production by Staphylococcus aureus was studied in a fermentor in which aeration rate, atmospheric composition, pH, and temperature were controlled. The toxin was synthesized at a maximal rate during the exponential phase. High bacterial populations were not necessarily accompanied by high TSST-1 yields. Aerobiosis increased TSST-1 production, but excessive aeration had an adverse effect. Addition of CO2 enhanced TSST-1 yield by increasing toxin production rate and efficiency. Cultures with no pH control made more TSST-1 than those maintained at pH 5.5 to 7.5. Maximum TSST-1 yields were obtained when cultures were supplied with air (20 cm3/min) and CO2 (5 cm3/min) via a sintered glass sparger.

Recovery, growth, and production of heat-stable enterotoxin by Escherichia coli after copper-induced injury.

Exposure of enterotoxigenic Escherichia coli strains to a sublethal concentration (0.75 mg/liter) of copper for 3 days at 4 degrees C induced sensitivity to deoxycholate (0.1%). When placed in a complex (brain heart infusion) or a defined amino acid salt medium, the copper-injured cells recovered their tolerance to deoxycholate in 3 and 6 h, respectively, and commenced active growth. Growth and heat-stable enterotoxin production of uninjured and copper-injured cells were studied in brain heart infusion medium. A slightly altered growth curve and an initial slow rate of toxin production were observed in injured cells when compared with those corresponding uninjured controls. However, maximum heat-stable enterotoxin levels in injured cultures were comparable to those produced by uninjured cells, suggesting that the enterotoxigenic potential of copper-injured cells was fully retained.

EFFECTS OF VARIOUS CONCENTRATIONS OF SODIUM NITRITE AND POTASSIUM SORBATE ON Clostridium botulinum TOXIN PRODUCTION IN COMMERCIALLY PREPARED BACON

ABSTRACTThe study consisted of five treatments including formulations with or without sodium nitrite (120 ppm) or potassium sorbate (0.26%) or both nitrite (40, 80 ppm) and sorbate (0.26%). Packages (300 per treatment) of commercially prepared bacon were inoculated with Clostridium botulinum spores from 10 strains (5 type A and 5 type B) and temperature abused at 27°C. Uninoculated packages (100 per treatment) were also abused. The packages were visually checked for gas production during a 60‐day incubation period and tested for botulinal toxin. Spore and vegetative cell counts, aerobic total plate counts, product pH, residual nitrite depletion, and sorbate levels were also monitored. Toxic samples frequently occurred without gas, and many samples showing gas were nontoxic. Added sorbate or added nitrite extended the time to detection of first gas‐containing and first toxic samples. A combination of sorbate (0.26%) with reduced nitrite levels (40, 80 ppm) extended this time further. Nitrite or sorbate used singly in the formulation also decreased the rate of toxin production. None of the uninoculated packages was toxic, while the total number of toxic inoculated packages decreased with nitrite or sorbate in the formulations. Ninety percent of the samples from the control treatment became toxic during the 60‐day incubation period; 58.8% from the treatment with 0.26% sorbate; 22.0% from the treatment with 40 ppm nitrite and 0.26% sorbate; none from the treatment with 80 ppm nitrite and 0.26% sorbate; and 0.4% from the treatment with 120 ppm nitrite. Low nitrite‐sorbate combinations were thus effective in delaying botulinal toxin production in temperature abused bacon.

Influence of refrigeration on aflatoxin production by strains of Aspergillus flavus.

Strains of Aspergillus flavus that produce high concentrations of aflatoxin in cultures incubated at room temperature also produced these toxins in significant concentrations under conditions simulating household refrigeration (7.5° to 10 °C). The rate of toxin production at 10 °C was markedly influenced by preincubating cultures at room temperature for 24 hours. Solid cultures yielded higher concentrations of toxin than liquid cultures under the prevailing experimental conditions.

Relationship of Incubation Temperature to Viability, Rate of Growth and Toxin Production of Cl. Botulinum In Different Vegetables

Journal Article Relationship of Incubation Temperature to Viability, Rate of Growth and Toxin Production of Cl. Botulinum In Different Vegetables Get access William A. Starin William A. Starin From the Department of Hygiene and Bacteriology of the University of Chicago Search for other works by this author on: Oxford Academic PubMed Google Scholar The Journal of Infectious Diseases, Volume 38, Issue 2, February 1926, Pages 106–114, https://doi.org/10.1093/infdis/38.2.106 Published: 01 February 1926 Article history Received: 27 August 1925 Published: 01 February 1926