scholarly journals Ecotoxicology of sediment in the estuary of the Jundiaí and Potengi Rivers in Natal-RN, Brazil, by using Leptocheirus plumulosus as test-organism

2018 ◽  
Vol 13 (2) ◽  
pp. 77-84
Author(s):  
R.B. Lopes ◽  
R.F. Souza ◽  
S.T.T. Silva-Nicodemo ◽  
J.V.F. Cruz ◽  
G.F. Medeiros
Keyword(s):  
Test Organism ◽  
Leptocheirus Plumulosus

scholarly journals Chronic arsenate exposure affects amphipod size distribution and reproduction

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8645
Author(s):  
Ioanna Visviki ◽  
Michael L. Judge
Keyword(s):  
Sex Ratio ◽  
Size Distribution ◽  
Test Organism ◽  
Quality Criteria ◽  
Sublethal Concentration ◽  
Water Quality Criteria ◽  
Offspring Sex Ratio ◽  
Leptocheirus Plumulosus ◽  
Chronic Effects ◽  
Inorganic Species

Arsenate (As V) is the predominant inorganic species of arsenic in oxic aquatic environments. Chronic water quality criteria for arsenate have not been established due to the scarcity of relevant studies on its impact on aquatic biota. We examined the acute and chronic effects of arsenate on the benthic amphipod Leptocheirus plumulosus, an important test organism for ecotoxicological studies. We determined that a concentration of 1,971 µg/L arsenate induced 50% mortality (LC50) in juveniles in 96-hr water only exposure. Subsequently, we tested the efficacy of a 42-day sediment bioassay to determine chronic population-level effects. Specifically, we analyzed the survivorship, size distribution, reproduction and offspring sex ratio of this amphipod to a sublethal concentration of arsenate. The sublethal concentration was determined based on the results of the acute tests. Arsenate (500 µg/L) was added to seawater (20 psu) overlying natural sediments (particle sizes < 250 µm). Fifteen replicate chambers per treatment were employed, each stocked with 20 stage-sorted juvenile amphipods (500–600 µm). Five replicates per treatment were destructively sampled on week 3 and ten replicates were sampled on week 6. Arsenate exposure did not affect the survivorship of parental amphipods, as expected, but it decreased significantly the number of offspring in the largest size classes. By week 6, arsenate-exposed replicates had statistically fewer sexually mature offspring compared to controls, likely because the overall reproduction was suppressed. Arsenate exposed amphipods had significantly fewer offspring than controls by week 6 (9.3 vs. 19.1 per parent), but the sex ratio of the offspring was not altered. Our results indicate that size distribution and reproduction may be more sensitive endpoints than survivorship for the chronic effects of arsenate in oxic systems. The extended 42-day bioassay with Leptocheirus plumulosus is a very promising tool to study the effects of toxicants on population dynamics.

Modified Assay Medium for the Turbidimetric Assay of Chlortetracycline in Feeds

1976 ◽  
Vol 59 (3) ◽  
pp. 536-539
Author(s):  
Hussein S Ragheb
Keyword(s):  
Growth Rate ◽  
Excellent Agreement ◽  
Test Organism ◽  
Plate Method ◽  
Assay Sensitivity ◽  
Assay Medium ◽  
Turbidimetric Method ◽  
Turbidimetric Assay ◽  
Commercial Feeds ◽  
Lower Recovery

Abstract In previous experiments, the turbidimetric method for determining chlortetracycline-HCI (CTC-HCl) in feeds showed lower recovery than the AOAC plate method. Although the addition of vitamins to the turbidimetric medium improved results, values by the turbidimetric method remained about 10% lower than by the plate method. A modified (1.7 × the weight recommended by the manufacturer) turbidimetric assay medium decreased assay sensitivity but did not significantly change the slope of S. aureus response to CTC-HCl. There was no evidence that vitamin fortification of the modified medium had any significant effect on the growth rate of test organism. Examination of about 100 samples of commercial feeds containing CTC-HCl showed excellent agreement in results between the turbidimetric and plate methods.

scholarly journals THE EFFECT OF THE pH ON THE GERMICIDAL ACTION OF SOAPS

1926 ◽  
Vol 10 (1) ◽  
pp. 147-160 ◽  
Author(s):  
Arnold H. Eggerth
Keyword(s):  
Surface Tension ◽  
Acid Solution ◽  
Partition Coefficient ◽  
Test Organism

1. The effect of the pH on the germicidal action of soaps has been studied. The lower members of the series were found to be most active in acid solution; the higher members, in alkaline. The point of transition varied with the test organism used. 2. This is probably due to the effect of the pH on the dissociation residue and on the solubility of the soap. The dissociation residue may affect the germicidal titer by modifying the surface tension, the penetration into the bacteria, and the partition coefficient of the germicide between bacteria and water. See PDF for Structure

Toxicity of 39 MEIC Chemicals to Bioluminescent Photobacteria (The Biotox™ Test): Correlation with Other Test Systems

1994 ◽  
Vol 22 (3) ◽  
pp. 147-160 ◽  
Author(s):  
Anne Kahru ◽  
Barbara Borchardt
Keyword(s):  
Toxic Substance ◽  
Light Output ◽  
Test Organism ◽  
Toxicity Testing ◽  
Correlation Coefficients ◽  
Photobacterium Phosphoreum ◽  
Short Term ◽  
Freeze Dried ◽  
Light Loss ◽  
Test Correlation

Photobacterium phosphoreum are naturally luminescent marine bacteria, which emit light as a result of metabolism. Any damage to the cellular metabolism caused by a toxic substance can therefore be monitored by measuring the change in light output of the bacteria, the light loss being proportional to the degree of toxicity. The Biotox™ test, based on reconstituted freeze-dried (viable) Photobacterium phosphoreum as the test organism, was used for the short-term toxicity testing of 39 chemicals from the MEIC list. Concentration-effect curves for these 39 chemicals were measured and five-minute EC50 values (the concentration of chemical, mM, which reduces the light output of the bacteria by 50% after contact for five minutes) were calculated. The EC50 data from the Biotox test were correlated with data from the literature: octanol/water partition coefficients, EC50 data from the Microtox™ test, minimal inhibitory concentration values for Escherichia coli and Bacillus subtilis and acute toxicity data from animal and human cell lines, rodents and man. The correlation coefficients ranged between 0.63 and 0.93.

Bioaerosol Exposure Method for Package Integrity Testing†

1996 ◽  
Vol 59 (7) ◽  
pp. 768-771 ◽  
Author(s):  
SCOTT W. KELLER ◽  
JOSEPH E. MARCY ◽  
BARBARA A. BLAKISTONE ◽  
GEORGE H. LACY ◽  
CAMERON R. HACKNEY ◽  
...  
Keyword(s):  
Particle Size ◽  
Test Organism ◽  
Hole Diameter ◽  
Pseudomonas Fragi ◽  
Integrity Testing ◽  
Aerosol Exposure ◽  
Exposure Method ◽  
Test Organisms ◽  
Organism Growth ◽  
Bioaerosol Exposure

Test organism motility, concentration, aerosol exposure time, hole diameter and length were evaluated to determine their influence on microbial ingress into a flexible plastic pouch. Microtubes with 10- and 20-μm hole diameters and of 5- and 10-mm lengths were used as defects in 128 flexible pouches. A bioaerosol with a 2.68-μm mean particle size comprised of 102 or 106 CFU/ml source concentrations of motile or nonmotile Pseudomonas fragi TM 849 was introduced into a 119,911-cm3 chamber for exposures of 15 or 30 minutes. Six pouches showed test organism growth after a 72-h incubation period. Microbial ingress was significant (P &lt; .05) for motile test organisms with source concentrations of 106 CFU/ml.

Effect of Temperature and Contact Time on the Activity of Eight Disinfectants - A Classification

1984 ◽  
Vol 47 (11) ◽  
pp. 841-847 ◽  
Author(s):  
P. GÉLINAS ◽  
J. GOULET ◽  
G. M. TASTAYRE ◽  
G. A. PICARD
Keyword(s):  
Quaternary Ammonium ◽  
Contact Time ◽  
Test Organism ◽  
Amphoteric Surfactant ◽  
Effect Of Temperature ◽  
Dilution Method ◽  
Ammonium Compound ◽  
Optimum Growth Temperature ◽  
Ammonium Compounds

The combined influence of temperature (4, 20, 37 and 50°C) and contact time (10, 20 and 30 min) on the efficacy of eight commercial disinfectants was evaluated by the Association of Official Analytical Chemists use-dilution method. An increase of temperature greatly enhanced the activity of all tested solutions, particularly glutaraldehyde, chlorhexidine acetate and the amphoteric surfactant, whereas contact time mainly enhanced the efficacy of sodium hypochlorite, the quaternary ammonium compound and the amphoteric surfactant. Temperature and contact time influenced the activity profile of the disinfectants tested, with a maximum efficacy near the optimum growth temperature (37°C) of the test organism (Pseudomonas aeruginosa ATCC 15442). This organism was highly resistant to the amphoteric surfactant as well as to the two quaternary ammonium compounds. Classification of disinfectants is proposed on the basis of their mode of action, temperature dependence and activation energies, heat and light stability, and tolerance to organic matter.

Reduction of Microorganisms on Citrus Fruit Surfaces during Packinghouse Processing

1998 ◽  
Vol 61 (7) ◽  
pp. 903-906 ◽  
Author(s):  
STEVEN PAO ◽  
G. ELDON BROWN
Keyword(s):  
Test Organism ◽  
Citrus Fruit ◽  
Microbial Populations ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Plate Counts ◽  
High Level ◽  
Inoculation Study ◽  
Fruit Surface

Citrus fruit surface microbial populations were evaluated following various packingline processes of seven Florida commercial packinghouses. At each packinghouse, six fruits (oranges or tangerines) were collected at each of four sampling points. The sampling was conducted in duplicate; thus, 336 fruit were evaluated during this survey. Average aerobic plate counts and yeast and mold counts on fruit surfaces before washing were about 4.0 log CFU/cm2 and 3.3 log CFU/cm2, respectively, and were reduced to 2.1 log CFU/cm2 and 1.3 log CFU/cm2, respectively, by packinghouse processing. Waxing alone reduced the average fruit surface aerobic plate counts and coliform counts from 3.7 log CFU/cm2 and 35.2 most probable number (MPN)/cm2, respectively, to 2.6 log CFU/cm2 and 1.4 MPN/cm2. No Escherichia coli was recovered from fruit at the end of packinghouse processing, and no salmonellae were found on fruit during the entire processing. In an inoculation study to test the effect of packinghouse processes, test organism E. coli was applied to fruit to achieve a high level (4.8 log CFU/cm2) of contamination. The average E. coli count was reduced about 2.4 log cycles by washing and rinsing with potable water (40 psi, 25 °C) for about 30 s. The combination of washing and waxing significantly reduced the inoculated level of E. coli from 4.8 to 1.4 log CFU/cm2.

Use of Azolla as a test organism in a growth chamber of simple design

1987 ◽  
Vol 99 (2-3) ◽  
pp. 219-230 ◽  
Author(s):  
Harro W. Wong Fong Sang ◽  
Vu van Vu ◽  
Jan W. Kijne ◽  
Vu Thanh Tam ◽  
Kees Planque
Keyword(s):  
Test Organism ◽  
Growth Chamber ◽  
Simple Design
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