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Arsenic is an abundant metalloid and a dangerous pollutant when in solution under the arsenate or arsenite forms—As(V) and As(III), respectively. Since its biological effects are expected to depend on the oxidation state and on speciation, effect of pH on either As(V) or As(III) speciation and resulting toxicity was investigated using the Microtox bioassay based on change in light emission by the luminescent bacteria Vibrio fischeri. Within a 5.0–8.0 pH range, EC50 values for As(V) were found to decrease as pH became basic, reflecting an increase in toxicity; whereas in the case of As(III), EC50 values were almost unchanged within a 6.0–8.0 pH range and lowered only at pH 9.0. HAsO42− and H2AsO3− were found to be the most toxic species. A statistical approach based on testing the null hypothesis of additive toxicity revealed an antagonistic effect between the arsenate chemical species. At low concentrations, As(V) was regularly found to be more toxic than As(III), independent of the pH value. Conversely, at high concentrations, the toxicity of both As(III) and As(V) was found to chiefly depend on pH, as a consequence of the strong influence of this parameter on the chemical speciation.

Alternative toxicological methods used in Russia to assess safety of food and non-food products have been reviewed. Along with traditional toxicological methods of monitoring various alternative toxicological study techniques are used to assess product safety. Those are methods using biological test-objects, so-called biological test methods, or in vitro methods which are allowed to be used from the legislative viewpoint. Alternative toxicological methods are based on risk degree assessment of the studied object by response of living organisms (test-objects) to adverse factor exposure. Information resulting from applied bio-testing methods represents combined toxic effect of all toxicants present in the given medium and their simultaneous presence. When assessing product safety by toxicological indices using alternative biological models, general toxic and irritating effects are to be studied and the test-objects are cattle semen, luminescent bacteria, chick egg chorioallantoic membrane, human and animal cell cultures and isolated organs. In vitro methods with cattle semen and luminescent bacteria playing the role of test-objects are also used to assess alcohol product toxicity, in particular spirits and vodkas. Thus, alternative study methods are widely known and commonly used in practice to prove safety of consumer goods and alcohol-containing foodstuffs.

Discharge of toxic industrial wastewaters into biological wastewater treatment plants may result in inhibition of activated sludge bacteria (ASB). In order to find an appropriate method of detoxification, the wastewater of a pesticide-processing plant in Vietnam was treated with three different methods (FeIII, powdered activated carbon (PAC), Fenton (FeII/H2O2)) analyzing the detoxification effect with the nitrification inhibition test (NIT), respiration inhibition test (RIT) and luminescent bacteria test (LBT). The heterotrophic ASB were much more resistant to the wastewater than the autotrophic nitrificants. The NIT turned out to be more suitable than the RIT since the NIT was less time-consuming and more reliable. In addition, the marine Aliivibrio fischeri were more sensitive than the nitrificants indicating that a lack of inhibition in the very practical and time-efficient LBT correlates with a lack of nitrification inhibition. With 95%, the Fenton method showed the highest efficiency regarding the chemical oxygen demand (COD) removal. Although similar COD removal (60–65%) was found for both the FeIII and the PAC method, the inhibitory effect of the wastewater was reduced much more strongly with PAC. Both the NIT and the LBT showed that the PAC and Fenton methods led to a similar reduction in the inhibitory effect.

After 3 weeks of starvation the bacterial light-organs of the bioluminescent shallow-water fishAnomalops katoptron cease to produce light. Because of a reduction of the number of symbionts in the cells of the light organ, it is concluded that the fish supplies its luminescent bacteria with nutrients out of its own metabolism. As a result of starving the fish, the luminescent bacteria decrease in number and finally cease to emit light.

The effect of temperature and salinity on numbers of luminescent bacteria present in waters of the Mystic (Conn.) River estuary was evaluated. Counts decreased with decreasing salinity; none were detected at freshwater stations. A population maximum of 35 per ml was noted at the highest salinity station (30±2‰). Highest counts were observed during winter and spring and lowest numbers occurred during summer and fall months. Isolates (111) were identified and compared with previously-described luminescent bacteria; i.e.,Beneckea (Vibrio) harveyi, Photobacterium (V.) fischeri, P. phosphoreum, andP. leiognathi. All species were isolated but distinct seasonal differences were noted.P. (V.) fischeri andB. (V.) harveyi represented 93% of the luminous population on an annual basis. Only the former was found during the period December through March (highest count 7 per ml) whileB. (V.) harveyi was the dominant species noted between May and October (maximum count 11 per ml).P. leiognathi andP. phosphoreum were found only during July and August as 7% of the total luminous population. All isolates grew at NaCl concentrations between 6 and 30‰; none grew below 6‰

WE have postulated previously that the catalytic decomposition by catalase of hydrogen peroxide to molecular oxygen and water is accompanied by changes in the valency of catalase iron1. This supposition is strongly supported by spectroscopic and manometric experiments carried out on azide-catalase. As additional evidence in support of this view, we brought forward the results of experiments carried out in Barcroft differential manometers, showing that under certain conditions even the activity of free catalase is inhibited when oxygen is completely removed from the surrounding medium and replaced by pure nitrogen. Our manometric experiments were repeated by Weiss and Weil-Malherbe2 who, using Warburg manometers, failed to obtain this inhibition. Johnson and van Schouvenburg3 also failed to confirm our results using luminescent bacteria as indicators of decomposition of hydrogen peroxide by catalase in complete absence of oxygen. However, we repeated our experiments from time to time, using different enzyme preparations, and invariably confirmed our previous results. The failure by other workers to obtain similar inhibition was explained by us4, 5 as being due probably either to some difficulty in complete elimination of oxygen from Warburg manometers or to some defects in their enzyme preparations.