Turbidity measurements of bacterial cultures in some available commercial instruments.
About: This article is published in Analytical Biochemistry.The article was published on 1970-11-01. It has received 213 citations till now.
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TL;DR: Results are consistent with the proposal that the peroxide radical is an important agent of the toxicity of oxygen and that superoxide dismutase may be a component of the systems which have been evolved to deal with this potential toxicity.
Abstract: Oxygen induces superoxide dismutase in Streptococcus faecalis and in Escherichia coli B. S. faecalis grown under 20 atm of O2 had 16 times more of this enzyme than did anaerobically grown cells. In the case of E. coli, changing the conditions of growth from anaerobic to 5 atm of O2 caused a 25-fold increase in the level of superoxide dismutase. Induction of this enzyme was a response to O2 rather than to pressure, since 20 atm of N2 was without effect. Induction of superoxide dismutase was a rapid process, and half of the maximal level was reached within 90 min after N2-grown cells of S. faecalis were exposed to 20 atm of O2 at 37 C. S. faecalis did not contain perceptible levels of catalase under any of the growth conditions investigated by Stanier, Doudoroff, and Adelberg (23), and the concentration of catalase in E. coli was not affected by the presence of O2 during growth. S. faecalis, which had been grown under 100% O2 and which therefore contained an elevated level of superoxide dismutase, was more resistant of 46 atm of O2 than were cells which had been grown under N2. E. coli grown under N2 contained as much superoxide dismutase as did S. faecalis grown under 1 atm of O2. The E. coli which had been grown under N2 was as resistant to the deleterious effects of 50 atm of O2 as was S. faecalis which had been grown under 1 atm of O2. These results are consistent with the proposal that the peroxide radical is an important agent of the toxicity of oxygen and that superoxide dismutase may be a component of the systems which have been evolved to deal with this potential toxicity.
295 citations
TL;DR: Observations lend support to the hypothesis that O(2) (-) is an important agent of oxygen toxicity and that superoxide dismutase functions to blunt the threat posed by this reactive radical.
Abstract: Oxygen caused an increase in the amount of superoxide dismutase in Escherichia coli B but not in Bacillus subtilis. E. coli B cells, induced by growth under 100% O2, were much more resistant to the lethal effects of 20 atm of O2 than were cells which contained the low uninduced level of this enzyme. In contrast, B. subtilis, which could not respond to O2 by increasing its content of superoxide dismutase, remained equally sensitive to hyperbaric O2 whether grown under 100% O2 or areobically. The catalase in these organisms exhibited a reciprocal response to oxygen. Thus, the catalase of E. coli B was not induced by O2, whereas that of B. subtilis was so induced. These results are consistent with the view that superoxide dismutase is an important component of the defenses of these organisms against the toxicity of oxygen, whereas their catalases are of secondary importance in this respect. The ability of streptonigrin to generate O2−, by a cycle of reduction followed by spontaneous reoxidation, has been verified in vitro. It is further observed that E. coli B which contain the high induced level of superoxide dismutase were more resistant to the lethality of this antibiotic, in the presence of oxygen, than were E. coli B which contained the low uninduced level of this enzyme. This difference between induced and uninduced cells was eliminated by the removal of O2. These results are consistent with the proposal that the enhanced lethality of streptonigrin under aerobic conditions may relate to its in vivo generation of O2− by a cycle of reduction and spontaneous reoxidation. In toto, these observations lend support to the hypothesis that O2− is an important agent of oxygen toxicity and that superoxide dismutase functions to blunt the threat posed by this reactive radical.
266 citations
TL;DR: In this paper, the authors examined the potential for biodegradation of s-triazines as an example and with biological treatment of wastewater containing s-Triazines as the aim, but the system was not practicable because the specific enzymes were too low, because of inhibition by salt in the wastewater and because expensive carbon sources were necessary.
Abstract: Biodegradation of xenobiotic compounds is examined with s-triazines as an example and with biological treatment of wastewater containing s-triazines as an aim. s-Triazines have been termed recalcitrant, but examination of the literature indicates that a potential for biodegradation exists. Nitrogen-limited enrichment cultures yield organisms able to degrade by-products of the industrial synthesis of s-triazine herbicides as sources of nitrogen. The choice of inoculum for these enrichments is important and often allows for successful enrichment after simple batch culture, but organisms containing several degradative reactions could be obtained only after selection in extended culture. Routine, specific determinations of all s-triazines (by HPLC) were essential throughout the work. Molar growth yields show complete mass balances for the utilization of s-triazines. Kinetic experiments indicate that specific degradation rates of s-triazines in growing cells are about 0.4 mkat/kg of protein. Characterised biochemical pathways consist of a series of hydrolytic cleavages of chloro-, amino- and alkylamino-groups from the s-triazine ring. Pathways converge to cyanuric acid, which is subject to hydrolytic ring cleavage to CO2 and NH4+ via hydrolysis of biuret and urea. Our cultures degraded all significant s-triazines in real wastewater. But the system was not practicable because the specific activities of some enzymes were too low, because of inhibition by salt in the wastewater and because expensive carbon sources were necessary. Improved planning for enrichment cultures is seen to be necessary and this depends on adequate knowledge of the chemistry of the wastes.
243 citations
Cites background from "Turbidity measurements of bacterial..."
...Growth, for example, is often measured as light scattering, and this can be an accurate measure of growth under defined conditions with proper calibration [41] [42]....
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TL;DR: Data indicate that, in both prokaryotes and in eukaryotes, superoxide dismutase is an important component of the defenses against oxygen toxicity.
Abstract: Saccharomyces cerevisiae var. ellipsoideus contained 6.5 times more superoxide dismutase and 2.3 times more catalase when grown under 100% O2 than when grown anaerobically. Growth under oxygen caused equal increases in both the cyanide-sensitive and the cyanide-insensitive superoxide dismutases of this organism. Experience with other eukaryotes has shown that cyanide sensitivity is a property of the cupro-zinc superoxide dismutase of the cytosol, whereas cyanide insensitivity is a property of the corresponding mangani-enzyme found in mitochondria. Cu2+, which has been shown to increase the radioresistance of yeast, also caused an increase of both of the superoxide dismutases of S. cerevisiae. Yeast which had been grown under 1 atm of O2 were more resistant toward the lethal effects of 20 atm of O2 than were yeast which had been grown in the absence of O2. Escherichia coli K-12 his− responded to growth under 1 atm of O2 by increasing its content of catalase and of peroxidase, but not of superoxide dismutase. This contrasts with E. coli B, which was previously shown to respond to O2 by a striking increase in superoxide dismutase. E. coli K-12 his− did not gain resistance toward 20 atm of O2 because of having been grown under 1 atm of O2. Once again, this contrasts with the behavior of E. coli B. These data indicate that, in both prokaryotes and in eukaryotes, superoxide dismutase is an important component of the defenses against oxygen toxicity.
169 citations
TL;DR: This paper presents the first study aimed at determining the primary antibacterial mode-of-action of the MXene, a novel 2D nanomaterial that has been reported to have excellent antibacterial activity against both Gram-negative and Gram-positive bacteria.
Abstract: Antibacterial properties of two-dimensional (2D) nanomaterials are of great interest in fields such as environmental engineering, biomedical engineering, and medicine. Ti3C2Tx MXene, a novel 2D nan...
165 citations
References
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TL;DR: It is found that for osmotic swelling of spheroplasts or mitrochondria, the absorbancy varies nearly inversely with the volume, and for variations in size at constant concentration, the absorption varies directly as the four-thirds power of the volume of the particle.
242 citations
107 citations
TL;DR: For suspension of randomly oriented, asymmetric particles of slightly irregular shape, reasonably accurate estimates of the light scattering can be computed from simple Rayleigh-Gans theory, even when applied to large objects such as mammalian mitochondria or the most-studied bacteria, Escherichia coli.
103 citations
TL;DR: It is shown that the relationship between light scattering and red-cell concentration is parabolic and that the absorption of light within the erythrocyte is the same as in a haemoglobin solution.
Abstract: Light transmission by thin films of nonhaemolysed blood is affected by the multiple scattering that occurs in undiluted blood. Previous studies did not permit investigation in terms of a light-scattering theory. The present study was made with an integrating-sphere spectrophotometer. Application of Twersky's theory for the multiple scattering of waves permitted separation of the effects of absorption and scattering on the light transmittance of nonhaemolysed blood. It is shown that the relationship between light scattering and red-cell concentration is parabolic and that the absorption of light within the erythrocyte is the same as in a haemoglobin solution.
97 citations
TL;DR: Experimental measurements show that the Rayleigh-Gans approximation for calculating the intensity of scattered light at angles up to 30° applies surprisingly well to particles as large as bacteria, and it is proposed that low angle light scattering can be useful in estimating the average volume of the bacterial cells in populations.
70 citations