Single recessive mutations of the methylotrophic yeast Pichia methanolica acs1, acs2, acs3 and icl1 affecting acetyl-CoA synthetase and isocitrate lyase, and growth on ethanol as sole carbon and energy source, caused a defect in autophagic peroxisome degradation during exposure of methanol-grown cells to ethanol. As a control, a mutation in mdd1, which resulted in a defect of the 'malic' enzyme and also prevented ethanol utilization, did not prevent peroxisome degradation. Peroxisome degradation in glucose medium was unimpaired in all strains tested. Addition of ethanol to methanol-grown cells of acs1, acs2, acs3 and icl1 mutants led to an increase in average vacuole size. Thickening of peroxisomal membranes and tight contacts between groups of peroxisomes and vacuoles were rarely observed. These processes proceeded much more slowly than in wild-type or mdd1 mutant cells incubated under similar conditions. No peroxisomal remnants were observed inside vacuoles in the cells of acs1, acs2, acs3 and icl1 mutants after prolonged cultivation in ethanol medium. We hypothesize that the acs and icl mutants are defective in synthesis of the true effector-presumably glyoxylate-of peroxisome degradation in ethanol medium. Lack of the effector suspends peroxisome degradation at an early stage, namely signal transduction or peroxisome/vacuole recognition. Finally, these defects in peroxisome degradation resulted in mutant cells retaining high levels of alcohol oxidase which further led to increased levels of acetaldehyde accumulation upon incubation of mutant cells with ethanol.
New strains of sulfate-reducing bacteria were obtained from human intestine. These bacteria are vibrio-like (strains SRB Vib-1, SRB Vib-2, SRB Vib-3) and short rod-like (strains SRB Rod-4 and SRB Rod-5) forms. Growth of these strains of bacteria, usa ge of sulfates by bacteria and their production of hydrogen sulfide were studied. The strains of sulfate-reducing bacteria SRB Vib-1, SRB Vib-2, SRB Vib-3 more intensively accumulate biomass compared with strains SRB Rod-4 і SRB Rod-5. The SRB Vib-1 and SRB Vib-2 strains grow most intensively. Accumulation of bacterial biomass (3.8 g/l) is the highest on the third day of cultivation, and after that a stationary growth phase began. The SRB Vib-3 strain of bacteria accumulates 2.89 gram per liter of biomass on the third day of bacteria cultivation. Maximal biomass of SRB Rod-4 and SRB Rod-5 bacteria strains ranged from 2.59 to 3.25 gram per liter on the eighth day of cultivation. The obtained sulfate-reducing bacteria intensively use sulfate ions and produce hydrogen sulfide. The SRB Vib-1, SRB Vib-2, SRB Vib-3 strains produce from 2.99 mM to 3.12 mM of hydrogen sulfide. The rod-shaped strains of sulfate-reducing bacteria use sulfate ions and produce hydrogen sulfide less intensively in the presence of sulfates.
The toxicity of metal ions to microorganisms, in particular at high concentrations, is one of the main impediments to their usage in remediation technologies. The purpose of this work is to analyze the possibility of usage by bacteria of the Desulfuromonas genus, isolated by us from Yavorivske Lake, of ferrum (ІІІ) and manganese (IV) ions at concentrations in the medium of 1,74–10,41 mM as electron acceptors of anaerobic respiration to assesss resistance of sulphur reducing bacteria strains to heavy metal compounds. Cells of Desulfuromonas acetoxidans ІМV V-7384, Desulfuromonas sp. Yavor-5 and Desulfuromonas sp. Yavor-7 were cultivated for 10 days at 30 °C under anaerobic conditions in Kravtsov-Sorokin’s medium without sulphate ions, sulphur, with cysteine as the sulphur source (0.2 g/l) and sodium lactate or citrate as the electron donor (17.86 g/l), in which were added sterile 1 M solutions of C6H5O7Fe and C4H4O4 (control) and also weights of MnO2 to their terminal concentrations 1.74, 3.47, 5.21, 6.94, 10.41 mM. Biomass was determined by the turbidimetric method. In the culture liquid the presence of Fe3+ and Mn4+ were qualitatively determined, and the content of Fe2+ in reaction with о-phenanthroline was determined quantitatively. It was established that sulphur reducing bacteria used with different intensity ferrum (ІІІ) and manganese (IV) ions as electron acceptors during the process of anaerobic respiration at concentrations of 1.74–10.41 mM C6H5O7Fe and MnO2 in the medium, which demonstrated the important role of the investigated microorganisms in reductive detoxication of natural and technogenic media from oxidized forms of transitional heavy metals. An insignificant difference in biomass accumulation during usage of 5.21–10.41 mM ferrum (ІІІ) ions and fumarate is caused by toxicity of the metal ions to cells since the high redox potential of the Fe(III)/Fe(ІІ) pair with increase in concentrations of electron acceptors in the medium did not lead to increase in the biomass accumulation level. The greatest biomass of the bacteria accumulated on the 8–10th days in the medium with the lowest concentration of C6H5O7Fe – 1.74 mM (up to 2.77 g/l), and the lowest biomass – with highest concentration – 10.41 mM (up to 2.41 g/l). After 10 days of cultivation the bacteria of all strains had fully used the ferrum (ІІІ) ions present in the medium. A biomass yield almost twice as low was revealed after manganese (IV) oxide was used by bacteria compared with its use of ferrum (ІІІ) citrate and fumarate at all studied concentrations of electron acceptors in the medium. The highest biomass of bacteria accumulated in the medium with the lowest MnO2 content – 1.74 mM (up to 1.35 g/l), and the lowest biomass in the medium with the highest content – 10.41 mM (up to 1.15 g/l). After 10 days of cultivation bacteria of all strains had not fully restored the manganese (IV) ions present in the medium. The greatest biomass compared with other strains after growth in medium with different C6H5O7Fe and MnO2 contents was accumulated by the strain Desulfuromonas sp. Yavor-7. Since sulphur reducing bacteria strains proved to be resistant to Fe3+ and Mn4+ high concentrations (up to10.41 mM) they can be successfully used in technologies of environmenal remediation from sulphur and heavy metal compounds.
Moroz, O. M., Hnatush, S. O., Tarabas, O. V., Bohoslavets, C. I., Yavorska, G. V., & Borsukevych, B. M. (2018). Sulfidogenic activity of sulfate and sulfur reducing bacteria under the influence of metal compounds. Biosystems Diversity, 26(1), 3-10.Due to their high content in natural environments, heavy metals exhibit toxic effects on living organisms, which leads to a decrease in the biological diversity and productivity of ecosystems. In niches with low oxidation reducing potential, sulfate and sulfur reducing bacteria carry out the reducing transformation of oxidized sulfur compounds with the formation of significant amounts of hydrogen sulfide. H 2 S produced by bacteria interacts with metal ions, precipitating them in the form of sulfides. The aim of this work was to investigate the influence of lead, cuprum (II), iron (II) and manganese (II) salts on the production of hydrogen sulfide by bacteria of the Desulfovibrio and Desulfuromonas genera, isolated from Yavorivske Lake, and to evaluate the efficiency of their use for purifying media, enriched with organic compounds, from hydrogen sulfide and heavy metals. The content of heavy metal ions in the water of Yavorivske Lake was determined by the spectrophotometric method. The bacteria were grown for 10 days at 30 °C in the Kravtsov-Sorokin medium under anaerobic conditions. To study the influence of metal ions on bacteria growth and their H 2 S production, cells were incubated with metal salts (0.5-4.0 mM), washed and grown in media with SO 4 2or S 0 . To determine the level of metal ions binding by H 2 S, produced by bacteria, cells were grown in media with metal compounds (0.5-4.0 mM), SO 4 2or S 0 . Biomass was determined by turbidimetric method. In the cultural liquid the content of H 2 S was determined quantitatively by spectrophotometric method, and qualitatively by the presence of metal cations. The content of metal sulfides in the growth medium was determined by weight method. Sulfate and sulfur-reducing bacteria were resistant to 2.0 mM Pb(NO 3 ) 2 , 2.5 mM CuCl 2 , 2.5 mM FeCl 2 × 4H 2 O and 2.0 mM MnCl 2 × 4H 2 O, therefore they are promising for the development of biotechnologies for the purification of water resources contaminated by sulfur and metal compounds. When present in a medium with sulfates or sulfur of 1.0-1.5 mM lead, cuprum (II), iron (II) or manganese (II) ions, they almost completely bind with the H 2 S produced by bacteria in the form of insoluble sulfides, which confirms the negative results of qualitative reactions to their presence in the cultural liquid.
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