Chemical constituents and antibacterial activity of the leaf essential oil of <Emphasis Type="Italic">Feronia limonia</Emphasis>

Bioleaching of uranium was carried out with Turamdih ore sample procured from Uranium Corporation of India Limited, Jaduguda. The bacterial strain that was used in the leaching experiments was isolated from the Jaduguda mine water sample. Efficiency of bioleaching was studied by varying parameters like pulp density and initial ferrous concentration as source of energy. It is observed that the efficiency of bioleaching was 49% at 10% pulp density (w/v) and initial pH 2.0. Addition of external has no effect on efficiency of bioleaching showing domination of direct leaching mechanism over indirect.     

Effect of microbial activity on buried cyanobacterial organic matter

The biomass from which hydrocarbons were formed and the organisms responsible for its production are usually deduced by the use of biochemical markers. In the present study, using a simulated sedimentary system, cyanobacterial organic matter was buried in sediments and exposed to sequential environmental changes ranging from microaerobic conditions at ambient temperature to strongly reducing conditions at a biologically extreme temperature and pressure. Significant changes occurred in the composition of hydrocarbons and fatty acids isolated from the biomass that masked the characteristic patterns exhibited by the original cyanobacterial material. The changes depended on the particular environmental conditions to which the organic matter was exposed. The results stress the need for caution in interpreting biochemical markers in terms of their source material in sediments.     

Interactions of three eco-types of Acidithiobacillus ferrooxidans with U(VI)

The interaction of uranium with cells of three recently described eco-types of Acidithiobacillus ferrooxidans recovered from uranium mining wastes was studied. The uranium sorption studies demonstrated that the strains from these types possess different capabilities to accumulate and tolerate uranium. The amount of uranium biosorbed by all A. ferrooxidans strains increased with considerable concentrations. We have found that the representatives of type II accumulate significantly higher amounts of uranium in comparison to the other A. ferrooxidans strains. The investigations of the tolerance to uranium showed that the types I and III are resistant to 8 and 9 mM of uranium respectively, whereas the type II does not tolerate more than 2 mM of uranium. The recovery of the accumulated uranium by desorption was investigated using various desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. Sodium carbonate was the most efficient desorbing agent, removing 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectively.     

微生物接种密度和矿物收集时间对生物沥浸中次生铁矿物形成的影响

在嗜酸性氧化亚铁硫杆菌Acidithiobacillus ferrooxidans作用下, 污泥生物沥浸体系中常会有次生铁矿物形成, 这些矿物对污泥脱水和重金属溶出有重要影响。在FeSO4-K2SO4-H2O生物成矾临界点模拟生物沥浸过程, 考察了Acidithiobacillus ferrooxidans菌接种密度和矿物收集时间对次生铁矿物的影响。结果表明, 微生物接种密度和矿物收集时间对生物沥浸过程中次生铁矿物的重量及其类型均有一定影响, 随矿物收集时间的推迟, 溶液中含有的一价阳离子(如K+等)可导致施氏矿物向黄铁矾发生转变, 并成为影响铁矿物类型的主导因素。     

Isolation of Arsenic Resistant and Arsenopyrite Oxidizing Acidithiobacillus Species from pH Neutral Colombian Mine Effluents

Abstract

Inactive mines provide a great source of bacterial diversity for studying acidophilic communities and their biotechnological applications, but prospecting of these anthropogenic environments in Colombia has been limited. Conventional microbiological methods were used to isolate acidophilic bacterial strains from effluents emanating from the Colombian gold mine ‘El Zancudo’ (Titiribí, Antioquia). Despite the drainage waters having circumneutral pH, all of the isolated strains were phylogenetically related to the extreme acidophile Acidithiobacillus genus. However, based upon 16S rRNA gene sequences the mesophilic sulfur-oxidizing indigenous strains could not be assigned to a species. Pure cultures were selected by screening in medium with soluble inorganic arsenic (III) and their mineral-oxidative activity was evaluated at 30?°C in Erlenmeyer flasks with arsenopyrite ore under rotary shaking conditions. The indigenous strains were able to catalyze arsenopyrite oxidation in a mixed culture with a pulp density of 10%, maintaining their growth in the presence of >80?mM leached arsenic. This research provides information regarding the isolation of arsenic resistant bacterial communities from neutral effluents from El Zancudo mine and the possibility of the isolated strains to be useful in the biooxidation pretreatment of refractory gold-bearing arsenopyrite ores and concentrates.     

pH variations during growth of Acidithiobacillus thiooxidans in buffered media designed for an assay to evaluate concrete biodeterioration

The pH of two buffered media having their initial pH ranging between 3.5 and 8.5 was monitored during growth of Acidithiobacillus thiooxidans. The first media was buffered with tricyclic phosphate whereas the second one contained phosphate ions and thus exhibited a stronger buffer capacity. Bacterial growth was not observed in any of the two media when the initial pH was higher than 5.5. On the other hand, for initial pH lower than 5.5, bacterial growth induced pH drops in both media. This drop was preceded by a lag phase during which the pH remained unchanged. However, in the medium buffered with phosphate ions, the lag periods were longer. As these media were developed for designing a bioleaching test to evaluate concrete biodeterioration caused by A. thiooxidans, the medium containing tricyclic phosphate appeared to be the most appropriate.     

A Novel Zeolite Coating for Protection of Concrete Sewers from Biological Sulfuric Acid Attack

Microbial growth inhibition and resistance to biological deterioration of concrete specimens coated with silver-loaded zeolite was evaluated by measuring the time course of bacterial growth, biological sulfur oxidation, and sulfate production using Acidithiobacillus thiooxidans as a corrosive agent. Live bacterial cells declined from an initial inoculum concentration of 1.1 × 10₄ cell ml_-1 to zero in 10 days, during which only 0.5–1% of the initial sulfur concentration of 10 g l_-1 was biologically oxidized, corresponding to sulfate production rates of 35–42 mg SO ₄ ^{2 ?} g ^{? 1} S ^{? 1} . Leaching coefficients of calcium and silicon in the specimens coated with silver-loaded zeolite of 1.6 × 10 ^{? 4} to 4.6 × 10 ^{? 2} cm ² d ^{? 1} respectively, were only 0.8% and 1% of the uncoated specimens.     

Sulfite Oxidation Catalyzed by aa 3-Type Cytochrome c Oxidase in Acidithiobacillus ferrooxidans

Sulfite is produced as a toxic intermediate during Acidithiobacillus ferrooxidans sulfur oxidation. A. ferrooxidans D3-2, which posseses the highest copper bioleaching activity, is more resistant to sulfite than other A. ferrooxidans strains, including ATCC 23270. When sulfite oxidase was purified homogeneously from strain D3-2, the oxidized and reduced forms of the purified sulfite oxidase absorption spectra corresponded to those of A. ferrooxidans aa ₃-type cytochrome c oxidase. The confirmed molecular weights of the α-subunit (52.5 kDa), the β-subunit (25 kDa), and the γ-subunit (20 kDa) of the purified sulfite oxidase and the N-terminal amino acid sequences of the γ-subunit of sulfite oxidase (AAKKG) corresponded to those of A. ferrooxidans ATCC 23270 cytochrome c oxidase. The sulfite oxidase activities of the iron- and sulfur-grown A. ferrooxidans D3-2 were much higher than those cytochrome c oxidases purified from A. ferrooxidans strains ATCC 23270, MON-1 and AP19-3. The activities of sulfite oxidase purified from iron- and sulfur-grown strain D3-2 were completely inhibited by an antibody raised against a purified A. ferrooxidans MON-1 aa ₃-type cytochrome c oxidase. This is the first report to indicate that aa ₃-type cytochrome c oxidase catalyzed sulfite oxidation in A. ferrooxidans.