Toxicity of paraquat to microorganisms

The biochemical response of the microorganisms Lipomyces starkeyi (Lod & Rij), Escherichia coli K-12 W3110, Bacillus subtilis 168 (Marburg) and Pseudomonas sp. strain TTO1 to the presence of growth-inhibitory concentrations of paraquat was studied. Paraquat was added to each culture at a concentration previously determined to reduce the culture growth rate by up to 50%. The changes in activity of a number of enzymes previously shown to be associated with the defense of the mammalian system against the action of paraquat were studied. While the response of E. coli was in agreement with that found in other studies of this microorganism and supports a commonly accepted mechanism for paraquat toxicity, the results obtained with L. starkeyi, B. subtilis, and Pseudomonas sp. strain TTO1 suggest that other mechanisms exist for protection against the toxicity of paraquat.     

Use of heterotrophic microorganisms in mineral biotechnology

A process for biological removal of iron from quartz sands, kaolins and clays was developed in which these industrial minerals were leached at 90°C with lixiviant produced as a result of the cultivation of acid-producing heterotrophic microorganisms, mainly strains of Aspergillus niger, at 30°C in a nutrient medium containing molasses as a source of carbon and energy. The lixiviant, i.e. the fermentation fluid, contained oxalic and citric acids as main components and after the cultivation was acidified to a pH of 0.5 by means of hydrochloric acid. The leaching was carried out in mechanically stirred acid-resistant vats for a period of from 1 to 5 hours. The iron content of some sands treated by this method was lowered from 0.035–0.088 to below 0.012% Fe₂O₃ making them suitable for the preparation of high quality glass. The iron content of different kaolins was lowered from 0.65–1.49 to 0.44–0.75% Fe₂O₃ and as a result of this their whiteness was increased from 55–87 to 86–92%. The iron content of a clay was lowered from 6.25 to 1.85% Fe₂O₃ and this increased the fireproofness of the clay from 1 670 to 1 750°C. Similar process was used for leaching of aluminium from aluminosilicates, mainly clays and kaolins. However, after the cultivation the fermentation fluid was acidified either by means of sulfuric or hydrochloric acid or by means of different mixtures of inorganic acids. For enhancing aluminium solubilization the aluminosilicates were heated before leaching at 600–650°C for 1–2 hours. Over 90% of the aluminium present in different clays and kaolins was leached within 3–6 hours in this way. “Silicate” bacteria related to the species Bacillus circulans and B. mucilaginosus were used to leach silicon from low-grade bauxite ores containing aluminosilicates as impurities. The bacterial action was connected with the formation of mucilaginous capsules consisting of expolysaccharides. The solid residues after leaching were characterized by higher values of alumina content and were suitable for processing by means of the BAYER process for recovering aluminium. Heterotrophic bacteria were used to leach manganese from oxide ores using different organic compounds as reducing agents.     

Toxicity of paraquat to microorganisms.

The biochemical response of the microorganisms Lipomyces starkeyi (Lod & Rij), Escherichia coli K-12 W3110, Bacillus subtilis 168 (Marburg) and Pseudomonas sp. strain TTO1 to the presence of growth-inhibitory concentrations of paraquat was studied. Paraquat was added to each culture at a concentration previously determined to reduce the culture growth rate by up to 50%. The changes in activity of a number of enzymes previously shown to be associated with the defense of the mammalian system against the action of paraquat were studied. While the response of E. coli was in agreement with that found in other studies of this microorganism and supports a commonly accepted mechanism for paraquat toxicity, the results obtained with L. starkeyi, B. subtilis, and Pseudomonas sp. strain TTO1 suggest that other mechanisms exist for protection against the toxicity of paraquat.     

Abundance and biomass of heterotrophic microorganisms in Lake Tanganyika

1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 10⁶ cells mL^?1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m^?2 and phytoplankton biomass was 3.75 g C m^?2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m^?2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m^?2). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m^?2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion.     

异养微生物在金属生物淋滤技术中的应用

生物淋滤技术主要应用于低品位矿石金属选矿、煤气脱硫、废弃物中金属回收和污染介质中金属离子毒性的去除等方面。作为生物淋滤技术中的主体微生物之一,异养微生物可通过其产生的酸性代谢物还原、酸化及络合,提取或者溶解非硫化矿、固体废弃物、污水污泥及土壤中的金属,有助于解决目前的资源短缺问题,还可对污染环境治理提供技术支持,具有重要的理论意义和实践价值。应用于异养微生物淋滤技术中的常见微生物包括细菌(以假单胞菌为主)和真菌(以曲霉菌和青霉菌应用最为广泛)。淋滤过程涉及酸解、络合、还原及碱化等。目前,异养微生物淋滤技术主要应用于生物冶金、固体废弃物处理、污水处理和污染土壤修复等。本文分析了异养微生物金属淋滤过程中的问题,并提出了未来研究的发展方向。     

Ultra-sonication application in biodiesel production from heterotrophic oleaginous microorganisms

Utilization of microbial oil for biodiesel production has gained growing interest due to the increase in prices and the shortage of the oils and fats traditionally used in biodiesel production. However, it is still in the laboratory study stage due to the high cost of production. Employing organic wastes as raw materials to grow heterotrophic oleaginous microorganisms for further lipid production to produce biodiesel has been predicted to be a promising method for reducing costs. However, there are many obstacles including the low biodegradability of organic wastes, low lipid accumulation capacity of heterotrophic oleaginous microorganisms while using organic wastes, a great dependence on a high-energy consumption approach for biomass harvesting, utilization of toxic organic solvents for lipid extraction, and large amount of methanol required in trans-esterification and in-situ trans-esterifications. Ultra-sonication as a green technology has been extensively utilized to enhance bio-product production from organic wastes. In this article, ultra-sonication applications in biodiesel production steps with heterotrophic oleaginous microorganisms have been reviewed, and its impact, potential, and limitations on the process have been discussed.     

Toxicity of flotation reagents to moderately thermophilic bioleaching microorganisms

The toxicity of 15 flotation reagents (including xanthates, carbamates, thiophosphates, a mercaptobenzthiazole and a frothing reagent) used for concentrating sulfide minerals to five species of mineral-oxidising, moderately thermophilic and acidophilic microorganisms was assessed. The acidophiles tested included four bacteria (a Leptospirillum isolate, Acidimicrobium ferrooxidans, Acidithiobacillus caldus and a Sulfobacillusisolate) and one archaeon (a Ferroplasma isolate). There was wide variation both in terms of the relative toxicities of the different flotation reagents and the sensitivities of the microorganisms tested. In general, the dithiophosphates and the mercaptobenzothiol were the most toxic, while the Leptospirillum and Ferroplasma isolates were the most sensitive of the acidophilic microorganisms. The significance of these findings, in view of the expanding application of ore concentrates bioprocessing, is discussed.     

Increase and limits of growth yields for heterotrophic microorganisms

Substrates for heterotrophic growth of microorganisms are more or less energy-limited. In order to improve the growth yields phenotypic and genetic measures come into consideration. By means of the auxiliary substrate concept the carbon metabolism determined carbon conversion efficiency of about 75% for C₂ compounds (i.e. non-glycolytic, gluconeogenetic substrates) and about 85%, respectively, for C₃ or glycolytic substrates can be attained experimentally. With methylotrophic microorganisms the growth yield might approach to this limit if the methanol oxidizing methanol dehydrogenase (bacteria) and methanol oxidase (yeasts) are replaced by an NAD⁺-linked dehydrogenase. Due to an increase in the overall P/O quotient up to the maximum this limit cannot be reached.     

Application of denitrifying microorganisms in waste water treatment

Summary A continuous fixed-bed denitrification system operating with high capacity and 100% efficiency has been developed for laboratory scale experiments. The data required for stable operation were obtained by determination of the kinetic constants of the system.     

An improved method for collecting heterotrophic microorganisms living on pebbles in streams

In microbiological studies in streams, pebble samples have until now been taken out of the water following the conventional method. However, this allows the loss of microorganisms as a result of the removal of overlying water. In the present study, to minimize the loss of microorganisms, we have developed a new sampling method, called the submerged method, for collecting microorganisms living on pebbles in streams. The abundance of microorganisms on natural pebbles and artificial clay tiles, both of which had biofilms developing on their surfaces, was measured using both the conventional and submerged methods and the results from the two methods were compared. The cell densities of bacteria (0.10–14.00 × 10⁸ cells cm^–2), heterotrophic nanoflagellates (0.36–50.30 × 10⁴ cells cm^–2), and ciliates (0.071–88.27 × 10² cells cm^–2) measured by the submerged method tended to be higher than those obtained by the conventional method, although there were only a few cases in which a significant difference existed between microbial abundances determined by the two methods. Also supported by microscopic observation, these results suggest the presence of planktonic and/or weakly attached microorganisms on substrate materials in streams. Significant correlations between the concentration of chlorophyll a and the cell densities of heterotrophic microorganisms and significant correlations among heterotrophic microorganisms suggest the presence of active microbial food webs in streams.     

Occurrence of collagen-degrading microorganisms in associations of mesophilic heterotrophic bacteria from various soils

A total of 437 bacterial cultures was isolated from various soils and sewage water that were tested for the ability to decompose reconstituted collagen. This activity was found in 6.6% of the cultures isolated from sewage water, 15% of the cultures from organic horizons of the spruce growth soil, 30% of the cultures from the meadow soil, 29% of the cultures from the vegetable field soil and in 37% of those isolated from garden soil. The capability to produce collagenolytic enzymes does not appear to be rare among soil bacteria.     

14C-most-probable-number method for enumeration of active heterotrophic microorganisms in natural waters.

A most-probable-number method using 14C-labeled substrates is described for the enumeration of aquatic populations of heterotrophic microorganisms. Natural populations of microorganisms are inoculated into dilution replicates prepared from the natural water from which the organisms originated. The natural water is supplemented with a 14C-labeled compound added so as to approximate a true environmental concentration. 14CO2 evolved by individual replicates is trapped in NaOH and counted by liquid scintillation techniques for use in scoring replicates as positive or negative. Positives (14CO2 evolution) are easily distinguished from negatives (no 14CO2 evolution). The results from a variety of environments using the 14CO2 procedure agreed well with previously described methods, in most instances. The 14C-most-probable-number method described here reduces handling procedures over previously described most-probable-number procedures using 14C-labeled substrates. It also appears to have advantages over other enumeration methods in its attempt to approximate natural conditions more closely.     

14C-most-probable-number method for enumeration of active heterotrophic microorganisms in natural waters.

A most-probable-number method using 14C-labeled substrates is described for the enumeration of aquatic populations of heterotrophic microorganisms. Natural populations of microorganisms are inoculated into dilution replicates prepared from the natural water from which the organisms originated. The natural water is supplemented with a 14C-labeled compound added so as to approximate a true environmental concentration. 14CO2 evolved by individual replicates is trapped in NaOH and counted by liquid scintillation techniques for use in scoring replicates as positive or negative. Positives (14CO2 evolution) are easily distinguished from negatives (no 14CO2 evolution). The results from a variety of environments using the 14CO2 procedure agreed well with previously described methods, in most instances. The 14C-most-probable-number method described here reduces handling procedures over previously described most-probable-number procedures using 14C-labeled substrates. It also appears to have advantages over other enumeration methods in its attempt to approximate natural conditions more closely.     

异养微生物固定CO2的合成生物学研究进展

人类活动造成大气二氧化碳（CO₂）浓度不断升高,使当今世界面临着气候变化的重大危机。微生物CO₂固定为实现地球“碳中和”提供了一条有前景的绿色发展路线。与自养微生物相比,异养微生物具有更快的生长速度和更先进的遗传工具,但是其固定CO₂的能力还很有限。近年来,基于合成生物学技术强化异养微生物CO₂固定受到诸多关注,主要包括优化能量供给、改造羧化途径以及基于异养微生物间接固定CO₂。本综述将围绕上述3个方面重点讨论异养微生物CO₂固定的研究进展,为将来更好地利用微生物CO₂固定技术实现“碳达峰、碳中和”提供参考。     

代谢工程改造异养微生物固定CO2研究进展

环境保护和能源供应是人类关心的两大问题。能源消耗释放出的温室气体对环境造成了严重影响。利用CO_2固定途径可将CO_2转化成燃料或化学品。天然固碳生物通常存在生长缓慢、固碳效率低等问题。通过在模式微生物中增强或重构CO_2固定途径,实现CO_2的再循环,可提高燃料或化学品的产量,减少温室气体排放。文中详细介绍了通过代谢工程手段改造CO_2固定途径改善化学品生产以及糖合成,阐述了相关代谢途径及其中的关键酶在CO_2固定中的作用,介绍了电生化合成系统的应用,显示出CO_2固定的巨大潜力,并展望了未来CO_2固定的研究方向。     

Airborne microorganisms in a municipal solid waste recovery system

The types of bacteria and fungi present in the air of a municipal solid waste recovery system have been characterized and the population densities estimated. Conventional methods were successful in enumerating coagulase-positive staphylococci, Klebsiella spp., gram-negative bacteria, fungi, and common indicator organisms. Selective and enrichment media, however, did not yield Salmonella isolates. Salmonella and Shigella were recovered at a frequency of 3% or less on trypticase soy agar. A broad spectrum of bacteria and fungi were isolated. No evidence has been found that indicates that these organisms have produced adverse health effects.