Bromine in soils and peats

Summary Determinations were made by an iodometric method and by gas-liquid chromatography (g.l.c.) of inorganic bromide and total bromine in two soils of widely differing organic matter content, and in eight types of peat. The volumetric method is responsive to both bromide and iodide and gave a combined value. The g.l.c. method is halogen specific and gave individual values for bromide and iodide. Inorganic bromide represented only a small fraction (1.1% and 8%) of the total bromine in the soils, and was an even smaller fraction (0–1%) in the peats. The highly organic soil contained 141 μg total Br/g dry wt compared with 14 μg/g in the other soil. Total Br in the peats ranged from 11–116 μg/g. The organic soil contained an appreciable amount of total I (46 μg/g), while the total I content of the peats ranged from 3–18 μg/g. The possibility is considered that during the decomposition of peat added to soil, organic Br is released which might act as a potential source of inorganic bromide available to plants, so contributing to bromide residues in edible crops.     

The production of hydrogen sulphide in peats

The levels of sulphide ions in several peatlands have been shown to vary from low on the surface to values deeper in the peat in excess of 7.0 mg S/100 g fresh weight of peat. Highest levels of sulphide were recorded in early summer falling to close to zero in August and November. Rates of hydrogen sulphide production in peats are greatest between 10 and 15 cm from the surface and are associated with water table position. Reduced rates towards the surface are related to aeration and those below 15 cm attributed to higher sulphide levels causing autoinhibition or to the absence of suitable carbon sources.     

一株高耐氧反硝化细菌的筛选及其反硝化产物确定

利用浅层振荡培养和连续通气培养方法,获得一株高耐氧反硝化细菌H1.分别利用NO报告克隆nnrS-gfp和乙炔抑制-气相色谱测得菌株H1能够在反硝化条件下产生NO和N2O,不能产生N2,因此其反硝化途径为NO3-→NO2-→NO→N2O.在初始O2浓度为0%～21%范围内,该菌株能将98%以上的NO3-还原为气态氮化物.在150 mL的培养液中,连续以2 L/min的速率通气,H1依然能够反硝化,但是更高的通气速率则反硝化停止.16S rDNA序列分析表明,菌株H1与Ralstonia taiwanensis相似性达98%.     

The micromorphology of selected Irish milled peats

The movement of water in milled peat is of importance to the peat industry particularly in terms of rewetting. Considering the importance of structure with regard to water flow, micromorphology was used to obtain information regarding the nature of milled peat as a porous medium in a manner not available by other means. Peat was sampled from the undisturbed surface of two bogs (raised and fen origin) and from milled peat stockpiles. Thin sections were prepared to describe the nature of the two peat materials (milled and unmilled) in terms of the particle / pore properties and composition. Image analysis and point counting techniques were used to quantify results wherever possible. Although overall macro-porosity was similar for the two stockpiles, particle and pore size distributions varied considerably. Variations arose from the nature of the peat type and its interaction with milling operations with results suggesting that smaller pore sizes relate to a greater propensity to rewet. This revised version was published online in June 2006 with corrections to the Cover Date.     

好氧反硝化菌

<正>养殖水体氮素污染问题是目前困扰我国水产养殖业可持续发展的一大难题。生物脱氮技术被认为是目前最具发展前景的水体脱氮技术,其效果的优劣与所采用菌株的特性密切相关。传统反硝化细菌仅能在厌氧及低氧条件下发挥脱氮作用,与养殖水体的高溶氧环境矛盾,而好氧反硝化细菌则可在高溶氧环境中发挥脱氮作用,显著提高生物脱氮技术在养殖水体中的应用效果,实现养殖水体的绿色、零污染脱氮。因而,对好氧反硝化细菌开展高效选育方法的研究,找到可适应养殖水体水环境的微生物菌株具有重要的理论价值和经济价值。     

反硝化功能基因—— 检测反硝化菌种群结构的分子标记

反硝化菌种类繁多, 且分属多个分类学上的不同种属, 故不能利用常规的16S rRNA测序方法对其进行研究。利用编码反硝化酶的功能基因作为分子标记, 可以有效研究环境样品中反硝化菌的种群结构、数量以及活性等。本文重点介绍了主要的反硝化功能基因以及常用的扩增引物, 分析了反硝化功能基因与16S rRNA系统发育之间的关系, 比较了nirS和nirK基因菌的群落分布特征, 对目前反硝化功能基因的研究和应用现状进行了综述, 讨论了研究中发现的新问题, 期望为研究复杂微生物的生态特征提供参考。     

The biosynthesis of ethyl esters of lithocholic acid and isolithocholic acid by rat intestinal microflora

Recent reports concerning the tumor-promoting action of lithocholic acid in the colon and liver suggest that the metabolism of this major fecal bile acid may be important in carcinogenesis at various target sites. The metabolism of [¹⁴COOH]-lithocholic acid by rat intestinal microflora derived from standard laboratory chow-fed animals produced slightly more non-polar metabolites than those incubations which utilized flora from animals on a high lean-beef regimen. Purification of the crude bacterial extracts by Sephadex LH-20 chromatography and analysis of the radioactive peaks by glass fiber paper chromatography resulted in the identification of two neutral metabolites. Confirmation of their identity as ethyl lithocholate and ethyl isolithocholate was achieved by gas-liquid chromatography and combined gas-liquid chromatography-chemical ionization mass spectrometry. The formation of ethyl esters of lithocholic acid and isolithocholic acid by the intestinal microflora requires the presence of ethanol and anaerobic incubation conditions. These data support results obtained previously with single human fecal microorganisms. Since the formation of these derivatives in vitro occurs under anaerobic conditions only, it is possible that such derivatives may form physiologically in the colon. The carcinogenic potential of these derivatives is under investigation.     

Denitrifying degradation of dimethyl phthalate

Results of batch experiments on the denitrifying degradation of dimethyl phthalate (DMP) was most favorable at pH 7–9 and 30–35°C. DMP was first degraded to monomethyl phthalate (MMP), which was in turn degraded to phthalate before complete mineralization. There was no fatty acid residue in the mixed liquor throughout the experiments. The maximum specific degradation rates were 0.32 mM/(gVSS·h) for DMP, 0.19 mM/(gVSS·h) for MMP, and 0.14 mM/(gVSS·h) for phthalate. About 86% of available electron in DMP was utilized for denitrification; the remaining 14% was presumable conserved in the new biomass with an estimated yield of 0.17 mg/mg DMP. Based on 16S rDNA analysis, the denitrifying sludge was mainly composed of β-subdivision and α-subdivision of Proteobacteria (33 and 5 clones out of a total of 43 clones, respectively), plus some Acidobacteria. Using a primer set specifically designed to amplify the denitrification nirK gene, 10 operational taxonomy units (OTUs) were recovered from the clone library. They clustered into a group in the α-subdivision of Proteobacteria most closely related to denitrifier Bradyrhizobium japonicum USDA110 and several environmental clones.     

Isolation of Denitrifying Photosynthetic Bacteria

An alkaline proteinase produced by Bacillus sp. was purified and crystallyzed through isopropanol or ammonium sulfate precipitation, decolorization with DEAE-cellulose and gel filtration with Sephadex G-100. The optimum pH for caseinhydrolysis was 11.5 and the activity was completely inactivated after incubation with DFP. The specific activity on Hammersten casein was about 4,500 units/mg enzyme protein. The enzyme also hydrolyzed synthetic ester substrate such as Ac-Tyr-OEt, Ac-Phe-OEt or Bz-Met-OMe. The isoelectric point was pH 10.7, and the molecular weight was estimated to be about 17,500 by the sedimentation equilibrium method and 16,000 by gel filtration method. Some physicochemical properties and the amino acid composition of the enzyme were investigated, indicating that the enzyme is distinguishable from alkaline proteinase of Bacillus species so far reported.     

Denitrifying potential of methanogenic sludge

Summary A methanogenic sludge showed denitrifying activity for acetate, glucose and effluents from methanogenic treatments as substrates; denitrifiers were present in a relatively high number. When glucose was used as substrate dissimilatory reduction of nitrate to ammonium occurred. Methane production from acetate was inhibited by denitrification and resumed after nitrite and nitrous oxide depletion.     

Gastric acid reduction leads to an alteration in lower intestinal microflora

To clarify the alterations in lower intestinal microflora induced by gastric acid reduction, the dynamics of 12 major genera or groups of bacteria comprising the microflora in feces and colonic contents were examined by quantitative real-time PCR in proton pump inhibitor-treated rats and in asymptomatic human subjects with hypochlorhydria. In both rat and human experiments, most genera or groups of intestinal microflora (facultative and obligate anaerobes) proliferated by gastric acid reduction, and marked and significant increases in the Lactobacilli group and Veillonella, oropharyngeal bacteria, were observed. In rats, potent gastric acid inhibition led to a marked and significant increase of intestinal bacteria, including the Bacteroidesfragilis group, while Bifidobacterium, a beneficial bacterial species, remained at a constant level. These results strongly indicate that the gastric acid barrier not only controls the colonization and growth of oropharyngeal bacteria, but also regulates the population and composition of lower intestinal microflora.     

Unaltered metabolism of taurolithocholic acid with changes in composition of rat intestinal microflora

Changes in composition of both total aerobes and anaerobes of rat intestinal microflora do not appear to affect the metabolism of taurolithocholic acid.     

Influence of intestinal microflora on the amino acid composition of lamb feces]

6 conventional and 5 germfree male lambs were fed ad libitum a UHT sterilized cow milk. Body weight and food intake were recorded. Whole feces were collected for 5 consecutive days. Growth rate reached 259 g/d for the germfree. Daily fecal excretion of dry matter and nitrogenous compounds are not found different in the two groups of animals. The influence of intestinal microflora appears on the biochemical composition of the feces. As compared to the conventional fecal proteins from germfree lambs are very high in threonine and serine and low in lysine. Moreover the difference of amino acid composition between these two groups come not only from the histidine alanine and arginine composition of bacteries; it also involves the high levels of threonine serine cystine and tyrosine of the endogenous digestive proteins.     

Bromate Reduction by Denitrifying Bacteria

In the presence of bromide, ozonation as applied in water treatment results in the formation of bromate, an ion with carcinogenic properties. The reduction of bromate by mixed bacterial populations as well as pure cultures was studied under laboratory conditions. Bromate was reduced to bromide by a mixed bacterial population with and without a preceding nitrate reduction step in an anaerobically incubated medium with ethanol as the energy and carbon source at 20 and 25 deg C. The predominating bacteria isolated from the batches showing bromate reduction were identified as Pseudomonas spp. Strains of Pseudomonas fluorescens reduced BrO(inf3)(sup-) to Br(sup-) but at a much lower rate than the mixed bacterial population did. Nitrate is a preferred electron acceptor for the bromate-reducing bacteria. Bromate reduction did not occur in the presence of NO(inf3)(sup-), and the rate of bromate reduction was at least 100 times lower than the rate of nitrate reduction. Bromate was completely converted to Br(sup-), indicating that intermediates, e.g., BrO(inf2)(sup-), did not accumulate during bromate reduction.     

Species-specific FISH analysis of cecal microflora in rats administered with lactic acid bacteria

Summary We investigated the effects of lactic acid bacterial (LAB) cells in rats using fluorescence in situ hybridization (FISH) targeting 16S rRNA to identify the cecal microbial community. We designed a novel species-specific 16S rDNA probe to detect Lactobacillus rhamnosus (Lrham454). Subtractive technique using the LAC722 probe (Sakai et al. 2004 Journal of Bioscience and Bioengineering 98, 48) under different hybridization stringency (LAC722(L-H)) was applied to identify Lactococcus lactis. We also applied Lplan447 and LAC722(L) to detect Lactobacillus plantarum and a wide range of LAB (total LAB), respectively. We optimized the hybridization and washing conditions and then quantified L. rhamnosus, L. plantarum, and L. lactis cells in rat cecal contents. We monitored increases in individual bacterial populations and in total LAB caused by the administration of the corresponding LAB cells. Growth, food efficiency and internal disorders did not significantly differ among the rats administered with LABs. Rats administered with polydextrose (POL) developed diarrhea, which decreased the total numbers of cecal bacteria, whereas the simultaneous administration of POL and L. rhamnosus KY-3 eased this symptom, and recovered the numbers of total LAB and of L. rhamnosus.