Antibacterial efficacy of Withania somnifera (ashwagandha) an indigenous medicinal plant against experimental murine salmonellosis

In the present study, we evaluated the antibacterial activity of ashwagandha [Withania somnifera L. Dunal (Solanaceae; root and leaves)], an Indian traditional medicinal plant against pathogenic bacteria. Both aqueous as well as alcoholic extracts of the plant (root as well as leaves) were found to possess strong antibacterial activity against a range of bacteria, as revealed by in vitro Agar Well Diffusion Method. The methanolic extract was further subfractionated using various solvents and the butanolic sub-fraction was found to possess maximum inhibitory activity against a spectrum of bacteria including Salmonella typhimurium. Moreover, in contrast to the synthetic antibiotic (viz. chloramphenicol), these extracts did not induce lysis on incubation with human erythrocytes, advocating their safety to the living cells. Finally, the antibacterial efficacy of the extracts isolated from plant (both root and leaves) was determined against experimental salmonellosis in Balb/C mice. Oral administration of the aqueous extracts successfully obliterated salmonella infection in Balb/C mice as revealed by increased survival rate as well as less bacterial load in various vital organs of the treated animals.     

In vitro evaluation of Datura innoxia (thorn-apple) for potential antibacterial activity

Various parts of Datura innoxia were examined for potential antibacterial activity by preparing their crude aqueous and organic extracts against Gram-negative bacteria (Escherichia coli and Salmonella typhi) and Gram-positive bacteria (Bacillus cereus, Bacillus subtilis and Staphylococcus aureus). The results of agar well diffusion assay indicated that the pattern of inhibition depends largely upon the plant part, solvent used for extraction and the organism tested. Extracts prepared from leaves were shown to have better efficacy than stem and root extracts. Organic extracts provided potent antibacterial activity as compared to aqueous extracts. Among all the extracts, methanolic extract was found most active against almost all the bacterial species tested. Gram-positive bacteria were found most sensitive as compared to Gram-negative bacteria. Staphylococcus aureus was signifi cantly inhibited by almost all the extracts even at very low MIC followed by other Gram-positives. For Escherichia coli (a Gram-negative bacterium), the end point was not reached for ethyl acetate extract while it was very high for other extracts. The study promises an interesting future for designing a potentially active antibacterial agent from Datura innoxia.     

Effect of 2,4,6-trinitrotoluene on soil bacterial communities

To gain insight into the impact of 2,4,6-trinitrotoluene (TNT) on soil microbial communities, we characterized the bacterial community of several TNT-contaminated soils from two sites with different histories of contamination and concentrations of TNT. The amount of extracted DNA, the total cell counts and the number of CFU were lower in the TNT-contaminated soils. Analysis of soil bacterial diversity by DGGE showed a predominance of Pseudomonadaceae and Xanthomonadaceae in the TNT-contaminated soils, as well as the presence of Caulobacteraceae. CFU from TNT-contaminated soils were identified as Pseudomonadaceae, and, to a lesser extent, Caulobacteraceae. Finally, a pristine soil was spiked with different concentrations of TNT and the soil microcosms were incubated for 4 months. The amount of extracted DNA decreased in the microcosms with a high TNT concentration [1.4 and 28.5 g TNT/kg (dry wt) of soil] over the incubation period. After 7 days of incubation of these soil microcosms, there was already a clear shift of their original flora towards a community dominated by Pseudomonadaceae, Xanthomonadaceae, Comamonadaceae and Caulobacteraceae. These results indicate that TNT affects soil bacterial diversity by selecting a narrow range of bacterial species that belong mostly to Pseudomonadaceae and Xanthomonadaceae.     

供磷水平和根际效应协同影响含碱性磷酸酶基因细菌群落的网络复杂性和稳定性北大核心

【目的】通过研究长期不同供磷水平下根际、土体土壤中编码碱性磷酸酶基因(alkaline phosphatase gene,phoD)细菌群落特征、网络复杂性、群落的稳定性及其与磷酸酶活性之间的关系,揭示供磷水平和根际效应在调控土壤有机磷矿化中的微生物学机制。【方法】选取华北平原长期施磷的小麦-玉米轮作体系石灰性土壤为基质土壤,开展根箱试验。选取的试验处理包括3个供磷水平,分别是0、50.0、200.0 kg P/hm^(2)(分别表示为P0、P50、P200)。玉米种子播种30 d后,采集玉米的根际土和土体土。采用高通量测序技术分析根际和土体土壤中编码碱性磷酸酶基因(phoD)细菌群落,探究施肥及根际效应对含phoD基因细菌的群落特征、网络特征的影响及其与磷酸酶活性的关系。【结果】随着施磷量的增加,速效磷(available P,AP)和碱性磷酸酶(alkaline phosphatase,ALP)活性在根际、土体土壤中均显著提高,且两者呈显著正相关。phoD基因丰度在P0、P200处理的根际土壤中显著高于土体土壤。含phoD基因细菌群落的α多样性在P50处理下的根际土壤显著高于土体土壤。冗余分析(redundancy analysis,RDA)表明,土壤中AP、有机磷(organic P,Po)和全磷(total P,Pt)是影响微生物群落的主要因素。与不施磷处理(P0)相比,施磷处理(P50、P200)下根际土壤中网络节点数和连接数降低,而土体土壤中网络节点数和连接数增加;同时,施磷处理含phoD基因细菌群落的鲁棒性(robustness)在根际土壤中显著提高,而在土体土壤中显著降低。Mantel检验表明,含phoD基因微生物群落中的优势物种在根际土壤与AP、酸性磷酸酶(acid phosphatase,ACP)、内聚力(cohesion)和网络的鲁棒性显著相关,在土体土壤中无显著性。【结论】供磷水平及根际效应协同影响phoD基因丰度、含phoD基因细菌群落的α多样性、群落结构、优势物种、网络的复杂性及群落的稳定性,进而影响磷酸酶活性,调控了土壤中有机磷的矿化。     

Isolation and structural characterisation of two antibacterial free fatty acids from the marine diatom, <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis>

One solution to the global crisis of antibiotic resistance is the discovery of novel antimicrobial compounds for clinical application. Marine organisms are an attractive and, as yet, relatively untapped resource of new natural products. Cell extracts from the marine diatom, Phaeodactylum tricornutum, have antibacterial activity and the fatty acid, eicosapentaenoic acid (EPA), has been identified as one compound responsible for this activity. During the isolation of EPA, it became apparent that the extracts contained further antibacterial compounds. The present study was undertaken to isolate these additional antibacterial factors using silica column chromatography and reverse-phase high-performance liquid chromatography. Two antibacterial fractions, each containing a pure compound, were isolated and their chemical structures were investigated by mass spectrometry and nuclear magnetic resonance spectroscopy. The antibacterial compounds were identified as the monounsaturated fatty acid (9Z)-hexadecenoic acid (palmitoleic acid; C16:1 n-7) and the relatively unusual polyunsaturated fatty acid (6Z, 9Z, 12Z)-hexadecatrienoic acid (HTA; C16:3 n-4). Both are active against Gram-positive bacteria with HTA further inhibitory to the growth of the Gram-negative marine pathogen, Listonella anguillarum. Palmitoleic acid is active at micro-molar concentrations, kills bacteria rapidly, and is highly active against multidrug-resistant Staphylococcus aureus. These free fatty acids warrant further investigation as a new potential therapy for drug-resistant infections.     

Antibacterial activity of certain plant extracts against bacterial wilt of tomato

Abstract

Five isolates of Ralstonia solanacearum were isolated from a naturally wilted root of tomato plants grown in Assiut governorate. The antibacterial activity of extract of Datura, Garlic and Nerium were tested in controlling R. solanacearum in vitro and in vivo. Garlic exhibited the strongest antibacterial activity against bacterial wilt in vitro and in vivo followed by Datura and then Nerium. Cold water extracts of these plant species were more effective than hot water extract in the development of the disease in vivo. In greenhouse experiments, the application of the tested plant extract to soil at the time of inoculation, two days before inoculation and two days after inoculation the pathogen, significantly reduced the disease index of wilt on Super Marmande tomato cultivars. The application of plant extracts at the same time as inoculation resulted in the highest reduction of disease index.     

Dynamics of total surface bacteria and bacterial species counts during desiccation in the Malaysian sea lettuce, Ulva reticulata (Ulvales, Chlorophyta)

The present study illustrates the dynamics of surface bacteria during post‐harvest desiccation of Ulva reticulata Forsskal. Algal fronds were subjected to desiccation for 31 days. The total surface bacteria and bacterial species counts were monitored for moisture content and water activity index (a_w). There was an 86% decrease in total algal moisture content. However, a_w showed a more gradual decrease. The total bacterial count increased in the first week, reaching a maximum on day 7. After this, there was a drastic drop in the total bacterial count until day 14, and then a more gradual decline towards the end of the process. Six species of bacteria were isolated throughout this process: Azomonas sp., Aeromonas hydrophila, Vibrio alginolyti‐cus, Escherichia coli, Proteus vulgaris and Vibrio para‐haemolyticus. The dynamics of each of these bacterial species exhibited trends similar to the total bacterial count. Based on these findings, the drastic decrease in the total bacterial count after seventh day of desiccation could not be attributed to the a_w or salinity. Therefore, the possible exposure of these bacteria to the algal internal fluid upon the rupture of the thallus cells was seen as the most likely reason for the drop in the bacterial population. Scanning electron microscope micrographs taken after the tenth day of desiccation showed the presence of cracks and areas where the bacteria were exposed to the algal internal fluid. In vitro antibacterial tests of three different solvent extracts of Ulva reticulata were also carried out against these surface bacteria to verify the antibacterial potential of its internal fluid. It was apparent that all these surface bacteria were inhibited by at least one of the three extracts, and there were indications of the possible presence of multicompound antibacterial potential, since extracts of different polarity showed bacteria‐specific activity. Hence, it is possible that Ulva reticulata has the potential to protect itself against the opportunistic bacteria present on its surface and in its environment.     

Anti-mosquito and antimicrobial nor-halimanoids, isocoumarins and an anilinoid from Tessmannia densiflora

The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5-pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products.     

喀斯特石漠化治理区钙果种植年限对根内细菌群落的影响

存在于健康植物根中的内生细菌不但能够与宿主植物建立共生关系,而且还具有促进植物生长、提升植物对营养元素摄取能力等功能,从而对维持陆地生态平衡、提升喀斯特石漠化综合治理成效具有重要的意义。【目的】探究宿主植物根中的内生细菌群落结构,为深入认识宿主植物-内生细菌的互作机制提供理论依据。【方法】以被引种到喀斯特断陷盆地石漠化综合治理区不同种植年限钙果根中的内生细菌和根际土为研究对象,分析根内生细菌群落特征和根际土理化性质。【结果】钙果种植年限对研究区土壤质量整体有着直接、显著的影响,并间接影响根内生细菌群落。根内生细菌群落以共生互作为主,通过共网络结构识别出种植第一年和第三年的前三位优势属为链霉菌属(Streptomyces)、卡氏伯克霍尔德菌属(Burkholderia-Caballeronia- Paraburkholderia)和噬几丁质菌属(Chitinophaga),种植第五年的前三位优势属为Streptomyces、Chitinophaga和海无柄孢囊黏细菌属(Haliangium)。根内生细菌群落的形成主要由随机性过程中的生态漂变所主导。【结论】不同生长阶段钙果根内生细菌群落结构的差异是由于随机性过程赋予了微生物物种多样化。内生细菌群落的共生互作关系以及优势菌具有生防功能,可增强钙果定殖能力和生长,进而提升钙果在喀斯特断陷盆地石漠化综合治理区的生态效益和经济效益。     

具有优良抑菌特性乳酸菌的筛选鉴定及活性物质检测

【背景】有益性乳酸菌在人体和动物体内分布极为广泛,是维持胃肠道菌群平衡、提高机体免疫力的主力军。近年来,为了解决禁用抗生素而导致动物发病率不断增高的问题,分析和研究乳酸菌及其所产活性物质的益生特性并开发新型饲料添加剂成为一个重要手段。【目的】本实验旨在从土壤中分离筛选出具有优良抑菌特性的乳酸菌,并对其所产活性物质的特性进行分析评价。【方法】采用溴甲酚紫平板法筛选并结合抑菌能力检测,得到2株具有优良抑菌特性的产酸菌株,分别命名为H-3和H-4。经形态学鉴定及16S rRNA基因序列测定后,对2株菌分别进行生长曲线和产酸量检测;通过排除酸处理、蛋白酶处理和热处理的方法分析2株菌所产抑菌物质的有效成分。【结果】H-3和H-4菌株经初步鉴定为乳酸片球菌(Pediococcus acidilactici),2株菌均具有良好的生长性能及产酸性能。菌株发酵上清液对大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)、猪霍乱沙门氏菌(Salmonella choleraesuis)、福氏志贺氏菌(Shigella flexneri)均表现出明显的抑...     

药用植物刺山柑不同部位细菌群落结构及其多样性

【目的】研究传统药用植物刺山柑（Capparis spinosa L.）不同部位细菌群落结构、物种组成和多样性特征,为药用植物微生物资源的开发及微生物与宿主互作提供理论依据。【方法】本研究以刺山柑地上部植物组织（果实、茎）和地下部土壤（根际土壤、非根际土壤）为研究材料,采用高通量测序技术分析刺山柑不同部位细菌的16S rRNA基因多样性,比较其细菌群落结构和物种组成特征。【结果】刺山柑4种样本共获得的3 649个操作分类单元（operational taxonomic unit,OTU）,属于34门、88纲、248目、464科和1 051属。土壤样本的细菌多样性大于植物组织,细菌群落多样性以根际土壤、非根际土壤、茎和果实的顺序逐渐降低,果实内生细菌群落多样性始终最低,显著低于根际土壤。不同部位相对丰度较高的细菌门如下：植物组织中以变形菌门为主,根际土壤中为变形菌门和放线菌门,非根际土中为厚壁菌门和放线菌门。无色杆菌属（Achromobacter）、欧文氏菌属（Erwinia）、肠球菌属（Enterococcus）、微小杆菌属（Exiguobacterium）、乳杆菌属（Lactobacillus）和克雷伯氏菌属（Klebsiella）主要存在于刺山柑植物组织中。游动球菌属（Planomicrobium）、库克菌属（Kocuria）、类芽孢杆菌属（Paenibacillus）、链霉菌属（Streptomyces）、微枝形杆菌属（Microvirga）和节杆菌属（Arthrobacter）主要分布于土壤中。β多样性分析结果表明,刺山柑植物组织和土壤的细菌群落结构具有显著差异,同类型样本的细菌群落结构相似。【结论】刺山柑土壤样本中细菌群落的多样性和丰富度均高于植物组织,刺山柑不同部位的细菌群落组成不同。本研究对刺山柑不同部位细菌群落结构进行了初步分析,鉴定了各部位细菌群落中的核心菌群,为以后挖掘刺山柑的功能研究和利用提供了准确的微生物信息。     

黄萎病不同发生程度棉田中土壤微生物多样性

作物根际土壤微生物群落对土壤生态及作物健康至关重要。以棉花黄萎病不同发生程度棉田的土壤为研究对象,采用理化分析、微生物纯培养及高通量测序技术对土壤理化性质及微生物数量、细菌丰度多样性进行综合分析。结果表明:在纯培养条件下,大丽轮枝菌无菌发酵滤液对细菌生长有明显的抑制作用;棉田接种大丽轮枝菌对土壤中细菌、真菌、放线菌的数量及细菌菌群丰度多样性未产生明显影响,不同采样时间的土壤中细菌菌群结构差异更大。土壤中大丽轮枝菌微菌核数量与棉花黄萎病的发生程度呈显著正相关。土壤肥力对土壤中微生物数量起主导作用,而水稻-棉花轮作能够使棉田有效降盐、减病、改善土壤肥力。通过生物防治、作物轮作、深翻等调控措施增加土壤中有益菌群数量、改善土壤生态、降低棉田土壤中大丽轮枝菌菌源数量是减轻棉花黄萎病危害的基础。     

Antibacterial activity of the leaf essential oil of <Emphasis Type="Italic">Blumea mollis</Emphasis> (D. Don) Merr.

The antibacterial activity of the leaf essential oil of Blumea mollis was assayed against 14 clinically isolated bacterial strains on Muller–Hinton Agar medium and Muller–Hinton Agar medium with 5% sheep blood. The essential oil had promising antibacterial activity against all the bacterial strains tested. The highest mean zone of inhibition and lowest values of minimum inhibitory concentration were recorded against methicillin-resistant Staphylococcus aureus followed by beta hemolytic Streptococcus pyogenes. The Gram-positive bacteria were more sensitive than Gram-negative bacteria. Among the bacterial strains tested, Psudomonas aeruginosa was resistant to the essential oil. The results of the present study suggest that the essential oil of B. mollis is one of the new medicinal resources as an antibacterial agent against the bacterial strains tested.     

Changes in microbial activity and composition in a pasture ecosystem exposed to elevated atmospheric carbon dioxide

Elevated atmospheric CO₂ increases aboveground plant growth and productivity. However, carbon dioxide-induced alterations in plant growth are also likely to affect belowground processes, including the composition of soil biota. We investigated the influence of increased atmospheric CO₂on bacterial numbers and activity, and on soil microbial community composition in a pasture ecosystem under Free-Air Carbon Dioxide Enrichment (FACE). Composition of the soil microbial communities, in rhizosphere and bulk soil, under two atmospheric CO₂ levels was evaluated by using phospholipid fatty acid analysis (PLFA), and total and respiring bacteria counts were determined by epifluorescence microscopy. While populations increased with elevated atmospheric CO₂ in bulk soil of white clover (Trifolium repens L.), a higher atmospheric CO₂ concentration did not affect total or metabolically active bacteria in bulk soil of perennial ryegrass (Lolium perenne L.). There was no effect of atmospheric CO₂ on total bacteria populations per gram of rhizosphere soil. The combined effect of elevated CO₂ on total root length of each species and the bacterial population in these rhizospheres, however, resulted in an 85% increase in total rhizosphere bacteria and a 170% increase in respiring rhizosphere bacteria for the two plant species, when assessed on a per unit land area basis. Differences in microbial community composition between rhizosphere and bulk soil were evident in samples from white clover, and these communities changed in response to CO₂ enrichment. Results of this study indicate that changes in soil microbial activity, numbers, and community composition are likely to occur under elevated atmospheric CO₂, but the extent of those changes depend on plant species and the distance that microbes are from the immediate vicinity of the plant root surface.     

巨菌草不同生长时期对砒砂岩地区土壤理化性质及细菌群落结构的影响

[目的]揭示巨菌草种植前及其不同生长时期对砒砂岩地区土壤基本理化性质及细菌群落结构的影响,为更好应用巨菌草改良砒砂岩地区土壤提供理论依据。[方法]运用Illumina MiSeq高通量测序技术,在门、属水平上比较砒砂岩地区巨菌草不同生长时期对土壤细菌结构及多样性的影响。[结果]巨菌草种植后,三块样地的含水量在巨菌草分蘖期最低,在成熟期达到最高,土壤有机含量有所增加,土壤pH值变化不明显。细菌菌群结构：各样地的土壤细菌在巨菌草种植前及其生长的四个时期,门水平上的优势菌群均为放线菌门（Actinobacteria）、变形菌门（Proteobacteria）;在属水平上,含量最高的是未分类（unidentified）的细菌。Alpha多样性及群落组成丰度分析表明,三块样地种植巨菌草后,其细菌多样性和物种丰度均比种植前高,农田地土壤细菌多样性和物种丰度在巨菌草拔节期达到峰值,在分蘖期土壤细菌数量最大,比种植前土壤细菌数量高出8倍多,达2.09×10⁷ CFU/g干土,山顶地土壤细菌多样性和物种丰度在巨菌草分蘖期达到峰值,河滩地土壤细菌多样性在巨菌草苗期达到峰值,其丰富度在拔节期达到最大。[结论]砒砂岩地区土壤细菌群落结构在巨菌草不同生长时期相似,巨菌草能明显促进砒砂岩地区土壤细菌菌群多样性和丰富度,能有效提高土壤有机质含量,但砒砂岩地区各样地土壤细菌多样性、数量和有机质含量达到峰值的时期不同。     

Contrasting effects of extracts from invasive Reynoutria japonica on soil microbial biomass,activity, and community structure

Invasive plants may modify soil properties through the release of phenolic compounds. The effects of phenolics produced by a noxious invader, Reynoutria japonica, on soil microorganisms have rarely been studied in experimental conditions. We performed a laboratory experiment to assess the influence of extracts from R. japonica on soil microbial activity, biomass, and community structure. Two types of extracts (shoots and rhizomes) were added in four concentrations (control—no extract, low—extract diluted 100 times, medium—extract diluted ten times, and high—undiluted extract) to soil collected under native plant species. Concentrations of 12 phenolic compounds, namely catechin, chlorogenic acid, emodin, epicatechin, hyperoside, quercetin, physcion, piceatannol, polydatin, procyanidin B3, resveratrol, and resveratroloside were analyzed in the extract and soil. We measured the activity of five enzymes, namely acid and alkaline phosphatases, β-glucosidase, phenoloxidase, peroxidase, the activity of bacteria on Biolog Ecoplates, as well as the biomass of bacteria, saprotrophic fungi, arbuscular mycorrhizal fungi (AMF), and microbial community structure using phospholipid (PLFA) and neutral (NLFA) fatty acid analysis. Many microbial parameters, namely phosphatase activities, total microbial, AMF, and G?+?bacterial biomass, were reduced following the addition of extracts. This was likely related to phenolics as concentrations of these compounds in soil increased with the concentration of extract added. In contrast, saprotrophic fungi and G- bacteria were largely positively affected by extract addition. Shoot and rhizome extracts had relatively similar effects on the soil properties. The changes in soil biota caused by R. japonica invasion may have implications for restoration of invaded areas.

     

36种中药材体外抗菌活性筛选研究

该文研究36种常用中药材80%乙醇提取物在体外抗临床常见致病菌的抗菌活性。采用药敏纸片法测耐药菌的耐药谱,中药粗粉用80%乙醇浸泡提取,提取液减压浓缩得浸膏,通过琼脂打孔法测定提取物抑菌圈,再通过微量倍比稀释法测定最低抑菌浓度(MIC)和最低杀菌浓度(MBC)。结果表明:36种中药材醇提物中,有15种具有广谱抗菌活性,对实验中各标准菌表现出不同程度的抑制作用,对MRSA抗菌活性也较强。其中,岩陀、卷柏、首乌藤、苏木、乌药、夏枯草6种药材的抗菌活性比较突出,抑菌圈均大于11 mm,细菌对其表现为中高度敏感;它们对7株标准菌的MIC/MBC值除个别为12.5 mg·m L~(-1)以外,均小于1.563 mg·m L~(-1),对16株MRSA的MIC/MBC值均小于1.563 mg·m L~(-1),它们的萃取层活性均小于1 mg·m L~(-1)。所筛选出的15种抗菌活性较强的中药材,可为后续研究其活性单体化合物和作用机制,研发有效的抗多重耐药菌的中药制剂以及解决细菌耐药性问题提供一定的参考。     

半干旱区沙地蒿类植被建成对土壤细菌的影响

半干旱区沙地土壤发育早期依赖固沙植被建成,油蒿和差巴嘎蒿作为我国北方半干旱区沙地半灌木植物群落的主要先锋种和建群种,研究其建成对土壤细菌群落变化的影响对沙质草原生态系统稳定性有重要意义。因此,围绕两个典型的半干旱区(科尔沁沙地和毛乌素沙地),通过高通量测序的方法探讨了蒿类群落生长前后两个阶段(流动沙丘和藓类结皮)的土壤细菌多样性和群落组成变化规律,结果表明:(1)植被建成前后,土壤总碳、总氮、全磷、电导率和含水率均有显著差异,而pH值在不同阶段变化不显著;(2)植被建成前后,土壤细菌多样性变化不显著,但是细菌群落组成在不同阶段具有较大差异。在门类水平上,厚壁菌门(Firmicutes)、拟杆菌(Bacteroidetes)、变形菌门(Proteobacteria)和放线菌(Actinobacteria)均是两个阶段的优势菌,但随着蒿类植被建成和土壤养分的积累,厚壁菌门的相对丰度降低,变形菌门和放线菌门的相对丰度增加;(3)两个阶段,不同深度土壤理化性质和优势菌的相对丰度均存在变化;(4)两种典型沙地土壤理化特性和细菌群落在植被建成前后的变化规律存在共性。通过空间代替时间序列的方法,阐明了土壤细菌群落随着半干旱沙地同类型植被建成的变化模式,可为总结半干旱区植被恢复与成土过程的关系提供参考和思路。     

Assessment of Antibacterial Activity of Solanum surrattense Against Waterborne Pathogens Isolated from Surface Drinking Water of the Potohar Region in Pakistan

People dwelling in different cities of the Potohar region, Pakistan, are mostly dependent on surface water for drinking and domestic use. In an attempt to make available potable, safe water, filtration plants were constructed along with dams in the Potohar region. Water samples from these filtration plants were collected and analyzed for total and faecal coliform bacteria as well as for total viable count. Results showed that bacterial indicators of faecal contamination were numerous and significantly greater than World Health Organization recommended guidelines. Accordingly, antibacterial activity of methanolic and aqueous extracts of different parts of Solanum surrattense were assessed in vitro against waterborne pathogens. Fruits exhibited more antibacterial activities at incubation at 37°C than shoots and roots, which showed lowest Minimum Inhibitory Concentration (MIC) and zones of inhibition. These results suggest that plants offer a great potential for purification of drinking water that needs to be explored further because fruit extract of the aforementioned plant can be of practical use against waterborne pathogens.     

芽胞杆菌浸种对水稻内生细菌群落结构的影响

水稻内生细菌群落是反映植株内环境是否健康稳定的重要生物学指标,芽胞杆菌是防治水稻病害的重要生防微生物。为揭示芽胞杆菌浸种处理对水稻内生细菌群落结构的影响,采用Illumina MiSeq测序的方法对水稻内生细菌的16S rRNA基因进行测序,剖析了芽胞杆菌浸种处理对不同水稻组织内生细菌的微生态调控作用。结果表明,3种芽胞杆菌浸种处理可以提高水稻根和茎部内生细菌群落的丰富度和均匀度,降低叶部内生细菌群落的丰富度和均匀度,显著增加根部内生细菌群落多样性。变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes)是水稻根部和茎部共有优势菌门,厚壁菌门和芽胞杆菌属(Bacillus)是叶部共有优势菌门和属。芽胞杆菌浸种处理显著提高了叶部内生厚壁菌门和芽胞杆菌属的相对丰度,增加了根系和茎部组织内生细菌的分类单元OTU(Operational Taxonomic Units)数量,对叶部组织影响不明显;降低了茎部和叶部中参与各种代谢通路的内生细菌丰度,显著增加了根部参与代谢通路的内生细菌丰度。因此,3种芽胞杆菌浸种处理可以显著改变水稻根部、茎部和叶部内生细菌群落结构,改善水稻生长的微生态环境。