Geomicrobiological Changes in Two Ephemeral Desert Playa Lakes in the Western United States

The geochemistry and microbiology of two ephemeral playa lakes in the Western United States, Surprise Valley Alkali Lake (SVAL) and Eldorado Playa (EP), were examined over one wetting cycle, revealing dramatic temporal changes in suspended mineralogy, aqueous chemistry, and bacterial populations. In SVAL the predominant suspended mineral changed from smectite to vermiculite and clinoptilolite, which led to a depletion of soluble Mg²⁺. Nitrate became depleted in both playas as a result of biological nitrogen demand imparted by unusually dense microbial communities reaching ～1 × 10⁸ cultivable heterotrophs per ml of water. One hundred eighty eight bacterial isolates were obtained, representing sixty phylotypes and four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. Phylogenetic analyses suggested that the microbial communities reflected different phases of succession, with SVAL changing from a diverse community with abundant Yonghaparkia to a less diverse late summer community with abundant Bacteroidetes and Proteobacteria such as Loktanella, Rhodobaca, Saccharospirillum, Flexibacter, and phylogenetically novel members of the Flexibacteriaceae. In EP, a diverse assemblage of bacteria often associated with soils was replaced very quickly by a much less even community dominated by Yonghaparkia, Sandarakinorhabdus, and relatives of Belliella baltica. Strikingly, the early summer microbial community from SVAL was not significantly different from the EP community that developed within one week of flooding, even though these playas are almost 1000 km apart, whereas sympatric communities in different phases of succession were different. To our knowledge, this is one of the first geomicrobiological studies of a recharge playa, the dominant playa type worldwide.     

Isolation and diversity of culturable rhizobacteria associated with economically important crops and uncultivated plants in Québec,Canada

Plants are chronically associated with microorganisms, residing all tissues. Holonomic analysis of diversity of established rhizobacteria in uncultivated plants is scarce. Thus, the present study was conducted to access the root-associated bacterial diversity of 6 crops (maize, canola, soybean, reed canarygrass, alfafa, and miscanthus) and 20 uncultivated plant species in the region of Sainte-Anne-de-Bellevue, Québec, Canada, using pure-culture methods. Based on 16S rRNA gene sequence analysis, 446 bacterial isolates were distributed onto four phyla (Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes), 32 families and 90 genera. Proteobacteria constituted the largest group of isolates (240), 40% of ectophytic and 61% of endophytic bacteria. Representatives of the genera Bacillus and Pseudomonas dominated in rhizosphere soil; Microbacterium and Pseudomonas were the predominant endophytes. Some genera were associated with specific plant species, such as Stenotrophomonas, Yersinia, Labrys and Luteibacter. Several endophytes were occasionally observed in the rhizosphere, and vice versa. This is the first survey of culturable endophytic bacteria associated with uncultivated plants in Québec. The culturable bacterial community studied herein are assumed to represent a portion of the entire phytomicrobiome of the evaluated plants. Results confirmed that the crops and uncultivated plants of Québec represent an extremely rich reservoir of diverse rhizobacteria.     

Heterotrophic bacteria associated with the green alga <Emphasis Type="Italic">Ulva rigida</Emphasis>: identification and antimicrobial potential

Heterotrophic bacteria associated with the green alga Ulva rigida, collected from the coast of Tunisia, were isolated and subsequently identified by their 16S rRNA gene sequences and by phylogenetic analysis. The 71 isolates belong to four phyla: Proteobacteria (Alpha-and Gamma- subclasses), Bacteroidetes, Firmicutes, and Actinobacteria. Most of the isolates belong to Proteobacteria. The Gram-positive Firmicutes and especially the genus Bacillus were well-represented at the surface of U. rigida, collected from the coast as well as from the lagoon, while Actinobacteria were represented only at the surface of algae collected from the coast of Cap Zebib. Bacteroidetes were more represented at the surface of algae collected from the Ghar El Melh lagoon. The bacterial community of the water surrounding the algae was different from that associated with the surface of the algae. Moreover, the abundance of bacteria in the surrounding water was much lower compared to the density of bacteria associated with the surface of the algae. Bacteria isolated from the algal surface were tested for their antimicrobial potential. The results show that ~?36% of the algae-associated bacterial isolates possess antibacterial activity whereas free-living bacteria, isolated from the surrounding water, did not show such activity. The surface of U. rigida was colonized by a high diversity of culturable and possibly novel epiphytic bacteria that may be an important source of antimicrobial compounds and are therefore of biotechnological interest.     

Bacterial diversity in surface sediments from the Pacific Arctic Ocean

In order to assess bacterial diversity within four surface sediment samples (0–5 cm) collected from the Pacific Arctic Ocean, 16S ribosomal DNA clone library analysis was performed. Near full length 16S rDNA sequences were obtained for 463 clones from four libraries and 13 distinct major lineages of Bacteria were identified (α, β, γ, δ and ε-Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, Firmicutes, Planctomycetes, Spirochetes, and Verrucomicrobia). α, γ, and δ-Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria were common phylogenetic groups from all the sediments. The γ-Proteobacteria were the dominant bacterial lineage, representing near or over 50% of the clones. Over 35% of γ-Proteobacteria clones of four clone library were closely related to cultured bacterial isolates with similarity values ranging from 94 to 100%. The community composition was different among sampling sites, which potentially was related to geochemical differences.     

Bacterial community composition of the gut microbiota of <Emphasis Type="Italic">Cylindroiulus fulviceps</Emphasis> (diplopoda) as revealed by molecular fingerprinting and cloning

Bacterial clone libraries of the gut microbiota of nurtured and starved Cylindroiulus fulviceps specimens displayed the predominance of the phyla Bacteroidetes (55 and 37 %, respectively) and Proteobacteria (40 and 35 %, respectively) and a high similarity to bacteria previously detected in the intestinal tract of termites and beetles, which are known to harbor symbiotic bacteria essential for digestive activity. Bacterial isolates were dominated by Proteobacteria (74 %), followed by members of the phyla Actinobacteria, Firmicutes and Bacteroidetes. PCR-DGGE fingerprints of the gut samples showed that intestinal bacteria were affected by starvation, although the change was not significant.     

Roots of the xerophyte Panicum turgidum host a cohort of ionizing-radiation-resistant biotechnologically-valuable bacteria

Bacterial communities associated with roots of Panicum turgidum, exposed to arid conditions, were investigated with a combination of cultural and metataxonomic approaches. Traditional culture-based techniques were used and 32 isolates from the irradiated roots were identified as belonging to Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria phyla. Four actinobacterial strains were shown to be ionizing-radiation (IR)-resistant: Microbacterium sp. PT8 (4.8 kGy (kGy)), Micrococcus sp. PT11 (4.4 kGy), Kocuria rhizophila PT10 (2.9 kGy) and Promicromonospora panici PT9^T (2.6 kGy), based on the D₁₀ dose necessary for a 90% reduction in colony forming units (CFU). Concerning the investigation of microbial communities in situ, metataxonomic analyses of the diversity of IR-resistant microorganisms associated with irradiated roots revealed a marked dominance of Actinobacteria (46.6%) and Proteobacteria (31.5%) compared to Bacteroidetes (4.6%) and Firmicutes (3.2%). Gamma irradiation not only changed the structure of bacterial communities, but also affected their functional properties. Comparative analyses of metabolic profiles indicated the induction of several pathways related to adaptation to oxidative stress in irradiated roots, such as DNA repair, secondary metabolites synthesis, reactive oxygen species (ROS)-mitigating enzymes, etc. P. turgidum is emblematic of desert-adapted plants. Until now, there is no other work that has focused on the microbial profile of irradiated roots of this xerophyte.     

Broad Diversity and Newly Cultured Bacterial Isolates from Enrichment of Pig Feces on Complex Polysaccharides

One of the fascinating functions of mammalian intestinal microbiota is fermentation of plant cell wall components. Eight-week continuous culture enrichments of pig feces with cellulose and xylan/pectin were used to isolate bacteria from this community. A total of 575 bacterial isolates were classified phylogenetically using 16S rRNA gene sequencing. Six phyla were represented in the bacterial isolates: Firmicutes (242), Bacteroidetes (185), Proteobacteria (65), Fusobacteria (55), Actinobacteria (23), and Synergistetes (5). The majority of the bacterial isolates had ≥97 % similarity to cultured bacteria with sequences in the RDP, but 179 isolates represent new species and/or genera. Within the Firmicutes isolates, most were classified in the families of Lachnospiraceae, Enterococcaceae, Staphylococcaceae, and Clostridiaceae I. The majority of the Bacteroidetes were most closely related to Bacteroides thetaiotaomicron, Bacteroides ovatus, and B. xylanisolvens. Many of the Firmicutes and Bacteroidetes isolates were identified as species that possess enzymes that ferment plant cell wall components, and the rest likely support these bacteria. The microbial communities that arose in these enrichment cultures had broad bacterial diversity. With over 30 % of the isolates not represented in culture, there are new opportunities to study genomic and metabolic capacities of these members of the complex intestinal microbiota.     

Diazotrophic diversity in the rhizosphere of two exotic weed plants, Prosopis juliflora and Parthenium hysterophorus

This study is aimed at assessing culturable diazotrophic bacterial diversity in the rhizosphere of Prosopis juliflora and Parthenium hysterophorus, which grow profusely in nutritionally-poor soils and environmentally-stress conditions so as to identify some novel strains for bioinoculant technology. Diazotrophic isolates from Prosopis and Parthenium rhizosphere were characterized for nitrogenase activity by Acetylene Reduction Assay (ARA) and 16S rRNA gene sequencing. Further, the culture-independent quantitative PCR (qPCR) was performed to compare the abundance of diazotrophs in rhizosphere with bulk soils. The proportion of diazotrophs in total heterotrophs was higher in rhizosphere than bulk soils and 32 putative diazotrophs from rhizosphere of two plants were identified by nifH gene amplification. The ARA activity of the isolates ranged from 40 to 95 nmol ethylene h⁻¹ mg protein⁻¹. The 16S rRNA gene analysis identified the isolates to be members of alpha, beta and gamma Proteobacteria and firmicutes. The qPCR assay also confirmed that abundance of nif gene in rhizosphere of these two plants was 10-fold higher than bulk soil.     

美洲大蠊成虫肠道可培养细菌多样性研究

【目的】了解美洲大蠊成虫肠道可培养细菌的多样性。【方法】运用纯培养法、数值分类和16S rRNA基因序列的系统发育分析对样品中可培养细菌多样性进行研究。【结果】从NA培养基中分离得到54株细菌,根据形态观察和部分生理生化特性,选取32个代表性菌株进行16S rRNA基因序列的系统发育多样性分析。结果表明,数值分类中的代表菌株在82%相似水平上可分为12个表观群;这些分离菌株代表20个物种,属于4个大的系统发育类群(Proteobacteria,Bacteroidetes,Firmicutes,Actinobacteria)的10个科、15个属。多数菌株属于Proteobacteria门(15株,占46.9%)和Bacteroidetes门(10株,占31.3%)。【结论】美洲大蠊成虫肠道内存在较为丰富的细菌多样性。     

Diversity of Culturable Bacteria Associated with Ascocarps of a Chinese White Truffle,Tuber panzhihuanense (Ascomycota)*

Culturable bacterial communities inhabiting ascocarps of Tuber panzhihuanense were investigated. Isolates obtained on tryptone soy agar (TSA) were screened with high performance capillary electrophoresis (HPCE) according to differences in size of 16S rDNA V3. Target isolates were identified by analysis of the whole length of 16S rDNA gene. The results revealed that the ascocarps of T. panzhihuanense harbored a great number of culturable bacteria which belonging to 20 species and 11 genera in 5 phyla. Most isolates (4968%) were affiliated to the γ Proteobacteria, dominated by Pseudomonas lurida. The second major subclass was α Proteobacteria (3742%), with Phyllobacterium and a nitrogen fixing bacterium Bradyrhizobium japonicum also occurring as dominant taxa. The remaining bacterial isolates contained members of Actinobacteria (322%) and Firmicutes (774%) of which Bacillus was the commonest bacterium. A novel Tuber associated culturable bacterium species, Terriglobus roseus, was isolated and detected for the first time in Tuber ascocarps.     

中国白块菌——攀枝花块菌子囊果内可培养细菌的多样性研究

对新近发现的块菌属一新种——攀枝花白块菌（Tuber panzhihuanense）子囊果中可培养细菌的多样性进行了研究。采用胰蛋白大豆培养基（TSA）对菌株进行分离。用毛细管电泳（HPCE）对所有获得的菌株的16S rDNA V3高变区进行筛选获得不同条带大小的菌株,对筛选出的菌株的16S rDNA进行测序,并进行细菌多样性分析和研究。结果显示,攀枝花块菌子囊果内可培养细菌在数量及种类上都表现出很高的多样性,所有细菌分属于5个门的11个属和20个种。在所分离到的变形菌门的细菌中,数量最多的菌株（4968%）属于γ Proteobacteria,其中假单胞菌属的Pseudomonas lurida为优势类群;其次为α Proteobacteria,占3742%,其中以固氮菌 Bradyrhizobium japonicum和Phyllobacterium spp.为优势类群。其余的菌株属于放线菌门（Actinobacteria） （322%）和厚壁菌门（Firmicutes） （774%）,厚壁菌门中以芽孢杆菌属（Bacillus）为代表菌群。酸杆菌门中的Terriglobus roseus（194%）首次从块菌中分离获得。     

Bacterial Endosymbionts of Pyrodinium bahamense var. compressum

The study presents evidence in support of the bacterial theory associated with the toxicity of Pyrodinium bahamense var. compressum. Bacterial endosymbionts from Philippine P. bahamense var. compressum strain Pbc MZRVA 042595 were isolated and identified via 16S rDNA sequence analysis. Taxonomic diversity of the identified culturable intracellular microbiota associated with Philippine P. bahamense var. compressum was established to be limited to the Phyla Proteobacteria, Actinobacteria, and Firmicutes. Major endosymbionts identified included Moraxella spp., Erythrobacter spp., and Bacillus spp., whereas Pseudomonas putida, Micrococcus spp., and Dietzia maris were identified as minor isolates. All identified strains except D. maris, P. putida, and Micrococcus spp. were shown to contain either saxitoxin or neo saxitoxin or both at levels ≤73 ng/10⁷ bacterial cells based on high-performance liquid chromatography analysis. Paralytic shellfish poisoning-like physiologic reactions in test animals used in the mouse assay were recorded for the endosymbionts except for P. putida. The study is the first to elucidate the possible contribution of bacterial endosymbionts in the toxicity of P. bahamense var. compressum isolated in the Philippines.     

Use of plate-wash samples to monitor the fates of culturable bacteria in mercury- and trichloroethylene-contaminated soils

With the ultimate aim of developing bioremediation technology that use the optimum bacterial community for each pollutant, we performed polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis and identified communities of culturable bacteria in HgCl(2)- and trichloroethylene (TCE)-contaminated soil microcosms. PCR-DGGE band patterns were similar at 0 and 1 ppm HgCl(2), but changes in specific bands occurred at 10 ppm HgCl(2). Band patterns appearing at 10 and 100 ppm TCE were very different from those at 0 ppm. Phylogenetic analysis showed four bacterial groups in the HgCl(2)-contaminatied cultures: Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes. Most high-density bands, decreased-density bands, and common bands were classified into the phyla Proteobacteria, Actinobacteria, and Firmicutes, respectively; the effects of HgCl(2) on culturable bacteria appeared to differ among phyla. Duganella violaceinigra [98.4% similarity to DNA Data Bank of Japan (DDBJ) strain], Lysobacter koreensis (98.2%), and Bacillus panaciterrae (98.6%) were identified as bacteria specific to HgCl(2)-contaminated soils. Bacteria specific to TCE-contaminated soils were distributed into three phyla (Firmicutes, Proteobacteria, and Actinobacteria), but there was no clear relationship between phylum and TCE effects on culturable bacteria. Paenibacillus kobensis (97.3%), Paenibacillus curdlanolyticus (96.3%), Paenibacillus wynnii (99.8%), and Sphingomonas herbicidovorans (99.4%) were identified as bacteria specific to TCE-contaminated soils. These bacteria may be involved in pollutant degradation.     

Characterization of bacterial community in the stomach of yellow catfish (<Emphasis Type="Italic">Pelteobagrus fulvidraco</Emphasis>)

In this study, the traditional culture-based technique and the 16S rDNA sequencing method were used to investigate the characterization of bacterial community in the stomach contents and mucus of yellow catfish (Pelteobagrus fulvidraco). The culture-based technique disclosed that the average bacterial numbers in the gastric contents and mucus were 5.79 × 10⁷ cfu/g (cfu: colony forming unit) and 1.89 × 10⁵ cfu/g, respectively. Several different bacteria were obtained from gastric contents, including species from genera Bradyrhizobium, Phyllobacterium, Plesiomonas, Hafnia, Edwardsiella, Pseudomonas, and Bacillus. However, only two species were isolated from the gastric mucus, including species from genera Plesiomonas and Aeromonas. Forty-five phylotypes were observed from the 65 positive clones from the stomach contents (library SC); nineteen phylotypes were detected from the 45 clones from the stomach mucus (library SM). Further analyses revealed that the fish stomach harbored characteristic microbiota, where Firmicutes was dominant, followed by Proteobacteria and Bacteroidetes and Fusobacteria. This characterization of bacterial community is markedly different from that of the fish intestine, where Proteobacteria is predominant, followed by Fusobacteria and Firmicutes. Chloroflexi (1.5%) was only found in the library SC, while Actinobacteria (4.4%) was only found in the library SM, suggesting that microbiota of GI contents was quite different from that of GI mucus. In addition, several species of bacteria found in the stomach may be potentially opportunistic pathogens, indicating that fish digestive tract is a reservoir for many nosocomial pathogens.     

Phylogenetic profiling of bacterial community from two intimately located sites in Balramgari,North-East coast of India

Microbial communities in coastal subsurface sediments play an important role in biogeochemical cycles. In this study microbial communities in tidal subsurface sediments of Balramgari in the state of Orissa, India were investigated using a culture independent approach. Two 16S rDNA cloned libraries were prepared from the closely located (100 m along the coast) subsurface sediment samples. Library I sediment samples had higher organic carbon content but lower sand percentage in comparison to Library II. A total of 310 clone sequences were used for DOTUR analysis which revealed 51 unique phylotypes or operational taxonomic units (OTUs) for both libraries. The OTUs were affiliated with 13 major lineages of domain bacteria including Proteobacteria (α, β, δ and λ), Acidobacteria, Actinobacteria, Cyanobacteria, Chloroflexi, Firmicutes, Verrucomicrobia, Bacteroidetes, Gemmatimonadetes and TM7. We encountered few pathogenic bacteria such as Aeromonas hydrophila and Ochrobactrum intermedium, in sediment from Library I. ∫-LIBSHUFF comparison depicts that the two libraries were significantly different communities. Most of the OTUs from both libraries possessed ≥85% to <97% similarity to RDP database sequences depicting the putative presence of new species, genera and phylum. This work revealed the complex and unique bacterial diversity from coastal habitat of Balramgari and shows that, in coastal habitat a variability of physical and chemical parameter has a prominent impact on the microbial community structure.     

Isolation of novel bacteria, including a candidate division, from geothermal soils in New Zealand

We examined bacterial diversity of three geothermal soils in the Taupo Volcanic Zone of New Zealand. Phylogenetic analysis of 16S rRNA genes recovered directly from soils indicated that the bacterial communities differed in composition and richness, and were dominated by previously uncultured species of the phyla Actinobacteria , Acidobacteria , Chloroflexi , Proteobacteria and candidate division OP10. Aerobic, thermophilic, organotrophic bacteria were isolated using cultivation protocols that involved extended incubation times, low-pH media and gellan as a replacement gelling agent to agar. Isolates represented previously uncultured species, genera, classes, and even a new phylum of bacteria. They included members of the commonly cultivated phyla Proteobacteria , Firmicutes , Thermus/Deinococcus , Actinobacteria and Bacteroidetes , as well as more-difficult-to-cultivate groups. Isolates possessing < 85% 16S rRNA gene sequence identity to any cultivated species were obtained from the phyla Acidobacteria , Chloroflexi and the previously uncultured candidate division OP10. Several isolates were prevalent in 16S rRNA gene clone libraries constructed directly from the soils. A key factor facilitating isolation was the use of gellan-solidified plates, where the gellan itself served as an energy source for certain bacteria. The results indicate that geothermal soils are a rich potential source of novel bacteria, and that relatively simple cultivation techniques are practical for isolating bacteria from these habitats.     

崇测冰帽不同的冰川样品可培养细菌群落结构差异北大核心CSCD

【目的】研究细菌群落组成在西昆仑崇测冰帽冰川雪样、冰碛物和土样中的差异。【方法】通过传统的纯培养和菌株16S r RNA基因序列鉴定,分析菌株在门水平和属水平的群落结构。【结果】冰川细菌由Actinobacteria、Firmicutes、Proteobacteria和Bacteroidetes 4个门组成。雪样以Proteobacteria为优势,而土样和冰碛物则以Actinobacteria为优势。在属的水平上,冰川土样中的优势属仅有Arthrobacter,雪样中的优势属主要有Methylobacterium、Modestobacter、Hymenobacter、Brevundimonas、Bacillus这5种。雪环境的细菌群落结构与冰碛物和土样的差异性较大,而冰碛物和土样之间的差异性不大。Skermanella可能为崇测冰帽所特有的细菌。【结论】初步说明了在冰川退缩的气候环境下,冰川雪样细菌多样性的脆弱性,以及冰川雪环境细菌资源保护的重要性。     

Cultivable bacteria associated with Caribbean octocorals are active against coral pathogens but exhibit variable bioactivity when grown under different temperature conditions

Caribbean scleractinian corals have been declining in recent decades while octocorals appear to be thriving. Although microbial communities associated with scleractinians have been extensively studied, less is known about octocoral-associated communities. To investigate whether octocoral-associated microorganisms can provide resistance against coral pathogens, bacteria from the mucus and external surfaces of three common Caribbean octocoral species (Gorgonia ventalina, Eunicea flexuosa, and Antillogorgia americana) were isolated. Isolates were tested for bioactivity against six scleractinian coral pathogens at three temperatures to capture potential differences under varying conditions. Production of bioactive metabolites was evaluated using disk diffusion assays while growth competition assays determined whether the pathogen and isolate could establish simultaneously. Over half of the isolates, members of the phyla Actinobacteria, Firmicutes and Proteobacteria, produced compounds that inhibited the growth of one or more pathogens with some variation in bioactivity noted across temperatures. When inoculated simultaneously, most isolates were able to grow in presence of the pathogens while temperature did not have a significant impact. Collectively, these results demonstrate that octocorals support a diverse group of culturable bacteria capable of competing against coral pathogens. The putative protective roles of these bacteria provide insight into why Caribbean octocorals may be less susceptible to diseases and might explain their increasing prevalence on degraded reefs.

     

Distribution of Endophytic Bacteria in Alopecurus aequalis Sobol and Oxalis corniculata L. from Soils Contaminated by Polycyclic Aromatic Hydrocarbons

The distributions of endophytic bacteria in Alopecurus aequalis Sobol and Oxalis corniculata L. grown in soils contaminated with different levels of polycyclic aromatic hydrocarbons (PAHs) were investigated with polymerase chain reaction followed by denaturing gradient gel electrophoresis technology (PCR-DGGE) and cultivation methods. Twelve types of PAHs, at concentrations varying from 0.16 to 180 mg·kg⁻¹, were observed in the roots and shoots of the two plants. The total PAH concentrations in Alopecurus aequalis Sobol obtained from three different PAH-contaminated stations were 184, 197, and 304 mg·kg⁻¹, and the total PAH concentrations in Oxalis corniculata L. were 251, 346, and 600 mg·kg⁻¹, respectively. The PCR-DGGE results showed that the endophytic bacterial communities in the roots and shoots of the two plants were quite different, although most bacteria belonged to Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. A total of 68 endophytic bacterial strains were isolated from different tissues of the two plants and classified into three phyla: Firmicutes, Proteobacteria and Bacteroidetes. In both plants, Bacillus spp. and Pseudomonas spp. were the dominant cultivable populations. With an increase in the PAH pollution level, the diversity and distribution of endophytic bacteria in the two plants changed correspondingly, and the number of cultivable endophytic bacterial strains decreased rapidly. Testing of the isolated endophytic bacteria for tolerance to each type of PAH showed that most isolates could grow well on Luria-Bertani media in the presence of different PAHs, and some isolates were able to grow rapidly on a mineral salt medium with a single PAH as the sole carbon and energy source, indicating that these strains may have the potential to degrade PAHs in plants. This research provides the first insight into the characteristics of endophytic bacterial populations under different PAH pollution levels and provides a species resource for the isolation of PAH-degrading endophytic bacteria.     

甘南高寒地区不同海拔西藏沙棘根瘤内生菌多样性

为了研究甘南高寒地区3个不同海拔西藏沙棘根瘤中内生菌的多样性,采用Illumina MiSeq高通量测序技术对3种不同海拔的西藏沙棘根瘤内生菌的菌群组成和多样性进行了分析。实验结果表明,3个不同海拔西藏沙棘根瘤中的内生菌主要包括6大门,分别为蓝藻门(Cyanobacteria),放线菌门(Actinobacteria),变形菌门(Proteobacteria),拟杆菌门(Bacteroidetes),梭杆菌门(Fusobacteria)和厚壁菌门(Firmicutes)。其中占主导地位的微生物是蓝藻门和放线菌门,蓝藻门在3个海拔的西藏沙棘根瘤中的丰度分别为68.1%,64.7%和66.0%,放线菌门在3个海拔的西藏沙棘根瘤中的丰度分别为28.6%,30.2%和29.5%。放线菌门弗兰克氏菌属(Frankia)为共同的优势菌属之一,在3个海拔的丰度分别为28.2%,29.8%和29.1%。3个不同海拔西藏沙棘根瘤中的内生菌除了能与沙棘共生固氮的弗兰克氏菌外,还存在其他的微生物群落,可能存在一些潜在的有价值的内生菌种资源。