Molecular Phylogeny and Diversity of the Salt-Tolerant Alkaliphilic Actinobacteria Inhabiting Coastal Gujarat,India

Actinobacteria is a dominant phylum in saline soil and play important roles in the process of organic matter decomposition and biogeochemical cycling. In this study, we investigated the diversity and phylogeny of the haloalkaliphilic actinobacteria that inhabited the saline soil of Coastal Gujarat (India) using conventional and molecular approaches. The actinobacteria were diversified on the basis of their growth patterns, morphology, spore color and sugar utilization. The cultivated actinobacteria were genetically diverse, with the ability to grow at high salt concentrations. The salt resistance feature was widely distributed among the isolates and not confined to any particular phylogenetic cluster. The PCR -DGGE approach was used to assess molecular diversity and to mitigate the limitation of the 16S rRNA sequence approach. Reproducible band profiles confirmed that the PCR-DGGE provided an excellent tool for the 16S rDNA heterogeneity analysis. The migration behavior of the 16S rRNA genes on the DGGE gel suggested lack of correlation between the band numbers and α-diversity. The findings highlighted the trends associated with the microbial community and signify the role of the DGGE in distinguishing a group of species that exhibit 16S rRNA based phylogenetic relatedness with distinct phenotypic characters. Based on the 16S rRNA genes, the actinobacteria were identified as belong to Nocardiopsis, Brachybacterium, Streptomyces and Prauseria. Nocardiopsis was the most predominant actinobacterial genera. The study indicated that a combination of the conventional and molecular approaches could be highly significant in analyzing the diversity of the actinobacteria from the saline habitat.     

新疆红井子盐碱土壤非培养放线菌多样性

【目的】研究新疆红井子盐碱土壤中的放线菌物种多样性。【方法】应用基于16S rRNA基因序列系统发育分析的免培养方法进行放线菌物种多样性分析。利用放线菌特异性引物,以土壤样品总DNA为模板,扩增16S rRNA基因,构建16S rRNA基因克隆文库,并对文库中的插入序列进行RFLP分析。【结果】随机挑选的246个阳性克隆通过酶切筛选出61个不同图谱的重组克隆并测序。分析结果显示这61个克隆序列分属于42个OTUs,分布于放线菌纲(Actinobacteria)的放线菌亚纲(Actinobacteridae)、酸微菌亚纲(Acidimicrobidae)和红色杆菌亚纲(Rubrobacteridae);该环境中有71.4%的序列与已有效发表菌株的序列相似性小于97%,代表着放线菌新类群,其中部分序列形成了几个独立的进化分支,可能代表更高级的新分类单元。【结论】红井子土壤中的放线菌组成具有丰富的多样性,并有新放线菌分类单位的潜在资源,值得进一步进行开发研究。     

澄黄滨珊瑚和丛生盔型珊瑚非培养放线菌多样性

【目的】研究澄黄滨珊瑚(Porites lutea)和丛生盔型珊瑚(Galaxea fascicularis)联合放线菌物种多样性。【方法】实验提取两种珊瑚的总DNA,利用放线菌特异性引物对样品总DNA进行扩增,通过构建16S rRNA基因克隆文库和系统发育分析,对三亚鹿回头岸礁区优势物种澄黄滨珊瑚和丛生盔型珊瑚联合放线菌的多样性和群落结构进行研究。【结果】118个从澄黄滨珊瑚克隆文库中随机挑选的阳性克隆子归为58个OTUs,主要分布于酸微菌亚目、棒状杆菌亚目、微球菌亚目、丙酸杆菌亚目和未知类群。丛生盔型珊瑚克隆文库共获得96个序列,归为31个OTUs,主要分布于酸微菌亚目和未知的放线菌类群。多样性指数和稀疏度曲线分析结果显示澄黄滨珊瑚联合放线菌物种多样性比丛生盔型珊瑚更高。【结论】澄黄滨珊瑚和丛生盔型珊瑚拥有较高水平的放线菌物种多样性和复杂的群落结构,并隐藏着大量的高等级放线菌新分类单元。     

南海深海沉积物放线菌多样性分析

【目的】免培养和纯培养相结合分析南海深海沉积物放线菌多样性。【方法】免培养方法通过提取沉积物宏基因组DNA,利用放线菌门特异性引物扩增放线菌16S r RNA基因序列,构建放线菌16S r RNA基因克隆文库,文库经RFLP(Restriction fragment length polymorphism)分析后挑选代表序列测序并进行多样性指数分析和系统发育分析。可培养方法利用8种培养基进行菌株分离,对排重后的菌株进行16S r RNA基因序列多样性分析。【结果】构建的两个深海位点的16S r RNA基因克隆文库在放线菌门的放线菌纲(Actinobacteria)、酸微菌纲(Acidimicrobiia)、腈基降解菌纲(Nitriliruptoria)和嗜热油菌纲(Thermoleophilia)4个纲中均有分布;两个位点中的种群结构有差异,N40-4位点的优势种群是放线菌纲的链霉菌目(Streptomycetales);N63-4位点的优势种群是腈基降解菌纲的腈基降解菌目(Nitriliruptorales)。8种培养基共分离出41株放线菌,根据形态特征排重后得到的19株菌分布于10个不同的属,12个不同的种,其中稀有放线菌属比例较高,菌株OAct400为潜在的微杆菌属(Microbacterium)新种。【结论】南海深海沉积物蕴含着丰富的放线菌物种资源及大量未知种群,具有进一步研究的价值。     

Variability of Actinobacteria, a minor component of rumen microflora

Actinobacteria (Actinomycetes) are a significant and interesting group of gram-positive bacteria. They are regular, though infrequent, members of the microbial life in the rumen and represent up to 3 % of total rumen bacteria; there is considerable lack of information about ecology and biology of rumen actinobacteria. During the characterization of variability of rumen treponemas using non-cultivation approach, we also noted the variability of rumen actinobacteria. By using Treponema-specific primers a specific 16S rRNA gene library was prepared from cow and sheep rumen total DNA. About 10 % of recombinant clones contained actinobacteria-like sequences. Phylogenetic analyses of 11 clones obtained showed the high variability of actinobacteria in the ruminant digestive system. While some sequences are nearly identical to known sequences of actinobacteria, we detected completely new clusters of actinobacteria-like sequences, representing probably new, as yet undiscovered, group of rumen Actinobacteria. Further research will be necessary for understanding their nature and functions in the rumen.     

Marine actinobacteria associated with marine organisms and their potentials in producing pharmaceutical natural products

Actinobacteria are ubiquitous in the marine environment, playing an important ecological role in the recycling of refractory biomaterials and producing novel natural products with pharmic applications. Actinobacteria have been detected or isolated from the marine creatures such as sponges, corals, mollusks, ascidians, seaweeds, and seagrass. Marine organism-associated actinobacterial 16S rRNA gene sequences, i.e., 3,003 sequences, deposited in the NCBI database clearly revealed enormous numbers of actinobacteria associated with marine organisms. For example, RDP classification of these sequences showed that 112 and 62 actinobacterial genera were associated with the sponges and corals, respectively. In most cases, it is expected that these actinobacteria protect the host against pathogens by producing bioactive compounds. Natural products investigation and functional gene screening of the actinobacteria associated with the marine organisms revealed that they can synthesize numerous natural products including polyketides, isoprenoids, phenazines, peptides, indolocarbazoles, sterols, and others. These compounds showed anticancer, antimicrobial, antiparasitic, neurological, antioxidant, and anti-HIV activities. Therefore, marine organism-associated actinobacteria represent an important resource for marine drugs. It is an upcoming field of research to search for novel actinobacteria and pharmaceutical natural products from actinobacteria associated with the marine organisms. In this review, we attempt to summarize the present knowledge on the diversity and natural products production of actinobacteria associated with the marine organisms, based on the publications from 1991 to 2013.     

Diversity of bacterial endophytes in roots of Mexican husk tomato plants (Physalis ixocarpa) and their detection in the rhizosphere

Endophytic bacterial diversity was estimated in Mexican husk tomato plant roots by amplified rDNA restriction analysis and sequence homology comparison of the 16S rDNA genes. Sixteen operational taxonomic units from the 16S rDNA root library were identified based on sequence analysis, including the classes Gammaproteobacteria, Betaproteobacteria, Actinobacteria, and Bacilli. The predominant genera were Stenotrophomonas (21.9%), Microbacterium (17.1%), Burkholderia (14.3%), Bacillus (14.3%), and Pseudomonas (10.5%). In a 16S rDNA gene library of the same plant species' rhizosphere, only common soil bacteria, including Stenotrophomonas, Burkholderia, Bacillus, and Pseudomonas, were detected. We suggest that the endophytic bacterial diversity within the roots of Mexican husk tomato plants is a subset of the rhizosphere bacterial population, dominated by a few genera.     

Diversity of culturable actinobacteria isolated from marine sponge <Emphasis Type="Italic">Haliclona</Emphasis> sp.

This study describes actinobacteria isolated from the marine sponge Haliclona sp. collected in shallow water of the South China Sea. A total of 54 actinobacteria were isolated using media selective for actinobacteria. Species diversity and natural product diversity of isolates from marine sponge Haliclona sp. were analysed. Twenty-four isolates were selected on the basis of their morphology on different media and assigned to the phylum Actinobacteria by a combination of 16S rRNA gene based restriction enzymes digestion and 16S rRNA gene sequence analysis. The 16S rRNA genes of 24 isolates were digested by restriction enzymes TaqI and MspI and assigned to different groups according to their restriction enzyme pattern. The phylogenetic analysis based on 16S rRNA gene sequencing showed that the isolates belonged to the genera Streptomyces, Nocardiopsis, Micromonospora and Verrucosispora; one other isolate was recovered that does not belong to known genera based on its unique 16S rRNA gene sequence. To our knowledge, this is the first report of a bacterium classified as Verrucosispora sp. that has been isolated from a marine sponge. The majority of the strains tested belong to the genus Streptomyces and three isolates may be new species. All of the 24 isolates were screened for genes encoding polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS). PKS and NRPS sequences were detected in more than half of the isolates and the different "PKS-I-PKS-II-NRPS" combinations in different isolates belonging to the same species are indicators of their potential natural product diversity and divergent genetic evolution.     

The rhizospheres of traditional medicinal plants in Panxi, China, host a diverse selection of actinobacteria with antimicrobial properties

Actinobacteria are a prolific source of antibiotics. Since the rate of discovery of novel antibiotics is decreasing, actinobacteria from unique environments need to be explored. In particular, actinobacterial biocontrol strains from medicinal plants need to be studied as they can be a source of potent antibiotics. We combined culture-dependent and culture-independent methods in analyzing the actinobacterial diversity in the rhizosphere of seven traditional medicinal plant species from Panxi, China, and assessed the antimicrobial activity of the isolates. Each of the plant species hosted a unique set of actinobacterial strains. Out of the 64 morphologically distinct isolates, half were Streptomyces sp., eight were Micromonospora sp., and the rest were members of 18 actinobacterial genera. In particular, Ainsliaea henryi Diels. hosted a diverse selection of actinobacteria, although the 16S ribosomal RNA (rRNA) sequence identity ranges of the isolates and of the 16S rRNA gene clone library were not congruent. In the clone library, 40% of the sequences were related to uncultured actinobacteria, emphasizing the need to develop isolation methods to assess the full potential of the actinobacteria. All Streptomyces isolates showed antimicrobial activity. While the antimicrobial activities of the rare actinobacteria were limited, the growth of Escherichia coli, Verticillium dahliae, and Fusarium oxysporum were inhibited only by rare actinobacteria, and strains related to Saccharopolyspora shandongensis and Streptosporangium roseum showed broad antimicrobial activity.     

Isolation and identification of actinobacteria from surface-sterilized wheat roots

This is the first report of filamentous actinobacteria isolated from surface-sterilized root tissues of healthy wheat plants (Triticum aestivum L.). Wheat roots from a range of sites across South Australia were used as the source material for the isolation of the endophytic actinobacteria. Roots were surface-sterilized by using ethanol and sodium hypochlorite prior to the isolation of the actinobacteria. Forty-nine of these isolates were identified by using 16S ribosomal DNA (rDNA) sequencing and found to belong to a small group of actinobacterial genera including Streptomyces, Microbispora, Micromonospora, and Nocardiodes spp. Many of the Streptomyces spp. were found to be similar, on the basis of their 16S rDNA gene sequence, to Streptomyces spp. that had been isolated from potato scabs. In particular, several isolates exhibited high 16S rDNA gene sequence homology to Streptomyces caviscabies and S. setonii. None of these isolates, nor the S. caviscabies and S. setonii type strains, were found to carry the nec1 pathogenicity-associated gene or to produce the toxin thaxtomin, indicating that they were nonpathogenic. These isolates were recovered from healthy plants over a range of geographically and temporally isolated sampling events and constitute an important plant-microbe interaction.     

Development of PCR primers specific for the amplification and direct sequencing of gyrB genes from microbacteria, order Actinomycetales

PCR primer sets were developed for the specific amplification and sequence analyses encoding the gyrase subunit B (gyrB) of members of the family Microbacteriaceae, class Actinobacteria. The family contains species highly related by 16S rRNA gene sequence analyses. In order to test if the gene sequence analysis of gyrB is appropriate to discriminate between closely related species, we evaluate the 16S rRNA gene phylogeny of its members. As the published universal primer set for gyrB failed to amplify the responding gene of the majority of the 80 type strains of the family, three new primer sets were identified that generated fragments with a composite sequence length of about 900 nt. However, the amplification of all three fragments was successful only in 25% of the 80 type strains. In this study, the substitution frequencies in genes encoding gyrase and 16S rDNA were compared for 10 strains of nine genera. The frequency of gyrB nucleotide substitution is significantly higher than that of the 16S rDNA, and no linear correlation exists between the similarities of both molecules among members of the Microbacteriaceae. The phylogenetic analyses using the gyrB sequences provide higher resolution than using 16S rDNA sequences and seem able to discriminate between closely related species.     

Phylogenetic analysis of the fecal flora of the wild pygmy loris

The bacterial diversity in fecal samples from the wild pygmy loris was examined with a 16S rDNA clone library and restriction fragment length polymorphism analysis. The clones were classified as Firmicutes (43.1%), Proteobacteria (34.5%), Actinobacteria (5.2%), and Bacteroidetes (17.2%). The 58 different kinds of 16S rDNA sequences were classified into 16 genera and 20 uncultured bacteria. According to phylogenetic analysis, the major genera within the Proteobacteria was Pseudomonas, comprising 13.79% of the analyzed clone sequences. Many of the isolated rDNA sequences did not correspond to known microorganisms, but had high homology to uncultured clones found in human feces. Am. J. Primatol. 72:699–706, 2010. © 2010 Wiley‐Liss, Inc.     

Microbial diversity in hot synthetic compost as revealed by PCR-amplified rRNA sequences from cultivated isolates and extracted DNA

High-temperature (>/=60 degrees C) synthetic food waste compost was examined by cultivation-dependent and -independent methods to determine predominant microbial populations. Fluorescent direct counts totaled 6.4 (+/-2.5)x10(10) cells gdw(-1) in a freeze-dried 74 degrees C compost sample, while plate counts for thermophilic heterotrophic aerobes averaged 2.6 (+/-1.0)x10(8) CFU gdw(-1). A pre-lysis cell fractionation method was developed to obtain community DNA and a suite of 16S and 18S rDNA-targeted PCR primers was used to examine the presence of Bacteria, Archaea and fungi. Bacterial 16S rDNA, including a domain-specific 1500-bp fragment and a 300-bp fragment specific for Actinobacteria, was amplified by PCR from all compost samples tested. Archaeal rDNA was not amplified in any sample. Fungal 18S rDNA was only amplified from a separate dairy manure compost that reached a peak temperature of 50 degrees C. Amplified rDNA restriction analysis (ARDRA) was used to screen isolated thermophilic bacteria and a clone library of full-length rDNA fragments. ARDRA screening revealed 14 unique patterns among 63 isolates, with one pattern accounting for 31 of the isolates. In the clone library, 52 unique patterns were detected among 70 clones, indicating high diversity of uncultivated bacteria in hot compost. Phylogenetic analysis revealed that the two most abundant isolates belonged in the genera Aneurinibacillus and Brevibacillus, which are not commonly associated with hot compost. With the exception of one Lactobacillus-type sequence, the clone library contained only sequences that clustered within the genus Bacillus. None of the isolates or cloned sequences could be assigned to the group of obligate thermophilic Bacillus spp. represented by B. stearothermophilus, commonly believed to dominate high-temperature compost. Amplified partial fragments from Actinobacteria, spanning the V3 variable region (Neefs et al. (1990) Nucleic Acids Res. 18, 2237-2242), included sequences related to the genera Saccharomonospora, Gordonia, Rhodococcus and Corynebacterium, although none of these organisms were detected among the isolates or full-length cloned rDNA sequences. All of the thermophilic isolates and sequenced rDNA fragments examined in this study were from Gram-positive organisms.     

Phylogenetic diversity and investigation of plant growth-promoting traits of actinobacteria in coastal salt marsh plant rhizospheres from Jiangsu,China

Actinobacteria from special habitats are of interest due to their producing of bioactive compounds and diverse ecological functions. However, little is known of the diversity and functional traits of actinobacteria inhabiting coastal salt marsh soils. We assessed actinobacterial diversity from eight coastal salt marsh rhizosphere soils from Jiangsu Province, China, using culture-based and 16S rRNA gene high throughput sequencing (HTS) methods, in addition to evaluating their plant growth-promoting (PGP) traits of isolates. Actinobacterial sequences represented 2.8%–43.0% of rhizosphere bacterial communities, as determined by HTS technique. The actinobacteria community comprised 34 families and 79 genera. In addition, 196 actinobacterial isolates were obtained, of which 92 representative isolates were selected for further 16S rRNA gene sequencing and phylogenetic analysis. The 92 strains comprised seven suborders, 12 families, and 20 genera that included several potential novel species. All representative strains were tested for their ability of producing indole acetic acid (IAA), siderophores, 1-aminocyclopropane-1-carboxylate deaminase (ACCD), hydrolytic enzymes, and phosphate solubilization. Based on the presence of multiple PGP traits, two strains, Streptomyces sp. KLBMP S0051 and Micromonospora sp. KLBMP S0019 were selected for inoculation of wheat seeds grown under salt stress. Both strains promoted seed germination, and KLBMP S0019 significantly enhanced seedling growth under NaCl stress. Our study demonstrates that coastal salt marsh rhizosphere soils harbor a diverse reservoir of actinobacteria that are potential resources for the discovery of novel species and functions. Moreover, several of the isolates identified here are good candidates as PGP bacteria that may contribute to plant adaptions to saline soils.     

新疆泥火山细菌遗传多样性

为了解新疆乌苏泥火山细菌多样性,从泥火山泥浆样品中直接提取总DNA,构建了含150个有效转化子的泥火山细菌16S rDNA基因文库,转化子经菌液PCR及HaeⅢ酶切后获得16个不同带型,克隆测序结果表明,其分属于16个不同的分类单元.一部分序列与已知细菌类群的16S rDNA序列相似性较高,归属变形菌门(Proteobacteria),厚壁菌门(Firmicutes),梭杆菌门(Fusobacteria),放线菌门(Actinobacteria);另外一部分序列与已知细菌类群的16S rDNA序列同源性较低,可能代表新的分类单位.研究结果显示,泥火山环境中微生物种群丰富,值得进一步研究.     

Bacteria in Weathered Basaltic Glass,Iceland

Bacteria play an important role in rock weathering and yet their diversity and potential activity in the terrestrial rock weathering environment is poorly understood. Culture and culture-independent methods (16S rDNA) were used to investigate the populations of bacteria inhabiting a basaltic glass/palagonite subglacial (hyaloclastite) deposit subject to weathering in Iceland. The rock hosts a diverse microbial community. The 16S rDNA clones were dominated by Actinobacteria, Proteobacteria, Bacteroidetes and Acidobacteria. Representatives of Gemmatimonadetes and Verrucomicrobia were present. Isolation of organisms on basalt/palagonite yielded only two isolates, an actinobacterium and a Bacteroidetes, showing that the active species, at least in the time scale of laboratory cultivation, are a small proportion of the total diversity. Firmicutes and Actinobacteria were isolated when basalt/palagonite was supplemented with an organic source. Many of the isolates demonstrated tolerance to transition metals (Cr, Cu, Zn, Ni, Co) naturally present in the rock. The growth of the isolates was inhibited at typical pH values for Icelandic rain, which suggests that the increase in pH caused by the consumption of protons in rock weathering, for example by palagonite formation, may play a role in defining which organisms are active. Colonization experiments show that the filamentous growth habit of the actinobacterium isolated on basalt/palagonite allows it to actively invade and colonise the basaltic glass. The filamentous growth of some actinobacteria may be an important contributor to their role in systemic interstitial rock weathering in the natural environment.     

Isolation and Identification of Actinobacteria from Surface-Sterilized Wheat Roots

This is the first report of filamentous actinobacteria isolated from surface-sterilized root tissues of healthy wheat plants (Triticum aestivum L.). Wheat roots from a range of sites across South Australia were used as the source material for the isolation of the endophytic actinobacteria. Roots were surface-sterilized by using ethanol and sodium hypochlorite prior to the isolation of the actinobacteria. Forty-nine of these isolates were identified by using 16S ribosomal DNA (rDNA) sequencing and found to belong to a small group of actinobacterial genera including Streptomyces, Microbispora, Micromonospora, and Nocardiodes spp. Many of the Streptomyces spp. were found to be similar, on the basis of their 16S rDNA gene sequence, to Streptomyces spp. that had been isolated from potato scabs. In particular, several isolates exhibited high 16S rDNA gene sequence homology to Streptomyces caviscabies and S. setonii. None of these isolates, nor the S. caviscabies and S. setonii type strains, were found to carry the nec1 pathogenicity-associated gene or to produce the toxin thaxtomin, indicating that they were nonpathogenic. These isolates were recovered from healthy plants over a range of geographically and temporally isolated sampling events and constitute an important plant-microbe interaction.     

Detection of Actinobacteria cultivated from environmental samples reveals bias in universal primers

AIMS: The aims of this study were to develop media to cultivate actinomycetes, screen the resulting isolates with Actinobacteria-specific primers, and examine the efficacy of detection of the actinobacterial isolates with universal primers. METHODS AND RESULTS: Soil-extract medium was developed for a terrestrial bluff environment. Recovered isolates were subjected to polymerase chain reaction (PCR) with taxon-specific primers to identify Actinobacteria. Universal bacterial primers 24f and 1492r (modified and original versions) were used to amplify the 16S rRNA gene from the putative Actinobacteria. While both reverse primers failed to provide amplification products from 20% to 50% of the isolates, the 1492r primer detected Actinobacteria more effectively than 1492r-mod. The region of the gene containing the annealing site for the 1492r primers from 15 isolates that failed to amplify showed no differences in nucleotide sequence to the original 1492r primer. CONCLUSIONS: Universal 16S rRNA gene primers are not capable of amplifying this gene from all bacteria within an environmental sample. Some Actinobacteria may share 100% sequence similarity to universal primers but remain undetected. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings are important for studies of particular taxa in environmental samples where reactions utilizing universal primers may not reveal the extent of their presence and diversity.     

毛竹根际可培养微生物种群多样性分析

[目的]为了了解天然毛竹林根际可培养微生物种群的多样性信息,[方法]采用稀释平板法,对浙江天目山和重庆缙云山天然毛竹林根际细菌和放线菌进行了分离,并对其16S rDNA序列进行了分析.[结果]分别从天目山和缙云山天然毛竹林根际分离得到51株和31株菌落形态差异的细菌和放线菌.16S rDNA序列分析表明,天目山和缙云山毛竹根际细菌主要包括厚壁菌门(Firmicutes,分别为40%和58%)、放线菌门(Actinobacteria,分别为36.7%和10.52%)、变形菌门-亚群(Alphaproteobacteria,分别为10%和5.26%)和变形菌门 --亚群(Gammaproteobacteria,分别为10%和26.32%),其中芽孢杆菌属(Bacillus sp.)为共同的优势菌属(分别为34.38%和42.11%).分离的菌株中,B188、B171和B152等6株与GenBank中已报道16S rRNA基因序列的相似性从90%到96%不等,可能代表着新属或种.[结论]这表明,天然毛竹林根际具有较为丰富的可培养微生物种群多样性,并存在一些潜在的新的微生物菌种资源.     

孟加拉虎粪便放线菌的分离及其多样性

【目的】建立有效分离动物粪便放线菌的方法,认识孟加拉虎粪便放线菌的多样性。【方法】从预处理、抑制剂、培养基三个方面考虑,采用平板稀释的分离方法。用细菌通用引物扩增获得放线菌菌株的16SrRNA基因,根据系统发育分析进行鉴定。【结果】孟加拉虎粪便样品中,可培养放线菌的菌落平均数量为1.10×108cfu/g(粪便湿重);对分离到的110株纯培养放线菌的16S rRNA基因部分序列分析表明:它们分布于10个科、12个属,主要是一些菌丝分化程度低的放线菌,如:Arthrobacter、Dietzia、Kocuria、Corynebacterium、Microbacterium等;产丝的放线菌主要以Streptomyces占优势,约占分离到放线菌总数的64%。【结论】干热处理粪便样品可以大大提高放线菌的出菌率;添加多种抑制剂及不含天然成分的组合培养基较适合粪便放线菌的分离;孟加拉虎粪便中可培养放线菌的多样性较丰富。本研究提供的分离动物粪便放线菌的有效方法,为动物粪便放线菌资源的研究和开发利用提供了借鉴作用。