Thermotolerant and thermophilic actinomycetes from soils of Mongolia desert steppe zone

In the actinomycete complexes of Mongolian desert soils, thermotolerant and thermophilic actinomycetes were found in high abundance, exceeding that of the mesophilic forms. Among the thermotolerant members of the order Actinomycetales, Streptomyces, Micromonospora, Actinomadura, and Streptosporangium species were most widespread in desert soils. Experiments with soil microcosms demonstrated that thermophilic actinomycetes in desert soils grew, developed, and formed mycelia of the length comparable to that of the mesophilic forms of actinomycetes. Molecular biological investigation of the samples of desert steppe soils by denaturing gradient gel electrophoresis (DGGE) and fluorescent in situ hybridization (FISH) revealed members of the phylum Actinobacteria. FISH analysis revealed that the biomass of the metabolically active mycelial actinobacteria in the prokaryotic community of Mongolian desert soils exceeded that of the unicellular Actinobacteria.     

Abundance of actinobacteria and production of geosmin and 2-methylisoborneol in Danish streams and fish ponds

Occurrence of the odours geosmin and 2-methylisoborneol (MIB) in freshwater environments indicates that odour-producing organisms are commonly occurring. In the present study, we assumed actinomycetes to be a major source of the odours. Seasonal concentrations of odours and abundance of Actinobacteria, which includes actinomycetes and other G+ and high GC bacteria, were determined in one oligotrophic and two eutrophic freshwater streams, as well as in aquacultures connected to these streams, in Denmark. Concentrations of geosmin and MIB ranged from 2 to 9 ng l(-1) and were lowest in the winter. Passage of stream water in the aquacultures increased the amount of geosmin and MIB by up to 55% and 110%, respectively. Densities of actinobacteria were determined by fluorescence in situ hybridization with catalyzed reporter deposition (CARD-FISH) technique and were found to make up from 4 to 38 x 10(7) cells l(-1), corresponding to 3-9% of the total bacterial populations. The lowest densities of actinobacteria occurred in the winter. Filamentous bacteria targeted by the FISH probe made up about 2.7-38% (average was 22%) of the actinobacteria and were expected to be actinomycetes. Combined microautoradiography and CARD-FISH demonstrated that 10-38% (incorporation of 3H-thymidine) and 41-65% (incorporation of 3H-leucine) of the actinobacteria were metabolically active. The proportion of active actinobacteria increased up to 2-fold during passage of stream water in the aquacultures, and up to 98% of the cells became active. Sequencing of 16S rRNA genes in 8 bacterial isolates with typical actinomycete morphology from the streams and ponds demonstrated that most of them belonged to the genus Streptomyces. The isolated actinomycetes produced geosmin at rates from 0.1 to 35 aggeosmin bacterium(-1)h(-1). MIB was produced at similar rates in 5 isolates, whereas no MIB was produced by three of the isolates. Addition of the odours to stream water demonstrated that indigenous stream bacteria were capable of reducing the odours, and that enrichment with LB medium stimulated the degradation. Our study shows that bacterial communities in freshwater include geosmin- and MIB-producing actinobacteria. However, the mechanisms controlling production as well as degradation of the odours in natural waters appear complex and require further research.     

Specificity of the chitinolytic microbial complex of soils incubated at different temperatures

The structural and functional specificity of the chitinolytic microbial complex changes dramatically depending on the incubation temperature of soil microcosms. It was shown that the highest rates of chitin degradation occurred in desert soils at high temperatures (50°C); in the moderate and northern zones, these rates peaked at lower temperatures (5°C). The role of prokaryotes as the main chitin degraders in soils incubated at high temperatures, with fungi more actively participating in chitin decomposition at low temperatures, was shown for the first time. Fluorescent in situ hybridization (FISH) revealed the predominance of actinomycetes in the metabolically active chitinolytic prokaryotic complex of desert soils (high temperatures); in the soils of the northern latitudes (low temperatures), proteobacteria prevailed. The relationship between the taxonomic position of the dominant members of the chitinolytic complex of soil microorganisms, isolated in pure cultures with the dominant phylogenetic groups and the sequence types obtained by using molecular biological techniques (FISH) was revealed.     

可培养海洋放线菌生物多样性的研究进展

海洋放线菌是新药开发和天然活性产物的重要来源,海洋放线菌的生物多样性是代谢产物功能多样性的基础,因此研究可培养放线菌的生物多样性具有重要的意义。综述了近年来可培养的海洋放线菌生物多样性的研究进展,尤其是海绵共附生放线菌、深海放线菌和海洋固有放线菌的研究进展,对可培养的海洋放线菌的分离培养方法,包括样品处理、培养基的选择等进行了重点介绍,并对未培养海洋放线菌的分离培养进行了探讨,强调了建立区域性海洋放线菌菌种及基因资源库的重要性。     

抗菌活性放线菌的界面微滴移液互作分离筛选方法

[背景]放线菌是天然产物的宝库,目前应用于临床的天然抗生素有70％来源于放线菌的次级代谢产物.随着细菌对传统抗生素耐药问题的日趋严重,如何从自然生境中高效筛选新型活性放线菌资源并发现新型抗生素成为当前微生物学者面临的重要挑战.通过传统方法筛选活性放线菌不仅费时费力、试剂耗材消耗量大,并且筛选通量非常有限,难以对自然样品...     

海南西海岸真红树内生放线菌多样性及其延缓衰老活性初筛

为了发掘红树林内生放线菌资源和进行新型海洋药物研究,该文选择海南西海岸14种真红树的根、茎、叶、花、胚轴为研究对象,采用9种不同分离培养基[改良的高氏培养基(AGG)、海藻糖-天冬酰胺培养基(M4)、海藻糖-脯氨酸培养基(M5)、改良ISP5培养基(M7)、精氨酸-天冬酰胺培养基(M9)、改良淀粉-水解酪素培养基(M10)、酪氨酸-天冬酰胺培养基(P7)、燕麦培养基(P3)、棉籽糖-组氨酸培养基(M11)],结合稀释涂布法和三线划线法从真红树组织中分离菌株,基于菌株16S rRNA基因序列信息等分子生物学鉴定方法对获得的海洋放线菌进行多样性分析,并使用模式生物秀丽隐杆线虫对所得内生放线菌的延缓衰老活性进行研究。结果表明:(1)从46份真红树组织中共获得24株放线菌,隶属于7科11属,其中9株菌株为链霉菌属(Streptomyces),且IMDGX 6270、IMDGX 6137和IMDGX 6173为3株疑似潜在新菌株。(2)秀丽隐杆线虫模型筛选发现4株放线菌(IMDGX 6157、IMDGX 6182、IMDGX 6248、IMDGX 6360)具有延缓衰老的活性,与空白组比较,生存时间分别延长17.16%、28.11%、29.05%、27.10%。综上结果说明海南西海岸区域真红树植物中可能含有较丰富的放线菌资源,能够为延缓衰老药物的研发提供新来源。     

波罗的海放线菌的多样性

摘要:【目的】为了探索海洋放线菌的多样性,为发现新的药物先导化合物提供新菌源,我们分析了波罗的海的放线菌多样性及生物活性。【方法】采集100 份底泥样品,用7 种培养基分离放线菌809 株;去掉相同菌株后,选择280 株代表菌进行了初步分类鉴定;采用琼脂扩散法,检测了它们对5 种细菌、真菌的抗菌活性;用API ZYM system 测定了21 种酶的活性。【结果】用海藻糖-脯氨酸培养基和HV 培养基分离的放线菌中,稀有放线菌占60% 和63% ;波罗的海的放线菌有15 个属,其中3 个属是首次从海洋中分离     

Phylogenetic analysis of the genus Microbacterium based on 16S rRNA gene sequences

Abstract 16S rRNA gene (rDNA) studies of the six species of the genus Microbacterium, M. lacticum, M. laevaniformans, M. dextranolyticum, M. imperiale, M. arborescens and M. aurum , were performed and the primary structures were compared with those of 29 representative actinobacteria and related organisms. Phylogenetic analysis indicated that six species of the genus Microbacterium and representative four species of the genus Aureobacterium appear to be phylogenetically coherent as was suggested by Rainey et al., although the peptidoglycan types of these two genera are different (peptidoglycan type B1 or B2). Thus, the phylogenetical analyses revealed that members of actinobacteria with group B-peptidoglycan do not cluster according to their peptidoglycan types, but form compact cluster different from actinobacteria or actinomycetes with group A-peptidoglycan.     

Aerobic biodegradation of biphenyl and polychlorinated biphenyls by Arctic soil microorganisms.

We examined the degradation of biphenyl and the commercial polychlorinated biphenyl (PCB) mixture Aroclor 1221 by indigenous Arctic soil microorganisms to assess both the response of the soil microflora to PCB pollution and the potential of the microflora for bioremediation. In soil slurries, Arctic soil microflora and temperate-soil microflora had similar potentials to mineralize [14C]biphenyl. Mineralization began sooner and was more extensive in slurries of PCB-contaminated Arctic soils than in slurries of uncontaminated Arctic soils. The maximum mineralization rates at 30 and 7 degrees C were typically 1.2 to 1.4 and 0.52 to 1.0 mg of biphenyl g of dry soil-1 day-1, respectively. Slurries of PCB-contaminated Arctic soils degraded Aroclor 1221 more extensively at 30 degrees C (71 to 76% removal) than at 7 degrees C (14 to 40% removal). We isolated from Arctic soils organisms that were capable of psychrotolerant (growing at 7 to 30 degrees C) or psychrophilic (growing at 7 to 15 degrees C) growth on biphenyl. Two psychrotolerant isolates extensively degraded Aroclor 1221 at 7 degrees C (54 to 60% removal). The soil microflora and psychrotolerant isolates degraded all mono-, most di-, and some trichlorobiphenyl congeners. The results suggest that PCB pollution selected for biphenyl-mineralizing microorganisms in Arctic soils. While low temperatures severely limited Aroclor 1221 removal in slurries of Arctic soils, results with pure cultures suggest that more effective PCB biodegradation is possible under appropriate conditions.     

Antagonistic activity of soil acidophilic actinomycetes

It has been shown that soil acidophilic actinomycetes (mycelial prokaryotes with a growth optinum between pH 3 and 7) markedly differ from neutrophilic actinomycetes in antimicrobial activity: the former are more active against fungi and yeasts, whereas the latter effectively suppress Gram-positive bacteria. Acidophilic streptomycetes actively inhibit the growth of phytopathogenic fungi, especially on acidic media.     

Isolation and Characterization of Novel Marine-Derived Actinomycete Taxa Rich in Bioactive Metabolites

A unique selective enrichment procedure has resulted in the isolation and identification of two new genera of marine-derived actinobacteria. Approximately 90% of the microorganisms cultured by using the presented method were from the prospective new genera, a result indicative of its high selectivity. In this study, 102 actinomycetes were isolated from subtidal marine sediments collected from the Bismarck Sea and the Solomon Sea off the coast of Papua New Guinea. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rRNA gene sequences, and phylogenetic analysis based on 16S rRNA genes provided strong evidence for the two new genera (represented by strains of the PNG1 clade and strain UMM518) within the family Micromonosporaceae. Biological activity testing of fermentation products from the new marine-derived actinomycetes revealed that several had activities against multidrug-resistant gram-positive pathogens, malignant cells, and vaccinia virus replication.     

Isolation and characterization of novel marine-derived actinomycete taxa rich in bioactive metabolites

A unique selective enrichment procedure has resulted in the isolation and identification of two new genera of marine-derived actinobacteria. Approximately 90% of the microorganisms cultured by using the presented method were from the prospective new genera, a result indicative of its high selectivity. In this study, 102 actinomycetes were isolated from subtidal marine sediments collected from the Bismarck Sea and the Solomon Sea off the coast of Papua New Guinea. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rRNA gene sequences, and phylogenetic analysis based on 16S rRNA genes provided strong evidence for the two new genera (represented by strains of the PNG1 clade and strain UMM518) within the family Micromonosporaceae. Biological activity testing of fermentation products from the new marine-derived actinomycetes revealed that several had activities against multidrug-resistant gram-positive pathogens, malignant cells, and vaccinia virus replication.     

Sensitivity of Various Bacteria, Including Actinomycetes, and Fungi to Cadmium and the Influence of pH on Sensitivity

A variety of microorganisms, including gram-negative and gram-positive eubacteria, actinomycetes, yeasts, and filamentous fungi, were tested for their sensitivity to cadmium (Cd). In general, the actinomycetes were more tolerant to Cd than were the eubacteria; gram-negative eubacteria were more tolerant to Cd than were gram-positive eubacteria. The period of exponential growth of the eubacteria and actinomycetes was extended in the presence of Cd. Wide extremes in sensitivity to Cd were noted among the fungi; there was no correlation between the class of fungus and tolerance to Cd. Fungal sporulation was more sensitive to Cd than was mycelial growth, as spore formation was inhibited at Cd concentrations that were noninhibitory to mycelial proliferation. The toxicity of Cd to the eubacteria, actinomycetes, and fungi appeared to be pH dependent, as toxicity was generally potentiated at pH 8 or 9.     

The evolution of development in Streptomyces analysed by genome comparisons

There is considerable information about the genetic control of the processes by which mycelial Streptomyces bacteria form spore-bearing aerial hyphae. The recent acquisition of genome sequences for 16 species of actinobacteria, including two streptomycetes, makes it possible to try to reconstruct the evolution of Streptomyces differentiation by a comparative genomic approach, and to place the results in the context of current views on the evolution of bacteria. Most of the developmental genes evaluated are found only in actinobacteria that form sporulating aerial hyphae, with several being peculiar to streptomycetes. Only four (whiA, whiB, whiD, crgA) are generally present in nondifferentiating actinobacteria, and only two (whiA, whiG) are found in other bacteria, where they are widespread. Thus, the evolution of Streptomyces development has probably involved the stepwise acquisition of laterally transferred DNA, each successive acquisition giving rise either to regulatory changes that affect the conditions under which development is initiated, or to changes in cellular structure or morphology.     

The influence of germinating seeds and developing roots on re-establishment of micro-organisms in fumigated soil

A laboratory study was made of re-invasion of soils fumigated in closed containers at rates of 3 ml./sq.ft. 10 in. deep with chloropicrin, methyl bromide and a 67:33 mixture of the two materials (MBC–33), using the dilution plate method of determination. Counts after aeration, 3 weeks later, showed that all three fumigants eliminated practically all fungi. Chloropicrin and MBC–33 also killed almost all bacteria and actinomycetes, whereas fumigation with methyl bromide markedly increased numbers of bacteria without materially altering numbers of actinomycetes. Subsequently, in soils fumigated with chloropicrin or MBC–33, fungi recolonized rapidly, but up to 93 % of the colonies isolated were Trichoderma viride. Increase of fungi in soils fumigated with methyl bromide was slower and Penicillium spp. predominated. Bacteria at first declined in numbers, then increased rapidly in soils fumigated with all three materials. In soils fumigated with methyl bromide, actinomycetes, usually considered to include good antagonists, increased but did not exploit their initial advantage over fungi. In soils fumigated with chloropicrin and MBC–33 actinomycetes did not recolonize in appreciable numbers. The greatest variety of fungous genera occurred in isolates from rhizo-spheres of red beet, but the greatest numbers of colonies of both fungi and bacteria were isolated from rhizospheres of pea and pumpkin. None of the crops tested greatly stimulated recolonization by actinomycetes. Compared with the drastic changes brought about by fumigants the influence of seed and root exudates on either the magnitude or the composition of re-invading micro-organisms was slight.     

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.     

Unlocking Streptomyces spp. for use as sustainable industrial production platforms by morphological engineering

Filamentous actinomycetes are commercially widely used as producers of natural products (in particular antibiotics) and of industrial enzymes. However, the mycelial lifestyle of actinomycetes, resulting in highly viscous broths and unfavorable pellet formation, has been a major bottleneck in their commercialization. Here we describe the successful morphological engineering of industrially important streptomycetes through controlled expression of the morphogene ssgA. This led to improved growth of many industrial and reference streptomycetes, with fragmentation of the mycelial clumps resulting in significantly enhanced growth rates in batch fermentations of Streptomyces coelicolor and Streptomyces lividans. Product formation was also stimulated, with a twofold increase in yield of enzyme production by S. lividans. We anticipate that the use of the presented methodology will make actinomycetes significantly more attractive as industrial and sustainable production hosts.     

Soil actinobacteria tend to have neutral interactions with other co-occurring microorganisms,especially under oligotrophic conditions

Actinobacteria produce a variety of secondary metabolites that can influence the survival or behaviour of other organisms. The understanding of the ecological roles of actinobacteria has significantly improved in the past decades, but a systematic insight into the interactions between actinobacteria and other microbes in nature is warranted. Here, we studied the pairwise effects of actinobacteria on other microbes isolated from red soils under different nutritional conditions. We found that neutral effects dominated the interactions, accounting for 68.1% of the interactions in eutrophic conditions and for a significantly higher proportion (86.2%) in oligotrophic conditions. High nutrient levels boosted active metabolism of actinobacteria and generally made them more aggressive, supporting the stress gradient hypothesis. The secondary metabolites produced by actinobacteria played a pivotal role in interference competition with other microbes, of which the role of desferrioxamine siderophores could not be ignored. Niche overlap seemed to be another cause of competition, notably under oligotrophic conditions. Moreover, the large-scale phylogeny had a much greater impact on the interaction than the location origin of the microbes. These results provide an understanding of the coexistence of actinobacteria with other microbes in nature and suggest neutrality as a key mechanism for maintaining microbial diversity in soils.     

Description of the phylogenetic structure of hydrolytic prokaryotic complex in the soils

With the help of the molecular-biological method of cell hybridization in situ (FISH), the abundance of a physiologically active hydrolytic prokaryotic complex in chernozem and gley-podzolic soils is determined. The total proportion of metabolically active cells, which were detected by hybridization with universal probes as representatives of the domains Bacteria and Archaea, in samples of the studied soil, was from 38% for chernozem up to 78% for gley-podzolic soil of the total number of cells. The differences in the structure of chitinolytic and pectinolytic prokaryotic soil complexes are detected. Along with the high abundance of Actinobacteria and Firmicutes in the soils with chitin, an increase in phylogenetic groups such as Alphaproteobacteria and Bacteroidetes is observed.