Detection and quantitation of colored deposit-forming <Emphasis Type="Italic">Meiothermus</Emphasis> spp. in paper industry processes and end products

Colored biofilms cause problems in paper industry. In this work we used real-time PCR to detect and to quantitate members of the genus Meiothermus from the process samples and end products from 24 machines manufacturing pulp, paper and board in four countries. The results obtained from 200 samples showed the importance of members of the genus Meiothermus as ubiquitous biofoulers in paper machines. This genus was the dominant biofouler in some mills. From ≤10⁴ to 10¹¹ copies of Meiothermus 16S rRNA genes were found per gram of process deposit (wet weight). Meiothermus spp. were found in paper and board products with colored defects and connection between deposit-forming microbes and end-product spots was shown. 16S rRNA gene sequences of 29 biofilm producing bacterial isolates from different mills were determined. Based on sequence data, 25 of the isolates were assigned to the genus Meiothermus, with Meiothermus silvanus and M. ruber as the most frequent species.     

Diversity of bacteria contaminating paper machines

Formation of microbial biofilms and slimes is a general and serious problem in the operation of paper machines. Studies of microbial populations in paper machine-derived biofilms have been conducted using standard microbiological procedures; however, the bacterial genera present in this type of samples as well as their diversity are quite poorly known. Here, the bacterial diversity of 38 process water and 22 biofilm samples from four different Finnish paper machines were analyzed by length heterogeneity analysis of PCR-amplified 16S ribosomal DNA (LH-PCR). In addition, sequencing of the amplified 16S rRNA gene from 69 clones was conducted for characterization of the bacterial genera present in biofilm and slime samples. The LH-PCR profiles of both the free-living (process waters) and immobilized (biofilms) bacteria were diverse at all stages of the papermaking process. Out of the 69 sequenced clones, 44 belonged to alpha-Proteobacteria, most of which were close to the nitrogen-fixing root nodule genera Sinorhizobium, Rhizobium and Azorhizobium. Other clones were assigned to beta- and gamma-Proteobacteria and the phylum Bacteroidetes. In addition, eight of the clones were assigned to a yet uncultivated phylum, TM7. Finally, epifluorescence microscopy revealed that Gram-negative bacteria were predominant in both the biofilm (65%) and process water (54%) samples and a small coccoid cell morphology was most common in all samples. Together, our results show that the analysis of microbial samples from paper machines using modern molecular biology techniques adds valuable information and should, therefore, be useful as a more specific and sensitive microbiological method for the paper industry. This information could further be applied, e.g., in the development of more specific and environmental friendly antimicrobial agents for paper mills.     

Spatial and successional dynamics of microbial biofilm communities in a grassland stream ecosystem

Biofilms represent a metabolically active and structurally complex component of freshwater ecosystems. Ephemeral prairie streams are hydrologically harsh and prone to frequent perturbation. Elucidating both functional and structural community changes over time within prairie streams provides a general understanding of microbial responses to environmental disturbance. We examined microbial succession of biofilm communities at three sites in a third‐order stream at Konza Prairie over a 2‐ to 64‐day period. Microbial abundance (bacterial abundance, chlorophyll a concentrations) increased and never plateaued during the experiment. Net primary productivity (net balance of oxygen consumption and production) of the developing biofilms did not differ statistically from zero until 64 days suggesting a balance of the use of autochthonous and allochthonous energy sources until late succession. Bacterial communities (MiSeq analyses of the V4 region of 16S rRNA) established quickly. Bacterial richness, diversity and evenness were high after 2 days and increased over time. Several dominant bacterial phyla (Beta‐, Alphaproteobacteria, Bacteroidetes, Gemmatimonadetes, Acidobacteria, Chloroflexi) and genera (Luteolibacter, Flavobacterium, Gemmatimonas, Hydrogenophaga) differed in relative abundance over space and time. Bacterial community composition differed across both space and successional time. Pairwise comparisons of phylogenetic turnover in bacterial community composition indicated that early‐stage succession (≤16 days) was driven by stochastic processes, whereas later stages were driven by deterministic selection regardless of site. Our data suggest that microbial biofilms predictably develop both functionally and structurally indicating distinct successional trajectories of bacterial communities in this ecosystem.     

Endophytic bacterial diversity in grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) leaves described by 16S rRNA gene sequence analysis and length heterogeneity-PCR

Diversity of bacterial endophytes associated with grapevine leaf tissues was analyzed by cultivation and cultivation-independent methods. In order to identify bacterial endophytes directly from metagenome, a protocol for bacteria enrichment and DNA extraction was optimized. Sequence analysis of 16S rRNA gene libraries underscored five diverse Operational Taxonomic Units (OTUs), showing best sequence matches with γ-Proteobacteria, family Enterobacteriaceae, with a dominance of the genus Pantoea. Bacteria isolation through cultivation revealed the presence of six OTUs, showing best sequence matches with Actinobacteria, genus Curtobacterium, and with Firmicutes genera Bacillus and Enterococcus. Length Heterogeneity-PCR (LH-PCR) electrophoretic peaks from single bacterial clones were used to setup a database representing the bacterial endophytes identified in association with grapevine tissues. Analysis of healthy and phytoplasma-infected grapevine plants showed that LH-PCR could be a useful complementary tool for examining the diversity of bacterial endophytes especially for diversity survey on a large number of samples.     

基于16S rRNA和rpoB基因的分子系统发育分析在铜绿假单胞菌鉴定中的应用

为对比16S rRNA和rpo B基因分子系统发育分析与传统表型分类法对铜绿假单胞菌的鉴定,评估16S rRNA和rpo B基因序列分析在铜绿假单胞菌鉴定中的应用,用表型分类方法对临床自动微生物鉴定系统鉴定为铜绿假单胞菌的23株分离株进行再鉴定,PCR扩增23株分离株16S rRNA和rpo B基因片段,并测序进行系统发育分析。结果表明,表型再鉴定结果与自动微生物鉴定系统鉴定结果一致。基于两个基因的系统发育分析均显示分离株p22与不动杆菌属序列聚为一枝,其余22株分离株与铜绿假单胞菌序列聚为一枝。因此p22应鉴定为不动杆菌,16S rRNA和rpo B基因序列分析均能准确鉴定铜绿假单胞菌并能较好建立假单胞菌属内种间关系。     

A glimpse under the rim – the composition of microbial biofilm communities in domestic toilets

Aim: To determine the microbial composition of biofilms in domestic toilets by molecular means. Methods and Results: Genomic DNA was extracted from six biofilm samples originating from households around Düsseldorf, Germany. While no archaeal 16S rRNA or fungal ITS genes were detected by PCR, fingerprinting of bacterial 16S rRNA genes revealed a diverse community in all samples. These communities also differed considerably between the six biofilms. Using the Ribosomal Database Project (RDP) classifier tool, 275 cloned 16S rRNA gene sequences were assigned to 11 bacterial phyla and 104 bacterial genera. Only 15 genera (representing 121 sequences affiliated with Acidobacteria, Actinobacteria, Bacteroidetes, Planctomycetes and Proteobacteria) occurred in at least half of the samples or contributed at least 10% of the sequences in a single biofilm. These sequences were defined as ‘typical’ for toilet biofilms, and they were examined in more detail. On a 97% sequence similarity level, these sequences represented 56 species. Twelve of these were closely related to well‐described bacterial species, and only two of them were categorized as belonging to risk group 2. No 16S rRNA genes of typical faecal bacteria were detected in any sample. Virtually all ‘typical’ clones were found to be closely related to bacteria or to sequences obtained from environmental sources, implicating that the flushing water is the main source of recruitment. Conclusion: In view of the great diversity of mostly yet‐uncultured bacteria and the considerable differences between individual toilets, very general strategies appear to be most suited for the removal and prevention of toilet biofilms. Significance and Impact of the Study: For the first time, a molecular fingerprinting and cloning approach was used to monitor the species composition in biofilm samples taken from domestic toilets. Knowledge about the microbial composition of biofilms in domestic toilets is a prerequisite for developing and evaluating strategies for their removal and prevention.     

Dynamics of bacterial community exposed to hydrocarbons and oleophilic fertilizer in high-Arctic intertidal beach

Exposure of pristine microbial environments to hydrocarbon contamination stimulates growth of the initially small fraction of indigenous hydrocarbon-degrading bacteria. Custom-made oleophilic fertilizers have been demonstrated to promote oil bioremediation by boosting this proliferation. In the present study, the temporal dynamics of the bacterial community structure and the individual influences of hydrocarbons and an oleophilic fertilizer in shaping the community structure was explored during a 78 days bioremediation experiment in a high-Arctic intertidal beach environment. A combination of cultivation-independent 16S rRNA gene length-heterogeneity polymerase chain reaction (LH-PCR) profiling and identification of hydrocarbon-degrading isolates based on partial 16S rRNA gene sequences was employed. LH-PCR community profiles in the fertilizer alone and fertilized kerosene plots were largely indistinguishable throughout the experimental period, while kerosene alone plots showed a markedly different composition of dominant groups. This pointed to the fertilizer as the more decisive factor in shaping the community structure. Most prominent LH-PCR fragments which emerged after kerosene or fertilizer addition could be provisionally assigned to bacterial taxa through coinciding LH-PCR fragment lengths with hydrocarbon-degrading isolates obtained from the same type of experimental units. However, a few quantitatively significant LH-PCR groups had no counterparts among the cultivated bacteria. One of these was affiliated to a hitherto unspeciated subgroup within the Alkanindiges/Acinetobacter clade of Moraxellaceae by a 16S rRNA gene cloning approach.     

Ribotyping of 16S and 23S rRNA genes and organization of rrn operons in members of the bacterial genera Gemmata,Planctomyces, Thermotoga,Thermus, and Verrucomicrobium

The number of organization of rrn genes of two members of the order Planctomycetales, Planctomyces limnophilus and Gemmata obscuriglobus, as well as three species from other bacterial phyla, namely Thermotoga maritima, Thermus aquaticus and Verrucomicrobium spinosum were examined by Southern blot hybridization analysis of restricted DNA with labeled 16S- and 23S rRNAs. Ribotyping analysis revealed that two species contain unlinked 16S- and 23S rRNA genes. Planctomyces limnophilus possessed two unlinked rrn genes which were separated from each other by at least 4.3 kb, and Thermus aquaticus had to unlinked 16S and 23S rRNA genes, separated from each other by at least 2.5 kb. Gemmata obscuriglobus exhibited five genes for which the organization could as yet not be determined because of the complex hybridization patterns. In the other two species, rrn genes clustered in operons. Thermotoga maritima had a single gene for each rRNA species which were separated by not more than 1.5 kb, while Verrucomicrobium spinosum had four copies of probably linked 16S and 23S rRNA genes with a maximal distance between 16S and 23S rRNA genes of 1.3 kb.     

Carbon utilization profiles of bacteria colonizing the headbox water of two paper machines in a Canadian mill

Forty-one bacterial strains isolated from the headbox water of two machines in a Canadian paper mill were associated with the genera Asticcacaulis, Acidovorax, Bacillus, Exiguobacterium, Hydrogenophaga, Pseudomonas, Pseudoxanthomonas, Staphylococcus, Stenotrophomonas based on the sequence of their 16S rRNA genes. The metabolic profile of these strains were determined using Biolog EcoPlate, and the bacteria were divided into four metabolic groups. Metabolic profiles of the bacterial communities colonizing the headbox water of two paper machines was also determined weekly over a 1 year period. The only compound that was not reduced by the bacterial community was 2-hydroxybenzoic acid. Utilization frequency of the other carbon sources in the Biolog EcoPlate ranged from 3 to 100%. The metabolic profiles of the bacterial community did not vary considerably between the two paper machines. However, the metabolic profile varied among the sampling dates.     

Phylogenetic and metabolic bacterial diversity of <Emphasis Type="Italic">Phragmites australis</Emphasis> periphyton communities in two Hungarian soda ponds

Bacterial diversity of reed (Phragmites australis) periphyton communities of Kelemen-szék and Nagy-Vadas (two Hungarian soda ponds) was investigated using molecular cloning and cultivation-based techniques. The majority of the 80 Kelemen-szék and 72 Nagy-Vadas bacterial isolates proved to be moderately halophilic and alkaliphilic. A great proportion of the isolates showed phosphatase and urease activity, utilized aesculin, citrate and certain biopolymers (e.g., gelatine and tween 80). Partial 16S rDNA sequence analysis of 33 Kelemen-szék and 20 Nagy-Vadas ARDRA group representatives showed Gram-positive (Nesterenkonia, Cellulomonas, Dietzia, Bacillus and Planococcus) dominance at both sampling sites. Species of the genera Acidovorax, Hydrogenophaga (β-Proteobacteria) and Flavobacterium, Sphingobacterium (Bacteroidetes) were represented only from Kelemen-szék. Altogether 16 isolates showed low sequence similarity with yet described bacteria and may represent novel taxa. Screening of the 16S rRNA gene libraries of 129 Kelemen-szék and 158 Nagy-Vadas clones resulted in 30 and 28 different ARDRA groups, respectively. Sequence analysis revealed a Gram-negative (Rheinheimera, Aquimonas, Cellvibrio, Flavobacterium and Sphingobacterium) dominated phylogenetic diversity. A high number of the clones were affiliated with uncultured bacterial clones described from diverse environmental samples.     

Distribution and diversity of carbon monoxide‐oxidizing bacteria and bulk bacterial communities across a succession gradient on a Hawaiian volcanic deposit

Relatively little is known about the distribution and diversity of CO‐oxidizing bacteria during succession on volcanic deposits even though they are among the primary colonists. We surveyed CO‐oxidizing communities across a vegetation gradient on a 1959 cinder deposit using coxL (large subunit gene of carbon monoxide dehydrogenase) sequences. Sequences most closely related to a coxL sequence from Ktedonobacter racemifer, dominated unvegetated cinders, while Proteobacteria‐like sequences dominated vegetated sites. The number of coxL operational taxonomic units (OTUs) increased threefold with increased vegetation, and correlated most strongly with the increased β‐Proteobacteria richness (r = 0.987). These compositional shifts were also reflected in overall bacterial community compositions as determined by 16S rRNA gene analysis. Notably, coxL OTU:16S rRNA OTU ratios increased with increased vegetation, indicating that CO oxidizers became a larger fraction of total bacterial richness during succession. Results from most probable number estimates and maximum potential CO uptake activity assays indicate that increased richness is paralleled by increased CO oxidizer abundance, which likely results from increased vegetation and organic carbon content. Collectively, results suggest that in contrast to patterns observed for plant succession, a versatile bacterial functional group that is important during early colonization and succession can remain important in later stages of succession, irrespective of dramatic environmental changes.     

Corresponding 16S rRNA gene segments in Rhizobiaceae and Aeromonas yield discordant phylogenies

Previous evidence has indicated that the 16S rRNA genes in certain species of Aeromonas may have a history of lateral transfer and recombination. A comparative analysis of patterns of 16S nucleotide sequence polymorphism among species of Rhizobium and Agrobacterium was conducted to determine if there is similar evidence for chimeric 16S genes in members of the Rhizobiaceae. Results from phylogenetic analyses and comparison of patterns of nucleotide sequence polymorphism in portions of rhizobial 16S genes revealed the same type of segment-dependent polymorphic site partitioning that was previously reported for Aeromonas. These results support the hypothesis that certain 16S segments in rhizobia may have a history of lateral transfer and recombination.Abbreviations 16S rRNA 16S ribosomal ribonucleic acid - 16S the 16S rRNA gene     

分离自印度洋深海沉积物的部分链霉菌分离株多位点序列分析

【目的】采用多位点序列分析方法,研究印度洋3 000 m以下深海沉积物中分离得到的16S rRNA基因比对高度相似的链霉菌菌株的种间系统发育关系,同时探讨各管家基因及多基因聚类分析后的种间区分能力。【方法】以分离自印度洋深海沉积物的7株Streptomyces albidoflavus,11株Streptomyces cavourensis,16株Streptomyces pratensis为研究对象,以16S rRNA、atpD、recA和rpoB基因片段为标记,通过PCR扩增、测序,获得序列。同时从NCBI上下载5株S.pratensis上述4个基因的序列,将所有序列在MLST网站进行比对,并构建系统进化树进行比较。【结果】S.pratensis各菌株种内比较发现,16S rRNA基因构建的系统进化树中相同基因型的菌株没有聚在一起,系统进化树不稳定,区分度不高。其余3个构建的系统进化树稳定,菌株的聚类关系与MLST数据库得到的基因型一致。同时,多基因聚类分析后将菌株分为6个类群。在3个种的种间多位点序列比较中,除区分度明显增加、进化树更加稳定以外,还发现rec A基因进化上比较特殊的菌株。【结论】多位点序列分析将实验菌株分为很多不同的类型,成功地将所分离的链霉菌进行了更细的分类,同时也找到部分菌株在个别基因上差异较大。此方法可以用于相近种的快速鉴定。     

Organization of three rRNA (rrn) operons from Sphingobium chungbukense DJ77

The nucleotide sequences of all three rRNA operons (rrnA, rrnB, and rrnC) of Sphingobium chungbukense DJ77 were determined. The three rrn operons have the same gene order (16S rRNA-tRNA^Ile-tRNA^Ala-23S rRNA-5S rRNA-tRNA^fMet). The nucleotide sequences were identical over a 5,468 bp region spanning the 16S rRNA gene to the 5S rRNA gene. Variability was observed in the 5S rRNA-tRNA^fMet spacer sequence of rrnB. The tRNA^fMet gene sequences were identical except for two bases (T₅₇₉₄ and A₅₈₇₁ in rrnB, T₅₉₄₂ and A₅₉₅₆ in rrnA, but C₅₉₄₂ and G₅₉₅₆ in rrnC). Comparative sequence analyses of ribosomal RNA operons from DJ77 with those of the class Alphaproteobacteria, to which the genus Sphingobium belongs, reveal close evolutionary relationships with other members of the order Sphingomonadales.     

Cross-Ocean Distribution of Rhodobacterales Bacteria as Primary Surface Colonizers in Temperate Coastal Marine Waters

Bacterial surface colonization is a universal adaptation strategy in aquatic environments. However, neither the identities of early colonizers nor the temporal changes in surface assemblages are well understood. To determine the identities of the most common bacterial primary colonizers and to assess the succession process, if any, of the bacterial assemblages during early stages of surface colonization in coastal water of the West Pacific Ocean, nonnutritive inert materials (glass, Plexiglas, and polyvinyl chloride) were employed as test surfaces and incubated in seawater off the Qingdao coast in the spring of 2005 for 24 and 72 h. Phylogenetic analysis of the 16S rRNA gene sequences amplified from the recovered surface-colonizing microbiota indicated that diverse bacteria colonized the submerged surfaces. Multivariate statistical cluster analyses indicated that the succession of early surface-colonizing bacterial assemblages followed sequential steps on all types of test surfaces. The Rhodobacterales, especially the marine Roseobacter clade members, formed the most common and dominant primary surface-colonizing bacterial group. Our current data, along with previous studies of the Atlantic coast, indicate that the Rhodobacterales bacteria are the dominant and ubiquitous primary surface colonizers in temperate coastal waters of the world and that microbial surface colonization follows a succession sequence. A conceptual model is proposed based on these findings, which may have important implications for understanding the structure, dynamics, and function of marine biofilms and for developing strategies to harness or control surface-associated microbial communities.     

Phylogenetic characterization of bacterial consortia obtained of corroding gas pipelines in Mexico

Characterization of the microbial populations formed in gas pipelines is essential to understand the metallic surface-microbe interaction, their role in metal corrosion, and to implement efficient monitoring and control strategies. Microbial community analysis in a corroded gas pipeline in a petroleum-producing facility in the Southeast region in Mexico was performed by traditional cultivation techniques and identification based on 16S rRNA gene sequence. In all samples, thin bacterial biofilms were observed and pitting corrosion was reveled after removing the biofilms. Six pure or mixed cultures of anaerobic bacteria were obtained and their 16S rRNA libraries were constructed, respectively. At least two members of each RFLP profile were sequenced and the phylogenetic affiliations of cloned bacterial 16S rRNA genes indicated that native biofilms were mainly colonized by Desulfovibrio vulgaris and Desulfovibrio desulfuricans, sulfate-reducing bacteria members; Citrobacter freundii, an Enterobacteriaceae member; Clostridium celerecrescens and Clostridium sporogenes, spore-forming anaerobic species and Cetobacterium somerae, a microaerotolerant, non-spore-forming fusobacteria. Some of these species have been observed consistently in other steel pipelines previously, but Cetobacterium members and C. celerecrescens are described for the fist time in this corroded gas pipeline. The potential role of each species in biofilm formation and steel corrosion is discussed.     

Quantitative contributions of bacteria and of Deinococcus geothermalis to deposits and slimes in paper industry

Deinococcus geothermalis has frequently been isolated from pink colored deposits of paper industry processes. Laboratory studies have shown that D. geothermalis is capable of forming on nonliving surfaces patchy biofilms that are resistant to adverse agents such as extreme pH, desiccation, solubilising detergents and biocides. This study was done to quantitatively assess the role of D. geothermalis as a biofouler in paper industry. Colored deposits were collected from 24 European and North American paper and board machines and the densities of the bacterial 16S rRNA genes and those of the red slime producers D. geothermalis and Meiothermus spp. were measured by QPCR (quantitative real time PCR). D. geothermalis was found at nine machines, usually from splash area deposits, but its contribution was minor, 0.001–1%, to the total bacterial burden of 8.3 to log 10.5 log units per gram wet-weight of the deposits. When D. geothermalis was found in a measurable quantity, Meiothermus spp. also was found, often in bulk quantity (7–100% of the total bacteria). The data are in line with the properties of D. geothermalis known from laboratory biofilm studies, indicating this species is a pioneer coloniser of machine surfaces and may help other bacteria to adhere and grown into biofilms, rather than competing with them.     

Prokaryotic diversity of a Tunisian multipond solar saltern

16S rRNA gene clone libraries were separately constructed from three ponds with different salt concentrations, M2 (15%), TS38 (25%) and S5 (32%), located within a multipond solar saltern of Sfax. The 16S rRNA genes from 216 bacterial clones and 156 archaeal clones were sequenced and phylogenetically analyzed. 44 operational taxonomic units (OTUs) were generated for Bacteria and 67 for Archaea. Phylogenetic groups within the bacterial domain were restricted to Bacteroidetes and Proteobacteria, with the exception that one cyanobacterial OTU was found in the TS38 pond. 85.7, 26.6 and 25.0% of the bacterial OTUs from M2, TS38 and S5 ponds, respectively, are novel. All archaeal 16S rRNA gene sequences were exclusively affiliated with Euryarchaeota. 75.0, 60.0 and 66.7% of the OTUs from, respectively, M2, TS38 and S5 ponds are novel. The result showed that the Tunisian multipond solar saltern harbored novel prokaryotic diversity that has never been reported before for solar salterns. In addition, diversity measurement indicated a decrease of bacterial diversity and an increase of archaeal diversity with rising salinity gradient, which was in agreement with the previous observation for thalassohaline systems. Comparative analysis showed that prokaryotic diversity of Tunisian saltern was higher than that of other salterns previously studied. A. Sghir and E. Ammar have equally contributed to this work.     

16S rRNA及rpoC1基因用于螺旋藻、节旋藻系统发育的比较北大核心CSCD

【目的】利用16S rRNA和rpoC1基因分子标记研究螺旋藻、节旋藻的系统发育关系,并对其区分能力进行比较。【方法】以84株螺旋藻、节旋藻为研究对象,对其进行16S rRNA、rpoC1基因序列的扩增、测序及分析,并对构建的系统发育树进行对比。【结果】rpoC1基因序列保守位点所占比例49.7%、平均G+C百分含量47.7%和序列相似度76%–100%明显低于16S rRNA基因序列的79.4%、55.6%和91%–100%,其变异程度高于16S rRNA基因;基于16S rRNA、rpoC1基因构建的系统发育NJ树拓扑结构基本一致,84株实验藻株分为2个属3个类群,其中仅F-351、F-904-2、F-1070和TJBC14-1藻株为螺旋藻,其余均为节旋藻;虽然2个基因都不能区分形态种和地理种,但rpoC1基因NJ树的置信度(100%)高于16S rRNA基因(99%),属内分群效果也明显优于16S rRNA基因。【结论】支持了螺旋藻、节旋藻为两个不同属的结论,且在属内分类时rpoC1基因比16S rRNA基因具有更高的区分度。     

Diversity of Actinobacterial community in saline sediments from Yunnan and Xinjiang, China

The diversity and community structures of actinobacteria in saline sediments collected from Yunnan and Xinjiang Provinces, China, were investigated with cultivation and 16S rRNA gene analysis. A total of 163 actinobacterial isolates were obtained, and they were affiliated with the order Actinomycetales (distributed into five suborders: Streptosporangineae, Micrococcineae, Streptomycineae, Pseudonocardineae, and Glycomycineae). A total of 748 actinobacterial 16S rRNA gene clones were examined, and they could be classified into Actinomycetales, Acidimicrobiales, and unclassified actinobacteria. The Actinomycetales sequences were distributed into nine suborders: Streptosporangineae, Glycomycineae, Micromonosporineae, Pseudonocardineae, Corynebacterineae, Frankineae, Propionibacterineae, Streptomycineae, and Micrococcineae. The unclassified actinobacteria contained three new clusters at the level of subclass or order. Our 16S rRNA gene phylogenetic data indicated that actinobacterial communities were very diverse in the investigated saline sediments (salinity 0.4–11.6%) and some actinobacterial members may be halotolerant or halophilic. The actinobacterial community structures in the saline sediments were different from those in marine and freshwater environments. Our data have implications for a better understanding of the distribution of Actinobacteria in saline environments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.