Symbiotic Bacteria in Gills and Guts of Chinese Mitten Crab (Eriocheir sinensis) Differ from the Free-Living Bacteria in Water

Aquatic animals have a close relationship with water, but differences in their symbiotic bacteria and the bacterial composition in water remains unclear. Wild or domestic Chinese mitten crabs (Eriocheir sinensis) and the water in which they live were collected from four sampling sites in Jiangsu and Shanghai, China. Bacterial composition in water, gills or guts of E. sinensis, were compared by high-throughput sequencing using 16S rRNA genes. Analysis of >660,000 sequences indicated that bacterial diversity was higher in water than in gills or guts. Tenericutes and Proteobacteria were dominant phyla in guts, while Actinobacteria, Proteobacteria and Bacteroidetes were dominant in gills and water. Non-metric multidimensional scaling analysis indicated that microbiota from gills, guts or water clearly separated into three groups, suggesting that crabs harbor a more specific microbial community than the water in which they live. The dominant OTUs in crab gut were related to Mycoplasmataceae, which were low in abundance in gills, showing that, like mammals, crabs have body-site specific microbiota. OTUs related to Ilumatobacter and Albimonas, which are commonly present in sediment and seawater, were dominant in gills but almost absent from the sampled water. Considering E. sinensis are bottom-dwelling crustacean and they mate in saline water or seawater, behavior and life cycle of crabs may play an important role in shaping the symbiotic bacterial pattern. This study revealed the relationship between the symbiotic bacteria of Chinese mitten crab and their habitat, affording information on the assembly factors of commensal bacteria in aquatic animals.     

Comparison of the gut microbiota from soldier and worker castes of the termite Reticulitermes grassei

The bacterial microbiota from the whole gut of soldier and worker castes of the termite Reticulitermes grassei was isolated and studied. In addition, the 16S rDNA bacterial genes from gut DNA were PCR-amplified using Bacteria-selective primers, and the 16S rDNA amplicons subsequently cloned into Escherichia coli. Sequences of the cloned inserts were then used to determine closest relatives by comparison with published sequences and with sequences from our previous work. The clones were found to be affiliated with the phyla Spirochaetes, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Synergistetes, Verrucomicrobia, and candidate phyla Termite Group 1 (TG1) and Termite Group 2 (TG2). No significant differences were observed with respect to the relative bacterial abundances between soldier and worker phylotypes. The phylotypes obtained in this study were compared with reported sequences from other termites, especially those of phylotypes related to Spirochaetes, Wolbachia (an Alphaproteobacteria), Actinobacteria, and TG1. Many of the clone phylotypes detected in soldiers grouped with those of workers. Moreover, clones CRgS91 (soldiers) and CRgW68 (workers), both affiliated with 'Endomicrobia', were the same phylotype. Soldiers and workers also seemed to have similar relative protist abundances. Heterotrophic, poly-β-hydroxyalkanoate-accumulating bacteria were isolated from the gut of soldiers and shown to be affiliated with Actinobacteria and Gammaproteobacteria. We noted that Wolbachia was detected in soldiers but not in workers. Overall, the maintenance by soldiers and workers of comparable axial and radial redox gradients in the gut is consistent with the similarities in the prokaryotes and protists comprising their microbiota.     

Intracolonial differences in gut bacterial community between worker and soldier castes of Coptotermes formosanus

Abstract The establishment of symbiotic relationships with intestinal microorganisms enables termites to thrive on recalcitrant substrates such as cellulose and wood. A termite colony is composed of several different castes which have distinct feeding habits. The soldiers, for example, cannot feed by themselves and depend on workers, who feed them with digested or semi‐digested foods. To investigate the influence of feeding habits on the bacterial symbionts, a comparative study of gut bacteria between worker and soldier castes of the termite Coptotermes formosanus was conducted. The bacterial communities of both castes were investigated using denaturing gradient gel electrophoresis (DGGE) and clonal analysis of 16S ribosomal DNA (rDNA). Both methods indicated Bacteroidetes was the common predominant group; the common dominant phylotype was affiliated with a reported uncultured Bacteroidetes phylotype (BCf1–03). There were significant differences in Bacteroidetes and Spirochaetes between two castes. Compared to the gut bacteria of workers, those of soldiers were lower in abundance and diversity of Bacteroidetes and slightly higher in Spirochaetes. Two phylotypes (W8, W11) affiliated to Bacteroidetes and two (W26, W29) affiliated to Spirochaetes were exclusively found in the DGGE profile of the worker caste. Bacteroidetes are assumed to be involved in fermentation of sugars and nitrogenous compounds as well as degradation of uric acid. Spirochaetes are supposed to aid in the functions of acetogenesis and N₂‐fixation. The different feeding habits between workers and soldiers of C. formosanus may explain the observed differences in the gut bacterial community.     

Distinct and complex bacterial profiles in human periodontitis and health revealed by 16S pyrosequencing

Periodontitis has a polymicrobial etiology within the framework of a complex microbial ecosystem. With advances in sequencing technologies, comprehensive studies to elucidate bacterial community differences have recently become possible. We used 454 sequencing of 16S rRNA genes to compare subgingival bacterial communities from 29 periodontally healthy controls and 29 subjects with chronic periodontitis. Amplicons from both the V1-2 and V4 regions of the 16S gene were sequenced, yielding 1 393 579 sequences. They were identified by BLAST against a curated oral 16S database, and mapped to 16 phyla, 106 genera, and 596 species. 81% of sequences could be mapped to cultivated species. Differences between health- and periodontitis-associated bacterial communities were observed at all phylogenetic levels, and UniFrac and principal coordinates analysis showed distinct community profiles in health and disease. Community diversity was higher in disease, and 123 species were identified that were significantly more abundant in disease, and 53 in health. Spirochaetes, Synergistetes and Bacteroidetes were more abundant in disease, whereas the Proteobacteria were found at higher levels in healthy controls. Within the phylum Firmicutes, the class Bacilli was health-associated, whereas the Clostridia, Negativicutes and Erysipelotrichia were associated with disease. These results implicate a number of taxa that will be targets for future research. Some, such as Filifactor alocis and many Spirochetes were represented by a large fraction of sequences as compared with previously identified targets. Elucidation of these differences in community composition provides a basis for further understanding the pathogenesis of periodontitis.     

Characterization of gut bacterial flora of Apis mellifera from north-west Pakistan

Gut microbiota has been recognized to play a beneficial role in honey bees (Apis mellifera). Present study was designed to characterize the gut bacterial flora of honey bees in north-west Pakistan. Total 150 aerobic and facultative anaerobic bacteria from guts of 45 worker bees were characterized using biochemical assays and 16S rDNA sequencing followed by bioinformatics analysis. The gut isolates were classified into three bacterial phyla of Firmicutes (60%), Proteobacteria (26%) and Actinobacteria (14%). Most of the isolates belonged to genera and families of Staphylococcus, Bacillus, Enterococcus, Ochrobactrum, Sphingomonas, Ralstonia, Enterobacteriaceae, Corynebacterium and Micrococcineae. Many of these bacteria were tolerant to acidic environments and fermented sugars, hence considered beneficial gut inhabitants and involved the maintenance of a healthy microbiota. However, several opportunistic commensals that proliferate in the hive environment including members Staphylococcus haemolyticus group and Sphingomonas paucimobilis were also identified. This is the first report on bee gut microbiota from north-west Pakistan geographically situated at the crossroads of Indian subcontinent and central Asia.     

Characterization of the gut microbiome in the beet armyworm Spodoptera exigua in response to the short-term thermal stress

The gut microbiota is critical for energy and nutrient utilization and plays a role in host immunity in response to environmental changes. The beet armyworm Spodoptera exigua is a worldwide polyphagous agricultural pest and has frequently experienced potentially stressful temperature fluctuations under natural environmental conditions. However, little is known about the effects of thermal stress on the gut microbiome of this moth pest. Therefore, we investigated the gut microbiome variations, composition and community structure of S. exigua among low-temperature (10 °C), control (26 °C) and high temperature (35 °C) treatments using 16S amplicon sequencing. Overall, 1,192,707 high-quality reads and 762 operational taxonomic units (OTUs) were detected from 15 samples. A total of 289 genera belonging to 19 bacterial phyla were captured, with Firmicutes and Proteobacteria being the most prominent phyla. Alpha diversity metrics indicated no significant differences in the gut bacterial diversity of S. exigua among the three temperature treatments. Principal coordinates and hierarchical cluster analysis revealed significant differences in the structure of gut microbiota between the low-temperature treatment and the other two temperature treatments. In addition, PICRUSt2 analysis demonstrated that the predicted metagenomes associated with the gut microbiome were amino carbohydrate transport and metabolism, acid transport and metabolism, inorganic ion transport and metabolism and cellular processes. Our study showed that thermal stress induced changes in the gut microbiome of the beet armyworm, which may contribute to better understanding the ecological adaptation of S. exigua under changing temperature trends and to evaluating the use of gut microorganisms as biocontrol agents for this pest.     

Differential abundance and core members of the bacterial community associated with wild male Zeugodacus cucurbitae fruit flies (Insecta: Tephritidae) from three geographical regions of Southeast Asia

Zeugodacus cucurbitae (Coquillet) is one of the most significant and widespread tephritid pest species of agricultural crops. This study reports the bacterial communities associated with Z. cucurbitae from three geographical regions in Southeast Asia (Thailand, Peninsular Malaysia, and Sarawak). The bacterial microbiota were investigated by targeted 16S rRNA gene (V3–V4 region) sequencing using the Illumina Mi-Seq platform. At 97% similarity and filtering at 0.001%, there were seven bacterial phyla and unassigned bacteria, comprising 11 classes, 23 orders, 39 families and 67 genera. The bacterial diversity and richness varied within and among the samples from the three geographical regions. Five phyla were detected for the Sarawak sample, and six each for the Thailand and Peninsular Malaysia samples. Four phyla—Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria—were represented in all the fruit fly specimens, forming the core members of the bacterial community. Proteobacteria was the predominant phylum, followed by Bacteroidetes, Firmicutes, and Actinobacteria. Fifty-three genera were represented in the Thailand sample, 56 in the Peninsular Malaysia sample, and 55 in the Sarawak sample. Forty-two genera were present in all the three geographical regions. The predominant core members were order Enterobacteriales (Proeteobacteria), and family Enterobacteriaceae (Enterobacteriales). Klebsiella (Enterobacteriaceae) was the predominant genus and K. oxytoca the predominant species with all specimens having?>?10% relative abundance. The results indicate the presence of a great diversity as well as core members of the bacterial community associated with different populations of Z. cucurbitae.

     

Pyrosequencing analysis of the bacterial communities in the guts of honey bees Apis cerana and Apis mellifera in Korea

The bacterial communities in the guts of the adults and larvae of the Asian honey bee Apis cerana and the European honey bee Apis mellifera were surveyed by pyrosequencing the 16S rRNA genes. Most of the gut bacterial 16S rRNA gene sequences were highly similar to the known honey bee-specific ones and affiliated with Pasteurellaceae or lactic acid bacteria (LAB). The numbers of operational taxonomic units (OTUs, defined at 97% similarity) were lower in the larval guts (6 or 9) than in the adult guts (18 or 20), and the frequencies of Pasteurellaceae-related OTUs were higher in the larval guts while those of LAB-related OTUs in the adult guts. The frequencies of Lactococcus, Bartonella, Spiroplasma, Enterobacteriaceae, and Flavobacteriaceae-related OTUs were much higher in A. cerana guts while Bifidobacterium and Lachnospiraceae-related OTUs were more abundant in A. mellfera guts. The bacterial community structures in the midguts and hindguts of the adult honey bees were not different for A. cerana, but significantly different for A. mellifera. The above results substantiated the previous observation that honey bee guts are dominated by several specific bacterial groups, and also showed that the relative abundances of OTUs could be markedly changed depending on the developmental stage, the location within the gut, and the honey bee species. The possibility of using the gut bacterial community as an indicator of honey bee health was discussed.     

Diversity of commensal bacteria from mid-gut of pink stem borer (Sesamia inferens [Walker])-Lepidoptera insect populations of India

Sesamia inferens (W.) is polyphagous agricultural pests and prevalent in the India, China, South Asia and South East Asia. Insecticides is not recommended because, apart from the hazardous effects of chemicals, its larvae tunnel throughout the stem from first instar. Associated bacteria with insects provide several benefits to their host, revealing the types of bacteria associated with S. infersns will give basic information, which may throw light on management of this noxious pest. The culture dependant, 16S rRNA gene technique revealed thirty two bacterial isolates from gut of S. inferens from different region of India and host, comprising phyla Proteobacteria, Firmicutes and Bacteroidetes. Among which proteobacteria phyla was dominant with families and genus like Enterobacteriaceae (Citrobacter, Enterobacter, Serratia, Klebsiella and Xenorhabdus), Pseudomonadaceae (Pseudomans), Moraxellaceae (Acinetobactor) and Comamonadaceae (Comamonas). The phyla Firmicutes less dominant with four families and one genus each viz., Staphylococcaceae (Staphylococcus), Bacillaceae (Lysinibacillus), Streptococcaceae (Lactococcus) and Enterococcaceae (Enterococcus). Third phyla had only one family viz., Flavobacteriaceae (Chryseobacterium). The bacterial diversity varied greatly among insects that were from different host plants than those from the same host plant of different locations. This result suggested that the type of host plant greatly influences the mid-gut bacterial diversity more than the location of the host plant of S.inferens. These bacterial populations may have a key role in digestion, as well as other benefits to the S. inferens larvae. Determination of the bacterial community and its biological functions within the insect could provide us with basic information for future pest control research.     

Bacterial Community Structure in Two Permafrost Wetlands on the Tibetan Plateau and Sanjiang Plain,China

Permafrost wetlands are important methane emission sources and fragile ecosystems sensitive to climate change. Presently, there remains a lack of knowledge regarding bacterial communities, especially methanotrophs in vast areas of permafrost on the Tibetan Plateau in Northwest China and the Sanjiang Plain (SJ) in Northeast China. In this study, 16S rRNA-based quantitative PCR (qPCR) and 454 pyrosequencing were used to identify bacterial communities in soils sampled from a littoral wetland of Lake Namco on the Tibetan Plateau (NMC) and an alluvial wetland on the SJ. Additionally, methanotroph-specific primers targeting particulate methane monooxygenase subunit A gene (pmoA) were used for qPCR and pyrosequencing analysis of methanotrophic community structure in NMC soils. qPCR analysis revealed the presence of 10¹⁰ 16S rRNA gene copies per gram of wet soil in both wetlands, with 10⁸ pmoA copies per gram of wet soil in NMC. The two permafrost wetlands showed similar bacterial community compositions, which differed from those reported in other cold environments. Proteobacteria, Actinobacteria , and Chloroflexi were the most abundant phyla in both wetlands, whereas Acidobacteria was prevalent in the acidic wetland SJ only. These four phyla constituted more than 80 % of total bacterial community diversity in permafrost wetland soils, and Methylobacter of type I methanotrophs was overwhelmingly dominant in NMC soils. This study is the first major bacterial sequencing effort of permafrost in the NMC and SJ wetlands, which provides fundamental data for further studies of microbial function in extreme ecosystems under climate change scenarios.     

Redescription of the enigmatic genus Genuotermes Emerson (Isoptera,Termitidae, Termitinae)

The imago and soldier castes of the Neotropical Termitinae species Genuotermes spinifer Emerson are redescribed. The gut anatomy of the worker is described in detail for the first time, and morphological variations in the soldier are noted and illustrated. The known geographical distribution of Genuotermes spinifer is greatly expanded.     

16S-rRNA-based analysis of bacterial diversity in the gut of fungus-cultivating termites (Microtermes and Odontotermes species)

The interaction between termites and their gut symbionts has continued to attract the curiosity of researchers over time. The aim of this study was to characterize and compare the bacterial diversity and community structure in the guts of three termites (Odontotermes somaliensis, Odontotermes sp. and Microtermes sp.) using 16S rRNA gene sequencing of clone libraries. Clone libraries were screened by restriction fragment length polymorphism and representative clones from O. somaliensis (100 out of 330 clones), Odontotermes sp. (100 out of 359 clones) and Microtermes sp. (96 out 336 clones) were sequenced. Phylogenetic analysis indicated seven bacterial phyla were represented: Bacteroidetes, Spirochaetes, Firmicutes, Proteobacteria, Synergistetes, Planctomycetes and Actinobacteria. Sequences representing the phylum Bacteroidetes (>60 %) were the most abundant group in Odontotermes while those of Spirochaetes (29 %) and Firmicutes (23 %) were the abundant groups in Microtermes. The gut bacterial community structure within the two Odontotermes species investigated here was almost identical at the phylum level, but the Microtermes sp. had a unique bacterial community structure. Bacterial diversity was higher in Odontotermes than in Microtermes. The affiliation and clustering of the sequences, often with those from other termites’ guts, indicate a majority of the gut bacteria are autochthonous having mutualistic relationships with their hosts. The findings underscore the presence of termite-specific bacterial lineages, the majority of which are still uncultured.     

Characterization of bacterial community structure in the rhizosphere of Triticum aestivum L.

The plant microbiome influence plant health, yield and vigor and has attained a considerable attention in the present era. In the current study, native bacterial community composition and diversity colonizing Triticum aestivum L. rhizosphere at two distant geographical locations including Mirpur Azad Kashmir and Islamabad was elucidated. Based on IonS5™XL platform sequencing of respective samples targeting 16S rRNA gene that harbor V3-V4 conserved region revealed 1364 and 1254 microbial operational taxonomic units (OTUs) at ≥97% similarity and were classified into 23, 20 phyla; 70, 65 classes; 101, 87 orders; 189,180 families; 275, 271 genera and 94, 95 species. Respective predominant phyla accounting for 97.90% and 98.60% of bacterial community were Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, Firmicutes, Chloroflexi and Gemmatimonadetes. Diversity indices revealed variations in relative abundance of bacterial taxa owing to distant geographical locations however predominant bacterial taxa at both locations were similar. These findings paved a way to dissect consequence of associated microbiota on future wheat production system.     

Structure of the human gastric bacterial community in relation to Helicobacter pylori status

The human stomach is naturally colonized by Helicobacter pylori, which, when present, dominates the gastric bacterial community. In this study, we aimed to characterize the structure of the bacterial community in the stomach of patients of differing H. pylori status. We used a high-density 16S rRNA gene microarray (PhyloChip, Affymetrix, Inc.) to hybridize 16S rRNA gene amplicons from gastric biopsy DNA of 10 rural Amerindian patients from Amazonas, Venezuela, and of two immigrants to the United States (from South Asia and Africa, respectively). H. pylori status was determined by PCR amplification of H. pylori glmM from gastric biopsy samples. Of the 12 patients, 8 (6 of the 10 Amerindians and the 2 non-Amerindians) were H. pylori glmM positive. Regardless of H. pylori status, the PhyloChip detected Helicobacteriaceae DNA in all patients, although with lower relative abundance in patients who were glmM negative. The G2-chip taxonomy analysis of PhyloChip data indicated the presence of 44 bacterial phyla (of which 16 are unclassified by the Taxonomic Outline of the Bacteria and Archaea taxonomy) in a highly uneven community dominated by only four phyla: Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Positive H. pylori status was associated with increased relative abundance of non-Helicobacter bacteria from the Proteobacteria, Spirochetes and Acidobacteria, and with decreased abundance of Actinobacteria, Bacteroidetes and Firmicutes. The PhyloChip detected richness of low abundance phyla, and showed marked differences in the structure of the gastric bacterial community according to H. pylori status.     

Microbial Community Diversity in the Gut of the South American Termite Cornitermes cumulans (Isoptera: Termitidae)

Termites inhabit tropical and subtropical areas where they contribute to structure and composition of soils by efficiently degrading biomass with aid of resident gut microbiota. In this study, culture-independent molecular analysis was performed based on bacterial and archaeal 16S rRNA clone libraries to describe the gut microbial communities within Cornitermes cumulans, a South American litter-feeding termite. Our data reveal extensive bacterial diversity, mainly composed of organisms from the phyla Spirochaetes, Bacteroidetes, Firmicutes, Actinobacteria, and Fibrobacteres. In contrast, a low diversity of archaeal 16S rRNA sequences was found, comprising mainly members of the Crenarchaeota phylum. The diversity of archaeal methanogens was further analyzed by sequencing clones from a library for the mcrA gene, which encodes the enzyme methyl coenzyme reductase, responsible for catalyzing the last step in methane production, methane being an important greenhouse gas. The mcrA sequences were diverse and divided phylogenetically into three clades related to uncultured environmental archaea and methanogens found in different termite species. C. cumulans is a litter-feeding, mound-building termite considered a keystone species in natural ecosystems and also a pest in agriculture. Here, we describe the archaeal and bacterial communities within this termite, revealing for the first time its intriguing microbiota.     

Soldier determination in Pheidole bicarinata: Effect of methoprene on caste and size within castes

Topical application of methoprene to final-instar larvae of the ant Pheidole bicarinata can induce soldier development. Soldier induction takes place if methoprene levels are above a soldier-determining threshold during a critical period of juvenile hormone-sensitivity that occurs during about days 4–6 of the final instar. Furthermore, the amount of exogenous methoprene applied affects the timing of metamorphosis and the adult size in both the minor worker and soldier castes. When larvae that receive methoprene treatment become minor workers these are always larger than acetone-treated controls. In larvae that become soldiers, growth and timing of metamorphosis vary with the dose of methoprene, but in a more complex way. A high dose of methoprene produces a metamorphic delay and large soldiers. However, the lowest effective dose for soldier induction produces early metamorphosis and small adults. On the basis of these results, we have expanded our model of a mechanism by which juvenile hormone could control determination of worker castes in Pheidole bicarinata.     

Culture-independent identification of gut bacteria in fourth-instar red imported fire ant, Solenopsis invicta Buren, larvae

Red imported fire ants (RIFA), Solenopsis invicta Buren, are medical, urban, and agricultural pests from South America. They are successful invaders due to their preference for disturbed habitats, high reproductive rates, and the ability to feed on a wide variety of food items (omnivorous). Fourth-instar larvae are used by the colony to digest solid food and then regurgitate it for consumption by workers and queens. Larvae are an ideal source of investigations of endosymbiotic bacteria possibly involved in nutrient distributions. Our study utilized 16S rDNA sequencing to describe the composition of the bacterial community in fourth-instar ant larvae in order to identify possible endosymbiotic bacteria present therein. The 16S rRNA gene was directly amplified from mixed-population DNA of whole fire ant larval guts and cloned into Escherichia coli. Bacterial communities from three geographically separated RIFA colonies were examined. Sequenced bacterial clones from guts were determined to be predominantly from the phylum Proteobacteria and the family Enterobacteriaceae. Our results did not detect the presence of endosymbiotic bacteria in the guts of RIFA larvae among the colonies. In addition, minimal species overlap was found when bacterial inventories were compared among colonies. Thus, bacteria coadapted with red imported fire ant larvae were not detected. Identified bacteria were not closely affiliated with endosymbiotic bacteria common in other insect species. Bacteria communities appeared to be unique to each geographical location and were determined by the foods consumed by the ants.     

Midgut bacterial communities in the giant Asian honeybee (Apis dorsata) across 4 developmental stages: A comparative study

Bacterial communities are known to play important roles during the developmental stages of insects, but current knowledge of bacteria associated with the midgut of Apis dorsata, the giant Asian honeybee, is limited. Using polymerase chain reaction‐denaturing gradient gel electrophoresis analysis (PCR‐DGGE) and 16S rRNA sequencing, the aim of this study was to determine the dynamics of bacterial community structure across four A. dorsata life stages in different geographical locations. The results reveal that bacterial diversity increased as the bee progressed through larval stage to newly emerged worker and old worker. However, in the pupal stage, no bands identified as bacteria could be observed. Overall, 2 bacterial phyla (Proteobacteria and Firmicutes) and 4 classes (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Bacilli) were identified, but the frequency varied among the different stages and locations. The classes of Gammaproteobacteria and Bacilli dominated among larval, newly emerged worker and old worker developmental stages.     

塔克拉玛干沙尘暴源区空气细菌群落多样性

【目的】采集新疆塔克拉玛干沙漠腹地和周围沙尘暴源区空气样品,对不同样点沙尘暴发生前期、中期、后期空气细菌进行群落结构解析。阐明新疆沙尘暴源区空气细菌种属特征和群落多样性动态变化规律。【方法】基于Illumina HiSeq测序平台,利用双末端测序方法,构建16S rRNA小片段文库进行测序。【结果】塔克拉玛干沙尘暴源区空气细菌主要分为4门37个属,Proteobacteria占67.6%、Bacteroidetes占17.6%、Actinobacteria占11.7%、Firmicutes占2.9%;在属水平上,新疆沙尘暴源区有8个不同优势属,非度量多维尺度分析表明,不同样点在不同时期的细菌群落组成差异极显著;典范对应分析表明,环境因子对沙尘暴源区空气细菌多样性的影响大小为:海拔纬度经度湿度气压温度,且差异不显著。【结论】新疆沙尘暴源区空气细菌群落多样性和丰富度高;不同样点沙尘暴前期、中期、后期的空气细菌群落组成差异极显著;沙尘暴对5个源区固有细菌群落影响差异极显著。     

Bacterial community diversity associated with four marine sponges from the South China Sea based on 16S rDNA-DGGE fingerprinting

Culture-independent 16S rDNA-DGGE fingerprinting and phylogenetic analysis were used to reveal the community structure and diversity of the predominant bacteria associated with the four sponges Stelletta tenui, Halichrondria, Dysidea avara, and Craniella australiensis from the South China Sea for the first time. Sponge total community DNA extracted with a direct grinding disruption based method was used successfully after series dilution for 16S rDNA PCR amplification, which simplifies the current procedure and results in good DGGE banding profiles. 16S rDNA-V3 fragments from 42 individual DGGE bands were sequenced and the detailed corresponding bacteria were found in sponges for the fist time based on BLAST results. The sponge-associated bacteria are sponge host-specific because each of the tested four sponges from the same geographical location has different predominant bacterial diversity. Proteobacteria, e.g. α, β and γ subdivisions, make up the majority of the predominant bacteria in sponges and are perhaps in close symbiotic relationship with sponges. Though similar bacteria with close phylogenetic relationships were found among different sponges, the sponge-associated predominant bacterial community structures differ. Sponge C. australiensis has the greatest bacterial diversity, with the four bacteria phyla Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria, followed by the sponge D. avara with the two phyla Proteobacteria and Bacteroidetes, and the sponges S. tenui and Halichrondria with the phylum Proteobacteria. DGGE fingerprint-based analysis should ideally be integrated with band cloning and sequencing, phylogenetic analysis and molecular techniques to obtain precise results in terms of the microbial community and diversity.