Transmission of nephridial bacteria of the earthworm Eisenia fetida

The lumbricid earthworms (annelid family Lumbricidae) harbor gram-negative bacteria in their excretory organs, the nephridia. Comparative 16S rRNA gene sequencing of bacteria associated with the nephridia of several earthworm species has shown that each species of worm harbors a distinct bacterial species and that the bacteria from different species form a monophyletic cluster within the genus Acidovorax, suggesting that there is a specific association resulting from radiation from a common bacterial ancestor. Previous microscopy and culture studies revealed the presence of bacteria within the egg capsules and on the surface of embryos but did not demonstrate that the bacteria within the egg capsule were the same bacteria that colonized the nephridia. We present evidence, based on curing experiments, in situ hybridizations with Acidovorax-specific probes, and 16S rRNA gene sequence analysis, that the egg capsules contain high numbers of the bacterial symbiont and that juveniles are colonized during development within the egg capsule. Studies exposing aposymbiotic hatchlings to colonized adults and their bedding material suggested that juvenile earthworms do not readily acquire bacteria from the soil after hatching but must be colonized during development by bacteria deposited in the egg capsule. Whether this is due to the developmental stage of the host or the physiological state of the symbiont remains to be investigated.     

Transmission of Nephridial Bacteria of the Earthworm Eisenia fetida

The lumbricid earthworms (annelid family Lumbricidae) harbor gram-negative bacteria in their excretory organs, the nephridia. Comparative 16S rRNA gene sequencing of bacteria associated with the nephridia of several earthworm species has shown that each species of worm harbors a distinct bacterial species and that the bacteria from different species form a monophyletic cluster within the genus Acidovorax, suggesting that there is a specific association resulting from radiation from a common bacterial ancestor. Previous microscopy and culture studies revealed the presence of bacteria within the egg capsules and on the surface of embryos but did not demonstrate that the bacteria within the egg capsule were the same bacteria that colonized the nephridia. We present evidence, based on curing experiments, in situ hybridizations with Acidovorax-specific probes, and 16S rRNA gene sequence analysis, that the egg capsules contain high numbers of the bacterial symbiont and that juveniles are colonized during development within the egg capsule. Studies exposing aposymbiotic hatchlings to colonized adults and their bedding material suggested that juvenile earthworms do not readily acquire bacteria from the soil after hatching but must be colonized during development by bacteria deposited in the egg capsule. Whether this is due to the developmental stage of the host or the physiological state of the symbiont remains to be investigated.     

Verminephrobacter eiseniae type IV pili and flagella are required to colonize earthworm nephridia

The bacterial symbiont Verminephrobacter eiseniae colonizes nephridia, the excretory organs, of the lumbricid earthworm Eisenia fetida. E. fetida transfers V. eisenia into the egg capsule albumin during capsule formation and V. eiseniae cells migrate into the earthworm nephridia during embryogenesis, where they bind and persist. In order to characterize the mechanistic basis of selective tissue colonization, methods for site-directed mutagenesis and colonization competence were developed and used to evaluate the consequences of individual gene disruptions. Using these newly developed tools, two distinct modes of bacterial motility were shown to be required for V. eiseniae colonization of nascent earthworm nephridia. Flagella and type IV pili mutants lacked motility in culture and were not able to colonize embryonic earthworms, indicating that both twitching and flagellar motility are required for entrance into the nephridia.     

Diversity and host specificity of the Verminephrobacter-earthworm symbiosis

Symbiotic bacteria of the genus Verminephrobacter (Betaproteobacteria) were detected in the nephridia of 19 out of 23 investigated earthworm species (Oligochaeta: Lumbricidae) by 16S rRNA gene sequence analysis and fluorescence in situ hybridization (FISH). While all four Lumbricus species and three out of five Aporrectodea species were densely colonized by a mono-species culture of Verminephrobacter, other earthworm species contained mixed bacterial populations with varying proportions of Verminephrobacter; four species did not contain Verminephrobacter at all. The Verminephrobacter symbionts could be grouped into earthworm species-specific sequence clusters based on their 16S rRNA and RNA polymerase subunit B (rpoB) genes. Closely related host species harboured more closely related symbionts than did distantly related hosts. Co-diversification of the symbiotic partners could not be demonstrated unambiguously due to the poor resolution of the host phylogeny [based on histone H3 and cytochrome c oxidase subunit I (COI) gene sequence analyses]. However, there was a pattern of symbiont diversification within four groups of closely related hosts. The mean rate of symbiont 16S rRNA gene evolution was determined using a relaxed clock model, and the rate was calibrated with paleogeographical estimates of the time of origin of Lumbricid earthworms. The calibrated rates of symbiont 16S rRNA gene evolution are 0.012-0.026 substitutions per site per 50 million years and thus similar to rates reported from other symbiotic bacteria.     

Verminephrobacter aporrectodeae sp. nov. subsp. tuberculatae and subsp. caliginosae, the specific nephridial symbionts of the earthworms Aporrectodea tuberculata and A. caliginosa

Clone library-based studies have shown that almost all lumbricid earthworm species harbour host-specific symbiotic bacteria belonging to the novel genus Verminephrobacter in their nephridia (excretory organs). To date the only described representative from this genus is Verminephrobacter eiseniae, the specific symbiont of the earthworm Eisenia fetida. In this study two novel rod-shaped, non-endosporeforming, betaproteobacterial symbionts were isolated from the nephridia of two closely related earthworm species. Both isolates were affiliated with the genus Verminephrobacter by 16S rRNA gene sequence analysis. Similarly to V. eiseniae, the two isolates grew aerobically with a preference for low oxygen concentrations on a range of sugars, fatty acids and amino acids and fermentatively on glucose and pyruvate. These phenotypes match well with the conditions reported or inferred for the nephridial environment. Based on 16S rRNA gene similarity, DNA–DNA hybridization value and phenotypic characteristics the two isolates are clearly distinct from V. eiseniae. Phenotypic characteristics could not clearly differentiate the two strains as separate species but a low DNA–DNA hybridization value of 57.3%, their earthworm host specificity, differing temperature ranges and pH optima suggest that they represent two subspecies of a novel species of Verminephrobacter. For this species, the name V. aporrectodeae sp. nov. is proposed, with the two subspecies V. aporrectodeae subsp. tuberculatae (type strain, At4^T = DSM 21361^T = LMG 25313^T) and V. aporrectodeae subsp. caliginosae (type strain, Ac9^T = DSM 21895^T = LMG 25312^T) isolated from the nephridia of the earthworms Aporrectodea tuberculata and A. caliginosa, respectively.     

赤子爱胜蚓对两种土壤中细菌群落结构组成及多样性的影响

本研究探讨赤子爱胜蚓（Eisenia fetida）对不同土壤细菌群落结构的影响,以便利用蚯蚓改善土壤生物学质量。选取华南地区赤红壤和水稻土,分别接种赤子爱胜蚓进行10 d室内盆钵培养,运用16S rDNA Illumina Miseq高通量测序技术对培养前后土壤的细菌群落结构进行分析。结果显示：（1）经赤子爱胜蚓取食后,两种土壤的细菌群落结构均发生了改变。赤红壤中增加了5个非优势细菌门,分别为FBP、纤维杆菌门（Fibrobacteres）、OP11、柔膜菌门（Tenericutes）和Thermi;Cytophagia、Spartobacteria和疣微菌纲（Verrucomicrobiae）从非优势细菌纲变为优势细菌纲;Solibacteres从优势细菌纲变为非优势细菌纲。水稻土中海绵菌门（Poribacteria）为新增加的1个非优势细菌门;螺旋体门（Spirochaetes）从非优势细菌门变为优势细菌门;4个非优势细菌门消失,分别为SBR1093、SC4、WS4和WS5;螺旋体纲（Spirochaetes）和疣微菌纲从非优势细菌纲变为优势细菌纲;浮霉菌纲（Planctomycetia）从优势细菌纲变为非优势细菌纲;酸杆菌门（Acidobacteria）、放线菌门（Actinobacteria）、拟杆菌门（Bacteroidetes）、绿弯菌门（Chloroflexi）、厚壁菌门（Firmicutes）、浮霉菌门（Planctomycetes）、变形菌门（Proteobacteria）和疣微菌门（Verrucomicrobia）依然是两种土壤中的优势类群;（2）赤红壤中酸杆菌门的相对丰度显著下降44.90%,拟杆菌门的相对丰度显著上升14.88%;水稻土中酸杆菌门、绿弯菌门、芽单胞菌门（Gemmatimonadetes）、硝化螺旋菌门（Nitrospirae）、浮霉菌门和疣微菌门等6种细菌类群的相对丰度分别显著下降49.05%、20.44%、64.01%、35.00%、33.56%和24.38%,而拟杆菌门和螺旋体门的相对丰度分别显著上升28.85%和154.17%;（3）两种土壤细菌丰度的变化情况存在差异：赤红壤细菌丰度呈上升趋势,水稻土细菌丰度呈下降趋势,而两种土壤的细菌多样性变化则均呈下降趋势。本研究说明,经赤子爱胜蚓取食后赤红壤和水稻土的细菌群落结构组成和多样性均发生变化,为深入理解蚯蚓与土壤微生物群落的相互作用机制提供参考依据。     

Dynamic Changes in Bacterial Communities During Compost and Earthworm Treatment of Low-Grade Potassium Ore

Both composting and earthworm treatment can degrade potassium rock powders and bacteria play a key role during the bio-processings. To understand the dominant bacteria and bacterial profile in biological conversion of the ore including compost and earthworm treatment, the bacterial communities in the compost were studied by using the method of denaturing gradient gel electrophoresis (DGGE) after ore powder was co-composted with organic wastes and then treated with earthworms. Results showed bacterial community structure changed very quickly during the early stages of solid-state fermentation, but relatively stable in the later stages of fermentation and during earthworm treatment. The dominant species of bacteria largely varied in the earlier stage of composting, but they were stable in the latter stage and during earthworm treatment. Two classes of bacteria, represented by band 12 (likely Alteromonas) and band 14 (likely Firmicutes) in DGGE profile, were found to be dominant species over the entire solid-state fermentation period. No special dominant bacterial species appeared during earthworm treatment. Phylogenetic studies of the bacteria based on 16S rRNA sequences indicate that major 13 bands came from phyla Proteobacteria and Firmicutes, suggesting that bacteria in these phyla played an important role during the compost treatment.     

8-hydroxydeoxyguanosine generated in the earthworm Eisenia fetida grown in metal-containing soil

Heavy metal pollution of soil causes biological problems, such as mutagenicity to living organisms, including human beings. However, few methods have been developed to assess metal mutagenicity in soil. To avoid metal mutagenicity, an adequate bio-monitoring method is required. In the present study, to determine if the analysis of oxidative DNA damage generated in the earthworm is a useful bio-monitoring method for soil mutagenicity, the accumulation of 8-hydroxydeoxyguanosine (8-OH-dG), a major form of oxidative DNA damage, in Eisenia fetida (Savigny, 1826) treated with cadmium chloride (CdCl2) or nickel chloride (NiCl2) was analyzed. E. fetida was treated with Cd (10 or 200 microg/g soil) or Ni (10 or 200 microg/g soil) for 1, 2, and 3 weeks or 3 months. After metal exposure, the metal concentration in E. fetida was analyzed by atomic absorption spectrometry and the 8-OH-dG accumulated in E. fetida was analyzed by HPLC analyses and immunohistochemistry. Atomic absorption spectrometry revealed that Cd, but not Ni, accumulated within E. fetida. The 8-OH-dG levels in the DNA of E. fetida treated with Cd for 3 months were significantly higher than those in control E. fetida. Moreover, immunohistochemical analyses revealed that positive signals for 8-OH-dG accumulation in seminal vesicles were detected only in E. fetida treated with 10 microg of Cd for 3 months. Although some points remain unresolved, a bio-monitoring system analyzing the DNA damage generated in the earthworm might be useful for the assessment of the mutagenicity of soil contaminated with various heavy metals, such as Cd.     

Decomposition of kitchen waste amended with cow manure using an epigeic species (Eisenia fetida) and an anecic species (Lampito mauritii)

An epigeic (surface dweller) earthworm species Eisenia fetida and an anecic (deep burrower) earthworm species Lampito mauritii have been tested for decomposition of kitchen waste plus cow dung. Chemical analyses of worm-worked substrates by both species showed g/kg increases in nitrogen, phosphorus and potassium and decreases in C/N and C/P ratios after 150 days of vermicomposting. However, organic carbon matter showed reduction in their amounts for 3-4 months and afterwards slightly increased up to 150 days. E. fetida produced 0.27%, 156%, 41% and 38% increases in organic carbon, nitrogen, phosphorus, and potassium as well as 61% and 29% decreases in C/N and C/P ratios as compared to control after 150 days of earthworm inoculation. In contrast, L. mauritii produced 14%, 102%, 33% and 42% increases in organic carbon, nitrogen, phosphorus and potassium as well as 43% and 14% decreases in C/N and C/P ratios as compared to control after 150 days of earthworm activity. There was moderate mineralization and faster decomposition by E. fetida in comparison to moderate mineralization and moderate decomposition by L. mauritii. The average numbers of cocoons and adults produced were greater by E. fetida than by L. mauritii after 150 days. These results indicate E. fetida may be a better adapted species for decomposition of kitchen waste plus cow dung under tropical conditions.     

Comparative studies on biomass production, life cycles and composting efficiency of Eisenia fetida (Savigny) and Lampito mauritii (Kinberg)

Comparative studies were performed to evaluate composting potential, biomass growth and biology of a non-native (Eisenia fetida) and an endemic (Lampito mauritii) species of earthworm in the semiarid environment of Jodhpur district of Rajasthan in India. Earthworms were reared in a mixed bedding material comprised of biogas slurry, cowdung, wheat straw, leaflitter, sawdust and kitchen waste. The percentage of organic carbon of the culture bedding material declined upto 105 days with E. fetida and 120 with L. mauritii. The percentage of nitrogen, phosphorous and potassium increased as a function of the vermicomposting period. In contrast, C/N and C/P ratios decreased day by day. Both species were effective for decomposition and mineralization of mixed bedding in the semiarid environment. A comparative assessment of biomass growth of E. fetida and L. mauritii was done under controlled laboratory conditions. The optimum temperature, moisture content and pH for E. fetida were 25 degrees C, 70% and 6.5, respectively. However, the optimum temperature, moisture content and pH for growth and development of L. mauritii were 30 degrees C, 60% and 7.5, respectively. The biology and reproductive rates of both species were also studied in the laboratory using mixed bedding. Cocoon production was higher for E. fetida than L. mauritii. The net reproductive rate was 9 per month in the case of E. fetida and 1 per month for L. mauritii. Fertilized eggs of E. fetida and L. mauritii developed into adults within 4 and 5 1/4 months, respectively. These observations indicate E. fetida may be a more efficient breeder than L. mauritii in the desert region of Rajasthan.     

Tracking and predation on earthworms by the invasive terrestrial planarian Bipalium adventitium (Tricladida, Platyhelminthes)

The potential ecological impact of exotic terrestrial planarians will be determined in part by their sensory abilities and predatory behavior. It has been suggested that these flatworms may only encounter their earthworm prey by chance, hence restricting the breadth of species they will feed upon and the number of microhabitats in which predator-prey interactions occur. We hypothesized that those flatworms that have already successfully invaded North America (genus Bipalium) actually detect and follow chemical trails of earthworms and possess the behavioral repertoire needed to feed on the prey in a range of microhabitats. We examined: (1) the tendency of Bipalium adventitium to follow chemical trails left by injured and un-injured earthworms; (2) the behavioral repertoire and predatory success of B. adventitium feeding on three earthworm species in subterranean tunnels; and (3) the response of flatworms to the reportedly defensive secretions of the earthworm Eisenia fetida in tunnels. B. adventitium detected and followed trails of earthworm mucus and secretions left by injured and un-injured earthworms. Flatworms followed trails on a range of substrates and pursued and captured three species of earthworms in subterranean tunnels, including individuals many times their mass. Although most behavior exhibited during underground attacks was similar to that reported for surface encounters, the flatworms also behaved in ways that blocked earthworm escape from tunnels. The flatworms were less successful at preying on E. fetida than on Lumbricus rubellus and Lumbricus terrestris in underground tunnels and showed some aversion to the secretions from E. fetida.     

Earthworm egg capsules as vectors for the environmental introduction of biodegradative bacteria.

Earthworm egg capsules (cocoons) may acquire bacteria from the environment in which they are produced. We found that Ralstonia eutropha (pJP4) can be recovered from Eisenia fetida cocoons formed in soil inoculated with this bacterium. Plasmid pJP4 contains the genes necessary for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4-dichlorophenol (2,4-DCP) degradation. In this study we determined that the presence of R. eutropha (pJP4) within the developing earthworm cocoon can influence the degradation and toxicity of 2,4-D and 2,4-DCP, respectively. The addition of cocoons containing R. eutropha (pJP4) at either low or high densities (10(2) or 10(5) CFU per cocoon, respectively) initiated degradation of 2,4-D in nonsterile soil microcosms. Loss of 2,4-D was observed within the first week of incubation, and respiking the soil with 2,4-D showed depletion within 24 h. Microbial analysis of the soil revealed the presence of approximately 10(4) CFU R. eutropha (pJP4) g-1 of soil. The toxicity of 2,4-DCP to developing earthworms was tested by using cocoons with or without R. eutropha (pJP4). Results showed that cocoons containing R. eutropha (pJP4) were able to tolerate higher levels of 2,4-DCP. Our results indicate that the biodegradation of 2, 4-DCP by R. eutropha (pJP4) within the cocoons may be the mechanism contributing to toxicity reduction. These results suggest that the microbiota may influence the survival of developing earthworms exposed to toxic chemicals. In addition, cocoons can be used as inoculants for the introduction into the environment of beneficial bacteria, such as strains with biodegradative capabilities.     

Diversity and stability of egg‐bacterial assemblages: The role of paternal care in the glassfrog Hyalinobatrachium colymbiphyllum

Embryos of oviparous organisms must cope with harsh environments and are especially susceptible to disease, considering that many immune mechanisms do not develop until later in life. Parents may transmit symbiotic microflora to eggs, which can contribute to embryo immune defense. Despite the importance of symbiotic microbes for immune function and survival of adult amphibians, vertical transfer of symbionts in amphibians has received less attention than in other taxa. Here, we test the role of male‐only parental care in establishing and maintaining the diversity of egg‐bacterial assemblages in a Neotropical glassfrog (Centrolenidae). Previous research suggests that father Hyalinobatrachium colymbiphyllum may transfer bacterial symbionts to their eggs. We combined a male‐removal experiment in situ with 16S rRNA gene amplicon sequencing to determine whether egg attendance by father H. colymbiphyllum influences the bacterial community and survival of eggs. We found that eggs harbor a diverse and stable bacterial assemblage. Despite different host environments, we found that adult skin and eggs supported very similar bacterial assemblages—even after removing fathers. While we found overlap in the bacteria present on eggs and their fathers, our experiment reveals that extended male care does not contribute to the maintenance of egg‐bacterial communities, so there may be other potential routes of transfer. This study contributes to our understanding of the diversity and maintenance of egg microbiomes, and motivates further research on how initial bacteria are acquired and the ontogenetic development of host–symbiont communities.     

Mitochondrial L-rRNA from Aspergillus nidulans: potential secondary structure and evolution.

The alignment of gene sequences coding for A. nidulans mitochondrial L-rRNA and E. coli 23S rRNA indicates a strong conservation of primary and potential secondary structure of both rRNA molecules, except that homologies to the 5'-terminal 5.8S-like region and the 3'-terminal 4.5S-like region of bacterial rRNA are not detectable on mtDNA. The structural organization of the A. nidulans mt L-rRNA gene corresponds to that of yeast omega + strains: both genes are interrupted by a large intron sequence (1678 and 1143 bp, respectively) and by another smaller insert (91 and 66 bp) at homologous positions within domain V. An evolutionary tree derived from conserved L-rRNA gene sequences of yeast nuclei, E. coli, maize chloroplasts and six mitochondrial species exhibits a common root of organelle and bacterial sequences separating early from the nuclear branch.     

Seasonal population dynamics of Eisenia fetida (Savigny, 1826) (Oligochaeta, Lumbricidae) in the field

In order to assess the response of epigeic earthworms to seasonal changes we monitored the population dynamics of Eisenia fetida (Oligochaeta, Lumbricidae) in a manure heap in the field during a year. Earthworms were hand-sorted from five 0.25 x 0.25 x 0.20 m blocks around the heap in November (autumn) 1999 and in January (winter), April (spring) and August (summer) 2000 to determine earthworm population dynamics. Earthworms of each block were classified into different age classes: mature, preclitellate, juvenile, hatchling and cocoon, and afterwards counted and weighed. Seasonality had a strong effect on the density, biomass and reproductive activity of the population. The population of E. fetida was characterized by a high density of individuals and the predominance of mature individuals throughout the year. Maximum density, mating activity and size of cocoons were achieved in spring, but there were not changes in the number of cocoons per mature earthworm throughout the year. Unexpectedly, the smallest cocoons were produced in winter by the largest individuals. These results suggest that E. fetida is able to allocate resources to growth and/or reproduction in response to environmental fluctuations.     

Earthworms as modifiers of the structure and biological activity of humic acids

Passage of humic acids (HAs) through the digestive tract of the earthworm, Eisenia fetida andrei, resulted in a decrease in molecular masses of the HAs. The effect of earthworm-modified HAs on individual bacteria and on bacterial communities as a whole is different from the effect of native HAs. Modified HA probably induces and regulates microbial successions in soils and composts in a different manner than the native HA, suppressing or stimulating different groups of microorganisms. These results may explain why the positive effects of commercial humates in real soil ecosystems, unlike model communities, attenuate rapidly.     

Intergenerational Transfer of Specific Bacteria in Corals and Possible Implications for Offspring Fitness

Diverse and abundant bacterial populations play important functional roles in the multi-partite association of the coral holobiont. The specificity of coral-associated assemblages remains unclear, and little is known about the inheritance of specific bacteria from the parent colony to their offspring. This study investigated if broadcast spawning and brooding corals release specific and potentially beneficial bacteria with their offspring to secure maintenance across generations. Two coral species, Acropora tenuis and Pocillopora damicornis, were maintained in 0.2 μm filtered seawater during the release of their gametes and planulae, respectively. Water samples, excluding gametes and planulae, were subsequently collected, and bacterial diversity was assessed through a pyrosequencing approach amplifying a 470-bp region of the 16S rRNA gene including the variable regions 1–3. Compared to the high bacterial diversity harboured by corals, only a few taxa of bacteria were released by adult corals. Both A. tenuis and P. damicornis released similar bacteria, and the genera Alteromonas and Roseobacter were abundant in large proportions in the seawater of both species after reproduction. This study suggests that adult corals may release bacteria with their offspring to benefit the fitness in early coral life stages.     

Presence of Culturable Bacteria in Cocoons of the Earthworm Eisenia fetida

Viable bacteria were found to coexist with developing embryos in egg capsules (cocoons) of the earthworm Eisenia fetida. Earthworms were reared under standardized conditions, and bacterial densities were measured in distinct batches of cocoons collected weekly for 10 weeks. Cocoons weighing 12 mg contained a mean viable bacterial population of approximately 10⁸ CFU/g of cocoons. No difference was found in viable counts obtained from cocoons incubated at 15°C and cocoons incubated at 24°C. Viable bacterial numbers increased with cocoon age, while acridine orange direct counts of microbial cells were stable at approximately 10⁹ cells per g of cocoons. Bacteria isolated from cocoons were used to develop antisera in rabbits for the production of strain-specific fluorescent antibodies. Fluorescent antibody and selective plating techniques were used to monitor populations of these bacteria in earthworm bedding and to determine whether cocoons acquire bacteria from the environment in which they are formed. Cocoon isolates were readily recovered from cocoons formed in inoculated bedding at densities of 10⁸ CFU/g of cocoons. Bradyrhizobium japonicum USDA 110 and UMR 161 added to bedding were also recovered from cocoons, but at lower densities than cocoon isolates. Escherichia coli K-12(pJP4) inoculum was recovered from bedding but not from cocoons. The bacterial complement of Eisenia fetida cocoons is affected by inoculation of selected bacterial isolates in the worm growth environment.     

Aberrant structures of fecal bacterial community in allergic infants profiled by 16S rRNA gene pyrosequencing

We investigated the correlation between fecal bacteria composition in early infancy and the prevalence of allergic diseases in late infancy. The fecal microbiota in the first 2?months was profiled using the 16S rRNA V6 short-tag sequences in the community and statistically compared between two groups of subjects who did and did not show allergic symptoms in the first 2?years (n?=?11 vs. 11). In the allergic group, genus Bacteroides at 1?month and genera Propionibacterium and Klebsiella at 2?months were more abundant, and genera Acinetobacter and Clostridium at 1?month were less abundant than in the nonallergic group. Allergic infants who showed high colonization of Bacteroides and/or Klebsiella showed less colonization of Clostridium perfringens/butyricum, suggesting antagonism between these bacterial groups in the gastrointestinal tract. It was also remarkable that the relative abundance of total Proteobacteria, excluding genus Klebsiella, was significantly lower in the allergic than in the nonallergic group at the age of 1?month. These results indicate that pyrosequence-based 16S rRNA gene profiling is valid to find the intestinal microbiotal disorder that correlates with allergy development in later life.     

云南省富宁磁铁矿矿区可培养细菌多样性初步研究

目的对云南富宁磁铁矿矿区样品中可培养细菌进行分离并对其多样性进行了初步研究。方法采集云南富宁磁铁矿矿区土样和矿石样,采用固体肉汤培养基、卵黄培养基及PYGV培养基分离该矿区环境中的可培养细菌,利用16SrRNA基因序列分析构建系统发育树,并统计不同种属细菌的数量,初步评估细菌多样性。结果富宁磁铁矿矿区环境细菌的主要种群包括厚壁菌门、放线菌门和变形菌门的不同菌属：芽孢杆菌属、葡萄球菌属、节杆菌属和假单胞菌属的菌株,其中抗逆性较强的优势菌群为厚壁菌门的芽孢杆菌。结论本研究初步表明富宁磁铁矿矿区可培养细菌种类具有一定的多样性。