Ecological succession of fungal and bacterial communities in Antarctic mosses affected by a fairy ring disease

Extremophiles - We evaluated fungal and bacterial diversity in an established moss carpet on King George Island, Antarctica, affected by ‘fairy ring’ disease using metabarcoding. A...     

Abrupt induction of GDP-fucose: Asialo GM1 fucosyltransferase in the small intestine after conventionalization of germ-free mice

We studied the time-course of the induction of GDP-fucose: asialo GM1 fucosyltransferase and its product, i.e. fucosyl asialo GM1, of the small intestine after introduction of microorganisms to germ-free mice (conventionalization). We found that the fucosyltransferase activity was abruptly induced and asialo GM1 was converted into fucosyl asialo GM1 within a few days after conventionalization. However, two weeks after conventionalization this enzyme activity dropped to approximately 10^?2 level of the maximum value and asialo GM1 appeared again as one of the major glycolipids. These results showed that the microbial colonization in the gut evoked a drastic change of the glycolipid pattern at the intestinal epithelial cell-surface via the induction of a fucosyltransferase.     

Ecological succession in long-term experimentally evolved biofilms produces synergistic communities

Many biofilm populations are known for their exceptional biodiversity, but the relative contributions of the forces that could produce this diversity are poorly understood. This uncertainty grows in the old, well-established communities found on many natural surfaces and in long-term, chronic infections. If the prevailing interactions among species within biofilms are positive, productivity should increase with diversity, but if they tend towards competition or antagonism, productivity should decrease. Here, we describe the parallel evolution of synergistic communities derived from a clone of Burkholderia cenocepacia during ∼1500 generations of biofilm selection. This long-term evolution was enabled by a new experimental method that selects for daily cycles of colonization, biofilm assembly and dispersal. Each of the six replicate biofilm populations underwent a common pattern of adaptive morphological diversification, in which three ecologically distinct morphotypes arose in the same order of succession and persisted. In two focal populations, mixed communities were more productive than any monoculture and each variant benefited from the mixture. These gains in output resulted from asymmetrical cross-feeding between ecotypes and the expansion and partitioning of biofilm space that constructed new niches. Therefore, even in the absence of starting genetic variation, prolonged selection for surface colonization generates a dynamic of ecological succession that enhances productivity.     

Allogenic succession of marine bacterial communities in response to pharmaceutical waste

Vibrio spp. predominated in the culturable bacterial community of surface waters of the Puerto Rico Trench at the site of disposal for nearly ten years of pharmaceutical wastes. In this area and surrounding waters as far as 1000 km north of the dumpsite and south into the Caribbean Sea, Vibrio spp. comprised up to 100% of the culturable bacteria, with Acinetobacter spp. being the second most prevalent group. Pseudomonas spp., reported to be common in these waters a decade earlier, were virtually absent from all samples examined during a three year study involving 9 cruises. Staphylococcus spp. were also found in water samples collected within the dumpsite. Using cultures isolated from surface water samples collected at the dumpsite, laboratory experiments confirmed that pharmaceutical waste can enrich for Vibrio spp., in preference to Pseudomonas spp., with growth of the strains proportional to the amount of waste added.     

Allogenic succession of marine bacterial communities in response to pharmaceutical waste

Vibrio spp. predominated in the culturable bacterial community of surface waters of the Puerto Rico Trench at the site of disposal for nearly ten years of pharmaceutical wastes. In this area and surrounding waters as far as 1000 km north of the dumpsite and south into the Caribbean Sea, Vibrio spp. comprised up to 100% of the culturable bacteria, with Acinetobacter spp. being the second most prevalent group. Pseudomonas spp., reported to be common in these waters a decade earlier, were virtually absent from all samples examined during a three year study involving 9 cruises. Staphylococcus spp. were also found in water samples collected within the dumpsite. Using cultures isolated from surface water samples collected at the dumpsite, laboratory experiments confirmed that pharmaceutical waste can enrich for Vibrio spp., in preference to Pseudomonas spp., with growth of the strains proportional to the amount of waste added.     

Phylogenetic structure of angiosperm communities during tropical forest succession

The phylogenetic structure of ecological communities can shed light on assembly processes, but the focus of phylogenetic structure research thus far has been on mature ecosystems. Here, I present the first investigation of phylogenetic community structure during succession. In a replicated chronosequence of 30 sites in northeastern Costa Rica, I found strong phylogenetic overdispersion at multiple scales: species present at local sites were a non-random assemblage, more distantly related than chance would predict. Phylogenetic overdispersion was evident when comparing the species present at each site with the regional species pool, the species pool found in each age category to the regional pool or the species present at each site to the pool of species found in sites of that age category. Comparing stem size classes within each age category, I found that during early succession, phylogenetic overdispersion is strongest in small stems. Overdispersion strengthens and spreads into larger size classes as succession proceeds, corroborating an existing model of forest succession. This study is the first evidence that succession leaves a distinct signature in the phylogenetic structure of communities.     

Influence of conventionalization on small-intestinal mucosa of germ-free Wistar rats: quantitative light microscopic observations

Germ-free rats were inoculated with microbial flora from feces of conventionally reared rats and the mucosal structure was quantitatively observed at different time intervals after the inoculation and at different regions of the small intestine. In the ileum, desquamation figures were frequently seen on the villus tip, and several parameters of the mucosal elements, i.e., villus and crypt lengths, mitotic figures, goblet cells and thickness of lamina propria were significantly increased after the inoculation. On the other hand, in the duodenum and jejunum, such parameters except for the lamina propria showed no remarkable change during the course of the experiment, though the villus/crypt ratio increased temporarily at half a day after the inoculation. These regional differences of the mucosal response to the inoculation may be due to the different populations of microbial flora which settled in each region of the small intestine.     

Molecular analysis of bacterial community succession during prolonged compost curing

The compost environment consists of complex organic materials that form a habitat for a rich and diverse microbial community. The aim of this research was to study the dynamics of microbial communities during the compost-curing phase. Three different methods based on 16S rRNA gene sequence were applied to monitor changes in the microbial communities: (1) denaturing gradient gel electrophoresis of PCR-generated rRNA gene fragments; (2) partial rRNA gene clone libraries; and (3) a microarray of oligonucleotide probes targeting rRNA gene sequences. All three methods indicated distinctive community shifts during curing and the dominant species prevailing during the different curing stages were identified. We found a successional transition of different bacterial phylogenetic groups during compost curing. The Proteobacteria were the most abundant phylum in all cases. The Bacteroidetes and the Gammaproteobacteria were ubiquitous. During the midcuring stage, Actinobacteria were dominant. Different members of nitrifying bacteria and cellulose and macromolecule-degrading bacteria were found throughout the curing process. In contrast, pathogens were not detected. In the cured compost, bacterial population shifts were still observed after the compost organic matter and other biochemical properties had seemingly stabilized.     

rRNA‐based analysis to monitor succession of faecal bacterial communities in Holstein calves

Aims: To quantitatively analyse the faecal bacterial communities of Holstein calves and track their succession up to 12 weeks of age. Methods and Results: Faecal samples obtained from four female Holstein calves were analysed by the RNA‐based, sequence‐specific rRNA cleavage method. Twelve scissor probes covering major rumen bacterial groups were used, detecting c. 60–90% of the total 16S rRNAs. At 1 week of age, 16S rRNAs from members of the Bacteroides‐Prevotella group (40·0% of the total 16S rRNAs), Faecalibacterium (21·7%), the Clostridium coccoides–Eubacterium rectale group (16·7%) and the Atopobium cluster (10·9%) were detected at high levels. Throughout the 12‐week period, rRNAs of the Bacteroides‐Prevotella and the Cl. coccoides‐Eu. rectale groups constituted the major fraction of microbiota (c. 50–70% of the total). The relative abundances of the Atopobium cluster, Faecalibacterium, and some probiotic bacteria (such as those of the genera Lactobacillus and Bifidobacterium) decreased as the animal aged. Instead, an uncultivated rumen bacterial group, as well as Ruminococcus flavefaciens and Fibrobacter emerged at the detectable levels (1–2%) in the faeces sampled at a postweaning age. In addition, certain bacterial groups that were not covered by the probe suite increased as the animals aged. Conclusions: Young calves undergo dynamic changes in their intestinal bacterial community during the first 12 weeks of life. As young ruminants undergo metabolic and physiological development in their digestive tracts in the transition from a monogastric to a ruminant animal at an early age, the intestinal bacterial community may reflect such development. Significance and Impact of the Study: The succession of the bacterial communities in the faeces of calves was quantitatively monitored in the present study for the first time. The approach used here was demonstrated to be a useful means for determining the populations of predominant faecal bacterial groups in a variety of calf experiments in response to diet, stress and disease.     

Changes in the seasonal rhythm of two forest communities during secondary succession

Changes in the seasonal rhythm of two plant phytocoenoses in a submountain beech forest during secondary succession were studied. Investigations were done on four monitoring plots with different stand density over the period of four successive years. The rhythm of the associations Dentario bulbiferae-Fagetum and Carici pilosae-Fagetum reflects the course of succession processes running six years after the human impact (cutting) in the ecosystem. Results of the phenological observations of the understorey species with the focus on the changes in flowering and colour spectrum allowed to make the comparisons between both associations in connection with different phyto-climatic conditions and in dependence on time. The most conspicuous changes in the seasonal rhythm and structure of the examined associations were found in conditions of the former clear-cut, currently in succession phase. A clear decrease (56%) in number of taxons with the dominance > 1% in one association towards the end of the 4-year study period was detected here. Simultaneously, a decrease in the number of flowering species was observed, while the relative rate of species being in the vegetative stage increased considerably (from 6 to 67%) over the growing season. The course of flowering of both of the associations missed discernible trends and peaks as well as colour spectra were partially changed during four monitored successive years on the formerly unstocked area.     

Evidence for community assembly constraints during succession in dune slack plant communities

Community assembly during succession can be constrained by both local and regional factors. Despite an increasing regional species pool size during succession, we found a limit on the number of species in 1 × 1 m plots in dune slacks. Three alternative hypotheses (habitat heterogeneity, dispersal limitation and niche limitation) explaining this community saturation were tested. A null model analysis showed that species richness in the plots had an unusually low variance suggesting that beta habitat diversity was not likely to explain the limitation on species richness. Because we did not find a correlation between the distribution of species over the slack and their dispersal capacity, we also excluded the dispersal limitation hypothesis. Finally, a guild proportionality analysis revealed that the abundances of forb, graminoid and ruderal species showed low an unusually low variance over all age classes involved. This provides evidence for nonrandom community assembly during succession, likely to be determined by competitive exclusion among species of the same guild.     

Phylogenetic analysis of the succession of bacterial communities in the Great South Bay (Long Island)

Bacterial community composition and succession were examined over the course of the summer season in the Great South Bay, Long Island, NY, USA, using a 16S rDNA clone library approach. There was a progression of changes in dominant species in the libraries during the summer of 1997. The July library had several groups dominant, the SAR407 relatives of the alpha-Proteobacteria (24%) and the SAR86 (18%), sulfur-oxidizing symbiont relatives (8%) of the gamma-Proteobacteria, and unidentified Cytophaga-Flexibacter representatives (22%). In August, the Cytophaga-Flexibacter (Gelidibacter sp. and unidentified Cytophaga-Flexibacter representative) and Cyanobacteria (Synechococcus sp.) increased to 28% and 14%, respectively. High GC Gram-positives appeared at 18%, and beta-Proteobacteria (Ralstonia sp.) at 10%. By September these groups had either declined or were absent, while the SAR86 cluster, Pseudoalteromonas and Alteromonas of the gamma-Proteobacteria were dominant in the community (61%). The dominance of open ocean bacteria along with the presence of Aureococcus anophagefferens (Pelagophyceae) in July suggests possible open ocean coupling to bloom events. Many clones in this study were related to previously described clones from a wide distribution of marine environments, substantiating the cosmopolitan nature of pelagic bacteria. Only one isolated bacterium was closely related to 16S rDNA found in the August library.     

Ecological succession among iron-oxidizing bacteria

Despite over 125 years of study, the factors that dictate species dominance in neutrophilic iron-oxidizing bacterial (FeOB) communities remain unknown. In a freshwater wetland, we documented a clear ecological succession coupled with niche separation between the helical stalk-forming Gallionellales (for example, Gallionella ferruginea) and tubular sheath-forming Leptothrix ochracea. Changes in the iron-seep community were documented using microscopy and cultivation-independent methods. Quantification of Fe-oxyhydroxide morphotypes by light microscopy was coupled with species-specific fluorescent in situ hybridization (FISH) probes using a protocol that minimized background fluorescence caused by the Fe-oxyhydroxides. Together with scanning electron microscopy, these techniques all indicated that Gallionellales dominated during early spring, with L. ochracea becoming more abundant for the remainder of the year. Analysis of tagged pyrosequencing reads of the small subunit ribosomal RNA gene (SSU rRNA) collected during seasonal progression supported a clear Gallionellales to L. ochracea transition, and community structure grouped according to observed dominant FeOB forms. Axis of redundancy analysis of physicochemical parameters collected from iron mats during the season, plotted with FeOB abundance, corroborated several field and microscopy-based observations and uncovered several unanticipated relationships. On the basis of these relationships, we conclude that the ecological niche of the stalk-forming Gallionellales is in waters with low organic carbon and steep redoxclines, and the sheath-forming L. ochracea is abundant in waters that contain high concentrations of complex organic carbon, high Fe and Mn content and gentle redoxclines. Finally, these findings identify a largely unexplored relationship between FeOB and organic carbon.     

C. parvum in germ-free mice

Summary The effect of previous sensitization to C. parvum, by cross-reacting antigens from other bacteria, on the immunostimulatory effects of C. parvum treatment were studied in germ-free and conventional mice. It was found that the development of splenomegaly and specific delayed hypersensitivity following C. parvum injection were similar in both germ-free mice and conventional mice.Supported by U.S. Public Health Service Grant No. 5S07 RR05705 and NIH Grant no. AM 18530Visiting Investigator. Present address: Department of Experimental Immunobiology, The wellcome Research Laboratories Beckenham, Kent, England.Recipient of a post-doctoral fellowship from the National Foundation for Ileitis and Colitis Inc.Recipient of Research Career Development Award No. AM 0073 from the National Institute of Arthritis, Metabolism and Digestive Diseases     

Use of germ-free mice in experimental transplantation

A comparative study of skin allografts was performed in germ-free A/Ola mice kept in boxes and in A/Ola and BALB mice raised in ordinary conditions. Skin graft (of C57B1/6 mice) in A/Ola and BALB mice raised in ordinary conditions was shown to reject 16-21 and 12-18 days after the transplantation, respectively without cyclophosphamide (CP) use. CP application in BALB mice, grown in ordinary conditions, prolonged the lifespan of grafts to 12-29 days. The use of CP in germ-free A/Ola mice prolonged the lifespan of grafts to 19-39 days. In germ-free mice kept in boxes the use of an immunodepressant was not accompanied by infectious complications, while the animals kept in the vivarium often died of infectious diseases.     

Properties of native plant communities do not determine exotic success during early forest succession

Considerable research has been devoted to understanding how plant invasions are influenced by properties of the native community and to the traits of exotic species that contribute to successful invasion. Studies of invasibility are common in successionally stable grasslands, but rare in recently disturbed or seral forests. We used 16 yr of species richness and abundance data from 1 m² plots in a clearcut and burned forest in the Cascade Range of western Oregon to address the following questions: 1) is invasion success correlated with properties of the native community? Are correlations stronger among pools of functionally similar taxa (i.e. exotic and native annuals)? Do these relationships change over successional time? 2) Does exotic abundance increase with removal of potentially dominant native species? 3) Do the population dynamics of exotic and native species differ, suggesting that exotics are more successful colonists? Exotics were primarily annual and biennial species. Regardless of the measure of success (richness, cover, biomass, or density) or successional stage, most correlations between exotics and natives were non‐significant. Exotic and native annuals showed positive correlations during mid‐succession, but these were attributed to shared associations with bare ground rather than to direct biotic interactions. At peak abundance, neither cover nor density of exotics differed between controls and plots from which native, mid‐successional dominants were removed. Tests comparing nine measures of population performance (representing the pace, magnitude, and duration of population growth) revealed no significant differences between native and exotic species. In this early successional system, local richness and abundance of exotics are not explained by properties of the native community, by the presence of dominant native species, or by superior colonizing ability among exotics species. Instead natives and exotics exhibit individualistic patterns of increase and decline suggesting similar sets of life‐history traits leading to similar successional roles.     

Detection of viruslike particles in germ-free mice

Kajima, Masahiro (University of Notre Dame, Notre Dame, Ind.), and Morris Pollard. Detection of viruslike particles in germ-free mice. J. Bacteriol. 90:1448-1454. 1965.-Viruslike particles similar in structure to the mouse leukemia agent were detected by electron microscopy in thymus tissues of germ-free AK mice which had developed spontaneous leukemia. In addition, unique viruslike particles (type B) were detected in tissues from spontaneous mammary adenocarcinoma of germ-free C3H mice. Leukemia virus-like particles were also observed in the thymuses of the control AK mice and of the C3H control mice as well as of those with mammary tumors. Germ-free mice are not virus-free. The routes of transmission of leukemia as well as of mammary tumor viruses may be "vertical," through the embryo or placenta.