Novel spirochetes in the crystalline style of fresh water gastropods

Freshwater gastropods of the families Amnicolidae, Bithyniidae, Baicaliidae, and Benedictiidae are shown for the first time to harbor spirochetes associated with the crystalline style in the intestinal tract. The examined gastropod species are omnivorous, phyto-detritophagous grazers or filter-feeders. Their habitats are various water bodies and biotopes, including deep water hydrothermal vents and gas hydrate zones in Lake Baikal.     

First report on bacteria of the family <Emphasis Type="Italic">Spirochaetaceae</Emphasis> from digestive tract of endemic gastropods from Lake Baikal

Detection of bacteria of the family Spirochaetaceae in the crystalline style of 11 species of endemic gastropods from Lake Baikal is reported. Investigation by transmission and scanning electron microscopy showed that these spirochetes belonged to the genus Cristispira.     

Phylogenetic position and in situ identification of ectosymbiotic spirochetes on protists in the termite gut

Phylogenetic relationships, diversity, and in situ identification of spirochetes in the gut of the termite Neotermes koshunensis were examined without cultivation, with an emphasis on ectosymbionts attached to flagellated protists. Spirochetes in the gut microbial community investigated so far are related to the genus Treponema and divided into two phylogenetic clusters. In situ hybridizations with a 16S rRNA-targeting consensus oligonucleotide probe for one cluster (known as termite Treponema cluster I) detected both the ectosymbiotic spirochetes on gut protists and the free-swimming spirochetes in the gut fluid of N. koshunensis. The probe for the other cluster (cluster II), which has been identified as ectosymbionts on gut protists of two other termite species, Reticulitermes speratus and Hodotermopsis sjoestedti, failed to detect any spirochete population. The absence of cluster II spirochetes in N. koshunensis was confirmed by intensive 16S ribosomal DNA (rDNA) clone analysis, in which remarkably diverse spirochetes of 45 phylotypes were identified, almost all belonging to cluster I. Ectosymbiotic spirochetes of the three gut protist species Devescovina sp., Stephanonympha sp., and Oxymonas sp. in N. koshunensis were identified by their 16S rDNA and by in situ hybridizations using specific probes. The probes specific for these ectosymbionts did not receive a signal from the free-swimming spirochetes. The ectosymbionts were dispersed in cluster I of the phylogeny, and they formed distinct phylogenetic lineages, suggesting multiple origins of the spirochete attachment. Each single protist cell harbored multiple spirochete species, and some of the spirochetes were common among protist species. The results indicate complex relationships of the ectosymbiotic spirochetes with the gut protists.     

Prevalence of the Lyme disease spirochete in populations of white-tailed deer and white-footed mice

The prevalence of the Ixodes dammini spirochete (IDS) in white-tailed deer (Odocoileus virginianus) and white-footed mice (Peromyscus leucopus) was studied on the eastern end of Long Island, New York. Both species commonly occur in a variety of habitats, are preferred hosts of Ixodes dammini, and can harbor the spirochetes in the blood. Each animal was examined for spirochetemia, tick infestation, and IDS infection rates in the ticks that were removed from it. The results obtained suggest that in winter deer can be infected by questing adult I. dammini. Adult ticks apparently are infected through transtadial transmission of spirochetes from subadult ticks which had fed earlier in their life history on infected animals. Deer are important hosts of adult ticks and the IDS in winter and probably are a reservoir host in other seasons. The patterns of spirochete prevalence suggest that deer and mice are reservoirs of the organism and thus are fundamental to the ecology of Lyme disease on Long Island.     

Dynamic effects of ground-layer plant communities on beetles in a fragmented farming landscape

Vegetation effects on arthropods are well recognized, but it is unclear how different vegetation attributes might influence arthropod assemblages across mixed-agricultural landscapes. Understanding how plant communities influence arthropods under different habitat and seasonal contexts can identify vegetation management options for arthropod biodiversity. We examined relationships between vegetation structure, plant species richness and plant species composition, and the diversity and composition of beetles in different habitats and time periods. We asked: (1) What is the relative importance of plant species richness, vegetation structure and plant composition in explaining beetle species richness, activity-density and composition? (2) How do plant-beetle relationships vary between different habitats over time? We sampled beetles using pitfall traps and surveyed vegetation in three habitats (woodland, farmland, their edges) during peak crop growth in spring and post-harvest in summer. Plant composition better predicted beetle composition than vegetation structure. Both plant richness and vegetation structure significantly and positively affected beetle activity-density. The influence of all vegetation attributes often varied in strength and direction between habitats and seasons for all trophic groups. The variable nature of plant-beetle relationships suggests that vegetation management could be targeted at specific habitats and time periods to maximize positive outcomes for beetle diversity. In particular, management that promotes plant richness at edges, and promotes herbaceous cover during summer, can support beetle diversity. Conserving ground cover in all habitats may improve activity-density of all beetle trophic groups. The impacts of existing weed control strategies in Australian crop margins on arthropod biodiversity require further study.     

Winning the biodiversity arms race among freshwater gastropods: competition and coexistence through shell variability and predator avoidance

Explanations for the coexistence of many closely related species in inland waters continue to be generated more than 50 years after Hutchinson’s question: why are there so many kinds of animals? This review focuses on the hypothesis that high species diversity of freshwater gastropods results, in part, from predators maintaining biodiversity across a range of deep- and shallow-water habitats. Invertebrate predators, such as aquatic insects, and leeches consume soft tissue of pulmonate snails by penetrating shells of various shapes and sizes. Crayfish and large prawns chip around the shell aperture to enter thick shells and crush small shells with their mandibles. Crabs use their strong chelae to crush thin and thick shells. Fishes with pharyngeal teeth are major shell-breaking predators that combine with other vertebrate predators such as turtles and wading birds to increase the diversity of gastropod communities by regulating the abundance of dominant species. Although the generalized diets of most freshwater predators preclude tight co-evolutionary patterns of responses, there are combinations of predators that modify gastropod behavior and shell morphology in aquatic assemblages of different ages and depths. This combination of invertebrate and vertebrate predatory impacts led to competitive advantages among individual gastropods with different adaptations: (1) less vulnerable shell morphologies and sizes; (2) predator-avoidance behaviors; or (3) rapid and widespread dispersal with variable life histories. Some individuals develop thicker and/or narrow-opening shells or shells with spines and ridges. Other thin-shelled species crawl out of the water or burrow to lower their risk to shell-breaking or shell-entering predators. Some alter their age at first reproduction and grow rapidly into a size refuge. Fluctuations in water levels and introductions of non-native species can change competitive dominance relationships among gastropods and result in major losses of native species. Many different gastropod predators control species that are human disease vectors. Most snails and their predators provide other ecosystem services such as nutrient cycling and transfer of energy to higher trophic levels. Their persistence and diversity of native species require adaptive management and coordinated study.     

Trophic plasticity,environmental gradients and food‐web structure of tropical pond communities

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Cotransmission of divergent relapsing fever spirochetes by artificially infected Ornithodoros hermsi

The soft tick Ornithodoros hermsi, which ranges in specific arboreal zones of western North America, acts as a vector for the relapsing fever spirochete Borrelia hermsii. Two genomic groups (genomic group I [GGI] and GGII) of B. hermsii are differentiated by multilocus sequence typing yet are codistributed in much of the vector's range. To test whether the tick vector can be infected via immersion, noninfected, colony-derived O. hermsi larvae were exposed to reduced-humidity conditions before immersion in culture suspensions of several GGI and GGII isolates. We tested for spirochetes in ticks by immunofluorescence microscopy and in mouse blood by quantitative PCR of the vtp locus to differentiate spirochete genotypes. The immersed larval ticks were capable of spirochete transmission to mice at the first nymphal feeding. Tick infection with mixed cultures of isolates DAH (vtp-6) (GGI) and MTW-2 (vtp-5) (GGII) resulted in ticks that caused spirochetemias in mice consisting of MTW-2 or both DAH and MTW-2. These findings show that this soft tick species can acquire B. hermsii by immersion in spirochete suspensions, that GGI and GGII isolates can coinfect the tick vector by this method, and that these spirochetes can be cotransmitted to a rodent host.     

Phylogenetic Position and In Situ Identification of Ectosymbiotic Spirochetes on Protists in the Termite Gut

Phylogenetic relationships, diversity, and in situ identification of spirochetes in the gut of the termite Neotermes koshunensis were examined without cultivation, with an emphasis on ectosymbionts attached to flagellated protists. Spirochetes in the gut microbial community investigated so far are related to the genus Treponema and divided into two phylogenetic clusters. In situ hybridizations with a 16S rRNA-targeting consensus oligonucleotide probe for one cluster (known as termite Treponema cluster I) detected both the ectosymbiotic spirochetes on gut protists and the free-swimming spirochetes in the gut fluid of N. koshunensis. The probe for the other cluster (cluster II), which has been identified as ectosymbionts on gut protists of two other termite species, Reticulitermes speratus and Hodotermopsis sjoestedti, failed to detect any spirochete population. The absence of cluster II spirochetes in N. koshunensis was confirmed by intensive 16S ribosomal DNA (rDNA) clone analysis, in which remarkably diverse spirochetes of 45 phylotypes were identified, almost all belonging to cluster I. Ectosymbiotic spirochetes of the three gut protist species Devescovina sp., Stephanonympha sp., and Oxymonas sp. in N. koshunensis were identified by their 16S rDNA and by in situ hybridizations using specific probes. The probes specific for these ectosymbionts did not receive a signal from the free-swimming spirochetes. The ectosymbionts were dispersed in cluster I of the phylogeny, and they formed distinct phylogenetic lineages, suggesting multiple origins of the spirochete attachment. Each single protist cell harbored multiple spirochete species, and some of the spirochetes were common among protist species. The results indicate complex relationships of the ectosymbiotic spirochetes with the gut protists.     

Real-time high resolution 3D imaging of the lyme disease spirochete adhering to and escaping from the vasculature of a living host

Pathogenic spirochetes are bacteria that cause a number of emerging and re-emerging diseases worldwide, including syphilis, leptospirosis, relapsing fever, and Lyme borreliosis. They navigate efficiently through dense extracellular matrix and cross the blood-brain barrier by unknown mechanisms. Due to their slender morphology, spirochetes are difficult to visualize by standard light microscopy, impeding studies of their behavior in situ. We engineered a fluorescent infectious strain of Borrelia burgdorferi, the Lyme disease pathogen, which expressed green fluorescent protein (GFP). Real-time 3D and 4D quantitative analysis of fluorescent spirochete dissemination from the microvasculature of living mice at high resolution revealed that dissemination was a multi-stage process that included transient tethering-type associations, short-term dragging interactions, and stationary adhesion. Stationary adhesions and extravasating spirochetes were most commonly observed at endothelial junctions, and translational motility of spirochetes appeared to play an integral role in transendothelial migration. To our knowledge, this is the first report of high resolution 3D and 4D visualization of dissemination of a bacterial pathogen in a living mammalian host, and provides the first direct insight into spirochete dissemination in vivo.     

Spirosymplokos deltaeiberi nov. gen., nov. sp.: variable-diameter composite spirochete from microbial mats

Large (up to 100 m long), loosely coiled, free-living spirochetes with variable diameters (from 0.4 to 3 m in the same cell) were seen at least 40 times between August 1990 and January 1993. These spirochetes were observed in mud water and enrichment media from highly specific habitats in intertidal evaporite flats at three disjunct localities, one in Spain and two in Mexico. All three are sites of commerical saltworks. Associated with Microcoleus chthonoplastes, the large spirochetes from Spain display phototaxis and a composite organization. Shorter and smaller-diameter spirochetes are seen inside both healthy and spent periplasm of larger ones. Small spirochetes attached to large ones have been observed live. From two to twelve spirochete protoplasmic cylinders were seen inside a single common outer membrane. A distinctive granulated cytoplasm in which the granules are of similar diameter (20–32 nm) to that of the flagella (26 nm) was present. Granule diameters were measured in thin section and in negatively-stained whole-mount preparations. Based on their ultrastructure, large size, variable diameter, number of flagella (3 to 6), and phototactic behavior these unique spirochetes are formally named Spirosymplokos deltaeiberi. Under anoxic (or low oxygen) conditions they formed blooms in mixed culture in media selective for spirochetes. Cellobiose was the major carbon source in 80% seawater, the antibiotic rifampicin was added, mat from the original field site was present and tubes were incubated in the light at from 18–31 °C. Within 1–2 weeks populations of the large spirochete developed at 25 °C but they could not be transferred to fresh medium.     

Habitat specialization in tropical continental shelf demersal fish assemblages

The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth), down the fore reef slope to the reef base (10-30 m depth) then across the adjacent continental shelf (30-110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected habitats through which fish can migrate.     

Fish larvae distribution among different habitats in coastal East Africa

Fish larvae abundances, diversity and trophic position across shallow seagrass, coral reef and open water habitats were examined to characterize their distribution in coastal East Africa. Larvae were identified to family and analysed for abundance differences between sites and habitats, trophic level using stable-isotope analysis and parental spawning mode. Abundances differed greatly between sites with the highest numbers of larvae occurring in the open-water and seagrass habitats. Larval fish diversity was high across habitats with 51 families identified with small differences between sites and among habitats. Notably, larvae of abundant large herbivorous fishes present in reef and seagrass habitats were almost completely absent at all sampling locations. In the seagrass, demersal spawned larvae were more abundant compared with the reef and open-water habitats. Stable-isotope analysis revealed that fish larvae have a varied diet, occupying trophic level two to three and utilizing planktonic prey. This study offers new insights into distributional aspects of fish larvae along the East African coast where such information is sparse.     

16S rDNA sequence and phylogenetic position of an uncultivated spirochete from the hindgut of the termite Mastotermes darwiniensis Froggatt

Abstract We have analyzed the 16S rDNA sequence and the phylogenetic position of an uncultivated spirochete from the hindgut contents of the Australian termite Mastotermes darwiniensis Froggatt. The 16S rRNA genes of bacteria from the hindgut contents of Mastotermes darwiniensis were amplified by polymerase chain reaction. The amplification products were cloned and sequenced. The sequences were compared to known homologous primary structures. Two of the clones (MDS1 and MDS3) had an insert of 1498 nucleotides showing typical signatures of spirochete 16S rRNA sequences. The sequences of the two clones were most similar to the 16S rRNA sequence of Spirochaeta stenostrepta (89.8%) and Treponema sp. strain H1 (90.7%). Phylogenetical analysis positioned the hindgut spirochete sequence with that of the free-living anaerobic Spirochaeta stenostrepta and Treponema sp. strain H1 as its nearest relatives within the cluster of the spirochetes. We conclude that the analyzed SSU rDNA sequences originate from a spirochete related to the genus Treponema . It is possibly one of the uncultivated unique spirochetes symbiotic in termite hindguts.     

Influence of lateral gradients of hydrologic connectivity on trophic positions of fishes in the Upper Mississippi River

1. Riverscapes consist of the main channel and lateral slackwater habitats along a gradient of hydrological connectivity from maximum connection in main channel habitats to minimum connection in backwaters. Spatiotemporal differences in water currents along this gradient produce dynamic habitat conditions that influence species diversity, population densities and trophic interactions of fishes. 2. We examined the importance of lateral connectivity gradients for food web dynamics in the Upper Mississippi River during spring (high flow, moderately low temperatures) and summer (low flow, higher temperatures). We used literature information and gut contents analyses to determine feeding guilds and stable isotope analysis to estimate mean trophic position of local fish assemblages. During June and August 2006, we collected over 1000 tissue samples from four habitats (main channel, secondary channels, tertiary channels and backwaters) distributed within four hydrologic connectivity gradients. 3. Mean trophic position differed among feeding guilds and seasons, with highest values in spring. Mean trophic position of fish assemblages, variability in trophic position and food chain length (maximum trophic position) of the two dominant piscivore species (Micropterus salmoides and M. dolomieu) in both seasons were significantly associated with habitat along the lateral connectivity gradient. Food chain length peaked in tertiary channels in both seasons, probably due to higher species diversity of prey at these habitats. We infer that food chain length and trophic position of fish assemblages were lower in backwater habitats in the summer mainly because of the use of alternative food sources in these habitats. 4. A greater number of conspecifics exhibited significant among‐habitat variation in trophic position during the summer, indicating that low river stages can constrain fish movements in the Upper Mississippi River. 5. Results of this study should provide a better understanding of the fundamental structure of large river ecosystems and an improved basis for river rehabilitation and management through knowledge of the importance of lateral complexity in rivers.     

Genetic variation at the vlsE locus of Borrelia burgdorferi within ticks and mice over the course of a single transmission cycle

The Lyme disease spirochete, Borrelia burgdorferi, causes a persistent infection in the vertebrate host even though infected animals mount an active immune response against the spirochete. One strategy used by the spirochete to evade vertebrate host immunity is to vary the structure and expression of outer membrane antigens. The vlsE locus represents the best-studied example of antigenic variation in B. burgdorferi. During vertebrate host infection, recombination between the active vlsE locus and silent, partial vlsE copies leads to gene conversion events and the generation of novel alleles at the expression site. In the present study, we followed a population of B. burgdorferi organisms moving through vertebrate host and tick stages to complete one transmission cycle. The major goal of the study was to determine if the vlsE locus was subject to different selective pressure and/or recombination frequency at different stages of the spirochete's life cycle. We report here that the vlsE genetic diversity generated within the rodent host was maintained through the larval and nymphal tick stages. Therefore, naturally infected ticks are likely to transmit spirochete populations with multiple vlsE alleles into naive vertebrate hosts. Although vlsE genetic diversity in mice was maintained through tick stages, the dominant vlsE alleles were different between tick stages as well as between individual ticks. We propose that population-level bottlenecks experienced by spirochetes, especially during the larval-to-nymphal molt, are responsible for individual infected ticks harboring different dominant vlsE alleles. Although vlsE genetic diversity is maintained through tick stages, the VlsE protein is unlikely to be of functional importance in the vector, because the protein was expressed by very few (<1%) bacteria in the vector.     

Epibenthic gastropods of the middle Florida keys: the role of habitat and environmental stress on assemblage composition

A survey of epibenthic prosobranch gastropods was undertaken in both seagrass and hard substratum (coral or old reef rock) habitats on opposite sides of the Florida Keys (Florida Bay and Hawk Channel) to compare faunal differences attributable to differences in the above two habitats and environments. Additionally, two data sets (26 continuous months) of daytime dissolved oxygen, surface salinity and water temperature from Florida Bay (Long Key) and Hawk Channel (Key Largo) environments were compared to determine differences that might constitute environmental stresses likely to affect the fauna. The above data were collected to determine if several hypotheses concerning effects of stress on organisms, assemblage, community and faunal composition were consistent with data on assemblage structure. These hypotheses were that: (1) stress should reduce the average size of organisms; (2) shorten food chains; (3) reduce predation intensity; (4) reduce species richness and diversity; and (5) increase the relative abundance of predator-susceptible ancestral species (i.e. Archaegastropoda). Water quality data suggest that the two most likely forms of stress in deeper (>1 m) areas of Florida Bay adjacent to the Keys are cold water temperatures associated with winter cold fronts and low predawn oxygen associated with warm summer temperatures, high salinity, and periodic algal and seagrass drift buildups. Seagrass sites had high population densities and low diversity due to the dominance of Astraea americana Gmelin (American star shell) in Florida Bay and Modulus modulus L. in Hawk Channel seagrass habitats. Florida Bay sites had high species richness on a small spatial scale, but Hawk Channel sites had more species and greater encounter rates of new species on a larger scale. Predawn oxygen measurements taken during July in four habitats were positively correlated with prosobranch species richness and diversity. Faunal data, analysed on a population density basis, fit the above hypotheses of body size, trophic level, and evolutionary age of the species. Attempts to measure predation on an experimental prosobranch (A. americana) were unsuccessful but a tethering experiment with a sea urchin (Echinometra lucunter L.) indicated higher predation in the less stressful Hawk Channel than Florida Bay hard substratum sites. Stress appears to reduce the abundance of higher trophic levels (both prosobranch and finfish predators) resulting in the dominance of ancestral forms not adapted to predation but tolerant of environmental stress. Eutrophication or increased oxygen demands in Florida Bay could result in further species richness and diversity declines.     

山东东营和烟台潮间带海草床食物网结构特征

为了探明海草床内主要生物类群间的营养关系以及食物网结构, 作者于2018年8月分别在东营黄河口潮间带和烟台西海岸潮间带海草床采集大型底栖生物样品, 采用δ ¹³C和δ ¹⁵N稳定同位素方法, 对生物样品的碳、氮同位素组成进行了测定和分析。结果表明: 东营海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-21.99‰至-12.13‰和5.23‰-11.05‰, 烟台海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-18.11‰至-14.06‰和6.60‰-10.22‰。东营海草床主要生物的营养级范围为2.00-3.85, 烟台海草床主要生物的营养级范围为2.00-3.15。根据δ ¹⁵N值计算所得的营养级图分析可知两区域海草床内初级消费者主要为滤食性双壳类和多毛类, 次级消费者为植食性或杂食性甲壳类,肉食性鱼类和腹足类。与近海海域大型底栖生物食物网相比, 海草床内底栖生物的营养级均值普遍较低。     

Rifampin-resistant RNA polymerase in spirochetes

Abstract Various free-living and host-associated spirochetes isolated by methods not involving rifampin were resistant to relatively high concentrations of this antibiotic. The lowest concentrations of rifampin that were inhibitory for the spirochetes ranged from 50 to more than 200 μ g/ml, depending on the species. The spirochete strains examined were at least 10-fold more resistant to rifampin than Escherichia coli and 10 000-fold more resistant than Staphylococcus aureus . The results support the conclusion that rifampin resistance is a general characteristic of spirochetes. Resistance of Spirochaeta aurantia to rifampin was not the result of detoxification of the antibiotic in the culture medium. The activity of spirochete DNA-dependent RNA polymerase in vitro was completely resistant to 10 μg of rifampin per ml, a concentration that totally inhibited E. coli RNA polymerase. Higher concentrations decreased the spirochetal activity. Thus, rifampin resistance may be due to a low affinity of spirochete RNA polymerase for the antibiotic.     

Carotenoid pigments of facultatively anaerobic spirochetes.

Carotenoid pigments were purified from a previously undescribed, red, halophilic spirochete (spirochete RS1), and from Spirochaeta aurantia strain J1. Both spirochetes are facultative anaerobes and produce pigments when growing aerobically. The major pigments of the two spirochetes were identified by means of chromatographic analysis, absorption spectroscopy, hydride reduction, acetylation and silylation experiments, and mass spectrometry. It was concluded that the major pigment from spirochete RS1 was 4-keto-1',2'-dihydro-1'-hydroxytorulene. This conclusion was further supported by infrared spectroscopy and additional analytical data. The evidence showed that the major pigment from S. aurantia was 1',2'-dihydro-1'-hydroxytorulene. Chromatographic and spectrophotometric evidence indicated that this pigment was also present, as a minor carotenoid component, in spirochete RS1. These pigments have been previously detected almost exclusively in gliding bacteria, such as species of Flexibacter, Stigmatella, and Myxococcus. The occurrence of 4-keto-1',2'-dihydro-1'-hydroxytorulene and 1',2'-dihydro-1'-hydroxytorulene in both spirochetes and gliding bacteria may have significance with respect to the evolutionary development of these organisms.