New species of dictyostelids from Patagonia and Tierra del Fuego, Argentina

In late Jan and early Feb 2005 samples for isolation of dictyostelid cellular slime molds (dictyostelids) were collected in five different provinces and from six national parks (all located 39-55°S) in Patagonia and Tierra del Fuego, Argentina. Southern beech (Nothofagus) forests represented the primary vegetation type investigated, but some samples were obtained from Patagonian steppe, alpine meadows, Valdivian temperate rainforests and coniferous forests dominated by Araucaria, Austrocedrus and Fitzroya. Among the dictyostelids isolated from the samples we collected were seven species new to science. These species (Dictyostelium austroandinum, D. chordatum, D. fasciculoideum, D. gargantuum, D. leptosomopsis, D. valdivianum and Polysphondylium patagonicum) are described herein on the basis of both morphology and molecular (SSU rDNA) data. One of the new species, D. gargantuum, is one of the largest representatives of the group reported to date. Another unusual species, D. chordatum, produces long interwoven sorocarps that do not appear to respond to a spacing gas similar to the condition first noted in D. implicatum.     

Dictyostelid cellular slime molds associated with grasslands of the central and western United States

Dictyostelid cellular slime molds (dictyostelids) associated with grassland ecosystems of the central and western United States were investigated at nine sites that included examples of the three major ecological types of grasslands (tall grass, mixed grass and short grass) generally recognized for the region. Samples of soil/humus collected from each site were examined with the Cavender method of isolating dictyostelids. For each of those six sites with well developed gallery forests present, an additional set of forest soil/humus samples was collected. A more intensive sampling effort was carried out at one site (Konza LTER) to assess the possible effects of burning and grazing on dictyostelid diversity and density. Twelve species of dictyostelids were recovered from grassland sites, whereas gallery forest sites yielded only nine species. Four cosmopolitan species (Dictyostelium giganteum, D. mucoroides, D. sphaerocephalum and Polysphondylium pallidum) were represented by the greatest densities of clones, with D. sphaerocephalum particularly common. The general pattern across all sites was that both species richness and density of dictyostelids decreased with decreasing precipitation. Samples collected from ungrazed grassland plots yielded higher numbers of both species and clones as compared to grazed plots, and the general pattern was for both values to increase as the interval between fires increased. For numbers of clones this correlation was statistically significant.     

Seasonal population changes of myxomycetes and associated organisms in four woodland soils

Abstract The number of myxomycete plasmodium-forming units (PFUs) and associated microorganisms in soils from four woodland sites in the West of England were estimated at approximately monthly intervals over the course of a year, and other characteristics of the soils were determined. The numbers of PFUs were low except in an unusual high-phosphate woodland soil. This soil contained the fewest dictyostelid slime moulds. Conversely, the woodland soil with most dictyostelids contained the fewest PFUs. Naked soil amoebae were the most abundant phagotrophs. Myxomycetes were a comparatively small component of the phagotrophic community of the three typical woodland soils. Changes in the populations of naked amoebae, ciliates, myxomycetes and dictyostelids were sometimes synchronized with changes in the bacterial populations, which showed 9–35-fold seasonal variations in abundance at the four sites.     

What’s on your boots: an investigation into the role we play in protist dispersal

D. M. Wilkinson (2010, Journal of Biogeography, 37 , 393–397) suggested that anthropogenic dispersal is an understudied and potentially important factor in terrestrial protist biogeography. We investigated human footwear as a potential vector of dictyostelids, a diverse group of amoebae that includes both geographically restricted and cosmopolitan species. Eighteen pairs of boots were examined and dictyostelids were isolated from nearly all samples larger than 5.0 g. In total, six dictyostelid isolates were recovered, corresponding to four species –Dictyostelium minutum, D. sphaerocephalum, D. leptosomopsis and a new species, Polysphondylium sp. 1. Myxogastrid amoebae and acrasid‐like aggregations were also observed. Thus anthropogenic dispersal of naked amoebae appears to occur. The possible role of variations in dictyostelid fruiting body morphologies in dispersal potential is also discussed. These results support Wilkinson’s proposal and suggest that dictyostelids may be a useful group with which to study anthropogenic dispersal of terrestrial protists.     

The microbiology of soils under successive wheat crops in relation to take-all disease

Abstract Thirty-eight wheat fields in southern England were sampled in an attempt to correlate the amount of take-all disease with 35 microbiological and chemical measurements of soil. There was little correlation between field take-all and pot tests to determine soil infectivity. Myxogastrids were important components of the soil population, being up to half of the amoebal population, and most soils contained dictyostelids, reticulate amoebae and myxobacteria. Amoebae, ciliates, bacteria and saprophytic fungi were recorded for all soils. pH was a major determinant of soil populations, being clearly correlated with fungal abundance and with numbers of ciliates, dictyostelids and bacteria. Principal component analysis separated dictyostelids from the other soil amoebae and again showed the importance of pH in determining soil microbial populations. Take-all was negatively correlated with soil fertility and positively related to nematodes and myxobacteria, but this was probably an effect of take-all, and represented saprophytic growth on dead roots rather than being a cause. Reticulate amoebae and dictyostelids were both correlated with low levels of take-all. This study emphasises the large number of interrelated populations of soil microorganisms which could have an effect on the severity of take-all infections.     

Five new species of dictyostelid social amoebae (Amoebozoa) from Thailand

Background

Dictyostelid cellular slime molds (dictyostelids) are common inhabitants of the soil and leaf litter layer of fields and forests, along with animal dung, where they feed mostly on bacteria. However, reports on the species diversity of dictyostelids in South Asia, particularly Thailand, are limited. The research reported in this paper was carried out to increase our knowledge of the species diversity of this group of organisms in northern Thailand.

Results

Forty soil samples were collected at four localities in northern Thailand to assess the species richness of dictyostelids. These samples yielded five dictyostelid isolates that were not morphologically consistent with any described species. Based on molecular signatures, all five of these isolates were assigned to the family Cavenderiaceae, genus Cavenderia. All five share a number of morphological similarities with other known species from this family. The new taxa differ from previously described species primarily in the size and complexity of their fruiting bodies (sorocarps). This paper describes these new species (Cavenderia aureostabilis, C. bhumiboliana, C. protodigitata, C. pseudoaureostipes, and C. subdiscoidea) based on a combination of morphological characteristics and their phylogenetic positions.

Conclusions

At least 15 taxa of dictyostelids were obtained from the four localities in northern Thailand, which indicates the high level of species diversity in this region. Five species were found to be new to science. These belong to the family Cavenderiaceae, genus Cavenderia, and were described based on both morphology and phylogeny.

     

Polysphondylium multicystogenum sp. nov., a new dictyostelid species from Sierra Leone, West Africa

Polysphondylium multicystogenum, a new heterothallic species of dictyostelids, is described based on three isolates collected from soils in Sierra Leone, West Africa. This species is characterized by sorophores with a combination of clavate base and ovoid to oblong tip cell, smaller spores and abundant microcyst production under the usual culture conditions for sorocarp formation at 20 C. This is the first report of Polysphondylium producing such abundant microcysts.     

网柄细胞状黏菌生态学的研究进展

网柄细胞状黏菌(简称网柄菌)是黏菌的第二大类群,对其生态特征的研究有助于深入了解这类生物适宜的生存条件和人类活动的影响。本文回顾了1869年至今的网柄菌生态学研究历史,从地理因素、植被因素、生物因素三个角度,探讨了影响网柄菌物种丰度和多度的生态因素,从而为土壤及凋落物中黏菌的物种多样性保护提供参考。     

Heat-tolerant flowering plants of active geothermal areas in Yellowstone National Park

A broad survey of most of the major geyser basins within Yellowstone National Park (Wyoming, USA) was conducted to identify the flowering plants which tolerate high rhizosphere temperatures (> or = 40 degrees C) in geothermally heated environments. Under such conditions, five species of monocots and four species of dicots were repeatedly found. The predominant flowering plants in hot soils (>40 degrees C at 2-5 cm depth) were grasses, primarily Dichanthelium lanuginosum. Long-term (weeks to months) rhizosphere temperatures of individual D. lanuginosum above 40 degrees C were recorded at several different locations, both in the summer and winter. The potential role of heat shock proteins (HSPs) in the apparent adaptation of these plants to chronically high rhizosphere temperatures was examined. Antibodies to cytoplasmic class I small heat shock proteins (sHSPs) and to HSP101 were used in Western immunoblot analyses of protein extracts from plants collected from geothermally heated soils. Relatively high levels of proteins reacting with anti-sHSP antibodies were consistently detected in root extracts from plants experiencing rhizosphere temperatures above 40 degrees C, though these proteins were usually not highly expressed in leaf extracts from the same plants. Proteins reacting with antibodies to HSP101 were also present both in leaf and root extracts from plants collected from geothermal soils, but their levels of expression were not as closely related to the degree of heat exposure as those of sHSPs.     

Developmental features and associated symbiont bacterial diversity in essential life cycle stages of Heterostelium colligatum

Dictyostelium discoideum is a specialized amoebozoan protist that can feed on, carry and disperse bacteria. However, the symbiont bacterial diversity in other species of dictyostelids and the diversity associated with essential life cycle stages are still unknown until now. Here, another species of dictyostelids, Heterostelium colligatum, a new record for tropical China, was isolated from the soil collected in Xishuangbanna Tropical Botanical Garden, Yunnan Province, China. We describe the complete life cycle of this species and illustrate details of spore-to-spore development. The symbiont bacterial diversity and relative abundance associated with life cycle stages of H. colligatum, including the aggregation, pseudoplasmodium, and sorocarp stages, were investigated by high throughput metagenomic techniques. H. colligatum appears to be capable of carrying different types of bacteria during its life history in addition to those used as a food resource. The dominant groups of those three stages in its life cycle were the Proteobacteria, Actinobacteria and Firmicutes. The relative abundance of the dominant phyla and shared OTUs were different for the aggregation, pseudoplasmodium, and sorocarp stages. A comparison of the symbiont bacterial assemblages associated with D. discoideum and H. colligatum indicated that different dictyostelid species carried different species of symbiont associated bacteria.     

Distribution and ecology of dictyostelids in China

Dictyostelid cellular slime molds are a ubiquitous component of most soils, where they feed upon bacteria and other microbes and thus play an essential role in the soil ecosystem. Herein we review the available literature on dictyostelid cellular slime molds in China, especially their diversity and ecology. The patterns of distribution for these organisms in relation to the different habitats with which they are associated are analyzed and discussed. In addition, the assemblages of dictyostelids reported from China and the United States were compared. The CC value obtained (0.48) indicates that China and the United States are perhaps less similar than might be expected. Our data point out the need for further studies to characterize more completely the assemblages of dictyostelids associated with particular vegetation types or particular regions throughout the world.     

Dictyostelids from Mediterranean forests of the south of Europe

The first results of a study of dictyostelid diversity in soils of Mediterranean vegetation are presented. Surface soil samples were collected during 2003–2004 from different Mediterranean forests in Spain and Portugal and were plated out for cellular slime moulds. Isolated during this study were 14 species of dictyostelids. One species, Dictyostelium firmibasis is reported for the first time from Europe, and nine (Dictyostelium aureo-stipes, Dictyostelium sp. 1, Dictyostelium fasciculatum, Dictyostelium giganteum, Dictyostelium implicatum, Dictyostelium leptosomum, Dictyostelium sphaerocephalum, Polysphondylium candidum, Polysphondylium pallidum) are new records for the Mediterranean region. Members of the three genera Dictyostelium (ten species), Polysphondylium (three species) and Acytostelium (one species) are present in this region of the world. Comments on their diversity and distribution are included.     

大头网柄菌的个体发育

【背景】网柄细胞状黏菌是生物学、细胞学及发生生物学研究中一类重要的模式生物,至今已报道了百余种,但每个种的个体发育过程不是很明晰。【目的】了解网柄细胞状黏菌的个体发育。【方法】对采自云南苍山的土壤样品进行网柄菌的分离、培养和鉴定,并详细记录其个体发育全阶段特征。在传统形态学方法基础上,对样品进行基因组18S测序,并将获得序列在GenBank注册。通过双凹载玻片及水琼脂培养基添加大肠杆菌的培养方法,显微观察样品的发育过程,包括孢子、黏变形体、集群、假原质团、拔顶、孢堆果的发育特征。【结果】分离得到大头网柄菌Dictyostelium macrocephalum;该种温度适应范围较广,是亚热带和热带的广布种;其完成一个生活循环历时3 d,接种20 h后孢子开始萌发释放黏变形体,第50 h形成集群,第56 h假原质团形成,第58 h孢堆原形成,第71 h孢堆果完全成熟。【结论】研究分离的大头网柄菌为云南省新记录种,增加了其在我国亚热带的新分布区;明确了该种的个体发育过程。     

网柄细胞状黏菌生物学特性及其应用研究进展

网柄细胞状黏菌是一类介于植物和动物之间的原生生物。尽管形态微小,但因为同时具有动物细胞和植物细胞的特点,且生命周期短暂易重复,故而对其进行生物学特性及应用的研究具有重要价值。本文从网柄细胞状黏菌的生活史循环、生物学特性、生态多样性、在医学和药物领域的探索及其与其他微生物关系等5个方面探讨网柄细胞状黏菌的生物学特性及应用的研究进展及意义,展望网柄细胞状黏菌未来在医学和生态等方面的研究前景及其潜在的应用价值,旨在为我国网柄细胞状黏菌同其他领域的交叉研究相结合提供视野,探索其在促进人类的科学进步、改善生活环境及攻克疾病方面的作用及意义。     

DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.      

Diverse communities of arbuscular mycorrhizal fungi inhabit sites with very high altitude in Tibet Plateau

Diversity of arbuscular mycorrhizal fungi (AMF) is well studied in many ecosystems, but little is known about AMF in cold-dominated regions with very high altitude. Here, we examined AMF communities associated with two plant species in the Tibet Plateau. Roots and rhizosphere soils of Dracocephalum heterophyllum (pioneer species) and Astragalus polycladus (late-successional species) were sampled at five sites with altitude from 4500 to 4800 m a.s.l. A total of 21 AMF phylotypes were identified from roots and spores following cloning and sequencing of 18S rRNA gene, including eight new phylotypes and one new family-like clade. More AMF phylotypes colonized root samples of D. heterophyllum (5.4±0.49) than of A. polycladus (1.93±0.25). Vegetation coverage was the most important factor influencing AMF community composition in roots. Globally infrequent phylotype Glo-B2 in Glomus group B was the most dominant in roots, followed by globally frequent phylotype Glo-A2 related to Glomus fasciculatum/intraradices group. Our findings suggest that a diverse AMF flora is present in the Tibet Plateau, comprising both potentially habitat-selective and generalist fungi.     

Torulaspora indica a novel yeast species isolated from coal mine soils

Four yeast strains (APSS 805, APSS 806, APSS 815 and AP-18) belonging to a novel Torulaspora species were isolated from coal mine soils of Singareni in Andhra Pradesh state, India. Another strain (PBA-22) was isolated from agricultural field soil from Gujarat state, India. The vegetative cells of all these strains were round, haploid and produced asci by conjugation between independent cells or mother cell and bud, with rough ascospores, suggesting their possible relation to ascomycetous yeast genus Torulaspora. Phylogenetic analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene and Internal Transcribed Spacer (ITS) regions revealed that, among the five strains, three viz. APSS 805, APSS 806 and APSS 815 have identical sequences. The other two strains (AP-18 and PBA-22) differed from the other three strains in less than 1% nucleotide substitutions in the combined D1/D2 domain and ITS sequences, indicating that all of them (five strains) may belong to the same species. These five strains were closely related to Torulaspora globosa, but showed more than 3–7% sequence divergence from T. globosa and all other species in the genus Torulaspora in the combined sequence analysis of D1/D2 domain and ITS region of rRNA gene. In addition, these strains also showed distinct microsatellite finger-printing pattern from related species and differed in several physiological responses suggesting that these strains belong to a novel species of Torulaspora. We propose to name these strains as Torulaspora indica sp. nov., and designate APSS 805^T = MTCC 9772 ^T = CBS 12408 ^T as the type strain of this novel species. The Mycobank number of the novel species is MB 563738.     

Cropping systems for phytoremediation of phosphorus-enriched soils

Eutrophication of freshwater bodies is frequently attributed to elevated phosphorus (P) concentrations in surface runoff from P-enriched agricultural soils. Forage and grain-cropping systems were compared for their effectiveness at remediating P-enriched soils. At each of four locations, one of three forage systems (Forage I = cereal rye silage and corn silage annually; Forage II = alfalfa; Forage III = annual ryegrass and corn silage annually) and the grain system (corn, small grain, and soybean rotation) were maintained for 3 yr on soils with five distinct initial soil P concentrations that were established by using four annual applications (1994-1997) of five different rates (0, 100, 200, 300, and 400 kg total P ha(-1) y(-1)) of poultry manure, dairy manure, or commercial fertilizer. Across all manure P treatments at all locations, the forage systems had greater removal of P than the grain system. Soil P concentration changes (2001-2004) did not reflect differences in crop P removal. Few significant reductions in soil P concentration were observed for either crop system. When reductions did occur, they were for the more highly enriched soil P treatments. No significant reductions in soil P concentration have occurred for the lowest manure P treatments. Considerable variability in crop P concentrations was observed among species at locations and among years produced. However, crop P concentrations did increase uniformly as soil P concentration increased, indicating that luxury consumption of P does occur in agronomic species produced on P-enriched soils.     

Occurrence of Enterococci: Bud, Blossom, and Soil Studies

The occurrence of enterococci (group D streptococci) on buds and flowers of plants and in soils has been studied. They were recovered from 27.5% of the flowers of seven species of plants, and from 6.8% of the buds of the same plants. They were recovered from 34% of the flowers of nonagricultural plants, from 32.2% of the flowers of ten species of agricultural dicotyledonous plants, and from 10.4% of the flowers of five species of grasses and cereals. The enterococci were invariably present or invariably absent from all samples taken from very few species. They occurred in small numbers on enclosed tassels and silks of corn of 22 of 60 samples, and in greater numbers on 90% or more of these after their floral parts had emerged. Interposition of a mechanical barrier reduced the incidence of recovery from flowers. The occurrence in soil, generally at a low level of population, may be correlated with occurrence on the plant growing on the soil or with nearby enterococcal-bearing plants.It is concluded that enterococci may be regarded as temporary residents on plants, capable of limited reproduction, and that they are disseminated among plants by the action of insects and wind, and spread to the ground by these agencies, gravity, and rain.