Zooplankton grazing on bacteria and cyanobacteria in a eutrophic lake

During in situ experiments in a cyanobacteria- and copepod-dominatedeutrophic subtropical lake, all taxa of protozoa and metazoanzooplankton grazed fluorescently labelled bacteria and all metazoanzooplankton taxa grazed large filamentous and colonial cyanobacteria.     

ORIGINS AND AFFINITIES OF THE FILAMENTOUS GREEN ALGAL ORDERS CHAETOPHORALES AND OEDOGONIALES BASED ON 18S rRNA GENE SEQUENCES

The order Chaetophorales includes filamentous green algae whose taxonomic relationships to other chlorophycean orders is uncertain. Chaetophoralean taxa include filamentous species which are both branched and unbranched. Ultrastructural studies of zoospores have revealed similar flagellar apparatuses in a number of genera, including Uronema, Stigeoclonium, and Fritschiella, suggesting a close phylogenetic relationship among these taxa. The order Oedogoniales represents a second group of branched and unbranched filamentous green algae whose relationships to other chlorophycean orders also has been unclear. A possible close relationship between the Chaetophorales and Oedogoniales has been suggested. Using DNA sequences from the small-subunit ribosomal RNA gene (SSU rRNA) of several members of each order, we have examined the monophyly of the Chaetophorales and Oedogoniales, as well as the nature of their relationship to other chlorophycean orders. Our results show that chaetophoralean and oedogonialean taxa form separate monophyletic groups. Results also suggest that the two orders are not closely related to each other.     

The effect of wind exposure and filamentous algae on the distribution of surf zone macroinvertebrates in Lake Esrom,Denmark

Distribution and composition of the epilithic macroinvertebrate fauna was studied on 21 different sites situated in the surf zone of Lake Esrom. A relative degree-of-exposure (windinduced wave activity) was calculated for each station from the specific number of wind days, wind velocity and a measured wind fetch. Macroinvertebrate abundance averaged 20 200 ind. m^–2 stone bottom, and was composed primarily of six taxa (70% of the mean densities). The distribution patterns of the 48 most common taxa were compared to exposure, the amount of filamentous algae and shore slope, by regression, cluster analysis and ordination analysis (PCA and RDA). The abundance of 25 taxa was significantly correlated to the amount of filamentous algae, and a protectional effect of algae growth was suggested for the exposed sites. Seventeen taxa showed significant difference in abundance between sheltered western stations and exposed eastern stations. Stations with a gentle slope were characterised by sand covered stones and a fauna that qualitatively was similar to the fauna at greater depth in the littoral. Redundancy analysis (RDA) showed filamentous algae and slope to be the most important factors controlling the species distribution, whereas the gradient of exposure in Lake Esrom was too short to explain the species tolerance range.     

植物病原丝状真菌G蛋白偶联受体的研究进展

通过对丝状真菌G蛋白偶联受体(GPCR)的结构、分类以及功能方面进行综述,以期明确丝状真菌与其他模式生物GPCR之间的关系。基于已报道的模式生物及丝状真菌等不同生物中的GPCR,通过SMART保守结构域分析,以及利用Clustal X、MEGA等软件对上述GPCR进行遗传关系分析。明确丝状真菌典型GPCR具有七跨膜结构域,新型GPCR则含有PIPK、RGS等保守结构域,明确不同学者对于GPCR的分类情况,以及新型GPCR所具有的特殊功能,明确模式生物GPCR、丝状真菌GPCR分别各自聚类。丝状真菌中GPCR的数量较模式生物少,不同分类单元中真菌之间GPCR的数量也不尽相同,同时,丝状真菌GPCR除具有典型的七跨膜结构域外,还含有一些其他保守的结构域,上述研究为进一步开展其功能研究提供重要的理论基础。     

Stable carbon isotope variability associated with taxonomic composition of lotic benthic algae

We examined the relationship between the δ¹³C and taxonomic composition of benthic algae collected from a riffle (fast current habitat) of a non‐shaded mountain stream, which is a tributary of the Kiso River, Japan. The benthic algal δ¹³C ranged from ?20.6 to ?14.2‰ and tended to be ¹³C‐depleted with increasing relative abundance of upright filamentous cyanobacteria and ¹³C‐enriched with increasing relative abundance of prostrate filamentous cyanobacteria. Using isotopic mass balance equations, the relative abundance of the dominant taxa, upright and prostrate filamentous cyanobacteria, small diatoms and others, explained 74% of δ¹³C variability. This study shows a case where the difference in taxonomic composition is a possible source of the isotopic variability of benthic algae, which is a mixture of taxa with distinct isotopic signatures.     

Experimental warming alters potential function of the fungal community in boreal forest

Fungal community composition often shifts in response to warmer temperatures, which might influence decomposition of recalcitrant carbon (C). We hypothesized that evolutionary trade‐offs would enable recalcitrant C‐using taxa to respond more positively to warming than would labile C‐using taxa. Accordingly, we performed a warming experiment in an Alaskan boreal forest and examined changes in the prevalence of fungal taxa. In a complementary field trial, we characterized the ability of fungal taxa to use labile C (glucose), intermediate C (hemicellulose or cellulose), or recalcitrant C (lignin). We also assigned taxa to functional groups (e.g., free‐living filamentous fungi, ectomycorrhizal fungi, and yeasts) based on taxonomic identity. We found that response to warming varied most among taxa at the order level, compared to other taxonomic ranks. Among orders, ability to use lignin was significantly related to increases in prevalence in response to warming. However, the relationship was weak, given that lignin use explained only 9% of the variability in warming responses. Functional groups also differed in warming responses. Specifically, free‐living filamentous fungi and ectomycorrhizal fungi responded positively to warming, on average, but yeasts responded negatively. Overall, warming‐induced shifts in fungal communities might be accompanied by an increased ability to break down recalcitrant C. This change in potential function may reduce soil C storage under global warming.     

Further revisions of the Sabellidae subfamilies and cladistic relationships among the Fabriciinae (Annelida: Polychaeta)

Cladistic relationships of the sabellid subfamilies Fabriciinae and Sabellinae are examined in light of recent revisions of fabriciin taxa. The potential placement of Caobangia in the Sabellinae is suggested from an initial analysis of selected fabriciin species and genera. Subsequent cladistic analyses at the family level produced over 1800 cladograms, among which Caobangia is the most plesiomorphic taxon of either the Fabriciinae or Sabellinae. Successive approximations weighting reduced this ambiguity, consistently placing Caobangia in the Sabellinae. Subfamilies are emended on the basis of these results. Cladistic relationships of fabriciin taxa, exclusive of Caobangia , display topological instability among some genera and species. Genera are, however, monophyletic in all topologies. Incorporating ontogenetic data for branching ventral filamentous appendages in Augeneriella reduces ambiguity among genera and suggests alternative transformation series for ventral filamentous appendages.     

Chlorophytes of biological soil crusts in Gurbantunggut Desert, Xinjiang Autonomous Region, China

In this paper, chlorophytes collected from 253 biological soil crust samples in Gurbantunggut Desert in Xinjiang Autonomous Region, China were studied by field investigation and microscopical observation in lab. The flora composition, ecological distribution of chlorophytes in the desert and dynamic changes of species composition of chlorophytes in different developing stages of biological soil crusts are preliminarily analyzed. Results showed that there were 26 species belonging to 14 genera and 10 families, in which unicellular chlorophytes were dominant. There existed some differences in distribution of varied sand dune positions. The taxa of chlorophytes in leeward of sand dunes are most abundant, but the taxa in windward, interdune and the top of sand dunes reduced gradually. Chlorophytes were mainly distributed within the crust and the taxa of chlorophytes decrease obviously under the crust. In the devel-oping stages of the biological soil crust, species diversity of chlorophytes changed a little, but species composition pre-sented some differences. Chlorococcum humicola, Chlorella vulgaris, Chlamydomonas ovalis and Chlamydomonas sp. nearly existed in all developing stages of biological crusts. In several former stages of the biological soil crust there were spherical chlorophytes and filamentous ones. When moss crust formed, filamentous chlorophytes disappeared, such as Microspora and Ulothrix.     

Grazing on filamentous algae by herbivorous zooplankton

SUMMARY. 1. Feeding experiments were conducted to examine filtering rates and selectivity of a variety of zooplankton taxa (including cladocerans, copepods and a rotifer) for filamentous diatoms, green and blue-green algae.
2. Most herbivores were capable of consuming some filamentous algae at rates similar to or higher than those on unicellular algae. Only feeding of Diaphanosoma brachyurum Liéven and Moina micrura Kurz seemed to be primarily limited by the filamentous morphology.
3. Filtering rates and selectivities of most herbivores were much higher for the diatom Melosira granulata angustissima Müller than for similarly sized blue-green algal filaments, indicating that chemical factors strongly influence consumption of filamentous algae.
4. The toxic blue-green algal filament Anabaena flos-aquae De Brébisson NRC 44–1 had a much strong inhibitory effect on zooplankton feeding than other filaments. The only herbivores that were not inhibited by this strain have been shown to be resistant to blue-green algal toxins, or strongly avoided consuming the blue-green alga. These results indicate that the inhibitory effect of filamentous algae is due more to toxic or noxious chemicals than to the filamentous morphology.
5. Selectivities of zooplankton for filamentous algae were largely independent of herbivore body size. The small-bodied cladoceran Bosmina longirostris Müller had the highest selectivities for filamentous algae.     

Genetic transformation of filamentous fungi

Many filamentous fungi of all taxa can now be subject to DNA-mediated transformation. Many dominant selectable markers are available and the range available is increasing as new genes are cloned. Transformation is especially valuable in cloning genes defined by mutations with selectable phenotypes and is allowing investigation of many problems in fungi with good genetic systems. Increasingly sophisticated techniques for inactivating genes, targetingin vitro generated mutations to specific loci, and altering gene expression and its regulation are being developed. These approaches are being used to investigate the wealth of basic and applied biological problems available in filamentous fungi.     

High diversity and complex evolution of fungal cytochrome P450 reductase: cytochrome P450 systems

Cytochrome P450 reductase (CPR) is the redox partner of P450 monooxygenases, involved in primary and secondary metabolism of eukaryotes. Two novel CPR genes, sharing 34% amino acid identity, were found in the filamentous ascomycete Cochliobolus lunatus. Fungal genomes were searched for putative CPR enzymes. Phylogenetic analysis suggests that multiple independent CPR duplication events occurred in fungi, whereas P450-CPR fusion occurred before the diversification of Dikarya and Zygomycota. Additionally, losses of methionine synthase reductase were found in certain fungal taxa; a truncated form of this enzyme was conserved in Pezizomycotina. In fungi, high numbers of cytochrome P450 enzymes, multiple CPRs, and P450-CPR fusion proteins were associated with filamentous growth. Evolution of multiple CPR-like oxidoreductases in filamentous fungi might have been driven by the complexity of biochemical functions necessitated by their growth form, as opposed to yeast.     

High diversity and complex evolution of fungal cytochrome P450 reductase: cytochrome P450 systems.

Cytochrome P450 reductase (CPR) is the redox partner of P450 monooxygenases, involved in primary and secondary metabolism of eukaryotes. Two novel CPR genes, sharing 34% amino acid identity, were found in the filamentous ascomycete Cochliobolus lunatus. Fungal genomes were searched for putative CPR enzymes. Phylogenetic analysis suggests that multiple independent CPR duplication events occurred in fungi, whereas P450-CPR fusion occurred before the diversification of Dikarya and Zygomycota. Additionally, losses of methionine synthase reductase were found in certain fungal taxa; a truncated form of this enzyme was conserved in Pezizomycotina. In fungi, high numbers of cytochrome P450 enzymes, multiple CPRs, and P450-CPR fusion proteins were associated with filamentous growth. Evolution of multiple CPR-like oxidoreductases in filamentous fungi might have been driven by the complexity of biochemical functions necessitated by their growth form, as opposed to yeast.     

Aerobic microorganisms associated with alfalfa leafcutter bees (megachile rotundata)

Characterization of microorganisms associated with alfalfa leaf-cutter bee (Megachile rotundata) nectar, pollen, provisions, larval guts, and frass (excreta) in Alberta demonstrated a varied aerobic microflora. Yeasts were isolated frequently from nectar, pollen, and provisions but rarely from guts or frass. The most prevalent yeast taxa were: Candida bombicola, Cryptococcus albidus, Metschnikowia reukaufii, and Rhodotorula glutinis. Although few filamentous fungi were found in nectar, they were frequently isolated from pollen and provisions; the predominant taxa were Alternaria alternata, Cladosporium cladosporioides, C. herbarum, Epicoccum nigrum, and Penicillium chrysogenum. Bacteria, including species of Bacillus, Corynebacterium, Micrococcus, and the actinomycete Streptomyces, also were prevalent in provisions and/or on pollen. In general, the diversity of microorganisms isolated from alimentary canals and frass was lower than from nectar, pollen, and provisions. Bacillus firmus, B. licheniformis, B. megaterium, B. pumilus, and Streptomyces spp. were the most frequently isolated bacteria, whereas Trichosporonoides megachiliensis was the most common filamentous fungus isolated from larval guts and/or frass. These taxa may be part of the resident microflora of the alimentary canal. Populations of bacteria and filamentous fungi, but not yeasts, were larger from Ascosphaera aggregata-infected larvae than from healthy larvae. However, with the exception of Aspergillus niger and T. megachiliensis in frass from healthy larvae, no taxon of filamentous fungi was conspicuously present or absent in infected larvae, healthy larvae, or their frass. Offprint reauests to: M.S. Goettel.     

Novel filamentous spore-forming iron bacteria causes bulking in activated sludge

Several Gram-positive iron bacteria were isolated from bulking sludge. They were filamentous and had false branching. They had sheaths with iron deposits and formed spores on modified sucrose casitone yeast extract agar. They did not grow on influsion agar for longer than 1 month but could withstand 80°C for 1 h on the same medium. Adding them to sewage before aeration increased the biochemical oxygen demand of waste water and caused poor settling properties of activated sludges. They were the predominant filamentous micro-organisms in bulking activated sludges. At present, these strains cannot be assigned to recognized taxa of Bacillus spp. or sheathed iron bacteria.     

Algal-periphyton population and community changes from zinc stress in stream mesocosms

Three treatments of zinc (0.05, 0.5, 1.0 mg Zn l⁻¹) and a control could be identified by different algal communities in outdoor, flow-through, stream mesocosms. Established communities were continuously exposed to Zn, and samples were collected on days 0, 2, 5, 10, 20 and 30 after treatment began. Experiments were conducted in spring, summer, and fall 1984. Control stream mesocosms could be identified by diatoms in all seasons. The 0.05 mg Zn l⁻¹ treatment could be identified by certain diatom taxa being more abundant than in the control in all seasons and by a filamentous green alga in summer and fall. The 0.5 mg Zn l⁻¹ treatment could be identified by a filamentous green alga in fall. The 1.0 mg Zn l⁻¹ treatment was dominated by unicellular green algae in all seasons and by a filamentous blue-green alga in summer. A similarity index (SIMI) indicated that Zn-stressed samples generally became less similar to control samples as Zn concentration increased from 0.05 to 1.0 mg Zn l⁻¹. Total biovolume-density of all taxa responded slower than individual taxa in spring and failed to distinguish between Zn treatments in summer and fall. Zinc bound to periphyton was much better than total Zn in water for identifying Zn treatments. Zinc treatments as low as 0.05 mg Zn l⁻¹ changed algal species composition despite 0.047 mg Zn l⁻¹ being the Criterion of the US Environmental Protection Agency for the 24-h average of total recoverable Zn.     

Novel Actinomycete Isolated from Bulking Industrial Sludge

A novel actinomycete was the predominant filamentous microorganism in bulking activated sludge in a bench-scale reactor treating coke plant wastewater. The bacterium was isolated and identified as an actinomycete that is biochemically and morphologically similar to Amycolatopsis orientalis; however, a lack of DNA homology excludes true relatedness. At present, the isolate (NRRL B 16216) cannot be assigned to the recognized taxa of actinomycetes.     

Analysis of environmental drivers influencing interspecific variations and associations among bloom-forming cyanobacteria in large,shallow eutrophic lakes

Non-diazotrophic Microcystis and filamentous N₂-fixing Aphanizomenon and Dolichospermum (formerly Anabaena) co-occur or successively dominate freshwaters globally. Previous studies indicate that dual nitrogen (N) and phosphorus (P) reduction is needed to control cyanobacterial blooms; however, N limitation may cause replacement of non-N₂-fixing by N₂-fixing taxa. To evaluate potentially counterproductive scenarios, the effects of temperature, nutrients, and zooplankton on the spatio-temporal variations of cyanobacteria were investigated in three large, shallow eutrophic lakes in China. The results illustrate that the community composition of cyanobacteria is primarily driven by physical factors and the zooplankton community, and their interactions. Niche differentiation between Microcystis and two N₂-fixing taxa in Lake Taihu and Lake Chaohu was observed, whereas small temperature fluctuations in Lake Dianchi supported co-dominance. Through structural equation modelling, predictor variables were aggregated into ‘composites’ representing their combined effects on species-specific biomass. The model results showed that Microcystis biomass was affected by water temperature and P concentrations across the studied lakes. The biomass of two filamentous taxa, by contrast, exhibited lake-specific responses. Understanding of driving forces of the succession and competition among bloom-forming cyanobacteria will help to guide lake restoration in the context of climate warming and N:P stoichiometry imbalances.     

USING rbcL SEQUENCES TO TEST HYPOTHESES OF CHLOROPLAST AND THALLUS EVOLUTION IN CONJUGATING GREEN ALGAE (ZYGNEMATALES, CHAROPHYCEAE)

Sequences for the Rubisco large subunit (rbcL) gene were used to test hypotheses about the evolution of chloroplast shape and thallus type in genera of two families of conjugating green algae (Zygnematales): the Mesotaeniaceae (saccoderm desmids, mostly unicellular) and the Zygnemataceae (strictly filamentous). Unicellular (u) and filamentous (f) genera exhibit a series of three similar chloroplast shapes: ribbonlike (e.g. Spirotaenia [u], Spirogyra [f], and Sirogonium [f], laminate (e.g. Mesotaenium [u] and Mougeotia [f]), and twin-stellate (e.g. Cylindrocystis [u] and Zygnema [f]. Two conflicting phylogenetic hypotheses have been proposed: 1) families are polyphyletic constructs drawn from three lineages, each with unicellular and filamentous taxa characterized by a specific chloroplast shape; or 2) unicells form one monophyletic lineage (Mesotaeniaceae) and filaments form another (Zygnemataceae), with some chloroplast shapes independently derived. The rbcL data strongly refute hypothesis 2 (monophyly of the two traditional families) and support hypothesis 1 in part. Parsimony, maximum likelihood, and neighbor-joining analyses of the rbcL data strongly support monophyly of a clade containing taxa with ribbonlike chloroplasts and, to a lesser extent, monophyly of a second clade of the four genera with the other two chloroplast shapes. Two saccoderm genera (Roya, curved laminate chloroplasts; Netrium, "cucumber"-shaped chloroplasts) are not members of either of these clades, but they are included in a monophyletic Zygnematales .     

Culturable Fungi of Stored ‘Golden Delicious’ Apple Fruits: A One-Season Comparison Study of Organic and Integrated Production Systems in Switzerland

The effects of organic and integrated production systems on the culturable fungal microflora of stored apple fruits from five matched pairs of certified organic and integrated ‘Golden Delicious’ farms were studied at five representative production sites in Switzerland. Isolated fungi were identified morphologically. Colonization frequency (percentage of apples colonized), abundance (colony numbers), and diversity (taxon richness) were assessed for each orchard. The standard quality of the stored fruits was comparable for both organic and integrated apples and complied with national food hygiene standards. Yeasts (six taxa) and the yeast-like fungus Aureobasidium pullulans were the dominant epiphytes, filamentous fungi (21 taxa) the dominant endophytes. The most common fungi occurred at all sites and belonged to the “white” and “pink” yeasts, yeast-like A. pullulans, filamentous fungi Cladosporium spp., Alternaria spp., and sterile filamentous fungi. Canonical correspondence analysis of the total fungal community revealed a clear differentiation among production systems and sites. Compared to integrated apples, organic apples had significantly higher frequencies of filamentous fungi, abundance of total fungi, and taxon diversity. The effects of the production system on the fungal microflora are most likely due to the different plant protection strategies. The incidence of potential mycotoxin producers such as Penicillium and Alternaria species was not different between production systems. We suggest that higher fungal diversity may generally be associated with organic production and may increase the level of beneficial and antagonistically acting species known for their potential to suppress apple pathogens, which may be an advantage to organic apples, e.g., in respect to natural disease control.