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Rhodopsin transmembrane proton pumps (fuelled by visible light which is absorbed by retinal (carotenoid) chromophores) exist in all three domains of living species and in all groups of true fungi studied. Light driven proton and sodium pumps are likely to be essential for some marine fungi, especially hypersaline tolerant and endolithic species. Rhodopsin macromolecular machines, using visible light, drive metabolic reactions in addition to those provided by aerobic respiration, providing extra energy needed for the maintenance and growth of fungi, especially in euphotic environments where oxygen concentration is limited. In addition, dissimilatory nitrate and metal oxide reduction can provide sources of energy for fungi in the absence of oxygen, for example, in fungal species growing in marine sediments. Finally, the oxidation of elemental sulphur, iron and manganese can be a source of energy. Some fungi are, therefore, lithotrophs and photoheterotrophs. The ecological implications of these latter processes are discussed. • Rhodopsin transmembrane proton pumps exist in all three domains of living species. • Rhodopsin complexes can drive some metabolic reactions using carotenoid chromophores. • Carotenoid chromophores absorb and sense duration and intensity of visible light. • Dissimilatory nitrate and metal reductions can provide sources of energy in fungi. • Oxidation of elemental sulphur, iron and manganese are sources of energy as well. [ABSTRACT FROM AUTHOR]

Many species of zoosporic heterotrophic parasites, saprotrophs and mutualists in the Phyla Perkinsozoa (dinoflagellates), Oomycota, Hyphochytriomycota, Labyrinthulomycota and Phyomyxea share morphological characteristics with zoosporic true fungi especially with some of the Chytridiomycota and with fungus-like organisms in the Phyla Mesomycetozoea, Chytridiomycota and Aphelidae. These characteristics include chemotactic motile zoospores, zoosporangia which produce zoospores, thick walled resistant cysts, rhizoid-like structures, hyphal-like structures and cell walls surrounding the cells in several phases of their life cycle. These assemblages also inhabit both marine and freshwater ecosystems in which aquatic fungi and fungus-like organisms are found, have similar life cycles, grow on similar substrates, use similar infection strategies and infect some of the same host plants and animals. Many of these species were once included in the aquatic phycomycetes, an ecological assemblage of microorganisms but not a valid taxonomic group. Some of the shared characteristics are discussed in this review. [ABSTRACT FROM AUTHOR]

The “aquatic phycomycetes” constitute an ecologically and economically important assemblage of eukaryotic microorganisms, because they share many morphological traits and important ecological functions and they interact with each other in aquatic ecosystems. The last two decades of research have provided both molecular and structural evidence that the “aquatic phycomycetes” are a diverse, polyphyletic grouping and therefore not a valid taxonomic entity. Very little research has been conducted for many years with the “aquatic phycomycetes”, possibly because in general these microorganisms are often hard to isolate and maintain in most laboratory facilities, little background data has been available to identify the species, the studies were time consuming, the state of the art technology in many cases did not permit studies on these groups and they were thought to be economically and ecologically unimportant. However, this perception has changed recently. For example, some of these species (1) are now known to play important roles in biomass conversion and sequestration of CO 2 , (2) are parasites of many fungal, plant and animal species, (3) may harbor genes of important enzymes for industrial applications and (4) can serve as indicator species for eco-tox monitoring. This review discusses the assemblages of microorganisms which Sparrow placed into the aquatic phycomycetes, their history in brief and their current phylogenetic placement. [ABSTRACT FROM AUTHOR]

Degrees of colonization of palynomorphs from six mangrove plants by chytrids and thraustochytrids in four mangrove plant communities at each stage of the pre–depositional taphonomic process were investigated using a pollen–baiting method. Chytrids and thraustochytrids were the dominant group colonizing palynomorphs in mangroves, gaining access to the cytoplasm through the wall or aperture. There were no significant differences in the degree of colonization between the different plant communities. Pollen with a larger size and/or extensive apertural region appeared to be the most colonized, while the absence of apertures and the presence of a thick wall seemed to reduce the chance of colonization by these microorganisms. Taphonomic experiments showed that the longer palynomorphs take to settle into the mangrove sediments, the lower the possibility of survival from the destructive colonization by chytrids and thraustochytrids and consequently the less carbon that will be sequestered. [ABSTRACT FROM AUTHOR]

Living organisms in aquatic ecosystems are almost constantly confronted by pathogens. Nevertheless, very little is known about diseases of marine diatoms, the main primary producers of the oceans. Only a few examples of marine diatoms infected by zoosporic parasites are published, yet these studies suggest that diseases may have significant impacts on the ecology of individual diatom hosts and the composition of communities at both the producer and consumer trophic levels of food webs. Here we summarize available ecological and morphological data on chytrids, aphelids, stramenopiles (including oomycetes, labyrinthuloids, and hyphochytrids), parasitic dinoflagellates, cercozoans and phytomyxids, all of which are known zoosporic parasites of marine diatoms. Difficulties in identification of host and pathogen species and possible effects of environmental parameters on the prevalence of zoosporic parasites are discussed. Based on published data, we conclude that zoosporic parasites are much more abundant in marine ecosystems than the available literature reports, and that, at present, both the diversity and the prevalence of such pathogens are underestimated. [ABSTRACT FROM AUTHOR]

Parasitism is a widespread interaction that plays significant roles in ecosystem balance and evolution. Historically the biology of zoosporic parasites is often a neglected field when studying aquatic ecological dynamics, especially in marine ecosystems. In the marine environment, dinoflagellates represent a significantly large component of primary production, and may be infected by a variety of fungal and fungus-like parasites including chytrids, syndiniales, and perkinsids as well as other microorganisms. The relationship between these organisms and their dinoflagellate hosts constitutes a highly significant pathosystem given the increasing importance of aquaculture. Because of their small size and lack of morphological characteristics these organisms are difficult to identify. This review compares the taxonomy, life cycle, host range, infection strategies, and ecological roles of species of Parvilucifera , Amoebophrya and Dinomyces which are parasites of dinoflagellates. Most of these species have only been described recently. Implications for environmental management are discussed. [ABSTRACT FROM AUTHOR]

Ophidiomyces ophiodiicola , the causative agent of snake fungal disease, is a serious emerging fungal pathogen of North American-endemic and captive snakes. We provide a detailed literature review, introduce new ecological and biological information and consider aspects of O. ophiodiicola that need further investigation. The current biological evidence suggests that this fungus can persist as an environmental saprobe in soil, as well as colonizing living hosts. Not unlike other emerging fungal pathogens, many fundamental questions such as the origin of O. ophiodiicola , mode of transmission, environmental influences, and effective treatment options still need to be investigated. [ABSTRACT FROM AUTHOR]

Zoosporic true fungi belonging to the phylum Chytridiomycota, commonly referred to as chytrids, are ubiquitous in aquatic environments, however their role in phytoplankton population and eco-physiological dynamics is not fully understood. With the rising occurrence of harmful algal blooms (HABs) of phytoplankton worldwide, there is a growing need to investigate the factors affecting toxicity in algae, with a view to determining the significance of these factors in light of the current trends in global climate change. In this review we present current knowledge regarding the parasitism of phytoplankton by chytrids, including incidence of chytrid epidemics, methodologies used in their isolation and classification, their life cycles and infection strategies, and their potential role in toxin production in algae. We outline key areas in phytoplankton host–parasite dynamics that are poorly understood, discuss the potential roles of chytrids in these areas, and highlight future research directions for the furthering of our knowledge regarding algal ecophysiology. The synthesis of current knowledge in these fields will help researchers develop new hypotheses to further our understanding of primary production in aquatic ecology, and thus enhance our understanding of aquatic ecology, for more effective management of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

There is substantial evidence for the dominant role of Batrachochytrium dendrobatidis in amphibian population dynamics. However, a wide range of other pathogens could also be important in precipitating amphibian population declines, particularly in the face of climate change or other stressors. Here we discuss some examples of zoosporic parasites in the Chytridiomycota, Mesomycetozoa, Perkinsozoa and Oomycota, all of which infect amphibians in freshwater habitats. The pathosystem model provides an excellent basis for understanding host–parasite interactions. Chemotactic zoopores and several families of proteases facilitate infection. Introduction of non-native host may accelerate the dispersal of these parasites. Unlike B. dendrobatidis some of the other zoosporic parasites grow well at or slightly above 25 °C, and their growth rates are likely to increase with global warming. The interactions of parasites with each other and the combined effect of simultaneous infection with multiple species in amphibian populations remain to be carefully studied. [ABSTRACT FROM AUTHOR]

Abstract: Members of the families Chironomidae (chironomids or non-biting midges), Ceratopogonidae (ceratopogonids or biting midges) and Simuliidae (simulids or blackflies) are ubiquitous dipterans of the infraorder Culicomorpha. They are extremely diversified in ecological strategies. Their larvae play major roles in aquatic food webs as detritivores or predators, whereas their adults can be general predators (Chironomidae), hemolymphagous or hematophagous predators (Ceratopogonidae and Simuliidae) or pollinators. Both larval and adult stages are commonly infected by bacteria, viruses, protists, nematodes, true fungi and oomycetes. These phylogenetically diverse assemblages of microorganisms can simultaneously infect multiple species of chironomids, ceratopogonids and simulids, and each host may become trophically interrelated with other hosts by sharing their parasites. Here, we review the information on fungal and oomycete parasites of these dipteran groups with special reference to the natural regulation of host populations, the impact of parasitism in food webs, and the potential of these parasites as biocontrol agents. [Copyright &y& Elsevier]

Abstract: Fungal and fungal-like parasites and the diseases which they cause have been increasingly associated with amphibians and fish population declines at a global scale. This review summarises our current knowledge of the Mesomycetozoea, a poorly-studied group of fungal-like parasites that includes emerging virulent parasites capable of causing high mortality rates in fish and amphibian populations. This review considers the potential impact of emerging parasites in this class on global aquatic biodiversity. Several aspects of the biology of mesomycetozoean parasites are associated with the potential to drive hosts to extinction, including their high virulence under certain conditions, low host specificity, and a free-living infectious stage. In addition, mesomycetozoeans are currently being introduced into novel environments and hosts via the global freshwater wildlife trade. These parasites have been linked to dramatic population declines in at least one native fish throughout Europe, and there are indications that they are already impacting amphibian populations in America and Europe. The impact of mesomycetozoeans on freshwater biodiversity is likely to increase in response to stressors such as global climate change and habitat modification. Surveillance for mesomycetozoean parasites in the field and in specimens transported in the aquatic wildlife trade needs to be increased, and a tighter control of the aquatic wildlife trade is urgently needed. [Copyright &y& Elsevier]

Abstract: Overwhelming evidence suggests that seagrass ecosystems are declining around the world. Pathogens from the genus Labyrinthula have repeatedly been found to cause disease in a variety of seagrass species. For example, the ‘wasting disease’ of Zostera marina has been attributed to Labyrinthula infection. Although poorly characterized taxonomically, species of Labyrinthula are very common in marine ecosystems, virulence of genotypes/phylotypes is known to be variable, and highly virulent species are able to cause ecologically significant diseases of protists, plants and animals. Here, the pathosystem model is applied to host–parasite relationships in seagrass ecosystems. Known physical and biological stressors of seagrass are reviewed. Finally, we make the case that it is time to expand research on this poorly studied microorganism in order to quantify the role of disease in seagrass populations world-wide. [Copyright &y& Elsevier]

Abstract: Pathosystems describe the relationships between parasites, hosts and the environment. Generally these systems remain in a dynamic equilibrium over time. In this review we examine some of the evidence for the potential impacts of change in dynamic equilibrium in blue carbon ecosystems and the relationships to the amount of stored carbon. Blue carbon ecosystems are marine and estuarine ecosystems along the coasts. Virulent pathogens can be introduced into ecosystems along with non-native hosts. Alteration of environmental conditions, such as temperature, pH and salinity, may cause parasites to dominate the pathosystems resulting in significant decreases in productivity and population sizes of producer hosts and in changes in the overall species composition and function in these ecosystems. Such changes in blue carbon ecosystems may result in accelerated release of carbon dioxide back into the ocean and atmosphere, which could then drive further changes in the global climate. The resiliency of these ecosystems is not known. However, recent evidence suggests that significant proportions of blue carbon ecosystems have already disappeared. [Copyright &y& Elsevier]

Abstract: The Mesomycetozoea (Ichthyosporea) includes a group of fungus-like microorganisms which diverged near the animal fungus divide and is basal to the animal lineage in the Opisthokont supergroup. The composition of species within this group has changed considerably since it was reviewed by Mendoza et al. in 2002. There have been many additions to the group as a result of phylogenetic sequencing, and new species have been discovered following examination of digestive tracts of arthropods and other groups of invertebrates. Furthermore, ecological surveys and environmental sampling have revealed a high diversity of Mesomycetozoean phylotypes in marine, freshwater and terrestrial environments. Initially considered a group comprising mainly fish parasites, the Mesomycetozoea are now known to live in association with a wide range of host organisms including invertebrates, fish, amphibians, birds and mammals. Here we review the Mesomycetozoea and examine the broad spectrum of its ecology in the light of recent research based on sequence data, cultivation and in vivo studies. [Copyright &y& Elsevier]

Abstract: Parasites in the Phylum Cryptomycota and their hosts in the Phyla Chytridiomycota, Blastocladiomycota and Oomycota have commonly been observed in aquatic and soil ecosystems. Although rDNA sequence data from environmental samples suggest a wide genetic diversity for the Cryptomycota, Rozella is the only genus described in this group. The species of Rozella which have been studied in the laboratory are biotrophs and have stages with simple morphological characteristics in their life cycles. The life cycles consist of uniflagellate zoospores, thalli which are unwalled, endobiotic protoplasts, and sometimes walled resting spores. These parasites are secondary consumers in producer and detritus based food chains. Species of Rozella efficiently transfer carbon and energy from their hosts (primary consumers) to grazing zooplankton and other tertiary consumers. It is likely that they fine-tune the dynamics of food chains and increase the complexity of food webs. However, there are no quantitative data available at present to support this hypothesis. [Copyright &y& Elsevier]

Abstract: Zoosporic true fungi have frequently been identified in samples from soil and freshwater ecosystems using baiting and molecular techniques. In fact some species can be components of the dominant groups of microorganisms in particular soil habitats. Yet these microorganisms have not yet been directly observed growing in soil ecosystems. Significant physical characteristics and features of the three-dimensional structures of soils which impact microorganisms at the microscale level are discussed. A thorough knowledge of soil structures is important for studying the distribution of assemblages of these fungi and understanding their ecological roles along spatial and temporal gradients. A number of specific adaptations and resource seeking strategies possibly give these fungi advantages over other groups of microorganisms in soil ecosystems. These include chemotactic zoospores, mechanisms for adhesion to substrates, rhizoids which can penetrate substrates in small spaces, structures which are resistant to environmental extremes, rapid growth rates and simple nutritional requirements. These adaptations are discussed in the context of the characteristics of soils ecosystems. Recent advances in instrumentation have led to the development of new and more precise methods for studying microorganisms in three-dimensional space. New molecular techniques have made identification of microbes possible in environmental samples. [Copyright &y& Elsevier]

Abstract: Seventeen fungi in the Chytridiomycota were tested for their ability to use nitrate as a sole source of nitrogen in solid medium, and various organic and inorganic sources of nitrogen in liquid media. Since fourteen of the seventeen isolates grew well on solid chytrid synthetic medium (CSM) with nitrate as the sole source of nitrogen, this medium appears to be excellent for maintaining many of these fungi in culture. Growth was observed in liquid media containing nitrate, ammonium, urea, aspartate, alanine, phenylalanine, histidine and arginine as nitrogen sources. The results did not show clear patterns of nitrogen requirements within the orders tested. However, it does appear that the nitrogen requirements among zoosporic fungi are variable. Single amino acids were poor sources of both carbon and nitrogen in all fungi tested. Furthermore, since glucose and thiamine are the only organic compounds in CSM with nitrate, these results suggest that many of these fungi are capable of growth in the soil under field conditions with very little organic matter. [Copyright &y& Elsevier]

Abstract: Zoosporic fungi (often called chytrids) have been observed frequently on substrata in habitats with extremely low pH but never with extremely high pH. In the present study, growth, zoospore release and survival of some zoosporic fungi (Phyla Blastocladiomycota and Chytridiomycota) isolated from soil in Australia were examined in the laboratory to assess tolerance of extremes in pH. All 21 isolates grew rapidly in both solid and liquid PYG growth media (peptone, yeast extract, glucose) with pH values near neutrality. Most of the sixteen isolates tested could be maintained in culture on solid growth media at pH 4.7 and pH 8.9. One isolate grew down to pH 2.9, four isolates down to pH 3.3 and four isolates up to pH 11.2. In liquid PYG growth media all of the eight isolates tested grew (increased biomass) at pH 5.5 and pH 7.6, most isolates grew rapidly down to pH 4.5, some grew up to pH 11.2 but none of the isolates grew rapidly, if at all, at pH 2.9. The patterns of release of zoospores broadly reflect the patterns of growth at different pH values. Twenty one isolates survived for 7d at 20°C in liquid PYG growth media adjusted to pH 4.7, nine isolates survived down to pH 2.9, twelve up to pH 9.3, eight up to pH 11.2, and three even survived at both pH 2.9 and pH 11.2. The ecological significance of these data remains unclear. Patterns of survival, patterns of growth on solid and in liquid media and relative rates of zoospore release suggest ecotypes which prefer acidic, neutral or alkaline habitats, but these physiological properties were not highly correlated with either the pH of the soils from which these fungi were isolated nor with the taxonomic group in which they are placed. In general, many zoosporic fungi appear to be well adapted to a wider range of pH values than those found in the environments from which these fungi were isolated, and they quickly recover after brief exposure to extremes of pH. [Copyright &y& Elsevier]

Abstract: Some species of zoosporic fungi in the Phylum Blastocladiomycota are obligate parasites of invertebrate animals. Various stages in the life history of the host can be infected, including eggs, larvae and adults. Some parasites, such as some species of Coelomomyces, alternate between two hosts; while others, such as some species of Catenaria, require only one host for reproduction. Infection generally begins after zoospores attach to the outer surface of the host body or to the gut wall. Host specificity and parasite virulence vary broadly among species. Some parasites such as Coelomomyces and Catenaria can naturally regulate dipteran insect or nematode populations. New roles for Blastocladian parasites in food web dynamics have recently been discovered. For example, the parasite Polycaryum can reduce the quantity and quality of Daphnia hosts as a food resource for planktivorous fish. We propose that zoosporic fungal parasites contribute significantly to the biodiversity and the complexity of the food webs in freshwater and soil ecosystems. Further research is needed to highlight the importance of zoosporic fungal parasites in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Recent research suggests that fungal zoospores have important roles in ecosystems. Ultrastructural characteristics of zoospores and sequences of ribosomal RNA genes are increasingly being used in taxonomic and phylogenetic studies with zoosporic fungi. However, our current knowledge of the physiology and ecology of zoospores lags far behind our knowledge of phylogenetic relationships. Some aspects of the ecology of fungal zoospores are discussed in this review. Fungal zoospores have two mechanisms for active short range dispersal: flagellar and amoeboid movement. Flagellar movement is more common in open water and amoeboid movement more common on surfaces. All phases of the life cycle can be passively transported by currents in water for long range dispersal. As far as is known the zoospore never has a cell wall but can have a cell coat. This may cause zoospores to be more susceptible to damage by osmotic and mechanical forces than other phases in the life cycle. The environmental cues for release of zoospores are not understood. Zoospores can often respond to both light and chemical gradients. The behavior of zoospores may influence the structure of the colony formation. Little is known about the modes of nutrition of zoospores. Some zoospores may be osmotrophic but there is no evidence for holozoic nutrition. [Copyright &y& Elsevier]

Abstract: Very little is known about the capacity of soil chytrids to withstand freezing in the field. Tolerance to freezing was tested in 21 chytrids isolated from cropping and undisturbed soils in temperate Australia. Samples of thalli grown on peptone–yeast–glucose (PYG) agar were incubated for seven days at −15°C. Recovery of growth after thawing and transferring to fresh medium at 20°C indicated survival. All isolates in the Blastocladiales and Spizellomycetales survived freezing in all tests. All isolates in the Chytridiales also survived freezing in some tests. None of the isolates in the Rhizophydiales survived freezing in any of the tests. However, some isolates in the Rhizophydiales recovered growth after freezing if they were grown on PYG agar supplemented with either 1% sodium chloride or 1% glycerol prior to freezing. After freezing, the morphology of the thalli of all isolates was observed under LM. In those isolates that recovered growth after transfer to fresh media, mature zoosporangia were observed in the monocentric isolates and resistant sporangia or resting spores in the polycentric isolates. Encysted zoospores in some monocentric isolates also survived freezing. In some of the experiments the freezing and thawing process caused visible structural damage to the thalli. The production of zoospores after freezing and thawing was also used as an indicator of freeze tolerance. The chytrids in this study responded differently to freezing. These data add significantly to our limited knowledge of freeze tolerance in chytrids but leave many questions unanswered. [Copyright &y& Elsevier]

Abstract: Chytrids are very important components of freshwater ecosystems, but the ecological significance of this group of fungi is not well understood. This review considers some of the significant environmental factors affecting growth and population composition of chytrids in aquatic habitats. The physical factors include primarily salinity, dissolved oxygen concentration and temperature. The biological factors include the role of chytrids as saprobes and parasites and methods of dispersal of propagules throughout the ecosystem. Dispersal depends upon both zoospores for short range and whole thalli for long range dispersal. Five roles for chytrids in food-web dynamics are proposed: (1) chytrid zoospores are a good food source for zooplankton, (2) chytrids decompose particulate organic matter, (3) chytrids are parasites of aquatic plants, (4) chytrids are parasites of aquatic animals and (5) chytrids convert inorganic compounds into organic compounds. New molecular methods for analysis of chytrid diversity in aquatic environments have the potential to provide accurate quantitative data necessary for better understanding of ecological processes in aquatic ecosystems. [Copyright &y& Elsevier]

Abstract: Methods for the preservation of fungi in the Chytridiomycota in culture collections are reviewed in this paper. The Chytridiomycota can be preserved with varying degrees of success using a number of different protocols including cryopreservation. The survival of fungi in the Chytridiomycota is sensitive to environmental factors such as lack of moisture, high temperatures, high osmotic potential, and availability of oxygen, all of which must be considered in designing preservation methods. The age of the culture at the initiation of preservation appears to be a particularly important determinant of viability. Recently, commonly used methods for preservation of other groups of fungi have been modified to improve the survival of the Chytridiomycota in culture collections. High rates of survival have been reported after cryopreservation of aerobic and anaerobic chytrids in 10 % glycerol or dimethyl sulphoxide as cryoprotectants. The rates of freezing and thawing must be carefully controlled in the methods for cryopreservation considered in this review. Further research on increasing long-term survival rates and morphological, physiological and genetic stability of Chytridiomycota at low temperatures is necessary. [Copyright &y& Elsevier]

Abstract: Twenty isolates from soil in the orders Spizellomycetales, Blastocladiales and Chytridiales (Chytridiomycota) grew on complex solid media supplemented with 10gl−1 sodium chloride. In a synthetic liquid medium, 4.4gl−1 sodium chloride strongly inhibited growth in three of the five isolates, possibly because of the effect of the ions or osmolarity of the solution. The maximum concentration for growth in synthetic liquid medium with different osmotic potentials using polyethylene glycol (PEG) varied considerably amongst the isolates. Three patterns of growth with increasing concentrations of PEG were evident among isolates within the genus Rhizophydium. Up to the concentration where growth ceased, the dry weight of each isolate either decreased, remained constant, or in one case, increased. Most of the fungi survived when incubated at room temperature for 7d in complex liquid media supplemented with 35gl−1 sodium chloride or 300gl−1 PEG. These data indicate that soil Chytridiomycota can survive various osmotic potentials that may occur during the wetting and drying phases in soils. [Copyright &y& Elsevier]

Abstract: Sixteen isolates in the orders Blastocladiales, Chytridiales, Rhizophydiales and Spizellomycetales were incubated for 2d in liquid PYG growth medium at 33, 37, 40, 45 and 50°C. These fungi could not resume growth when returned to 20°C if the temperature of incubation was more than a few degrees above the maximum temperature for growth on solid PYG growth medium. The maximum temperatures for survival of some chytrids are probably close to the temperatures reached periodically on the surface of moist soils in warm climates. Desiccated thalli of chytrids in the Blastocladiales and Spizellomycetales can survive much higher temperatures than chytrids in the Chytridiales and Rhizophydiales. Therefore, the maximum temperature and moisture content of the soil could significantly affect the diversity of chytrids in the ecosystem. [Copyright &y& Elsevier]

This study examined the responses of a group of four zoosporic true fungi isolated from soils in NSW Australia, to concentrations of toxic metals in the laboratory that may be found in polluted soils. All isolates showed greatest sensitivity to Cu and least sensitivity to Pb. All isolates showed significant reduction in growth at 60 ppm (0.94 mmol m −3 ) for Cu, while three declined significantly at 60 ppm (0.92 mmol m −3 ) Zn. The growth of two isolates declined significantly at 100 ppm (0.48 mmol m −3 ) Pb and one at 200 ppm (0.96 mmol m −3 ) Pb. The rate of production of zoospores for all isolates was reduced when sporangia were grown in solid PYG media with 60 ppm Cu. Three isolates significantly declined in production at 60 ppm Zn and three at 100 ppm Pb. All isolates recovered growth after incubation in solid media with 60 ppm Zn or 100 ppm Pb. Two isolates did not recover growth after incubation in 60 ppm Cu. If these metals cause similar effects in the field, Cu, Pb, and Zn contamination of NSW soils is likely to reduce biomass of zoosporic true fungi. Loss of the fungi may reduce the rate of mineralisation of soil organic matter. [ABSTRACT FROM AUTHOR]

Marine disease ecology is a growing field of research, particularly for host organisms negatively impacted by a changing climate and anthropogenic activities. A decrease in health and increase in susceptibility to disease has been hypothesised as the mechanism behind wide-spread seagrass die-offs related to wasting disease in the past. However, seagrass wasting disease and the causative pathogen, Labyrinthula , have been vastly understudied in the southern hemisphere. Our aim was to build on the current knowledge of Australian Labyrinthula descriptions and phylogeny, while also providing a first look at wasting disease ecology in Australia. Five seagrass species along a 750 km stretch of coastline in southeastern Australia were sampled. The resulting 38 Labyrinthula isolates represented a diversity of morphotypes and five haplotypes of varying phylogenetic clade positions and virulence. The haplotypes clustered with previously-described phylogenetic clades containing isolates from Asia, USA and Europe. Pathogenicity tests confirmed, for the first time, the presence of at least two pathogenic haplotypes in Australia. While historically there have been no reports of wasting disease-related seagrass habitat loss, the presence of pathogenic Labyrinthula highlights the need for disease monitoring and research to understand seagrass wasting disease ecology in Australia. [ABSTRACT FROM AUTHOR]

Abstract: The Blastocladiomycota is a recently described phylum of ecologically diverse zoosporic fungi whose species have not been thoroughly sampled and placed within a molecular phylogeny. In this study, we investigated the phylogeny of the Blastocladiomycota based on ribosomal DNA sequences from strains identified by traditional morphological and ultrastructural characters. Our results support the monophyly of the Coelomomycetaceae and Physodermataceae but the Blastocladiaceae and Catenariaceae are paraphyletic or polyphyletic. The data support two clades within Allomyces with strains identified as Allomyces arbusculus in both clades, suggesting that species concepts in Allomyces are in need of revision. A clade of Catenaria species isolated from midge larvae group separately from other Catenaria species, suggesting that this genus may need revision. In the Physodermataceae, Urophlyctis species cluster with a clade of Physoderma species. The algal parasite Paraphysoderma sedebokerensis nom. prov. clusters sister to other taxa in the Physodermataceae. Catenomyces persicinus, which has been classified in the Catenariaceae, groups with the Chytridiomycota rather than Blastocladiomycota. The rDNA operon seems to be suitable for classification within the Blastocladiomycota and distinguishes among genera; however, this region alone is not suitable to determine the position of the Blastocladiomycota among other basal fungal phyla with statistical support. A focused effort to find and isolate, or directly amplify DNA from additional taxa will be necessary to evaluate diversity in this phylum. We provide this rDNA phylogeny as a preliminary framework to guide further taxon and gene sampling and to facilitate future ecological, morphological, and systematic studies. [Copyright &y& Elsevier]