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As a result of anthropogenic influences and global climate change, emerging infectious marine diseases are thought to be increasingly more common and more severe than in the past. The aim of our investigation was to confirm the presence of Labyrinthula, the aetiological agent of the seagrass wasting disease, in Southeastern Australia and provide the first isolation and characterisation of this protist, in Australia. Colonies and individual cells were positively identified as Labyrinthula using published descriptions, diagrams, and photographs. Their identity was then confirmed using DNA barcoding of a region of the 18S rRNA gene. Species level identification of isolates was not possible as the taxonomy of the Labyrinthula is still poorly resolved. Still, a diversity of Labyrinthula was isolated from small sections of the southeast coast of Australia. The isolates were grouped into three haplotypes that are biogeographically restricted. These haplotypes are closely related to previously identified saprotrophic clades. The study highlights the need for further investigation into the global distribution of Labyrinthula, including phylogenetic pathogenicity and analysis of host-parasite interactions in response to stressors. Given the results of our analyses, it is prudent to continue research into disease and epidemic agents to better prepare researchers for potential future outbreaks. [ABSTRACT FROM AUTHOR]

In the forthcoming decades, it is widely believed that the dominance of colonial and filamentous bloom-forming cyanobacteria (e.g. M icrocystis, P lanktothrix, A nabaena and C ylindrospermopsis) will increase in freshwater systems as a combined result of anthropogenic nutrient input into freshwater bodies and climate change. While the physicochemical parameters controlling bloom dynamics are well known, the role of biotic factors remains comparatively poorly studied. Morphology and toxicity often - but not always - limit the availability of cyanobacteria to filter feeding zooplankton (e.g. cladocerans). Filamentous and colonial cyanobacteria are widely regarded as trophic dead-ends mostly inedible for zooplankton, but substantial evidence shows that some grazers (e.g. copepods) can bypass this size constraint by breaking down filaments, making the bloom biomass available to other zooplankton species. A wide range of algicidal bacteria (mostly from the A lcaligenes, F lavobacterium/ C ytophaga group and P seudomonas) and viruses ( P odoviridae, S iphoviridae and M yoviridae) may also contribute to bloom control, via their lytic activity underpinned by a diverse array of mechanisms. Fungal parasitism by the Chytridiomycota remains the least studied. While each of these biotic factors has traditionally been studied in isolation, emerging research consistently point to complex interwoven interactions between biotic and environmental factors. [ABSTRACT FROM AUTHOR]

The survival of an isolate of Hyphochytrium catenoides collected from soil in the Blue Mountains in eastern New South Wales, Australia, was tested under extreme conditions in the laboratory. This isolate recovered growth after being subjected to drying on filter paper, to heat while desiccated, to hypersalinity, to strict anaerobic conditions, to freezing temperatures, and to a short period in solutions at pH 2.8–11.2. The capacity to survive under these conditions in the laboratory suggests adaptation to fluctuating conditions in the soil. The partial DNA sequence of the 28S ribosomal RNA gene in the isolate from New South Wales was 98% similar to that in an isolate from Arizona with a similar morphology. [ABSTRACT FROM AUTHOR]

Four aquatic fungi - Apodachlya brachynema and A. minima (Leptomitales), Aphanomyces laevis (Saprolegniales), and Pythium ultimum (Peronosporales) - were tested for growth in synthetic media containing one of a variety of carbon sources. Apodachlya brachynema readily utilized five amino acids - alanine, glutamate, aspartate, proline and leucine - as well as glucose and acetate. Growth on sucrose as a carbon source was slight. Apodachlya minima differed from A. brachynema in that it could not utilize proline and leucine. Aphanomyces laevis grew well on only three of the substrates tested - glucose, alanine and glutamate. Pythium ultimum utilized glucose, sucrose, maltose, cellobiose, alanine, glutamate, aspartate, proline asparagine, ornithine, and serine, but not eight other amino acids. All of these fungi hydrolyzed gelatin. Radioactively labeled carbon dioxide was released during incubation of Aphanomyces laevis in media containing labeled leucine, proline, or phenylalanine. These data provide evidence of some catabolism of the three substrates although none of these substrates can support the growth of Aphanomyces laevis as a sole source of carbon and nitrogen. [ABSTRACT FROM AUTHOR]

Four fungi in the order Saprolegniales - Saprolegnia sp., Achlya ambisexualis, Leptolegnia eccentrica and Dictyuchus sterile - were tested for growth in synthetic media containing one of the following carbon sources: glucose, maltose, sucrose, alanine, proline, glutamate, leucine, arginine and phenylalanine. All of these compounds were effective substrates for one or more of the four fungi. The ability of Saprolegnia sp. to utilize other substrates was studied. Saprolegnia sp. can metabolize soluble starch, fructose, ornithine, aspartate, serine, and lysine but did not grow on galactose and eight additional amino acids. [ABSTRACT FROM AUTHOR]

A comparative study of terminal respiration was undertaken in five genera of aquatic fungi in the Leptomitales. The cytochrome system in this group of fungi contained cytochrome a-a3 (605 nm), cytochrome c (551 nm), cytochrome b (557 nm), and cytochrome b (564 nm). A representative of each of three aerobic genera, Leptomitus, Apodachlya, and Sapromyces, had a total cytochrome content of about 2 × 10-10 mol/mg dry weight. An endogenous respiration rate of 21 μl O2 uptake/(h × mg dry weight) at 21.7°C was found in Leptomitus and Apodachlya and 14 in Sapromyces. The strain belonging to the fermentative genus Mindeniella had approximately one-third of the total cytochrome content and one-third of the endogenous respiration rate observed in Leptomitus and Apodachlya. Mindeniella and Sapromyces contained less total cytochrome when grown under reduced oxygen tension than when grown in air. Only about one-half of the b-type cytochrome was veducible by endogenous substrates. Both cytochrome a3 and an unidentified pigment bound CO. The endogenous respiration of Leptomitus, Apodachlya, and Sapromyces was strongly inhibited by sodium cyanide, sodium azide, antimycin A, and sodium fluoroacetate. [ABSTRACT FROM AUTHOR]

The endogenous respiration of six members of Saprolegniaceae (Oomycetes), Saprotegnia sp., Thraustotheca sp., Achlya sp., Dichtynchus sp., Aphanomyces euteiches, and A. astaci were studied in the presence and in the absence of exogenous substrate using conventional manometric techniques. Glucose stimulated the rate of oxygen uptake of unstarved mycelia to some extent in all the fungi. Attempts to increase the weak stimulation of respiration by glucose in A. astaci were not successful. The respiratory quotients of the fungi tested were usually in the range of 0.7 to 0.9 (luring endogenous respiration, and addition of glucose increased these values inure than expected. L-leucine and L-glutamic acid stimulated respiration of A. astaci only when the fungus was starved, and acetic acid and butyric acid were inhibitory. Fructose and acetic acid increased respiration in starved mycelium of A. euteiches while L-leucine and L-glutamic acid had little effect. Antimycin A, HOQNO, HCN, and fluoroacetate strongly inhibited endogenous oxygen uptake by A. astaci. Amytal and azide were also markedly inhibitory while rotenone and CO had little effect. DNP and diphenylamine inhibited respiration at a high concentration but at a lower concentration DNP was stimulatory. In contrast the respiration of Saprolegnia sp. was resistant to cyanide, antimycin A, and HOQNO. Spectrophotometric observations on homogenized mycelia of Saprolegnia sp. and of A. astaci indicated the presence of cytochrome c (551 nm), two b-type cytochromes (557 and 564 nm) and cytochrome a-a3 (605 nm) all in approximately equimolar concentrations. In both strains CO combined with cytochrome a3 and an unidentified pigment. A remarkable similarity in the cytochrome system seems to exist between these two strains and some members of the Leptomitales. [ABSTRACT FROM AUTHOR]