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At least 127 records · Page 7Linked to original sources
PubMed1998

Evolution of spore release mechanisms in the saprolegniaceae (Oomycetes): evidence from a phylogenetic analysis of internal transcribed spacer sequences

Classical studies on spore release within the Saprolegniaceae (Oomycetes) led to the proposition that different mechanisms of sporangial emptying represent steps in an evolutionary transition series. We have reevaluated this idea in a phylogenetic framework using internal transcribed spacer sequences of four genera. These data were compared with the response to osmotic stress exhibited by each taxon. Saprolegnia emerges as the most basal genus, sister to Achlya, Thraustotheca, and Dictyuchus. Achlya and Thraustotheca are most closely related, while Dictyuchus appears to have evolved along a separate evolutionary lineage. The resulting phylogenetic framework is consistent with the idea that the mechanism of sporangial emptying exhibited by Saprolegnia represents the plesiomorphic condition from which the other mechanisms were derived independently. These alternative mechanisms of spore release may have resulted from a small number of mutations that inhibited axonemal development and altered the temporal and spatial expression of lytic enzymes that degrade the sporangial wall. Copyright 1998 Academic Press.

Journal Article↗
PubMed1985

Immunological evidence that the nonhormone binding component of avian steroid receptors exists in a wide range of tissues and species.

A monoclonal antibody to a fungal protein has been used to demonstrate the presence of the nonhormone binding component of molybdate-stabilized steroid receptors in a variety of vertebrate tissues. We recently identified a steroid receptor in the aquatic fungus Achlya ambisexualis where sexual morphogenesis of the male is directed by the steroid antheridiol. This receptor resembles receptors of higher organisms in exhibiting an 8S, molybdate-stabilized form. In the chick oviduct, a 90 000 molecular weight protein has previously been shown to be associated with the molybdate-stabilized complex of the progesterone receptor. We have isolated a similar protein of molecular weight about 88 000 from A. ambisexualis and have obtained a hybridomal-derived monoclonal antibody directed against it. This mouse anti-Achlya immunoglobulin G1 (IgG1) cross-reacts with the 90 000 molecular weight protein in chick oviduct cytosol and was used to detect analogous 90 000 molecular weight proteins in mammalian tissues. Tissue cytosols were incubated with antibody, and the complexes were isolated onto protein A-Sepharose. The resin-bound proteins were then analyzed by gel electrophoresis. This procedure revealed the presence of 90 000 molecular weight proteins in several mammalian tissues including rat liver, mouse liver and uterus, pig ovarian granulosa cells, human endometrium, and HeLa cells. These results demonstrate that the 90 000 molecular weight protein is not peculiar to the chick oviduct but is present in several different tissues from a variety of animals. This antibody should be a useful probe for further studies on the biological role of these proteins.

Animals↗
PubMed1996

Control of microbiological quality and shelf-life of catfish (Clarias gariepinus) by chemical preservatives and smoking.

Fresh catfish (Clarias gariepinus) were subjected to different concentrations of sodium benzoate or potasium sorbate and smoked traditionally before evaluation for microbiological, chemical and organoleptic characteristics during ambient tropical storage. Unsmoked fish samples showed diverse microflora (Enterobacter, Escherichia, Serratia, Bacillus, Staphylococcus, Streptococcus, Penicillium, Aspergillus and Achlya genera) while smoked samples were dominated by Gram-positive bacterial flora (Bacillus, Staphylococcus and Streptococcus) and spoilage moulds (Penicillium verrucosum, Aspergillus flavus and Achlya spp.). Significant reduction in microbial population occurred in most samples following smoking with samples subjected to 0.4% (w/v) potassium sorbate showing the lowest microbial load and maximum shelf-stability. However, marked microbial increase occurred after day 4 of storage in control and benzoate-treated samples. Changes in pH were marginal but decreased after day 12 of storage. Moisture content decreased sharply after smoking and remained low after day 4 of storage. Overall, potassium sorbate treatment (0.4% w/v) was most effective in controlling microbial quality and extended the shelf-life of the samples by 8 d.

Animals↗
PubMed2004

[Water fungi occurence in the River Supraśl-bath Jurowce near Białystok].

Studies on the occurrence of aquatic fungi in the bathing sites of the Supraśl River in Jurowce village were collected in years 2000-2003. Hydrochemical analysis was performed using standard methods. Bait method was used to isolate the fungi. In the Supraśl River at Jurowce village 36 fungi species were identified, among them fish pathogens Achlya orion, Aphanomyces laevis, Dictyuchus monosporus, Saprolegnia ferax, Saprolegnia monoica, S. parasitica, human pathogens Aspergillus flavus, Candida albicans, Lagenidium humanum, Penicillium mycetomagenum, Rhizophydium keratinophilum and Trichosporon cutaneum, phytopathogens Achlya racemosa, Phytophthora gonapodoides, Pythium butleri, P. myriotylum and P. debaryanum. Physicochemical parameters of waters in Supraśl River-bathing sites had no important effect on the occurrence of fungi.

Animals↗
PubMed1997

[Seasonal variation of three Culex species (Diptera: Culicidae) and its parasites and pathogens in Punta Lara, Buenos Aires, Argentina].

The seasonality of immatures, imagoes and pathogens of Culex dolosus Lynch Arribálzaga, Culex intrincatus Brethes and Culex maxi Dyar from Punta Lara (Buenos Aires province, Argentina) was monitored weekly (larvae and pupae) or fortnightly (adults), from 1989 to 1991. Culex dolosus was present during all months. The larvae were parasitized by Geotrichum candidum Link ex Person, Smittium morbosum var. rioplatensis López Lastra, Coelomomyces sp., Achlya sp, Amblyospora dolosi García & Becnel and Strelkovimermis spiculatus Poinar & Camino. Conidia of Hyphomycetes, filarial worms of Onchocercidae and S. spiculatus were detected in adults. Cx. intrincatus was present from January to May; the immatures were parasitized by G. candidum, S. morbosum, Achlya sp. and Amblyospora sp. Larvae of Cx. maxi were collected from January to April, and adults in all months except for June and July. S. morbosum was the only parasite found in this mosquito.

Animals↗
PubMed2004

Turgor regulation in hyphal organisms.

Turgor regulation in two saprophytic hyphal organisms was examined directly with the pressure probe technique. The ascomycete Neurospora crassa, a terrestrial fungi, regulates turgor after hyperosmotic treatments when growing in a minimal medium containing K(+), Mg(2+), Ca(2+), Cl(-), and sucrose. Turgor recovery by N. crassa after hyperosmotic treatment is concurrent with changes in ion transport: hyperpolarization of the plasma membrane potential and a decline in transmembrane ion conductance. In contrast the oomycete Achlya bisexualis, a freshwater hyphal organism, does not regulate turgor after hyperosmotic treatment, although small transient increases in turgor were occasionally observed. We also monitored turgor in both organisms during hypoosmotic treatment and did not observe a turgor increase, possibly due to turgor regulation. Both hyphal organisms grow with similar morphologies, cellular expansion rates and turgor (0.4-0.7 MPa), yet respond differently to osmotic stress. The results do not support the assumption of a universal mechanism of tip growth driven by cell turgor.

Achlya↗
PubMed1990

Occurrence of zoosporic and terrestrial fungi in some ponds of Kharga Oases, Egypt.

Thirty-nine species belonging to 13 genera of zoosporic fungi were collected from 33 water samples on sesame and hemp seeds as baits at 22 degrees C. Five genera were isolated in high occurrence: Allomyces (2 species), Achlya (9 species), Dictyuchus (4 species), Pythium (5 species) and Saprolegnia (5 species). Aphanomyces (4 species) and Isoachlya (2 species) were of moderate frequencies. The remaining six genera were less frequent: Anisolpidium, Brevilegnia, Calyptralegnia, Leptolegnia, Pythiopsis and Thraustotheca. Sixty-six species and 2 varieties belonging to 34 genera were identified on glucose-(24 genera and 52 species + 1 variety) and cellulose (31 genera and 48 species + 2 varieties) Czapek Dox agar at 28 degrees C. The most common species on the two media were Acremonium strictum, Aspergillus flavus, A. fumigatus, A. niger, Fusarium moniliforme, F. oxysporum, F. solani, Mucor racemosus, Penicillium chrysogenum and P. corylophilum. Some fungi were common only on cellulose agar medium such as Chaetomium globosum, C. spirale and Memnoniella echinata.

Egypt↗
PubMed1991

Mycoflora associated with five species of freshwater leeches.

Twenty-two species belonging to 11 genera of zoosporic fungi were collected from 10 freshwater sites and from five species of leeches on sesame and hemp seeds, maize grains and Pinus pollen grains as baits at 22 degrees C. Dictyuchus, Achlya, Pythium, Allomyces and Saprolegnia were the most common genera. The highest population of zoosporic fungi was estimated from Batracobdelloides tricarinata, the lowest from Barbronia assiuti. In addition fifty-three species and 1 variety representing 23 terrestrial fungal genera were identified on glucose (17 genera and 41 species) and cellulose (20 genera and 34 species + 1 variety) Czapek's Dox agar at 28 degrees C. The most common species on the two media were Aspergillus niger, A. fumigatus, A. flavus, Trichoderma harzianum, Gibberella fujikuroi and Penicillium chrysogenum. Some fungi were common only on cellulose agar medium such as Botryotrichum atrogriseum, Chaetomium bostrychodes, Dactylella alaskana and Drechslera halodes. Batracobdelloides tricarinata was the richest with terrestrial fungi whereas Salifa delicata was the poorest. Five leech species, namely Alboglossiphonia polypompholyx, Batracobdelloides tricarinata, Helobdella conifera, Barbronia assiuti and Salifa delicata were used during this investigation.

Animals↗
PubMed1982

Seasonal fluctuations of freshwater fungi in river Nile (Egypt).

The seasonal fluctuations of aquatic fungi were studied over 24 water sample collected monthly between May 1979 and April 1981 from the River Nile near Assiut (about 375 km, south from Cairo, Egypt). The richest periods in aquatic fungal genera and species were September--December 1979, January--March, October--December 1980, and January--April 1981. These periods represent low or moderate temperature months. The poorest periods were May--August 1979, April, May, July, August and September 1980 which are almost summer months. Twenty-nine species and one variety of Olpidiopsis saprolegniae which belong to ten genera of aquatic fungi were collected during this investigation. Three genera were of high seasonal occurrence (19-24 months) namely: Achlya, Saprolegnia and Dictyuchus. Three other genera were of moderate seasonal occurrence (6-11 months) namely: Isoachlya, Leptolegnia and Pythium. The rest of genera were of low or rare seasonal occurrence.

Egypt↗
PubMed1983

Water-borne fungi in the River Inn, Innsbruck (Austria).

Pythium, Saprolegnia and Achlya were the basic components of the river mycoflora. Occurrence and periodicity of the fungal genera and species exhibited three different patterns during the different months of this investigation.

Austria↗
PubMed1997

Vacuolar reticulum in oomycete hyphal tips: An additional component of the Ca2+Regulatory system?

Cultures of Achlya sp., Phytophthora cinnamomi, Saprolegnia diclina, S. ferax, and S. parasitica, treated with 6-carboxyfluorescein diacetate solution, accumulate 6-carboxyfluorescein in a reticulate system of fine tubules. The network shows longitudinal polarity within the hyphae, tubules being finest toward the hyphal tips. In more mature subapical regions the network is connected with large vacuoles that also accumulate 6-carboxyfluorescein. A morphologically similar system has also been identified in freeze-substituted hyphae of S. ferax. The network is considered to be vacuolar, but differs from the tubular vacuole system of true fungi in that tubules are less motile, more frequently branched, and do not alternate with clusters of spherical vacuoles. The appearance of the network resembles patterns of calcium-sensitive dye staining and it is suggested that the vacuolar reticulum in the tip region of oomycete hyphae may act as a Ca2+ sink. The tubular reticulum in oomycetes is very fragile and can be shown with 6-carboxyfluorescein in only those hyphal tips with a motility and organelle distribution characteristic of growing hyphae with normal morphology. Diverse abnormal hyphae show a range of other fluorochrome localizations. These include large irregular compartments filled with fluorochrome, and fluorescent cytoplasm with organelles and vacuoles standing out in negative contrast. These localizations in abnormal hyphae are correlated with other structural changes indicative of damage. Special care is required in experiments with oomycetes to avoid such artefacts of localization. Copyright 1997 Academic Press. Copyright 1997 Academic Press

Journal Article↗
PubMed1994

Sequence analysis of duplicated actin genes in Lagenidium giganteum and Pythium irregulare (Oomycota).

Southern analysis of genomic DNA identified multiple-copy actin gene families in Lagenidium giganteum and Pythium irregulare (Oomycota). Polymerase chain reaction (PCR) protocols were used to amplify members of these actin gene families. Sequence analysis of genomic coding regions demonstrated five unique actin sequences in L. giganteum (Lg-Ac1, 2, 3, 4, 5) and four unique actin sequences in P. irregulare (Pi-Ac1, 2, 3, 4); none were interrupted by introns. Maximum parsimony analysis of the coding regions demonstrated a close phylogenetic relationship between oomycetes and the chromophyte alga Costaria costata. Three types of actin coding regions were identified in the chromophyte/oomycete lineage. The type 1 actin is the single-copy coding region found in C. costata. The type 2 and type 3 actins are found in the oomycetes and are the result of a gene duplication which occurred soon after the divergence of the oomycetes from the chromophyte algae. The type 2 coding regions are the single-copy sequence of Phytophthora megasperma, the Phytophthora infestans actB gene, Lg-Ac5 and Pi-Ac2. The type 3 coding regions are the single-copy sequence of Achlya bisexualis, the P. infestans actA gene, Lg-Ac1, 2, 3, 4 and Pi-Ac1, 3, 4.

Actins↗
PubMed1992

Regulatory sequences for expressing genes in oomycete fungi.

Promoter and terminator sequences from a range of species were tested for activity in the oomycetes, a group of lower fungi that bear an uncertain taxonomic affinity to other organisms and in which little is known of the sequences required for transcription. Transient assays, using the reporter gene beta-glucuronidase (GUS), were used to examine the function of these promoters and terminators in the plant pathogens Phytophthora infestans and P. megasperma f. sp. glycinea, and in the saprophytic water mold, Achlya ambisexualis. Oomycete promoters, isolated from the ham34 and hsp70 genes of Bremia lactucae and the actin gene of P. megasperma f. sp. glycinea, resulted in high levels of GUS accumulation in each of the three oomycetes. In contrast, little or no activity was detected when promoters from higher fungi (four ascomycetes and one basidiomycete), plants, and animals were tested. The terminator from the ham34 gene resulted in much higher levels of GUS accumulation than did others, although an oomycete terminator was not absolutely required for expression. Transcript mapping of RNA from stable transformants confirmed accurate initiation from the B. lactucae hsp70 promoter and termination within 3' ham34 sequences in P. infestans. Our results indicate that the transcriptional machinery of the oomycetes differs significantly from that of the higher fungi, but that enough conservation exists within the class to allow vectors developed from one oomycete species to be used for others.

Base Sequence↗
PubMed1978

The insensitivity of mushroom nuclear RNA polymerase activity to inhibition by amatoxins.

Nuclear fractions isolated from Amanita phalloides, Amanita muscaria and Agaricus bisporus were subjected to in vitro RNA synthesis assays in the presence of various concentrations of amatoxins. The mushroom nuclei were highly insensitive to inhibition by amatoxin when compared to assays of nuclear fractions isolated from the Oömycete fungus, Achlya ambisexualis and from rabbit brain.

Agaricales↗
PubMed1995

Fungal diseases of fish in Nanak Sagar, Naini Tal, India.

Eight zoosporic fungi viz., Achlya debaryana, A. flagellata, A. klebsiana, Aphanomyces laevis, Saprolegnia diclina, S. ferax, S. parasitica, and Pythium sp. were isolated from a large number of adult fishes of the species Mastacembelus armatus, Mystus vitatus, Nandus nandus, Tor putitora and T. tor of Nanak Sagar reservoir in Naini Tal district, India. Species of the parasites and the hosts were different in their pathogenicity and immunity, respectively. However, A. flagellata and S. parasitica appeared to be the most virulent. The severity of mycosis was primarily correlated to moderate water temperatures of 22-25 degrees C. High temperature (> 28 degrees C) retarded the disease process. The experimental inoculation with all the associated fungal species on Puntius conchonius in the laboratory produced clinical signs similar to the ones seen on infected fish in the reservoir. This is the first report on fish mycosis in the large reservoir located in the foot hill of Kumaun Himalaya.

Animals↗
PubMed1995

Experimental transmission and pathogenicity of some zoosporic fungi to Tilapia fish.

Seventeen fungal species belong to sex genera were recovered from the four organs of Tilapia fish and the most common were Saprolegnia ferax, S. diclina, Achlya dubia, A. americana, A. racemosa and A. flagellata, Dictyuchus sterile, Pythium undulatum and Aphanomyces sp. Severe infection followed by death of all fish was incited by S. parasitica and S. ferax through experiment I. 30-70% of T. nilotica and T. galileae were killed through experiment II by S. parasitica and S. ferax. T. galileae was more susceptible to fungal infection than T. nilotica.

Animals↗
PubMed1988

Ionic currents in morphogenesis.

Morphogenetic fields must be generated by mechanisms based on known physical forces which include gravitational forces, mechanical forces, electrical forces, or some combination of these. While it is unrealistic to expect a single force, such as a voltage gradient, to be the sole cause of a morphogenetic event, spatial and temporal information about the electrical fields and ion concentration gradients in and around a cell or embryo undergoing morphogenesis can take us one step further toward understanding the entire morphogenetic mechanism. This is especially true because one of the handful of identified morphogens is Ca2+, an ion that will not only generate a current as it moves, but which is known to directly influence the plasma membrane's permeability to other ions, leading to other transcellular currents. It would be expected that movements of this morphogen across the plasma membrane might generate ionic currents and gradients of both electrical potential and intracellular concentration. Such ionic currents have been found to be integral components of the morphogenetic mechanism in some cases and only secondary components in other cases. My goal in this review is to discuss examples of both of these levels of involvement that have resulted from investigations conducted during the past several years, and to point to areas that are ripe for future investigation. This will include the history and theory of ionic current measurements, and a discussion of examples in both plant and animal systems in which ionic currents and intracellular concentration gradients are integral components of morphogenesis as well as cases in which they play only a secondary role. By far the strongest cases for a direct role of ionic currents in morphogenesis is the polarizing fucoid egg where the current is carried in part by Ca2+ and generates an intracellular concentration gradient of this ion that orients the outgrowth, and the insect follicle in which an intracellular voltage gradient is responsible for the polarized transport from nurse cell to oocyte. However, in most of the systems studied, the experiments to determine if the observed ionic currents are directly involved in the morphogenetic mechanism are yet to be done. Our experience with the fucoid egg and the fungal hypha of Achlya suggest that it is the change in the intracellular ion concentration resulting from the ionic current that is critical for morphogenesis.

Animals↗
PubMed1977

Inhibition of DNA synthesis by cycloheximide and blasticidin-S is independent of their effect on protein synthesis.

The effects of cycloheximide and related glutarimide antibiotics on DNA synthesis in Achlya bisexualis Coker and A. Couch were compared to those of other protein synthesis inhibitors, puromycin, p-fluorophenylalanine and blasticidin-S. The inhibitors had no significant effects on intrahyphal pool sizes of dTTP, dCTP, ATP, UTP and CTP, nor on the specific activity of the dTTP pool labelled by [3H] thymidine. DNA was the sole acid-insoluble product of [3H]-thymidine incorporation. Cycloheximide, isocycloheximide, streptimidone and blasticidin-S inhibited DNA synthesis rapidly and completely and anhydrocycloheximide was less effective. Cycloheximide acetate, puromycin and p-fluorophenylalanine did not inhibit DNA synthesis. It is concluded that the effects of the several glutarimide antibiotics and of blasticidin-S on DNA synthesis were independent of their effects on protein synthesis.

Anti-Bacterial Agents↗