New pyranonaphthazarin and 2-naphthoic acid derivatives from the mangrove endophytic fungus Leptosphaerulina sp. SKS032

Two new compounds, named leptospyranonaphthazarin A (1) and leptosnaphthoic acid A (2), together with four known compounds (3–6) were isolated from an endophytic fungus Leptosphaerulina sp. SKS032. Their structures were assigned using spectroscopic methods, computational methods, and single-crystal X-ray diffraction analysis. In the antibiotic assay, compounds 1, 2, and 6 exhibited antibacterial activities against Staphylococcus aureus with minimal inhibitory concentration (MIC) values of 25.0, 50.0, and 50.0 μg/mL, respectively.     

New Family,Genus, and Species of Microsporida (Protozoa: Microsporida) from the Tropical Fire Ant,Solenopsis geminata (Fabricius) (Insecta: Formicidae)*

SYNOPSIS. A new species of Microsporida, Burenella dimorpha sp. n., representing a new family, Burenellidae fam. n. and genus, is described on the basis of light- and electron-microscope observations. The family is characterized by 2 sequences of sporogony, each sequence having morphologically different sporonts and spores. The parasite infects the tropical fire ant, Solenopsis geminata (Fabricius), producing distinct pathologic manifestations (clearing of the cuticle and eye malformation) and death in the pupal stage of development. Transmission of the infection per os to healthy S. geminata, to the Southern fire ant, Solenopsis xyloni McCook, and to the red and black imported fire ants, Solenopsis invicta Buren and Solenopsis richteri Forel, is reported.     

Purification and characterization of thermostable pectate-lyases from a newly isolated thermophilic bacterium, Thermoanaerobacter italicus sp. nov.

A novel thermophilic spore-forming anaerobic microorganism (strain Ab9) able to grow on citrus pectin and polygalacturonic acid (pectate) was isolated from a thermal spa in Italy. The newly isolated strain grows optimally at 70°C with a growth rate of 0.23 h⁻¹ with pectin and 0.12 h⁻¹ with pectate as substrates. Xylan, starch, and glycogen are also utilized as carbon sources and thermoactive xylanolytic (highest activity at 70°–75°C), amylolytic as well as pullulolytic enzymes (highest activity at 80°–85°C) are formed. Two thermoactive pectate lyases were isolated from the supernatant of a 300-l culture of isolate Ab9 after growth on citrus pectin. The two enzymes (lyases a and b) were purified to homogeneity by ammonium sulfate treatment, anion exchange chromatography, hydrophobic chromatography and finally by preparative gel electrophoresis. After sodium dodecylsulfate (SDS) gel electrophoresis, lyase a appeared as a single polypeptide with a molecular mass of 135 000 Da whereas lyase b consisted of two subunits with molecular masses of 93 000 Da and 158 000 Da. Both enzymes displayed similar catalytic properties with optimal activity at pH 9.0 and 80°C. The enzymes were very stable at 70°C and at 80°C with a half-life of more than 60 min. The maximal activity of the purified lyases was observed with orange pectate (100%) and pectate-sodium salt (90%), whereas pectin was attacked to a much lesser extent (50%). The K _m values of both lyases for pectate and citrus pectin were 0.5 g·l⁻¹ and 5.0 g·l⁻¹, respectively. After incubation with polygalacturonic acid, mono-, di-, and tri-galacturonate were detected as final products. A 2.5-fold increase of activity was obtained when pectate lyases were incubated in the presence of 1 mM Ca²⁺. The addition of 1 mM ethylenediaminetetraacetic acid (EDTA) resulted in complete inhibition of the enzymes. These heat-stable enzymes represent the first pectate-lyases isolated and characterized from a thermophilic anaerobic bacterium. On the basis of the results of the 16S rRNA sequence comparisons and the observed phenotypic differences, we propose strain Ab9 as a new species of Thermoanaerobacter, namely Thermoanaerobacter italicus sp. nov. Received: May 25, 1997 / Accepted: June 5, 1997     

Succession in zooplankton and hydrophytes of a seasonal water on the west coast of South Africa

Paramesochra mielkei sp.n. is described and figured from the interstices of subtidal sandy sediments off the SW Dutch coast. Kunz' (1981) phylogenetic scheme of the Paramesochridae Lang, 1948 is re-examined and it is suggested that the family comprises two phyletic lines which originated early in paramesochrid evolution. Translation into Linnean hierarchies implies the establishment of two new sub-families. Within the primitive Diarthrodellinae subfam. n., Tisbisoma Bozic, 1964 is ancestral to Diarthrodella Klie, 1949 s.l. and Rossopsyllus Soyer, 1975. Remanea Klie, 1929 is transferred to the Paramesochrinae subfam. n. which comprises the genera of both the Scottopsyllus- and the Paramesochra-group. The aberrant genus Caligopsyllus Kunz, 1975, standing close to Apodopsyllus, is removed from the Paramesochra-group. P. brevifurca Galhano, 1970 is splitted into two subspecies and replaced in the genus Paramesochra. An attempt is made to assess the phyletic interrelationships of the Paramesochra-species and the resulting cladogram splits the genus into four species-groups. P. mielkei sp.n. is referred to the dubia-group and seems to be closely related to P. borealis Geddes, 1981. Finally, an amended diagnosis and a revised key to the species of the genus Paramesochra are presented.     

厦门地区鸭鹅绦虫生活史研究

本文报告了福建厦门地区寄生于鸭鹅类的膜壳科绦虫计5属9种。实验阐明了5种绦虫的生活史,其中有三种生活史为我国首次报告。厦门地区有5种嵌水甲壳类可作膜壳绦虫的中间宿主。其中短角异剑水蚤(Apocyclops royi)是矛形剑带绦虫和片形皱缘绦虫的审间宿主,不等异介虫(Heterocypris anomala)为新发现的棘盘双睾绦虫的中间宿主,介虫(Cyprinotus sp.)为新发现的美丽膜壳绦虫的中间宿主。     

Anaerobic degradation of phenol by pure cultures of newly isolated denitrifying pseudomonads

From various oxic or anoxic habitats several strains of bacteria were isolated which in the absence of molecular oxygen oxidized phenol to CO₂ with nitrate as the terminal electron acceptor. All strains grew in defined mineral salts medium; two of them were further characterized. The bacteria were facultatively anaerobic Gramnegative rods; metabolism was strictly oxidative with molecular oxygen, nitrate, or nitrite as electron acceptor. The isolates were tentatively identified as pseudomonads. Besides phenol many other benzene derivatives like cresols or aromatic acids were anaerobically oxidized in the presence of nitrate. While benzoate or 4-hydroxybenzoate was degraded both anaerobically and aerobically, phenol was oxidized under anaerobic conditions only. Reduced alicyclic compounds were not degraded. Preliminary evidence is presented that the first reaction in anaerobic phenol oxidation is phenol carboxylation to 4-hydroxybenzoate.     

Growth of Nitrobacter by dissimilatoric nitrate reduction

Abstract Eight strains of the genus Nitrobacter grew under anaerobic conditions in the presence of nitrate. The growth was inhibited by nitrate concentrations above 0.5 mM. By a special culture technique inhibition caused by nitrite was abolished. Nitrate oxidizing cells grew in gas tight culture flasks as a biofilm on a gas-permeable silicone tubing. The biofilm allowed nitrate-reducing cells to grow at a low nitrite concentration. These cells grew either actively motile in the anaerobic medium, or in anaerobic zones of the biofilm. They produced nitrite and ammonia. Nitrogen balance calculations established a loss of inorganic nitrogen for 5 of 8 strains. This implies that nitrate-reducing cells produced furthermore volatile nitrogen compounds. N₂O was detected by gas chromatography.     

Tomato resistance to Alternaria stem canker: localization in host genotypes and functional expression compared to non-host resistance

Summary The Alternaria stem canker resistance locus (Asc-locus), involved in resistance to the fungal pathogen Alternaria alternata f. sp. lycopersici and in insensitivity to host-specific toxins (AAL-toxins) produced by the pathogen, was genetically mapped on the tomato genome. Susceptibility and resistance were assayed by testing a segregating F₂ population for sensitivity to AAL-toxins in leaf bioassays. Linkage was observed to phenotypic markers solanifolium and sunny, both on chromosome 3. For the Asc-locus, a distance of 18 centiMorgan to solanifolium was calculated, corresponding to position 93 on chromosome 3. This map position of the resistance locus turned out to be the same in three different resistant tomato accessions, one Dutch and two American, that are at least 40 years apart. AAL-toxin sensitivity in susceptible and resistant tomato genotypes was compared with AAL-toxin sensitivity in a non-host Nicotiana tabacum during different levels of plant cell development. In susceptible and resistant tomato genotypes, inhibitory effects were demonstrated at all levels, except for leaves of resistant genotypes. However, during pollen and root development, inhibitory effects on susceptible genotypes were larger than on resistant genotypes. In the non-host Nicotiana tabacum, hardly any effects of AAL-toxins were demonstrated. Apparently, a cellular target site is present in tomato, but not in Nicotiana tabacum. It was concluded that three levels of AAL-toxin sensitivity exist: (1) a susceptible host sensitivity, (2) a resistant host sensitivity, (3) a non-host sensitivity, and that the resistance mechanism operating in tomato is different from that operating in Nicotiana tabacum.