TWO TYPES OF CYTOPLASMIC CLEAVAGE IN THE COENOCYTIC SOIL ALGA PROTOSIPHON BOTRYOIDES (CHLOROPHYCEAE)1

Cytokinesis in the coenocytic green alga Protosiphon botryoides (Kütz.) Klebs was studied with transmission electron microscopy. In vegetative cells, nuclei with associated basal bodies and dictyosomes are scattered throughout the cytoplasm. Mature cells may develop either multinucleate resting spores (coenocysts) or uninucleate zoospores. Cytokinesis may be preceded by contraction of the protoplast due to the disintegration of vacuoles that are present in larger, siphonous cells. The formation of coenocysts in ageing, siphonous cells, is signalled by cleavage of the chloroplast and the development of arrays of phycoplast microtubules in one or more transversely oriented planes through the cell. Nuclei with associated basal apparatuses stay dispersed throughout the cytoplasm; the basal bodies apparently are not involved in organization of the phycoplast. The plasma membrane invaginates, resulting in a centripetal cleavage of the protoplast into two or more multinucleate daughter protoplasts. Simultaneously, wall material is deposited along the outside of the daughter protoplasts by dictyosome-derived vesicles, and finally two or more thick-walled coenocysts are formed. The formation of zoospores, on the other hand, is signalled by clustering of the nuclei in one or more groups depending on the shape of the mother cell. The nuclei become arranged with the associated basal apparatuses facing toward the center of the cluster. Bundles of phycoplast microtubules develop between the nuclei, radiating from the center of a cluster toward the plasma membrane; basal apparatuses or associated structures apparently are involved in organization of the phycoplast. Cleavage furrows grow out centrifugally along these bundles of micro-tubules, fed by dictyosome-derived vesicles. No wall material is deposited. An additional mitotic division occurs during cleavage, and finally numerous uninucleate, wall-less, biflagellate zoospores are formed. The ultrastructural features of the two different types of cytoplasmic cleavage associated with two different types of daughter cells have not previously been reported for chlorophycean algae.     

Use of Brassica callus culture to induce sporulation in Alternaria brassicae (Berk.) Sacc.

A non-sporulating isolate of Alternaria brassicae, inoculated on callus culture of Brassica juncea cv. Kranti, colonized the callus and produced spores. When captafol, a fungicide, was added (100 mg/l) to the callus culture medium, if effectively checked fungal contamination and saprophytic growth of A. brassicae on culture medium, without adversely affecting callus growth or establishment of dual culture.     

Isolation and characterization of an anaerobic benzoate-degrading spore-forming sulfate-reducing bacterium, Desulfotomaculum sapomandens sp. nov.

Abstract Spore-forming sulfate-reducing bacteria (SRB) were enriched selectively from various kinds of aerobic soils with fatty acids as the sole carbon and energy source. A Gram-negative motile rod-shaped bacterium, which produced gas vacuoles during sporulation was isolated. It degraded alcohols, aromatic and n-fatty acids (up to C₁₈) except for propionate, completely to CO₂. Sulfate, sulfite, thiosulfate or elemental sulfur served as electron acceptors. Because of its sensitivity to H₂S, the isolate never produced more than 8 mM dissolved sulfide at pH 7.0. G + C-content of the DNA was 48.0 mol %. The isolated strain Pato is described as a new species Desulfotomaculum sapomandens .     

诱导茄链格孢菌分生孢子形成的新技术

本文报道诱导茄链格孢菌(Alternaria solani)分生孢子形成的一种新技术。生长在马铃薯-葡萄糖-琼脂(PDA)上两天的茄链格孢菌琼脂块移接到玉米培养基上,置于日光灯下照射,诱发分生孢子梗生长。然后,再放在18℃下黑暗培养。12小时后,在菌丝块表面有大量的分生孢子形成。成熟的茄链格孢菌分生孢子用蒸馏水洗脱。     

Netropsin stimulates the formation of an extracellular proteinase and suppresses protein turnover in sporulating Bacillus megaterium

Abstract Netropsin stimulated the rate of synthesis of an extracellular metalloproteinase in Bacillus megaterium incubated in a sporulation medium. The antibiotic delayed but did not suppress the decrease in the ability to synthesize the proteinase occurring at later sporulation stages. Netropsin also stimulated the synthesis of the proteinase when added to a growing culture; it inhibited the increase of protein turnover which was switched on between the 2nd and 3rd hour in the sporulating population. No refractile spores were developed during 6 h at 35°C in the antibiotic-treated culture. In the control 60% of sporulating cells were observed under similar conditions.     

Syntheses and biological activities of azido ubiquinone derivatives

A general method for the synthesis of azido-ubiquinone derivatives has been developed directly by substituting one hydrogen atom on the benzoquinone ring with an azido group under weakly acidic conditions. The reaction takes several hours and the yield is generally low. The azido-ubiquinone was purified by preparative thin layer chromatography, and identified by NMR, IR and mass spectra. All the synthesized azido-ubiquinone derivatives show partial activity in mediating biological electron transfer in the dark, and show partial or complete inhibition upon photolysis.     

Sporulation: an alternative way to recover recombinant proteins from Bacillus subtilis

A recombinant strain of Bacillus subtilis engineered for endocellular expression of human interleukin-1 receptor antagonist (IL-Ira) was subjected to sporulation. The recombinant protein was recovered from the sporulation supernatant in quantities, purity, and activity comparable with those obtained from a traditional cell lysate. Thus, exploitation of this natural mechanism of autolysis could overcome problems of intact protein recovery related to the cell disruption step. (c) 1995 John Wiley & Sons, Inc.     

P-factor,a developmental hormone of Penicillium cyclopium?

From the mycelium of Penicillium cyclopium a biologically active fraction (P-factor) was isolated, which increases conidiation and the formation of the benzodiazepine alkaloids cyclopenin and cyclopenol. Its activity was determined by measuring the increase of alkaloid formation in strain SM 72. On a preparative scale P-factor preparations were obtained from fermenter-grown hyphae of mutant dev 63 by extraction with water at 120°. P-factor is strongly hydrophilic but it is not a protein. It was active if added during conidiospore germination and early growth phase, causing an acceleration of protein biosynthesis. The action on alkaloid biosynthesis and sporulation is indirect and resembles that of a developmental hormone.