Biofilm formation by haloarchaea

A fluorescence‐based live‐cell adhesion assay was used to examine biofilm formation by 20 different haloarchaea, including species of Halobacterium, Haloferax and Halorubrum, as well as novel natural isolates from an Antarctic salt lake. Thirteen of the 20 tested strains significantly adhered (P‐value < 0.05) to a plastic surface. Examination of adherent cell layers on glass surfaces by differential interference contrast, fluorescence and confocal microscopy showed two types of biofilm structures. Carpet‐like, multi‐layered biofilms containing micro‐ and macrocolonies (up to 50 μm in height) were formed by strains of Halobacterium salinarum and the Antarctic isolate t‐ADL strain DL24. The second type of biofilm, characterized by large aggregates of cells adhering to surfaces, was formed by Haloferax volcanii DSM 3757^T and Halorubrum lacusprofundi DL28. Staining of the biofilms formed by the strongly adhesive haloarchaeal strains revealed the presence of extracellular polymers, such as eDNA and glycoconjugates, substances previously shown to stabilize bacterial biofilms. For Hbt. salinarum DSM 3754^T and Hfx. volcanii DSM 3757^T, cells adhered within 1 day of culture and remained viable for at least 2 months in mature biofilms. Adherent cells of Hbt. salinarum DSM 3754^T showed several types of cellular appendages that could be involved in the initial attachment. Our results show that biofilm formation occurs in a surprisingly wide variety of haloarchaeal species.     

Minicell formation by Campylobacter jejuni

Campylobacter jejuni sheds its flagella and varying proportions of the poles of the cell late in the growth cycle, resulting in the production of very small flagellated structures 0.1 to 0.3 microM in diameter. Electron microscopy revealed that these structures were minicells possessing outer membrane, cytoplasmic membrane, flagellar basal complex, and polar membrane; nucleoplasms were not seen. The initial event in the formation of these minicells involved a constriction of the cytoplasmic membrane, segregating the polar regions of the cell. The peptidoglycan layer of the cell wall was not visible, but was presumed to lyse at the separation site of minicell formation, and to reform or remain intact along the main length of the cell because the rods did not spheroplast. Finally, rupture and resealing of the outer membrane component of the wall resulted in the release of fully enclosed minicells and nonflagellated rods.     

Rosette formation by human thymocytes

A proportion of lymphocytes in human fetal and post-natal thymus, and in blood, formed rosettes with red blood cells from sheep and pig. The count of rosette-forming cells (RFC) among human thymocytes varied widely, from 2–216 per thousand cells, and was higher in fetal than in post-natal life. The count of RFC among human thymocytes was not reduced by specific rabbit anti-human immunoglobulin sera, indicating that the receptor was not of immunoglobulin character; the reaction was inhibited by antithymocyte serum and metabolic poisons and certain enzymes. The receptor may be equivalent to other “non-specific” glycoprotein hemagglutinins in plants and viruses.The importance of species differences in immunological assays is emphasized. Thus human thymocytes gave high counts of RFC only with red blood cells of sheep and pig; moreover thymus lymphocytes from only man and pig, but not several other species including rodents, were highly reactive with sheep red blood cells. The capacity for rosette formation could be a marker for T cells in human blood.     

Ethanol formation by hybrid yeasts

Summary Fusion products between Saccharomyces cerevisiae and Saccharomyces mellis were examined for their fermentative capacity. While there was little difference in the fermentation rate between S. cerevisiae (industrial strain) and the hybrids at low sugar concentrations (4% glucose), at 35% the hybrid strains were far superior (13.6% w.w. vs. 9.0% w.w.). Data on the accumulation of intracellular ethanol seem to indicate that the high fermentation efficiency of the hybrid strains may be due, in addition to their osmotolerance, also to their improved ability to excrete ethanol from their cells.     

Pseudopodia formation by neurosecretory granules

Summary Ultrastructural studies of the mouse neurohypophysis, under various experimental conditions, revealed a number of neurosecretory granules (NSG) bearing single pseudopodia-like protrusions. Some NSG adhered to the axolemma via pseudopodia; other NSG, distant from the axolemma, budded electron lucent microvesicles from the tip of the pseudopod.Pseudopodia counts were made on electron micrographs, and calculated as a percentage of the NSG population. In neural lobes from intact mice, small numbers of pseudopodia were observed (0.3%); the count increased significantly after injections of large doses of horseradish peroxidase (HRP) (9.4–14.5%); hypertonic saline augmented the count, as did histamine.In vitro incubation experiments with isolated neural lobes in Krebs Ringer revealed concomitant pseudopodia formation and elevated vasopressin release (measured by antidiuretic bioassay) in the presence of HRP and di-butyryl cyclic AMP respectively. Histamine and excess potassium also increased hormone secretion, but did not induce pseudopodia formation in vitro; pseudopodia were observed neither in controls, nor in the presence of ineffective secretagogues.It is suggested that the pseudopod may represent the active site on the granule membrane. Different ultrastructural images of granule release suggest that several modes of hormone release may be operative in the neurohypophysis. The role of HRP in pseudopodia formation and vasopressin release is enigmatic.This study is dedicated to Prof. Berta Scharrer, esteemed mentor and beloved friendProf. Zwi Selinger, Department of Biological Chemistry of the Hebrew University, kindly collaborated in the in vitro experiments. Thanks are due to Mrs. Ilana Sabnai and Mrs. Sara Eimerl for excellent technical assistance. Research supported by the Binational Israel-United States Science Foundation (BNSF), grant 200     

Ketogluconate formation by Gluconobacter species

Summary When G. oxydans ATCC 621-H was grown in batch culture in a complex medium with glucose, ketogluconates were produced when the pH in the culture was maintained at 5.5. Without pH control gluconate was the only product of glucose oxidation, but at pH 5.5 the gluconate so produced was further oxidized to ketogluconates. Production of ketogluconates started when glucose was almost completely exhausted. It was shown that the actual glucose and gluconate concentrations in the culture do not determine the onset of ketogluconate formation during growth. Both 2 and 5 ketogluconate were produced. Addition of CaCO₃ to the medium favored the production of 5 ketogluconate. However, under these conditions minor quantities of 2 ketogluconate were also formed. The sequential production of gluconate and ketogluconates from glucose was not only restricted to G. oxydans ATCC 621-H. A number of G. oxydans strains when grown under standard conditions in a pH controlled batch culture, all produced ketogluconates from glucose via an intermediate accumulation of gluconate. Although the ratios of the ketogluconates produced varied from strain to strain, all strains produced both 2 and 5 ketogluconate.     

Sulfite formation by wine yeasts

Four strains of wine yeasts of two different species (Saccharomyces cerevisiae var. ellipsoideus and S. bayanus) were investigated with respect to regulation of NADPH- and benzyl viologen-dependent sulfite reductases by various sulfur sources. The enzyme activity was followed over a growth period of 96 h. The low sulfite-producing strains showed an increased biosynthesis of NADPH-dependent sulfite reductase during the exponential growth phase in the presence of sulfate, sulfite and djencolic-acid. This increase was not observed in the high sulfite-producing strains. Methionine and cysteine prevented this derepression. At the end of the exponential growth phase, enzyme biosynthesis was repressed again, presumably by sulfur-containing amino acids which were produced during growth. The regulatory influence of the various sulfur sources on benzyl viologen dependent sulfitereductase activity is obviously much weaker.Abbreviation BV benzyl viologen     

Amyloid formation by salmon calcitonin

It is demonstrated using three independent methods that salmon calcitonin can form amyloid fibrils in vitro. Large aggregates are shown to exhibit a blue-green birefringence in cross polarised light after staining with congo red. Individual fibrils were observed using electron microscopy. These fibrils are approx. 50–60 Å in diameter and up to 20 000 Å in length and are similar in appearance to those observed in Alzheimer's disease. Finally, X-ray diffraction studies of the large aggregates reveal the cross-β conformation characteristic of the monomers in the fibre.     

Cellulase formation by Aspergillus nidulans

The optimum pH, temperature and concentration of the substrate, carboxymethyl-cellulose (CMC), for the production of cellulases by Aspergillus nidulans were found to be 3.05, 37°C and 1%, respectively. When grown on CMC under optimum conditions, it produced the three components of the cellulase complex, exo-β-1,4-glucanase, endo-β-1,4-glucanase and β-1,4-glucosidase, both in cell free as well as cell-associated states. The enzyme yields in shake cultures were lower than those obtained during stationary cultivation. Among the defined substrates, lactose emerged as the best inducer for exo-glucanase and endo-glucanase, while β-glucosidase was best induced by pectin. Endo-glucanase production increased significantly when A. nidulans was grown on insoluble delignified lognocellulosic substrates, with the maximum being on paddy straw.It appears that the synthesis of individual components of the cellulase system of A. nidulans may not be regulated in a strictly coordinated manner.     

Ion channel formation by zervamicin-IIB

Zervamicin-IIB (Zrv-IIB) is a 16 residue peptaibol which forms voltage-activated, multiple conductance level channels in planar lipid bilayers. A molecular model of Zrv-IIB channels is presented. The structure of monomerc Zrv-II3 is based upon the crystal structure of Zervamicin-Leu. The helical backbone is kinked by a hydroxyproline residue at position 10. Zrv-IIB channels are modelled as helix bundles of from 4 to 8 parallel helices surrounding a central pore. The monomers are packed with their C-terminal helical segments in close contact, and the bundles are stabilized by hydrogen bonds between glutamine 11 and hydroxyproline 10 of adjacent helices. Interaction energy profiles for movement of three different probes species (K⁺, Cl^– and water) through the central pore are analyzed. The conformations of: (a) the sidechain of glutamine 3; (b) the hydroxyl group of hydroxyproline 10; and (c) the C-terminal hydroxyl group are optimized in order to maximize favourable interactions between the channel and the probes, resulting in favourable interaction energy profiles for all three. This suggests that conformational flexibility of polar sidechains enables the channel lining to mimic an aqueous environment.     

Sulfite formation by wine yeasts

Five different strains of wine yeasts were investigated with respect to active uptake of [³⁵S] sulfate and its regulation by methionine. Considerable differences exist between low and high sulfite-producing strains in the initial velocity of sulfate uptake. Further differences were established in repression of sulfate permease by l-methionine, most evident in a total lack of repression in one of the high sulfite producers. These findings explain in part variable sulfite and sulfide formation.List of Abbreviations CCMP carbonylcyanide-p-trifluormethoxyphenylhydrazone