Selection and Study of Potent Lactose-Fermenting Yeasts

Whey-fermenting Kluyveromyces cultures were revealed among 105 yeast strains assimilating lactose. Eighteen strains from milk products, showing maximum potency, fermented galactose, sucrose, and raffinose, in addition to lactose. Many yeast strains fermented inulin. Most strains were resistant to cycloheximide and grew in medium containing glucose, NaCl, and ethanol at concentrations of up to 50, 11–12, and 10–12%, respectively (4°C). Three strains had mycocinogenic activity. After fermentation of whey with selected yeast strains at 30°C for 2–3 days, the ethanol concentration was 4–5%.     

Screening of yeasts for the production of the aroma compound 2-phenylethanol in a molasses-based medium

Fourteen yeast strains were screened for production of 2-phenylethanol from l-phenylalanine with molasses as carbon source. Up to 1 g 2-phenylethanol l^–1 was obtained. Using oleyl alcohol as a second phase for in situ product removal to enhance the production of 2-phenylethanol increased the yield to about 3 g 2-phenylethanol l^–1 at 35 °C. The most productive strains were Kluyveromyces marxianus CBS 600 and CBS 397.     

SelectingRhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya: Tolerance of high temperature and antibiotic resistance

Forty one strains ofRhizobium phaseoli were screened for the ability to multiply at high temperatures on yeast extract-mannitol agar. Most strains were tolerant of 30°C, eight strains were tolerant of 45°C and two of 47°C although the rate of multiplication was reduced at 45–47°C. The high temperature-tolerant strains were isolated from Kenyan soils and were fast-growing. Seven of the eight strains tolerant of 45–47°C lost their infectiveness after incubation at high temperature but four strains tolerant of 40°C remained infective after incubation at that temperature.Thirty six strains were resistant to 200 g ml^–1 streptomycin sulphate and 29 strains to 200 g ml^–1 spectinomycin dihydrochloride. Eight strains were resistant to both antibiotics each at 200 g ml^–1. Two of the double-labelled antibiotic-resistant mutants lost their infectiveness onPhaseolus vulgaris. The response to acidity was unaltered and two of the mutants showed a decrease in temperature tolerance. The doublelabelled mutants were recoverable from two Kenyan soils.     

Isolation and improvement of a thermotolerant Saccharomyces cerevisiae strain

The ambient temperature is a drawback in industrial ethanol production in Jaffna due to heat killing of yeast during fermentation. Thus a search was initiated for thermotolerant organisms suitable for fermentation in hot climates. The screening of the best wild-type organisms was undertaken as the first step. Thermotolerant strains were selected from environments where there are chances of organisms being exposed to high temperature. The samples were enriched and screened for thermotolerant organisms which survived at 45 °C for 15 h. Among the yeast strains selected from different sources, thermotolerant strains with the capacity to withstand 45 °C for 15 h were found in samples collected from the compost heap and distillery environments. Three colonies from the distillery environment were selected for further studies and named p1, p2 and p3. Exponential phase (18 h) cultures of p1, p2 and p3 were subjected to 15 temperature treatment cycles (at 50 °C each for 3 h) and thermally adapted strains pt1, pt2 and pt3 were obtained, showing 100, 30 and 20% viability at 50 °C for 30 min respectively. The initial round of thermal adaptation cycles increased the duration of 100% viability from 20 h (p1) to 68 h (pt1) when incubated at 40 °C. Very little benefit was obtained when pt1 was treated with u.v. and ethyl methanesulphonate. The selected strain was identified and designated as Saccharomyces cerevisiae S1. The ethanol produced from 100 g glucose l^–1 by S. cerevisiae S1 was 46 g l^–1 (36 h), 38 g l^–1 (48 h) and 26 g l^–1 (48 h) at 40, 43 and 45 °C respectively in rich nutrient medium.     

Kinematographische Untersuchungen über die Wirkung von IES und Cumarin auf das Wachstum von grünen und etiolierten Weizenkoleoptilsegmenten

Zusammenfassung Das Streckungswachstum grüner und etiolierter Weizenkoleoptilsegmente wurde kinematographisch erfaßt. Das Eigenwachstum, das nach Regeneration der physiologischen Spitze einsetzt, tritt an grünen Koleoptilsegmenten später auf als an etiolierten Segmenten und vollzieht sich bei den ersteren ungeachtet einer eventuell vorausgegangenen IES-bedingten Streckung.IES-Gaben lösensofort nach der Dekapitation ein Wachstum aus. Durch steigende IES-Konzentration wird nicht nur eine steigende Wachstumsgeschwindigkeit hervorgerufen, sondern auch die zeitliche Dauer der ausgelösten Streckung verlägert. Dadurch ergibt sich für jede der getesteten IES-Konzentrationen eine charakteristische Wachstumsgeschwindigkeitskurve, die in ihrem Verlauf mehr oder weniger regelmäßige Schwankungen aufweist.Cumarinlösungen von 10^–6 lassen die normalerweise spät einsetzende erhöhte Wachstumsgeschwindigkeit früher auftreten, Lösungen von 10^–5 und 10^–4 sogar gleich nach der Dekapitation der Testpflanzen.Mit 12 Textabbildungen     

Einflu\ von Diffusionspotentialen auf Membranpotential- und IonenaktivitÄtsmessungen in biologischen Systemen am Beispiel von KCl-Rinderserumalbumin-Lösungen

Zusammenfassung Membranpotentiale und IonenaktivitÄten lassen sich aus EMK-Messungen nur dann nÄherungsweise bestimmen, wenn die Diffusionspotentiale an den beiden Salzbrücken nÄherungsweise berechnet werden können. Unter Benutzung der von Möller, van Os und Overbeek [Trans. Farad. Soc.57, 312 (1961)] gemessenen und durch die Anwesenheit des Rinderserumalbumins (RSA) verÄnderten elektrischen Beweglichkeit von K⁺- und Cl^–-Ionen in RSA-KCl-Lösungen verschiedener Konzentration wurden die überführungszahlen und derideale Anteil des Diffusionspotentials in einer Diffusionsschicht vom Henderson-Typ zwischen verschiedenen RSA-KCl-Lösungen und einer gesÄttigten KCl-Lösung berechnet. Bei dieser, an einer Rechenanlage durchgeführten Rechnung wurde die AktivitÄt der Komponenten durch deren Konzentration ersetzt. Au\erdem wurde der Einflu\ eines vom Wert in einer reinen Salzlösung gleicher Konzentration abweichenden AktivitÄtskoeffizienten für K⁺- und Cl^–-Ionen berechnet, wobei für den AktivitÄtskoeffizienten des Gegenions Werte zwischen 0,2 und 0,7 angenommen wurden. Die Rechnung ergab, da\ bei Anwesenheit des RSA-Moleküls mit einer Ladungszahl von — 22 in der Diffusionsschicht und bei Berücksichtigung der verschiedenen Kombinationen von Coionen- und GegenionenaktivitÄtskoeffizienten das Diffusionspotential einen Wert zwischen + 10 mV und – 10 mV annehmen kann.

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Liquid junction potential, membran potential, and ion activity in bovine serum albumin solutions and biological systems

Summary The determination of membrane potentials and single ion activities — although without strict thermodynamic basis — from e.m.f. measurement to a reasonable approximation presupposes an evaluation of the liquid junction potentials (l.j.p.) at the two salt bridges to the same degree of accuracy.Using the data for the electrical mobility of K⁺- and Cl^–-ions in bovine serum albumin solutions of differing compositions obtained by Möller, van Os, and Overbeek the transport numbers of K⁺ and Cl^– in these polyelectrolyte solutions and theideal part of the liquid junction potential were computed assuming a Henderson-type boundary and replacing activities by concentrations. The contribution of the terms containing various combinations of the activity coefficients for the colons between 0.5 and 0.9 and counter ions between 0.2 and 0.7 to the l.j.p. is of the same order of magnitude as theideal part of the l.j.p. containing the concentration and transport numbers alone. Taking the activity coefficients into account, the l.j.p. may reverse its sign. Practically all values for the l.j.p. are localized in the range between +10 mV and –10 mV.A crude approximation of the l.j.p. at the tip of a salt bridge located in the cytoplasm of a cell shows that even in this case the l.j.p. presumably has similar values.

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Herrn Professor Boris Rajewsky zum 75. Geburtstag gewidmet.     

Study of physicochemical factors limiting the growth ofKluyveromyces marxianus

Summary The effects of various physicochemical parameters on the growth of twoKluyveromyces marxianus strains were investigated, including: pH values, sodium chloride, water activity in the medium and temperature. Both yeast strains were unaffected by pH changes. Optimal pH for growth was found to be 4 with both strains, but they were able to develop within the pH 3–8 range. Suitable growth was obtained at temperatures of 4–44°C and the optimal temperature for growth was 36°C for both strains. Modelling of this latter parameter is described. Growth of both microorganisms was considerably modified by increased NaCl or decreased water activity in the medium.     

Nitrate reductase from yeast: cultivation,partial purification and characterization

Summary Several yeast strains were assayed for occurence of nitrate reductase after growth in a defined medium with nitrate as the sole nitrogen source, Candida boidinii DSM 70026, showing the highest specific activity, was further investigated. The procedures for yeast fermentation and nitrate reductase purfication are described in detail. Nitrate reductase from this yeast was characterized as NAD(P)H: nitrate oxidoreductase (E.C.1.6.6.2). The enzyme activity with NADH (NADPH) was highest at pH 7.0 (7.1) and 30° C (25° C). The values of K _m determinations with NADH/NADPH were both 4 × 10^–4 mol/l; values for the substrate inhibition constant (K _i) were 6 × 10^–4 mol/l. The molecular mass of the native enzyme was estimated by gel permeation chromatography to be approximately 350 kDa. Offprint requests to: R. Gromes     

Die Erzeugung von Chemilumineszenzen wÄ\riger TlI-Salzlösungen durch Röntgenstrahlen

Zusammenfassung Die Lumineszenz wÄ\riger Tl⁺-Lösungen unter Einwirkung von 8,5-keV_eff-Röntgenstrahlen wird untersucht, und zwar 1. in neutraler Lösung, 2. in saurer Lösung, 3. in alkalischer Lösung, 4. bei Zusatz von NaCl.Bei Änderung des pH-Wertes nimmt die Lichtausbeute sowohl auf der sauren Scite (beipH=3,4) als auch auf der alkalischen Scite (beipH=12) ein Maximum an; sie erreicht dort den 2- bis 3fachen Wert der Ausbeute in neutraler Lösung. Andererseits ist bei Zusatz von 1 M NaCl in neutraler Lösung die Ausbeute fünfmal höher als bei Abwesenheit von NaCl; die Maxima im sauren und alkalischen Bereich verschwinden jedoch bei 1 M NaCl vollkommen, und man erhÄlt bei gro\en und bei kleinen pH-Werten lediglich eine Löschung der Lumineszenz.Die Lumineszenz kommt durch Bildung von Tl^+* bei der Anlagerung von e_aq an Tl⁺⁺ zustande. Tl⁺⁺ entsteht jedoch nicht unmittelbar gemÄ\ Tl⁺ + OH Tl⁺⁺ + OH^–, sondern zunÄchst bildet sich Tl⁺OH, und dieses dissoziiert erst nach einer Verzögerung von > 10^–7 sec in Tl⁺⁺ und OH^–. Die Sensibilisierung durch H⁺ wird durch die Reaktion Tl⁺OH + H⁺ Tl⁺⁺ + H₂O und die durch OH^– durch Tl⁺OH + OH^– Tl⁺⁺O^– + H₂O erklÄrt. Die Reaktion der Komplexe Tl⁺Cl^– und Tl⁺Cl₂ ^– mit OH erfolgt offenbar ohne zeitliche Verzögerung, d. h. Tl⁺⁺Cl^–– bzw. Tl⁺⁺Cl₂ ^–– wird dabei innerhalb einer Zeit 10^–7 sec gebildet.

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Chemiluminescences of aqueous Tl^I solutions produced by irradiation with 8.5-keV-X-rays

Summary The luminescence of aqueous solutions of Tl⁺ during irradiation with 8.5-keV-X-rays has been investigated. In particular we have studied the Tl⁺-luminescence in 1. neutral solutions, 2. acid solutions, 3. alkaline solutions, 4. solutions containing various concentrations of NaCl.Varying thepH the luminescence yield passes a maximum on the acid side as well as on the alkaline side (atpH=3.4 respectivelypH=12). Compared with neutral solutions the luminescence yield is increased by a factor 2 to 3 at these pH-values.By adding 1 M NaCl to neutral Tl⁺-solutions the luminescence yield is enhanced by a factor five, however in dependence ofpH no further increase has been observed, but only quenching of the luminescence at low and highpH.The luminescence origins from the formation of Tl^+* by the reaction of e_aq with Tl⁺⁺ formed by oxidation of Tl⁺ by OH. However, Tl⁺⁺ is not formed directly by Tl⁺+OH Tl⁺⁺ + OH^– but via dissociation of the intermediate Tl+OH after a delay > 10^–7 sec.We explain the increase of the luminescence yield in acid solutions by the reaction Tl⁺OH + H⁺ Tl⁺⁺ + H₂O and in alkaline solutions by the reaction Tl⁺OH + OH^– Tl⁺⁺O^– + H₂O. In alkaline solutions the luminescence spectrum shifts to longer wavelengths; we conclude, that this spectrum is attributed to Tl^+*O^–. Evidently the reaction of Tl+Cl^– and Tl+Cl₂ ^–– with OH leads to formation of Tl⁺⁺Cl^– and Tl⁺⁺Cl₂ ^–– without any efficient delay.

     

Biosurfactant from <Emphasis Type="Italic">Lactococcus lactis</Emphasis> 53 inhibits microbial adhesion on silicone rubber

The ability of biosurfactant obtained from the probiotic bacterium Lactococcus lactis 53 to inhibit adhesion of four bacterial and two yeast strains isolated from explanted voice prostheses to silicone rubber with and without an adsorbed biosurfactant layer was investigated in a parallel-plate flow chamber. The microbial cell surfaces and the silicone rubber with and without an adsorbed biosurfactant layer were characterized using contact-angle measurements. Water contact angles indicated that the silicone-rubber surface with adsorbed biosurfactant was more hydrophilic (48°) than bare silicone rubber (109°). The results showed that the biosurfactant was effective in decreasing the initial deposition rates of Staphylococcus epidermidis GB 9/6 from 2,100 to 220 microorganisms cm^–2 s^–1, Streptococcus salivarius GB 24/9 from 1,560 to 137 microorganisms cm^–2 s^–1, and Staphylococcus aureus GB 2/1 from 1,255 to 135 microorganisms cm^–2 s^–1, allowing for a 90% reduction of the deposition rates. The deposition rates of Rothia dentocariosa GBJ 52/2B, Candida albicans GBJ 13/4A, and Candida tropicalis GB 9/9 were far less reduced in the presence of the biosurfactant as compared with the other strains. This study constitutes a step ahead in developing strategies to prevent microbial colonization of silicone-rubber voice prostheses.     

Quantitative Beziehungen zwischen Temperaturreiz und Aktionspotentialen der Lorenzinischen Ampullen

Zusammenfassung Es wurden die Aktionspotentiale der afferenten Nervenfasern aus den Lorenzinischen Ampullen des Katzenhaies (Scylliam) untersucht, während an den Ampullen definierte und thermoelektrisch registrierte Temperaturreize gesetzt wurden. Versuche in situ und an isolierten Präparationen ergaben keinen Unterschied. Die Entladung der Ampullen erwies sich als unempfindlich gegen mechanische Reize, dagegen äußerst empfindlich gegen thermische Einwirkung. Temperaturregistrierungen in den Ampullen zeigten, daß bei thermischen Reizen an der unverletzten Haut starke Temperaturänderungen il den Ampullen ablaufen.Bei konstanter Temperatur zeigt die Einzelfaser eine Dauerentladung, deren Frequenz zwischen 15 und 23° ein Maximum bis zu 65 Impulsen · sec^–1 hat und nach den wärmeren und kälteren Temperaturen stetig bis zum Nullwert abfällt; die äußersten Grenzen sind 2 und 34°. Das Frequenzmaximum des Gesamtnerven liegt bei etwa 20°. Die höchste statische Unterschiedsempfindlichkeit der Einzelfaser erreicht im Bereich des positiven Temperaturkoeffizienten +7 Imp · s^–1 · grad^–1, im Bereich des negativen — 20 Imp · s^–1 · grad^–1. Kältesprünge führen im gesamten Aktionsbereich der Einzelfaser zu einer vorübergehenden Frequenzerhöhung bis 180 sec^–1 mit anschließender Adaptation auf einen niedrigeren Dauerwert; die überschießende Frequenzerhöhung hängt dabei neben der Temperatur vor allem auch von deren Änderungsgesehwindigkeit d/dt ab. Die dynamische Unterschiedsempfindlichkeit erreicht dabei bis—90 Imp·s^–1 · grad^–1, wobei der Receptor auch außerhalb des statischen Aktionsbereiches noch dynamisch erregbar ist. — Bei Wärmesprüngen verhält sich die Entladung genau spiegelbildlich zur Abkühlung; nach vorübergehender partieller oder völliger Hemmung der Entladung stellt sie sich wieder auf einen Dauerwert ein.Isolierte Einzelampullen zeigen dieselben Erregungsgesetze, nur gehen hier die Spikes bei Abkühlung in regelmäßige Wellen über, die schwebungsartig moduliert sind und vermutlich durch Synchronisation von Fasern innerhalb der Ampulle zustande kommen.Das Verhalten der Lorenzinischen Ampullen entspricht qualitativ in allen Punkten dem der Kältereceptoren der Warmblüter; quantitativ sind die Ampullen noch etwas empfindlicher.Die Versuche wurden mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt. Den Kollegen an der Zoologischen Station Neapel, insbesondere Herrn Prof. Dr. Reinhard Dohrn, möchte ich an dieser Stelle meinen aufrichtigen Dank für ihre freundliche Hilfe zum Ausdruck bringen.     

Thermotolerant single cell protein production byKluyveromyces marxianus var.marxianus

Summary Amino acid analyses were undertaken on single cell protein (SCP) produced by thermotolerant strains ofKluyveromyces marxianus var.marxianus grown on sugar cane molasses at 40°C. The maximum conversion of available sugars to biomass at 45°C was only 10.8% (g dry wt.·g^–1 total sugars). The amino acid composition of the SCP did not differ markedly from that reported for other yeast species.     

The involvement of trehalose in yeast stress tolerance

Summary A total of 12 yeast strains from various genera were examined for their ability to produce ethanol in the presence of high concentrations of glucose. From these studies, the yeastsTorulaspora delbrueckii andZygosaccharomyces rouxii were observed to the most osmotolerant. These osmotolerant yeast strains were also observed to possess high concentrations of intracellular trehalose. Futhermore, these strains were found to be tolerant to long-term storage at –20°C and to storage at 4°C in beer containing 5% (v/v) ethanol. Cells containing high trehalose levels at the time of freezing or cold storage exhibited the highest cell viabilities. Trehalose concentration was observed to increase during growth on glucose, reaching a maximum after 24–48 h. Increasing the incubation temperature from 21 to 40°C also resulted in an increase in intracellular trehalose content. These results suggest that trehalose plays a role in enhancing yeast survival under environmentally stressful conditions.     

A comparison of proline, thiol levels and GAPDH activity in cyanobacteria of different origins facing temperature-stress

Three cyanobacterial strains originating from different habitats were subjected to temperature shift exposures and monitored for levels of proline, thiol and activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Thermophile Mastigocladus laminosus (growth optimum, 40 °C), raised the proline level 4.2-fold at low temperature (20 °C), for the psychrophile Nostoc 593 (growth optimum, 20 °C), it was raised 8-fold at 40 °C while in the mesophile Nostoc muscorum (growth optimum, 30 °C), the imino acid level increased 2.3-fold during temperature shiftdown to 20 °C or 3.5-fold in sets facing shiftup (40 °C). Alterations in thiol levels in the above strains were in line with proline. It is suggested that such fluctuations reflect metabolic shifts as a response to stress. Interestingly, GAPDH activity was maximum at the respective growth temperature optimum of M. laminosus (122 nmol NADPH oxidized min ^–1 mg ^–1 protein) and Nostoc 593 (141 nmol NADPH oxidized min ^–1 mg ^–1 protein) while in N. muscorum, it increased at 40 °C (101 nmol NADPH oxidized min ^–1 mg ^–1 protein) and to 93.3 nmol NADPH oxidized min ^–1 mg ^–1 protein (20 °C) relative to 86 nmol NADPH oxidized min ^–1 mg ^–1 protein at 30 °C. It seems that extremophiles maintain the GAPDH activity/level during growth at their respective temperatures optimal while the mesophile increases it in order to cope up with temperature-stress.     

Production of laccase byBotrytis cinerea and fermentation studies with strain F226

After induction, seven strains ofBotrytis cinerea released into the culture broth considerable amounts of laccase in a brief production time. The set-up of a suitable production process was studied with a selected strain in a 10-L fermenter. The optimum fermentation conditions were a 3% inoculum with a high degree of sporulation, a simple medium containing 20 g L^–1 of glucose and 2 g L^–1 of yeast extract at pH 3.5, 2 g L^–1 gallic acid as inducer, added after 2 days of growth, an agitation speed of 300 rpm, an aeration rate of 1.2 vvm and a temperature of 24°C. By optimizing the culture conditions, the enzyme activity reached 28 U ml^–1 in 5 days with a specific activity of 560 U mg^–1 protein. The best procedure to obtain a suitable crude enzyme preparation was concentration of the supernatant medium to 10% of the initial volume by ultrafiltration, followed by a fractional precipitation with ethanol. The optimum pH and temperature for laccase activity were 5.5 and 40°C, respectively, with syringaldazine as the substrate.     

Xylulose fermentation by Saccharomyces cerevisiae and xylose-fermenting yeast strains

Xylulose fermentation by four strains of Saccharomyces cerevisiae and two strains of xylose-fermenting yeasts, Pichia stipitis CBS 6054 and Candida shehatae NJ 23, was compared using a mineral medium at a cell concentration of 10 g (dry weight)/l. When xylulose was the sole carbon source and fermentation was anaerobic, S. cerevisiae ATCC 24860 and CBS 8066 showed a substrate consumption rate of 0.035 g g cells^–1 h^–1 compared with 0.833 g g cells^–1 h^–1 for glucose. Bakers' yeast and S. cerevisiae isolate 3 consumed xylulose at a much lower rate although they fermented glucose as rapidly as the ATCC and the CBS strains. While P. stipitis CBS 6054 consumed both xylulose and glucose very slowly under anaerobic conditions, C. shehatae NJ 23 fermented xylulose at a rate of 0.345 g g cells^–1 h^–1, compared with 0.575 g g cells^–1 h^–1 for glucose. For all six strains, the addition of glucose to the xylulose medium did not enhance the consumption of xylulose, but increased the cell biomass concentrations. When fermentation was performed under oxygen-limited conditions, less xylulose was consumed by S. cerevisiae ATCC 24860 and C. shehatae NJ 23, and 50%–65% of the assimilated carbon could not be accounted for in the products determined.     

Struktur,Entwicklung und Abbau von Trichocysten inCryptomonas undHemiselmis (Cryptophyceae)

Zusammenfassung Die Trichocysten der Cryptophyceen bestehen im Ruhezustand aus ein oder zwei zylindrischen Körpern mit einer konischen Aushöhlung auf beiden bzw. einer Seite, einem Zentralkörper und einer umgebenden dreischichtigen Membran. Die zylindrischen Körper sind aus einem Band mit langsam zunehmender Breite und 30–40 å Dicke in dichter spiraliger Aufrollung aufgebaut. In den zweigliedrigen Trichocysten sind die zylindrischen Körper von unterschiedlicher Grö\e, der proximale grö\er als der distale, ihre Achsen stehen schrÄg zueinander.Frühstadien der Trichocystenentwicklung liegen ausschlie\lich in nÄchster NÄhe zu dem in Einzahl vorkommenden Dictyosom, von dem sie sich ableiten lassen; sie stellen BlÄschen von 100 bis 160 nm im Durchmesser dar, die ein Trichocystenband von 20 å Dicke mit nur wenigen UmlÄufen und einen Zentralkörper enthalten. Vorhergehende Stadien sind vermutlich BlÄschen von 40 bis 80 nm Durchmesser mit einer kontrastreichen Membran und körnigem, randlich liegendem Inhalt. Im Laufe der Trichocystenentwicklung nehmen die Zahl der UmlÄufe und die Bandbreite vom Zentrum zur Peripherie hin zu. Nach einer eingliedrigen Initialphase beginnt die Entwicklung des zweiten Zylinders in einiger Entfernung vom Dictyosom und führt damit zu zweigliedrigen Trichocysten. In der Regel werden die Trichocysten zur Peripherie verfrachtet, wo sie hauptsÄchlich das Furchen-Schlund-System der Cryptophyceen umsÄumen. Cytolysomen (sekundÄre Lysosomen) mit Trichocystenmaterial sind hÄufig in der NÄhe des Dictyosoms beobachtet worden; sie sprechen für einenin vivo Abbau überschüssiger Trichocysten in Lysosomen.

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Structure, development, and decomposition of trichocysts inCryptomonas andHemiselmis (Cryptophyceae)

Summary The resting trichocysts of theCryptophyceae are composed of one or two cylindrical bodies with a conic excavation on both or one side, respectively, a central body, and a surrounding tripartite membrane. The cylindrical bodies are made up of a tape of slowly increasing width, 30–40 å in thickness, tightly rolled up in a spiral course. In two-membered trichocysts the cylindrical bodies are different in size, the proximal bigger than the distal one, the axes of which are standing oblique to one another.Early stages of development of trichocysts exclusively are lying in close proximity to the single dictyosome, from which they can be derived. These stages are vesicles, 100–160 nm in diameter, containing a trichocyst tape of only a few turns, 20 å in thickness, and a central body. Preceding stages presumably are vesicles, 40–80 in diameter, with an electron opaque membrane and peripheral granules inside. In the course of the trichocyst development, the number of turns and the width of the coiled tape from the center to the periphery are increased. After passing an one-membered initial phase, the development of the second cylinder starts in some distance from the dictyosome, subsequently leading to two-membered trichocysts.Normally the trichocysts are transported to the periphery, where they predominantly border the furrow-gullet-system of theCryptophyceae. Cytolysomes (secondary lysosomes) containing trichocyst material frequently have been found in the vicinity of the dictyosome; this observation supports the view of a decomposition of surplus trichocystsin vivo by lysosomes.

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Herrn Professor Dr. H.Drawert zum 60. Geburtstag gewidmet.

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Für ihre unermüdliche, zuverlÄssige Mitarbeit danke ich FrauChrista Zimmermann und FrÄulein Christel Schlemonat. Der Deutschen Forschungsgemeinschaft bin ich für eine Sachbeihilfe zu Dank verpflichtet.     

The effect of acclimation and glycerol injection on mortality and pupation in larvae of Ephestia kuehniella after exposures at low temperatures

Larvae of Ephestia kuehniella acclimated at 0° and 6° showed greater ability to survive at –10° or –6° than larvae transferred directly from 20°. Injection of glycerol further increased the survival rate.Acclimation did not affect the ability to pupate after exposure at low temperatures. Regardless of previous acclimation increasing larval mortality rates, however, were always accompanied by reduced ability of surviving larvae to pupate.

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Zusammenfassung Bei 0° und 6° takklimatisierte Larven von Ephestia kuehniella zeigten ein größeres Vermögen, niedrige Temperaturen, –10° und –6°, zu überleben als Larven, die unmittelbar von 20° übertragen wurden. Eine Injektion von Glyzerol hatte eine noch größere Wirkung auf das Überlebensvermögen als die Akklimatisation.Das Verpuppungsvermögen der überlebenden Larven nahm nach verlängerter Expositionszeit bei –10° und –6° ab. Ungefähr dasselbe Verhältnis wurde zwischen Mortalität und Verpuppung gefunden, ohne Beziehung auf frühere Akklimatisierungs- oder Versuchstemperaturen.Es scheint daher, daß nur das Überlebensvermögen und nicht die Verpuppungsfähigkeit von der Akklimatisierungstemperatur beeinflußt wird.

     

Fed-batch alcoholic fermentation of sugar cane blackstrap molasses: influence of the feeding rate on yeast yield and productivity

Fed-batch ethanol fermentation tests of sugar cane blackstrap molasses were carried out at 32° C and ph 4.5–5.0, using pressed yeast as inoculum, and with no air supply. Two values of the fermentor filling-up time were adopted: 5 h and 7 h. The feeding rates obeyed equation F=F₀·^–K·t, with K equal to 0.0, 0.2, 0.4, 0.6 and 0.8 h^–1. The average yeast yields and the average yeast productivities increased up to 33% and 45%, respectively, while the ethanol yield (average=76%; standard deviation=4%) was practically unaffected when K increased from 0 to 0.8 h^–1. Correspondence to: E. Aquarone     

Leptospirillum-Like Bacteria and Evaluation of Their Role in Pyrite Oxidation

Two strains of Leptospirillum-like bacteria isolated from dumps of Alaverdi and Akhtala sulfide ore deposits in Armenia were studied. The optimum and maximum temperatures for the growth of both strains were 37 and 40°C, respectively. The pH optimum was 2.0–2.3. Bacterial growth and ferrous iron oxidation were inhibited by yeast extract. The pyrite-leaching activity of the Leptospirillum-like bacteria under mesophilic conditions was close to that of Acidithiobacillus ferrooxidans and exceeded by 2.0–2.7 times the activity of these moderately thermophilic bacteria at 37°C. The leaching of pyrite by Leptospirillum-like bacteria increased in the presence of sulfur-oxidizing bacteria, particularly, in their association with a thermotolerant sulfur-oxidizing bacterium.