Radiochemical investigation of the respiration of spores of Bacillus cereus

Summary The endogenous respiration of ¹⁴C-labelled spores of B. cereus was measured through the ¹⁴CO₂ produced, and the rate expressed as Q (l CO₂/hxmg). New upper limits for respiration in various conditions have been set.Dry spores had no measurable activity; Q<10^–4 at room temperature and <10^–3 at 35° C. For wet spores of different harvests, at 30°C, Q lay between 0.0013 to 0.067. Near 40° C, respiration showed a maximum. Thermal history has a great influence on Q. CO₂ production by heat-killed spores is attributed largely to infection.Water or 10^–3 m sodium phosphate buffer (pH=6.5) gave equal spore respiration, in strong NaCl it was less. Azide enhanced respiration dramatically. A temporary increase was also found with non-radioactive glucose. Exogenous respiration of spores in glucose exceeded endogenous respiration.Endogenous and exogenous respiration of vegetative forms were much larger than those of spores and were time-dependent. The ratio of minimum (endogenous, dry spores) and maximum (exogenous, wet vegetative cells) respiration was at least 3x10⁵.     

Early transfer of genes determining transfer functions by some Hfr strains in Escherichia coli K12

Summary Sixty-eight Hfr strains were examined for their ability to transfer early in conjugation the transfer genes carried by the integrated sex factor. This was measured by mating these strains with F^- phenocopied recipient cultures of strains carrying transfer-deficient Flac ⁺ factors, and then measuring the ability of the recipient strains to transfer lac ⁺ to a further recipient strain. Most Hfr strains did not complement the missing transfer functions, though in some strains complementation was observed. It is concluded that on the sex factors of different Hfr strains either the site at which integration occurs or the origin of transfer must vary.     

Isolation and characterisation of Hfr strains from a recombination-deficient strain of Escherichia coli

Summary A T6^s RecA^- strain carrying a lac proB deletion and F_ts lac ⁺ was challenged with phage T6 and survivors which were both T6^r and Lac⁺ at 42° were tested for fertility. Among these were a number of Hfr strains which had their points of origin at or near the tsx locus and which still carried the recA allele. These arose in comparable frequencies in the RecA^- strain and in a Rec⁺ analogue. We conclude that such integration does not require the RecA function. The rate of chromosome transfer was similar in one such RecA^- Hfr and its Rec⁺ derivative; the yield of recombinants from the RecA^- strain was slightly lower than from its Rec⁺ derivative.     

Possible relationship between cyclic AMP and idiophasic metabolism in the white rot fungus Phanerochaete chrysosporium.

In the hymenomycete Phanerochaete chrysosporium, a 10-fold increase in intracellular cyclic AMP preceded the onset of the two idiophasic activities, lignin degradation and veratryl alcohol production. Further, addition of L-glutamate during this period reduced cyclic AMP levels and suppressed ligninolytic activity.     

Dependence of sulphate uptake by Anacystis nidulans on energy,on osmotic shock and on sulphate starvation

Effects of treatments with proteolytic enzymes and protein-modifying reagents on flocculation of brewer's yeast IFO 2018 were investigated. The floc-forming ability of the yeast cells was irreversibly eliminated by treatment with papain, trypsin, chymotrypsin or pepsin, indicating that certain proteins on the cell surface participate in the yeast flocculation. Chemical modification with reagents, known to act on disulfide bridges, carboxyl and/or phosphate groups, phenolic groups, amino groups, and imidazole groups, also destroyed the ability to flocculate, although in some cases a high concentration (8 M) of urea was necessary in addition to protein-modifying reagents. Thus, it is suggested strongly that these functional groups of amino acid residues of the proteins are essential for the floc-forming ability of brewer's yeast cells.Abbreviations Used CMA buffer 0.20 M Na-acetate buffer (pH 4.5) containing 0.009 M CaCl₂ and 0.004 M MgSO₄ - S.P. sedimentation percentage (see text) - SH sulfhydryl     

Xylanolytic enzyme activities produced by mesophilic and thermophilic actinomycetes grown on graminaceous xylan and lignocellulose

Mesophilic and thermophilic strains of actinomycetes were grown on media containing graminaceous xylan or lignocellulose. Aliquots of the culture fluids were sampled and assayed for enzyme activities involved in the degradation of hemicellulose. Xylanase, acetyl esterase and α-arabinofuranosidase activities could be detected after different times of incubation; their production was also dependent on the growth medium. The highest levels of xylanase activity were found in cultures of strains of Streptomyces, Actinomadura sp. and Saccharomonospora viridis. Streptomyces cyaneus produced the highest amount of arabinofuranosidase whereas acetyl esterase activities were highest in S. cyaneus, S. viridis and Pseudonocardia thermophila .     

Untersuchung der Lichtabhängigkeit der Aufnahme von Rubidium,Zink, Kobalt,Blei und Cer durch Chlorella nach einer Flußmethode

Summary A flow method for the measurement of the uptake of labelled substances by plant cells has been developed. Accumulation in the medium of substances released by the plants is thereby avoided, and a more precise determination of the rate of uptake—also of transients—than through the usual, static methods is possible. The time function of the stimulation of the uptake of Rb by Chlorella fusca by light at 30° has been analyzed, and the component believed to represent active transport separated from other components that have shorter time constants; at 3° the active component is much reduced.In the cases of the heavy metal ions Zn, Co, Pb and Ce, even after presaturation with the ions in the dark for the suppression of the short-term uptake the light-independent long-term uptake is far stronger than with Rb. Moreover, for Zn and Co the uptake is greatly stimulated by light at 30°, but little if at all at 5°. No stimulation was found under any conditions with Ce. With Pb, the light effect was hardly reproducible, and in any case extremely small. The energy-dependent transport of Zn and Co is probably active.

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Herrn Prof. Dr. K. Mothes zum 70. Geburtstag in Verehrung gewidment.     

The Impact of Model Peptides on Structural and Dynamic Properties of Egg Yolk Lecithin Liposomes – Experimental and DFT Studies

Electron spin resonance (ESR), ¹H‐NMR, voltage and resistance experiments were performed to explore structural and dynamic changes of Egg Yolk Lecithin (EYL) bilayer upon addition of model peptides. Two of them are phenylalanine (Phe) derivatives, Ac‐Phe‐NHMe ( 1 ) and Ac‐Phe‐NMe₂ ( 2 ), and the third one, Ac‐(Z)‐ΔPhe‐NMe₂ ( 3 ), is a derivative of (Z)‐α,β‐dehydrophenylalanine. The ESR results revealed that all compounds reduced the fluidity of liposome's membrane, and the highest activity was observed for compound 2 with N‐methylated C‐terminal amide bond (Ac‐Phe‐NMe₂). This compound, being the most hydrophobic, penetrates easily through biological membranes. This was also observed in voltage and resistance studies. ¹H‐NMR studies provided a sound evidence on H‐bond interactions between the studied diamides and lecithin polar head. The most significant changes in H‐atom chemical shifts and spin‐lattice relaxation times T₁ were observed for compound 1 . Our experimental studies were supported by theoretical calculations. Complexes EYL? Ac‐Phe‐NMe₂ and EYL? Ac‐(Z)‐ΔPhe‐NMe₂, stabilized by NH???O or/and CH???O H‐bonds were created and optimized at M06‐2X/6‐31G(d) level of theory in vacuo and in H₂O environment. According to our molecular‐modeling studies, the most probable lecithin site of H‐bond interaction with studied diamides is the negatively charged O‐atom in phosphate group which acts as H‐atom acceptor. Moreover, the highest binding energy to hydrocarbon chains were observed in the case of Ac‐Phe‐NMe₂ ( 2 ).     

The effect of β‐methylation on the conformation of α, β‐dehydrophenylalanine: a DFT study

Dehydroamino acids are non‐coded amino acids that offer unique conformational properties. Dehydrophenylalanine (ΔPhe) is most commonly used to modify bioactive peptides to constrain the topography of the phenyl ring in the side chain, which commonly serves as a pharmacophore. The Ramachandran maps (in the gas phase and in CHCl₃ mimicking environments) of ΔPhe analogues with methyl groups at the β position of the side chain as well as at the C‐terminal amide were calculated using the B3LYP/6‐31 + G** method. Unexpectedly, β‐methylation alone results in an increase of conformational freedom of the affected ΔPhe residue. However, further modification by introducing an additional methyl group at C‐terminal methyl amide results in a steric crowding that fixes the torsion angle ψ of all conformers to the value 123°, regardless of the Z or E position of the phenyl ring. The number of conformers is reduced and the accessible conformational space of the residues is very limited. In particular, (Z)‐Δ(βMe)Phe with the tertiary C‐terminal amide can be classified as the amino acid derivative that has a single conformational state as it seems to adopt only the β conformation. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.