CORRESPONDENCE BETWEEN PHYLOGENY AND MORPHOLOGY OF SNOWELLA SPP. AND WORONICHINIA NAEGELIANA,CYANOBACTERIA COMMONLY OCCURRING IN LAKES1

In this study, the first reported isolates of the genera Snowella and Woronichinia were characterized by 16S rRNA gene sequencing and morphological analysis. Phylogenetic studies and sequences for these genera were not available previously. By botanical criteria, the five isolated strains were identified as Snowella litoralis (Häyrén) Komárek et Hindák Snowella rosea (Snow) Elenkin and Woronichinia naegeliana (Unger) Elenkin. This study underlines the identification of freshly isolated cultures, since the Snowella strains lost the colony structure and were not identifiable after extended laboratory cultivation. In the 16S rRNA gene analysis, the Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. Thus, our results show that the morphology of the genera Snowella and Woronichinia was in congruence with their phylogeny, and their phylogeny seems to support the traditional botanical classification of these genera. Furthermore, the genera Snowella and Woronichinia occurred commonly and might occasionally be the most abundant cyanobacterial taxa in mainly oligotrophic and mesotrophic Finnish lakes. Woronichinia occurred frequently and also formed blooms in eutrophic Czech reservoirs.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Regulation of nitrogenase activity by oxygen in Azospirillum brasilense and Azospirillum lipoferum.

The nitrogenase activity of the microaerophilic bacteria Azospirillum brasilense and A. lipoferum was completely inhibited by 2.0 kPa of oxygen (approximately 0.02 atm of O2) in equilibrium with the solution. The activity could be partially recovered at optimal oxygen concentrations of 0.2 kPa. In contrast to the NH4+ switch off, no covalent modification of the nitrogenase reductase (Fe protein) was involved, as demonstrated by Western-blotting and 32P-labeling experiments. However, the inhibition of the nitrogenase activity under anaerobic conditions was correlated with covalent modification of the Fe protein. In contrast to the NH4+ switch off, no increase in the cellular glutamine pool and no modification of the glutamine synthetase occurred under anaerobic switch-off conditions. Therefore, a redox signal, independent of the nitrogen control of the cell, may trigger the covalent modification of the nitrogenase reductase of A. brasilense and A. lipoferum.     

Purification and characterization of Rhodobacter sphaeroides acyl carrier protein

Acyl carrier protein (ACP) has been purified from the facultative phototrophic bacterium Rhodobacter sphaeroides. The ACP preparation was greater than 95% homogeneous as determined by native and disodium dodecyl sulfate (Na2DodSO4)-polyacrylamide gel electrophoreses and N-terminal amino acid analysis. Amino acid compositional analysis revealed that the protein contains approximately 75 amino acids, has a calculated minimum molecular weight of 8700, and lacks the amino acids tyrosine and tryptophan. The presence of the characteristic 4'-phosphopantetheine prosthetic group was indicated by the occurrence of equimolar quantities of beta-alanine and taurine in amino acid hydrolysates and was confirmed by independent chemical analysis. The protein displayed a pI of 3.8 and had a calculated partial specific volume of 0.732 mL/g. The primary structure of the protein has been determined for the first 46 amino acid residues from the N terminus of the molecule, and the region of the molecule encompassing the amino acids from residues 31 to 44 was found to have 100% homology with the identical residues in Escherichia coli ACP. In contrast to E. coli ACP, R. sphaeroides ACP migrated according to its molecular weight during Na2DodSO4 gel electrophoresis, was resistant to pH-induced denaturation, and comigrated with the cis-vaccenoyl-ACP derivative during native gel electrophoresis. It is proposed that the basis for these properties is the enhanced hydrophobic character of the protein.     

Structural analysis of 5S rRNA, 5S rRNA-protein complexes and ribosomes employing RNase H and d(GTTCGG)

The hybridization of d(GTTCGG) to eubacterial 5S rRNAs, 5S rRNA-protein complexes, 70S ribosomes and 50S and 30S ribosomal subunits was investigated. This oligonucleotide, which may be considered to be an analogue of the T psi CG loop of tRNAs, was chosen in order to investigate a possible interaction between tRNAs with ribosomal components during protein synthesis. The hybridization was analysed by RNase H hydrolysis studies and, in the case of the ribosomes and ribosomal subunits, in addition with the radioactively labelled oligodeoxyribonucleotide in binding studies. The results obtained lead to the conclusion that nucleotides in loop c, i.e. positions 42-47, are available for oligonucleotide interaction in free Escherichia coli and Bacillus stearothermophilus 5S rRNAs and not available in the corresponding 5S rRNA-protein complexes. The 70S ribosomes and ribosomal subunits did not interact with the oligonucleotide. Under the assumption that d(GTTCGG) is an analogue of the T psi CG loop of tRNAs and in view of the results obtained, we conclude that in the unprogrammed ribosomes the T psi CG loop of tRNAs does not interact via standard Watson-Crick base pairs with the ribosomal 5S, 16S or 23S RNAs.     

Immunofluorescent localization of collagen types I,III and IV,fibronectin, laminin,and basement membrane proteoglycan in developing mouse skin

Summary The distribution of various extracellular matrix components was studied in frozen sections of embryonic (14–18 days) and early postnatal (birth and 4 days post parturn) dorsal mouse skin using monospecific antibodies and indirect immunofluorescence. Basement membrane zone components — type IV collagen, laminin and heparan sulphate proteoglycan — were found to be uniformly and unchangingly distributed along the dermal-epidermal junction. In contrast, the distribution of interstitial matrix components — types I and III collagen, and fibronectin — was heterogeneous and varied with the stages of hair development. Collagens became sparse and were eventually completely removed from the prospective dermal papilla and from a one-cell-thick sheath of dermal cells around hair buds. They remained absent from the dermal papilla throughout hair organogenesis. Fibronectin was always present around dermal papilla cells and was particularly abundant along the dermal-epidermal junction of hair rudiments, as well as underneath hair buds. In contrast, in interfollicular skin, collagens accumulated in increasing density, while fibronectin became progressively sparser. It thus appears that interstitial collagens and fibronectin are distributed in a manner which is related to hair morphogenesis. In morphogenetically active regions, collagen density is low, while that of fibronectin is high. Conversely, in histologically stabilized zones, collagen is abundant and fibronectin is sparse. This microheterogeneous distribution of interstitial collagens and of fibronectin might thus constitute part of the morphogenetic message that the dermis is known to transmit to the epidermis during the development of skin and of cutaneous appendages.