Microbial Ecology of Activated Sludge: I. Dominant Bacteria

Over 300 bacterial strains were isolated from seven samples of activated sludge by plating on sewage agar. Gram-negative bacteria of the genera Zoogloea and Comamonas predominated. Many isolates (51%) showed sudanophilic inclusions of poly-β-hydroxybutyric acid, whereas 34% accumulated iodophilic material on media containing starch. A large number required either vitamins or amino acids, or both, for growth. None of the isolates tested for their ability to bring about changes in autoclaved sewage produced an effluent comparable in quality to the activated sludge control, although the Zoogloea did produce activated sludgelike flocs. A study of 150 bacterial strains isolated from raw sewage revealed that they differed from the sludge isolates in several respects. Coliforms, which constitute nearly a quarter of the sewage isolates, were rarely encountered in sludge.     

Angiotensin II stimulates rapid serine phosphorylation of transcription factor Stat3

Lipid peroxidation (LPO) in rat testis and heart microsomes was compared using the ADP/Fe2+ as initiator with and without ascorbate at different concentrations. The extent of LPO was estimated by the levels of TBARS and PUFA. Without ascorbate, LPO was higher in heart than in testis despite elevated levels of catalase in heart. With increased ascorbate concentrations, a biphasic effect of LPO was observed. For a concentration 0.2 mM, ascorbate acted as pro-oxidant and increased TBARS correlated with decreased PUFA were observed both in testis and heart. Above 0.2 mM, ascorbate acts as antioxidant but differences in the rate of LPO were observed. In heart decreased TBARS correlated with increased PUFA whereas in testis TBARS only decreased, PUFA were not significantly modified. These results suggest different mechanisms in LPO initiation in the two organs. Increasing concentrations of H2O2 produced directly elevated TBARS levels in testis while a lag phase was observed in heart before the increase, suggesting that H2O2 was the essential ROS produced by ascorbate-ADP/Fe2+. The effects of scavengers such as catalase and ethanol showed an inhibitory effect on TBARS production only in testis, suggesting the role of H2O2/OH as an initiator of LPO. In heart, catalase produced a slight increase in TBARS levels whereas no modification was observed with ethanol, suggesting a possible direct activation by ADP/Fe2+ through a metal-oxo intermediate.     

Regulated processing of hepatitis C virus core protein is linked to subcellular localization.

Posttranslational processing and subcellular localization of the HCV core protein are critical steps involved in the assembly of hepatitis C virus (HCV). In this study, both of these events were investigated by in vitro translation and transient COS-1 cell transfection of core protein expression constructs. Mutations at amino acid residues 173 to 174 and 191 to 192 disrupted processing events at the two putative cleavage sites in the C-terminal hydrophobic region of the core protein, indicating that these residues are implicated in the pathway of core protein maturation. As a result, two forms of core protein, C173 and C191, were detected by immunoblotting. Indirect immunofluorescence experiments showed that core proteins C173 and C191, when produced from HCV full-length protein or various polyprotein precursors, displayed a cytoplasmic localization. The C173 species, however, was translocated to the nucleus when expressed in the absence of C191. These findings indicate that preferential cleavage may occur during core protein maturation and that the association of the C191 with the C173 species may contribute to the distinct subcellular distribution of core protein. This may provide a possible mechanism for the control of the diverse biological functions of core protein during HCV replication and assembly.     

Thrombin activates mitogen-activated protein kinase in primary astrocyte cultures

Thrombin is known to evoke numerous inflammatory and proliferative responses in a wide variety of its target cells. Recent studies have demonstrated morphoregulatory and mitogenic effects of thrombin on astroglial cells (astrocytes). The present study deals with thrombin-induced activation of mitogen-activated protein (MAP) kinase in primary cultures of rat astrocytes. Treatment of serum-starved astrocytes with thrombin resulted in a rapid activation of tyrosine (Tyr) phosphorylation of a set of proteins including a prominent one with a molecular mass of 42 kDa (p42). The identity of p42 with MAP kinase was confirmed by MAP kinase-immunoreactivity of isolated [i.e., immunoprecipitated with anti-phosphotyrosine (PY) antibodies] p42 and by increased myelin basic protein (MBP) kinase activity present in MAP kinase immunoprecipitates of thrombin-treated cultures. Pertussis toxin (PTX) pretreatment failed to inhibit thrombin stimulation of p42 phosphorylation, indicating the lack of involvement of PTX sensitive G proteins in the mechanism of activation of MAP kinase by thrombin. Chronic exposure of cultures to phorbol 12-myristate 13-acetate to down-regulate PKC resulted in an attenuation of thrombin-induced p42 Tyr phosphorylation, although H-7, a known PKC inhibitor, failed to block thrombin effect. However, staurosporine, a nonspecific protein kinase inhibitor, prevented the activation of p42 phosphorylation. It is concluded that thrombin induces MAP kinase activation in astrocytes by a mechanism involving a staurosporine-sensitive pathway. © 1995 Wiley-Liss, Inc.     

A Rapid Silver Staining and Destaining Technique for the Nucleolus Organizer Region

Silver staining of nucleolar organizing regions (NOR) is common, but a standard protocol is lacking. A modification of a rapid silver nitrate staining technique for NORs is presented here. Advantages of the modified technique include reliability, speed, cost and the fact that it can be carried out in the light.     

Involvement of 4-hydroxymandelic acid in the degradation of mandelic acid by Pseudomonas convexa.

A microorganism capable of degrading DL-mandelic acid was isolated from sewage sediment of enrichment culture and was identified as Pseudomonas convexa. It was found to metabolize mandelic acid by a new pathway involving 4-hydroxymandelic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid as aromatic intermediates. All the enzymes of the pathway were demonstrated in cell-free extracts. L-Mandelate-4-hydroxylase, a soluble enzyme, requires tetrahydropteridine, nicotinamide adenine dinucleotide phosphate, reduced form, and Fe2+ for its activity. The next enzyme, L-4-hydroxymandelate oxidase (decarboxylating), a particulate enzyme, requires flavine adenine dinucleotide and Mn2+ for its activity. A nicotinamide adenine dinucleotide-dependent, as well as a nicotinamide adenine dinucleotide phosphate-dependent, benzaldehyde dehydrogenase has been resolved and partially purified.     

The possibility of predicting solute uptake and plant growth response from independently measured soil and plant characteristics

Summary The growth and nitrogen uptake response of rape plants to nitrate concentration at the root surface were studied in solution culture in a controlled environment cabinet over a period of 24 days. NO₃ ^– was supplied at the rates of 10^–5 M, 5×10^–5 M, 10^–4 M, 10^–3 M and 10^–2 M in solution and was maintained near these levels.With increasing mean N concentration in the tissues, the relative growth rate and leaf area ratio increased and unit leaf rate decreased slightly. Values of all three growth parameters decreased with plant age.The shoot: root dry weight ratios and their N content ratios increased with increasing mean per cent N in the plant. The length or surface area per unit dry weight of roots was correlated negatively with per cent N and positively with age.The maximum mean inflow of nitrate to rape roots decreased sharply with age. The concentration at which half maximal mean inflow was attained was 3.44×10^–5 M NO₃ ^–.     

The possibility of predicting solute uptake and plant growth response from independently measured soil and plant characteristics

Summary Rape plants were grown in solutions of 10^-6, 10^-5, 10^-4 and 10^-3 M phosphate in a controlled environment that gave near optimum climatic conditions for growth. Uptake and growth were followed by replicate harvests taken every five days. The relation between the mean root absorbing power, and the concentration of P in solution was derived. The relations between the % P in the shoot dry matter and the other parameters of the growth model described in paper I were also determined. Growth rates were exceptionally high, with RGR values above 0.5 g/g/d in solutions of concentration 10^-5 M and more during the early stages of growth. RGR was reduced to about half this value in 10^-6 M P. The range of response to solution concentration in these conditions therefore lay between 10^-6 and 10^-5 M P. In solutions of 10^-6 and 10^-5 M P root hairs were abundant but in solutions of 10^-4 and 10^-3 M P, they were absent. Rape had a high UAR for P as a result of its high RGR, but it had a correspondingly large root surface area per unit plant weight. Onions (see Paper II of this series) had an inherently lower RGR and UAR for P, but had a comparatively low root surface area per unit plant weight. It appears that these contrasting features of rape and onions broadly compensated for each other so that the P concentration range over which the two species responded was much the same.Soil Science Labaratory, Department of Agricultural Science, University of Oxford     

A germacranolide from Inula indica

Chemical investigation of Inula indica has yielded a new germacranolide, 1β,10α-epoxy-2α,9β-dihydroxy-5β-acetoxy-6α(2-methylbutyryloxy)-germacran-8α,12-olide, whose structure and stereochemistry have been established from the spectral characteristics of the compound and its derivatives.