Transferable drug resistance in Pseudomonas patients with premature rupture of membranes in Ile-Ife, Nigeria.

Pseudomonas aeruginosa was cultured in eight patients with premature rupture of membranes in a Maternity Unit of the University of Ife Teaching Hospital Complex within a period of 48 h. Three of the strains were found to harbour R-factor DNA conferring high-level resistance to benzylpenicillin, streptomycin, chloramphenicol and tetracycline, while two strains are able to transfer this drug resistance en bloc to drug-sensitive Escherichia coli. The significance of this in the light of a continuing study of drug resistant bacteria in Ile-Ife is discussed.

RNase H is not involved in the induction of stable DNA replication in Escherichia coli.

rnh mutations of Escherichia coli inactivating RNase H activity allow the initiation of rounds of DNA replication in the absence of protein synthesis (stable DNA replication). However, levels of RNase H did not change during or after the induction of stable DNA replication in rnh+ strains by incubation with nalidixic acid or UV irradiation.

Inhibition of early vaccinia virus ribonucleic acid synthesis in interferon-treated chicken embryo fibroblasts.

Pretreatment of chicken embryo cells with homologous but not heterologous interferon inhibits the synthesis of vaccinia virus early messenger ribonucleic acid (mRNA). This inhibition is seen in the presence of cycloheximide, i.e., in the absence of protein synthesis, suggesting that the virion-bound transcriptase may be the target of the antiviral activity associated with interferon treatment. The inhibition of viral mRNA synthesis is dependent on the amount of chicken interferon used. The nonviral interferon inducer, polyriboinosine.polyribocytidine, similarly inhibits viral early mRNA synthesis in a dose-specific manner. The helical polynucleotide polydeoxyinosine.polyribocytidine, which is not an effective interferon inducer in chicken embryo cells, has no effect on viral ribonucleic acid synthesis.

Bacteriophage lambda; abortive infection of bacteria lysogenic for phage P2.

The efficiency of plating of wild-type lambda on a host lysogenic for P2 is less than 10(-6), and only a small number of infected cells produce progeny phage. Lambda can adsorb and inject its DNA normally in such cells; the DNA can circularize and is not nicked or degraded, but replication is severely impaired. Mutants of P2, which as prophages no longer interfere with lambda, have been isolated and found to be recessive to wild type, implying that P2 prophage codes for a diffusible product involved in lambda interference. The P2 gene product responsible for preventing lambda growth also kills recombination-deficient bacteria of the recB and recC classes under conditions where P2 does not normally kill the host. Mutants of lambda that are resistant to interference are recessive to wild-type lambda. Thus lambda actively participates in its own interference. The lambda-mutants that are resistant to interference are unable to synthesize at least two nonessential proteins. In addition, they are unable to grow on recombination-deficient bacteria of the recA class, but they can grow on recA recB double mutants.

Fate of plasmids containing Mu DNA: chromosome association and mobilization.

The fluorescent dye, diamidinophenylindole-dihydrochloride (DAPI) can be added to CsCl gradients to enhance the density resolution of DNA species, independent of their topological configurations. When Proteus mirabilis and Escherichia coli strains carrying an RP4::Mucts plasmid were examined with the use of such a technique, it was found that after thermal induction of the prophage essentially al of the plasmid DNA became associated with the chromosome. This quantitative association is detergent-RNase- and pronase-resistant and dependent on the expression of Mu genes. The association is temporally, and probably functionally, correlated with the onset of Mu DNA replication. Genetic studies with F'::mini Mu plasmids indicate that some of the association results in stable Hfr formation, and does not require the product of Mu gene B.

AIDS in Africa: distinguishing fact and fiction.

The data widely purporting to show the existence and heterosexual transmission in Africa of a new syndrome caused by a retrovirus which induces immune deficiency are critically evaluated. It is concluded that both acquired immune deficiency (AID) and the symptoms and diseases which constitute the clinical syndrome (S) are of long standing in Africa, affect both sexes equally and are caused directly and indirectly by factors other than human immunodeficiency virus (HIV). Seropositivity to HIV in Africans usually represents no more than cross-reactivity caused by an abundance of antibodies induced by the numerous infectious and parasitic diseases which are endemic in Africa. The apparently high prevalence of 'AIDS' and 'HIV' seropositives is therefore not surprising and is not proof of heterosexual transmission of either HIV or AIDS.

Metabolism of Monoterpenes : Metabolic Fate of (+)-Camphor in Sage (Salvia officinalis).

The bicyclic monoterpene ketone (+)-camphor undergoes lactonization to 1,2-campholide in mature sage (Salvia officinalis L.) leaves followed by conversion to the beta-d-glucoside-6-O-glucose ester of the corresponding hydroxy acid (1-carboxymethyl-3-hydroxy-2,2,3-trimethyl cyclopentane). Analysis of the disposition of (+)-[G-(3)H]camphor applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis of the bis-glucose derivative and its transport from leaf to root to be determined, and gave strong indication that the transport derivative was subsequently metabolized in the root. Root extracts were shown to possess beta-glucosidase and acyl glucose esterase activities, and studies with (+)-1,2[U-(14)C]campholide as substrate, using excised root segments, revealed that the terpenoid was converted to lipid materials. Localization studies confirmed the radiolabeled lipids to reside in the membranous fractions of root extracts, and analysis of this material indicated the presence of labeled phytosterols and labeled fatty acids (C(14) to C(20)) of acyl lipids. Although it was not possible to detail the metabolic steps between 1,2-campholide and the acyl lipids and phytosterols derived therefrom because of the lack of readily detectable intermediates, it seemed likely that the monoterpene lactone was degraded to acetyl CoA which was reincorporated into root membrane components via standard acyl lipid and isoprenoid biosynthetic pathways. Monoterpene catabolism thus appears to represent a salvage mechanism for recycling mobile carbon from senescing oil glands on the leaves to the roots.