Some effects of visible light on Escherichia coli

Light above 400 nm had selective effects on Escherichia coli ML-308: several processes or enzymes were strongly inhibited, whereas others were relatively unaffected. There was a correlation between the inhibition of respiration and the inhibition of active uptake of glycine. However, phenylalanine uptake did not show such a correlation. The decrease in adenosine 5'-triphosphate level during the first few minutes of illumination resembled the inactivation kinetics of phenylalanine uptake. The results suggest that phenylalanine uptake may not depend greatly on oxidative energy and may depend on the adenosine 5'-triphosphate level. The results for glycine suggest either that its active uptake and respiration involve a common photosensitive component or alternately, that only the respiratory chain contains the photosensitive component, and that glycine uptake is coupled almost exclusively to respiration. The critical photochemical lesion does not involve d-lactate dehydrogenase, succinate dehydrogenase, or l-alpha-glycerophosphate dehydrogenase since their inactivation rate is markedly lower than that for respiration.     

Tissue-and metal-specific effects of thiolacrylic acids in rats

Kidney copper increased 12- to 18-fold above the normal level in rats administered alpha-mercapto-beta-(2-furyl)acrylic acid (MFA). Kidney zinc increased twofold; plasma zinc increased more than 10-fold and liver zinc increased 30–50%. No other changes in copper, iron, and zinc concentrations were found in these tissues or in bone, brain, heart, lung, skeletal muscle, spleen, or testis. Related compounds produced similar effects, although MFA and its disulfide were the most potent of the compounds tested. These increases in tissue copper and zinc were largely complete after 2–5 d of daily administration of compound. Increased plasma zinc returned toward normal with a half-life of 1.0 d for the process, after dosing was ended; albumin was identified as the species binding the excess zinc in plasma. Kidney copper and zinc, which had increased in the ratio of 3 Cu/Zn, returned to normal levels after dosing was stopped with half-lives of 2.1–2.5 d. Consistent with the observations of highly tissuespecific effects of MFA, copper and zinc balances over 8 weeks of trials were found to be not greatly affected by administration of the compound. Thus, it was not established whether excess metal in affected organs derived from enhanced retention of dietary metal or redistribution from other tissues. Kidney copper and zinc and serum zinc increased even in zinc-deficient rats administered MFA.     

Maternal and neonatal outcome in pregnancies with no risk factors.

Between November 1979 and April 1984, 790 consecutive pregnant women who considered themselves as having a "normal" pregnancy were followed in private practice from 9 weeks'' gestation until 6 weeks post partum. The women had no pre-existing disease or problem classified as a risk to the pregnancy at the time of their first visit, had a singleton pregnancy and gave birth at Notre-Dame Hospital, Montreal. Maternal complications occurred during the course of pregnancy in 181 women (23%). Complications were mostly related to obstetric conditions (10%), such as preterm labour, intrauterine growth retardation (IUGR) and antepartum hemorrhage, or to medical conditions (12%), the most prevalent of which was hypertension (77% of medical conditions). Neonatal complications occurred in 183 infants (23%). The corrected perinatal death rate was 2.5 per 1000. Prematurity, IUGR and dysmaturity/postmaturity accounted for nearly half of the complications. Hyperbilirubinemia occurred in 7% of the cases. Among women without any maternal complications during pregnancy, the frequency rate of neonatal complications was 19%, compared with 23% among the entire group of 790 women. Our results suggest that the absence of maternal complications does not protect the infant from a neonatal complication. Further refinement is needed to identify markers of obstetric, medical and neonatal complications in pregnancies with no risk factors.     

Highly repetitive tRNA(Pro)-tRNA(His) gene cluster from Photobacterium phosphoreum.

A DNA fragment comprising the four tRNA gene sequences of the Escherichia coli argT locus hybridized with two Sau3A-generated DNA fragments from the vibrio Photobacterium phosphoreum (ATCC 11040). Detailed sequence analysis of the longer fragment shows the following gene organization: 5'-promoter-tRNA(Pro)-tRNAPro-tRNA(Pro)-tRNA(His)-tRNA(Pro)-tRNA(Pro)- tRNA(His)-tRNA(Pro)-five pseudogenes derived from the upstream tRNAPro interspersed by putative Rho-independent terminators. This sequence demonstrates the presence of highly repetitive, tandem tRNA genes in a bacterial genome. Furthermore, a stretch of 304 nucleotides from this cluster was found virtually unchanged in the other (shorter) fragment which was previously sequenced. The two clusters together contain eight tRNA(Pro) pseudogenes and eight fully intact tRNA(Pro) genes, an unusually high number for a single eubacterial isoacceptor tRNA. These results show that the organization of some tRNA operons is highly variable in eubacteria.     

Evolution of a tRNA operon in gamma purple bacteria

Genomic DNA from eubacteria belonging to the gamma-3 subdivision of purple bacteria, as classified by Woese (C.R. Woese, Microbiol. Rev. 51:221-271, 1987), were probed with the argT operon of Escherichia coli encoding 5'-tRNA(Arg)-tRNA(His)-tRNA(Leu)-tRNA(Pro)-3'. The homologous operon from Vibrio harveyi was isolated and sequenced. Comparison of the five available sequences of this tRNA cluster from members of the families Enterobacteriaceae, Aeromonadaceae, and Vibrionaceae led to the conclusion that variations in different versions of this operon arose not only by point mutations but also by duplication and addition-deletion of entire tRNA genes. This data base permitted the formulation of a proposal dealing with the evolutionary history of this operon and suggested that DNA regions containing tRNA genes are active centers (hot spots) of recombination. Finally, since the operon from V. harveyi was not highly repetitive and did not contain tRNA pseudogenes, as in the Photobacterium phosphoreum operon, hybridization of genomic DNAs from different photobacterial strains with probes specific for the repeated pseudogene element was performed. We conclude that the phylogenetic distribution of the repetitive DNA is restricted to strains of P. phosphoreum.     

The complex vaginal flora of West African women with bacterial vaginosis

Background

The spectrum of bacteria associated with bacterial vaginosis (BV) has recently expanded through taxonomic changes and the use of molecular methods. These methods have yet to be used in large-scale epidemiological studies in Africa where BV is highly prevalent.

Methods

An analysis of samples obtained during a clinical trial of the management of vaginal discharge in four West African countries. Samples were available from 1555 participants; 843 (54%) had BV. Nucleic acids of 13 bacterial genera or species potentially associated with BV were detected through the polymerase chain reaction.

Results

The associations between various components of the vaginal flora were complex. Excluding Lactobacillus, the other 12 micro-organisms were all associated with each other at the p≤0.001 level. The prevalence of various bacterial genera or species varied according to age, sexual activity and HIV status. In multivariate analysis, the presence of Gardnerella vaginalis, Bifidobacterium, Megasphaera elsdenii, Dialister, Mycoplasma hominis, Leptotrichia, and Prevotella were independently associated with BV as was the absence of Lactobacillus and Peptoniphilus. However, Mobiluncus, Atopobium vaginae, Anaerococcus, and Eggerthella were not independently associated with BV. Unexpectedly, after treatment with a regimen that included either metronidazole or tinidazole, the proportion of patients with a complete resolution of symptoms by day 14 increased with the number of bacterial genera or species present at enrolment.

Conclusions

Numerous bacterial genera or species were strongly associated with each other in a pattern that suggested a symbiotic relationship. BV cases with a simpler flora were less likely to respond to treatment. Overall, the vaginal flora of West African women with BV was reminiscent of that of their counterparts in industrialized countries.     

Effects ofBacillus thuringiensis var.San diego on predation effectiveness,development and mortality ofColeomegilla maculata lengi (Col.: Coccinellidae) larvae

Laboratory experiments were conducted to determine the effects of M-One^™ (Bacillus thuringiensis var.san diego) on larval instars ofColeomegilla maculata lengi Timberlake. Coccinellid larval development (from egg hatch to adult), completed on pollen treated with suspensions of M-One^™ at 20 ml/litre (5.6×10⁸ CPBIU/litre) and 200 ml/litre, took respectively 29.3 and 38.5 days compared with 21.9 days for the control (water). M-One^™ did not cause larval mortality.C. maculata third instars did not show any preference between eggs ofLeptinotarsa decemlineata (Say) treated with water or with M-One^™ at 20 ml/litre. However, at 200 ml M-One^™/litre, the number of eggs attacked was 34.7% lower than the eggs treated with water only, 48 h after the beginning of the test. These results indicate that the use of M-One^™, at the manufacturer's recommended field rate of 20 ml/litre, does not cause a major threat to larvalC. maculata populations.

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Résumé Des bioessais en laboratoire ont été effectués afin de déterminer si les larves de la coccinelle maculée,Coleomegilla maculata lengi Timberlake (Col.: Coccinellidae), sont affectées par M-One^™, un insecticide biologique préparé à partir de la bactérieBacillus thuringiensis var.san diego Berliner et utilisé dans la lutte contre le doryphore de la pomme de terre,Leptinotarsa decemlineata (Say) (Col.: Chrysomelidae). Le développement larvaire, effectué sur du pollen traité avec des concentrations de 20 ml M-One^™/litre (5,6×10⁸ unités internationales de doryphore/litre) et 200 ml M-One^™/litre, a nécessité 29,3 et 38,5 jours respectivement, comparativement à 21,9 jours pour le témoin (eau). M-One^™ n'a pas causé de mortalité chez les larves. Au cours d'un test de 48 h, les larves de stade III n'ont montré aucune préférence entre des œufs traités avec 20 ml M-One^™/litre et des œufs traités avec de l'eau. Par contre avec 200 ml M-One^™/litre, le nombre d'œufs attaqués a diminué significativement de 34,7% par rapport au témoin, 48 h après le début du test. Ces résultats indiquent que l'utilisation de M-One^™ à la concentration recommandée de 20 ml/litre ne représente pas une menace pour les populations larvaires de la coccinelle maculée.