Aqueous plant extracts as stimulators of laccase production in liquid cultures of Lentinus edodes

Summary Total and specific activities of extra-cellular laccases from Lentinus edodes were enhanced by adding corn straw and chestnut juice to the liquid growth medium. The aqueous extracts were chemically characterized and revealed the presence of several phenolic and non-phenolic compounds. Extensive extraction of these components from the tested extracts completely annulled their stimulating properties on laccase production, suggesting that these compounds can act at micromole levels.     

A sensitive RNase protection assay using33P labeled antisense riboprobes

This article presents for the first time a modified protocol for RNase protection analysis that allows the substitution of³²P with³³P without loss of the high sensitivity of this method achieved with³²P. With this protocol, we were able to detect at least 1 pg of specific mRNA. In the RNase protection analysis³³P labeled riboprobes are more advantageous with regard to an easier handling and better resolution.     

Effect of chloramphenicol,antimycin A and hydroxamate on the morphogenetic development of the dimorphic ascomyceteEndomycopsis capsularis

Mitochondrial protein synthesis, primary (antimycin-sensitive) respiration and secondary (antimycin-insensitive, salicyl-hydroxamate-sensitive) respiration, have been characterized in the dimorphic yeastEndomycopsis capsularis. The inhibition by chloramphenicol (CAP) of the morphogenetic development from the yeast-like form to the mycelial structure in this yeast could represent the intervention in the morphogenetic process of mitochondrial protein synthesis, since chloramphenicol blocks in vivo and in vitro mitochondrial protein synthesis. In fact, other functions such as primary and secondary respiration, do not seem to play a role in the morphogenetic development since their inhibition by antimycin A (AA) or by salicyl-hydroxamic acid (SHAM) does not affect the process. In addition, mitochondrial protein synthesis has been shown to be uninhibited by the two respiratory inhibitors.     

Biofilm induced tolerance towards antimicrobial peptides

Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically regulated tolerant subpopulation formation and not caused by a general biofilm property. No significant difference in survival was detected when the strains were challenged with ciprofloxacin. Our data show that biofilm formation confers increased colistin tolerance to cells within the biofilm structure, but the protection is conditional being dependent on the structural organization of the biofilm, and the induction of specific tolerance mechanisms.     

Effects of low electric current (LEC) treatment on pure bacterial cultures

AIMS: This research focused on the effects of low electric current (LEC) on the cell viability and metabolic activity of Escherichia coli and Bacillus cereus. METHODS AND RESULTS: Different LEC intensities at fixed amperage were applied, employing either graphite or copper electrode pairs, and the effects were determined by conventional cultural methods and bioindicators. On E. coli, the LEC with graphite electrodes at 5 and 10 mA led to no significant variation, but at 20 and 40 mA there was increasing inhibition of both the enzymatic activities and growth, and a reduction in ATP content. On B. cereus, similar experiments at the lower amperages did not have any inhibitor effects, however, the 40 mA current stimulated growth, ATP content and some enzymatic activities. The LEC treatment using copper electrodes caused, already at 5 mA, inhibition of bacterial growth and metabolic and enzymatic activities in both E. coli and B. cereus. CONCLUSIONS: On the basis of the obtained results using different amperages and electrodes, we can conclude that E. coli seem to be more sensitive compared with B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY: The study increases the knowledge on LEC treatment effects on the pure bacterial cultures.     

Effect of Acute and Chronic Administration of Methylphenidate on Mitochondrial Respiratory Chain in the Brain of Young Rats

Methylphenidate is commonly used for the treatment of attention deficit/hyperactivity disorder. There are still few works regarding the effects of methylphenidate on brain energy metabolism. Thus, in the present study we evaluated the effect of chronic administration of methylphenidate on the activities of mitochondrial respiratory chain complexes I and III in the brain of young rats. The effect of acute administration of methylphenidate on mitochondrial respiratory chain complexes I, II, III and IV in the brain of young rats was also investigated. For acute administration, a single injection of methylphenidate was given to rats on postnatal day 25. For chronic administration, methylphenidate injections were given starting at postnatal day 25 once daily for 28 days. Our results showed that complexes I and III were not affected by chronic administration of methylphenidate. Moreover, the acute administration of methylphenidate decreased complex I activity in cerebellum and prefrontal cortex, whereas complexes II, III and IV were not altered.