How to enter the state of dormancy? A suggestion by Trichoderma atroviride conidia.

It is generally accepted that conidia, propagules of filamentous fungi, exist in the state of dormancy. This state is defined mostly phenomenologically, e.g., by germination requirements. Its molecular characteristics are scarce and are concentrated on the water or osmolyte content, and/or respiration. However, a question of whether conidia are metabolic or ametabolic forms of life cannot be answered on the basis of available experimental data. In other words, are mature conidia open thermodynamic systems as are mycelia, or do they become closed upon the transition to the dormant state? In this article, we present observations which may help to define the transition of freshly formed conidia to the putative dormant forms using measurements of selected enzyme activities, 1H- and 13C-NMR and LC-MS-metabolomes, and 14C-bicarbonate or 45Ca2+ inward transport. We have found that Trichoderma atroviride and Aspergillus niger conidia arrest the 45Ca2+ uptake during the development stopping thereby the cyclic (i.e., bidirectional) Ca2+ flow existing in vegetative mycelia and conidia of T. atroviride across the cytoplasmic membrane. Furthermore, we have found that the activity of α-ketoglutarate dehydrogenase was rendered completely inactive after 3 weeks from the conidia formation unlike of other central carbon metabolism enzymes. This may explain the loss of conidial respiration. Finally, we found that conidia take up the H14CO3- and convert it into few stable compounds within 80 d of maturation, with minor quantitative differences in the extent of this process. The uptake of H13CO3- confirmed these observation and demonstrated the incorporation of H13CO3- even in the absence of exogenous substrates. These results suggest that T. atroviride conidia remain metabolically active during first ten weeks of maturation. Under these circumstances, their metabolism displays features similar to those of chemoautotrophic microorganisms. However, the Ca2+ homeostasis changed from the open to the closed thermodynamic state during the early period of conidial maturation. These results may be helpful for studying the conidial ageing and/or maturation, and for defining the conidial dormant state in biochemical terms.

Chemiluminescence Detection of Hydrogen Sulfide Release by ß-Lactamase-Catalyzed ß-Lactam Biodegradation: Unprecedented Pathway for Monitoring ß-Lactam Antibiotic Bacterial Resistance.

ß-Lactamase positive bacteria represent a growing threat to human health because of their resistance to commonly used antibiotics. Therefore, development of new diagnostic methods for identification of ß-lactamase positive bacteria is of high importance for monitoring the spread of antibiotic-resistant bacteria. Here, we report the discovery of a new biodegradation metabolite (H2S), generated through ß-lactamase-catalyzed hydrolysis of ß-lactam antibiotics. This discovery directed us to develop a distinct molecular technique for monitoring bacterial antibiotic resistance. The technique is based on a highly efficient chemiluminescence probe, designed for detection of the metabolite, hydrogen sulfide, that is released upon biodegradation of ß-lactam by ß-lactamases. Such an assay can directly indicate if antibiotic bacterial resistance exists for a certain examined ß-lactam. The assay was successfully demonstrated for five different ß-lactam antibiotics and eight ß-lactam resistant bacterial strains. Importantly, in a functional bacterial assay, our chemiluminescence probe was able to clearly distinguish between a ß-lactam resistant bacterial strain and a sensitive one. As far as we know, there is no previous documentation for such a biodegradation pathway of ß-lactam antibiotics. Bearing in mind the data obtained in this study, we propose that hydrogen sulfide should be considered as an emerging ß-lactam metabolite for detection of bacterial resistance.

Novel, efficient total synthesis of natural 20(S)-camptothecin.

Enantiopure 20(S)-camptothecin has been prepared from a known hydroxypyridone through a novel approach that involves a Claisen rearrangement, an asymmetric nucleophilic ethylation, a Heck coupling and a Friedländer condensation as the key transformations.

Concise synthesis of 22-hydroxyacuminatine, cytotoxic camptothecinoid from Camptotheca acuminata, by pyridone benzannulation.

A short, efficient synthesis of 22-hydroxyacuminatine, starting from a readily accessible hydroxy pyridone, is presented; key steps include a Heck coupling with methyl pentadienoate, a flash vacuum pyrolytic cyclization, and a Friedländer condensation.