DNA chips for yeast biotechnology. The case of wine yeasts

The yeast Saccharomyces cerevisiae is one of the most popular model organisms. It was the first eukaryote whose genome was sequenced. Since then many functional analysis projects have tried to find the function of many genes and to understand its metabolism in a holistic way. Apart from basic science this microorganism is of great interest in several biotechnology processes, such as winemaking. Only global studies of the cell as a whole can help us to understand many of the technical problems facing winemaking. DNA chip technology is one of the most promising tools for the analysis of cell physiology. Yeast has been the model organism for the development of this technique. Many of the studies can be applied to improve our knowledge of wine strains. Nevertheless wine strains are quite different in some aspects from the laboratory reference strains so a particular study of wine strains and especially during the winemaking process is needed. During the past two years some groups have started this study and the first results have been published. We review here the current state of the knowledge of wine yeast and the capacity of DNA chip technology for its improvement.     

Scedosporium apiospermum keratitis

A case of Scedosporium apiospermum keratitis is reported in a 65-year-old farmer referred for treatment of an extensive corneal ulcer in the left eye. Direct examination of scrapes revealed abundant filamentous septate hyphae; all cultures were consistently positive for the same fungus, identified later as Scedosporium apiospermum. The patient successfully responded to treatment with amphotericin B.     

l-serine and GABA uptake by synaptosomes during postnatal development of rat

Postnatal development changes in mechanisms of synaptosomal amino acid transport have been studied in rat cerebral cortex. Specific uptake of radiolabeled l-serine was examined and compared with that of radiolabeled GABA using synaptosomes-enriched fractions freshly prepared from cerebral cortex at different postnatal days from the birth to young adulthood. The preparations were incubated with 10 nM of [³H]l-serine and 10 nM of [³H]-GABA in either the presence or absence of NaCl, KCl or choline chloride, at 2 and 30 °C, for different periods up to 30 min. The uptake of [³H]l-serine was temperature dependent in synaptosomal fractions prepared from cerebral cortex of rats in postnatal days 5, 7, 13 and 21, but stronger dependence was observed in adult brain, irrespective of the presence of Na⁺, K⁺ or choline ions. At all postnatal ages studied, [³H]-GABA uptake showed a high activity in the presence of Na⁺ ions and at 30 °C. The values of K_m were 90–489 μM in l-serine uptake. However, in the uptake of GABA the values of K_m were 80–150 μM. The highest values of V_max were obtained at 5 and 21 postnatal days for both transport systems. These results indicate that the uptake of l-serine and GABA are regulated differentially during postnatal development.     

Caspase-3 is not activated in seizure-induced neuronal necrosis with internucleosomal DNA cleavage

A caspase-3-activated DNase produces internucleosomal DNA cleavage (DNA laddering). We determined whether caspase-3 is activated by lithium-pilocarpine-induced status epilepticus in six brain regions with necrosis-induced DNA laddering. The thymuses of adult rats given methamphetamine or normal saline were used as controls for apoptosis. Some 6-8 h after methamphetamine treatment, thymocytes showed apoptosis by electron-microscopic examination, positive terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL), DNA laddering, cleavage of caspase-3 into its active p17 subunit, active caspase-3 immunoreactivity, and a 25-fold increase in caspase-3-like activity. Six hours after SE, necrotic neurons by electron-microscopic examination in hippocampus, amygdala and piriform, entorhinal and frontal cortices showed no TUNEL and no DNA laddering. Twenty-four hours after seizures, most necrotic neurons were negative for TUNEL, some were positive, but all regions showed DNA laddering. However, 6 and 24 h after seizures, active caspase-3 immunoreactivity was negative, caspase-3-like activity did not increase, and western blot analysis failed to show the p17 subunit. In addition, 24 h after seizures,microdialytic perfusion of carbobenzoxy-valyl-alanyl-aspartyl (O-methylester) fluoromethylketone was not neuroprotective. Thus, caspase-3 is not activated in brain regions with seizure-induced neuronal necrosis with DNA laddering. Either caspase-activated DNase is activated by another enzyme, or a caspase-independent DNase is responsible for the DNA cleavage.     

Spatial patterns in phage-Rhizobium coevolutionary interactions across regions of common bean domestication

Bacteriophages play significant roles in the composition, diversity, and evolution of bacterial communities. Despite their importance, it remains unclear how phage diversity and phage-host interactions are spatially structured. Local adaptation may play a key role. Nitrogen-fixing symbiotic bacteria, known as rhizobia, have been shown to locally adapt to domesticated common bean at its Mesoamerican and Andean sites of origin. This may affect phage-rhizobium interactions. However, knowledge about the diversity and coevolution of phages with their respective Rhizobium populations is lacking. Here, through the study of four phage-Rhizobium communities in Mexico and Argentina, we show that both phage and host diversity is spatially structured. Cross-infection experiments demonstrated that phage infection rates were higher overall in sympatric rhizobia than in allopatric rhizobia except for one Argentinean community, indicating phage local adaptation and host maladaptation. Phage-host interactions were shaped by the genetic identity and geographic origin of both the phage and the host. The phages ranged from specialists to generalists, revealing a nested network of interactions. Our results suggest a key role of local adaptation to resident host bacterial communities in shaping the phage genetic and phenotypic composition, following a similar spatial pattern of diversity and coevolution to that in the host.Subject terms: Microbial ecology, Bacteriophages, Microbial ecology, Biogeography, Microbial communities     

Neurotransmitter release regulated by a MALS-liprin-alpha presynaptic complex

Synapses are highly specialized intercellular junctions organized by adhesive and scaffolding molecules that align presynaptic vesicular release with postsynaptic neurotransmitter receptors. The MALS/Veli-CASK-Mint-1 complex of PDZ proteins occurs on both sides of the synapse and has the potential to link transsynaptic adhesion molecules to the cytoskeleton. In this study, we purified the MALS protein complex from brain and found liprin-alpha as a major component. Liprin proteins organize the presynaptic active zone and regulate neurotransmitter release. Fittingly, mutant mice lacking all three MALS isoforms died perinatally with difficulty breathing and impaired excitatory synaptic transmission. Excitatory postsynaptic currents were dramatically reduced in autaptic cultures from MALS triple knockout mice due to a presynaptic deficit in vesicle cycling. These findings are consistent with a model whereby the MALS-CASK-liprin-alpha complex recruits components of the synaptic release machinery to adhesive proteins of the active zone.