New nucleic dyes for pico-and nanoplankton cytometric analysis

Flow cytometry (FCM) is a promising tool in the field of aquatic phytoplankton ecology because it allows for multi-parameter assessment of the physiological state of individual cells in an algal population. It can help to elucidate major questions such as phytoplankton taxa identification, the evaluation of cell quantity and viability, and the measuring of phytoplankton and general microbial metabolic activities. Traditionally, microalgal characterization is performed by microscopic analysis using UV-excited nuclear dyes (e.g. Hoechst and DAPI) or dyes that are excited in the blue-green part of the spectrum such as propidium iodide and eosin. The development of multi-laser cytometric systems has widened the possibilities for multi-parametric analysis and cell sorting of phytoplankton populations. Notwithstanding, significant algae autofluorescence originating from different types of chlorophyll and accessory pigments may overlap with propidium iodide and/or eosin staining and affect the resolution of algae clusters and cell sorting

New nucleic dyes for pico-and nanoplankton cytometric analysis

Flow cytometry (FCM) is a promising tool in the field of aquatic phytoplankton ecology because it allows for multi-parameter assessment of the physiological state of individual cells in an algal population. It can help to elucidate major questions such as phytoplankton taxa identification, the evaluation of cell quantity and viability, and the measuring of phytoplankton and general microbial metabolic activities. Traditionally, microalgal characterization is performed by microscopic analysis using UV-excited nuclear dyes (e.g. Hoechst and DAPI) or dyes that are excited in the blue-green part of the spectrum such as propidium iodide and eosin. The development of multi-laser cytometric systems has widened the possibilities for multi-parametric analysis and cell sorting of phytoplankton populations. Notwithstanding, significant algae autofluorescence originating from different types of chlorophyll and accessory pigments may overlap with propidium iodide and/or eosin staining and affect the resolution of algae clusters and cell sorting

Preparation of anti-vicinal amino alcohols: asymmetric synthesis of D-erythro-Sphinganine, (+)-spisulosine and D-ribo-phytosphingosine

Two variations of the Overman rearrangement have been developed for the highly selective synthesis of anti-vicinal amino alcohol natural products. A MOM-ether directed palladium(II)-catalyzed rearrangement of an allylic trichloroacetimidate was used as the key step for the preparation of the protein kinase C inhibitor D-erythro-sphinganine and the antitumor agent (+)-spisulosine, while the Overman rearrangement of chiral allylic trichloroacetimidates generated by asymmetric reduction of an alpha,beta-unsaturated methyl ketone allowed rapid access to both D-ribo-phytosphingosine and L-arabino-phytosphingosine

Horizontal Gene Acquisitions, Mobile Element Proliferation, and Genome Decay in the Host-Restricted Plant Pathogen \u3ci\u3eErwinia Tracheiphila\u3c/i\u3e

Modern industrial agriculture depends on high-density cultivation of genetically similar crop plants, creating favorable conditions for the emergence of novel pathogens with increased fitness in managed compared with ecologically intact settings. Here, we present the genome sequence of six strains of the cucurbit bacterial wilt pathogen Erwinia tracheiphila (Enterobacteriaceae) isolated from infected squash plants in New York, Pennsylvania, Kentucky, and Michigan. These genomes exhibit a high proportion of recent horizontal gene acquisitions, invasion and remarkable amplification of mobile genetic elements, and pseudogenization of approximately 20% of the coding sequences. These genome attributes indicate that E. tracheiphila recently emerged as a host-restricted pathogen. Furthermore, chromosomal rearrangements associated with phage and transposable element proliferation contribute to substantial differences in gene content and genetic architecture between the six E. tracheiphila strains and other Erwinia species. Together, these data lead us to hypothesize that E. tracheiphila has undergone recent evolution through both genome decay (pseudogenization) and genome expansion (horizontal gene transfer and mobile element amplification). Despite evidence of dramatic genomic changes, the six strains are genetically monomorphic, suggesting a recent population bottleneck and emergence into E. tracheiphila’s current ecological niche

D-Amino Acids Indirectly Inhibit Biofilm Formation in Bacillus subtilis by Interfering with Protein Synthesis

The soil bacterium Bacillus subtilis forms biofilms on surfaces and at air-liquid interfaces. It was previously reported that these biofilms disassemble late in their life cycle and that conditioned medium from late-stage biofilms inhibits biofilm formation. Such medium contained a mixture of d-leucine, d-methionine, d-tryptophan, and d-tyrosine and was reported to inhibit biofilm formation via the incorporation of these d-amino acids into the cell wall. Here, we show that l-amino acids were able to specifically reverse the inhibitory effects of their cognate d-amino acids. We also show that d-amino acids inhibited growth and the expression of biofilm matrix genes at concentrations that inhibit biofilm formation. Finally, we report that the strain routinely used to study biofilm formation has a mutation in the gene (dtd) encoding d-tyrosyl-tRNA deacylase, an enzyme that prevents the misincorporation of d-amino acids into protein in B. subtilis. When we repaired the dtd gene, B. subtilis became resistant to the biofilm-inhibitory effects of d-amino acids without losing the ability to incorporate at least one noncanonical d-amino acid, d-tryptophan, into the peptidoglycan peptide side chain. We conclude that the susceptibility of B. subtilis to the biofilm-inhibitory effects of d-amino acids is largely, if not entirely, due to their toxic effects on protein synthesis.Chemistry and Chemical Biolog

Cytological and transcript analyses reveal fat and lazy persister-like bacilli in tuberculous sputum

As nonreplicating tubercle bacilli are tolerant to the cidal action of antibiotics and resistant to multiple stresses, identification of this persister-like population of tubercle bacilli in sputum presents exciting and tractable new opportunities to investigate both responses to chemotherapy and the transmission of tuberculosis