Properties of selectively starved euglena

Euglena gracilis Genome and Transcriptome: Organelles, Nuclear Genome Assembly Strategies and Initial Features

Euglena gracilis is a major component of the aquatic ecosystem and together with closely related species, is ubiquitous worldwide. Euglenoids are an important group of protists, possessing a secondarily acquired plastid and are relatives to the Kinetoplastidae, which themselves have global impact as disease agents. To understand the biology of E. gracilis, as well as to provide further insight into the evolution and origins of the Kinetoplastidae, we embarked on sequencing the nuclear genome; the plastid and mitochondrial genomes are already in the public domain. Earlier studies suggested an extensive nuclear DNA content, with likely a high degree of repetitive sequence, together with significant extrachromosomal elements. To produce a list of coding sequences we have combined transcriptome data from both published and new sources, as well as embarked on de novo sequencing using a combination of 454, Illumina paired end libraries and long PacBio reads. Preliminary analysis suggests a surprisingly large genome approaching 2 Gbp, with a highly fragmented architecture and extensive repeat composition. Over 80% of the RNAseq reads from E. gracilis maps to the assembled genome sequence, which is comparable with the well assembled genomes of T. brucei and T. cruzi. In order to achieve this level of assembly we employed multiple informatics pipelines, which are discussed here. Finally, as a preliminary view of the genome architecture, we discuss the tubulin and calmodulin genes, which highlight potential novel splicing mechanisms.

Ultraviolet inactivation of Euglena chloroplasts. I. Effect of light intensity of culture

Target numbers for ultraviolet (UV) inactivation of chloroplast replication in Euglena gracilis were about 45 when cells were grown in the dark and about 150 when grown in the light (700 or 1200 foot-candles [ft-cd]). Total cell DNA was about 25% greater in the light-grown cells.

Studies on chloroplast development and replication in Euglena. I. Vitamin B12 and chloroplast replication

When Euglena gracilis is grown under vitamin B(12) deficiency conditions, the amount of protein and of chlorophyll per cell increase with decrease of B(12) in the medium and consequently in the cell. The increase in cell protein is proportional to and precedes an increase in the number of chloroplasts per cell. This replication of the chloroplasts under deficiency conditions is not accompanied by nuclear or cell division. It is concluded that chloroplast replication in Euglena gracilis is independent of nuclear and cellular replication, at least under B(12) deficiency conditions. We established a graph of the growth of Euglena under different concentrations of vitamin B(12) added to the growth medium, which permitted us to calculate that at least 22,000 molecules of vitamin B(12) per cell are required to give normal growth.