The inhibition of chlorophyll formation in Euglena by antibiotics which inhibit bacterial and mitochondrial protein synthesis

Metabolic Responses of a Model Green Microalga Euglena gracilis to Different Environmental Stresses

Euglena gracilis, a green microalga known as a potential candidate for jet fuel producers and new functional food resources, is highly tolerant to antibiotics, heavy metals, and other environmental stresses. Its cells contain many high-value products, including vitamins, amino acids, pigments, unsaturated fatty acids, and carbohydrate paramylon as metabolites, which change contents in response to various extracellular environments. However, mechanism insights into the cellular metabolic response of Euglena to different toxic chemicals and adverse environmental stresses were very limited. We extensively investigated the changes of cell biomass, pigments, lipids, and paramylon of E. gracilis under several environmental stresses, such as heavy metal CdCl₂, antibiotics paromomycin, and nutrient deprivation. In addition, global metabolomics by Ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was applied to study other metabolites and potential regulatory mechanisms behind the differential accumulation of major high-valued metabolites. This study collects a comprehensive update on the biology of E. gracilis for various metabolic responses to stress conditions, and it will be of great value for Euglena cultivation and high-value [154mm][10mm]Q7metabolite production.

The effect of glucose on the biochemical and ultrastructural characteristics of developing Euglena chloroplasts

Chloroplast development is inhibited in Euglena gracilis strain Z, when greened in a medium containing glucose. This inhibition is reflected not only in the pattern of chlorophyll accumulation but also in the chloroplast ultrastructure and activities of the 2 light reactions of photosynthesis. Chloroplasts of cells greening in the presence of glucose are delayed in developing certain structures. Photosystem I activity develops at about the same rate as that of the controls during the first 48 h of greening, after which it develops at a slower rate. The rate of development of photosystem II activity in cells greening in a glucose medium lags considerably behing that of the controls until the later hours of greening. There are similarities between glucose inhibition and chloramphenicol inhibition of chloroplast development. Glucose may inhibit a step in chloroplast development ultimately controlled by the chloroplast genome.

The effects of inhibitors of RNA and protein synthesis on chloroplast structure and function in wild-type Chlamydomonas reinhardi

Wild-type cells of the unicellular green alga Chlamydomonas reinhardi have been grown for several generations in the presence of rifampicin, an inhibitor of chloroplast DNA-dependent RNA polymerase, spectinomycin and chloramphenicol, two inhibitors of protein synthesis on chloroplast ribosomes, and cycloheximide, an inhibitor of protein synthesis on cytoplasmic ribosomes. The effects of cycloheximide are complex, and it is concluded that this inhibitor cannot give meaningful information about the cytoplasmic control over the synthesis of chloroplast components in long-term experiments with C. reinhardi. In the presence of acetate and at the appropriate concentrations, the three inhibitors of chloroplast protein synthesis retard growth rates only slightly and do not affect the synthesis of chlorophyll; however, photosynthetic rates are reduced fourfold after several generations of growth. Each inhibitor produces a similar pattern of lesions in the organization of chloroplast membranes. Only rifampicin prevents the production of chloroplast ribosomes.

Haem synthesis during mitochondrogenesis in yeast

The activities of delta-aminolaevulate synthetase and delta-aminolaevulate dehydratase have been assayed in Saccharomyces cerevisiae during glucose repression and de-repression. delta-Aminolaevulate dehydratase increased concomitantly with the increase in oxygen uptake during the de-repression phase caused by the depletion of glucose in the medium. delta-Aminolaevulate synthetase showed an oscillatory behaviour and a spurt in its activity always preceded the increase in oxygen uptake. The activity of both the enzymes was lowered if the cells were incubated with glucose or cycloheximide, but not with chloramphenicol.

Studies on senescing tobacco leaf disks with special reference to peroxidase : I. The effects of cutting, and of inhibition of nucleic-acid and protein synthesis

1. Disks of tobacco leaf were incubated on water in darkness at 25°. Diagonal cutting of disks had no significant effects on chlorophyll decrease, α-amino nitrogen increase or acid phosphatase increase. Cutting slightly stimulated protein decrease, stimulated peroxidase increase and inhibited catalase decrease. The central areas of larger disks only differed from the control disks in decreased chlorophyll disappearance and peroxidase synthesis. 2. Peroxidase extracts showed some latent activity when treated with Triton X-100, 2,4-dichlorophenol or frozen and thawed. This was insufficient to account for the marked stimulation of synthesis in senescing disks. There was no evidence for cytoplasmic inhibitors of peroxidase. 3. Biochemical differences between chlorotic and green areas of detached, senescing leaves were compared with differences between freshly cut (green) and senescing (chlorotic) leaf disks. 4. Studies with actinomycin D, chloramphenicol, puromycin and actidione suggest that these compounds inhibit the synthesis of some proteins in senescing disks more effectively than others. 5. The differences between disks cut from mature and young leaves were studied.