The biogenesis protein PEX14 is an optimal marker for the identification and localization of peroxisomes in different cell types, tissues, and species in morphological studies

Catalase and ABCD3 are frequently used as markers for the localization of peroxisomes in morphological experiments. Their abundance, however, is highly dependent on metabolic demands, reducing the validity of analyses of peroxisomal abundance and distribution based solely on these proteins. We therefore attempted to find a protein which can be used as an optimal marker for peroxisomes in a variety of species, tissues, cell types and also experimental designs, independently of peroxisomal metabolism. We found that the biogenesis protein peroxin 14 (PEX14) is present in comparable amounts in the membranes of every peroxisome and is optimally suited for immunoblotting, immunohistochemistry, immunofluorescence, and immunoelectron microscopy. Using antibodies against PEX14, we could visualize peroxisomes with almost undetectable catalase content in various mammalian tissue sections (submandibular and adrenal gland, kidney, testis, ovary, brain, and pancreas from mouse, cat, baboon, and human) and cell cultures (primary cells and cell lines). Peroxisome labeling with catalase often showed a similar tissue distribution to the mitochondrial enzyme mitochondrial superoxide dismutase (both responsible for the degradation of reactive oxygen species), whereas ABCD3 exhibited a distinct labeling only in cells involved in lipid metabolism. We increased the sensitivity of our methods by using QuantumDots?, which have higher emission yields compared to classic fluorochromes and are unsusceptible to photobleaching, thereby allowing more exact quantification without artificial mistakes due to heterogeneity of individual peroxisomes. We conclude that PEX14 is indeed the best marker for labeling of peroxisomes in a variety of tissues and cell types in a consistent fashion for comparative morphometry.     

Microbial utilization of coral mucus in long term in situ incubation over a coral reef

The purpose of this study was to assess degradation and utilization of the mucus produced by 3 coral reef Anthozoa (Sarcophyton, Fungia and Acropora) by microorganisms. This was achieved by carrying out long term in situ incubations at Nouméa lagoon (New Caledonia).The microbial population including bacterial and eukaryotic cells was monitored by cell counts, cultures of mucus degraders, and by estimation of microbial activity from the pool of adenylates and enzymatic activity. In addition the chemical composition (C and N) of the mucus was monitored and its morphological features were observed by scanning electron microscope (SEM).Only slight differences were found between the 3 types of mucus studied. On the whole, they follow the same pattern of change. After a short bacterial growth phase (4 days), a bloom of eukaryotes (Flagellates, Ciliates and Diatoms) was observed. This eukaryote population remained constant for at least 10 days. A similar pattern has been described in the breakdown of detritus of plant origin.Several observations suggest that bacteria utilize only certain components of mucus, the most widely used being proteins, triglycerides and wax esters; these latter two compounds are known to be the dissolved photosynthetic products released by zooxanthellae during mucus secretion. Neither bacteria nor eukaryotes completely degrade the mucus web even after 21 days of incubation. The likelihood that mucus excretion is a defensive reaction against physical and chemical stresses might explain why mucus is a poor, or even inhibiting medium for the bacterial degraders isolated from the mucus itself.