Carbon pools and isotopic trends in a hypersaline cyanobacterial mat.

The fine-scale depth distribution of major carbon pools and their stable carbon isotopic signatures (delta(13)C) were determined in a cyanobacterial mat (Salin-de-Giraud, Camargue, France) to study early diagenetic alterations and the carbon preservation potential in hypersaline mat ecosystems. Particular emphasis was placed on the geochemical role of extracellular polymeric substances (EPS). Total carbon (C(tot)), organic carbon (C(org)), total nitrogen (N(tot)), total hydrolysable amino acids (THAA), carbohydrates, cyanobacteria-derived hydrocarbons (8-methylhexadecane, n-heptadec-5-ene, n-heptadecane) and EPS showed highest concentrations in the top millimetre of the mat and decreased with depth. The hydrocarbons attributed to cyanobacteria showed the strongest decrease in concentration with depth. This correlated well with the depth profiles of oxygenic photosynthesis and oxygen, which were detected in the top 0.6 and 1.05 mm, respectively, at a high down-welling irradiance (1441 micromol photons m(-2) s(-1)). At depths beneath the surface layer, the C(org) was composed mainly of amino acids and carbohydrates. A resistance towards microbial degradation could have resulted from interactions with diverse functional groups present in biopolymers (EPS) and with minerals deposited in the mat. A (13)C enrichment with depth for the total carbon pool (C(tot)) was observed, with delta(13)C values ranging from -16.3 per thousand at the surface to -11.3 per thousand at 9-10 mm depth. Total lipids depicted a delta(13)C value of -17.2 per thousand in the top millimetre and then became depleted in (13)C with depth (-21.7 to -23.3 per thousand). The delta(13)C value of EPS varied only slightly with depth (-16.1 to -17.3 per thousand) and closely followed the delta(13)C value of C(org) at depths beneath 4 mm. The EPS represents an organic carbon pool of preservation potential during early stages of diagenesis in recent cyanobacterial mats as a result of a variety of possible interactions. Their analyses might improve our understanding of fossilized microbial remains from mat ecosystems.

Ultrabroadband chirped mirrors for femtosecond lasers.

We report on the performance of widely tunable femtosecond and continuous-wave Ti:sapphire lasers that use a newly developed ultrabroadband mirror set. The mirrors exhibit high reflectivity (R > 99%) and smooth variation of group delay versus frequency over a wavelength range from 660 to 1060 nm. Mode-locked operation with pulse durations of 85 fs was achieved from 693 to 978 nm with only one set of ultrabroadband mirrors.

Differential distribution of the mitochondrial heat-shock protein 60 in rat gastrointestinal tract.

Immunohistochemical studies on various parts of the rat gastrointestinal tract by means of an antibody against the mitochondrial chaperonin, heat-shock protein 60 (hsp60), has revealed a cell-specific distribution pattern. The active form of hsp60 is a heptameric complex that is involved in the import and refolding of nuclear-encoded proteins destined for the mitochondrial matrix. This chaperonin is detectable in highly replicating cells, e. g., keratinizing cells of the esophagus and short-living epithelial cells of the intestine. In the stomach, some of the oxyntic cells contain hsp60-positive mitochondria lying near intracellular canaliculi. Neuronal cells of the enteric nervous system present intense positive staining for hsp60 in some areas. All other non-epithelial cells of the digestive tract show weak or no hsp60 immunoreactivity. The presence of hsp60 in mitochondria seems to reflect two different forms of mitochondrial renewal: (1) total reformation of mitochondria and their content after mitotic division and (2) regeneration of these organelles following high activity, e. g., ATP synthesis.

Mitochondrial differentiation during meiosis of male germ cells.

In male germ cells mitochondria undergo dramatic morphological changes during spermatogenesis, at least three different types of mitochondrion being present. The usual cristae type of mitochondrion in spermatogonia, preleptotene and leptotene spermatocytes develops, via an intermediate form in zygotene spermatocytes, to the condensed form with almost no cristae which is typical of pachytene spermatocytes and early spermatids. In cell culture experiments in which isolated preparations of meiotic germ cells were used, it was shown that condensed mitochondria in pachytene spermatocytes cultured in Earle's minimal essential medium dedifferentiated to the intermediate type, while Sertoli cell-conditioned medium (SC-CM) was able to maintain the condensed structure. SC-CM was also able to induce conversion of the intermediate type to the condensed type in isolated zygotene spermatocytes. Preliminary biochemical characterization showed the involvement of one or several proteinaceous factors > 10 kDa (PMMF: paracrine mitochondria maturation factor) that were protease (subtilisin)- and heat-sensitive. Three mitochondrial proteins served as markers for germ cells in different phases of maturation. The chaperonin hsp60 was detectable in the orthodox-type mitochondria of spermatogonia and primary spermatocytes (leptotene and zygotene). An ATP- dependent mitochondrial matrix enzyme -- the Lon-protease -- appeared in the orthodox and intermediate forms of mitochondria in leptotene and zygotene spermatocytes. Sulphydryl oxidase is present in the condensed mitochondria of pachytene spermatocytes and early spermatids.