A deep sleep in coal beds Deep below the ocean floor, microorganisms from forest soils continue to thrive. Inagaki et al. analyzed the microbial communities in several drill cores off the coast of Japan, some sampling more than 2 km below the seafloor (see the Perspective by Huber). Although cell counts decreased with depth, deep coal beds harbored active communities of methanogenic bacteria. These communities were more similar to those found in forest soils than in other deep marine sediments. Science , this issue p. 420 ; see also p. 376

Microbial life in marine sediment contributes substantially to global biomass and is a crucial component of the Earth system. Subseafloor sediment includes both aerobic and anaerobic microbial ecosystems, which persist on very low fluxes of bioavailable energy over geologic time. However, the taxonomic diversity of the marine sedimentary microbial biome and the spatial distribution of that diversity have been poorly constrained on a global scale. We investigated 299 globally distributed sediment core samples from 40 different sites at depths of 0.1 to 678 m below the seafloor. We obtained ∼47 million 16S ribosomal RNA (rRNA) gene sequences using consistent clean subsampling and experimental procedures, which enabled accurate and unbiased comparison of all samples. Statistical analysis reveals significant correlations between taxonomic composition, sedimentary organic carbon concentration, and presence or absence of dissolved oxygen. Extrapolation with two fitted species–area relationship models indicates taxonomic richness in marine sediment to be 7.85 × 103 to 6.10 × 105 and 3.28 × 104 to 2.46 × 106 amplicon sequence variants for Archaea and Bacteria, respectively. This richness is comparable to the richness in topsoil and the richness in seawater, indicating that Bacteria are more diverse than Archaea in Earth’s global biosphere.

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Summary.The taste buds of rat circumvallate papillae contain three distinct types of cells. The type I (dark) cell is characterized by the presence of dense round granules, which are precursor to the dense substance of the taste pore. The granules are discharged into the pore by exocytosis.The type II (light) cell is filled with numerous vesicles and smooth-surfaced endoplasmic reticulum. The type III cell contains in its basal cytoplasm characteristic dark-cored vesicles and masses of clear vesicles, and makes synapse-like contacts with nerve fibers.The fine structure of foliate buds corresponds to that of circumvallate papillae, while fungiform buds differ in their apical regions.In the latter the pore is filled with vesicles alone, and the type I cell contains rod-shaped granules of moderate density.When polysaccharides were examined by means of the periodic acid-silver methenamine and the periodic acid-thiocarbohydrazide methods, slightly positive reactions were found on the dense granules of the type I cell and the dense substance in the pore, whereas the membranes of the pore vesicles, apical cytoplasmic processes and cytoplasmic vesicles in type II cells showed intense reactions.The ultrastructure of the mammalian taste buds was previously studied in rabbits (ENGSTROM and RYTZNER, 1956;TRUJILLO-CENOZ, 1957;DE LORENZO, 1958;NEMETSCHEK-GANSLER and FERNER, 1964;SCALZI, 1967;MURRAY and MURRAY, 1967; MURRAY, MURRAY and FUJIMOTO, 1969;FUJIMOTO and MURRAY, 1970), rats (GRAY and WATKINS, 1965; FARBMAN, 1965a, b;UGA, 1969), guinea pigs (SPOENDLIN, 1970), monkeys (MURRAY and MURRAY, 1960), and men (GRAZIADEI, 1969;MATTHEWS and MARTIN, 1971;TAKEDA, 1972). These studies have shown disagreement with regard to their cellular composition and the function of the individual cells. In particular, it remains to be established what cell type should be designated as the gustatory receptor. FARBMAN (1965a, b) distinguished the taste buds in rat fungiform papillae into four cell types which were called the peripheral, basal, type I (dark) and type II (light) cells. He considered the type I cell as the gustatory receptor.On the other hand, UGA (1969) who examined the rat circumvallate papillae, divided taste bud cells into two types, the light cells and the dark cells. He regarded the light cells as the gustatory element which is synaptically in contact with nerves. MURRAY, MURRAY and FUJIMOTO (1969) reported the third cell type in addition to the dark and the light ones. The cells of this type contained an aggregation of vesicles of a type generally found in synaptic regions in the basal portion of the cytoplasm, and they regarded this type as a gustatory receptor.The three primary areas of the tongue in mammals where the taste buds are commonly found are those of the circumvallate, foliate and fungiform papillae. In the rat tongue, the fungiform papillae are innervated by the chorda tympani nerve, whereas the circumvallate papillae and the posterior folds of the foliate papillae are 395