Cellulose and lignin degradation in forest soils: Response to moisture,temperature, and acidity

The concentration of lignin in plant tissue is a major factor controlling organic matter degradation rates in forest ecosystems. Microbial biomass and lignin and cellulose decomposition were measured for six weeks in forest soil microcosms in order to determine the influence of pH, moisture, and temperature on organic matter decomposition. Microbial biomass was determined by chloroform fumigation; lignin and cellulose decomposition were measured radiometrically. The experiment was designed as a Latin square with soils of pH of 4.5, 5.5, and 6.5 adjusted to 20, 40, or 60% moisture content, and incubated at temperatures of 4, 12, or 24°C. Microbial biomass and lignin and cellulose decomposition were not significantly affected by soil acidity. Microbial biomass was greater at higher soil moisture contents. Lignin and cellulose decomposition significantly increased at higher soil temperatures and moisture contents. Soil moisture was more important in affecting microbial biomass than either soil temperature or soil pH.     

Ethylene receptor expression is regulated during fruit ripening, flower senescence and abscission

Using theArabidopsis ethylene receptorETR1 as a probe, we have isolated a tomato homologue (tETR) from a ripening cDNA library. The predicted amino acid sequence is 70% identical toETR1 and homologous to a variety of bacterial two component response regulators over the histidine kinase domain. Sequencing of four separate cDNAs indicates that tETR lacks the carboxyl terminal response domain and is identical to that encoded by the tomatoNever ripe gene. Ribonuclease protection showed tETR mRNA was undetectable in unripe fruit or pre-senescent flowers, increased in abundance during the early stages of ripening, flower senescence, and in abscission zones, and was greatly reduced in fruit of ripening mutants deficient in ethylene synthesis or response. These results suggest that changes in ethylene sensitivity are mediated by modulation of receptor levels during development.     

Characterization of Inorganic Biocarriers That Moderate System Upsets during Fixed-Film Biotreatment Processes

Inorganic matrices were developed for fixed-film bioreactors affording protection to microorganisms and preventing loss of bioreactor productivity during system upsets. These biocarriers, designated Type-Z, contain ion-exchange properties and possess high porosity and a high level of surface area, which provide a suitable medium for microbial colonization. Viable cell populations of 10⁹/g were attainable, and scanning electron micrographs revealed extensive external colonization and moderate internal colonization with aerobic microorganisms. Laboratory-scale bioreactors were established with various biocarriers and colonized with Pseudomonas aeruginosa, and comparative studies were performed. The data indicated that bioreactors containing the Type-Z biocarriers were more proficient at removing phenol (1,000 ppm) than bioreactors established with Flexirings (plastic) and Celite R635 (diatomaceous earth) biocarriers. More significantly, these biocarriers were shown to moderate system upsets that affect operation of full-scale biotreatment processes. For example, subjecting the Type-Z bioreactor to an influent phenol feed at pH 2 for periods of 24 h did not decrease the effluent pH or reactor performance. In contrast, bioreactors containing either Celite or Flexirings demonstrated an effluent pH drop to ~2.5 and a reduction in reactor performance by 75 to 82%. The Celite reactor recovered after 5 days, whereas the bioreactors containing Flexirings did not recover. Similar advantages were noted during either nutrient or oxygen deprivation experiments as well as alkali and organic system shocks. The available data suggest that Type-Z biocarriers represent an immobilization medium that provides an amenable environment for microbial growth and has the potential for improving the reliability of fixed-film biotreatment processes.     

Nucleotide sequence and expression of a ripening and water stress-related cDNA from tomato with homology to the MIP class of membrane channel proteins

The nucleotide sequence and derived amino acid sequence were determined for a full-length version of the tomato cDNA clone, pTOM75, the mRNA for which has previously been shown to accumulate in roots, ripening fruit and senescing leaves. Computer analysis of the predicted protein product, which we have named tomato ripening-associated membrane protein (TRAMP) indicates strong homology to known transmembrane channel proteins from other organisms. Northern analysis showed that this gene was induced by waterstress and that this induction was unaffected in an ABA-deficient genetic back-ground.     

Reclassification of Thiobacillus thyasiris as Thiomicrospira thyasirae comb. nov., an organism exhibiting pleomorphism in response to environmental conditions

The halotolerant, facultatively chemolithoautotrophic, gramnegative sulphur-oxidizing organism isolated from the gills of Thyasira flexuosa is shown to exhibit pleomorphism consistent with its being a member of the genus Thiomicrospira and not a Thiobacillus as originally classified. Its distinctive morphology, DNA base composition, and similarity of 16S rRNA sequences to that of Thiomicrospira sp. strain L-12 (which differs only in detail from the type species Thiomicrospira pelophila), lead us to reclassify this strain as Thiomicrospira thyasirae DSM5322.     

THE NORMAL FINE STRUCTURE OF OPOSSUM TESTICULAR INTERSTITIAL CELLS

The interstitial tissue of the opossum testis includes interstitial or Leydig cells, macrophages, and small cells which morphologically resemble mesenchymal cells. The latter are thought to give rise to mature interstitial cells. The most prominent feature of the interstitial cell cytoplasm is an exceedingly abundant agranular endoplasmic reticulum. This reticulum is generally in the form of a meshwork of interconnected tubules about 300 to 450 A in diameter, but occasionally it assumes the form of flattened, fenestrated cisternae resembling those of pancreatic acinar cells, except for the lack of ribonucleoprotein particles on the surface of the membranes. The interstitial cells vary considerably in their cytoplasmic density. The majority are quite light, but some appear extremely dense, and in addition usually have a more irregular cell surface, with numerous small pseudopodia. These differences may well reflect variations in physiological state. Cytoplasmic structures previously interpreted as "crystalloids" consist of long bundles of minute parallel tubules, each about 180 A in diameter, which seem to be local differentiations of the endoplasmic reticulum. The mitochondria are rod-shaped, and contain a moderately complex internal membrane structure, and also occasional large inclusions that are spherical and homogeneous. The prominent juxtanuclear Golgi complex contains closely packed flattened sacs and small vesicles. The results of the present study, coupled with biochemical evidence from other laboratories, make it seem highly probable that the agranular endoplasmic reticulum is involved in the synthesis of the steroid hormones produced by the interstitial cell. This finding therefore constitutes one of the first functions of the agranular reticulum for which there is good morphological and biochemical evidence.     

Effects of wall shear stress and fluid recirculation on the localization of circulating monocytes in a three-dimensional flow model

There is a correlation between the location of early atherosclerotic lesions and the hemodynamic characteristics at those sites. Circulating monocytes are key cells in the pathogenesis of atherosclerotic plaques and localize at sites of atherogenesis. The hypothesis that the distribution of monocyte adhesion to the vascular wall is determined in part by hemodynamic factors was addressed by studying monocyte adhesion in an in vitro flow model in the absence of any biological activity in the model wall.

Suspensions of U937 cells were perfused (Re = 200) through an axisymmetric silicone flow model with a stenosis followed by a reverse step. The model provided spatially varying wall shear stress, flow separation and reattachment, and a three-dimensional flow pattern. The cell rolling velocity and adhesion rates were determined by analysis of videomicrographs. Wall shear stress was obtained by numerical solution of the equations of fluid motion. Cell adhesion patterns were also studied in the presence of chemotactic peptide gradients.

The cell rolling velocity varied linearly with wall shear stress. The adhesion rate tended to decrease with increasing local wall shear stress, but was also affected by the radial component of velocity and the dynamics of the recirculation region and flow reattachment. Adhesion was increased in the vicinity of chemotactic peptide sources downstream of the expansion site. Results with human monocytes were qualitatively similar to the U937 experiments.

Differences in the adhesion rates of U937 cells occurring solely as a function of the fluid dynamic properties of the flow field were clearly demonstrated in the absence of any biological activity in the model wall.