Bacteria associated with a marine planktonic copepod in culture. II. Degradation of fecal pellets produced on a diatom, a nanoflagellate or a dinoflagellate diet

Copepods (A cartia tonsa Dana) were allowed to feed on culturedalgal species simulating the yearly boreal phytoplankton succession,where the spring is characterized by diatoms, the summer bynanoflagellates and the autumn by dinoflagellates. Degradationof freshly produced fecal pellets in suspension was followedover time by volume recording and estimation of carbon loss.The fecal pellets produced on a diatom diet were very denseand showed a significantly slower degradation than those producedon nanoflagellate or dinoflagellate diets. This indicates thatthe algal texture, i.e. the mechanical robustness given by inertstructures, determines the degradation rate of the pellets.The degradation rate was also very dependent on the algal concentrationfor the grazer (565 µg Cl^–1 T₁     

Bacterial flora in the digestive tract of cattle. I. Comparison of nonselective culture medium and changes in fecal bacterial flora with age.

Studies were made on nonselective culture medium and the method of culture for the investigation of the bacterial flora in the digestive tract of cattle. With their results, further studies were done to clarify changes in the fecal bacterial flora in eight calves less than 6 months of age with the lapse of time. Three roll-tube media were used in the gas jet method. They were modified VL agar (VL medium), rumen fluid glucose cellobiose agar (RGCA medium), and Medium 10 (M 10). Moreover, glucose liver blood agar (BL medium) was used in the anaerobic jar method. In this method the steel wool method was applied after the substitution of carbon dioxide. Of the four media used, VL medium was proved to be the most efficient. It was followed by RGCA medium and M 10. BL medium was much less efficient than any other medium. When the fecal bacterial flora was examined in calves for changes with the advance in age, the total bacterial count and the enteric bacterial count decreased in the second half of the experimental period. The lactobacillary group count remained almost at a constant level of 7 approximately 9 (logarithmic value) per gram in breast-fed calves, but decreased to a level of 5 (logarithmic value) per gram in bottle-fed calves at about 2 months of age or later. The streptococcal group count showed no particular tendency to change. When the organic acid contents of the feces were estimated in calves in every stage of growth, the amount of total organic acids and that of propionic acid were larger in bottle-fed than in breast-fed calves.     

Compartments in a marine food web associated with phylogeny, body mass, and habitat structure

A long-standing question in community ecology is whether food webs are organized in compartments, where species within the same compartment interact frequently among themselves, but show fewer interactions with species from other compartments. Finding evidence for this community organization is important since compartmentalization may strongly affect food web robustness to perturbation. However, few studies have found unequivocal evidence of compartments, and none has quantified the suite of mechanisms generating such a structure. Here, we combine computational tools from the physics of complex networks with phylogenetic statistical methods to show that a large marine food web is organized in compartments, and that body size, phylogeny, and spatial structure are jointly associated with such a compartmentalized structure. Sharks account for the majority of predatory interactions within their compartments. Phylogenetically closely related shark species tend to occupy different compartments and have divergent trophic levels, suggesting that competition may play an important role structuring some of these compartments. Current overfishing of sharks has the potential to change the structural properties, which might eventually affect the stability of the food web.     

Abundance,succession and morphological variation of planktonic rotifers during autumnal circulation in a hypertrophic lake (Heiligensee,Berlin)

Quantitative samples were taken in the pelagial zone of hypertrophic Heiligensee (Berlin, Germany) in the late summer and autumn of 1990. Abundances of 26 species occurring in the plankton, as well as physical and chemical parameters (water temperature, O₂, total phosphorus, SRP, NO₃ ^–, NO₂ ^– NH₄ ⁺ , chlorophyll a) were determined at different depths. Erosion of the hypolimnion due to autumnal storms and decrease in temperature was interrupted by fine weather periods with the occurrence of re-stratification, thus allowing mass production of algae and rotifers (Synchaeta oblonga, S. tremula, Keratella cochlearis) through exploitation of newly available nutrients. Warm stenothermal summer species (e.g. Pompholyx sulcata, Trichocerca pusilla, Liliferotrocha subtilis) became less abundant as a consequence of the progressive mixing process, whereas the appearance of new species was a rare event. The late summer occurrence of Liliferotrocha subtilis in the fraction < 30 µm (up to 3500 ind. l^–1) is remarkable. Keratella cochlearis showed morphological variation from spineless summer forms to spine-bearing autumnal forms, the latter particularly dominating the deeper water layers. The prevailing phenomenon was the dramatic decrease of the total number of individuals and of species towards completion of autumnal turnover. The impact of falling temperature, increasing mixing depth and mass production of phytoplankton on the rotifer plankton community is discussed.     

Periodicity in cell division and physiological behavior of ditylum brightwellii,a marine planktonic diatom,during growth in light-dark cycles

Summary Cells of Ditylum brightwellii, a large marine centric diatom, were partially synchronized by employing an appropriate light-dark cycle. At 20°C this consisted of 8 hrs of illumination at an intensity of 0.05 cal/cm² min. A single 2.8 l culture was studied over a 20 day period by diluting the culture daily to a standard cell concentration. The sequence of events in cell development was as follows: daughter cells were formed late in the light period, in the dark they elongated and the numerous chromatophores began dividing. A minimum cell buoyancy was observed in the dark concurrent with cell elongation. Increase in cell phosphorus took place in the dark period. The photosynthetic rate of cells removed during the dark period decreased to a minimum. In the following light period photosynthetic rate increased to a maximum, photosynthetic pigments, cell carbon, nitrogen, and carbohydrate increased and cell division again took place. Cell silica content increased concomitant with cell division. Details of cell morphology during cell division, based upon light microscopy, are reported.Contribution of the Scripps Institution of Oceanography.     

Free-living marine nematodes of shrimp culture ponds in Thailand. I. New species of the genera Diplolaimella and Thalassomonhystera (Monhysteridae) and Theristus (Xyalidae)

Three new species belonging to the genera Diplolaimella and Thalassomonhystera of the family Monhysteridae and Theristus of the family Xyalidae are described from shrimp culture ponds near mangrove zones of Khung Kraben Bay, Thailand. Diplolaimella thailandica sp. n. resembles D. dievengatensis but differs from it by features of the ratios b and V, and size of the spicules and tail of the male. Thalassomonhystera siamensis sp. n. resembles T. diplops but differs from it in features of the amphids, ocelli, cloaca and gubernaculum. Theristus (Penzancia) longisetifer sp. n. resembles T. flevensis, T. ambronensis, T. macroflevensis, and T. pratti but differs from them in features of the cervical setae, ventral supplement of the male and others. This revised version was published online in July 2006 with corrections to the Cover Date.     

RNase I*, a form of RNase I, and mRNA degradation in Escherichia coli.

A previously unreported endoRNase present in the spheroplast fraction of Escherichia coli degraded homoribopolymers and small RNA oligonucleotides but not polymer RNA. Like the periplasmic endoRNase, RNase I, the enzyme cleaved the phosphodiester bond between any nucleotides; however, RNase I degraded polymer RNA as fast as homopolymers or oligomers. Both enzymes migrated as 27-kDa polypeptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and could not be separated by various chromatographic procedures. In rna insertion mutants, both enzymes were completely missing; the spheroplast enzyme is called RNase I*, since it must be a form of RNase I. The two forms could be distinguished by physical treatments. RNase I could be activated by Zn2+, while RNase I* was inactive in the presence of Zn2+. RNase I was inactivated very slowly at 100 degrees C over a wide pH range, while RNase I* was inactivated slowly by heat at pH 4.0 but much more rapidly as the pH was increased to 8.0. In the presence of a thiol-binding agent, the inactivation at the higher pH values was much slower. These results suggest that RNase I*, but not RNase I, has free sulfhydryl groups. RNase I* activity in the cell against a common substrate was estimated to be several times that of RNase I. All four 2',3'-phosphomonoribonucleotides were identified in the soluble pools of growing cells. Such degradative products must arise from RNase I* activity. The activity would be suited for the terminal step in mRNA degradation, the elimination of the final oligonucleotide fragments, without jeopardizing the cell RNA. An enzyme with very similar specificity was found in Saccharomyces cerevisiae, suggesting that the activity may be widespread in nature.     

Significance of low-temperature growth associated with the fecal coliform response, indole production, and pectin liquefaction in Klebsiella.

In the genus Klebsiella, the growth respnse in nutient broth at 10 degrees C correlates inversely with the operational definition of a fecal coliform and not merely with the ability to grow at 44.5 degrees C. Of the fecal coliform-positive Klebsiella, 97% did not grow at 10 degrees C after 72 h of incubation. Conversely, 97% of the fecal coliform-negative isolates grew at 10 degrees C. The amount of growth at 10 degrees C varied among the fecal coliform-negative isolates and was found to correlate with indole production and pectin liquefaction. Low-temperature growth associated with specific biochemical tests can be used to differentiate several groups in the genus Klebsiella. Three main groups were discerned. Group I consists of indole-negative, pectin-nonliquefying, fecal coliform-positive isolates that do not grow at 10 degrees C. Group II isolates are differentiated from group I by a fecal-coliform-negative response and growth at 10 degrees C. Group III are indole-positive, pectin-liquefying, fecal coliform-negative isolates that grow at 10 degrees C. In our culture collection, isolates of group I are most frequently of human/animal clinical origins, whereas isolates of groups II and III are predominantly derived from the environment.     

Molecular phylogeny of Nyctaginaceae: taxonomy, biogeography, and characters associated with a radiation of xerophytic genera in North America

The four o'clock family (Nyctaginaceae) has a number of genera with unusual morphological and ecological characters, several of which appear to have a "tendency" to evolve repeatedly in Nyctaginaceae. Despite this, the Nyctaginaceae have attracted little attention from botanists. To produce a phylogeny for the Nyctaginaceae, we sampled 51 species representing 25 genera (of 28-31) for three chloroplast loci (ndhF, rps16, rpl16, and nrITS) and included all genera from North America. Parsimony, likelihood, and Bayesian methods were used to reconstruct the phylogeny for the family. The family is neotropical in origin. A radiation of woody taxa unites Pisonia and Pisoniella with the difficult tropical genera Neea and Guapira, which also form a clade, though neither appears to be monophyletic. This group is sister to a clade containing Bougainvillea, Belemia, and Phaeoptilum. A dramatic radiation of genera occurred in the deserts of North America. The tribe Nyctagineae and its subtribes are paraphyletic, due to over-reliance on a few homoplasious characters, i.e., pollen morphology and involucre presence. Two notable characters associated with the desert radiation are cleistogamy and edaphic endemism on gypsum soils. We discuss evolutionary trends in these traits in light of available data about self-incompatibility and gypsum tolerance in Nyctaginaceae.     

Notes on calycophyllous Rubiaceae. Part I. Morphological comparisons of the genera Chimarrhis,Bathysa, and Calycophyllum,with new combinations and a new species,Chimarrhis gentryana

A comparison of some genera of the Condaminecae (Rubiaceae) with a few taxa of closely related tribes (Rondeletieae, Calycophylleae, and Cinchoneae) revealed that some species ofChimarrhis (Condamineeae s. 1.),Bathysa (Rondeletieae), andCalycophyllum (Calycophylleae) are often misassigned to genera. The taxonomic significance of calycophylls is discussed; the generic boundaries ofChimarrhis, Bathysa, andCalycophyllum are reevaluated; and their similarities and differences are discussed. As a result, a new calycophyllous species ofChimarrhis from the Amazon,C. gentryana, is described, two of its species are transferred toBathysa (B. Bathysoides, B. perijaënsis), and one species ofBathysa (B. difformis) is reduced to synonymy underChimarrhis (C. turbinata).     

Changes in body composition associated with smoltification and premature transfer to seawater in Coho salmon (Oncorhynchus kisutch) and King salmon (O. tschawytscha)

Serum protein, glucose and fat levels were determined for Coho salmon parrs, freshwater smolts, seawater smolts, seawater stunts and freshwater desmolts. Liver and muscle glycogen, fat, protein and water concentrations were also calculated. Serum protein, glucose and fat levels were significantly lower in the freshwater smolts than in the parrs. Furthermore, both liver and muscle total fat levels were markedly decreased in the smolts, suggesting that smoltification is associated with increased catabolism. Smolts that failed to reach seawater by late summer reverted to a parr-like appearance and also regained the biochemical characteristics of parrs (high body fat and glycogen). Premature transfer of Coho presmolts into seawater caused impaired growth (stunting). Stunted Coho had higher muscle protein levels than normal smolts and parrs. Tissue water levels were not significantly different between stunts and normal seawater smolts, suggesting that the stunting phenomenon may not be caused primarily by osmoregulatory failure but may be due to shifts in metabolic patterns. In contrast to the pronounced changes seen in Coho salmon, transfer of King salmon to sea water did not result in increased catabolism of body reserves or in the production of stunts.     

Formation of the acrosome and basal body during spermiogenesis in a marine snail,Nerita picea (Mollusca: Archaeogastropoda)

In Nerita picea the proacrosomal granule is formed basally in the early spermatid from one large cisterna of the Golgi body, with which the other Golgi-derived vesicles fuse. After the proacrosomal granule has attached to the plasma membrane and invaginated to form a cup shape, one cisterna of endoplasmic reticulum inserts into the open end and deposits a granular secretion on the inner surface. Subsequently, the proacrosome migrates along the plasma membrane to the apex of the nucleus, but the Golgi body remains basal, as occurs in other archaeogastropods and also many polychaete annelids. However, the final shape and structure of the acrosome is similar to that of mesogastropods. The annulus attaches the distal centriole to the plasma membrane early in spermiogenesis. The production of the flagellum by the distal centriole not only expands the plasma membrane posteriorly but moves the centriolar complex to the nucleus, causing an invagination of the plasma membrane where it is bound by the annulus. During proacrosome migration, the Golgi body secretes a dense tube around the flagellum, and the mitochondria fuse into two spheres at the base of the nucleus. The nuclear plug that closes off the intranuclear canal until this stage rapidly reorganizes itself into two tubes of material inside the canal. The centrioles continue flagellar production, break away from the annulus, and move deep into the intranuclear canal where they fuse together to form the basal body of the sperm. In the maturing spermatid, the two mitochondria fuse into a single sheath that spirals around the flagellum. The annulus does not migrate posteriorly but remains anterior to the midpiece, which is unusual for a filiform sperm. Spermiogenesis in Nerita picea has features in common with both archaeogastropods and mesogastropods but also has some unique features. These observations lend credence to the idea that the Neritidae are a transitional group between Archaeogastropoda and Mesogastropoda.     

Leptin treatment during the neonatal period is associated with higher food intake and adult body weight in rats.

For this study, we have determined the effects of neonatal leptin treatment on the evolution of body weight. Experiment 1: pups were divided into two groups: LepF - injected with leptin (8 micro g/100 g of body weight) for the first 10 days of lactation and control (C) - receiving saline. Experiment 2: pups were divided into two groups: LepL - injected with the same leptin concentration of experiment one for the last 10 days of lactation, and C, which received saline. Body weight and food intake were monitored until age 150 days, after which leptin concentrations were measured by ELISA. The LepF group had a significant increase in body weight (p < 0.05) from day 98 onward, in food intake (p < 0.05) from day 74 onward, and higher serum leptin concentration compared to the control (108 %, p < 0.05). The LepL group had a significant increase in body weight (p < 0.05) from day 113 onward, in food intake from day 121 onward (p < 0.001), and higher serum leptin concentration compared to controls (6.9 %, p < 0.05). These results suggest that both periods of lactation constituted a critical window for body weight and food intake programming, but the effects are more marked when the leptin is injected within the first ten days.     

Variables associated with peripartum traits in dairy cows. I. Effect of dietary forages and disorders on voluntary intake of feed, body weight and milk yield

Daily voluntary intakes of feed by each of 89 Holstein cows were compared between day 220 of gestation and day 30 postpartum over a 21-month period. Diets designed to meet NRC requirements and which contained either chopped hay (29 cows), hay crop silage (HCS; 30 cows) or corn silage (CS; 30 cows) were compared prepartum (27 to 0 days), peripartum (1 day before to 3 days after calving) and postpartum (days 4 to 30 postpartum). Mixed rations, fed during lactation, were 60% forage and 40% concentrate dry matter (DM). Cow management was similar to commercial operations. The experimental hypothesis was that pre-disposition for partum and postpartum disorders (abnormal) could be related either to voluntary intake of different diets or to physical traits. Intakes (DM or estimated net energy) across diets decreased 30% between days 7 and 1 prepartum and averaged 18% and 20% lower peripartum and postpartum, respectively, in abnormal cows than in control cows. Seasonal effects on intakes were significant. In general, changes in body weight and condition and differences in udder edema and milk yield reflected intakes. The results support the original hypothesis.     

Identification and characterization of the gene cluster involved in chitin degradation in a marine bacterium, Alteromonas sp. strain O-7.

Alteromonas sp. strain O-7 secretes chitinase A (ChiA), chitinase B (ChiB), and chitinase C (ChiC) in the presence of chitin. A gene cluster involved in the chitinolytic system of the strain was cloned and sequenced upstream of and including the chiA gene. The gene cluster consisted of three different open reading frames organized in the order chiD, cbp1, and chiA. The chiD, cbp1, and chiA genes were closely linked and transcribed in the same direction. Sequence analysis indicated that Cbp1 (475 amino acids) was a chitin-binding protein composed of two discrete functional regions. ChiD (1,037 amino acids) showed sequence similarity to bacterial chitinases classified into family 18 of glycosyl hydrolases. The cbp1 and chiD genes were expressed in Escherichia coli, and the recombinant proteins were purified to homogeneity. The highest binding activities of Cbp1 and ChiD were observed when alpha-chitin was used as a substrate. Cbp1 and ChiD possessed a chitin-binding domain (ChtBD) belonging to ChtBD type 3. ChiD rapidly hydrolyzed chitin oligosaccharides in sizes from trimers to hexamers, but not chitin. However, after prolonged incubation with large amounts of ChiD, the enzyme produced a small amount of (GlcNAc)(2) from chitin. The optimum temperature and pH of ChiD were 50 degrees C and 7.0, respectively.