Productivity and species composition of algal mat communities exposed to a fluctuating thermal regime

Algal mat communities growing in thermal effluents of production nuclear reactors at the Savannah River Plant, near Aiken, SC, are exposed to large temperature fluctuations resulting from reactor operations. Rates of primary production and species composition were monitored at 4 sites along a thermal gradient in a trough microcosm to determine how these large temperature fluctuations affected productivity and algal community structure. Blue-green algae (cyanobacteria) were the only phototrophic primary producers growing in water above 45°C. These thermophiles were able to survive and apparently adapt to ambient temperatures when the reactor was shut down. The algal mat communities exposed to <45°C were composed of blue-green and eukaryotic algae that adapted rapidly to ambient temperatures. An increase in the percentage extracellular release (PER) of¹⁴C-labeled dissolved organic compounds and a decrease in primary production were observed during periods of thermal fluctuation. The results show that the dominant phototrophs in this artificially heated aquatic habitat have been selected for their ability to survive large temperature fluctuations and are similar to those of natural hot springs.This paper was prepared in connection with work under Contract No. DE-AC09-76SR00001 with the U.S. Department of Energy.     

Transient expression of adheron molecules during chick retinal development

Neuritogenesis and synapse formation are transient phenomena mediated in part by filopodial attachments (Tsui, Lankford, and Klein, Proc. Natl. Acad. Sci. 82:8256–8260 1985). These attachments can be labeled by antisera against adherons, adhesive microparticles isolated from cell culture media (Tsui, Schubert, and Klein, J. Cell Biol. 106:2095–2108 1988). Here, two monoclonal antibodies raised against adherons have been found to recognize transiently expressed membrane antigens of developing avian retina. Early in development, monoclonal antibody (mAb) AD1 stained antigens that spanned the entire tissue. With time, immunoreactivity became restricted to optic fiber, ganglion cell, and inner plexiform layers. Immunoblots of embryonic day (E) 13 retina showed a broad band at 66–72 kD for particulate fractions and a fine band at 70 kD for suluble fractions. The particulate forms disappeared as retinas matured, but the soluble form did not. mAb AD2 initially labeled retina antigens of optic fiber, ganglion cell, and inner plexiform layers (IPL). Labeling in the plexiform layer showed discrete lamina. Immunoreactivity first appeared at E9, peaked at E15, and then disappeared shortly after hatching. In isolated cells, AD2 labeled small cell surface aggregates. Cytoarchitectural studies, using whole mount transmission electron microscopy, showed AD2 antigen in cell surface microfilaments, including some that joined filopodia together. The adheron antigens recognized by mAbs AD1 and AD2 thus were (1) topographically restricted; (2) associated with cell surfaces; and (3) developmentally down-regulated. This pattern suggests a role in developmentally transient cell surface phenomena, such as neurite extension or junction biogenesis. © 1992 John Wiley & Sons, Inc.     

The effect of cytochalasin B on the rate of growth and ultrastructure of wheat coleoptiles and maize roots

Cytochalasin B (CB) inhibits the elongation growth of maize roots, and that of wheat coleoptile segments incubated in indolyl-3-acetic acid, by over 30% after a lag period of about 60 min. This long lag is not due to poor tissue penetration by the inhibitor, but seems to reflect a property of the process inhibited by CB. The only visible ultrastructural change accompanying growth inhibition is the accumulation of secretory vesicles in the vicinity of dictyosomes, which occurs between 90 and 300 min. However, a massive accumulation of vesicles is seen after 120 min in root cap cells which possess very active dictyosomes. The results indicate that CB does not inhibit elongation growth by interfering with cytoplasmic streaming. Instead, they indicate that the drug acts to inhibit the secretion of cell wall components at some stage after vesicle production, but prior to their transport.Abbreviations CB cytochalasin B - IAA indolyl-3-acetic acid - DMSO dimethyl sulphoxide     

The identification of the tRNA substrates for the supK tRNA methylase.

Purified preparations of the tRNA methylase deficient in supK strains of Salmonella typhimurium transfer methyl groups from S-adenosylmethionine (SAM) to at least two tRNA species, an alanine tRNA and a serine tRNA. The identity of the tRNA substrates for this enzyme was determined by a change in the elution position of the methyl-labeled tRNA from BND-cellulose columns before and after aminoacylation with a specific amino acid followed by derivatization of the free primary amino group with phenoxy- or naphthoxyacetate. The radioactive methyl group enzymatically added to these tRNAs is both acid and base labile and can be hydrolyzed to a volatile product at pHs above 7.5 and also at pH 1. The methylated 3'-nucleotide isolated from digested tRNA is a pyrimidine derivative and chromatographs like a modified uridylic acid. Its identity has not been established, but it is likely that it corresponds to the methyl ester of V, uridin-5-oxyacetic acid.     

Genomic and structural analysis of Syn9, a cyanophage infecting marine Prochlorococcus and Synechococcus

Cyanobacteriophage Syn9 is a large, contractile-tailed bacteriophage infecting the widespread, numerically dominant marine cyanobacteria of the genera Prochlorococcus and Synechococcus . Its 177 300 bp genome sequence encodes 226 putative proteins and six tRNAs. Experimental and computational analyses identified genes likely involved in virion formation, nucleotide synthesis, and DNA replication and repair. Syn9 shows significant mosaicism when compared with related cyanophages S-PM2, P-SSM2 and P-SSM4, although shared genes show strong purifying selection and evidence for large population sizes relative to other phages. Related to coliphage T4 – which shares 19% of Syn9's genes – Syn9 shows evidence for different patterns of DNA replication and uses homologous proteins to assemble capsids with a different overall structure that shares topology with phage SPO1 and herpes virus. Noteworthy bacteria-related sequences in the Syn9 genome potentially encode subunits of the photosynthetic reaction centre, electron transport proteins, three pentose pathway enzymes and two tryptophan halogenases. These genes suggest that Syn9 is well adapted to the physiology of its photosynthetic hosts and may affect the evolution of these sequences within marine cyanobacteria.     

The effects of acute oral glutamine supplementation on exercise-induced gastrointestinal permeability and heat shock protein expression in peripheral blood mononuclear cells

Chronic glutamine supplementation reduces exercise-induced intestinal permeability and inhibits the NF-κB pro-inflammatory pathway in human peripheral blood mononuclear cells. These effects were correlated with activation of HSP70. The purpose of this paper is to test if an acute dose of oral glutamine prior to exercise reduces intestinal permeability along with activation of the heat shock response leading to inhibition of pro-inflammatory markers. Physically active subjects (N = 7) completed baseline and exercise intestinal permeability tests, determined by the percent ratio of urinary lactulose (5 g) to rhamnose (2 g). Exercise included two 60-min treadmill runs at 70 % of VO₂max at 30 °C after ingestion of glutamine (Gln) or placebo (Pla). Plasma levels of endotoxin and TNF-α, along with peripheral blood mononuclear cell (PBMC) protein expression of HSP70 and IκBα, were measured pre- and post-exercise and 2 and 4 h post-exercise. Permeability increased in the Pla trial compared to that at rest (0.06 ± 0.01 vs. 0.02 ± 0.018) and did not increase in the Gln trial. Plasma endotoxin was lower at the 4-h time point in the Gln vs. 4 h in the Pla (6.715 ± 0.046 pg/ml vs. 7.952 ± 1.11 pg/ml). TNF-α was lower 4 h post-exercise in the Gln vs. Pla (1.64 ± 0.09 pg/ml vs. 1.87 ± 0.12 pg/ml). PBMC expression of IkBα was higher 4 h post-exercise in the Gln vs. 4 h in the Pla (1.29 ± 0.43 vs. 0.8892 ± 0.040). HSP70 was higher pre-exercise and 2 h post-exercise in the Gln vs. Pla (1.35 ± 0.21 vs. 1.000 ± 0.000 and 1.65 ± 0.21 vs. 1.27 ± 0.40). Acute oral glutamine supplementation prevents an exercise-induced rise in intestinal permeability and suppresses NF-κB activation in peripheral blood mononuclear cells.     

Characterization of microbial community structure during continuous anaerobic digestion of straw and cow manure

Responses of bacterial and archaeal communities to the addition of straw during anaerobic digestion of manure at different temperatures (37°C, 44°C and 52°C) were investigated using five laboratory-scale semi-continuous stirred tank reactors. The results revealed that including straw as co-substrate decreased the species richness for bacteria, whereas increasing the operating temperature decreased the species richness for both archaea and bacteria, and also the evenness of the bacteria. Taxonomic classifications of the archaeal community showed that Methanobrevibacter dominated in the manure samples, while Methanosarcina dominated in all digesters regardless of substrate. Increase of the operating temperature to 52°C led to increased relative abundance of Methanoculleus and Methanobacterium. Among the bacteria, the phyla Firmicutes and Bacteroidetes dominated within all samples. Compared with manure itself, digestion of manure resulted in a higher abundance of an uncultured class WWE1 and lower abundance of Bacilli. Adding straw to the digesters increased the level of Bacteroidia, while increasing the operating temperature decreased the level of this class and instead increased the relative abundance of an uncultured genus affiliated to order MBA08 (Clostridia). A considerable fraction of bacterial sequences could not be allocated to genus level, indicating that novel phylotypes are resident in these communities.     

Mycobacteriophage Marvin: a new singleton phage with an unusual genome organization

Mycobacteriophages represent a genetically diverse group of viruses that infect mycobacterial hosts. Although more than 80 genomes have been sequenced, these still poorly represent the likely diversity of the broader population of phages that can infect the host, Mycobacterium smegmatis mc(2)155. We describe here a newly discovered phage, Marvin, which is a singleton phage, having no previously identified close relatives. The 65,100-bp genome contains 107 predicted protein-coding genes arranged in a noncanonical genomic architecture in which a subset of the minor tail protein genes are displaced about 20 kbp from their typical location, situated among nonstructural genes anticipated to be expressed early in lytic growth. Marvin is not temperate, and stable lysogens cannot be recovered from infections, although the presence of a putative xis gene suggests that Marvin could be a relatively recent derivative of a temperate parent. The Marvin genome is replete with novel genes not present in other mycobacteriophage genomes, and although most are of unknown function, the presence of amidoligase and glutamine amidotransferase genes suggests intriguing possibilities for the interactions of Marvin with its mycobacterial hosts.