Surface-Matrix Screening Identifies Semi-specific Interactions that Improve Potency of a Near Pan-reactive HIV-1-Neutralizing Antibody

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Recovery of freshwater marsh vegetation after a saltwater intrusion event

Greenhouse mesocosms of freshwater marsh vegetation were exposed to a simulated saltwater intrusion event followed by a recovery period during which water levels and interstitial water salinity were adjusted over a range of conditions. Virtually all above-ground vegetation, including the three dominant species, Sagittaria lancifolia L., Leersia oryzoides (L.) Swartz, and Panicum hemitomon Schultes, was killed by the initial saltwater intrusion event. P. hemitomon did not recover, but S. lancifolia and L. oryzoides, as well as many of the other species initially present, exhibited some ability to recover depending on post-saltwater intrusion conditions. Increasingly harsh recovery conditions (for freshwater marsh vegetation), including more reduced soil conditions, higher interstitial salinities, and higher interstitial sulfide concentrations were associated with decreased live above-ground biomass and species richness. The effect of elevated salinity on vegetative recovery became more pronounced under flooded conditions. This experiment illustrates that the response of a freshwater marsh community to the long-term disturbance effect of a transient saltwater intrusion event will be strongly influenced by post-intrusion salinity and water levels.     

Craniodental remains ofPapio angusticeps from the haasgat cave site,South Africa

Haasgat is a fossil-bearing cave site that has yielded 83 craniodental fossils of early Papio.All of the Haasgat cave baboon fossil collection may be identified as Papio angusticeps.The Haasgat fossils of P. angusticepsextend the previously known size range of the species as identified at other sites. The concordance of this and other fauna with that of Kromdraai suggest that Haasgat probably dates to the terminal Pliocene. We hypothesize that the Haasgat baboons and associated fauna were accumulated by versatile predators operating in a cave in a montane forest environment with savannah or open woodland nearby.     

A General Method for Identifying Recessive Diploid-Specific Mutations in Saccharomyces Cerevisiae, Its Application to the Isolation of Mutants Blocked at Intermediate Stages of Meiotic Prophase and Characterization of a New Gene Sae2

We describe a general new approach for identifying recessive mutations that affect diploid strains of yeast Saccharomyces cerevisiae and the application of this method to the identification of mutations that confer an intermediate block in meiotic prophase chromosome metabolism. The method uses a temperature-sensitive conjugation mutation ste7-1 in combination with homothallism. The mutations of interest confer a defect in spore formation that is dependent upon a gene required for initiation of meiotic recombination and development of meiosis-specific chromosome structure (SPO11). Identified in this screen were null mutations of the DMC1 gene, nonnull mutations of RAD50 (rad50S), and mutations in three new genes designated SAE1, SAE2 and SAE3 (Sporulation in the Absence of Spo Eleven). Molecular characterization of the SAE2 gene and characterization of meiotic and mitotic phenotypes of sae2 mutants are also presented. The phenotypes conferred by a sae2 null mutation are virtually indistinguishable from those conferred by the previously identified nonnull mutations of RAD50 (rad50S). Most notably, both mutations confer only weak sensitivity to the radiomimetic agent methyl methane sulfonate (MMS) but completely block resection and turnover of meiosis-specific double-strand breaks. These observations provide further evidence that this constellation of phenotypes identifies a specific molecular function.     

Mutations in Saccharomyces Cerevisiae That Block Meiotic Prophase Chromosome Metabolism and Confer Cell Cycle Arrest at Pachytene Identify Two New Meiosis-Specific Genes Sae1 and Sae3

Two new meiosis-specific genes, SAE1 and SAE3, have been identified in a screen for mutations that confer an intermediate block in meiotic prophase. Such mutations confer a block to spore formation that is circumvented by addition of a mutation that eliminates meiotic recombination initiation and other aspects of chromosome metabolism, i.e., spo11. We show that sae1-1 and sae3-1 mutations each confer a distinct defect in meiotic recombination. sae1-1 produces recombinants but very slowly and ultimately to less than half the wild-type level; sae3-1 makes persistent hyper-resected meiotic double-strand breaks and has a severe defect in formation of recombinants. Both mutants arrest at the pachytene stage of meiotic prophase, sae1-1 temporarily and sae3-1 permanently. The phenotypes conferred by sae3-1 are similar to those conferred by mutation of the yeast RecA homologue DMC1, suggesting that SAE3 and DMC1 act at the same step(s) of chromosome metabolism. These results provide further evidence that intermediate blocks to prophase chromosome metabolism cause cell-cycle arrest. SAE1 encodes a 208-residue protein homologous to vertebrate mRNA cap-binding protein 20. SAE3 corresponds to a meiosis-specific RNA encoding an unusually short open reading frame of 50 codons.     

Cloning and Characterization of Two Human G Protein-Coupled Receptor Genes (GPR38 and GPR39) Related to the Growth Hormone Secretagogue and Neurotensin Receptors

The recent cloning of a growth hormone secretagogue receptor (GHS-R) from human pituitary gland and brain identified a third G protein-coupled receptor (GPC-R) involved in the control of growth hormone release. The nucleotide sequence of the GHS-R is most closely related to the neurotensin receptor-1 (NT-R1) (35% overall protein identity). Two human GPC-Rs related to both the type 1a GHS-R and NT-Rs were cloned and characterized. Hybridization at low posthybridizational stringency with restriction enzyme-digested human genomic DNA resulted in the identification of a genomic clone encoding a first GHS-R/NT-R family member (GPR38). A cDNA clone was identified encoding a second GHS-R-related gene (GPR39). GPR38 and GPR39 share significant amino acid sequence identity with the GHS-R and NT-Rs 1 and 2. An acidic residue (E124) in TM-3, essential for the binding and activation of the GHS-R by structurally dissimilar GHSs, was conserved in GPR38 and GPR39. GPR38 is encoded by a single gene expressed in thyroid gland, stomach, and bone marrow. GPR39 is encoded by a highly conserved single-copy gene, expressed in brain and other peripheral tissues. Fluorescencein situhybridization localized the genes for GPR38 and GPR39 to separate chromosomes, distinct from the gene encoding the GHS-R and NT-R type 1. The ligand-binding and functional properties of GPR38 and GPR39 remain to be determined.     

Life on the edge: reproductive mode and rate of invasive <Emphasis Type="Italic">Phragmites australis</Emphasis> patch expansion

The dynamics of plant invasions from initial colonization through patch expansion are driven in part by mode of reproduction, i.e., sexual (seed) and asexual (clonal fragments and expansion) means. Expansion of existing patches—both rate and mode of spread into a matrix of varying conditions—is important for predicting potential invader impacts. In this study, we used fine-scale genetic assessments and remote sensing to describe both the rate and mode of expansion for 20 Phragmites australis patches in flooded and unflooded wetland units on the Great Salt Lake, UT. We found that the majority of Phragmites patch expansion occurred via clonal spread but we also documented instances of (potentially episodic) seedling recruitment. The mode of patch expansion, inferred from patch edge genet richness, was unrelated to flooding in the wetland unit in the preceding growing season. The rate of Phragmites patch expansion varied from 0.09 to 0.35 year^?1 and was unrelated to the mode of spread. In six patches monitored across two years, monoclonal patches stayed monoclonal, whereas patches with higher genet richness had a marked increase in diversity in the second year. The findings of the present study suggest how this partially clonal species can exploit the benefits of both sexual (i.e., genetic recombination, widespread dispersal, colonization of new areas) and asexual reproduction (i.e., stability of established clones suited to local environmental conditions) to become one of the most successful wetland plant invaders. To control this species, both forms of reproduction need to be fully addressed through targeted management actions.     

Numerical taxonomy of some non-saccharolytic and saccharolytic Bacteroides species

Various Bacteroides spp. were examined by physiological tests, presence of specific enzymes, antibiotic sensitivity, menaquinone composition and a few miscellaneous tests. The data matrix containing 58 strains and 55 unit characters was examined using Gower's similarity coefficients (S _G ) and included matching negative character states and multistate characters. The highly saccharolytic strains were separated from the less saccharolytic and non-fermentative strains at the 55% similarity level; while at the slightly higher level of 63% strains of Capnocytophaga (formerly Bact. ochraceus ) were recovered as a compact phenon distinct from other saccharolytic species. The phenogram was divided into 6 clusters at 72% similarity level. Most of the ' Bact. fragilis group' of species clustered in one phenon while Bact. melaninogenicus ssp. melaninogenicus, Bact. bivius and a new species, Bact. denticola , formed another group. Another phenon comprised the saccharolytic non-pigmented species closely related to Bact. oralis such as Bact. buccalis and Bact. pentosaceus. The less saccharolytic strains of Bact. melaninogenicus ssp. intermedius and Bact. disiens were recovered in a distinct phenon. The low affinity (less than 55% similarity) between the two subspecies of Bact. melaninogenicus emphasised the need for reclassifying these taxa into separate species. The non-fermentative and very weakly saccharolytic strains formed good taxospecies. The separation of this cluster into three subclusters is in excellent agreement with chemotaxonomic data now available.