The Effect of Culture Media on Antigenic Expression in Sulfate-Reducing Bacteria

The importance of sulfate-reducing bacteria (SRB) in nature has been widely recognized for many years. However, little is known about the ecology of SRB. The problem has been detecting, classifying, and quantifying these organisms. There are many shortcomings in the use of culture media for this purpose. As an alternative, fluorescent antibody (FA) techniques were considered as a method for the detection and identification of SRB. Antisera were prepared against whole cells of different species of SRB and evaluated for detection and identification of these organisms. Surface antigens of SRB were species specific. In addition, culture conditions influenced the expression of surface antigens, causing the antisera to be extremely specific. These results were confirmed by the sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE) profiles of membrane proteins. On the basis of this specificity, the application of FA produced against culture collection strains would have limited application for detecting, identifying, and enumerating these organisms in nature.     

Asynchronous expression of the homeodomain protein CUX1 in Sertoli cells and spermatids during spermatogenesis in mice

The homeodomain CUX1 protein exists as multiple isoforms that arise from proteolytic processing of a 200-kDa protein or an alternate splicing or from the use of an alternate promoter. The 200-kDa CUX1 protein is highly expressed in the developing kidney, where it functions to regulate cell proliferation. Transgenic mice ectopically expressing the 200-kDa CUX1 protein develop renal hyperplasia associated with reduced expression of the cyclin kinase inhibitor p27. A 55-kDa CUX1 isoform is expressed exclusively in the testes. We determined the pattern and timing of CUX1 protein expression in developing testes. CUX1 expression was continuous in Sertoli cells from prepubertal testes but became cyclic when spermatids appeared. In testes from mature mice, CUX1 was highly expressed only in round spermatids at stages IV-V of spermatogenesis, in both spermatids and Sertoli cells at stages VI-X of spermatogenesis, and only in Sertoli cells at stage XI of spermatogenesis. While most of the seminiferous tubules in wild-type mice were between stages VI and X of spermatogenesis, there was a significant reduction in the percentage of seminiferous tubules between stages VI and X in Cux1 transgenic mice and a significant increase in the percentage of seminiferous tubules in stages IV-V and XI. Moreover, CUX1 was not expressed in proliferating cells in testes from either wild-type or transgenic mice. Thus, unlike the somatic form of CUX1, which has a role in cell proliferation, the testis-specific form of CUX1 is not involved in cell division and appears to play a role in signaling between Sertoli cells and spermatids.     

Spatial and temporal variation in phytoplankton community structure in a southeastern U.S. reservoir determined by HPLC and light microscopy

Spatial and temporal variation in phytoplankton community structure within a large flood-control reservoir (Sardis Reservoir, MS, USA) was investigated in relation to variation in physicochemical properties, location within the reservoir, hydraulic residence time (HRT), nutrient concentrations, temperature, and light conditions over a 14-month period. During periods of short HRT, phytoplankton communities throughout the reservoir were homogeneous in biomass, composition, and production. With a gradual increase in HRT from spring to summer, spatially heterogeneous phytoplankton communities developed along the longitudinal axis of the reservoir. During this period of longer HRT, diatoms and chlorophytes were a larger proportion of total phytoplankton biomass at shallow and more turbid locations near the head of the reservoir, whereas cyanobacteria were a larger proportion of the community at deeper and less turbid locations closer to the outflow. Seasonal succession of the phytoplankton community was represented by high abundance of diatoms in spring, increasing biomass of cyanobacteria through summer, and a secondary bloom of diatoms in fall. Species of Cyclotella, Asterionella, Nitzschia, and Ankistrodesmus were among the first colonizers in the early growing season, closely followed by Aulacoseira, whereas species of Staurastrum and Tetraedron appeared later in the spring. Species of Synedra, Crucigenia, Selenastrum, Scenedesmus, and Merismopedia occurred throughout the sampling period. As the diatoms started to decrease during mid-spring, cryptophytes increased, prior to dominance of species of Pseudanabaena in summer. Reservoir management of HRT, in combination with spatial variation in reservoir morphology and seasonal variation in temperature and riverine nutrient inputs, creates seasonally variable yet distinct spatial patterns in phytoplankton community biomass, composition, and production. Handling editor: L. Naselli-Flores     

High-density mapping of a resistance gene to Ug99 from the Iranian landrace PI 626573

Managing wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is imperative for the preservation of global food security. The most effective strategy is pyramiding several resistance genes into adapted wheat cultivars. A search for new resistance sources to Pgt race TTKSK resistance identified a spring wheat landrace, accession PI 626573, as a potentially novel source of resistance. A cross was made between LMPG-6, a susceptible spring wheat line, and PI 626573 and used to develop a recombinant inbred population to map the resistance. Bulk segregant analysis (BSA) of LMPG-6/PI 626573 F₂ progeny determined resistance was conferred by a single dominant gene given the provisional designation SrWLR. The BSA identified nine microsatellite (SSR) markers on the long arm of chromosome 2B associated with the resistant phenotype. Fifteen polymorphic SSRs, including the nine identified in the BSA, were used to produce a linkage map of chromosome 2B, positioning SrWLR in an 8.8 cM region between the SSRs GWM47 and WMC332. This region has been reported to contain the wheat stem rust resistance genes Sr9 and SrWeb, the latter conferring resistance to Pgt race TTKSK. The 9,000 marker Illumina Infinium iSelect SNP assay was used to further saturate the SrWLR region. The cosegregating SNP markers IWA6121, IWA6122, IWA7620, IWA8295, and IWA8362 further delimited the SrWLR region distally to a 1.9 cM region. The present study demonstrates the iSelect assay to be an efficient tool to delimit the region of a mapping population and establish syntenic relationships between closely related species.     

Neocarzinostatin naphthoate synthase: an unique iterative type I PKS from neocarzinostatin producer Streptomyces carzinostaticus

Enediyne antibiotics are known for their potent antitumor activities. One such enediyne, neocarzinostatin (NCS), consists of a 1:1 complex of non-peptide chromophore (1a), and peptide apoprotein. The structurally diverse non-peptide chromophore is responsible for its biological activity. One of its structural components, the naphthoic acid moiety (2,7-dihydroxy-5-methyl-1-naphthoic acid, 1d) is synthesized by a polyketide synthase (PKS) pathway through condensing six intact acetate units. The 5.45 kb iterative type I PKS, neocarzinostatin naphthoate synthase (NNS), responsible for naphthoic acid moiety biosynthesis, shares sequence homology with 6-methyl salicylic acid synthase of fungi and orsellinic acid synthases (AviM and CalO5) of Streptomyces origin. Cultures of S. lividans TK24 and S. coelicolor YU105 containing plasmids with NNS were able to produce 2-hydroxy-5-methyl-1-naphthoic acid (2a), a key intermediate of naphthoic acid moiety in NCS. In addition to 2a, a novel product, 2-hydroxy-5-hydroxymethyl-1-naphthoic acid (2d) was isolated. This is the first report of a bacterial iterative type I PKS from an enediyne producer which enables the biosynthesis of bicyclic aromatic compounds.     

Angucyclines Sch 47554 and Sch 47555 from Streptomyces sp. SCC-2136: cloning, sequencing, and characterization

The entire gene cluster involved in the biosynthesis of angucyclines Sch 47554 and Sch 47555 was cloned, sequenced, and characterized. Analysis of the nucleotide sequence of genomic DNA spanning 77.5-kb revealed a total of 55 open reading frames, and the deduced products exhibited strong sequence similarities to type II polyketide synthases, deoxysugar biosynthetic enzymes, and a variety of accessory enzymes. The involvement of this gene cluster in the pathway of Sch 47554 and Sch 47555 was confirmed by genetic inactivation of the aromatase, including a portion of the ketoreductase, which was disrupted by inserting the thiostrepton gene.