Phylogenetic tests of the hypothesis of block duplication of homologous genes on human chromosomes 6, 9, and 1

There are 10 gene families that have members on both human chromosome 6 (6p21.3, the location of the human major histocompatibility complex [MHC]) and human chromosome 9 (mostly 9q33-34). Six of these families also have members on mouse chromosome 17 (the mouse MHC chromosome) and mouse chromosome 2. In addition, four of these families have members on human chromosome 1 (1q21-25 and 1p13), and two of these have members on mouse chromosome 1. One hypothesis to explain these patterns is that members of the 10 gene families of human chromosomes 6 and 9 were duplicated simultaneously as a result of polyploidization or duplication of a chromosome segment ("block duplication"). A subsequent block duplication has been proposed to account for the presence of representatives of four of these families on human chromosome 1. Phylogenetic analyses of the 9 gene families for which data were available decisively rejected the hypothesis of block duplication as an overall explanation of these patterns. Three to five of the genes on human chromosomes 6 and 9 probably duplicated simultaneously early in vertebrate history, prior to the divergence of jawed and jawless vertebrates, and shortly after that, all four of the genes on chromosomes 1 and 9 probably duplicated as a block. However, the other genes duplicated at different times scattered over at least 1.6 billion years. Since the occurrence of these clusters of related genes cannot be explained by block duplication, one alternative explanation is that they cluster together because of shared functional characteristics relating to expression patterns.      

Evidence for the presence of β-lactamase inStreptomyces glaucescens and its inhibition by sodium clavulanate

Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis.     

Trichopodiella faurei n. sp. (Ciliophora,Phyllopharyngea, Cyrtophoria): Morphological Description and Phylogenetic Analyses Based on SSU rRNA and Group I Intron Sequences

ABSTRACT. A new marine cyrtophorian ciliate Trichopodiella faurei n. sp., which belongs to the order Dysteriida, family Hartmannulidae, was investigated at the morphological and molecular levels. A combination of morphological features of the organism including the oval body shape, 2–3 contractile vacuoles, 22–28 nematodesmal rods in the cytopharyngeal basket, and 31–39 somatic kineties, distinguishes it from all other known congeners. In reconstructed small subunit (SSU) rRNA phylogenies, T. faurei groups with Isochona, a representative genus of the subclass Chonotrichia. The similarity of the infraciliature between hartmannulids and several chonotrichian examples also suggests that these taxa should be closely related. A new S943 intron belonging to group IC1 was identified in the SSU rRNA gene of this species. This intron is phylogenetically related to the S891 introns previously found in the suctorians Acineta sp. and Tokophrya lemnarum, and their internal guide sequences share four nucleotides, indicating that these introns were vertically inherited from a common phyllopharyngean ancestor and that reverse splicing might have been involved in the transposition.     

The Unique Chemistry of Eastern Mediterranean Water Masses Selects for Distinct Microbial Communities by Depth

The waters of the Eastern Mediterranean are characterized by unique physical and chemical properties within separate water masses occupying different depths. Distinct water masses are present throughout the oceans, which drive thermohaline circulation. These water masses may contain specific microbial assemblages. The goal of this study was to examine the effect of physical and geological phenomena on the microbial community of the Eastern Mediterranean water column. Chemical measurements were combined with phospholipid fatty acid (PLFA) analysis and high-throughput 16S rRNA sequencing to characterize the microbial community in the water column at five sites. We demonstrate that the chemistry and microbial community of the water column were stratified into three distinct water masses. The salinity and nutrient concentrations vary between these water masses. Nutrient concentrations increased with depth, and salinity was highest in the intermediate water mass. Our PLFA analysis indicated different lipid classes were abundant in each water mass, suggesting that distinct groups of microbes inhabit these water masses. 16S rRNA gene sequencing confirmed the presence of distinct microbial communities in each water mass. Taxa involved in autotrophic nitrogen cycling were enriched in the intermediate water mass suggesting that microbes in this water mass may be important to the nitrogen cycle of the Eastern Mediterranean. The Eastern Mediterranean also contains numerous active hydrocarbon seeps. We sampled above the North Alex Mud Volcano, in order to test the effect of these geological features on the microbial community in the adjacent water column. The community in the waters overlaying the mud volcano was distinct from other communities collected at similar depths and was enriched in known hydrocarbon degrading taxa. Our results demonstrate that physical phenomena such stratification as well as geological phenomena such as mud volcanoes strongly affect microbial community structure in the Eastern Mediterranean water column.     

Two Pax2/5/8-binding sites in Engrailed2 are required for proper initiation of endogenous mid-hindbrain expression

During early brain development mouse Engrailed2 (En2) is expressed in a broad band across most of the mid-hindbrain region. Evidence from gene expression data, promoter analysis in transgenic mice and mutant phenotype analysis in mice and zebrafish has suggested that Pax2, 5 and 8 play a critical role in regulating En2 mid-hindbrain expression. Previously, we identified two Pax2/5/8-binding sites in a 1.0 kb En2 enhancer fragment that is sufficient to directed reporter gene expression to the early mid-hindbrain region and showed that the two Pax2/5/8-binding sites are essential for the mid-hindbrain expression in transgenic mice. In the present study we have examined the functional requirements of these two Pax2/5/8-binding sites in the context of the endogenous En2 gene for directing mid-hindbrain expression. The two Pax2/5/8-binding sites were deleted from the En2 locus and replaced with the bacterial neo gene by homologous recombination in mouse embryonic stem cells. After transmitting the mutation into mice, the neo gene was removed by breeding with transgenic mice expressing cre from a CMV promoter. Embryos homozygous for this En2 Pax2/5/8-binding site deletion mutation had a mild reduction in En2 expression in the presumptive mid-hindbrain region at the 5-7 somite stage, when En2 expression is normally initiated. However, from embryonic day 9.0 onwards, the mutant embryos showed En2 expression indistinguishable from that seen in wild type embryos. Furthermore, the mutants did not show the cerebellar defect seen in mice with a null mutation in En2. This result demonstrates that the two Pax2/5/8-binding sites that were deleted, while being required for mid-hindbrain expression in the context of a 1.0 kb En2 enhancer, are only required for proper initiation of expression of the endogenous En2 gene. Interestingly, a comparison of the lacZ RNA and protein expression patterns directed by the 1.0 kb enhancer fragment revealed that lacZ protein was acting as a lineage marker in the mid-hindbrain region by persisting longer than the mRNA. The transgene expression directed by the 1.0 kb enhancer fragment therefore does not mimic the entire broad domain of En2 expression. Taken together, these two studies demonstrate that DNA binding sites in addition to the two Pax2/5/8-binding sites must be necessary for En2 mid-hindbrain expression.     

Temporal occurrence of third-stage larvae of Elaeophora schneideri in Tabanus lineola hinellus on South Island, South Carolina

The occurrence of third-stage larvae of the arterial worm (Elaeophora schneideri) in populations of the horse fly, Tabanus lineola hinellus, was studied on South Island, Georgetown County, South Carolina. Over the period from mid-April to mid-October 1982, horse flies had a bimodal pattern of abundance with peak populations in June and September. During individual bimonthly horse fly collections, the prevalence of infection of T. l. hinellus ranged from 0 to 1.23%. Prevalence of infected horse flies was biphasic with peaks in mid-May (1.23%) and mid-August (1.22%), 2 to 4 wk prior to peaks in horse fly populations. The intensity of infection of T. l. hinellus increased as time progressed and was highest in late summer. This increase resulted in greater recovery of infective larvae during August-September (mean intensity = 25) than in May-June (mean intensity = 4). Both prevalence and intensity of infection of T. l. hinellus were low compared to primary intermediate hosts of E. schneideri in the western U.S.     

Determination of aflatoxin levels in peanut butter using HPLC and ELISA procedures: Inter-laboratory comparison

Mycotoxin Research - Six laboratories analyzed portions of the same aqueous acetonitrile extracts of three peanut butters for aflatoxin concentrations by an HPLC procedure (using immunoaffinity...