The insect endosymbiont Sodalis glossinidius utilizes a type III secretion system for cell invasion

Sodalis glossinidius is a maternally transmitted secondary endosymbiont residing intracellularly in tissues of the tsetse flies, Glossina spp. In this study, we have used Tn5 mutagenesis and a negative selection procedure to derive a S. glossinidius mutant that is incapable of invading insect cells in vitro and is aposymbiotic when microinjected into tsetse. This mutant strain harbors Tn5 integrated into a chromosomal gene sharing high sequence identity with a type III secretion system invasion gene (invC) previously identified in Salmonella enterica. With the use of degenerate PCR, we have amplified a further six Sodalis inv/spa genes sharing high sequence identity with type III secretion system genes encoded by Salmonella pathogenicity island 1. Phylogenetic reconstructions based on the inv/spa genes of Sodalis and other members of the family Enterobacteriaceae have consistently identified a well-supported clade containing Sodalis and the enteric pathogens Shigella and Salmonella. These results suggest that Sodalis may have evolved from an ancestor with a parasitic intracellular lifestyle, possibly a latter-day entomopathogen. These observations lend credence to a hypothesis suggesting that vertically transmitted mutualistic endosymbionts evolve from horizontally transmitted parasites through a parasitism–mutualism continuum.

Biochemical evolution III: Polymerization on organophilic silica-rich surfaces, crystal–chemical modeling, formation of first cells, and geological clues

Catalysis at organophilic silica-rich surfaces of zeolites and feldspars might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and other geological sources. Crystal–chemical modeling yielded packings for amino acids neatly encapsulated in 10-ring channels of the molecular sieve silicalite-ZSM-5-(mutinaite). Calculation of binding and activation energies for catalytic assembly into polymers is progressing for a chemical composition with one catalytic Al–OH site per 25 neutral Si tetrahedral sites. Internal channel intersections and external terminations provide special stereochemical features suitable for complex organic species. Polymer migration along nano/micrometer channels of ancient weathered feldspars, plus exploitation of phosphorus and various transition metals in entrapped apatite and other microminerals, might have generated complexes of replicating catalytic biomolecules, leading to primitive cellular organisms. The first cell wall might have been an internal mineral surface, from which the cell developed a protective biological cap emerging into a nutrient-rich “soup.” Ultimately, the biological cap might have expanded into a complete cell wall, allowing mobility and colonization of energy-rich challenging environments. Electron microscopy of honeycomb channels inside weathered feldspars of the Shap granite (northwest England) has revealed modern bacteria, perhaps indicative of Archean ones. All known early rocks were metamorphosed too highly during geologic time to permit simple survival of large-pore zeolites, honeycombed feldspar, and encapsulated species. Possible microscopic clues to the proposed mineral adsorbents/catalysts are discussed for planning of systematic study of black cherts from weakly metamorphosed Archaean sediments.

The phosphatase activity of carbonic anhydrase III is reversibly regulated by glutathiolation.

Carbonic anhydrase isozyme III (CAIII) is unique among the carbonic anhydrases because it demonstrates phosphatase activity. CAIII forms a disulfide link between glutathione and two of its five cysteine residues, a process termed S-glutathiolation. Glutathiolation of CAIII occurs in vivo and is increased during aging and under acute oxidative stress. We show that glutathiolation serves to reversibly regulate the phosphatase activity of CAIII. Glutathiolation of Cys-186 is required for phosphatase activity, while glutathiolation of Cys-181 blocks activity. Phosphotyrosine is the preferred substrate, although phosphoserine and phosphothreonine can also be cleaved. Thus, glutathiolation is a reversible covalent modification that can regulate CAIII, a phosphatase that may function in the cellular response to oxidative stress.

The SNAP45 subunit of the small nuclear RNA (snRNA) activating protein complex is required for RNA polymerase II and III snRNA gene transcription and interacts with the TATA box binding protein.

The RNA polymerase II and III small nuclear RNA (snRNA) promoters contain a common basal promoter element, the proximal sequence element (PSE). The PSE binds a multisubunit complex we refer to as the snRNA activating protein complex (SNAPc). At least four polypeptides are visible in purified SNAPc preparations, which migrate with apparent molecular masses of 43, 45, 50, and 190 kDa on SDS/polyacrylamide gels. In addition, purified preparations of SNAPc contain variable amounts of TATA box binding protein (TBP). An important question is whether the PSEs of RNA polymerase II and III snRNA promoters recruit the exact same SNAP complex or slightly different versions of SNAPc, differing, for example, by the presence or absence of a subunit. To address this question, we are isolating cDNAs encoding different subunits of SNAPc. We have previously isolated the cDNA encoding the 43-kDa subunit SNAP43. We now report the isolation of the cDNA that encodes the p45 polypeptide. Antibodies directed against p45 retard the mobility of the SNAPc-PSE complex in an electrophoretic mobility shift assay, indicating that p45 is indeed part of SNAPc. We therefore refer to this protein as SNAP45. SNAP45 is exceptionally proline-rich, interacts strongly with TBP, and, like SNAP43, is required for both RNA polymerase II and III transcription of snRNA genes.

Identification of a virulence locus encoding a second type III secretion system in Salmonella typhimurium.

Mapping the insertion points of 16 signature-tagged transposon mutants on the Salmonella typhimurium chromosome led to the identification of a 40-kb virulence gene cluster at minute 30.7. This locus is conserved among all other Salmonella species examined but is not present in a variety of other pathogenic bacteria or in Escherichia coli K-12. Nucleotide sequencing of a portion of this locus revealed 11 open reading frames whose predicted proteins encode components of a type III secretion system. To distinguish between this and the type III secretion system encoded by the inv/spa invasion locus known to reside on a pathogenicity island, we refer to the inv/spa locus as Salmonella pathogenicity island (SPI) 1 and the new locus as SPI2. SPI2 has a lower G+C content than that of the remainder of the Salmonella genome and is flanked by genes whose products share greater than 90% identity with those of the E. coli ydhE and pykF genes. Thus SPI2 was probably acquired horizontally by insertion into a region corresponding to that between the ydhE and pykF genes of E. coli. Virulence studies of SPI2 mutants have shown them to be attenuated by at least five orders of magnitude compared with the wild-type strain after oral or intraperitoneal inoculation of mice.

Implementación de docencia semipresencial en Óptica Fisiológica III (Diplomatura en Óptica y Optometría)

Póster y resumen de la comunicación presentada en el VI Congreso Internacional de Docencia Universitaria e Innovación (CIDUI), Barcelona, 30 junio-2 julio 2010.

Note from William Croswell to Mrs. Crocker, [1795] July 30

Note regarding the return of Mrs. Crocker's books.

Letter from Benjamin Croswell to William Croswell, 1810 March 30

One-page letter from William Croswell's cousin with information about the ailments of Benjamin Croswell's wife.

Note from William Croswell to Levi Frisbie, 1818 November 30

Brief note with a complaint about the servant of Levi Frisbie, Harvard Professor of Natural History.

Letter from William Croswell to the Mr. Holt, [1824] September 30

Draft of a letter complaining about the noisiness of Holt's students.

III. Sermon notes, 1746-1747

This paper notebook contains abstracts of sermons attended between January 12, 1745/6 and November 15, 1747 in Kingston, Massachusetts, presumably by William Sever. The notebook lists the minister by last name, the location ("King." for Kingston), the date the sermon was delivered, the biblical passage used, and one-to-two-page entries on the sermon containing numbered notes and a section titled "Improvements and Applications." From the front of the volume, the pages contain entries for sermons attended between January 12 1745/6 through November 30, 1746, and there are no entries for June-September 1746. Sermon entries for December 7, 1746 to November 15, 1747 are written tête-bêche from the other end of the volume, and there are no entries for February-July 1747. Almost all of the sermons were delivered by Rev. William Rand, but there are sporadic sermons by additional ministers, who based on the last name are presumed to be John Angier (1701-1787; Harvard AB 1720), Ebenezer Gay (1696-1787; Harvard AB 1714), Nathaniel Eells (1678-1750; Harvard AB 1699), Josiah Torrey (1720-1783; Harvard AB 1741) and Daniel Shute (1722-1802; Harvard AB 1743).